[X] My Assistant

[Phil Stooke]

I am starting a new thread for this mission which should fly this year.

Phil

[mcaplinger]

Without a schematic of the propulsion system, it's really difficult to intuit what may be happening. Having done a little digging, apparently even the ACS thrusters are biprop (MMH doesn't work as a monopropellant, the spacecraft I'm familiar with that used dual-mode monoprop/biprop used pure hydrazine.)

Normally the large pressure gradient between the helium tank and the rest of the system would prevent any migration back into the helium tank, but if the pressure is equalized then all bets are off. Systems that aren't so mass-constrained have one-way check valves to keep migration from happening anyway (see Figure 1 in https://www.researchgate.net/publication/23...ion_Performance ) but it seems that Peregrine cut out anything that wasn't absolutely required.