Atmospheric Operations

[phavoc]

Pg 143 – Atmospheric Operations: The previous page listed types of hulls as streamlined, standard and dispersed. This section talks about streamlined and unstreamlined. The terms are different and potentially confusing. Unstreamlined should read standard hull configuration ships (or change the original definition and add in that standard ships are considered unstreamlined for atmospheric interaction).

Also, it says a standard hull ship requires thrusters to stay aloft in the atmosphere. That’s incorrect, they rely on anti-grav for lift (streamlined do as well. No spaceship can use aerodynamics to generate enough lift to fly - they are too heavy. Streamlining means better maneuvering though. The third paragraph makes it out that standard hulled ships would never enter an atmosphere. Yes, they can be ungainly and slow, but with anti-grav they can simply float up or down without risk.

 

[Rikki Tikki Traveller]

Also, they use the term Partially Streamlined - These should be the Standard Hull configuration. Dispersed is the Unstreamlined.

I think you should use the hull shapes exclusively.

 

[wbnc]

The Antonov An-225 would probably count as a starship sized small craft if it were in traveler..it has 45,000 cubic feet of cargo space...that's around 80 to 90 dtons of baggage volume.

When I was writing my catalog I submitted the option for aerodynamic flight surfaces for starships... they would work to allow dead stick glides, and controlled power off landings. I didn't monkey with the idea of reducing fuel while in atmo for simplicity sake.


from 80,000 feet a shuttle can glide across the continental US after a ballistic reentry, and make a very controlled landing..it's almost 100 tons of small craft

 

[phavoc]

That's true, the shuttle does mostly deadstick. But it's a very carefully plotted deadstick and it still has real wings to help with the lift.

Back in the early 80s the programmers ar NASA (a company called Singer Link) did the simulators. They programmed in an attempt by the Russians to intercept the shuttle over the Pacific and shoot it down. But it would be doing Mach 25 till it got near CA and started it's velocity shedding maneuvers.

Unfortunately a congressman was on a visit and didn't realize all what he was seeing and accused them of playing video games. They weren't allowed to make up other simulations like that any more.

 

[wbnc]

That's true, the shuttle does mostly deadstick. But it's a very carefully plotted deadstick and it still has real wings to help with the lift.

Back in the early 80s the programmers ar NASA (a company called Singer Link) did the simulators. They programmed in an attempt by the Russians to intercept the shuttle over the Pacific and shoot it down. But it would be doing Mach 25 till it got near CA and started it's velocity shedding maneuvers.

Unfortunately a congressman was on a visit and didn't realize all what he was seeing and accused them of playing video games. They weren't allowed to make up other simulations like that any more.

Too bad, those simulations help work out small details you might not see until the numbers get turned into action...or at least virtual projections. the shuttle is one of the best designed pickup trucks ever built...the aerodynamics are surprisingly complicated for something that was meant to simply haul cargo up and down

for several commercial ships/small craft I did I included aerodynamic flight surfaces, and heat shielding. This is added on during ship design and cant be retrofitted.....but it allows a ship or small craft to make unpowered, ballistic entry into an atmosphere, with a controlled landing at the end..as long as it has a clear runway or flat patch of dry lake bed.

You can do the same with a lifting body design, with the hull itself generating enough lift for controlled descent. but once you break 100-300 tons I don't see much in the way of cruise flight without at least partial gravitic drive...

 

[phavoc]

That's true, the shuttle does mostly deadstick. But it's a very carefully plotted deadstick and it still has real wings to help with the lift.

Back in the early 80s the programmers ar NASA (a company called Singer Link) did the simulators. They programmed in an attempt by the Russians to intercept the shuttle over the Pacific and shoot it down. But it would be doing Mach 25 till it got near CA and started it's velocity shedding maneuvers.

Unfortunately a congressman was on a visit and didn't realize all what he was seeing and accused them of playing video games. They weren't allowed to make up other simulations like that any more.

Too bad, those simulations help work out small details you might not see until the numbers get turned into action...or at least virtual projections. the shuttle is one of the best designed pickup trucks ever built...the aerodynamics are surprisingly complicated for something that was meant to simply haul cargo up and down

for several commercial ships/small craft I did I included aerodynamic flight surfaces, and heat shielding. This is added on during ship design and cant be retrofitted.....but it allows a ship or small craft to make unpowered, ballistic entry into an atmosphere, with a controlled landing at the end..as long as it has a clear runway or flat patch of dry lake bed.

You can do the same with a lifting body design, with the hull itself generating enough lift for controlled descent. but once you break 100-300 tons I don't see much in the way of cruise flight without at least partial gravitic drive...

The shuttle is essentially a flying brick, with wings. The mass of a scout ship would be, I think, much heavier due to the mass of the metal, especially if they are using a heavier armor like collapsed plating (on the other hand crystal iron could be quite light for it's strength). At some point the mass/weight of the ship is simply too great for the wings to provide any true lift. It can provide SOME, but I don't think enough to offset things. I suppose with control surfaces you can glide more horizontal than vertical.

Hrm... maybe it might work. Anybody wanna run the numbers for a super-heavy flying brick and what kind of lift it might get while falling out of the sky? I suppose the safari ship might work as an example. Though we have no idea what it masses.

 

[AKAramis]

Hrm... maybe it might work. Anybody wanna run the numbers for a super-heavy flying brick and what kind of lift it might get while falling out of the sky? I suppose the safari ship might work as an example. Though we have no idea what it masses.

Using MT and TNE/T4 numbers...
The mass per Td (Ton-displacement) for merchants runs between 5 and 10 metric tons per Td. Warships with heavy armor run up to 25 metric tons per Td.

As a rough guide, simplifying from TNE, using megagrams (Mg) instead of the synonymous T for tonnes, as they are the same unit but Mg is clearer vs Td for displacement.
Jump Drives: 42 Mg per Td
Maneuver Drive: 28 Mg per Td
PP: TL ≤12: 4 Mg per Td
PP TL 13-14: 3 Mg per Td
PP: TL 15: 2 Mg per Td
Sensors: 28 Mg per Td
Bridge: 0.2 Mg per Td, +2 Mg for computer and comms. (so, Mg=2+Td/10)
Screens: about 10 Mg per Td
Fuel: LHyd is 1 Mg/Td
Cargo: 10 Mg per Td*
Staterooms: 1 Mg per Td.
Turrets: about 26 Mg per Td

 

[wbnc]

That's true, the shuttle does mostly deadstick. But it's a very carefully plotted deadstick and it still has real wings to help with the lift.

Back in the early 80s the programmers ar NASA (a company called Singer Link) did the simulators. They programmed in an attempt by the Russians to intercept the shuttle over the Pacific and shoot it down. But it would be doing Mach 25 till it got near CA and started it's velocity shedding maneuvers.

Unfortunately a congressman was on a visit and didn't realize all what he was seeing and accused them of playing video games. They weren't allowed to make up other simulations like that any more.

Too bad, those simulations help work out small details you might not see until the numbers get turned into action...or at least virtual projections. the shuttle is one of the best designed pickup trucks ever built...the aerodynamics are surprisingly complicated for something that was meant to simply haul cargo up and down

for several commercial ships/small craft I did I included aerodynamic flight surfaces, and heat shielding. This is added on during ship design and cant be retrofitted.....but it allows a ship or small craft to make unpowered, ballistic entry into an atmosphere, with a controlled landing at the end..as long as it has a clear runway or flat patch of dry lake bed.

You can do the same with a lifting body design, with the hull itself generating enough lift for controlled descent. but once you break 100-300 tons I don't see much in the way of cruise flight without at least partial gravitic drive...

The shuttle is essentially a flying brick, with wings. The mass of a scout ship would be, I think, much heavier due to the mass of the metal, especially if they are using a heavier armor like collapsed plating (on the other hand crystal iron could be quite light for it's strength). At some point the mass/weight of the ship is simply too great for the wings to provide any true lift. It can provide SOME, but I don't think enough to offset things. I suppose with control surfaces you can glide more horizontal than vertical.

Hrm... maybe it might work. Anybody wanna run the numbers for a super-heavy flying brick and what kind of lift it might get while falling out of the sky? I suppose the safari ship might work as an example. Though we have no idea what it masses.

Okay lets see...a AN-225 has a takeoff weight of 640 tons, if I remember right one conversion displacement tons to gross tons is 5 gross tons per displacement ton....so a 100 ton scout is 500 gross tons. which means you could probably make a 100 ton aerodynamic flight capable 100 ton ship.

I'd say at 200 tons, or 1000 gross tons....you'd be pushing the upper limit of lift...it would take some damn good engineering...but using titanium, carbon fibers, and polymer/composites you could probably manage a decent powered flight. It'd be a pain to handle outside of basic maneuvers.

Since it's cruising and landing not taking off you could probably maintain a fairly decent glide with a 300 ton ship, and a safe landing glide up to around 400 tons.

Bigger than that you'd be lucky to manage a steep emergency descent..with a bone jarring high speed landing...if you have a huge flat surface to handle the landing at the sort of stall speed you would be dealing with.

http://www.freelancetraveller.com/features/shipyard/tonnage.html

 

[Infojunky]

The real question I am having is why would anyone do a ballistic reentry if they didn't have too?

Look at it this way most ships aren't one a orbit entry trajectory when they move in from the 100 diameter limit unless they are planing to orbit, and often not even then. With Contragravity and the Enormous amount of thrust available to even a 1g ship one can essentially park at whatever altitude one wants until clearance to land then set down with effectively a 0 kph groundspeed.

 

[phavoc]

The real question I am having is why would anyone do a ballistic reentry if they didn't have too?

Look at it this way most ships aren't one a orbit entry trajectory when they move in from the 100 diameter limit unless they are planing to orbit, and often not even then. With Contragravity and the Enormous amount of thrust available to even a 1g ship one can essentially park at whatever altitude one wants until clearance to land then set down with effectively a 0 kph groundspeed.

Quite right! Grav-equipped ships would leisurely enter atmo - at least compared to an unpowered ballistic entry. Plus it would be relatively stress-free on the ships frame and hull, making the owners quite happy. The only people who should be looking to get down to the ground fast would be daredevils and assault landers under fire. Coming in hot and fast from orbit just makes you a nice bright candle that's easily tracked.

 

[wbnc]

The real question I am having is why would anyone do a ballistic reentry if they didn't have too?

Look at it this way most ships aren't one a orbit entry trajectory when they move in from the 100 diameter limit unless they are planing to orbit, and often not even then. With Contragravity and the Enormous amount of thrust available to even a 1g ship one can essentially park at whatever altitude one wants until clearance to land then set down with effectively a 0 kph groundspeed.

Being ballistic entry capable would be a safety feature for scouts, small traders etc. such Ships routinely visit planet surfaces, and may operate away from the safety of larger starports. If they were damaged such as a critical failure of their drives, or lost drives during entry the could make a high speed entry. While a controlled landing might be out of the question they could use areobraking maneuvers to reduce their speed to something more survivable than entry velocity.

While the landing would be brutal, it would be more survivable than a supersonic faceplant. would also give the crew time to evacuate the ship by air raft, or grav chute, rather than riding the ship down. Bailing out of a high speed object is a very risky proposition, at supersonic speeds it is near suicide....even with modern ejector seats.

 

[phavoc]

A ship that had no aero control surfaces and no drive and no antigravity is just screwed. They would have no method to do shuttle like maneuvers to shed velocity. Even though it cannot use its wings to take off like a regular aircraft the shuttle does have wings, a rudder and other control surfaces to alter it's course. A spaceships maneuvering thrusters are designed to make a ship turn in space or with anti grav turned on. Being on a ballistic nosedive at high speeds is just a death ride.

The scouts hull isn't the type that would generate lift like an aircraft wing. None of the starship would really. The subsidized merchant has a wing which would certainly help generate some lift. If it had the same characteristics as a aircraft wing that would do the trick. Not sure how effective wingless would be for control vs a standard or twin tail though. I suspect it might have some issues. Still, the B2 doesn't have one, but it has a unique design that overcomes that limitation.

Which kind of begs the question just how tough the average free trader might be to take that sort of structural stress from aerodynamics. Would it bend or tear parts of the frame if it attempted such a landing? Sure it may have a tough hull, but the frame is built to take steps certain ways, and it's not magically invulnerable.

 

[Infojunky]

Couple of issues with your logic here....

If they were damaged such as a critical failure of their drives, or lost drives during entry the could make a high speed entry. While a controlled landing might be out of the question they could use aerobraking maneuvers to reduce their speed to something more survivable than entry velocity.

A critical failure of the drives, in the 1st case then you are on a fixed course from where the drive failed, as such is out of the question as you can't maneuver to enter the parameters of a Aerobrake landing (it is a very small corridor). For the second case if you are already doing a conventional landing and the drive fails then Terminal velocity is the speed you are limited to in Atmosphere.

Note; the straight fall to ground has potential to be supersonic in early parts of the fall but as air density increases the maximum speed of terminal velocity decreases.

I think the confusion here is that you are mixing up orbital speeds with landing speeds and how they interact. My stipulation is that Supersonic speeds in atmosphere are not necessary for either launch or reentry as the most craft have sufficient means to move directly to space without that tedious stop in orbit....

 

[wbnc]

Couple of issues with your logic here....

If they were damaged such as a critical failure of their drives, or lost drives during entry the could make a high speed entry. While a controlled landing might be out of the question they could use aerobraking maneuvers to reduce their speed to something more survivable than entry velocity.

A critical failure of the drives, in the 1st case then you are on a fixed course from where the drive failed, as such is out of the question as you can't maneuver to enter the parameters of a Aerobrake landing (it is a very small corridor). For the second case if you are already doing a conventional landing and the drive fails then Terminal velocity is the speed you are limited to in Atmosphere.

Note; the straight fall to ground has potential to be supersonic in early parts of the fall but as air density increases the maximum speed of terminal velocity decreases.

I think the confusion here is that you are mixing up orbital speeds with landing speeds and how they interact. My stipulation is that Supersonic speeds in atmosphere are not necessary for either launch or reentry as the most craft have sufficient means to move directly to space without that tedious stop in orbit....

I understand the issue, as well as anyone without a degree in physics and aeronautical engineering can.

My point, was that having the ability to execute a dead stick entry would be a good safety feature. not a standard means of making a landing. But certainly something a buyer might look at if they operate away from systems with a search and rescue system in place.

my thought processes, were not flawed..I only forgot to explain some assumptions I made.

FIrst
the vehicle in question would have to have the ability to maneuver without main drives. i assumed a starship would have the means to maneuver without it's main drives...that's a common sense precaution.

second
Ballistic entry capable ( more than just heat shielding and a streamlined form)would also include means of maneuvering the ship in atmosphere. Using reaction thrusters, or aerodynamic controls. If the feature was added to a design as a potential safety feature, some means of positive control would be included in the design.

If the ship has the aerofin option. it has plenty of control surface to work with. NASA lifting body designs had ridiculously small fins for stable flight. With any streamlined body, simple pop out panels to increase drag in one direction or another would be sufficient to allow for wide S-turns to burn energy and allow the pilot to maintain a safe flight speed.

as for entry speeds, I am assuming that a ship would be cruising at several hundred miles an hour during entry.

Mostly due to the fact I don't see anyone letting a starship descend straight down over a starport instead requiring them to enter atmosphere away for the port and then approach from some distance away.

well not after the first ship looses power during entry and landing dead center of the starport. a few million pounds of ship, cargo, fuel, and a fusion powerplant landing on the tarmac at terminal velocity would ruin your day...

but since most people dont enjoy drifting along like a blimp when they can go faster... I am going with the ships pushing a few hundred miles an our just to cut down on flight time.


By the way from a near dead stop Felix Baumgartner hit nearly 850 mph in free fall from upper atmosphere. nothing to do with the discussion, but good lord supersonic without an airplane!!!

 

[phavoc]

Most starships aren't going to be streamlined to the detail that aircraft are. Some might, but much of the artwork shows otherwise. With no need to generate real lift and their primary place being in space that makes a lot of sense. They have no need for aerodynamics because they can push it aside with brute force (fusion-powered thrusters and anti-grav).

Most ships are going to rely upon their anti-grav for lift, and their main drive for thrust. Secondary movement would most likely be based upon maneuvering thrusters, which are designed to maneuver the ship while it's on anti-grav or in space. Depending on which drive failed, a ship could land with just anti-grav, or perhaps make it back up into space on just maneuvering thrusters. But if both have failed, yeah, it's gonna drop like a rock. One of the reasons the shuttle can do what it does is that it's coming in ballistically, so it has forward momentum to help keep it aloft. If it were to simply sink into the atmosphere it would drop straight down, maybe if it got it's nose down and then traded velocity for lift it would have more options. Even regular aircraft, once they get into a flat spin with no lift can crash and burn.

And starships are going to be much heavier and less maneuverable than pure aircraft. Even with aerofins you have a brick, with no wings, but a few control surfaces. The aerofins still have to overcome mass (which is something Traveller doesn't deal with when it comes to ships) to do any sort of maneuvers. Aerofins on a spacecraft might be tough, but they would fail like regular aerostructures if stressed too much.

Your best bet, to survive something like this, would be to have an emergency anti-grav system (battery powered) that tries to arrest your fall at the last possible instant, possibly burning itself out in the process to get you down on the ground in hopefully a single piece.

 

[Infojunky]

My point, was that having the ability to execute a dead stick entry would be a good safety feature. not a standard means of making a landing. But certainly something a buyer might look at if they operate away from systems with a search and rescue system in place.

I am not arguing that point, in that Dead-Stick does not imply a hypersonic reentry and aerobraking... In this case it more of a question of what other emergency equipment said ship is equipped with.... Anyone for inflatable crash bags and one use deceleration thrusters for a survivable Litho-Braking maneuver?

my thought processes, were not flawed..I only forgot to explain some assumptions I made.

Unfortunately that is a sin that we all are guilty of.

FIrst
the vehicle in question would have to have the ability to maneuver without main drives. i assumed a starship would have the means to maneuver without it's main drives...that's a common sense precaution.

Well that all depends. I Think in the pre-reentry failure of Maneuver my concern would less about putting the ship down and more about establishing a stable orbit till I could rectify the situation.

Second
Ballistic entry capable ( more than just heat shielding and a streamlined form)would also include means of maneuvering the ship in atmosphere.

Would it? The vast majority of reentries in the real world had zero maneuver ability once they were committed to reentry...

Using reaction thrusters, or aerodynamic controls. If the feature was added to a design as a potential safety feature, some means of positive control would be included in the design.

If the ship has the aerofin option. it has plenty of control surface to work with. NASA lifting body designs had ridiculously small fins for stable flight. With any streamlined body, simple pop out panels to increase drag in one direction or another would be sufficient to allow for wide S-turns to burn energy and allow the pilot to maintain a safe flight speed.

as for entry speeds, I am assuming that a ship would be cruising at several hundred miles an hour during entry.

If you aren't burning off orbital velocities sub-sonic speeds are perfectly reasonable. (Think 1,100 kph or lower)

Mostly due to the fact I don't see anyone letting a starship descend straight down over a starport instead requiring them to enter atmosphere away for the port and then approach from some distance away.

well not after the first ship looses power during entry and landing dead center of the starport. a few million pounds of ship, cargo, fuel, and a fusion powerplant landing on the tarmac at terminal velocity would ruin your day...

but since most people don't enjoy drifting along like a blimp when they can go faster... I am going with the ships pushing a few hundred miles an our just to cut down on flight time.

Ok, this all depends on a lot of factors, especially what your down range looks like. 1st a little bit of science, the danger zone for reentry is the last 12 kilometers of altitude, entry into the troposphere, i.e. where all the weather is at. So the target, landing zone should probably have a large area for diversion into (A lot of SF has large chunks of desert as their primary starport). It really comes down to how you envision a Starport.

By the way from a near dead stop Felix Baumgartner hit nearly 850 mph in free fall from upper atmosphere. nothing to do with the discussion, but good lord supersonic without an airplane!!!

Whee!!!.....

 

[wbnc]

Your best bet, to survive something like this, would be to have an emergency anti-grav system (battery powered) that tries to arrest your fall at the last possible instant, possibly burning itself out in the process to get you down on the ground in hopefully a single piece.

a one shot Grav chute for starships...neat idea

 

[Condottiere]

Acme Corp Anti-Grav Buffer.

Opens up ten metres from solid surface, if activated ten seconds before impact.

Better results than Y. Lee Koyoteh Inc. impact airbag.

 

[wbnc]

I am not arguing that point, in that Dead-Stick does not imply a hypersonic reentry and aerobraking... In this case it more of a question of what other emergency equipment said ship is equipped with.... Anyone for inflatable crash bags and one use deceleration thrusters for a survivable Litho-Braking maneuver?

Ummm that would be my absolute last choice...right after grabbing a grav-chute and going out the door.

Well that all depends. I Think in the pre-reentry failure of Maneuver my concern would less about putting the ship down and more about establishing a stable orbit till I could rectify the situation.

well that is an option, but one that renders the entire discussion moot.

Would it? The vast majority of reentries in the real world had zero maneuver ability once they were committed to reentry...

quite simply because we use a capsule style spacecraft because they are cheaper and easier to design. the experiments in lifting bodies proved it was possible to build a functional non-capsule craft...just the flight control systems of the time weren't up to the task. And, capsules are just so much cheaper.

If you aren't burning off orbital velocities sub-sonic speeds are perfectly reasonable. (Think 1,100 kph or lower)

at much over 600 miles per hour you run into a huge issue with atmospheric friction...not enough to burn our ship to dust, but it is enough to make forcing your way past the tran-sonic barrier a pain....the air cant get out of the way if your craft isn't properly designed for supersonic flight. Buffeting, and a nasty bit of hull stress result. going supersonic wold just make the ride very uncomfortable without the hull being shaped to allow for smooth supersonic flight....which is why I went with entry speeds below 600 MPH.

Ok, this all depends on a lot of factors, especially what your down range looks like. 1st a little bit of science, the danger zone for reentry is the last 12 kilometers of altitude, entry into the troposphere, i.e. where all the weather is at. So the target, landing zone should probably have a large area for diversion into (A lot of SF has large chunks of desert as their primary starport). It really comes down to how you envision a Starport.

Oh very familiar wit the effects of weather on flying... those nasty little variations in atmosphere can make a short flight a study in ..."okay just don't throw up in the cockpit." had a Cesna I was in end up on its side due to a sudden gust hitting us in the middle of a bank once or twice.

its also where he air is thick enough to start causing real stress on the structure of any vessel. hitting that layer of air at high speeds is not as bad as hitting water...but as I mentioned earlier unless your ship is designed for high speed in atmo flight it's a pain.

as for starports..in my settings I always envisioned them well away from a city, or other area you don't want to experience the effects of a starship crash. Usually with many miles of open air or a nice solid mountain range as a buffer zone....if a nice broad dry lake would make sense that's where I put them.

Whee!!!.....

yeah, for a few minutes he got to feel like superman...

 

[Infojunky]

I am not arguing that point, in that Dead-Stick does not imply a hypersonic reentry and aerobraking... In this case it more of a question of what other emergency equipment said ship is equipped with.... Anyone for inflatable crash bags and one use deceleration thrusters for a survivable Litho-Braking maneuver?

Ummm that would be my absolute last choice...right after grabbing a grav-chute and going out the door.

The recent landing modes for the Mars Rovers amuse the heck out of me, as does the inflatable hypersonic disk....

If you aren't burning off orbital velocities sub-sonic speeds are perfectly reasonable. (Think 1,100 kph or lower)

at much over 600 miles per hour you run into a huge issue with atmospheric friction...not enough to burn our ship to dust, but it is enough to make forcing your way past the tran-sonic barrier a pain....the air cant get out of the way if your craft isn't properly designed for supersonic flight. Buffeting, and a nasty bit of hull stress result. going supersonic wold just make the ride very uncomfortable without the hull being shaped to allow for smooth supersonic flight....which is why I went with entry speeds below 600 MPH.

Note I used kilometers instead of either Knots or Miles....