Optimizing for Both Atmosphere and Space

[darthbob88]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

If particle shields work the way I think they do, though, it should be quite easy to design a craft for air and space combat. Assuming that particle shields act, so far as particles are concerned, something like physical armor, then you could design a craft with all the bits and pieces you want, then configure the particle shield to form an aerodynamic envelope around the craft. I'd include a picture, but I fail at t3h Photoshop.

For convenience in disproving this, this hypothesis is based on the assumptions that:
1) Particle shielding deflects particles in the same manner as more solid armor does,
2) That particle shielding may be placed at an arbitrary distance from its emitters, and
3) That space superiority requires that a spacecraft have bits and pieces tacked on which leave the craft less aerodynamic than a brick.

[Covenant]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

If particle shields work the way I think they do, though, it should be quite easy to design a craft for air and space combat. Assuming that particle shields act, so far as particles are concerned, something like physical armor, then you could design a craft with all the bits and pieces you want, then configure the particle shield to form an aerodynamic envelope around the craft. I'd include a picture, but I fail at t3h Photoshop.

For convenience in disproving this, this hypothesis is based on the assumptions that:
1) Particle shielding deflects particles in the same manner as more solid armor does,
2) That particle shielding may be placed at an arbitrary distance from its emitters, and
3) That space superiority requires that a spacecraft have bits and pieces tacked on which leave the craft less aerodynamic than a brick.

There's no reason why it HAS to be this way. You could always force an Aerodynamic shape if you're willing to waste space on a curved shell around the thing to act as an airfoil. If you're talking about maximum efficency for air AND space, yeah, that's not gonna happen--but that's because they are two very different environments. It's not even necessary to create a particle shield to do this. There's a lot of ugly, unatmospheric parts of a spaceship that are not great for air travel, but you can always just stick a piece of hull around it so the air never touches it. Again, you're trading one kind of efficency for another, but it has to do with what your goals are.

[GrandMasterTerwynn]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

Yes, you're right. A combat spacecraft would require space for radiators, to shed waste heat from internal systems, hardpoints for lasers, attitude control thrusters, and a great deal of internal mass devoted to propulsion. A combat aircraft doesn't have any need for thrusters like that, or the kind of radiators you need in vacuum. It also doesn't need as much propellant nor as beefy an engine as a spacecraft, since the aircraft only needs enough power to generate sufficient forward thrust for its wings to develop lift. As a result, it helps for the aircraft to be light and aerodynamic.

If particle shields work the way I think they do, though, it should be quite easy to design a craft for air and space combat. Assuming that particle shields act, so far as particles are concerned, something like physical armor, then you could design a craft with all the bits and pieces you want, then configure the particle shield to form an aerodynamic envelope around the craft. I'd include a picture, but I fail at t3h Photoshop.

In hardcore sci-fi, they don't work at all. Sure, you might create one using some sort of fine EM control and plasma manipulation in a hard high-tech sci-fi, but such a shield would likely be hopelessly disrupted by the solid wall of particles slamming into it at all angles known as the atmosphere. (Though there is the thought of ionizing the air in front of you, and pulling it along the shield boundaries in a sort of teardrop shape, but I imagine that's probably not as much control as you'd like.)

In most any other scenario, you could pretty much make the shields work in any way you wish. In that case, you'd focus more on the effects and not bore the reader, or invite them to spot glaring weaknesses in your logic by a tedious exposition of the means.

[andrewgpaul]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

Yes, you're right. A combat spacecraft would require space for radiators, to shed waste heat from internal systems, hardpoints for lasers, attitude control thrusters, and a great deal of internal mass devoted to propulsion. A combat aircraft doesn't have any need for thrusters like that, or the kind of radiators you need in vacuum. It also doesn't need as much propellant nor as beefy an engine as a spacecraft, since the aircraft only needs enough power to generate sufficient forward thrust for its wings to develop lift. As a result, it helps for the aircraft to be light and aerodynamic.

Actually, I'd think a space fighter would need a less beefy engine than the aircraft; for precisely the reason that to attain the same forward acceleration, it's not having to also generate lift, or overcome drag.

I'm sure an engineer will be along shortly to correct any misconceptions

But yeah, I doubt that a fighter designed to operate in both atmosphere and space will get soundly beaten by a vehicle designed to operate in only one medium (all things being equal of course; Centauri Sentris could outfly EA Starfuries, despite the latter being a space-only fighter, but the Centauri had centuries of development on the EA)

Star Wars seems to get away with it by 'cheating'; the starfighters use repulsorlifts for lift, and possibly their shields aid in streamlining. Even then, X-Wings can out-turn TIE Fighters, because they don't have a massive radiator providing air resistance.

(all that's from reading X-Wing and Rogue Squadron novels, right enough, and I don't know if there's even an atmosphere-only fighter in the canon to compare it with).

[Darth Yoshi]

There are plenty. The cloud car, IIRC, operates at altitudes greater than a repulsor can typically handle using a space-worthy drive. Same with the v-wing.

[andrewgpaul]

Isn't the V-wing a starfighter?

[Bounty]

Isn't the V-wing a starfighter?

The other V-wing.

[Darth Yoshi]

Not the one in Dark Empire.

[Batman]

Isn't the V-wing a starfighter?

I ran afoul of that that myself. It's both (and a civilian transport, to boot). That designator was used for an OR spacefighter and a NR combat airspeeder (from DE, if memory serves).

Actually, I'd think a space fighter would need a less beefy engine than the aircraft; for precisely the reason that to attain the same forward acceleration, it's not having to also generate lift, or overcome drag.

As long as you don't want to operate from inside a gravity well that might work, except UNlike the aircraft, you have to take your reaction mass right along with you which is going to up your tonnage quite a bit so even for the paltry 1.5 or so gs of linear accelleration a jetfighter is capable of, you DO need quite a beefier engine.
Plus even with torchship-stxle constant thrust halfway turnover courses, you'll take your own sweet time going places. We're talking 3.7 hours for a measly 100 k-klicks, not exactly interplanetary distances...

[GrandMasterTerwynn]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

Yes, you're right. A combat spacecraft would require space for radiators, to shed waste heat from internal systems, hardpoints for lasers, attitude control thrusters, and a great deal of internal mass devoted to propulsion. A combat aircraft doesn't have any need for thrusters like that, or the kind of radiators you need in vacuum. It also doesn't need as much propellant nor as beefy an engine as a spacecraft, since the aircraft only needs enough power to generate sufficient forward thrust for its wings to develop lift. As a result, it helps for the aircraft to be light and aerodynamic.

Actually, I'd think a space fighter would need a less beefy engine than the aircraft; for precisely the reason that to attain the same forward acceleration, it's not having to also generate lift, or overcome drag.

Well, you could stick an arbitrarily weak main engine on a spacecraft, but it will generate arbitrarily miniscule thrust. Sure you'll still get to the same final velocity, but you're going to take a really, really long time to do it. Ergo, a spacecraft with higher performance on the helm must have more powerful engines that consume more fuel, generate more waste heat, etc.

But yeah, I doubt that a fighter designed to operate in both atmosphere and space will get soundly beaten by a vehicle designed to operate in only one medium (all things being equal of course; Centauri Sentris could outfly EA Starfuries, despite the latter being a space-only fighter, but the Centauri had centuries of development on the EA)

Of course. Both are almost mutually exclusive design paradigms. You could stick a heat shield on the belly of a troop or equipment dropcraft, send it plunging through the atmosphere, and have it land VTOL using its main engines, but an agile air-superiority fighter it will never be. On the same token, you could stick motors powerful enough to accelerate an aircraft to orbital velocites, and bolt in an RCS system to maneuvering in vacuum, and add heat-shielding and cooling systems to enable it to come back again, but all those add mass to the fighter, making it less nimble in the air, and leaving less mass/space left over for weapons.

Star Wars seems to get away with it by 'cheating'; the starfighters use repulsorlifts for lift, and possibly their shields aid in streamlining. Even then, X-Wings can out-turn TIE Fighters, because they don't have a massive radiator providing air resistance.

Yes, Star Wars gets away with it because they have CoM-defying magical wank-tech.

[andrewgpaul]

Yes, you're right. A combat spacecraft would require space for radiators, to shed waste heat from internal systems, hardpoints for lasers, attitude control thrusters, and a great deal of internal mass devoted to propulsion. A combat aircraft doesn't have any need for thrusters like that, or the kind of radiators you need in vacuum. It also doesn't need as much propellant nor as beefy an engine as a spacecraft, since the aircraft only needs enough power to generate sufficient forward thrust for its wings to develop lift. As a result, it helps for the aircraft to be light and aerodynamic.

Actually, I'd think a space fighter would need a less beefy engine than the aircraft; for precisely the reason that to attain the same forward acceleration, it's not having to also generate lift, or overcome drag.

Well, you could stick an arbitrarily weak main engine on a spacecraft, but it will generate arbitrarily miniscule thrust. Sure you'll still get to the same final velocity, but you're going to take a really, really long time to do it. Ergo, a spacecraft with higher performance on the helm must have more powerful engines that consume more fuel, generate more waste heat, etc.

Yeah, but if you were to replace the engine in an F16, say, with a rocket engine, it would be able to generate the same net forward acceleration with lower thrust, due to not having to bother about atmospheric and lift-induced drag.

[Batman]

Hm-don't ask me how but I seem to have seriously botched my calculations above. The actual time for a 100k km turnover would be 1.43 hours (but by all means check my figures, I think they work this time but I can still not fathom what I did to get them 3.7 hours).

[Batman]

Yeah, but if you were to replace the engine in an F16, say, with a rocket engine, it would be able to generate the same net forward acceleration with lower thrust, due to not having to bother about atmospheric and lift-induced drag.

Again, no it wouldn't (or at least not for any time worth mentioning) on account of the aircraft being much heavier thanks to having to carry the reaction mass along (which the F-16 doesn't).

[RedImperator]

Somebody, I dunno who, commented on the difficulty of designing a craft to work well in both space and atmosphere; I think this is because space superiority would require lots of less-than-aerodynamic bits and pieces that don't work well in atmo. I might be wrong, but if I'm right it would create problems for a designer.

It cuts the other way, too. In space, you pay for every gram of mass. All the metal required to enclose those parts will be dead weight in space. So will the heat shield, the control surfaces, the parts of the engine designed for the atmosphere, and the wings. That's before we start talking about radiators, which you can't keep enclosed in space. So now you need to carry a motor to fold them away, another to close a lid over them for reentry, and a lid.

If particle shields work the way I think they do, though, it should be quite easy to design a craft for air and space combat. Assuming that particle shields act, so far as particles are concerned, something like physical armor, then you could design a craft with all the bits and pieces you want, then configure the particle shield to form an aerodynamic envelope around the craft. I'd include a picture, but I fail at t3h Photoshop.

What particle shields are you talking about? Star Wars? There's a thousand Star Wars tech sites that could tell you the answer. Another franchise? Every franchise that has shields will handle them differently. I could write a story where particle shields can be shaped precisely like an aircraft, and can even provide control surfaces and landing gear, but I don't think you mean to ask "could you make up a universe where a spacecraft is a good fighter?". You need to be more specific if that's the case.

If you're talking about the real world or any franchise based on real world science, forget it.

For convenience in disproving this, this hypothesis is based on the assumptions that:
1) Particle shielding deflects particles in the same manner as more solid armor does,
2) That particle shielding may be placed at an arbitrary distance from its emitters, and
3) That space superiority requires that a spacecraft have bits and pieces tacked on which leave the craft less aerodynamic than a brick.

Even given all this, there are problems in trying to make one vehicle do two very different things well. A space fighter, as has been discussed several times in this forum, is a stupid idea. On the other hand, a flying battleship for atmospheric combat is a stupid idea, too. Consider the question "Could a tank be made into a good submarine?" The answer is, "Perhaps, with enough arbitrary wanktech", but you're still better off with one tank and one submarine instead of two vehicles which do both.

[LadyTevar]

Silly Question time:

Is SG1's F302 fighter come close to what you're thinking of?

[GrandMasterTerwynn]

Yeah, but if you were to replace the engine in an F16, say, with a rocket engine, it would be able to generate the same net forward acceleration with lower thrust, due to not having to bother about atmospheric and lift-induced drag.

It would also require around twice the propellant, since the F16 gets its oxidizer free from the atmosphere, whereas the space-F16 has to schlep its oxidizer around with it. Or use something like a nuclear salt-water rocket or antimatter or something with a similarly high energy density. (Of course, touching one of those off in an atmosphere would make it an environmental catastrophe in an aluminum can.) And you still have to add a whole bunch of other weight-intensive doodads to the space-F16, which would then require a bigger engine to push the extra weight around, etc.

[andrewgpaul]

Gah. Forgot about the oxidiser OK, higher acceleration for half the time

You're right about the need for other doohickeys, but I was specifically discussing the main engines, since the post I initially replied to seemed to say that the space fighter would need a beefier engine to move the same mass as an aeroplane. I wasn't taking into account any extras needed for working in space.

[Darth Yoshi]

Silly Question time:

Is SG1's F302 fighter come close to what you're thinking of?

Doesn't the F-302 also cheat? Sure, it has rocket engines, but there isn't enough room on one to provide the kind of thrust we see.

[Admiral Valdemar]

Unless it has an M/AM energy source and plenty of compact heavy metal ions for propellant, then yes, it cheats. Most sci-fi does that is on screen, because most sci-fi is more fantasy than sci-fi. Anyone who thinks an X-Wing or F-302 or what have you is remotely doable is living in la-la land.

[darthbob88]

After reading the above, I'm starting to get the idea that my hypothesis is feasible in Sci-Fi and movies, but not in Real Life or any realistic environment. C'est la vie; it also seems like it'd be a horrible idea in the first place to try and make an aerospace fighter craft, or even train people for combat in space and atmosphere.

[Batman]

Also, in air, a plane turns by rotating along its long axis (the wings bank - it rolls). In space, that would do nothing.

As a matter of fact that does nothing to change the direction of an aircraft, either. It is I believe called a barrel roll. To actually turn, you COMBINE pitching (which the roll turns into a horizontal as opposed to vertical turn) with yawing (which would produce minimal course changes on its own thanks to inertia and aerodynamic drag).

To change direction, you must rotate on another axis (if you look at it from above, you see it spinning in those two directions. I'm sure there is an aviation term for this, pitch or yaw I think, but I'm not sure). Whatever it is called, it is a very different move.

Depending on which way you want to turn, it's either. Pitch would be vertical, yaw would be horizontal (in a spacecraft those would presumably be relative to your direction of travel). And as I said above, the reason aircraft bank in turning is because that allows them to turn a vertical into a horizontal turn.

[Batman]

snip

I did not know that. Pretty cool stuff.

You might want to check with Broomstick but for a change I'm actually pretty sure I know what I'm talking about.

And one last thing: I said it must have thrusters to adjust during reentry, which is true of the space shuttle, but I am not sure if that is true on all craft entering the atmosphere. Apollo's capsules I think just fell entirely unpowered, and finally parachuted into the water where the astronauts were picked up by waiting naval ships. So it might be possible to get by without the little thrusters (again, I am not sure), but of course, the other problems still stand, which are enough on their own.

Without thrusters how do you initiate reentry in the first place? Wether they were part of the actual capsule or the equipment module ( I seem to remember the former but can't ATM find links saying much of anything worthwhile) so at best you need a second stage to properly align your reentry vector. Yes you DO need thrusters for proper reentry.

[Nyrath]

I don't have much to add. You will not see a combined space-aircraft fighter for the same reason you will never see a combined fighter aircraft-submarine. The equipment needed to handle one medium will just be so much penalty-weight in the other medium.

A combined craft attempting to fight a craft optimized for one medium will be metaphorically fighting with one foot in a bucket of concrete.

[darthbob88]

On the impossibility of an aerial submarine, I give you this. Worthless for proving a point, but neat.

As for maneuvering in both air and space, I had another neat idea. Since the particle shield is already formed into an aerodynamic envelope, it should be possible, with a clever enough computer, to manipulate the emitters and the envelope as needed to provide pseudo-control surfaces. In theory, you could produce a flat sheet of shielding near the craft, to produce near instantaneous braking or changes in direction. Every bit as viable as the original plan, but much more wanked and exponentially more complicated.

[RedImperator]

On the impossibility of an aerial submarine, I give you this. Worthless for proving a point, but neat.

As for maneuvering in both air and space, I had another neat idea. Since the particle shield is already formed into an aerodynamic envelope, it should be possible, with a clever enough computer, to manipulate the emitters and the envelope as needed to provide pseudo-control surfaces. In theory, you could produce a flat sheet of shielding near the craft, to produce near instantaneous braking or changes in direction. Every bit as viable as the original plan, but much more wanked and exponentially more complicated.

I already suggested this. I really don't see the fun in suggesting arbitrarily wanked technologies that serve no dramatic or speculative purpose. Why not skip the middleman and have an entire aircraft made entirely of force fields if you're going to go this route?