Rosetta & Philae

[Ether]

Originally Posted by GrifBot

Philae bounced upon landing, (not surprised based off of the speed of the comet)

Please explain why you think the comet's speed was a factor in the bouncing.

[g_sawchuk]

Originally Posted by Ether

Please explain why you think the comet's speed was a factor in the bouncing.

Well, I'm not extremely educated in the means of how no gravity would effect this, but logically speaking, it would typically bounce or not smoothly land. Imagine a treadmill going on full speed. Imagine jumping on it. You will most likely fall and slide off. The higher you come from, you will also fall harder. Although the no gravity environment would change the Philae landing, I'm imagining that it would have some factor.

[JesseK]

Originally Posted by GrifBot

Well, I'm not extremely educated in the means of how no gravity would effect this, but logically speaking, it would typically bounce or not smoothly land. Imagine a treadmill going on full speed. Imagine jumping on it. You will most likely fall and slide off. The higher you come from, you will also fall harder. Although the no gravity environment would change the Philae landing, I'm imagining that it would have some factor.

There's a fairly good explanation and "simulation" here https://www.youtube.com/watch?v=GlMR...=TLU-o4vCFhIP0 for how Rosetta got into orbit and also learn some fun history.

The fact that the parent craft is in an orbit around the comet means that Philae was only moving at an orbital velocity relative to the comet. Since 67P's gravity is so low, we can deduce that the velocity required to orbit the comet is also quite low (relative to the comet, of course). Forget that they're moving umpteen thousand km/s around the sun - that's irrelevant for a landing from orbit.

To change your analogy, it's like you increased the speed of a neighboring treadmill that you're jumping from to match the speed of the treadmill you're jumping to prior to jumping. Getting into orbit around the comet is like running next to a moving train prior to jumping on it.

[protoserge]

Is it time to break out the orbital mechanics book?

http://en.wikipedia.org/wiki/67P/Chu...%93Gerasimenko
http://en.wikipedia.org/wiki/Rosetta_(spacecraft)


The term "no gravity" is a bit of a misnomer. Gravity is always present. Weightlessness is an effect of being in orbit. If the craft were to slow down, the object would de-orbit and be pulled toward the celestial body via gravity.

[Monochron]

Originally Posted by stinglikeabee

Is it time to break out the orbital mechanics book?

Probably just time to go play some Kerbal Space Program...

[Electronica1]

Originally Posted by Monochron

Probably just time to go play some Kerbal Space Program...

Yea, that game got me through AP physics (only person in my class to get a 5 on the exam).

[Alan Anderson]

After being "dropped" by Rosetta, Philae reached the surface of the comet traveling at about one meter per second. The 1 km bounce says a lot about the unexpectedly hard surface, but absolutely nothing about the orbital speed of the comet.