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For a science fiction setting I'm working on, I'm trying to make a clear division between ships made exclusively for space flight, atmospheric flight and dual-purpose ships that can fly in both. The most common example I would imagine for these dual-purpose ships are freighters that travel between planets and the fighters that escort them so they don't have to recall their fighters for entry and then deploy another set once in atmosphere.

Unfortunately, I'm no expert in aerodynamics or 3D modeling, so my ship designs are kind of boxy and often a joke in aerodynamic design despite my best efforts. The linked image is probably what I would consider one of my more aerodynamic designs that I've published a render of, though it has an atmospheric variant I'm working on that would have more aerodynamic wings and engine pods.

It got me thinking, though, maybe I could find a way to make this work within the confines of this setting. Could a combination of cheap energy and powerful thrusters allow a ship to overpower poor aerodynamics to the point where starship manufacturers can get away with cutting corners on aerodynamics to cut design and manufacturing costs?

The thought is that making fighters capable of surviving re-entry would be expensive, so they might want to cut costs elsewhere or it might become cheaper for freighters to carry two sets of fighters and go through the hassle of switching fighters as part of re-entry procedures.

I still intend for dedicated atmospheric craft to have an advantage over these dual-purpose ships, but I want them to be good enough that a skilled pilot could believably overcome that disadvantage.

These ships would likely be traveling at speeds comparable to modern jet fighters, maybe a little faster. The limitation is still going to be the forces exerted on the pilot as I don't have any kind of "inertial dampener" style tech in this setting.

Clarifications:

  • This question is more focused on fighters and smaller craft. The freighters themselves will likely need to be more aerodynamic or have to flow at much lower speeds. I'm mostly focused on the smaller ships because they would need to intercept any oncoming attackers.
  • I'm not looking for suggestions for alternate designs. I'm simply trying to find out if my existing designs aerodynamic shortcomings due to my own lack of expertise in the field can be justified in-universe.
  • The speeds in question would be more in the combat speed range than cruising speeds.
  • The dual purpose atmospheric+space use fighters will still have an attempt at aerodynamics. They won't be flying bricks. The idea is that the manufacturers might not put anywhere near as much time and effort into aerodynamics as we do any modern aircraft to cut costs.
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    $\begingroup$ It's not just the retardive friction/lift relation you need to worry over, it's also the turbulence and stability - trying not to shake your pilots to pieces or tear the plane apart in an uncontrolled tumble might figure in the design. $\endgroup$ Jul 17 at 16:55
  • $\begingroup$ I guess I could ask if my example design is "aerodynamic enough" to not worry about that? Would that be a better way to structure my question? $\endgroup$
    – Arvex
    Jul 17 at 17:01
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    $\begingroup$ "cheap energy and powerful thrusters" isn't enough because the ship's structure must also be heavily reinforced to handle the increased structural stresses caused by poor aerodynamics and more powerful thrusters. If you're going to go full on sci-fi, use external force fields to shape airflow around the craft and then it can have any shape you like. (Of course, if the power goes out, the craft will instantly be hit by the full effects of its shape and likely disintegrate.) $\endgroup$ Jul 17 at 17:09
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    $\begingroup$ Endurance is another issue. Drag and gravity losses eat up a spacecraft's delta-v budget very rapidly. Airfoils and air-breathing engines are needed to make a usable atmospheric fighter, but are dead mass on a space fighter, never mind all the thermal protection required. Then there's the drastically different sensors/weapons needed, the different navigational instruments and flight controls required, etc...the environments are just too different for something effective in one to be more than a joke in the other. $\endgroup$ Jul 17 at 18:08
  • $\begingroup$ I added a few clarifications since I meant to specify that the ships in question would still have some aerodynamic design effort put into them, but because I'm no aircraft expert, my designs would likely fall short by real world standards. (The linked image is a good example of what I mean by "some effort.") $\endgroup$
    – Arvex
    Jul 18 at 0:54
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The brief answer is “no”. At fighter-jet speeds, overheating from atmospheric drag is also an enormously important issue, so even if you have an engine that needs no fuel at all, you still have to be aerodynamic.

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    $\begingroup$ To add to it, it's not just overheating. It's also sheer force on the material that can buckle, sheer or otherwise deform. Aerodynamics helps reduce the strain as well. $\endgroup$
    – Trioxidane
    Jul 17 at 20:25
  • $\begingroup$ So low drag and airflow management are always important, but lift is basically optional. (e.g. a setting like BattleTech's AeroTech fighters that are optimized for space and have fusion engines. Thrust in atmosphere is near-free using fusion energy to heat air I think, although I think a lot of that is hand-waved in the aerotech rules, IIRC from ages ago, and probably have implausible amounts of delta-V in space) $\endgroup$ Jul 18 at 4:56
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    $\begingroup$ Should probably also mention maneuverability. A cube-shaped plane would probably be very unstable and hard to control. $\endgroup$
    – MaxD
    Jul 19 at 0:41
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Totally possible - Your energy abundance results in you travelling MUCH slower than current space missions.

Space isn't that high up. The ISS is 408km above the ground. If it was horizontal you could get there in a car at highway speeds in 4 hours.

Space as we know it isn't high, its FAST. That ISS is travelling at 7.6km/s. It needs to do that speed to maintain an orbit. If it slows down, it falls out of orbit. To travel any slower it'd need to be constantly thrusting upwards.

Re-entry as we know it is a transfer from LEO using minimal fuel in orbit to subtly perturb the orbital ellipse so it skims the atmosphere, resulting in spaceships hitting the atmosphere at hypersonic speeds. Because of these hypersonic speeds, aerodynamics is everything.

However, if you have an epic power supply, you don't need to conserve fuel. Because you don't need to conserve fuel, you don't need to travel at 7.6km/s. You can travel at car speeds. You could fly upwards at 100km/hr for 4 hours. Stop at 408km in altitude, keep the engine trusting upwards at about 1g, and watch the ISS shoot fast at bullet speed, and think "Hey that's soo cool", then return home, never having exceeding 100km/hr. 9 hour total journey.

Because you don't exceed highway speed in the atmosphere at any point, your ships can be as aerodynamic as anything you see on the road.


You can of course travel faster when in the vacuum of space if you want, just remember to follow your crafts atmospheric speed limit during re-entry, otherwise you will burn up.


Note that obviously the freighters and fighters travel at approximately the same speed.

Remember if the freighters are travelling at 100km/hr then their escorts are going to be travelling at ~100km/hr too to stay close. An interceptor sent out to get them can travel at whatever speed they want, but if they're travelling much faster they're going to overshoot. All battles takes place at highway speeds because no-one needs to travel at hypersonic speeds, nor gets any benefit to doing so.

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    $\begingroup$ The question is about non-aerodynamic fightercraft maneuvering in combat in an atmosphere, not the transport itself? $\endgroup$ Jul 17 at 18:02
  • $\begingroup$ Planets are big; it's probably useful to be able to get from space to ground a lot faster than 4 hours. But yes, interesting perspective on what's possible, if there's some reason not to at least streamline. (Lift can be replaced with thrust, but ability to go fast in air without disintegrating or melting is nice, especially when you have that much thrust. Especially for military vessels, even military freight transport: a slow convoy can't escape into space as quickly if danger shows up.) $\endgroup$ Jul 18 at 5:01
  • $\begingroup$ @GrumpyYoungMan Yes I'm aware. But remember If the freighters are travelling at 100km/hr then their escorts are going to be travelling at ~100km/hr too to stay close. An interceptor sent out to get them can travel at whatever speed they want, but if they're travelling much faster they're going to overshoot. The whole battle takes place at highway speeds because no-one needs to travel at hypersonic speeds, nor gets any benifet to doing so. $\endgroup$
    – Ash
    Jul 18 at 10:11
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    $\begingroup$ @Ash I love the challenge to my intuition. I kept trying to make the craft go fast, like we do! However, as for the combat speed, while the defenders may only have to hang out in the vicinity of the freighter, air combat typically does not reward the slow. Evolving faster aircraft (and faster weapons) will always provide an advantage. That being said, your answer does drop the lower bar to... well.. as you put it, car speeds! $\endgroup$
    – Cort Ammon
    Jul 18 at 15:11
  • $\begingroup$ @PeterCordes you can get down very fast, if you figure out how to shed excess heat while up high and excess speed when down low. You will reach zero speed at zero altitude in any case, but humans tend to break when subjected to too much acceleration. $\endgroup$ Jul 18 at 17:31
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Here's the thing-- I don't see the aerodynamic issue as so much a matter of cost as one of fuel. The less aerodynamic, the more fuel the ship will spend when in an atmosphere, and the lower its range.

On the other hand, the more you add wings and whatnot to make it aerodynamic, the more fuel the ship will spend when out of the atmosphere (because it weighs more).

So if you want to favor less aerodynamic fighters, I'd say the best justification would be to make their primary use maneuvering in space. This is especially justifiable because space combat would likely take more fuel than aerial combat, and need more optimization toward it. That way the economics justifies optimizing to have less aerodynamic gizmos in favor of more room for fuel and thrusters for more efficient maneuverability in space.

Also, optimizing for combat in a vacuum allows you to have battles over planets with little or no atmosphere like Mars.

Hope that helps!

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    $\begingroup$ I've upvoted this because it deals with something the other answers ignored, but in turn, this somewhat ignores the complexities of in-atmosphere flight dynamics. $\endgroup$ Jul 18 at 4:07
  • $\begingroup$ @ARogueAnt. Partly because I hardly know anything about aerodynamics except what I've learned from playing KSP. 😉 $\endgroup$ Jul 18 at 4:32
  • $\begingroup$ How about a surface to orbit craft that ditched its wings etc when leaving the atmosphere, allowing those to return to the launch site by themselves. $\endgroup$
    – DrMcCleod
    Jul 18 at 11:21
  • $\begingroup$ @DrMcCleod Could probably work in theory... a lot of odd mechanics to work out. But the main problem with that is that the original ship doesn't have a good way to get back into the atmosphere (for the context of this question) $\endgroup$ Jul 18 at 11:23
  • $\begingroup$ @Benjaminhollon Perhaps it could leave the wings in orbit then, and grab them on the way home. $\endgroup$
    – DrMcCleod
    Jul 18 at 15:42
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Proposal:

  1. Freighters are totally nonaerodynamic agglomerations of containers and other structures. They use the thrusters to slow from orbital speed on re-entry and then schlep along wastefully thru the atmosphere. Maybe they even come down into the ocean and turn into boats. They try to come down close to where they want to be.

  2. You do have space fighters and atmospheric fighters. The atmospheric fighters are carried aboard the freighter and emerge when there is enough atmosphere. Some might come up from the port and escort the freighter in. The space fighters are nonaerodynamic spheres.

There is a point during (the slow, slow) freighter re-entry where the space fighters have all come inside but the atmospheric fighters are not out yet. That is when the pirates come, and these are the ones that have the dually able ships. Those ship need to stay in their narrow zone because they will be outgunned by either the space fighters or the atmospheric fighters.

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I give you, Battlefield Earth

The book, not the film, which stank so badly that it could be smelled in the Antarctic.

L. Ron Hubbard faced the very same question and came up with the very same response. He had a fundamentally undefined unlimited-energy source combined with the coolest idea on the planet: teleportation engines (the space inside the engine teleported, producing motion).

But the tech was being used by the Psychos, who were a remarkably uncreative but entirely capitalistically-driven species. And they not only had energy and thrusters — they also had nearly indestructible metal. It didn't matter to them at all if anything was particularly aerodynamic.

What mattered is that they were inexpensive and disposable.

And this is the point of my answer

Economics have as much (and occasionally more) to do with design than aerodynamics. Planes are shaped the way they do only because they're needed to be so to keep them in the air. If we had some kind of gravitics keeping them afloat, they'd look like buses because that shape is a whole lot cheaper to build.

So, if your world has an ignorable economy, shapes will include aerodynamics because people can afford both the artistry and the benefit. If you don't have an ignorable economy, then cost will limit just how aerodynamic anything will be. The balance will be, "can I move it enough with acceptable losses to gain the win I desire?" because anything else will cost more.

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If you have no fuel budget and your materials are strong enough to withstand aerodynamic stresses then the shape of the fighter is not hugely important To Quote Enzo Ferrari:

“Aerodynamics are for people who can’t build engines.”

Your differential in Space vs atmosphere fighters is more likely to come from weapon fit. In space the best weapon fit might be lasers, whereas in atmosphere these might not be as effective so missiles are the best choice. The skill of you pilots could be in using the suboptimal weapon system.

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The perfect dual-purpose fighter: A Sphere

Having limitless energy means that you can deorbit and land pretty much anything with the structural integrity to stay intact in gravity. Aerodynamics only limits how fast you can move in-atmosphere, as long as you don't mind a snails-pace you can land even the most ungainly of ships.

I believe it's been explored in a different question, but the ideal manned space fighter should have it's thrusters, weapons, and cockpit all able to rotate independently, in order to maximise both manoeuvrability and G-tolerance (so that the pilot is always "Eyeballs In").

A space-only fighter can be cheap and lumpy with random stuff bolted on, but if that goes into atmosphere and tries to move at anything resembling combat speeds it will tumble uncontrollably.

The solution then, is to make sure that all that hardware fits within a spherical hull. It would be less flexible in loadout and modifications than a dedicated fighter of either type. Also somewhat less space efficient than a brick-shaped space-fighter, if that matters.

A sphere has decent aerodynamics and, most importantly, no preferred aerodynamic orientation. The fighter can still rotate, thrust, and fire in all directions without the air trying to pull it a certain way. Lacking wings just means has to adjust its thrust vector to account for gravity.

You can even easily slap on a detachable hemispherical heat-shield for when you need to reenter at high speed.

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