Atmospheric Operations

[wbnc]

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

No, I did not ) my brain is hardwired for MPH, I have to stop and convert it, and don't always catch the Kph ....ugh....I use metric well enough, its just that translation step that hangs me up.

the new systems NASA has used make be wonder exactly what is in the tea at the office. The work, they are perfectly viable. Its just really off the wall thinking.

now if I remember right the Russians, who use land bound touch down points, have airbags on their re-entry capsules. I also know that some clever monkeys have been tinkering with personal airbags.

Now if I were building an escape pod, I'd have those airbags on the outside panels of the pod.

 

[Tenacious-Techhunter]

Anything larger/heavier than the most-recent Mars rovers is simply too much for airbags of current construction; the first generation of Mars rovers used parachutes before the drop, and the second had to add a reverse-JATO phase before the drop, because of the additional weight. So while you might get packages delivered from the starport that way (Take that, Amazon!), for spaceship landings, forget it... not without some ridiculously fantastic sci-fi material.

Streamlining does not improve maneuverability (agility); it improves top speed. A raindrop shape is not maneuverable; it is fast. If you want more agility, you need a lifting body; you should have to trade one level of streamlining for it; so you would buy up your streamlining, and then trade one level away for lifting body, which would give you an additional agility point.

The Fat Trader's "wings" do not provide lift; or, at least, they can't. If you don't want to believe me, try it in Kerbal. It just won't work. The reason is, the center of lift is way too far behind the center of mass. They're control surfaces for stable atmospheric flight only; they're fins on a dart; nothing more.

 

[wbnc]

Anything larger/heavier than the most-recent Mars rovers is simply too much for airbags of current construction; the first generation of Mars rovers used parachutes before the drop, and the second had to add a reverse-JATO phase before the drop, because of the additional weight. So while you might get packages delivered from the starport that way (Take that, Amazon!), for spaceship landings, forget it... not without some ridiculously fantastic sci-fi material.

Streamlining does not improve maneuverability (agility); it improves top speed. A raindrop shape is not maneuverable; it is fast. If you want more agility, you need a lifting body; you should have to trade one level of streamlining for it; so you would buy up your streamlining, and then trade one level away for lifting body, which would give you an additional agility point.

The Fat Trader's "wings" do not provide lift; or, at least, they can't. If you don't want to believe me, try it in Kerbal. It just won't work. The reason is, the center of lift is way too far behind the center of mass. They're control surfaces for stable atmospheric flight only; they're fins on a dart; nothing more.

Actually No....lifting froms don't give agility, ask the pilot of Shutle, or an, AN-225

I understand what you mean


The fat trader was drawn by an artist not an aerospace engineer. SO of course it doesn't fly right. But the basic idea of a delta winged , lifting-body freighter works ell enough..you just have to twea the wings positioning, shape....

 

[Infojunky]

Anything larger/heavier than the most-recent Mars rovers is simply too much for airbags of current construction; the first generation of Mars rovers used parachutes before the drop, and the second had to add a reverse-JATO phase before the drop, because of the additional weight. So while you might get packages delivered from the starport that way (Take that, Amazon!), for spaceship landings, forget it... not without some ridiculously fantastic sci-fi material.

Still the image of a Free Trader Lithobraking is too amusing for words... And the 2nd lander didn't litho break it abasaled to ground from a rocket frame, which is another cool visual in its own right.....

A raindrop shape is not maneuverable; it is fast.

Actually is a conical cross section that serves to shape the shock wave of plasma away from the skin of the craft during the hypersonic phase of Aerobraking,

 

[wbnc]

Yeah seeing a Trader bouncing along, as the crew ships dances on the bridge, would be cool...hilarious, ridiculous, but very cool.

 

[Tenacious-Techhunter]

A raindrop shape is not maneuverable; it is fast.

Actually is a conical cross section that serves to shape the shock wave of plasma away from the skin of the craft during the hypersonic phase of Aerobraking,

Well yes, but I was trying to write it approachably...

 

[Tenacious-Techhunter]

Actually No....lifting froms don't give agility, ask the pilot of Shutle, or an, AN-225

The ability of an aircraft to make yawing turns, what us players call "agility", is dependent on the lift the wings generate.


In my opinion, the Fat Trader can have either its iconic design, or lifting wings, but not both; I fall on the side of the art being canon, and not the stats, in this case.

 

[phavoc]

I wouldn't say the shuttle, or an AN-225 has agility. Agility means more than yawing back and forth. It also means you have an airframe that can take that sort of stress, plus enough power-to-mass ratio to put that zip-a-dee-do-dah back in your step after you bleed a lot of energy doing a agile maneuver. Even with gravitics once you kill your velocity in a gravity well you gotta build it back up again.

And anti-gravity doesn't mean you don't have to work against your own mass.

I don't see any issue with the Type R having wings, but in reality they wouldn't be there to provide much lift. More for artistic sake, and inefficient fuel storage.

 

[Tenacious-Techhunter]

AN225... Are you sure you don't mean the Buran, the "shuttle clone" the AN225 was carrying?

Typical Traveller firmly leaves the unpowered gliding regime behind. I don't think it has much relevance here. These ships traded excess speed for extra drag-inducing lift, which has no real value as a game mechanic. Of course, if you want to play "Traveller: Orbiter", there's a book for that... (If the GM decides to use orbital calculations, porkchop plots, and delta-v maps, let me know, I'm SO in...)

However, since we're not relying on unpowered flight, and we're not worried about extra lift, the only thing worth trading top-speed for is agility from drag-induced lift. The appropriate value of top-speed required in trade to achieve an extra point of agility is worth discussing.

You are right in that the airframe has to be strong enough to support this extra lift induced stress... but that's more of a TL and cost issue than a gameplay one; surely there's some material for which this is a suitable trade. And if not, aren't we then banishing all the wings?

Now, to make extra clear about lift providing additional agility, more lift is going to allow the ship to turn in a tighter turning radius. Which sounds like extra agility to me.


With regards to the Fat Trader, considered from a purely technical standpoint, those fins are there purely for atmospheric stability, and nothing more.

 

[wbnc]

AN225... Are you sure you don't mean the Buran, the "shuttle clone" the AN225 was carrying?

I did some checking the An-225, Airbus Beluga, and a couple other over sized cargo planes actually fall in the tonnage range of a starship. And fly pretty well, the Beluga is a twin engine, which can push .8 mach....Not bad at all.

The An-225 would be roughly the size of 200 ton starship if my math holds. and she can carry 100dt of cargo....however; her wings seem to take up a big portion of her anatomy. since the fuselage is around 140-160 Dtons...the tapered shape makes it hard to figure tonnage based on listed specs.

 

[phavoc]

AN225... Are you sure you don't mean the Buran, the "shuttle clone" the AN225 was carrying?

Typical Traveller firmly leaves the unpowered gliding regime behind. I don't think it has much relevance here. These ships traded excess speed for extra drag-inducing lift, which has no real value as a game mechanic. Of course, if you want to play "Traveller: Orbiter", there's a book for that... (If the GM decides to use orbital calculations, porkchop plots, and delta-v maps, let me know, I'm SO in...)

However, since we're not relying on unpowered flight, and we're not worried about extra lift, the only thing worth trading top-speed for is agility from drag-induced lift. The appropriate value of top-speed required in trade to achieve an extra point of agility is worth discussing.

You are right in that the airframe has to be strong enough to support this extra lift induced stress... but that's more of a TL and cost issue than a gameplay one; surely there's some material for which this is a suitable trade. And if not, aren't we then banishing all the wings?

Now, to make extra clear about lift providing additional agility, more lift is going to allow the ship to turn in a tighter turning radius. Which sounds like extra agility to me.


With regards to the Fat Trader, considered from a purely technical standpoint, those fins are there purely for atmospheric stability, and nothing more.

No, the AN-225 aircraft itself. All of the heavy lifters (aircraft) are rather ungainly. Much like a supertanker takes miles to stop or turn around). It CAN, but it's ungainly and certainly not agile. Moving on with the nautical equivalent, ships equipped with drive pods are capable of more agile maneuvers than those with only rudders. However due to their size and bulk they will never be considered agile - not like say a fighter aircraft that has true agility due to its size and outsized thrust-to-weight ratio.

A starship, with it's crystal-iron, or even collapsed matter hull, is just too heavy to even consider the existing wings to provide any real lift. At most they could help to provide additional control surfaces, but with anti-grav there's no real need. And they would be too massive in a gravity well to do much agility - at least as we consider real-world agility. Being able to ignore lift if a HUGE benefit, yet the other remaining factors still must be considered to 'dance' in the air.

 

[Tenacious-Techhunter]

No, the AN-225 aircraft itself. All of the heavy lifters (aircraft) are rather ungainly. Much like a supertanker takes miles to stop or turn around). It CAN, but it's ungainly and certainly not agile. Moving on with the nautical equivalent, ships equipped with drive pods are capable of more agile maneuvers than those with only rudders. However due to their size and bulk they will never be considered agile - not like say a fighter aircraft that has true agility due to its size and outsized thrust-to-weight ratio.

A starship, with it's crystal-iron, or even collapsed matter hull, is just too heavy to even consider the existing wings to provide any real lift. At most they could help to provide additional control surfaces, but with anti-grav there's no real need. And they would be too massive in a gravity well to do much agility - at least as we consider real-world agility. Being able to ignore lift if a HUGE benefit, yet the other remaining factors still must be considered to 'dance' in the air.

Yes, but that's not a lifting body aircraft, which is what we were discussing. Further, that is a craft for which cargo capacity and efficiency were the key design criteria, and not atmospheric maneuverability. It may be the right size, but it was not designed to the relevant constraints. And I was not making the point that a lifting-body aircraft would be agile; just that it would be more agile than an otherwise identical craft, but at the cost of top-speed. Whether it could be agile enough to earn an additional point is a subject worthy of debate.

Drive pods only have to be powerful in proportion to the drag of the craft they are trying to propel. Look at modern tugboats for an example of how a drivepod approach has made them insanely maneuverable craft. If those pods were scaled up to the drag of a cruise ship and installed, that cruise ship would be just as maneuverable; no longer fit to be a cruise ship, but just as maneuverable.

Realistically speaking, a small ship in atmosphere with a high level of streamlining of Thrust 6 will have a higher top-speed than a larger ship with the same degree of streamlining work which also had Thrust 6; because while the coefficient of drag is the same, the aerodynamic profile area is larger. At the speed at which the larger ship tops-out, the smaller ship will only be more maneuverable because it has leftover thrust. However, as a gameplay mechanic, this is lousy. It would be better to scale the cost of streamlining by the square of the cube-root of the displacement, and then make those two ships perform the same, because their numbers are the same. However, if, instead of streamlining that ship, you give it Thrust 9, then it has extra thrust to maneuver with, and tighten its turns, and power through the drag like a muscle-car. The larger ship then can be faster, so long as the ship is not so much bigger that the drag can't be beaten.

Wings do not provide control surfaces; control surfaces provide control surfaces. Wings can provide bulk lift, which can help in tightening turns. But a lifting body would be more efficient and more relevant, given the sizes involved.

 

[phavoc]

Yes, but that's not a lifting body aircraft, which is what we were discussing. Further, that is a craft for which cargo capacity and efficiency were the key design criteria, and not atmospheric maneuverability. It may be the right size, but it was not designed to the relevant constraints. And I was not making the point that a lifting-body aircraft would be agile; just that it would be more agile than an otherwise identical craft, but at the cost of top-speed. Whether it could be agile enough to earn an additional point is a subject worthy of debate.

We have no operational craft of that sort. The shuttle is essentially a standard aircraft on steroids, but with no real ability to do anything that we are discussing other than land. Maneuvers are designed to bleed energy to get it down to a reasonable speed in order to land. But it does no maneuvering such as climbing, as it can't - or at least not for very long or very high.

Traveller-craft aren't quite in the same boat as they have no need for lift. That is already there via their anti-grav. So then it becomes a question of is the craft capable of, agility wise. I think one issue here is that we haven't defined what is meant by agility. In an atmosphere you can use resistance in ways you cannot in space (i.e. if you thrust left, you will continue to do so until you counter your thrust or you are affected by another gravity field). So there are maneuvers possible in-atmo that you could never really do in space, or at least not without a great deal of constanly counter-thrust.

The larger/heavier the craft (air or space), the more energy is required to make it change direction. And the larger the mass, the slower the reaction is going to be. Having an atmosphere to react against can help, or hinder, your movements. And having a more aerodynamic shape means less resistance, thus you will be faster on the movement than a non-aerodynamic one. There is going to be a point where applying more power to overcome the issue is not going to work anymore.

A second issue in our discussion is one of scale. Ships of the 100-200Dton displacement would be able to do much more than say a 10,000dton behemoth, or even a 5,000dton one. So sure, craft of a smaller size are going to be capable of doing lots more and being more agile - regardless of their type.

Drive pods only have to be powerful in proportion to the drag of the craft they are trying to propel. Look at modern tugboats for an example of how a drivepod approach has made them insanely maneuverable craft. If those pods were scaled up to the drag of a cruise ship and installed, that cruise ship would be just as maneuverable; no longer fit to be a cruise ship, but just as maneuverable.

Actually cruise ships today utilize drive pods now. I witnessed a 80,000 ton cruise ship do a 180 in front of me and then dock itself. It took less than 10 minutes. It was faster than having tugs do it. Newer cruise ships all have drive pods because it allows them greater flexibility in docking. I don't know if it's more efficient than a standard set of screws, but man are they capable of some tight turns.

Realistically speaking, a small ship in atmosphere with a high level of streamlining of Thrust 6 will have a higher top-speed than a larger ship with the same degree of streamlining work which also had Thrust 6; because while the coefficient of drag is the same, the aerodynamic profile area is larger. At the speed at which the larger ship tops-out, the smaller ship will only be more maneuverable because it has leftover thrust. However, as a gameplay mechanic, this is lousy. It would be better to scale the cost of streamlining by the square of the cube-root of the displacement, and then make those two ships perform the same, because their numbers are the same. However, if, instead of streamlining that ship, you give it Thrust 9, then it has extra thrust to maneuver with, and tighten its turns, and power through the drag like a muscle-car. The larger ship then can be faster, so long as the ship is not so much bigger that the drag can't be beaten.

I agree with your analysis. Breaking that down into simpler gameplay mechanics might be rough because of the wild variance you can get in ship designs. I think I would prefer keeping costs the same but providing better performance to the more streamlined ship. That 'feels' more right to me.

Wings do not provide control surfaces; control surfaces provide control surfaces. Wings can provide bulk lift, which can help in tightening turns. But a lifting body would be more efficient and more relevant, given the sizes involved.

True, but that's a bit of a quibble isn't it? Control surfaces require wings in order to be properly positioned to work in the first place. Without wings flaps can't exist. Without wings you can't have aerilons. Just like without tails you can't have rudders. Even the experimental lifting body aircraft designed and flown by NASA have standard tails and rudders. They also have other control surfaces, but not wing-based ones since they don't have any. Plus they require more power to generate lift. That's a benefit of wings in that you can use less power (over pure lifting bodies). The Blended wing approach seems to take the best of both worlds. Course we still need to build them and get more knowledge behind their operation to better determine if it's the way to go or not. Orbital Sciences proposed a blended lifting body style for their Promethesus shuttle.

There's always going to be a trade-off somewhere.

 

[Tenacious-Techhunter]

We have no operational craft of that sort.

Here's one you can build at home: https://en.wikipedia.org/wiki/Wainfan_Facetmobile

Do not mistake our declining to put such craft into production as some sort of inability to do so. The difference has more to do with NASA type stodginess of preferring to use craft with a proven track record, or optimizing other alternative criteria, like top-speed. A "tennis-ball can with wings" is always going to be faster than a Lifting Body; just not as efficient. For something like a starship, where efficient use of volume and having a reduced targeting profile presented to the enemy is a predominant factor, a Lifting Body design is the proper approach, when lift or agility is preferred over pure speed.

I think one issue here is that we haven't defined what is meant by agility.

Agility is the ability to turn in a tighter circle. To do that, you need additional force perpendicular to the Velocity; this means either lift, or thrust. This is how lift contributes to agility, and can be substituted for thrust, when available. Control surfaces are just a means by which to change which direction this perpendicular direction is.

The larger/heavier the craft (air or space), the more energy is required to make it change direction. And the larger the mass, the slower the reaction is going to be. Having an atmosphere to react against can help, or hinder, your movements. And having a more aerodynamic shape means less resistance, thus you will be faster on the movement than a non-aerodynamic one. There is going to be a point where applying more power to overcome the issue is not going to work anymore.

A second issue in our discussion is one of scale. Ships of the 100-200Dton displacement would be able to do much more than say a 10,000dton behemoth, or even a 5,000dton one. So sure, craft of a smaller size are going to be capable of doing lots more and being more agile - regardless of their type.

Difference in mass is predominantly covered by how much Thrust is produced by a maneuver drive installed in a given size hull. So as long as spare Thrust is available, so is that much agility.

Drive pods only have to be powerful in proportion to the drag of the craft they are trying to propel. Look at modern tugboats for an example of how a drivepod approach has made them insanely maneuverable craft. If those pods were scaled up to the drag of a cruise ship and installed, that cruise ship would be just as maneuverable; no longer fit to be a cruise ship, but just as maneuverable.

Actually cruise ships today utilize drive pods now. I witnessed a 80,000 ton cruise ship do a 180 in front of me and then dock itself. It took less than 10 minutes. It was faster than having tugs do it. Newer cruise ships all have drive pods because it allows them greater flexibility in docking. I don't know if it's more efficient than a standard set of screws, but man are they capable of some tight turns.

You missed my point here. My point was, if the Cruise Ship had the same proportional thrust to drag as the tugboat, it would maneuver identically to the tugboat, in spite of its size.

I agree with your analysis. Breaking that down into simpler gameplay mechanics might be rough because of the wild variance you can get in ship designs. I think I would prefer keeping costs the same but providing better performance to the more streamlined ship. That 'feels' more right to me.

It's not the streamlining that's different; it's the size. The coefficient of drag can be the same, but the cross-sectional area is larger. Unless we get a chart showing ship size and top speed, it makes more sense to bake that into the hull costs.

True, but that's a bit of a quibble isn't it? ... Just like without tails you can't have rudders.

Using correct terminology is sort of a prerequisite to having a meaningful discussion. In the technical sense, the fins that the elevators and the rudders are on are not wings.

Plus they require more power to generate lift. That's a benefit of wings in that you can use less power (over pure lifting bodies). The Blended wing approach seems to take the best of both worlds. Course we still need to build them and get more knowledge behind their operation to better determine if it's the way to go or not.

Go back and read my "power vs. thrust" statement. While not strictly wrong, it's a misunderstanding you have to correct. "Power" is generally not relevant to the discussion here, and I recommend against you using it.

Additionally, it's not "thrust" that provides the additional lift; it's speed. You need more thrust to counter the drag at the additional speed required to get the same lift.

Orbital Sciences proposed a blended lifting body style for their Promethesus shuttle.

The modern version is Sierra Nevada Corporation's Dreamchaser. This one will fly: http://www.sncorp.com/BusinessAreas/SpaceSystems

 

[phavoc]

Here's one you can build at home: https://en.wikipedia.org/wiki/Wainfan_Facetmobile

Do not mistake our declining to put such craft into production as some sort of inability to do so. The difference has more to do with NASA type stodginess of preferring to use craft with a proven track record, or optimizing other alternative criteria, like top-speed. A "tennis-ball can with wings" is always going to be faster than a Lifting Body; just not as efficient. For something like a starship, where efficient use of volume and having a reduced targeting profile presented to the enemy is a predominant factor, a Lifting Body design is the proper approach, when lift or agility is preferred over pure speed.

I didn't make the mistake. But you'll notice that nobody has, right?

Agility is the ability to turn in a tighter circle. To do that, you need additional force perpendicular to the Velocity; this means either lift, or thrust. This is how lift contributes to agility, and can be substituted for thrust, when available. Control surfaces are just a means by which to change which direction this perpendicular direction is.

I would define agility as the ability to move out of the way of incoming fire, or make it damn difficult to shoot you. The only reason to have agility is to either show off or to make it harder to hit you. A free trader takes off via lift, and then uses thrust to more quickly reach orbit. It cannot take off on thrust alone. And while it can eventually reach orbit on lift alone, it is a combination of the two that gets it there speedily.

Difference in mass is predominantly covered by how much Thrust is produced by a maneuver drive installed in a given size hull. So as long as spare Thrust is available, so is that much agility.

You missed my point here. My point was, if the Cruise Ship had the same proportional thrust to drag as the tugboat, it would maneuver identically to the tugboat, in spite of its size.

I'm not sure it would in reality. I see where you are going with your point, but I'm not sure if you actually built something like that it would react the same way. Just because you can build something at 1/100th scale doesn't mean it works the exact same way at 1/1 scale. That's been proven time and again with many forms of models. It's an interesting thought though, and I would really like to see that in action. I think it would be pretty neat to watch.

It's not the streamlining that's different; it's the size. The coefficient of drag can be the same, but the cross-sectional area is larger. Unless we get a chart showing ship size and top speed, it makes more sense to bake that into the hull costs.

Yeah, I don't see that ever happening. From a gaming perspective it would be tough to design a chart like that because ship configurations are all over the board (yay!) based upon personal and racial design preferences. That's a good thing from a gaming point of view. I'm not sure there would be a lot of useful gaming use here. I don't want to slide too far back into MegaTraveller design processes. The designing got to be more of a chore than a joy.

Using correct terminology is sort of a prerequisite to having a meaningful discussion. In the technical sense, the fins that the elevators and the rudders are on are not wings.

This isn't an aeronautical engineering forum, and I'm not a licensed aerospace engineer. Generalized terms seem appropriate to the space.

Additionally, it's not "thrust" that provides the additional lift; it's speed. You need more thrust to counter the drag at the additional speed required to get the same lift.

Not in a universe populated by gravitics. Speed, generally speaking, provides no lift. That's what gravitics are used for.

The modern version is Sierra Nevada Corporation's Dreamchaser. This one will fly: http://www.sncorp.com/BusinessAreas/SpaceSystems

I hope it does. Only time will tell though. Others have tried, and failed.

 

[Tenacious-Techhunter]

Here's one you can build at home: https://en.wikipedia.org/wiki/Wainfan_Facetmobile

Do not mistake our declining to put such craft into production as some sort of inability to do so.

I didn't make the mistake. But you'll notice that nobody has, right?

This is primarily a function of design requirements, but also a function of relying on what is perceived as "tried and true" design.

Agility is the ability to turn in a tighter circle. To do that, you need additional force perpendicular to the Velocity; this means either lift, or thrust. This is how lift contributes to agility, and can be substituted for thrust, when available. Control surfaces are just a means by which to change which direction this perpendicular direction is.

I would define agility as the ability to move out of the way of incoming fire, or make it damn difficult to shoot you. The only reason to have agility is to either show off or to make it harder to hit you. A free trader takes off via lift, and then uses thrust to more quickly reach orbit. It cannot take off on thrust alone. And while it can eventually reach orbit on lift alone, it is a combination of the two that gets it there speedily.

As I said, Agility is a measure of how much force you can apply perpendicular to the velocity. It doesn't matter whether you're turning or sideslipping, as you apparently prefer. And no, dodging isn't the only benefit of agility; the other is bringing your guns to bear on your target, and being able to get the shot in the first place. Attempting to bring your guns to bear on your target is a contest of agility. If you win, you hit. If you fail, you miss. The craft with the tighter turning circle wins. See the "Scissors" circumstance in advanced combat maneuvers, and you will quickly understand the importance of having a superior ability to turn on combat: https://en.wikipedia.org/wiki/The_Scissors

Difference in mass is predominantly covered by how much Thrust is produced by a maneuver drive installed in a given size hull. So as long as spare Thrust is available, so is that much agility.

You missed my point here. My point was, if the Cruise Ship had the same proportional thrust to drag as the tugboat, it would maneuver identically to the tugboat, in spite of its size.

I'm not sure it would in reality. I see where you are going with your point, but I'm not sure if you actually built something like that it would react the same way. Just because you can build something at 1/100th scale doesn't mean it works the exact same way at 1/1 scale. That's been proven time and again with many forms of models. It's an interesting thought though, and I would really like to see that in action. I think it would be pretty neat to watch.

I was neglecting a few things like the Reynolds number, which has some significance. I was also neglecting mass, but we were talking about Traveller thrust, not actual thrust, since we're talking about Traveller, and Thrust is a function of the maneuver drive and the displacement of the ship. But, within those bounds, what I said was entirely correct, whether you believe it or not. I said that to make a point, however, and that point is still valid; the things you describe in nebulous terms are accountable, whether you know how to account for them or not. And, because they are, it's possible to make definitive statements about how craft would operate relative to one another, if you know how to account for them. So please be more careful in doing so.

It's not the streamlining that's different; it's the size. The coefficient of drag can be the same, but the cross-sectional area is larger. Unless we get a chart showing ship size and top speed, it makes more sense to bake that into the hull costs.

Yeah, I don't see that ever happening. From a gaming perspective it would be tough to design a chart like that because ship configurations are all over the board (yay!) based upon personal and racial design preferences. That's a good thing from a gaming point of view. I'm not sure there would be a lot of useful gaming use here. I don't want to slide too far back into MegaTraveller design processes. The designing got to be more of a chore than a joy.

That's why I'm advocating that it be a function of raw displacement, rather than something more strict, like cross-section.

Using correct terminology is sort of a prerequisite to having a meaningful discussion. In the technical sense, the fins that the elevators and the rudders are on are not wings.

This isn't an aeronautical engineering forum, and I'm not a licensed aerospace engineer. Generalized terms seem appropriate to the space.

Appropriate to the space, yes; appropriate to the question and the discussion that has arisen from it, no. It's important that the discussion remain coherent.

Additionally, it's not "thrust" that provides the additional lift; it's speed. You need more thrust to counter the drag at the additional speed required to get the same lift.

Not in a universe populated by gravitics. Speed, generally speaking, provides no lift. That's what gravitics are used for.

You lost track of what this was in response to; this was in response to your statement about a lifting body needing more "power" to achieve the same lift. Gravitics weren't relevant to that point. You can supplement the force lift provides with gravitics, but the lift itself will be the same for any given speed, supplemented or not.

The modern version is Sierra Nevada Corporation's Dreamchaser. This one will fly: http://www.sncorp.com/BusinessAreas/SpaceSystems

I hope it does. Only time will tell though. Others have tried, and failed.

Yeah, we'll know tomorrow if they win the cargo contract.

 

[phavoc]

As I said, Agility is a measure of how much force you can apply perpendicular to the velocity. It doesn't matter whether you're turning or sideslipping, as you apparently prefer. And no, dodging isn't the only benefit of agility; the other is bringing your guns to bear on your target, and being able to get the shot in the first place. Attempting to bring your guns to bear on your target is a contest of agility. If you win, you hit. If you fail, you miss. The craft with the tighter turning circle wins. See the "Scissors" circumstance in advanced combat maneuvers, and you will quickly understand the importance of having a superior ability to turn on combat: https://en.wikipedia.org/wiki/The_Scissors

Standard aerial combat maneuvers aren't really applicable in the Traveller grav-powered universe. You have no need of lift from thrust. You can move in (nearly) any direction by adjusting your gravitics. You still have to counter your directional thrust though, at least or until friction in the atmosphere does it for you. I saw a recent video of a Russian aircraft that did a literal 180 in the sky without changing altitude. Of course this was done at a lower speed, but it showed off some impressive handling characteristics. Had it been a grav craft, instead of doing just the 180 it could have shot up/down/at an angle. Turning circles only matter when you require thrust for lift. Otherwise you can toss that out the window and maneuver to the extent your vehicle is capable of handling the stress as well as the physics of your movement.

I agree that being able to bring your weapons to bear on a target is also a good use of agility. Though most spacecraft use turrets, and some small craft do as well, so offensively it could be less of an issue, depending on the craft in question.

I was neglecting a few things like the Reynolds number, which has some significance. I was also neglecting mass, but we were talking about Traveller thrust, not actual thrust, since we're talking about Traveller, and Thrust is a function of the maneuver drive and the displacement of the ship. But, within those bounds, what I said was entirely correct, whether you believe it or not. I said that to make a point, however, and that point is still valid; the things you describe in nebulous terms are accountable, whether you know how to account for them or not. And, because they are, it's possible to make definitive statements about how craft would operate relative to one another, if you know how to account for them. So please be more careful in doing so.

I don't usually tend to bring up equations in gaming conversations, at least not ones that deal with fluid modeling (aka aerodynamics). I still hold true to the idea if you had a cube-shaped craft and an aerodynamic shaped craft the aerodynamic one would be more maneuverable in an atmosphere. The cube-shaped one would have to devote so much power to offset the aerodynamics that it would no longer be viable as a useful or economic craft. I wasn't trying to min/max the question here. I was trying to stay within the realm of what someone would actually build. And even then it still becomes a question of can you actually put enough power out of the vehicle in question while still remaining within the displacement of the vehicle.

That's why I'm advocating that it be a function of raw displacement, rather than something more strict, like cross-section.

I think it would have to be along the lines of 'types' of hulls, with a lot of generalization tossed in there. Should a 10,000 ton streamlined ship be faster than a 10,000 ton sphere, or standard hull ship within an atmosphere? It seems regardless of what path is taken there are issues with the modeling of it due to the nature of the topic (i.e. a game).

You lost track of what this was in response to; this was in response to your statement about a lifting body needing more "power" to achieve the same lift. Gravitics weren't relevant to that point. You can supplement the force lift provides with gravitics, but the lift itself will be the same for any given speed, supplemented or not.

But in an atmosphere lift can only be generated by speed (or the application of thrust to generate the said speed). That's what I was saying. When you put gravitics in the mix you no longer need thrust to generate lift. No lifting body is going to lift off without thrust. And that's the point - when you can sidestep the requirement for thrust to generate lift you fundamentally change all of your concepts and requirements.

Yeah, we'll know tomorrow if they win the cargo contract[/url].

Let's hope so. We need more industry in this sector that can deliver payloads to orbit in order to bring down the cost of access.

 

[Tenacious-Techhunter]

Standard aerial combat maneuvers aren't really applicable in the Traveller grav-powered universe. You have no need of lift from thrust. You can move in (nearly) any direction by adjusting your gravitics. ... Turning circles only matter when you require thrust for lift. Otherwise you can toss that out the window and maneuver to the extent your vehicle is capable of handling the stress as well as the physics of your movement.

Turning circles matter any time you want to change your trajectory, which is important for dodging fire. The source of the Thrust is irrelevant; it's the Thrust that does the job. The scissors example is a tactical situation in which there are very few alternatives but to continue the scissors, because most other alternatives are worse; but it's a delaying tactic at best, because the more maneuverable aircraft always wins; the repetition simply favors the more maneuverable craft. This is all due to turning radius at a given velocity, which is a function of Thrust. You may claim this maneuver isn't relevant in space, but it is, particularly for single-turret craft like a Type S Scout; the "rolling scissors" is the best option a Type S Scout has for keeping his target within the turret arc, particularly when the dogfighter wants to exploit his massive ventral blindspot.

I agree that being able to bring your weapons to bear on a target is also a good use of agility. Though most spacecraft use turrets, and some small craft do as well, so offensively it could be less of an issue, depending on the craft in question.

For dogfighters and single turret ships, the ability to bring guns to bear on the opponent has tight constraints. And those constraints don't go away until ships have at least 4 turrets.

I don't usually tend to bring up equations in gaming conversations, at least not ones that deal with fluid modeling (aka aerodynamics). I still hold true to the idea if you had a cube-shaped craft and an aerodynamic shaped craft the aerodynamic one would be more maneuverable in an atmosphere. The cube-shaped one would have to devote so much power to offset the aerodynamics that it would no longer be viable as a useful or economic craft. I wasn't trying to min/max the question here. I was trying to stay within the realm of what someone would actually build. And even then it still becomes a question of can you actually put enough power out of the vehicle in question while still remaining within the displacement of the vehicle.

If the cubed one had more Thrust at the same speed, it would be more maneuverable. However, if the spherical one had the same Thrust, the cubed one would lose; there's a very subtle tipping-point between the integer value Yhrust values where just a little more Thrust on the cubed ship would make it only equal to the sphere, but a full +1 Thrust blows that out of the water. Aerodynamics can be beaten by thrust alone; that's what you're seeing when you see those vectored thrust aircraft so popular in Europe these days; they have so much thrust applied in the right directions that the aerodynamics no longer matter. The difference is that this is sub-optimal; better aerodynamics are more efficient. However, more efficiency is not always an option. It's perfectly feasible to have a race with TL12 engines and TL9 streamlining. With a war on, their ships will be very "cube"y, because they are easier to manufacture with what they know; and cost-efficiency is better strategy in a war.

I think it would have to be along the lines of 'types' of hulls, with a lot of generalization tossed in there. Should a 10,000 ton streamlined ship be faster than a 10,000 ton sphere, or standard hull ship within an atmosphere? It seems regardless of what path is taken there are issues with the modeling of it due to the nature of the topic (i.e. a game).

So long as the math has been pre-calculated in a handy chart, no one will have reason to question it. But a chart that models the circumstances better is more useful, because it doesn't have to be corrected after-the-fact. You can certainly start trimming entries above a certain level of absurdity, of course. The important point though is that the cost function should be correct.

But in an atmosphere lift can only be generated by speed (or the application of thrust to generate the said speed). That's what I was saying. When you put gravitics in the mix you no longer need thrust to generate lift. No lifting body is going to lift off without thrust. And that's the point - when you can sidestep the requirement for thrust to generate lift you fundamentally change all of your concepts and requirements.

Gravitics are just another source of Thrust. Lift is Thrust as a function of speed. Thrust is Thrust; the source is irrelevant.

Yeah, we'll know tomorrow if they win the cargo contract[/url].

Let's hope so. We need more industry in this sector that can deliver payloads to orbit in order to bring down the cost of access.

Finally, we agree on something; go us! XD

My point, of course, was that the technology is entirely fieldable; we just need an appropriately optimal use-case to justify using it.

 

[phavoc]

Agreement... yay us!

I think we've beaten most of this argument to death. It was interesting but I don't see either of us budging much from our stated positions. And that's ok, it's not a necessity nor a requirement.

Let's hope we DO see more space industry!!