Why Couldn't Spaceships be Rectangles?

So, I'm debating on buying the new computer game Elite - Dangerous. Stay with me, I'm not on the wrong forum. I was looking at all the 'cool looking' spaceships in the game and this thought occured to me.

Since it's in space, why do spaceships have to be shaped aerodynamically?

Here on earth where you have air molecules engineers spend a lot of time designing the shapes of surfaces to interact with those air molecules to optimise lift and minimize drag.

But, if you are out in space that wouldn't really matter would it?

I mean a spaceship that looks like a 'really cool airplane from the future' shouldn't fly any better than a spaceship that looks like a big cube or rectangle, correct?

Or am I missing something?

 

To get to space from earth, you still have to pass through the atmosphere. I'm guessing that plays a role in determining the shape.

 

Actually, if your spaceship can fly close to the speed of light, you might want it to be shaped more like an aircraft, because at those speeds space would behave more like a gas than a vacuum.

But at lower speeds, the only manned spacecraft I can think of that was designed solely for flight in space was the Apollo Lunar Module, and you can see how aerodynamic that was!

 

I think your right, it is explained well here http://physics.stackexchange.com/questions/29955/would-a-fast-inter-stellar-spaceship-benefit-from-an-aerodynamic-shape

 

Edited to add: Just seen Lance Schukies' post

 

Wasn't the Borg ship cubed shaped?

 

Yes, but that was because they travelled via trans-warp corridors, thus using the "folding" nature of space to effectively compress the space through which they travelled, thus only travelling at non-relativistic velocities. Because of the "folded" nature of space, the distance that they needed to travel was materially reduced, thus transit time gave the appearance of FTL travel.

 

Outer space is not a true vacuum and as velocities increase the tiny amount of matter that is encountered starts to become more significant. That being said, many sci-fi franchises have made use of ships that are far from "airworthy" as regards aerodynamics in order to effect a certain look of military seriousness. The Sulaco from the film Aliens is not aerodynamic in the least, though she does present a very intimidating, "all business" sort of personality.

 

Aerodynamic ships have a somewhat phallic appeal.

However, apart from that, see Wrey's point. The vacuum of space not only isn't absolute, it varies considerably in density. It's never even close to the density of Mars at high altitudes, but the density in a nebula can produce significant drag and skin friction, even turbulence, at relativistic velocities. You could still see across interplanetary or even interstellar distances without noticeable "cloudiness", but it still acts as drag.

 

I actually think a spaceship built like a Hoberman Sphere, one of those toys that expands and contracts, would be a better design. My logic is that for maneuvering the ship would contract allowing for easier turning motions, possibly. However while traveling through space the expanded ship would present a less "solid" target, and if one section was taken out by a bit of debris or missile the damage would be very localized. Additionally targeting would end up aiming at a bunch of nothing in many cases, passing right through it.

On the flip side accessing various parts of the ship might be complex and obviously it would take a lot of material to build compared to a simple Death Star design. Just don't make it shaped like a Klein bottle.

 

Not to derail this train, but why in HELL are exercise bikes set up aerodynamically... like racing bikes? You know ...narrow seat, handlebars way front, so you have to hunch over to reach them as if you're booking for the finish line. I mean, the damn things aren't going anywhere, and you don't need to steer them. Why can't you just sit up straight on a comfortable seat, rest your hands on handlebars simply for balance, and pedal? Never mind, rant over ...as you were...

 

I think it's more to do with how much effort you can put in...sitting upright on an armchair of a saddle and you'll have significant "drag" on your buttocks as you move them up and down on said saddle - razor-blade of a saddle won't create as much friction. Similarly with the leaning-forward posture - the thrust will be more up and down rather than backwards and forwards.

 

Okay, I buy that. To an extent. (Although what's wrong with a touring bike rather than a racing bike design?) But while I love my exercise bike, I always stop before I'm ready because the seat is uncomfortable because of the fixed angle (I've bought a gel pad, so padding isn't the issue), and my wrists hurt like hell from holding onto the handlebars. And no, they're not adjustable. And because of the seat angle which tips me forward, I can't ride 'no hands.' Bummer. Bad design. Maybe other bikes are better? Anyway, I don't want to derail this thread, but thanks for the insight...

 

The bike that we inherited from my mother-in-law was comfortable enough to sit upright and pedal, look-no-hands.

 

If it is sci-fi we are talking, then why not? You just need some sort of technological explanation for the design choice.

 

I'm guessing that spaceships have to be versatile in fluid and vacuum environments. Spaceships are used in both space and planet atmosphere so it only makes sense that they still have to be aerodynamic. However, maybe it's a design necessity, but we wouldn't know because spaceships aren't exactly common right now.

 

It's not that big. Cool image.

 

In most serious science fiction, the ships that cross the void don't land on planets. They carry smaller landing craft designed for atmospheric use, specialized for the round trip into a gravity well and back again. Or they use transfer vessels provided by the port of call.

Ever see an amphibious craft? Remarkable machines, but they never outperform craft designed solely for one or the other medium in that medium.

 

Spaceships shouldn't really have to be any particular shape, especially if they are faster than light capable, since that is basically impossibly given our current technology level and understanding of physics. So, if you get to the point where ships are moving faster than light, you are already using some psuedoscience to explain that, at which point you can probably use some of that same stuff to explain why the ship is the same shape as a flying (instert polygon of choice here).

Whatever the actual physical reasons behind ship design might be, in science fiction, you can get away with a lot as long as you can make it sound plausible in a way that will not piss off the real hardcore sciency readers.

And Elite looks awesome. In a video game, I think the Rule of Cool takes precedence over physics, so that probably explains why the ships all look the way that they do.

 

It is probably due to the need to travel in space and the atmosphere of various planets, plus the need to look cool for the audience.

Also, I might add that there are valid reasons to require certain shapes for fast travel, one of them being the need to deal with the force exerted from whatever type of thrusters/propulsion system the craft has. While I can't say that "plane like" would be the way to go, there would be certain shapes that would break up if they accelerated too fast.

 

Like, for example, human shapes.

Humans can't stand too many g-forces. If we want to make the acceleration comfortable for humans, then it would very likely be comfortable for nearly any metal structure. I strongly doubt that a starship carrying humans would be accelerating at more than about one g - people don't like that, and it's going to be a long trip anyway, Millennium Falcon or no Millennium Falcon.

Sure, you need a space-shuttle kind of structure, and lots of g's, to get into and out of atmospheres. But a ship designed only for space travel - never entering an atmosphere or deep into a gravity well - wouldn't require large acceleration.

 

At some point the space ship would have to take off from the planet that built it. I imagine it would be very difficult for a cube shaped ship to leave the atmosphere. The increased amount of fuel required would also reduce its range.

 

This is precisely why nobody imagines space ships like that any more. You build a big, cube or sphere or abstract or whatever shaped space ship (mother ship) just to travel in space. You use shuttle crafts to get you down to the surface of a planet and back up to the mother ship. The mother ship never enters an atmosphere.

You don't build the mother ship on the ground. You launch components up into orbit and assemble the mother ship there, just the was the International Space Station has been built. You want a cube-shaped ship like the Borg ship in Star Trek? Assemble it in orbit - it never travels through an atmosphere.

 

Building a space ship in space using what is already available might be a possibility. Do like the Dresser Crab and pick up old satellites and reshape them to your needs. Another thread was about catching an asteroid several weeks back, that might provide a way to get raw materials for something larger. Even building on the moon with 1/5th gravity would make it possible to assemble larger stuff and avoid atmosphere resistance constraints. I believe they built the ships for Star Trek in orbiting factories.

It probably would be hard to write an interesting sci-fi with the plot being assembling spaceships but maybe there could be some interesting twists in it.