Apollo CSM RCS Fuel Consumption: Manual vs. V49

[Wedge313]

Good morning,

Killing some time while performing the Apollo 7 PTC test. This is a question I should have asked a long time ago....

When maneuvering the CSM to an attitude, which method would use the least RCS fuel? Manually or using V49?

I ask because when I'm using V49 to maneuver, my RCS seems to work against itself a lot of the time. It tends to make a lot of small pulses bracketing (I assume) the rate I've selected in the DAP, for instance pulsing the roll clockwise toward the selected attitude, then taking some of the rate out, then putting some back in etc. This goes on in all three axis. I would guess this frequent chattering in all three axis would use a lot of RCS propellant unnecessarily? Whereas if I maneuver manually, I can pulse the RCS once in the direction I want to roll (or pitch or yaw) and then wait as the spacecraft maneuvers.

V49 is nice, it takes the headwork out of a maneuver and all you have to do is watch out for gimbal lock. Just curious which method used the least fuel.

Thanks

 

[rcflyinghokie]

I think it depends on many things especially how far you are maneuvering, your rate of maneuvering, and maintaining deadband as you stated. Those small pulses are pretty much the shortest interval the RCS can fire, smaller than the RHC unless you use minimum impulse I believe so that give V49 a little advantage. They used a mixed bag early on to check this as well. I will see if I can find some consumption charts but again they should be similar in consumption for the same maneuver assuming you are going the same direction, maintaining same rate etc.

Are you using rate command for the manual maneuver? If so you should be able to generate similar results.