Reaction Torque for EVA Kerbals

[Red Iron Crown]

13 minutes ago, SchweinAero said:

Are you sure it works in a vacuum?

No reason it shouldn't, it's not using air resistance to rotate. You would agree that a reaction wheel can reorient a craft with no residual wheel speed as long as angular momentum is the same before and after the maneuver, no? Think of your arms and legs as a reaction wheel with only about 180 degrees of rotation and it makes more sense how it is possible.

It would be tricky to do in an EVA suit due to less flexibility though.

6 minutes ago, swjr-swis said:

This one maybe (check at 5:45):

<snip>

@Red Iron Crown, this the one you meant?

It is indeed, thank you.  Guess I was misremembering it being on Skylab rather than the shuttle.

[ZooNamedGames]

4 minutes ago, swjr-swis said:

This one maybe:

 

It's seeing stuff like this, that reminds me why I loved the space program. They're all a bunch a goofballs up there  . Most people don't know astronauts past the suit, but I'm glad we do  .

As to our discussion, you can see in the video that they can adjust their rotation whilst free floating without needing another object to push off of.

[swjr-swis]

1 minute ago, ZooNamedGames said:

As to our discussion, you can see in the video that they can adjust their rotation whilst free floating without needing another object to push off of.

They can, to a limited degree. It would be very hard to use that to impart a significant force on another object though, like enough to flip a rover. It's an awful lot of effort just to rotate themselves 90 degrees...

[SchweinAero]

2 minutes ago, Red Iron Crown said:

No reason it shouldn't, it's not using air resistance to rotate. You would agree that a reaction wheel can reorient a craft with no residual wheel speed as long as angular momentum is the same before and after the maneuver, no? Think of your arms and legs as a reaction wheel with only about 180 degrees of rotation and it makes more sense how it is possible.

It would be tricky to do in an EVA suit due to less flexibility though.

I see it now. Well explained. That is not what @ZooNamedGames meant then, is it?

[The_Rocketeer]

2 minutes ago, ZooNamedGames said:

As to our discussion, you can see in the video that they can adjust their rotation whilst free floating without needing another object to push off of.

I'm not seeing this. Every time they change their attitude they seem to be in contact with a rigid surface, or still in a tumble from having let go. Perhaps you can give specific timestamps to check?

[swjr-swis]

1 minute ago, The_Rocketeer said:

I'm not seeing this. Every time they change their attitude they seem to be in contact with a rigid surface, or still in a tumble from having let go. Perhaps you can give specific timestamps to check?

The drill at 5:45. They are close to the floor, but if you look closely you'll see they are not actually touching it. They can't bem because the wild leg movements would bounce them off in the direction of the ceiling.

[eddiew]

16 minutes ago, ZooNamedGames said:

Why wouldn't it? If I were to put my hands on my toes and then throw them up above my head and behind me, the force I would be apply would put me into a spin without needing to touch anything. Vacuum or not.

In my mind, putting your hands on your toes in microgravity results in your toes coming up as much as your arms/torso go down. Flinging your arms 'up' then gets countered by your legs going back 'down' and you're back where you started.

You might end up changing orientation (as per video above), but you can't go into a lasting spin without having pushed on something because you haven't applied a force to anything, you've just bent and unbent. To create a permanent spin, you need an external object to push on.

[swjr-swis]

1 minute ago, eddiew said:

You might end up changing orientation (as per video above), but you can't go into a lasting spin without having pushed on something

Look at the drill again. By the end of it, the astronaut in the back (sorry, I can't remember his name right now) is actually in a slow spin now, having started at full standstill.

[Red Iron Crown]

1 hour ago, swjr-swis said:

Look at the drill again. By the end of it, the astronaut in the back (sorry, I can't remember his name right now) is actually in a slow spin now, having started at full standstill.

They both appear to have picked up a small bit of angular momentum, probably from their gyrations interacting with the air. I don't think that would happen in vacuum as it's a net angular momentum change.

[ImmaStegosaurus!]

21 hours ago, ZooNamedGames said:

Spoiler

Lately I've had this realization in my head that Kerbals are way physically under powered compared to humans. Specifically, humans can impart force on a craft they are on, whether this be leaning, pushing or pulling on it. By doing these actions they impart torque on it. 

 

Reaction wheels get saturated with torque over time and you'll need RCS or similar force to reset them. Running around spacecraft would rotate it but once you stop, you'll cancel out what was just done.