How do real rockets / space planes turn or spin without RCS?

[lammatt]

can someone tell me if it's possible and if so the mechanism how a space vessel turns or spins without a working RCS

[NovaSilisko]

Usually reaction wheels: http://en.wikipedia.org/wiki/Reaction_wheel

But they are very slow.

[stupid_chris]

Indeed, those are most often used for long term missions, missions far from earth, and on light crafts. The ISS does have reaction wheels, but it' to keep it's heading as it doesn't really need to turn around and stuff like that.

[espm400]

Usually reaction wheels: http://en.wikipedia.org/wiki/Reaction_wheel

But they are very slow.

A bit off-topic, but following the wiki link I heard about Japan's 'Hayabusa' craft. Further reading unveiled to me the completely Kerbal-esq failure of the MINERVA minirover... They sent the command to drop it whilst the parent craft was maneuvering, thus instead of landing it, they accidentally just launched it into space. Fantastic...

[NeoMorph]

They use them on satellites and space telescopes too. It's the reason that the Kepler space telescope is near to breaking because out of four wheels, one died and a second one died quite recently and they need two to keep it working. Dunno what they are going to do to fix it, I guess they could send up the Shuttle to... oops!

[stupid_chris]

They use them on satellites and space telescopes too. It's the reason that the Kepler space telescope is near to breaking because out of four wheels, one died and a second one died quite recently and they need two to keep it working. Dunno what they are going to do to fix it, I guess they could send up the Shuttle to... oops!

The three first wheels are pretty much dead if I understood correctly and the fourth backup one is suffering from too much friction, so it probably won't last long. And anyway, it would be hard to send the shuttle on a solar orbit, even if it was still in operation

[Whackjob]

Hence the necessity of RCS tugs and docking ports. If Kepler had a docking port, we could've hauled it back into low Earth orbit, gave that piano a tuneup, and sent it back out for some of that sweet Heliocentric music.

[espm400]

Hence the necessity of RCS tugs and docking ports. If Kepler had a docking port, we could've hauled it back into low Earth orbit, gave that piano a tuneup, and sent it back out for some of that sweet Heliocentric music.

From a realist standpoint though, that mission's probably done. At least it got some decent info while it was out there.

[longhornchris]

Reaction wheels or control moment gyroscopes are used for routine control. That said, both only function as momentum exchange devices so RCS, torque rods, or some other methods are needed to allow the vehicle to dump excess momentum if the vehicle accumulates it due to some sort of imbalance. The key advantage to CMGs or Reaction Wheels is that they are very precise while RCS thrusters tend to have a minimum thrust and thus a minimum torque which makes precision pointing difficult.

In order to make KSP behave like real life, there would have to be an angular momentum accumulation that keeps track of how much is being stored in the reaction wheels or CMG array and have the vehicle saturate when the maximum momentum is reached.

[stupid_chris]

In order to make KSP behave like real life, there would have to be an angular momentum accumulation that keeps track of how much is being stored in the reaction wheels or CMG array and have the vehicle saturate when the maximum momentum is reached.

True, but micromanagement much. No doubt it would make a good mod for added difficulty like modular fuel and remote tech though

[stupid_chris]

Dammit, double post, sorry folks. If a mod sees this, feel free to delete.

Edited July 20, 2013 by stupid_chris
dammit

[spikeyhat09]

well, space planes would obviously use control surfaces to roll, pitch, and yaw

[arq]

In order to make KSP behave like real life, there would have to be an angular momentum accumulation that keeps track of how much is being stored in the reaction wheels or CMG array and have the vehicle saturate when the maximum momentum is reached.

They could add some sort of 'saturation' tracker to recognize when the wheels could no longer provide control, and they could passively de-saturate over time (imagine magnetic torquers doing that bit). It would be equivalent to an overheat system, though without exploding upon saturation (technically, turning the opposite direction would also de-saturate the wheels, but that would be too troublesome to track).

...But honestly, I don't see such a mechanic adding to the game in a meaningful way. Just pretend they have limits and use them sparingly, if you really want.

[joethebeast22]

From a realist standpoint though, that mission's probably done. At least it got some decent info while it was out there.

it kinda bums me out that that probe is dying, i loved going on NASA's website to see what kepler uncovered from day to day, i think they should launch a replacement, the data we could find is and what we have found is too important to abandon

[espm400]

it kinda bums me out that that probe is dying, i loved going on NASA's website to see what kepler uncovered from day to day, i think they should launch a replacement, the data we could find is and what we have found is too important to abandon

It gave us some good information while it was up and running (something tells me someone got fired over those reaction wheels...), but you only have about five more years until the JWST launches, and hopefully with what it will provide, it will make Kepler pale in comparison. At least we still have Hubble for the time being.

[longhornchris]

They could add some sort of 'saturation' tracker to recognize when the wheels could no longer provide control, and they could passively de-saturate over time (imagine magnetic torquers doing that bit). It would be equivalent to an overheat system, though without exploding upon saturation (technically, turning the opposite direction would also de-saturate the wheels, but that would be too troublesome to track).

...But honestly, I don't see such a mechanic adding to the game in a meaningful way. Just pretend they have limits and use them sparingly, if you really want.

For what its worth, I don't think a 'momentum saturation' should be added to the game (unless as an optional mod). Sizing momentum exchange systems correctly is a difficult problem, one of the key aspects in spacecraft design. Additionally, large vehicles like many manned spacecraft (ex. all US systems except for the ISS) use RCS alone because the size, weight, and power required for reaction wheels or CMGs is more than the required propellant for the 'short' durations of the mission and the vehicle is large enough that the minimum thrust is small enough to prevent limit cycling and other non-linear effects that hamper precision pointing.

What I would like for squad to implement is the ability to add more non-RCS torque capability to the vehicle that consumes electricity and has a significant weight penalty. Thus for short missions RCS is a better choice, but for long missions a CMG / RW package may be better.