** I still get a little nervous about venting methane straight overboard -
I'm trying to avoid a 'delta iv' like situation where a cloud of methane is
ignited upon engine start that could potentially damage GSE or the raceways
on the vehicle. Has this ever been a problem with similar
amateur/collegiate methane rockets or am I being too paranoid? *
My SDSU students vented the methane directly overboard during filling ops.
No flares involved. We did intentional design methane & LOX vents on
opposite sides of the vehicle in case we needed to suddenly depressurize
the vehicle. Granted this is not a guarantee that no mixing could occur,
but seemed wise.
That being said, if you look at the following video, you can see a large
amount of gaseous methane present outside the engine at ignition starting
around 17:02 on the time stamp.
https://www.youtube.com/watch?v=K3a16jAo0FQ&t=24s
The methane and LOX ball valves were opened simultaneously and the methane
had to prime the motor regen passages, so we fully expected LOX to be
present first. During the methane filling ops there was no sign of a leak
(visual, audible or smell… we used LNG which does have a smell). Maybe the
gaseous methane just flowed faster through the plumbing & regen passages
than the cold GOX.
--- Carl
