Rosetta's stone

Monday 17 November 2014


Exciting news about the Rosetta space probe meeting up with 67P/Churyumov–Gerasimenko. I saw a picture of how big the comet is compared to a city and it seems to be about the size of a mountain, this interested me as I didn't think the gravitational field would be big enough to make it possible to orbit it. Anyway I looked up some data

67P/Churyumov–Gerasimenko

Mass = 1013 kg
Radius about 3 km

Orbit radius = 30 km

Assuming the orbit is circular:

fraction numerator G M m over denominator r squared end fraction equals fraction numerator m v squared over denominator r end fraction space space v equals square root of fraction numerator G M R over denominator r end fraction end root space equals square root of fraction numerator 6.67 space cross times 10 to the power of minus 11 end exponent cross times 10 to the power of 13 over denominator 30 cross times 10 cubed end fraction end root equals 0.15 space m s to the power of minus 1 end exponent

That's a pretty slow orbit. A time period of 14 days.

I tried setting this up in Interactive Physics by zooming out so that the scale was about 1 cm : 1 km. I think I achieved an orbit but its slow slow you can hardly see the motion. The trail you see in the image is about an hours worth. Just goes to show, you can orbit anything if you go slow enough.

Searching for more information I found the Rosetta blog with this video of the orbits.

I left the simulation running overnight and got the following confirmation that an orbit has been achieved. Now this would be a good investigation topic. In the video above you can see that when Rosetta first met the stone it didn't orbit but did several fly bys.

Why rEEsearch?
23 Nov 2014
Who can say Huygens?
12 Nov 2014