3 ms·

By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped

By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped spacecraft be the most efficient?

icegreentea2 3y ago
Only if instantaneous large accelerations in arbitrary directions is amongst your primary performance requirements. You'd need to have thrusters ready to fire in arbitrary directions as well. A spherical (specifically) spacecraft would also have more heat dissipation challenges.
carabiner 3y ago
There are 1,000 other requirements that do not demand maximum 3D rotation efficiency.
dmbche 3y ago
The space between things in space is quite large, so you're going in a single direction for a while. The thrust from the spacecraft is also used to exploit gravitational energy (slingshoting around planets) for the most part, from my understanding. In Sci-fi, it's generally understood that very fast crafts (0.1c and up) will need to reverse and apply thrust opposite their direction to slow down for a very large part of the voyage (up to more than half) - so could be a good idea to be able to flip around and apply thrust the other way too.
- 0cf8612b2e1e 3y ago
  Plus, without deflector shield voodoo, a skinny tube design minimize your cross sectional area and how much debris you will impact.
pdonis 3y ago
No. Such a craft would either need to have full thrust engines pointing in every possible direction (way too costly and overbuilt) or would have to have some way of rotating its full thrust engines to be at any arbitrary angle relative to the ship (which then means you have to transfer all the thrust through gimbal mounts or whatever you're using to be able to rotate the engines, and those things won't be able to withstand that kind of stress). It's much easier and simpler to point your full thrust engines in one direction (out the back of the ship), so the thrust gets transferred through the entire ship's fixed structure, and then have smaller thrusters to rotate the ship to point in the direction you want to go.
outworlder 3y ago
> By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped spacecraft be the most efficient? Definitely not. There's very little need to 'maneuver flexibly in 3D space'. You are mostly interested in rotation. A slight amount of translation if you are trying to dock with something else. You will likely still prefer to thrust mostly in a 'forward' (wherever forward is) direction. If, for some weird reason, you wanted to have thrusters equally powerful in all directions, just imagine the amount of weight (and plumbing) this would require.
tonyarkles 3y ago
I think one of the most interesting things about space flight is how inflexibly your maneuvering actually is compared to how it’s portrayed in TV and film. As an example, in a given orbital altitude you cannot really speed up or slow down without changing your altitude. You can’t really move side to side at all without completely changing your orbital trajectory.

By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped spacecraft be the most efficient?

icegreentea2 3y ago

Only if instantaneous large accelerations in arbitrary directions is amongst your primary performance requirements. You'd need to have thrusters ready to fire in arbitrary directions as well. A spherical (specifically) spacecraft would also have more heat dissipation challenges.

carabiner 3y ago

There are 1,000 other requirements that do not demand maximum 3D rotation efficiency.

dmbche 3y ago

The space between things in space is quite large, so you're going in a single direction for a while. The thrust from the spacecraft is also used to exploit gravitational energy (slingshoting around planets) for the most part, from my understanding. In Sci-fi, it's generally understood that very fast crafts (0.1c and up) will need to reverse and apply thrust opposite their direction to slow down for a very large part of the voyage (up to more than half) - so could be a good idea to be able to flip around and apply thrust the other way too.

0cf8612b2e1e 3y ago
Plus, without deflector shield voodoo, a skinny tube design minimize your cross sectional area and how much debris you will impact.

pdonis 3y ago

No. Such a craft would either need to have full thrust engines pointing in every possible direction (way too costly and overbuilt) or would have to have some way of rotating its full thrust engines to be at any arbitrary angle relative to the ship (which then means you have to transfer all the thrust through gimbal mounts or whatever you're using to be able to rotate the engines, and those things won't be able to withstand that kind of stress). It's much easier and simpler to point your full thrust engines in one direction (out the back of the ship), so the thrust gets transferred through the entire ship's fixed structure, and then have smaller thrusters to rotate the ship to point in the direction you want to go.

outworlder 3y ago

> By the way, since you need to apply thrust from any direction to maneuver flexibly in 3D space (without wind or gravity), wouldn't spherical/disc(saucer) shaped spacecraft be the most efficient? Definitely not. There's very little need to 'maneuver flexibly in 3D space'. You are mostly interested in rotation. A slight amount of translation if you are trying to dock with something else. You will likely still prefer to thrust mostly in a 'forward' (wherever forward is) direction. If, for some weird reason, you wanted to have thrusters equally powerful in all directions, just imagine the amount of weight (and plumbing) this would require.

tonyarkles 3y ago

I think one of the most interesting things about space flight is how inflexibly your maneuvering actually is compared to how it’s portrayed in TV and film. As an example, in a given orbital altitude you cannot really speed up or slow down without changing your altitude. You can’t really move side to side at all without completely changing your orbital trajectory.