Quick question on centrifuges.

[sgt_flyer]

54 minutes ago, Nuke said:

because a spinning ship is a big massive gyroscope and gyroscopes tend to resist changes in orientation. a big ship spinning around is going to have a lot more angular momentum than a small part of a big ship spinning. so it will require additional rcs thrust to maneuver. and in turn that means more rcs propellant is required for the mission. on top of that now every part of your ship is subject to centrifugal force, so you start introducing forces that want to pull your ship apart which require additional structural strength, and that means more mass as well.

at least thats my understanding, i could be wrong and if i am please correct me.

another problem with a fully spinning ship, is that you need a way to keep your antennas targeted towards earth, and keep your solar panels and radiators correctly orientated for sunlight (so you end up needing mechanical systems anyway to keep those systems correctly lined up, with the same problems as previously - torque, friction and reliability) fuel centrifugation and slosh would have to be taken into account too, maybe needing to be able to design the propellant tanks to be able to work both in zero-G and while spinning.

Edited March 10, 2016 by sgt_flyer

[Nuke]

spinning tanks do have advantages, for example you can use centrifugal force for the pumping action, simply place your engine "below" your tanks in its rotational frame of reference. it may also help slow and perhaps aid in recovery of boil off. so certain fuel configurations it may be advantageous. these configurations are gonna need to be a long skinny ship with habitation ring of sorts to minimize angular momentum and reduce g forces at the tankage and other parts to reduce structural mass. you still need coms and solar gimbals i suppose but those can be rather small. if the ship spends most of its time pointing into its trajectory, and its not to eccentric it can put the radiators pointing along the long axis. solar on the other hand can be put on a large boom out the front of the ship which can rotate to stay pointed at the sun.

i think space craft engineering starts at the engine and works its way out. heres our engine we need this fuel/propellant , we also need this much power, and you pick your tankage and power plant, then figure out how much heat you got to get rid of. i bet crew comfort comes last in that metric.

Edited March 10, 2016 by Nuke

[fredinno]

14 hours ago, SpaceMouse said:

Just had a random idea i assume is stupid. Has anyone ever done a concept for a actual hollow sphere for a habitat? While i don't think it would be very practical or necessary, it was at least a amusing idea.CENTRIFUGE ALL THE THINGS! If it spins in all 3 axis i think it... might... work...

That is not how centrifugal acceleration works.

[SpaceMouse]

4 hours ago, fredinno said:

That is not how centrifugal acceleration works.

Details.  Details. 

[SpaceMouse]

5 hours ago, Nuke said:

 

i think space craft engineering starts at the engine and works its way out. heres our engine we need this fuel/propellant , we also need this much power, and you pick your tankage and power plant, then figure out how much heat you got to get rid of. i bet crew comfort comes last in that metric.

See,  i think that's part of the problem. Particularly on some long endurance mission you need to treat people like they're people and not cargo. Not that I'm NOT aware space travel is a glorified math problem....

[andrewas]

2 hours ago, SpaceMouse said:

Details.  Details. 

For any rigid body, at any given instant, you have one axis of rotation. With some shapes, the axis of rotation can shift over time, which means the gravity at a given point would change, which is not desirable. A sphere with fairly even mass distribution won't do that, it'll rotate on a single axis. Which means the equator gets full g and regions nearer the poles get partial g and steep slopes.

[Nuke]

6 hours ago, SpaceMouse said:

See,  i think that's part of the problem. Particularly on some long endurance mission you need to treat people like they're people and not cargo. Not that I'm NOT aware space travel is a glorified math problem....

i really only mean to say that how you build your centrifuge is going to depend on a lot of other design factors, propulsion, power, what kind of fuel you use, etc. if we didnt care about the humans we wouldn't build a centrifuge at all. we would just stuff em into a tin can like sardines (much like most airlines nowadays).

[SpaceMouse]

5 hours ago, andrewas said:

For any rigid body, at any given instant, you have one axis of rotation. With some shapes, the axis of rotation can shift over time, which means the gravity at a given point would change, which is not desirable. A sphere with fairly even mass distribution won't do that, it'll rotate on a single axis. Which means the equator gets full g and regions nearer the poles get partial g and steep slopes.

I did realize there was a awful lot of practical issues with it. I have no intention of making any spherical parts.