Centrifuge's on a spacecraft

[mrmcp1]

Many science fiction books and films have spacecraft will a centrifuge to generate artificial gravity. My question is would a single centrifuge produce a force on the ship and if there is a force would a counter rotating centrifuge solve this problem. Hope you can help as I find centrifuges on spacecraft an interesting prospect.

[SargeRho]

Yes, a single centrifuge would produce torque, since you can't have zero friction. You can solve that by adding a second one spinning in the opposite direction, or just a counterweight. You can also build the entire ship as a centrifuge.

[mrmcp1]

Thanks for the quick reply. I though that would be the case but I wanted to check.

[Nibb31]

Another topic that has been beaten to death already.

http://forum.kerbalspaceprogram.com/threads/73282-Let-s-talk-about-centrifuges?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/72851-Does-artificial-gravity-improve-the-reliability-of-life-support-systems?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/76877-Could-centrifugal-force-solve-some-long-term-spaceflight-problems?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/81317-What-is-the-best-axis-of-rotation-for-an-Earth-orbiting-rotating-space-station?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/77614-Fitting-rotational-gravity-segments-on-rockets?highlight=centrifuge

The thing is, we don't know if a centrifuge is even necessary. People have survived in space for long periods without one. If artificial gravity is actually proven to be more beneficial than other methods of reducing bone-loss (including exercice, diet, medication, etc...) then it would be much easier to simply spin the entire ship. Having a rotating section attached to a non rotating ship just adds unnecessary complexity and critical failure points for no good reason.

[MC.STEEL]

Another topic that has been beaten to death already.

http://forum.kerbalspaceprogram.com/threads/73282-Let-s-talk-about-centrifuges?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/72851-Does-artificial-gravity-improve-the-reliability-of-life-support-systems?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/76877-Could-centrifugal-force-solve-some-long-term-spaceflight-problems?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/81317-What-is-the-best-axis-of-rotation-for-an-Earth-orbiting-rotating-space-station?highlight=centrifuge

http://forum.kerbalspaceprogram.com/threads/77614-Fitting-rotational-gravity-segments-on-rockets?highlight=centrifuge

The thing is, we don't know if a centrifuge is even necessary. People have survived in space for long periods without one. If artificial gravity is actually proven to be more beneficial than other methods of reducing bone-loss (including exercice, diet, medication, etc...) then it would be much easier to simply spin the entire ship. Having a rotating section attached to a non rotating ship just adds unnecessary complexity and critical failure points for no good reason.

Much thanks to me.

EDIT:now i see none of the examples use my treads of the topic.

[Nuke]

also this is relevant:

http://www.artificial-gravity.com/sw/SpinCalc/

[MarkyJ279]

I remember seeing an article on the BBC news website recently of some experts who were asked to plan a theoretical mission to mars with an interesting solution to the problem. They seperated the (equal mass) lander module and the command module with a long tether and then used RCS to spin the ship end over end like a bolas. With a long tether they could get decent gravity even at slow rotation speeds and they wouldn't have to faff around with rings or bearings.

On topic though, if you spun your centrifuge clockwise it would exert an equal force in the form of torque on the main section that would cause it to spin anti-clockwise. A second centrifuge of equal mass and speed going in the other direction would result in some interesting stresses between the bases of the two rings but would otherwise balance the forces involved

[Nibb31]

Yes, that's another way to do it. Again, does the benefit outweigh the drawbacks in risk and complexity? What happens if the tether breaks? How do you perform correction burns with a bola arrangement?

[Dodgey]

Yes, that's another way to do it. Again, does the benefit outweigh the drawbacks in risk and complexity? What happens if the tether breaks? How do you perform correction burns with a bola arrangement?

You have multiple teathers. Redundancy is your friend. Also you would spin down and reconnect for correction burns.

[SargeRho]

As far as I know for Mars Direct the plan was a 1500m long tether, requiring only one RPM for sufficient gravity. If the tether was to break apparently the mission could continue unimpaired.

[shynung]

As far as I know for Mars Direct the plan was a 1500m long tether, requiring only one RPM for sufficient gravity. If the tether was to break apparently the mission could continue unimpaired.

That's 2 separate spacecrafts, intended to work as one, moving away from each other at about 157 m/s (correct me if I am wrong). A maneuver to make them meet each other again should take at least that much delta-v. That may eat into the mission's delta-v budget enough to impair the mission.

[Lukaszenko]

Yes, that's another way to do it. Again, does the benefit outweigh the drawbacks in risk and complexity? What happens if the tether breaks? How do you perform correction burns with a bola arrangement?

I think of all the things that could break on a spacecraft, a tether is the simplest to design against. It's just a simple calculation that we could whip off in a minute on an envelope. There wouldn't even be any fatigue stresses. It just seems scarier than it should be simply because such a failure appears quite catastrophic.

[Nibb31]

It's still a single point of failure with no redundancy. It's also unnecessary.

[MockKnizzle]

Just have three cables, a single one of which is strong enough to hold the craft together. Problem solved.

[Nibb31]

Adds unnecessary mass. Redundancy isn't just "add three of everything". That is extremely poor engineering practice. It simply multiplies the weight of the vehicle and if there is a flaw in the design, then all three parts will have the same flaw and the same chance to break.

Designing a space mission is about designing to requirements. Anything extra increases cost, complexity, weight, and risk. Keep it as simple as possible. Redundancy is usually built into systems by allowing dual use of equipment, for example Apollo could use the LM's descent engine for course corrections if there was a failure with the CSM engine, the EVA suits could be used to transfer the astronauts between the LM and the CSM if the docking mechanism failed, etc...

We don't know if artificial gravity is required. Our experience is that people have successfully flown long duration missions on the ISS without it. Most negative effects of microgravity can be countered with medication, diet, and exercice. We also know that centrifuges may have a negative effect on orientation, balance, and maybe also induce side effects on the circulatory system as well as nausea.

So right now, there is no reason to include a centrifuge on a Mars mission. It might be required for further destinations, but we really don't know.