Angular momentum conserved!

[Goody1981]

I remember being somewhat disappointed years ago when I saw that unfolding solar panels did not slow a spinning craft due to conservation of angular momentum (the old spinning ice skater moving the arms etc etc).

So I am super impressed that with the new robotics parts it works beautifully. I just built a rotor with some pistons attached, with small fuel tanks on the edge of the pistons. Extended the pistons, spun up the rotor, disengaged the motor of the rotor so it was freewheeling (not sure if this was necessary) then retracted the pistons for a large increase in RPM. Very cool.

This is probably obvious to many, since KSP is a physics simulator, but it’s still cool to see it model something not because it’s been specifically programmed to in that one instance, but because it’s just programmed to obey the laws of physics. Made my day

[Gargamel]

Completely pointless (at least for my game play, IRL has many applications) but utterly cool.    I'll have to try this.

[Xavven]

6 hours ago, Gargamel said:

Completely pointless (at least for my game play, IRL has many applications) but utterly cool.    I'll have to try this.

I wish we could get ropes and cables so we could build yo-yo despin mechanisms  (and pulleys but that's another topic!)

[Bill Phil]

6 hours ago, Gargamel said:

Completely pointless (at least for my game play, IRL has many applications) but utterly cool.    I'll have to try this.

Not actually pointless, at least in real spaceflight.

You see, in many situations when a solid motor is used as an upperstage, a certain part of the craft is spun to high angular speed. Then when the motor is finished with the burn the vehicle performs a de-spin maneuver using "yoyos" that are released and still connected to the vehicle, flying outwards to slow its rotation. 

Not as useful to us KSP players but definitely useful for real spaceflight.

[Guest]

yer, i noticed the change in spin while playing around with a collapsible robotic solar array. Was a nice little bit of realism  

[Cydonian Monk]

Now if only it was conserved through timewarp....

[Snark]

Moving to Breaking Ground Discussion

[Geschosskopf]

If you mess around with autogryos, you'll quickly discover angular momentum is not conserved in all cases.  But hey, some is better than nothing

[Terwin]

I expect the big problem with parts like solar arrays is that the center of mass did not move when the deploy animation ran, so no effect on angular momentum would be expected.

I would be curious about which cases do not preserve angular momentum @Geschosskopf, are they primarily cases where the actual(as opposed to apparent) mass does not move, or are there cases where masses are clearly moved but do not affect the core object?

[Geschosskopf]

2 hours ago, Terwin said:

I expect the big problem with parts like solar arrays is that the center of mass did not move when the deploy animation ran, so no effect on angular momentum would be expected.

I would be curious about which cases do not preserve angular momentum @Geschosskopf, are they primarily cases where the actual(as opposed to apparent) mass does not move, or are there cases where masses are clearly moved but do not affect the core object?

Braking the co-ax, counter-rotating rotors of an autogyro after landing.  The whole point of having co-ax rotors is to balance out things like this.  However, the braking animation seems to play in only 1 direction, even though neither has a motor and are just free-wheeling.  The result is that 1 rotor instantly reverses direction and the fuselang absorbs the combined momentum of both, flipping over.  You could say that the the final outcome is the conservation of angular momentum but that leaves out the instant sign change before, which kinda violates conservation.

 

[Goody1981]

On 6/12/2019 at 5:15 AM, Terwin said:

I expect the big problem with parts like solar arrays is that the center of mass did not move when the deploy animation ran, so no effect on angular momentum would be expected.

I’m sure you’re right with regard to it being just an animation and there is no mass moving, but (and I might be wrong here) the centre of mass doesn’t have to move right? You would still get the effect if symmetrical panels mounted exactly in line with the centre of mass were unfolded?

[Terwin]

2 hours ago, Goody1981 said:

I’m sure you’re right with regard to it being just an animation and there is no mass moving, but (and I might be wrong here) the centre of mass doesn’t have to move right? You would still get the effect if symmetrical panels mounted exactly in line with the centre of mass were unfolded?

Sorry, I was referring to part COM, not vessel COM.  You do need the mass to spread out from the center for the angular momentum to reduce the RPM, even if the vessel COM stays the same.

[Goody1981]

Ah yeah cool gotcha

[AHHans]

On 6/8/2019 at 10:27 AM, Gargamel said:

Completely pointless (at least for my game play, IRL has many applications) but utterly cool.

Just wait till someone builds a catapult powered by this.

 

On 6/8/2019 at 4:40 PM, Xavven said:

I wish we could get ropes and cables so we could build yo-yo despin mechanisms  (and pulleys but that's another topic!)

Have you tried making a yo-yo despin with a chain of motorless hinges? I imagine that would work.

[Xavven]

4 hours ago, AHHans said:

Have you tried making a yo-yo despin with a chain of motorless hinges? I imagine that would work.

Good idea! I was also thinking about trying pistons. It's on my to-do list.