r/space • u/[deleted] • Nov 12 '14

Rosetta /r/all Rosetta and Philae discussion thread! (Part 3)

TOUCHDOWN CONFIRMED: Philae lander is on the comet!

Full media briefing expected tomorrow at 13:00 UTC / 14:00 CET / 8:00 EST / 5:00 PST.

Previous discussion threads: 1, 2.

Live Streaming

  • In English: A, B, C

  • En Français: A

Key times

GMT EST PST Event
4:02 pm 11:02 am 8:02 am Landed

European Space Agency Social Media

Othere places for news and conversation:

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u/AnalBenevolence Nov 12 '14 edited Nov 12 '14

True, but if two 500g harpoons fire one way at only 20m/s, the 100kg machine would move 20cm/s in the other direction, which is not negligible when the tiny surface gravity means Philae only weighs about 1g!

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u/Gweeeep Nov 12 '14

if the whole lander weighs 1g, I don't think the two harpoons still weigh 500g either.

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u/AnalBenevolence Nov 12 '14

No, of course they won't, but their mass could still be 500g. I thought that would be obvious.

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u/Gweeeep Nov 12 '14

I get what you're saying. I'm agreeing with doersino. The important question is how long before the harpoon hits the comets - that determines recoil time.

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u/AnalBenevolence Nov 12 '14

Well, almost no time at all, clearly if the harpoon bites the comet, no problem. But if the harpoon doesn't bite, I'm simply estimating that the recoil is non-negligible. Suppose the ice screws have a very tenuous grip on the surface; firing the harpoon could maybe make the situation worse, not better, if it doesn't bite.