[X] My Assistant

[djellison]

It's not that easy - a re-entry might be within a 5 hour window on any one of 3 orbits at any place along a 5000 mile track.

Doug

[nprev]

I wasn't too clear in my last post. What I meant was just a general international warning (NOTAM) for aviators that a reentry was likely in the next 24 hours would be sufficient without specifying location, as well as some training for them about the events (i.e., it may look close, but it probably ain't).

[nprev]

I thought boosters were supposed to depressurize to avoid this sort of thing.

Speaking of that, how is this usually done exactly? Do most boosters have valves somewhere on the fuel manifold that open up on ground command or via preprogramming, or are there dump valves directly connected to the tanks themselves?

I'm sure there are several different methods, just curious about how this is supposed to work. You obviously don't want them opening up during powered flight...

[dvandorn]

Rocket stages in a vacuum are usually vented through the engine bell(s). That way, you don't need to design any separate venting system; all you have to do is activate the proper pumps (the ones that feed the fuels to the combustion chamber during flight) and your fuel or oxidizer goes flowing out of the bell. (You could actually vent hydrogen and oxygen at the same time, though I don't think they do that all that often... hypergolics, of course, you vent separately.)

Yes, these vents can be somewhat propulsive, but not nearly as propulsive as when the engine is actually operating (i.e., when the fuel and oxidizer are undergoing combustion). Apollo S-IVBs were sent on their post-TLI trajectories (often designed to crash into the Moon) using, in part, the propulsive effect of their fuel and oxidizer venting.

-the other Doug

[nprev]

Ah...makes sense, thanks, DV. So then, failures to fully purge are usually caused by lack of power, pump failure, or I'd imagine some stray moisture freezing & plugging the outflow path? Should add comm link failure as well, apparently.