Comments on: Two Space Robots To Crash Into Moon Monday

By: Ken

Ken — Tue, 18 Dec 2012 17:27:59 +0000

Because the exact amount of fuel remaining aboard each spacecraft is unknown, mission navigators and engineers designed the depletion burn to allow the probes to descend gradually for several hours and skim the surface of the moon until the elevated terrain of the target mountain gets in their way

By: Joffan

Joffan — Fri, 14 Dec 2012 20:11:21 +0000

Goodbye, Ebenezer and Florence Grail, and what a great mission. As usual far more than the minimal science achieved. I’m sure LRO will be checking out your impact site, too.

By: Michael Kelsey

Michael Kelsey — Fri, 14 Dec 2012 18:46:28 +0000

“Whut?” Yes, I have the same question, as the comment as stated is absurd. Impact in a shadowed region “should” make for better visualization, since any explosion would not be washed out by sunlight.

However…the craft will be impacting with empty fuel tanks, by design, so there won’t be an explosion, just a rather quiet thud. Pity.

By: Eric Lund

Eric Lund — Fri, 14 Dec 2012 14:53:39 +0000

De-orbiting satellites at the end of the mission is now something NASA routinely does. They don’t want to clutter up the orbit with space junk, and in the case of the Moon they don’t want to take the admittedly small risk of having the satellites crash into a previous landing site. (Similarly, they prefer any sizeable chunks of de-orbiting Earth satellites to land in the ocean, rather than on land where they might hurt somebody.)

By: daedalus2u

daedalus2u — Thu, 13 Dec 2012 22:09:01 +0000

I think also they want to empty the fuel tanks because the fuel can be nasty. It uses hydrazine, and catalytically decomposes it into N2 and H2.

At the poles it is cold enough for hydrazine to freeze-out and potentially contaminate any ice or other low boiling point materials that might be there; complicating potential recovery and interfering with measurements.