LCROSS wheat from chaff?

I was reading about the LRO/LCROSS launch on www.space.com. It was
saying that LCROSS will guide the Centaur upper stage into an impact
on the moon, which it will presumably watch until it too impacts on
the moon. My understanding is the idea is to scan the ejecta for
evidence of water.

That sounds all well and good to my peanut gallery brain, but then I
went over to the wikipedia entry for Centaur - it uses LH2 and LOX.
Does Centaur have facilities for a (verified) purge of the tanks before it
hits the moon? If not, aren't residual LH2 and LOX a concern wrt
"contaminating" their measuements?

rick jones
--
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Rick Jones wrote in
:


That sounds all well and good to my peanut gallery brain, but then I
went over to the wikipedia entry for Centaur - it uses LH2 and LOX.
Does Centaur have facilities for a (verified) purge of the tanks
before it hits the moon? If not, aren't residual LH2 and LOX a
concern wrt "contaminating" their measuements?

Yes; some Centaur missions leave the stage in a permanent high
orbit where it's desirable to purge the tanks in a controlled
manner. Just opening valves and letting the cryogens boil off
is essentially what happens. There's also a residual supply of
hydrazine for the ullage and attitude thrusters, and helium
bottles to vent.

LCROSS's own propulsion system will handle attitude and course
corrections. The stage won't impact for several weeks so there's
plenty of time to dump all traces of propellant into vacuum.

--Damon

Damon Hill wrote:
Rick Jones wrote in
:


That sounds all well and good to my peanut gallery brain, but then I
went over to the wikipedia entry for Centaur - it uses LH2 and LOX.
Does Centaur have facilities for a (verified) purge of the tanks
before it hits the moon? If not, aren't residual LH2 and LOX a
concern wrt "contaminating" their measuements?

Yes; some Centaur missions leave the stage in a permanent high
orbit where it's desirable to purge the tanks in a controlled
manner. Just opening valves and letting the cryogens boil off
is essentially what happens. There's also a residual supply of
hydrazine for the ullage and attitude thrusters, and helium
bottles to vent.

LCROSS's own propulsion system will handle attitude and course
corrections. The stage won't impact for several weeks so there's
plenty of time to dump all traces of propellant into vacuum.

--Damon


They explained exactly how this works with an animation during the
countdown. Here is a link to a replay of the video on Space-Multimedia

http://www.space-multimedia.nl.eu.or...s/replay41.php

Jim

Rick Jones wrote:
That sounds all well and good to my peanut gallery brain, but then I
went over to the wikipedia entry for Centaur - it uses LH2 and LOX.
Does Centaur have facilities for a (verified) purge of the tanks before it
hits the moon? If not, aren't residual LH2 and LOX a concern wrt
"contaminating" their measuements?


That's all supposed to be completly vented by the time it hits, a few
months from now.

Pat