A lot of worlds over 1g gravity. How do 1G thrust ships take off?

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Moppy
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby Moppy » Wed Feb 06, 2019 4:30 pm

@phavoc

Your physics is wrong.

"But I pasted it from NASA"

Yes but you pasted an article that doesn't describe in full how lift works. It's correct but incomplete for reasons of length.

You have many forces on a wing that provide lift. A partial list is:

(1) the pressure diferential above the wing "sucking" the aircraft up - caused by airfoil shape, and by tilting the wing upwards.

(2) Netwon's 3rd law. tilting the wing upwards meaning air being deflected downwards and creating an upward reaction.

If you admit there is air deflected downwards, you must also realise there is an upward reaction force exerted? This is how a helicopter rotor works, right? There's basically no difference between wing and rotor physics. Both are shaped, angled surfaces that are moved through air, generating an upward force by the same mechanisms. If you were to turn one wing of a plane upside down and spin the plane on a turntable, you would have a rotor blade.

In the case of a brick, (2) i think is more significant as it's a stupid shape for flying.

As for the airframe drag: If the m-drive needs more thrust in atmosphere to cancel out the increased drag, why can't it generate the same thrust in space, and therefore provide higher acceleration in vacuum? We have to pick one of "game approximatation" or "negligible drag on hull"

phavoc wrote:
Tue Feb 05, 2019 8:54 pm
Moppy wrote:
Tue Feb 05, 2019 7:47 pm
Obviously the brick is powered. Since it's sufficiently powered and tilted up at the front, it generates lift by deflecting air downwards. It will also tumble to chaotic forces and then lose lift. Maintaining the precise angle to generate lift is problem of control. I have absolutely no idea why you think the air cannot generate enough force to provide sufificient lift, as wind storms like tornados can easily lift bricks.

Drag from parachutes don't matter. The maneuver drive ignores it. It generates the same acceleration in vacuum and in atmopshere, right? Therefore there is almst zero drag on a ship powered by that engine. Although as I said, there i obviously some limit. Parachutes will flap about and cause minute attitude shifts, hence it's a control problem to maintain your angle. The reduction of drag also means less lift, which is problematic. There's still the bernoulli effect :-)

I don't claim those planes are identical to a Type-R. Just that saying the wings of a Type-R are too fat is unsupportable. None of us knows if the Type-R shape is possible under Traveller physics. Another thing to consider for Traveller ships are waveriders and ground effect.
Umm, in my example the brick was being held by a hand in a car at 50mph. And it was an unpowered brick. Most bricks, I think, would fall within that category. As I mentioned previously (original data can be found here - https://www.researchgate.net/publicatio ... fting_Body) the lift-to-drag ratio of a brick is 0 with a glide angle of 90 degrees. The glide angle for a lifting body is 16 degrees, the space shuttle is 12 degrees. A tumbling brick wouldn't have one since it's tumbling (well, technically, it would have more than one, as it would run through a whole bunch as it tumbled, but effectively it would have none).

As has been continually cited, yes, the brick CAN generate lift - but ONLY when the forward velocity is sufficient to overcome both mass and drag. And it doesn't generate lift by deflecting air downwards, lift is generated by air pressure being different above and below couple with the speed of the air. If air is moving faster above than below then no lift can be generated. The space shuttle and the X-series lifting bodies also would adjust their angle of attack. Again, going back to the boys from NASA, click on the link here - https://www.nasa.gov/centers/johnson/pd ... 26-241.pdf - refer to page 12. You will see how the shuttle angles it's nose to take advantage of drag during the deorbiting. The X-series craft, also designed to be fly from orbit, do the same. The lift is there to offset their 'brick' status and to allow for the craft to travel farther, thus giving them more landing sites. The NASA article also gives a lot of information regarding pressure and other issues that spacecraft have to deal with deorbiting. Which is another reason why using anti-gravity is a wonderful thing - less stress, less heat, less everything when entering the atmosphere. You can essentially 'sink' to your landing spot, though air turbulence and such would probably require some powered flight in order to have more control and speed.

As to your tornado question, that's simple. Tornadoes create vortexes. They also create pressure differentials. Air pressure is something aircraft also deal with to generate lift. High pressure on the ground and lower pressure in the tornado, combined with the vortex, create lift. A tornado is very destructive thing with a helluva lot power in it. Things far heavier than a brick get picked up. I've never said air cannot generate enough force to provide lift. Please go back and re-read what I have said (and what I have quoted and cited). You will find that to be an incorrect statement.

Why do you think drag does not matter? Even if you don't want to listen to me it doesn't make your assumption wrong. Drag is a force just like lift. You can disbelieve me all day long but that won't change the science. It's not me, personally, saying that by the way.

M-drive does not ignore drag. NOTHING flying ignores drag unless there is a field surrounding the object that ignores fluid dynamics. An M-drive may be able to generate the same THRUST in both atmosphere and vacuum - however vaccum has zero drag and atmosphere has infinitely more. The greater the density the more drag there is and the more thrust you must apply to maintain your current flight envelope. Again you need not believe me personally. Do just a teeny-tiny amount of investigations and you will find this to be a true statement.

I agree that none of us know the true shape of the wing. But the illustrations provided, along with the obvious characteristics from the illustrations and how they differ so greatly from the ones you provided allow us to have an inference. While you may not want it to be true, you cannot deny how aerodynamics work. And even a cursory review of the field will support my point. I'm having a problem embedding images, but you can see from the drag curve diagram that as velocity increases so does drag - https://en.wikipedia.org/wiki/Lift-to-d ... flight.svg
Last edited by Moppy on Wed Feb 06, 2019 4:56 pm, edited 4 times in total.
phavoc
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Wed Feb 06, 2019 4:37 pm

Annatar Giftbringer wrote:
Wed Feb 06, 2019 1:26 pm
n MT that requires overloading, in Gurps and T5 it apparently does not. MgT says nothing about this.
How do Gurps and T5 handle thrust vectoring?
CONTRAGRAVITY SYSTEMS (GURPS Starships, p40)
(TL8)
Contragravity systems cancel out all natural gravitational forces acting on an object up to their rated lifting capacity, as discussed on pp. GT107 and S120. In GURPS Traveller, where reactionless thrusters are common, such technology is available but only necessary in very specialized applications. Each module counteracts 450 stons of weight at TL8, 1,500 stons at TL9, and 5,000 stons at TL10+. The module provides no lateral thrust.

CAN MY VESSEL REALLY FLY? (GURPS Starships, p40)
For extra detail, a ship required to fly in an atmosphere must have enough lift to compensate for its weight. This lift can come from three different locations: the hull (via streamlining),
contragravity, or vectored drives. One or both of the latter two are required if unstreamlined ships want to move around in an atmosphere – they don’t get any lift from the hull (see Streamlining, pp. 17 and GT119). The minimum required surface area to keep a streamlined ship in the air if its contragravity and/or vectored drive cannot totally compensate for the weight is 10 ´ LMass ´
square root of (LMass / Thrust), where LMass and Thrust are in stons. This formula indicates how much surface area is needed to stay in the air given the thrust of the vessel in one Earth atmosphere. If the CG or vectored drives can’t keep it in the air and the hull’s surface area is below this value, the design needs a bigger hull or to add more CG or drives.

REACTION AND MANEUVER DRIVES (GURPS Starships, p37)
There are two kinds of normal space drives: reaction drives and reactionless maneuver drives. A vessel needs some type of normal space drive to adjust its course through space; even “immobile” space stations and platforms will often have weak drives to make small corrections in their orbits. All normal space drives are available with long-term access and most are available with short-term access for use with small craft.

MANEUVER DRIVES
A maneuver drive (M-Drive) is a reactionless thruster that produces thrust without fuel or reaction mass. Each module has a vectored reactionless thruster and a power-plant slice to run it. Install as many M-Drive modules as desired. Short-term and half-sized modules are available, as well. See Ships Without Vectored Thrust Engines, p. GT174, for more information.

REACTION DRIVES
The reactionless maneuver drive is the most common form of slower-than-light propulsion in the Traveller universe, but far from the only one. At low TLs, reaction drives (rockets) of various sorts may be a better option or the only option available. Short-term modules are available for all except the HEPlaR drives and Solid Rocket Boosters. The Solid Rocket Booster has no access space, as it is disposable.

“Reaction drive” is a general term for any drive that involves throwing something out the back of the ship to make it go forward. The limiting factor on reaction drives is reaction mass – the material ejected as exhaust. A drive that uses a lot of reaction mass has limited acceleration, since carrying the reaction mass itself slows down the ship. But a ship which uses little mass, or which can pick up more while traveling, could in time accelerate to speeds approaching light speed. GMs that feel reaction drives are too archaic or too realistic may choose to ignore them completely. Alternatively, they may feel reactionless thrusters are too “super-science” and decide to use reaction drives exclusively (though this can substantially change the flavor of a Traveller campaign).
Early discussions of campaign style can avert the use of inappropriate technologies.

Thrust, mass, cost, and fuel consumption (in dtons per hour) are per module of drive. All drives are vectored thrust (except the Bussard ramjets). Most are already in halfspace increments.

Liquid Fuel Rockets are rocket engines that burn a mixture of fuel and oxidizer, and expel the resulting hot gas exhaust to create thrust. Liquid-fuel rocket engines are quite lightweight, but they are extremely fuel-thirsty.

Fission Rockets utilize a built-in fission reactor optimized to heat reaction mass and expel it to produce thrust. They are heavy and expensive. Their exhaust is also somewhat radioactive. Fission rockets require a Power Core appropriate for the drive TL (see p. 36).

Solid Rocket Boosters (SRBs, or solid fuel rockets) differ from the more advanced models of chemical rocket in that the fuel is part of the rocket engine. Each module installed either adds 20 minutes burn time or the rated thrust (in stons). Alternatively, the thrust may be doubled, halving burn time. In either case, once the rocket fuel has burned away, the rocket is useless. The remaining weight of the rocket casing is 15% of the fueled rocket and is usually jettisoned. SRBs may be externally mounted in any of the available external mountings (see p. 34). Cradles are generally not used because guidance of the rocket requires control connections. Hardpoints may be mounted on a larger assembly containing the SRBs, to hold the actual spacecraft itself.

Example: If a ship is using a TL8 SRB (providing 7 stons of thrust for 20 minutes) and it requires 14 stons of thrust, cut the burn time of the booster by 10 minutes or add another SRB module. If a thrust of 28 tons (4´) is required, cut burn time to 5 minutes (1/4´) or add three more SRB modules.

HEPlaR drives (High Energy Plasma Recombustion) are an advanced and efficient fusion drive. They add a heat exchanger/recombustion chamber to any existing fusion power plant. Hydrogen injected into the chamber is heated to a plasma state, and then magnetically accelerated further to produce a high-velocity stream of reaction mass. HEPlaR thrusters do require input power. They are not available in short-term versions. They incorporate crude, first-generation elements of the technology that eventually becomes reactionless thrusters.

Total Conversion Rockets are a total conversion drive; see Reaction Drives Table, p. S117. They convert fuel directly into energy. It is marginally “harder” science than a reactionless
thruster, since it does not violate the conservation of energy or momentum. It also requires ships to refuel occasionally even when the jump drives are not used.

Metal/Oxide Rockets burn a watery mixture of metal powder in liquid oxygen (Metal/LOX). The performance is substantially lower than other types, but they are sometimes used because fuel can be obtained by processing asteroids or lunar rocks.

Metal/LOX fuel (MOX) is a cryogenic slurry – the metal element may vary, though aluminum and magnesium perform about equally and are common in asteroids. It is a tricky fuel to burn, requiring tougher pumps and engine parts to resist abrasion from both the metal powder and the exhaust, which is essentially hot, fine sand. The advantage of Metal/LOX is that it can be produced from material commonly available on waterless vacuum moons and asteroids, where hydrogen is scarce.


I don't have my T5 CD handy to quote from there.
phavoc
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Wed Feb 06, 2019 5:10 pm

Moppy wrote:
Wed Feb 06, 2019 4:30 pm
@phavoc

Your physics is wrong.

"But I pasted it from NASA"

Yes but you pasted an article that doesn't describe in full how lift works.

You have many forces on a wing that provide lift. A partial list is:

(1) the pressure diferential above the wing "sucking" the aircraft up - caused by airfoil shape, and by tilting the wing upwards.

(2) Netwon's 3rd law. tilting the wing upwards meaning air being deflected downwards and creating an upward reaction.

If you admit there is air deflected downwards, you must also realise there is an upward reaction force exerted? This is how a helicopter rotor works, right? There's basically no difference between wing and rotor physics. Both are shaped, angled surfaces that are moved through air, generating an upward force by the same mechanisms.

In the case of a brick, (2) i think is more significant as it's a stupid shape for flying.

As for the airframe drag: If the m-drive needs more thrust in atmosphere to cancel out the increased drag, why can't it generate the same thrust in space, and therefore provide higher acceleration in vacuum?
[/quotoe]

Well, I'm not claiming ownership of the physics surrounding aerodynamics. I studied it but the math was too much for me. I'm not sure what is "wrong". Care to be more specific?

What was posted were basic illustrations of how lift works. The difficulty in responding to your statement is that you aren't citing all of the physics surrounding airfoil design. I have mentioned the basic forces (lift, thrust drag, mass). If you start talking about pressure you have to put parameters around the pressure. Are we talking sea-level, 5,000', 25,000'? And if you go down that route you have to factor in humidity and temperature. Hot and dry weather, coupled with high altitude, affect lift. So if you want to discuss, please pick the parameters to frame the discussion in. Otherwise we have to keep it general and at a higher level.

Newtons' 3rd law only barely references the concepts around wing angle. Newton's equations tangentially are part of more complicated aeronautical laws. Like most of science there are any number of previous laws that provide the foundation of further science. I prefer using Bernoulli's equations along with other explanations of fluid dynamics because they help to better model flight characteristics. At a basic level you can use Newton's 3rd law, but it can't be used for the more complex modeling (though like I mentioned it's an underlying aspect of aeronautics, but that's no different than saying the concept of multiplication is an underlying aspect of Newtonian equations. Each has it's proper place when correctly referenced and used).

By your question about air being deflected downwards I'm assuming you are referring to how lift works? Maybe this video will help you understand better - https://www.google.com/search?client=fi ... #kpvalbx=1 It's actually a good video, though it's really too short to do much more than scratch the surface.

Helicopters are a lot more complicated than planes. The blades of the helicopter change their angle of attack depending on the maneuver. If you want a better understanding of blade movement and such check out this video - https://www.youtube.com/watch?v=2tdnqZgKa0E

I do agree a brick is a horrible shape to be in if you want to fly using standard aeronautical laws. There are much better shapes to do this with. But it was one of the examples we started with. And hey, if the guys from Martin, who built stuff for NASA, can use it, I don't see why I can't.

Your question about airframe drag is easy. This goes back to fluidics. Both air and water are fluids. Any object moving through a fluid generates drag. Space is not a fluid, it'a a vacuum. Therefore there is no drag in space. Which is why in a fluid infinite thrust will be met with infinite drag. And that's not my math or physics, it's from people way smarter than me.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Wed Feb 06, 2019 5:13 pm

Moppy wrote:
Wed Feb 06, 2019 4:30 pm
As for the airframe drag: If the m-drive needs more thrust in atmosphere to cancel out the increased drag, why can't it generate the same thrust in space, and therefore provide higher acceleration in vacuum? We have to pick one of "game approximatation" or "negligible drag on hull"
Sorry to butt in, but M-drives have constant thrust.

In space that leads to constant acceleration.

In atmosphere it leads to a specific top speed, see e.g.
MT RM, p87 wrote:Space-Faring Craft: For space-faring craft, list the maneuver drlve thrust in Gs, the jump drive number, along with the standard atmosphere terrain following speed(NOE), cruising speed, and top speed for streamlined and airframe designs. ... Compute the speed values as shown for grav vehicles. Use the spacecraft's maneuver drive thrust in Gs directly as the maneuver thrust—skip the maneuver thrust computation.
So, an 1 g airframe ship, like the Subbie, has a top speed in atmosphere of ~1100 km/h, cruising speed of ~800 lm/h, and a NOE speed of ~270 km/h according to MT.
phavoc
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Wed Feb 06, 2019 5:23 pm

Condottiere wrote:
Wed Feb 06, 2019 2:00 pm

Flying wing.
The Yb-49. Too bad both prototypes were destroyed. The B-36 replaced it as the strategic bomber.
https://www.google.com/search?q=b-36+n ... --Mm8P8pM:

For scale purposes. The B-36 even had an oboard reactor for a prototype propulsion system.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby Annatar Giftbringer » Wed Feb 06, 2019 8:38 pm

phavoc wrote:
Wed Feb 06, 2019 4:37 pm
Annatar Giftbringer wrote:
Wed Feb 06, 2019 1:26 pm
n MT that requires overloading, in Gurps and T5 it apparently does not. MgT says nothing about this.
How do Gurps and T5 handle thrust vectoring?
CONTRAGRAVITY SYSTEMS (GURPS Starships, p40)
(TL8)
Contragravity systems cancel out all natural gravitational forces acting on an object up to their rated lifting capacity, as discussed on pp. GT107 and S120. In GURPS Traveller, where reactionless thrusters are common, such technology is available but only necessary in very specialized applications. Each module counteracts 450 stons of weight at TL8, 1,500 stons at TL9, and 5,000 stons at TL10+. The module provides no lateral thrust.

CAN MY VESSEL REALLY FLY? (GURPS Starships, p40)
For extra detail, a ship required to fly in an atmosphere must have enough lift to compensate for its weight. This lift can come from three different locations: the hull (via streamlining),
contragravity, or vectored drives. One or both of the latter two are required if unstreamlined ships want to move around in an atmosphere – they don’t get any lift from the hull (see Streamlining, pp. 17 and GT119). The minimum required surface area to keep a streamlined ship in the air if its contragravity and/or vectored drive cannot totally compensate for the weight is 10 ´ LMass ´
square root of (LMass / Thrust), where LMass and Thrust are in stons. This formula indicates how much surface area is needed to stay in the air given the thrust of the vessel in one Earth atmosphere. If the CG or vectored drives can’t keep it in the air and the hull’s surface area is below this value, the design needs a bigger hull or to add more CG or drives.

REACTION AND MANEUVER DRIVES (GURPS Starships, p37)
There are two kinds of normal space drives: reaction drives and reactionless maneuver drives. A vessel needs some type of normal space drive to adjust its course through space; even “immobile” space stations and platforms will often have weak drives to make small corrections in their orbits. All normal space drives are available with long-term access and most are available with short-term access for use with small craft.

MANEUVER DRIVES
A maneuver drive (M-Drive) is a reactionless thruster that produces thrust without fuel or reaction mass. Each module has a vectored reactionless thruster and a power-plant slice to run it. Install as many M-Drive modules as desired. Short-term and half-sized modules are available, as well. See Ships Without Vectored Thrust Engines, p. GT174, for more information.

REACTION DRIVES
The reactionless maneuver drive is the most common form of slower-than-light propulsion in the Traveller universe, but far from the only one. At low TLs, reaction drives (rockets) of various sorts may be a better option or the only option available. Short-term modules are available for all except the HEPlaR drives and Solid Rocket Boosters. The Solid Rocket Booster has no access space, as it is disposable.

“Reaction drive” is a general term for any drive that involves throwing something out the back of the ship to make it go forward. The limiting factor on reaction drives is reaction mass – the material ejected as exhaust. A drive that uses a lot of reaction mass has limited acceleration, since carrying the reaction mass itself slows down the ship. But a ship which uses little mass, or which can pick up more while traveling, could in time accelerate to speeds approaching light speed. GMs that feel reaction drives are too archaic or too realistic may choose to ignore them completely. Alternatively, they may feel reactionless thrusters are too “super-science” and decide to use reaction drives exclusively (though this can substantially change the flavor of a Traveller campaign).
Early discussions of campaign style can avert the use of inappropriate technologies.

Thrust, mass, cost, and fuel consumption (in dtons per hour) are per module of drive. All drives are vectored thrust (except the Bussard ramjets). Most are already in halfspace increments.

Liquid Fuel Rockets are rocket engines that burn a mixture of fuel and oxidizer, and expel the resulting hot gas exhaust to create thrust. Liquid-fuel rocket engines are quite lightweight, but they are extremely fuel-thirsty.

Fission Rockets utilize a built-in fission reactor optimized to heat reaction mass and expel it to produce thrust. They are heavy and expensive. Their exhaust is also somewhat radioactive. Fission rockets require a Power Core appropriate for the drive TL (see p. 36).

Solid Rocket Boosters (SRBs, or solid fuel rockets) differ from the more advanced models of chemical rocket in that the fuel is part of the rocket engine. Each module installed either adds 20 minutes burn time or the rated thrust (in stons). Alternatively, the thrust may be doubled, halving burn time. In either case, once the rocket fuel has burned away, the rocket is useless. The remaining weight of the rocket casing is 15% of the fueled rocket and is usually jettisoned. SRBs may be externally mounted in any of the available external mountings (see p. 34). Cradles are generally not used because guidance of the rocket requires control connections. Hardpoints may be mounted on a larger assembly containing the SRBs, to hold the actual spacecraft itself.

Example: If a ship is using a TL8 SRB (providing 7 stons of thrust for 20 minutes) and it requires 14 stons of thrust, cut the burn time of the booster by 10 minutes or add another SRB module. If a thrust of 28 tons (4´) is required, cut burn time to 5 minutes (1/4´) or add three more SRB modules.

HEPlaR drives (High Energy Plasma Recombustion) are an advanced and efficient fusion drive. They add a heat exchanger/recombustion chamber to any existing fusion power plant. Hydrogen injected into the chamber is heated to a plasma state, and then magnetically accelerated further to produce a high-velocity stream of reaction mass. HEPlaR thrusters do require input power. They are not available in short-term versions. They incorporate crude, first-generation elements of the technology that eventually becomes reactionless thrusters.

Total Conversion Rockets are a total conversion drive; see Reaction Drives Table, p. S117. They convert fuel directly into energy. It is marginally “harder” science than a reactionless
thruster, since it does not violate the conservation of energy or momentum. It also requires ships to refuel occasionally even when the jump drives are not used.

Metal/Oxide Rockets burn a watery mixture of metal powder in liquid oxygen (Metal/LOX). The performance is substantially lower than other types, but they are sometimes used because fuel can be obtained by processing asteroids or lunar rocks.

Metal/LOX fuel (MOX) is a cryogenic slurry – the metal element may vary, though aluminum and magnesium perform about equally and are common in asteroids. It is a tricky fuel to burn, requiring tougher pumps and engine parts to resist abrasion from both the metal powder and the exhaust, which is essentially hot, fine sand. The advantage of Metal/LOX is that it can be produced from material commonly available on waterless vacuum moons and asteroids, where hydrogen is scarce.


I don't have my T5 CD handy to quote from there.
Thanks!
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby Moppy » Wed Feb 06, 2019 9:23 pm

phavoc wrote:
Wed Feb 06, 2019 5:10 pm
I'm not sure what is "wrong". Care to be more specific?p
You said there there was no action/reaction component to lift coming from deflected air, so i said that, then you asked why it was wrong while admitting there was, and for some reason you've linked a video about elevators for "lift". It's a very disjointed chain of logic and I'm assuming maybe you typoed something due to posting speed, rather than changed around halfway. The broken formatting of your message supports this.

Just to make sure my position is clear, here is my summary of how wings work. It's very basic level and not in much detail. There's 2 main ways they work:

(1) Imagine your wing is tilted up at the front as if the plane was climbing. As the wing is advancing, air molecules hit the lower surface. We have 2 solid objects colliding. This must push the wing, and therefore the airplane, upwards and backwards, and deflect the air molecule downwards. This is basic newton's laws, and explains ONE of the many mechanisms by which a wing generates lift - a netwton's law reaction to the downward deflection of air. (In reality, air a fluid and we're imparting a turning motion to the fluid but that's hard to explain and this will do for a summary).

(2) Another way how a wing generates lift is that the airflow passing over the wing is disturbed, resulting in lower pressure above the wing than below. Pressure will attempt to equalise, and therefore push the wing up. There are various reasons why the pressure is lower above the wing and this is really complex. However the aerofoil shape on its own can't be responsible for this pressure difference above the wing, as planes can fly inverted and symetrical wings still work.

As you correctly mention, one can go very deep into this but there is no need for this situation. It's something you do if you have a 3d model and want to simulate its flight.

Helicopters. While they do change the parameters of their rotors, they still work in the same way, and there's very little difference in the physics of a rotor vs a wing. All fans, wings, rotors, propellers, and sails, both air and maritime, all work using these same basic principles described above. What causes most people problems is that bad schools teach that, because it's intuitive, that a helicopter blows air down and a plane works with air pressure.

Airframe Drag. I agree airframe drag must indeed exist in any system we know of right now, but we're talking about a spacecraft with identical acceleration in atmosphere and vacuum, and it's hard to relate the two.

BTW as someone with engineering training, we generally don't regard video or external links as credible for simple explanations, under the rule that "if you can't explain it yourself, you don't understand it properly". They're useful for looking up facts like the weight of a plane, or remembering an equation, but they should NOT be required for a simple explanation, and you should not need to use one. (edit: They are of course useful timesaving devices)
Last edited by Moppy on Wed Feb 06, 2019 9:59 pm, edited 1 time in total.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby Moppy » Wed Feb 06, 2019 9:47 pm

AnotherDilbert wrote:
Wed Feb 06, 2019 5:13 pm
Sorry to butt in, but M-drives have constant thrust.

In space that leads to constant acceleration.

In atmosphere it leads to a specific top speed, see e.g.
MT RM, p87 wrote:Space-Faring Craft: For space-faring craft, list the maneuver drlve thrust in Gs, the jump drive number, along with the standard atmosphere terrain following speed(NOE), cruising speed, and top speed for streamlined and airframe designs. ... Compute the speed values as shown for grav vehicles. Use the spacecraft's maneuver drive thrust in Gs directly as the maneuver thrust—skip the maneuver thrust computation.
So, an 1 g airframe ship, like the Subbie, has a top speed in atmosphere of ~1100 km/h, cruising speed of ~800 lm/h, and a NOE speed of ~270 km/h according to MT.
I'm considering Mongoose (edit: 2) and not MegaTraveller.

In Mongoose there is no restriction on a ship performing at its acceleration in atmopshere, and a specific allowance for anti-grav vehicles (which admittedly arent spacecraft) to ignore atmosphere and world size for performance. We can't tell if there is no ship limit because they forgot to define it, or because they chose not to set one. I am told there is note in companion (which I don't own but a friend told me) that spacecraft "don't usually have to make rolling aerodynamic landings".
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Wed Feb 06, 2019 10:47 pm

phavoc wrote: You have yet to provide a counter to all of the information available for the Type-R. It's mythical (unlike the things I'm providing). Unless and until you can provide engineering drawings and data from it's testing all anyone has to go by are the illustrations and the text description. Since you cannot provide any of the requested your, and mine, only source of information is the aforementioned illustrations. If you don't like the ones I've provided or referenced, please provide the baseline illustration you feel best represents the Type-R.
My point is that we don't have exact information, so how could I say one is better than any other?
From a purely aesthetic view I prefer the CT shape.

phavoc wrote: I have posted numerous times real, logical, and proven examples of the laws of aerodynamics, how lift is generated from craft traveling through the air. You have provided nothing of note in return. The preponderence of science and evidence firmly lies on my side. I still await a logical & reasonable rebuttal to how it can fly. Since you continue to not provide such an argument I can only assume that you neither have one nor that you believe you can present a logical one to defend your viewpoint. I need not quantify anything since you have provided nothing to substantiate your argument that it can. Your argument is one that you hear on the playground not one that should be debated between adults. Step up and prove your point - in at least SOME way.
I'm not trying to prove that it can fly, and as I have argued that would be impossible. I'm perfectly happy that the rules say it can fly, and the designer presumably intended it to.

You are claiming it can't possibly fly, you prove it.

Yes, you have talked a lot about aerodynamics, yet you have not produced any concrete data about how much lift the Subbie can generate.


You are being specific, thank you that is very helpful.
phavoc wrote: 1) Traveller ships are heavy.
2) Aeronautical lift requires surface area.

4) The heavier something is, the more lifting surface it requires.
5) All objects have drag in a fluid environment.
6) The faster you go the more drag you create. Infinite ...
7) Fluid environments include air and water.
8) To generate lift you have to go fast.
9) The laws of aerodynamics are applicable to Traveller ships.

11) There is no theoretical upper limit on how big or how heavy a craft can be to fly like an airplane.
Great! We agree, except about infinite speed and drag of course.

phavoc wrote: 3) Traveller ships have very little lifting surface area when compared to their mass.
10) At all times I have continually maintained the same stance - Traveller ships have to much mass and too little surface area to generate enough lift to takeoff or land using aerodynamics.
ALL Traveller ships?
ALL possible ships?
ALL Traveller ships you have seen?

Here is a 50 Dt pinnace I just designed:
Image
It has a boxy body of about 6 m × 3 m with a rounded front and wings to the side. It's mass is about 500 tonnes. It is intended to be able to fly.
Is this also completely unable to fly?

I'm not trying to be funny, I'm just trying to understand what you mean with "Traveller ships".

phavoc wrote: This, however, has nothing to do with the Type-R being unable to generate enough lift aerodynamically to takeoff or land.
Very well.

phavoc wrote: I agree that the exact amount of lift is not determinable without having all the necessary information to plug into the formula. However you fail to acknowledge any of the other aspects of this view. Neither of us will be able to produce data to generate a somewhat accurate estimate of the lift generated by the hull. That is an agreed upon issue.
Great! We agree.

phavoc wrote: Nevertheless, the preponderance of evidence as provided illustrates why the Type-R is unable to do so. You have continually refused to acknowledge this and provided nothing to rebut it.
That is, I believe, a legal term. It is devoid of meaning in science. Aircraft either fly, or they don't.

phavoc wrote: Using actual physical laws and applying them to an object such as the Type-R (as provided by copious illustrations - including the original ship) show us that the design will generate massive amounts of drag. It was you who wanted to used 4,000 tons for the mass of the Type-R. Applying that mass to how wings work is easy. As you have proven elsewhere you are able to solve for missing information (your Newton equations). You should know that you can simply toss out the CI portion and use base numbers. And that basic equation will state that the wing area (even giving you perfect lift for the entire underbody with zero drag) is insufficent to generate enough lift to takeoff or land. It is your refusal to accept common sense and logic that is the barrier.
If it's so easy, simply show that the Subbie generates less lift than its weight?

No, we can't disregard the lift coefficient Cl, it is unique for this particular airframe and situation.

phavoc wrote:
AnotherDilbert wrote:
phavoc wrote: You neglect, however, another aspect of the equation - mass. As multiple examples have pointed out, mass is a HUGE factor in determining lift.
No, lift is an aerodynamic force, unrelated to the mass of the aircraft.
Sigh.... And there you were saying you had a basic understanding. So either you lied upthread or you are lying here, or you lied upthread and you are professing true ignorance here. I have stated, repeatedly, that aerodynamic equations are MORE than simple newtonian ones. Since you apparently can't pay attention to a mass of text I have restated that here. I am sure you will ignore it again because, like Al Gore pointed out, it's an inconvenient truth. You said (now I doubt it) that you went through the slide show. It was rather long, but aerodynamics is complicated so it has to be. In that slide show mass is one of the items mentioned. The mass of the object flying determines how much lift is required to keep it flying. For someone who has such an attraction to Newton I fail to see how you cannot grasp such a simple concept. If Newton can grasp it, and you are able to parrot it back, how can you profess the view of a failure to understand the mass and lift are connected for aircraft?
I believe I understand what lift is and its connection to mass.

Shall we define lift again? From wiki:
A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.
Lift is expressed as (from the slides I quoted in my last post, but apparently never read):
Image
Note the curious lack of aircraft mass.

Or as I said a few days ago:
AnotherDilbert wrote:
Fri Feb 01, 2019 6:48 am
Aerodynamics can tell you the force of lift, but Newton's second is needed to tell you how the aircraft will move exposed to that force.
Or as the slide would have it:
Image
Or in the more general case (weight is dependent on mass):
Image

This is, I would say, very basic. Do we really disagree about this?


phavoc wrote:
AnotherDilbert wrote: Lift is proportional to wing area AND air flow speed squared, as we seems to have agreed before.
Thrust gives speed, as Newton explained; Speed gives lift, as aerodynamics explains.
Hence heavier aircraft need larger wings and/or higher take off speed to take off. Wing area alone is not sufficient to calculate lift.
Yes. And all objects have drag. Drag is the direct counter to thrust. As aerodynamics explains you cannot bully your way through the laws of physics. Newton explains that, too. How can you profess an understanding of physics, especially newtonian ones, and not grasp the basics of aerodynamics? I am at a loss to try to balance these two opposing viewpoints.
I fail to see your point. You were claiming that lift was dependent on wing area alone. I showed otherwise.

I trust we can agree that for a given airframe, with a specific Cd, more thrust means higher top speed?

And that for a given aircraft and runway, more thrust means we can accelerate to a higher take off speed?

phavoc wrote: First off, show me how the Type-R can go hypersonic (which is 5x the speed of sound or approximately 3,800mph or 1,700 meters/second). Please oh please explain that to me in aerodynamic terms. And, as you like to say, provide proof. I'd settle just to see the gyrations you will go through to explain how you can push an object through an atmosphere at that speed with just the nose of the Type-R. Please show me a hypersonic vehicle that has any similar designs (excluding objects that fall from space. All manned craft that humanity has put in orbit have fallen from the sky at hypersonic speeds. Type-R has to go UP, too).
You thoughtfully provided the answer to your own question. The Subbie has to not just take off, but also land.


phavoc wrote: Thirdly, I see you are studiously avoiding acknowledging the fact that the Type-R has insufficient lifting surface to generate lift according to science. You want to confuse your failure to prove your point by trying to make it to be a "illustrations are inexact".
"According to science" isn't an argument. Calculating specific lift, or at least bounding it, would be a scientific argument.

You believe the Subbie can't fly, but you can't show why, specifically.

phavoc wrote:
AnotherDilbert wrote:
phavoc wrote: ... - reality states the designs are unable to generate lift to fly ...
Yes, you believe that some unspecified designs and the Subbie are unable to generate enough lift and are unable to prove it?
Nope. If by 'unspecified' designs you mean all of the actual real-world designs I have cited, you are incorrect (again).
I mean unspecified Traveller craft, as you seem to claim.

phavoc wrote: I have illustrated that using aeronautical laws (which do not change regardless of the time frame) the Type-R is too heavy to generate enough lift utilzing it's wings to fly like an aircraft.
Great! Then what is the specific lift while taking off at say 500 km/h and 10° angle of attack at Earth standard atmosphere with a temperature of 20°? The weight is 40 MN.

phavoc wrote: You have yet to disprove any of that. Your argument has continually hinged upon, well, nothing. I have time and time again cited how aeronautics works and how the Type-R (using all available provided data) cannot follow the laws of physics to match the book description. You simply don't like that.
I have never tried to prove anything. You have claimed that the Subbie and some other unspecified Traveller ships can't possibly fly, you prove it.

You have showed nothing, you have offered opinion.

My state of mind is still irrelevant to your claim and lack of proof.

phavoc wrote: And you have clearly selected bits and pieces of various canon articles while avoiding the other bits and pieces of canon that dispute your same position. You have demonstrated continuosly that you are willing to selectively ignore anything that disagrees with your viewpoint. And you have demonstrated that you are willing to snippet things out of context, from canon literature no less, in an attempt to prove your point. But you have been caught time and again misrepresenting yourself and canon.
Please show where I misrepresented canon?
Where does canon explicitly state that thrust cannot be vectored?

phavoc wrote: It's not an extra assumption at all. As you have previously stated, MGT is very unclear and high-level, hence your desire to pull selected quotes from multiple previous iterations. By the very definition it's not an "extra" assumption. I am using Occam's razor correctly.
You started by assuming ships must descend and hover vertically:
phavoc wrote:
Wed Jan 30, 2019 4:20 am
You forget that starships don't take off like aircraft (e.g. no runways at most starports). ...
Therefore a ship must be able to take off and land vertically under it's own power with no ability for wings to provide lift.
This is an extra, unnecessary assumption.

You seem to claim that all ships must be able to land on all planets, regardless of gravity. That is an extra, unnecessary assumption.

phavoc wrote: If anti-grav is magical, then canon literature, in all variations, also references the magic. Vehicles use anti-grav, personal harnesses use anti-grave. Oh, wait! Now I get it! Those people who used anti-grave were flung off the faces of all the planets when they activated the devices! Ah! Now I understand your viewpoint! The magical technology has magically erased itself from existence!
You said (yes it is a snippet, but the original post is clearly linked):
phavoc wrote:
Sun Feb 03, 2019 12:34 am
In space, zero-G, gravity is nullifed. Amazingly enough you can still nullify gravity in orbit and stay attracted to a planetary body. Using your analogy above the ISS should be left behind as the planet (and star) accelerate away from it. So I guess the ISS is violating the space-time curvature?
...
Again a big, fat nope. All anti-grav/contragrav is doing is replicating the effect an object in space has closer to the surface of a planet.
You do understand the difference between free-fall in orbit and not being affected by gravity at all close to a planet?

Being bound by gravity to a planet, while at the same time not being bound by gravity, is a magical tech not found in Traveller.

phavoc wrote:
AnotherDilbert wrote:
Wed Feb 06, 2019 1:08 pm
Agreed, but we seem to completely disagree about how contragrav works in Traveller.
I don't seem to have a problem, but you apparently do. Somehow you think that a vessel activating it's anti-grav or CG would be magically flung off the planet, or perhaps finding itself drifting away. Yet, again magically, a vehicle utilzing the same technology has none of these problems. And, also apparently magically, your viewpoint of how it works doesn't seem to be referenced, nor user warning plastered anywhere about the dangers of turning on an anti-gravity device. Somehow everyone else seems to be able to grasp the concept and fit it within the gaming universe. Your view seems to be unique to yourself.
That is the obvious effect of the properties you claim CG has.

You do understand the difference between free-fall in orbit and not being affected by gravity at all close to a planet?

I have claimed the opposite, as specified by canon:
AnotherDilbert wrote:
Sat Feb 02, 2019 12:41 pm
AG is simple: One AG module provides a specified amount of thrust, nothing more, nothing less. It can push you away from the planet or pull you towards it. Gravity, mass, and weight are not affected.

phavoc wrote: Your selective memory and quoting is showing up again. You've already acknowledged multiple versions of canon Traveller that state AG/CG lifting is present. You have already acknowledged that MGT is very vague about many things, thus your need to quote across multiple editions. And, by the above, you have already agreed that these are not extra drive systems. To wit, you've already agreed they are present and canon. You simply don't want to admit your argument is not holding up.
You misrepresent my statements. Yes, AG exists in Traveller. Adding them to all ships per default would be an extra, unnecessary drive system in that ship.

phavoc wrote: You have yet to show what is included in the base cost for the hull. As you said, in other system, where they are stated, the majority of ships have them (that plan to land on planets at least).
You misrepresent my statements and canon. MT has AG in the design system, yet no standard ship I can recall have it. Gurps has CG in the design system, but many ships do not have it (and it is explicitly unnecessary if the M-drive is powerful enough).

phavoc wrote: And, as you stated, MGT doesn't mention them. The design systems that have them provide for them in the stated designs. Your reference to the vehicle design system is disingenious since we are not talking about starships. The vehicle design system also reference wheeled and tracked propulsion. It references many things that don't exists in the starship system, and vice versa.
The Vehicle system in MgT2 mentions AG drive and that is has a cost. Are you suggesting that AG drives in vehicles are a completely different technology than AG drives in spacecraft?

phavoc wrote: Lifesupport takes volume, power, mass and cost. Though didn't you say that mass is of no consequence in MGT, it's all volume based? So mass is out of the discussion and it never should have been referenced (another non-sequitur).
Just as in CT mass is simplified so we don't have to calculate it. It still exists. Or are you suggesting MgT repeals physics wholesale?

phavoc wrote: I believe MGT just lumps all ships systems into a Power bucket. If you want to split it out, how much is allocated to the inertial compensator? How much to the lighting? How much to... My way is far simpler - it's there and it's a system that is only needed for planetary activities. All ships have more than enough power for this even under the amorphous design system.
Drive systems have specific power requirements in MgT2.

Yes, it is simpler to ignore inconvenient facts.

phavoc wrote: Ships having CG for lift is not my explanation. It's Traveller canon.
Yes, in TNE. TNE did also not have normal M-drives, nor were ships explicitly pulled by gravity in the movement system. CG did still have a cost, volume, mass, and power requirement.

phavoc wrote: Amazingly your Harrier jump jet is pictured flies according the previously cited laws of aerodynamics. Unless this image, too, is not correctly representing the Harrier. Since you are questioning all the of the Type-R imagery I think it's probably safer to say that all images are suspect, ergo they shouldn't be used because they may be suspect.
But does it use vectored thrust? You seem to claim that spacecraft with vectored thrust cannot do exactly this.

phavoc wrote: Where is that happening? Quoting the rules is somehow misrepresenting what you said? In your zeal to misrepresent the rules you fail to add in those rules that weaken your argument. If you do not want the rules used (correctly) against you then I suggest you stop quoting rules. And, by the way, you have added tons of non-sequitur issues to this. If you don't like it, stop doing it.
I have never claimed vectored thrust must roll for malfunction, as you seem to imply.
You are conflating MT and MgT rules.

phavoc wrote: What source is there to read? The question was rather clear. The source was the question. The ship has 1G drives, the planetary gravity is 1.4. What other specifications are there to be provided? Whether it was Pirates of Drinax or some random planet in the Traveller universe the question remains the same. And, once again, you failed to provide an answer. Instead you seek to deflect the issue and make vague reasons on why you cannot, using your interpretation of the rules, answer it. All of this is a classic sign your argument cannot be relied upon to provide a valid answer.
What does the text say exactly? Is the ship streamlined? Is the gravity specified to be 1.4 g, or just assumed? How is the starport described? Why was the Highport bypassed?

phavoc wrote: Wow. Talk about conceptual twisting. You can't even accept the definition of what Occam's razor is.
Do you prefer the modern "When presented with competing hypotheses to solve a problem, one should select the solution with the fewest assumptions" or the classic "We may assume the superiority ceteris paribus of the demonstration which derives from fewer postulates or hypotheses"?

phavoc wrote: Not only that but you try to deflect by using a logical fallacy. Traveller canon is not being changed at all. For one things CG lift IS canon.
Ships having CG by default is a change in canon.

phavoc wrote: Your fallacy is attempting to equate all of Traveller canon into a single set, which is of itself a fallacy because each version is it's own canon. To the best of my knowledge, if you want to use the word 'canon' then only T5 and MGT are canon because accepted canon includes only those versions currently in print. Or, if you want a more expansive definition, canon would be restricted specifically to each version, thus canon cannot be across multiple versions. Pick one definition and stick with it.
Canon is not easily defined:
http://www.travellerrpg.com/CotI/Discus ... hp?t=35542

But I would agree that each edition has its own canon, informed by the editions it builds on. So MgT builds on CT, but not necessarily T5.

phavoc wrote: It changes nothing. Unless you are conflating change with clarification. That's entirely possible. As you have agreed to, it's not changing Traveller at all. Some versions specifically call it out, others (such as MGT) say nothing about it. Ergo it's not change using MGT, it's clarification.
I have not agreed to anything of the sort.

Only Mongoose can clarify what they actually mean.

phavoc wrote:
AnotherDilbert wrote: And I completely disagree with your definition of common sense.
I expect no less from you. In fact I now expect it.
That is the problem with invoking "Common Sense", it is not well defined.

phavoc wrote: Again, a reference to magic. When did the space orks and angry fairies start sprinkling magic in your set of rules, let alone with your sophmoric attempts at "logic"? Here you talk about aircraft using wings as common sense... yet you refuse to accept aeronautical laws that govern how they work. It is only you who speaks of magical CG drives. I've never argued for AG/CG drives, that's purely you boyo! My statements have been exclusively centered around CG/AG to provide lift. You have hysterically argued about people being flung off the planet (which vaguely reminds me of how people spoke of flight before they understood it. Silly ignorant people!). You cannot seem to grasp the basic concept that CG lift in a starship would perform no differently than what a vehicle does, or a person in a AG harness. Unless those people are magically flung off the planet, too. As to cost/volume, cost is already there with no defined list of what you spending on in a "hull", and volume is already an amorphous blob that it has no bearing. If you are so concerned about volume, tell me how ships get landing gear when it's not defined? How much do they cost? What is their volume?? Oh, wait, it's not defined and of no consequence since it's assumed to be part the cost of the "hull". Funny how common sense works...
You do understand the basics of how gravity works?

You do understand the difference between free-fall in orbit and not being affected by gravity at all close to a planet?

You are postulating CG with properties contrary to gravity, I call that magical.


phavoc wrote: Hrm... since the argument has centered around the Type-R with it's 1G drive, AND since Type-R DOES land (unless you are going to try and argue they don't land), I would say your statement remains false. You claim to have a basic understanding of aeronautics so you should be able to understand the Type-R has insufficient lifting area to fly like an airplane. Unless you want to also reject all of that and just spew crap out.

The Drinax treasure ship is in canon material. It has a 1G drive, and no wings. It takes off and lands on a 1.4G planet. Take your rule and make that work. Oh, wait, according to your rule it can't land, but canon says it does. According to your rule it uses a highport instead, but canon again says it lands.

Seems canon is right and you are wrong.
Canon say streamlined spacecraft land using their wings. So you appeal to canon, when you reject canon?

Yes, I have a very basic understanding of aerodynamics; I can, for example, not calculate the lift of an aircraft after glancing at a hand drawing of it. Without that I'm unable to determine if a specific aircraft can fly, apparently unlike you.

I have no idea what is going on with the Treasure ship, I have not read the source.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Wed Feb 06, 2019 11:38 pm

Moppy wrote: I'm considering Mongoose (edit: 2) and not MegaTraveller.
You are of course free to disregard other editions.

But that makes it somewhat difficult to say much at all about ship performance. For example I believe ships do not technically have a specified acceleration, but a "Thrust rating". I assume that is an acceleration, based on earlier editions...

This does not appear to not imply that spacecraft ignore atmospheric forces:
Core, p143 wrote:ATMOSPHERIC OPERATIONS
A streamlined ship is designed to enter a planetary atmosphere, and can function like a conventional aircraft. Pilot checks are required in high winds and other extreme weather.

Partial streamlining allows a ship to skim gas giants and enter Atmosphere codes of 3 or less, acting in the same way as streamlined ships. In other atmospheres, the ship will be ponderous and unresponsive, reliant on its thrusters to keep it aloft.

An unstreamlined ship is completely non-aerodynamic and if it enters an atmosphere it runs the risk of sustaining serious damage. Such a ship must make a Pilot check at DM-4 when it enters an atmosphere and for every minute of flight. Each failed check inflicts 1D damage to the ship, ignoring any Armour.

This actually specifies speed, not acceleration.
Core, p163 wrote:Spacecraft are capable of any Speed Band listed in the Vehicles chapter, and will typically be going at Hypersonic speeds when entering an atmosphere.
I believe spacecraft are still bound by the acceleration rules in the Vehicle chapter, while using the Vehicle combat system:
Core, p130 wrote:A vehicle may change its current speed by one Speed Band at the start of every combat round if it is travelling at Fast speed or less, or by one Speed Band every minute if it is travelling faster.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Thu Feb 07, 2019 12:22 am

Moppy wrote: ... and a specific allowance for anti-grav vehicles (which admittedly arent spacecraft) to ignore atmosphere and world size for performance.
Ah, I think I have found what you mean. I believe that is just an exception to the Airborne Movement Rule:
Core, p130 wrote:Airborne Movement
Most aircraft (vehicles that use the Flyer skill) are designed for a specific atmosphere and planetary gravity. This means aircraft can only fly on worlds with Size and Atmosphere types within 2 of their world of creation.
...
In any case, aircraft require a minimum Atmosphere code of 1 in order to function. Aircraft descriptions include the Size and Atmosphere types of their world of manufacture.

Grav Vehicles
Vehicles using the Flyer (grav) skill employ anti-gravity technology rather than traditional methods of flight and so are unaffected by the Atmosphere and Size of worlds they travel on.

Grav vehicles still have a stated top speed, implying drag.


The Vehicle Handbook says:
VH, p16 wrote:Streamlined
High performance grav vehicles can be designed with aerodynamic hulls that allow them to travel at much greater speeds.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Thu Feb 07, 2019 3:55 am

Amount of lift generated by a Type-R:

Lifting co-efficient - it's not known so I used one for a 747. That is .29

Density of air at sea level - 1.2754 kg/m(cubed)

Wing Surface area - I used the entire lower portion of type R- 450 sq/meters

Velocity Flow - the speed you are going to take off at - I used 100 m/s

Mass of a Type-R in 1G is 4,000 tons or 8,000,000lbs

I used a calculator online (here - https://www.vcalc.com/wiki/MichaelBartm ... ce+of+Lift ) to determine lifting capability. Lift generated is 832,198N.

In order for a craft to climb the amount of lift must be greater than the mass.

We can change the mass to 4,000 metric tons, which equals 4,000,000 kg. You need approximately 10N to lift 1kg. That's 40,000,000 million N to lift 4,000 metric tons.

The above formula does not take into account any drag. We haven't even discussed the lift generated by the wing using Bernoulli's equation. Pressure has to be higher under the wing. The design of the wing roots would cause vortices to disrupt the smooth flow of air over the top of the wing, which to generate the lift has to flow faster than underneath. All of the images show the wing to be flat. All of the images show a massive and relatively flat wing root at least 1m tall. Airflow from the front will impact this and cause the drag. All modern wing designs have a some rounding on the leading edge, or if like the F-104, they are very thin. In any case no wing design has such a large flattened surface for much of the leading edge. If you can find one (in reality and has similar characteristics please share).

BTW, you asked about infinite drag - Image. This is what is meant by that.

Oh, and for it to have flight characteristics like an aircraft it's also going to have to have wheeled landing gear because it will require some runway to take off (747 requires 2000m, but the characteristics are going to be different).

I don't suppose this will convince you, but you asked me to prove it. Please check my math. If you want to alter the lifting coeffecient that's fine. As before I said it had insufficient lift to fly aerodynamically.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Thu Feb 07, 2019 5:58 am

Jeezus. And you complained about MY "wall of text"???????
AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: You have yet to provide a counter to all of the information available for the Type-R. It's mythical (unlike the things I'm providing). Unless and until you can provide engineering drawings and data from it's testing all anyone has to go by are the illustrations and the text description. Since you cannot provide any of the requested your, and mine, only source of information is the aforementioned illustrations. If you don't like the ones I've provided or referenced, please provide the baseline illustration you feel best represents the Type-R.
My point is that we don't have exact information, so how could I say one is better than any other?
From a purely aesthetic view I prefer the CT shape.
Use the original Keith drawing. Though this is MGT, so using the ship illustration from the book is more fair. Wing design doesn't change from either illustration in any material way.
AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: I have posted numerous times real, logical, and proven examples of the laws of aerodynamics, how lift is generated from craft traveling through the air. You have provided nothing of note in return. The preponderence of science and evidence firmly lies on my side. I still await a logical & reasonable rebuttal to how it can fly. Since you continue to not provide such an argument I can only assume that you neither have one nor that you believe you can present a logical one to defend your viewpoint. I need not quantify anything since you have provided nothing to substantiate your argument that it can. Your argument is one that you hear on the playground not one that should be debated between adults. Step up and prove your point - in at least SOME way.
I'm not trying to prove that it can fly, and as I have argued that would be impossible. I'm perfectly happy that the rules say it can fly, and the designer presumably intended it to.

You are claiming it can't possibly fly, you prove it.

Yes, you have talked a lot about aerodynamics, yet you have not produced any concrete data about how much lift the Subbie can generate.
I have. Check the math. Now prove your Type-R can fly using wings.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
Great! We agree, except about infinite speed and drag of course.
I posted the chart specifically for you. I don't care that you don't agree with it. It's a fact. You don't seem to like facts that go against your argument. (shrug)

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
ALL Traveller ships?
ALL possible ships?
ALL Traveller ships you have seen?
SHIPS, yes. I never mentioned small craft. I was referenced to known designs. I specifically tried to disabuse you of the Type-R. I believe I have proven this mathematically now. With great handwavium or ludicrous responses you can offset real science. That is always possible.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: Nevertheless, the preponderance of evidence as provided illustrates why the Type-R is unable to do so. You have continually refused to acknowledge this and provided nothing to rebut it.
That is, I believe, a legal term. It is devoid of meaning in science. Aircraft either fly, or they don't.
It is used in law, yes. Jeezus, now you are complaining about words? Look it up in the Oxford dictionary and tell me it's being used wrong. It's not. You are just throwing crap up because you cannot provide a rebuttal (oops, another 'legal' term... shakes head).

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: Using actual physical laws and applying them to an object such as the Type-R (as provided by copious illustrations - including the original ship) show us that the design will generate massive amounts of drag. It was you who wanted to used 4,000 tons for the mass of the Type-R. Applying that mass to how wings work is easy. As you have proven elsewhere you are able to solve for missing information (your Newton equations). You should know that you can simply toss out the CI portion and use base numbers. And that basic equation will state that the wing area (even giving you perfect lift for the entire underbody with zero drag) is insufficent to generate enough lift to takeoff or land. It is your refusal to accept common sense and logic that is the barrier.
If it's so easy, simply show that the Subbie generates less lift than its weight?

No, we can't disregard the lift coefficient Cl, it is unique for this particular airframe and situation.
It's done. You will, of course object. I'm sure there is an apple on the shelf somewhere that you will reference, or some other silly nonsense. If you don't like the assumptions made, give me others. It will still fail due to science. It's very simple.


AnotherDilbert wrote: No, lift is an aerodynamic force, unrelated to the mass of the aircraft.
Sigh.... And there you were saying you had a basic understanding. So either you lied upthread or you are lying here, or you lied upthread and you are professing true ignorance here. I have stated, repeatedly, that aerodynamic equations are MORE than simple newtonian ones. Since you apparently can't pay attention to a mass of text I have restated that here. I am sure you will ignore it again because, like Al Gore pointed out, it's an inconvenient truth. You said (now I doubt it) that you went through the slide show. It was rather long, but aerodynamics is complicated so it has to be. In that slide show mass is one of the items mentioned. The mass of the object flying determines how much lift is required to keep it flying. For someone who has such an attraction to Newton I fail to see how you cannot grasp such a simple concept. If Newton can grasp it, and you are able to parrot it back, how can you profess the view of a failure to understand the mass and lift are connected for aircraft?
[/quote]
I believe I understand what lift is and its connection to mass.

Shall we define lift again? From wiki:
A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.
Lift is expressed as (from the slides I quoted in my last post, but apparently never read):
Image
Note the curious lack of aircraft mass.

Or as I said a few days ago:
Aerodynamics can tell you the force of lift, but Newton's second is needed to tell you how the aircraft will move exposed to that force.
[/quote]

Seriously? You are going to play the stupid quoting game again when you HAVE ALREADY PROVIDED EXAMPLES OF LIFT IN AERONAUTICS IN THIS VERY POST? Just how stupid are you going to get with your circular arguments? You want definitions and then you ignore them - even ones you post to yourself. Look below at your quotes. Do you not see MASS/WEIGHT as part of the explanation?

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
Or as the slide would have it:
Image
Or in the more general case (weight is dependent on mass):
Image

This is, I would say, very basic. Do we really disagree about this?
Honestly at this point I think you would disagree with yourself if you were standing in the rain and argue that you weren't wet, but that your clothes were.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote:
AnotherDilbert wrote: Lift is proportional to wing area AND air flow speed squared, as we seems to have agreed before.
Thrust gives speed, as Newton explained; Speed gives lift, as aerodynamics explains.
Hence heavier aircraft need larger wings and/or higher take off speed to take off. Wing area alone is not sufficient to calculate lift.
Yes. And all objects have drag. Drag is the direct counter to thrust. As aerodynamics explains you cannot bully your way through the laws of physics. Newton explains that, too. How can you profess an understanding of physics, especially newtonian ones, and not grasp the basics of aerodynamics? I am at a loss to try to balance these two opposing viewpoints.
I fail to see your point. You were claiming that lift was dependent on wing area alone. I showed otherwise.

I trust we can agree that for a given airframe, with a specific Cd, more thrust means higher top speed?

And that for a given aircraft and runway, more thrust means we can accelerate to a higher take off speed?
To take off your lift must exceed your mass. I have shown a Type-R has insufficient wing area to do so. You haven't 'shown' anything. You can fail to see whatever you want (and obviously that's a pretty long list at this point). If you cannot grasp this this very basic explanation then maybe you need to stop tryiing to rebut it. If you don't understand then go educate yourself. It's not my job to educate a person who claims they have a basic grasp of aerodynamics and then claims ignorance when it is convenient for them. The world is full of information. Go forth and learn some of it.

If you want to "show" me something, then "show" me how much wing area is necessary to get 4,000 metric tons aloft. Use the CL of a A380, a 747, a An-225. If you insist you can do it via thrust alone, then calculate the required distance to generate sufficient lift. Oh, and FYI - Traveller starports have never been drawn to have multi-km long runways. As to your airfame, if you want to go there, then you'll have to design one far more efficient than the Type-R with it's very blocky nose and massive drag built into its' wings. That is the airframe you are given. Oh, wait, that's just a waste because you'll say you can't because... whatever reason. Basically you failed, again, to "show" anything other than your attempt at distraction.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: First off, show me how the Type-R can go hypersonic (which is 5x the speed of sound or approximately 3,800mph or 1,700 meters/second). Please oh please explain that to me in aerodynamic terms. And, as you like to say, provide proof. I'd settle just to see the gyrations you will go through to explain how you can push an object through an atmosphere at that speed with just the nose of the Type-R. Please show me a hypersonic vehicle that has any similar designs (excluding objects that fall from space. All manned craft that humanity has put in orbit have fallen from the sky at hypersonic speeds. Type-R has to go UP, too).
You thoughtfully provided the answer to your own question. The Subbie has to not just take off, but also land.[/quote[

AND, you did it again. You stated it was hypersonic capable. You were challenged to prove that statement that it was capable of doing so from the ground. It was thoughtful of you to once again fail. Thank you, you continue to prove my point with each failure you interject into the conversation. A failure to support your assertion.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: Thirdly, I see you are studiously avoiding acknowledging the fact that the Type-R has insufficient lifting surface to generate lift according to science. You want to confuse your failure to prove your point by trying to make it to be a "illustrations are inexact".
"According to science" isn't an argument. Calculating specific lift, or at least bounding it, would be a scientific argument.

You believe the Subbie can't fly, but you can't show why, specifically.
Neither are your statements. It's a argumentative position. Oh, and science, being real and not an argument, doesn't mean it's not present. I do believe you have quoted your favorite fellow, Mr. Newton, multiple times. So are you now saying you were in error by saying "according to newton's law..."? His laws, after all, are science.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote:
Nope. If by 'unspecified' designs you mean all of the actual real-world designs I have cited, you are incorrect (again).
I mean unspecified Traveller craft, as you seem to claim.
Which specific unspecified craft do you wish to discuss?

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: You have yet to disprove any of that. Your argument has continually hinged upon, well, nothing. I have time and time again cited how aeronautics works and how the Type-R (using all available provided data) cannot follow the laws of physics to match the book description. You simply don't like that.
I have never tried to prove anything. You have claimed that the Subbie and some other unspecified Traveller ships can't possibly fly, you prove it.

You have showed nothing, you have offered opinion.

My state of mind is still irrelevant to your claim and lack of proof.
Once again, you are incorrect. You have tried to prove that my statements are incorrect, that the illustrations are not indicative of how the ships are, and that a Type-R is capable of flying like an aircraft and being able to land. You have continually asserted that it can by disputing the argument, ergo you are attempting to prove your point correct and mine incorrect. I have offered the science behind how planes fly. I have offered actual facts of how the lifting body program was set up, and how the lifting body craft never were able to take off, just land after being dropped from altitude. You have asserted all kinds of things, so you must be trying to prove something.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: And you have clearly selected bits and pieces of various canon articles while avoiding the other bits and pieces of canon that dispute your same position. You have demonstrated continuosly that you are willing to selectively ignore anything that disagrees with your viewpoint. And you have demonstrated that you are willing to snippet things out of context, from canon literature no less, in an attempt to prove your point. But you have been caught time and again misrepresenting yourself and canon.
Please show where I misrepresented canon?
When you snippeted, out of the MGTv1 book, the alternative movement rules around gravity wells. You attempted to use that to justify your statement. It was quoted out of context, which is why you selectively quoted only part of the text and not all of it. You did so knowingly, thus my point is valid.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote: It's not an extra assumption at all. As you have previously stated, MGT is very unclear and high-level, hence your desire to pull selected quotes from multiple previous iterations. By the very definition it's not an "extra" assumption. I am using Occam's razor correctly.
You started by assuming ships must descend and hover vertically:
phavoc wrote:
Wed Jan 30, 2019 4:20 am
You forget that starships don't take off like aircraft (e.g. no runways at most starports). ...
Therefore a ship must be able to take off and land vertically under it's own power with no ability for wings to provide lift.
This is an extra, unnecessary assumption.

You seem to claim that all ships must be able to land on all planets, regardless of gravity. That is an extra, unnecessary assumption.
Once again the preponderance of evidence proves your point invalid. SHIPS are too heavy to generate aeronautical lift to take off and land as the illustrations suggest. If you are too blind or too stupid to understand that is your place to be. That is an extra, but necessary assumption to make when discussing this with you.


AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
You do understand the difference between free-fall in orbit and not being affected by gravity at all close to a planet?

Being bound by gravity to a planet, while at the same time not being bound by gravity, is a magical tech not found in Traveller.
Wow. Again, just wow. So all the antigrav vehicles is now magical tech not found in Traveller? Lemme get some popcorn. I really want to hear you come up with an explanation to this one.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
phavoc wrote:
I don't seem to have a problem, but you apparently do. Somehow you think that a vessel activating it's anti-grav or CG would be magically flung off the planet, or perhaps finding itself drifting away. Yet, again magically, a vehicle utilzing the same technology has none of these problems. And, also apparently magically, your viewpoint of how it works doesn't seem to be referenced, nor user warning plastered anywhere about the dangers of turning on an anti-gravity device. Somehow everyone else seems to be able to grasp the concept and fit it within the gaming universe. Your view seems to be unique to yourself.
That is the obvious effect of the properties you claim CG has.

You do understand the difference between free-fall in orbit and not being affected by gravity at all close to a planet?
Dude, you can try to obfuscate this as much as you want, your circular logic-fu is, again, failing. It was you who claimed antigrav/countergrav fitted to starships would make them magically fly off a planet. Unfortunately for your view this fails common sense. Otherwise no antigrav/cg would be possible. Yet it is, in all versions. You can play stupid all you want with your games, it doesn't make your point any more invalid.
AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm
I have claimed the opposite, as specified by canon:
AnotherDilbert wrote:
Sat Feb 02, 2019 12:41 pm
AG is simple: One AG module provides a specified amount of thrust, nothing more, nothing less. It can push you away from the planet or pull you towards it. Gravity, mass, and weight are not affected.
This is supposed to mean what? You seem to think if you obfuscate what CG/AG is it somehow strengthens your argument. It doesn't. Both can provide vertical lift, hover and descent. Those are the only things germane to this discussion and have been since the first page. You can continue this pattern as long as you want. It just makes you look stupider because it's meaningless.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

You misrepresent my statements. Yes, AG exists in Traveller. Adding them to all ships per default would be an extra, unnecessary drive system in that ship.
If you state it exists here, but dispute it upthread, which is your position? All I'm doing is feeding your own statements back to you.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

You misrepresent my statements and canon. MT has AG in the design system, yet no standard ship I can recall have it. Gurps has CG in the design system, but many ships do not have it (and it is explicitly unnecessary if the M-drive is powerful enough).
Nope, not at all. MGT leaves it blank. Thus my statement still stands. Yours fails because you never responded to it. You also fail to acknowledge that (a) for the Type-R that we discuss, it has CG, thus using GURPS 'Can it Fly on it's own" paragraph, it's acknowledged that it cannot generate enough lift. Do a count of designs that enter atmosphere and tell me how many have CG, and how many do not.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

The Vehicle system in MgT2 mentions AG drive and that is has a cost. Are you suggesting that AG drives in vehicles are a completely different technology than AG drives in spacecraft?
We are debating space ships, not vehicles. Once again you fail at answering the question and continue to pursue a non-sequitur.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

Just as in CT mass is simplified so we don't have to calculate it. It still exists. Or are you suggesting MgT repeals physics wholesale?
It's just as valid to say it the other way. If you weren't playing stupid (again) you would know the answer to your own question. Figure it out.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

Drive systems have specific power requirements in MgT2.

Yes, it is simpler to ignore inconvenient facts.
Drives do (M and Jump) weapons do. Life support does not. Lights don't. The food processor does not. The automated air fresheners in the heads do not. You can split all the hairs you want but your point remains just as invalid. My point stands, you just don't want to accept it works.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

Yes, in TNE. TNE did also not have normal M-drives, nor were ships explicitly pulled by gravity in the movement system. CG did still have a cost, volume, mass, and power requirement.
In GURPS it did too. GURPS also put in CG for the ships that could not fly on their own. So my statement remains correct.

AnotherDilbert wrote:
Wed Feb 06, 2019 10:47 pm

But does it use vectored thrust? You seem to claim that spacecraft with vectored thrust cannot do exactly this.{/quote]

It does indeed! That has already been answered. And you already didn't like to hear that with vectored thrust it is unable to take off fully loaded. But you don't like inconvenient facts like that. They tend to weaken your argument. Oh, and you cannot account for heavy grav worlds other than "maybe they don't land on them". Great explanation!
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Thu Feb 07, 2019 12:02 pm

phavoc wrote:
Thu Feb 07, 2019 5:58 am
Jeezus. And you complained about MY "wall of text"???????
Please, I'm not trying to be hostile, snarky (with occasional lapses, sorry), or disingenuous.

I just don't know what you mean, EXACTLY.

I don't understand you, EXACTLY.

And you appear to not understand me. (Note I did not say anything about you, but of my view of your posts.)

I don't know what this fundamental lack of understanding is caused by. You appear to see my posts as overly pedantic, I see your posts as inexact, sometimes bordering on incomprehensibility.

When I see such inexactness, I ask for specific detail. This is not hostility or disingenuousness, but me trying to understand you.


To take a simple example I still don't understand exactly what aircraft you claim are unable to fly. It is some set of ships including the Subbie. By nagging about it I believe I have understood that you have no problem with large or heavy aircraft in principle, but some specific ships, but I still don't know what exact ships (except that it includes the Subbie).

I believe that means that we could design some new ships with apparently reasonably low drag and big enough wings, and you could accept that they could fly, but I'm still not sure.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Thu Feb 07, 2019 2:31 pm

phavoc wrote: Amount of lift generated by a Type-R:
Thank you, this is basically what I have asked for all along.

To prove that it can't possibly fly, you have to show that it can't generate enough lift under any circumstances, even borderline improbable, not just a specific case with random parameters.

So, I will calculate another case, with deliberately favourable parameters. If it still fails to fly that says a lot more...

phavoc wrote: Lifting co-efficient - it's not known so I used one for a 747. That is .29
That seems low? What case is that? This source www.ae.utexas.edu/~varghesep/class/airc ... stions.pdf seems to indicate that typical max Cl at take off is about 1.5-2.2.

I believe that we have to take off at less than CL max to avoid stall, so I will use an approximate value of 1.8, somewhat less than the max.

phavoc wrote: Density of air at sea level - 1.2754 kg/m(cubed)
OK.

phavoc wrote: Wing Surface area - I used the entire lower portion of type R- 450 sq/meters
I guesstimated 500 m² wing area, from a CT deckplan schematic earlier. I will stick with it. I don't believe we have the accuracy to distinguish between two estimates that are just 10% apart.

phavoc wrote: Velocity Flow - the speed you are going to take off at - I used 100 m/s
We could just as well use a higher speed, say 200 m/s. Yes, that is high, but if we are to prove that is can't possible fly, we have to use all possible values.

phavoc wrote: Mass of a Type-R in 1G is 4,000 tons or 8,000,000lbs

In order for a craft to climb the amount of lift must be greater than the mass.

We can change the mass to 4,000 metric tons, which equals 4,000,000 kg. You need approximately 10N to lift 1kg. That's 40,000,000 million N to lift 4,000 metric tons.
Agreed.

phavoc wrote: I used a calculator online (... ) to determine lifting capability. Lift generated is 832,198N.
OK, I get:

L = ½ρv²ACl = ½ × 1.2754 × 200² × 500 × 1.8 ≈ 23 MN.

23 MN lift < 40 MN weight, so it appears it can't take off.

But if we have vectored thrust, which I assume, we can direct some thrust upwards. If we direct the thrust upwards at, say, 45° angle we get about 40 MN × cos(45°) = 40 MN × 1/√2 ≈ 28 MN forward thrust and 40 MN × sin(45°) = 40 MN × 1/√2 ≈ 28 MN upward thrust.

So, we have forces of 23 NM (lift) + 28 MN (thrust) = 51 MN accelerating the ship upwards, and 40 MN (weight) accelerating the ship downwards for a total force of 51 - 40 = +11 MN accelerating the ship upwards. The ship will lift, in this specific case.

phavoc wrote: The above formula does not take into account any drag.
Agreed.

In the simplest case it would be something like:

D = ½ρv²ACd = ½ × 1.2754 × 200² × 500 × 0.12 ≈ 1.5 MN << available thrust.

Note that I took the approximate Cd of a 747 and quadrupled to account for the shape of the Subbie and AoA, I have no idea if that is reasonable.


phavoc wrote: We haven't even discussed the lift generated by the wing using Bernoulli's equation. Pressure has to be higher under the wing. The design of the wing roots would cause vortices to disrupt the smooth flow of air over the top of the wing, which to generate the lift has to flow faster than underneath.
That is an aerodynamic force, included in Lift?

phavoc wrote: All of the images show the wing to be flat. All of the images show a massive and relatively flat wing root at least 1m tall. Airflow from the front will impact this and cause the drag. All modern wing designs have a some rounding on the leading edge, or if like the F-104, they are very thin. In any case no wing design has such a large flattened surface for much of the leading edge. If you can find one (in reality and has similar characteristics please share).
I don't consider it to be my job to prove your claim, but in an effort of good will I have looked for illustrations of the Subbie:
Image
Image
They appear to show wings with rounded leading edges and perhaps a thickness of less than 1 m. I can't be very sure of relative dimensions, or course.

Some sources show a straight wing, others show a rounded cropped delta wing.

phavoc wrote: BTW, you asked about infinite drag - [sorry, ran out of URLs]. This is what is meant by that.
Thank you, but I don't understand. I see no infinite drag in the graph, that would be far above the top of the graph. If you mean stall that is characterised by a quick loss of lift, not infinite drag?

Physically the effect of infinite drag would be roughly as if you had run into a mountain. The infinite force would stop the aircraft instantly, with infinite acceleration, turning the aircraft into shredded wreckage.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Thu Feb 07, 2019 2:42 pm

AnotherDilbert wrote:
Thu Feb 07, 2019 12:02 pm
phavoc wrote:
Thu Feb 07, 2019 5:58 am
Jeezus. And you complained about MY "wall of text"???????
Please, I'm not trying to be hostile, snarky (with occasional lapses, sorry), or disingenuous.

I just don't know what you mean, EXACTLY.

I don't understand you, EXACTLY.

And you appear to not understand me. (Note I did not say anything about you, but of my view of your posts.)

I don't know what this fundamental lack of understanding is caused by. You appear to see my posts as overly pedantic, I see your posts as inexact, sometimes bordering on incomprehensibility.

When I see such inexactness, I ask for specific detail. This is not hostility or disingenuousness, but me trying to understand you.


To take a simple example I still don't understand exactly what aircraft you claim are unable to fly. It is some set of ships including the Subbie. By nagging about it I believe I have understood that you have no problem with large or heavy aircraft in principle, but some specific ships, but I still don't know what exact ships (except that it includes the Subbie).

I believe that means that we could design some new ships with apparently reasonably low drag and big enough wings, and you could accept that they could fly, but I'm still not sure.
You understand fine. You have shown the previous ability to infer things. You have shown intelligence and creativity. You have shown the necessary skills to do estimations and figure things out. That you choose not to exercise those skills in this posting is a choice. Feigning ignorance when your position has failed is a sign of poor character, and should be a warning to anyone who attempts to intelligently engage you.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Thu Feb 07, 2019 4:03 pm

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
Thank you, this is basically what I have asked for all along.

To prove that it can't possibly fly, you have to show that it can't generate enough lift under any circumstances, even borderline improbable, not just a specific case with random parameters.

So, I will calculate another case, with deliberately favourable parameters. If it still fails to fly that says a lot more...

That seems low? What case is that? This source www.ae.utexas.edu/~varghesep/class/airc ... stions.pdf seems to indicate that typical max Cl at take off is about 1.5-2.2.

I believe that we have to take off at less than CL max to avoid stall, so I will use an approximate value of 1.8, somewhat less than the max.
Fair enough. But let's put some parameters around this A craft has to take off from a stop. A 747 will never reach a 2.2 number. And my .29 number was at ground level at a stop because all craft start at that point if they want to take off.

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
I guesstimated 500 m² wing area, from a CT deckplan schematic earlier. I will stick with it. I don't believe we have the accuracy to distinguish between two estimates that are just 10% apart.
That's overly generous, but we'll use those numbers, too. I used the MGT deck plans, since we are talking MGT.

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
We could just as well use a higher speed, say 200 m/s. Yes, that is high, but if we are to prove that is can't possible fly, we have to use all possible values.
Umm, that is 720kph. Your suggestion here is that during the takeoff run your takeoff speed is 50% of supersonic? At basically ground level?? Sure.... let's go with that, too.

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
23 MN lift < 40 MN weight, so it appears it can't take off.

But if we have vectored thrust, which I assume, we can direct some thrust upwards. If we direct the thrust upwards at, say, 45° angle we get about 40 MN × cos(45°) = 40 MN × 1/√2 ≈ 28 MN forward thrust and 40 MN × sin(45°) = 40 MN × 1/√2 ≈ 28 MN upward thrust.

So, we have forces of 23 NM (lift) + 28 MN (thrust) = 51 MN accelerating the ship upwards, and 40 MN (weight) accelerating the ship downwards for a total force of 51 - 40 = +11 MN accelerating the ship upwards. The ship will lift, in this specific case.
The CL you are using includes an AOA. If you go and look at the numbers, a 747, during it's climb, will have a CL of 1.8. So in this case you are double-dipping in your numbers. Also, you are assuming this craft will take off like an aircraft. Why? Because to generate lift it has to move forward at speed.

Also, you asked me previously about where is the power coming for CG? I would ask you the same thing here. Your forward thrust is being provided by your M-drive. You cannot have full thrust from the drive aft AND vector it downwards. You have X amount of thrust to choose from. You are proposing X+X, or nearly doubling.

Further, let's go with what you said many posts ago. A 1G drive, for a 4,000 metric ton ship, can put out 40MN. Using your numbers above, you have stated you are using 51MN of thrust. The problem is your drive now requires itself to be overloaded just to take off from a 1G world. You need 30% (rounded up) more power. The rules state:

Overload Drive (Engineer) (CRB MGTv2, p160)
By overloading the manoeuvre drive, the engineer can lend the ship extra speed and manoeuvrability. A successful Difficult (10+) Engineer (m-drive) check (1 round, INT) will increase the ship’s Thrust by one during the next round. If the check fails with an Effect of –6 or less, the manoeuvre drive suffers a critical hit with Severity 1, as detailed on page 160. This check suffers
a cumulative DM-2 each time it is attempted after the first.
This penalty can be removed by performing maintenance on the drive, a procedure that requires Engineer (m-drive) and 1D hours.


Overload Plant (Engineer) (CRB MGT v2, P160)
A favourite of engineers on action vids, the power plant can be overstressed on a temporary basis to provide the ship with more Power points. A successful Difficult (10+) Engineer (power) check (1 round, INT) will increase the ship’s current Power points by +10% during the next round. If the check fails with an Effect of –6 or less, the power plant suffers a critical hit with Severity 1, as detailed on page 160. This check suffers a cumulative DM-2 each time it is attempted after the first. This penalty can be removed by performing maintenance on the power plant, a procedure that requires Engineer (power) and 1D hours.


Power requirements for the Type-R (CRB MGTv2, p184): Basic Ship Systems - 80, M-Drive: 40, Jump drive: 40 Sensors:1 Power Generated: 135.

At takeoff it requires 121 power, which leave 14 in reserve. Overloading the drive, as stated, doubles the output of the drive, but would logically require double the power (80). Per the rules you can only get 10% more power out of the plant (14 points). Not sufficient.

However, if allowed, you could just overload the M-drive by 30% to gain 12 extra M-drive thrust points. 30% additional power could be found by the 14pts in reserve. This would make it possible to generate enough overload thrust to take off from a 1G world with a 1G drive.

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
In the simplest case it would be something like:

D = ½ρv²ACd = ½ × 1.2754 × 200² × 500 × 0.12 ≈ 1.5 MN << available thrust.

Note that I took the approximate Cd of a 747 and quadrupled to account for the shape of the Subbie and AoA, I have no idea if that is reasonable.
I find it rather amazing that you now are able to not only grasp aerodynamics, but you can express them mathematically. And yes, your numbers are not reasonable. You are not at all considering how much worse the aerodynamics are for a Type-R vs a 747. Simply amazing your understanding has changed so radically in the last 12hrs.

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
I don't consider it to be my job to prove your claim, but in an effort of good will I have looked for illustrations of the Subbie:
Image
Image
They appear to show wings with rounded leading edges and perhaps a thickness of less than 1 m. I can't be very sure of relative dimensions, or course.

Some sources show a straight wing, others show a rounded cropped delta wing.
The top image, based on the angle, could be interpreted either way, so we'll discard that one. The smaller, fuzzier one, is coming from GURPS I believe. GURPS already establishes the Type-R requires CG lift. These examples are different than yours. I have included the original canon one as well. You will notice that what you find in the rule books are different than yours. But, if we go to the original image from Keith, it, too, clearly shows what I am referring to - large flattened wing roots. You agree with my 1m approximate flat thickness? Well, hallelaujah!

https://imgur.com/gallery/230RyVu

AnotherDilbert wrote:
Thu Feb 07, 2019 2:31 pm
Thank you, but I don't understand. I see no infinite drag in the graph, that would be far above the top of the graph. If you mean stall that is characterised by a quick loss of lift, not infinite drag?

Physically the effect of infinite drag would be roughly as if you had run into a mountain. The infinite force would stop the aircraft instantly, with infinite acceleration, turning the aircraft into shredded wreckage.
Sigh.... feigning ignorance again? Well, if you can do the above math then you can read a frigging image. It's very clear that as your velocity increases drag decreases, but then climbs back up in a reverse bell curve. You can clearly see in the upper right quadrant that as velocity continues to increase, drag will increase at the same rate.

Stall is a flight characteristic shared by planes. It is not applicable here for either of our views. You have maintained that vectored thrust is used from the main drive, ergo there is no stall. I have maintained CG is used, ergo no stall. No stall is necessary or part of the discussion.

And yes, much like objects slamming into the atmosphere, they are moving extremely fast and then go from zero drag to large armount. And they shatter, they disintegrate, they cease. Most, not all. Some are too massive, though none of them have infinite velocity. The chart shows what happens, as does your mountain analogy.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Thu Feb 07, 2019 5:21 pm

phavoc wrote:
Thu Feb 07, 2019 2:42 pm
<Ad hominems and strawmen snipped>
Very well, polite engagement is impossible.

I will not waste my time on you.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby phavoc » Thu Feb 07, 2019 6:18 pm

Old School wrote:
Sat Feb 02, 2019 7:36 pm
So I haven’t been following all the back and forth, but I thought it might be helpful for ya’ll to explain this terms of an example.

I have attached a picture of an Imperial Treasure Ship, which is a 1600 ton, 1G capable ship opersted by the Imperial Navy. In the Pirates of Drinax adventure “Treasure Ship”, this ship lands and later departs from the downport on Acrid under its own power. Acrid is a size A, 1.4 G world, with a violent atmosphere that requires atmospheric weather control to allow ships to land safely.

Can each of you involved in this debate explain the process by which this ship lands and takes off?

Image
AnotherDilbert - Now that you are able to understand the requirements, here is the question you have studiously avoided.

Here is some text description of the ship from the adventure:

The ship barely qualifies as streamlined. It can enter a planet’s atmosphere, supported by its vestigial lifting surfaces and overworked grav-plates, but it does not so much fly as fall in roughly the right direction. The prow of the ship is hinged, allowing access to the cavernous cargo bay. 300 tons of cargo space is unsecured, but the huge secure vault contains another 60 tons of space at the heart of the ship.

A 1,600 ton displacement ship that has no wings (per the illustration). The Drive is 1G and produces 160 MN thrust without overloading the drive. The planetary gravity is 1.4, thus the effective displacement is 2,240 tons. The drive size, however, does not change (using the previous discussion, a 1 G drive produces 10MN thrust for each 100 tons displacement). Powerplant output is 570 pts. Stated power requirements are 320pts for basic systems, 160pts for M-drive, 480 pts for the jump drive, 2 pts for sensors and 72pts for weapons. When the M-drive is active the ship is consuming 482pts of power, which leaves a reserve of 88pts. The ship takes off and lands under it's own power at the planetary starport. Since you asked, it is a A-class starport.

Explaining how the ship can perform this maneuver under MGT-only rules using vectored thrust. Powerplant overloading (10% maximum) is not required. Drive overloading (to 2G) is required. Using the stated numbers above, the ship, using vectored thrust explanation, would require 224 pts of power (160 * 40%) to land and take off from the planet. Overloading of the drive to get 40% more thrust requires 64pts of power. There is a reserve of 88pts, so no powerplant overloading is necessary.

Under the vectored thrust explanation, this ship can take off from any world up to 2G. After that it is incapable of adding any more power to the M-drive.

According to the ship description, it has vestigial lifting surfaces and overworked grav-plates. I'd like to point out that the Floating Palace is held aloft by anti-gravity systems and that King Oleb's Hawk Warriors are all equipped with grav harnesses. So anti-gravity capabilities abound in the book. Somehow (magically perhaps?) the Floating Palace manages to stay floating above the planet with no issues. Also on the planet Neumann (pop 10 billion) entire buildings float on gravity platforms. And the supplement uses both anti-grav, grav, and contragravity interchangably.

As you can see from the image it's not at all designed to aircraft aerodynamic standards. And, as you can read, there are numerous examples of large structures floating above planets just fine on AG/CG. So there should be no reason why a ship would have any problems (without having to summon a magical being). The ships description uses grav-plates in referencing the needed lift to enter a planet's atmosphere.

I'm sure you will dispute this, but you have AG/CG specifically mentioned in MGT related to a starship using it to get to orbit and to land on a planet. I checked MGT v1 CRB and HG - no mention of vectored thrust. There is a mention of thruster plates. In MGTv2 vectored thrust for aircraft (a vehicle) is mentioned. There is no mention of it in HG v2.

So it would appear that under MGT rules your position is not supported. It would appear that I have found ONE specific reference in material released by the publisher. I do believe that makes AG/CG canon and vectored thrust (for starships) non-canon for this edition.
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Re: A lot of worlds over 1g gravity. How do 1G thrust ships take off?

Postby AnotherDilbert » Thu Feb 07, 2019 7:05 pm

phavoc wrote:
Thu Feb 07, 2019 6:18 pm
Continue your lies if you wish, I no longer care.

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