Messenger to Mercury
I was stuck in traffic yesterday afternoon. The upside to this was hearing NPR's story on, among other things, why it takes so long (i.e., eight years) for a spacecraft to land on Mercury:
[Maria] Zuber says the answer is gravity. Mercury's orbit is closer to the sun than the Earth's, and if you launch a rocket toward the sun, the sun's gravity is going to cause your spacecraft to speed up.
So ... [Messenger] used the gravity of other planets to slow it down with respect to the sun. In a trajectory worthy of Rube Goldberg, Messenger looped once around the Earth, then made two close encounters with Venus. When it arrived at Mercury in 2008, it was still going too fast, so it flew by Mercury three times, slowing down a little more each time. "The fourth time it came by Mercury it was slowed down enough that when we fired the main engine, Mercury's gravity field was able to capture it," says Zuber. Messenger has been orbiting Mercury since March 2011.
I need to remember this story the next time I'm taking six detours to get from A to B.
This entry was originally posted at http://zirconium.dreamwidth.org/8999.html.
[Maria] Zuber says the answer is gravity. Mercury's orbit is closer to the sun than the Earth's, and if you launch a rocket toward the sun, the sun's gravity is going to cause your spacecraft to speed up.
So ... [Messenger] used the gravity of other planets to slow it down with respect to the sun. In a trajectory worthy of Rube Goldberg, Messenger looped once around the Earth, then made two close encounters with Venus. When it arrived at Mercury in 2008, it was still going too fast, so it flew by Mercury three times, slowing down a little more each time. "The fourth time it came by Mercury it was slowed down enough that when we fired the main engine, Mercury's gravity field was able to capture it," says Zuber. Messenger has been orbiting Mercury since March 2011.
I need to remember this story the next time I'm taking six detours to get from A to B.
This entry was originally posted at http://zirconium.dreamwidth.org/8999.html.