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View Full Version : Achieving helio-centric, earth-trailing orbit?



schlaugh
2009-Mar-19, 07:17 PM
I understand that Kepler and Spitzer are in Earth-trailing orbits. Got that. My question: what does the launch and orbital profile look like for such a placement? What speeds need to be achieved, and what (or where) is the insertion point?

I assume that an object placed into an earth-trailing orbit must be accelerated to about 29 km/s and then perhaps a bit more so that the object would eventually drift behind and beyond Earth's orbit. But darned if I can find any details on the NASA site or elsewhere on the interweb.

Larry Jacks
2009-Mar-19, 07:48 PM
You can read about Earth-trailing orbits here (http://www.planet4589.org/space/misc/sirtf/sirtf.html).

cjameshuff
2009-Mar-19, 07:59 PM
I assume that an object placed into an earth-trailing orbit must be accelerated to about 29 km/s and then perhaps a bit more so that the object would eventually drift behind and beyond Earth's orbit. But darned if I can find any details on the NASA site or elsewhere on the interweb.

It's already moving at 29-some km/s before it even launches. You just need to get it beyond the point where Earth's gravity dominates over the sun's, and nudge it into a slightly longer-period heliocentric orbit. Slightly less than Earth escape velocity should accomplish this, about 11 km/s delta-v from the ground, most of which goes into lifting the craft out of Earth's gravity well.

http://kepler.nasa.gov/sci/design/orbit.html

schlaugh
2009-Mar-20, 01:17 AM
Thanks folks, much appreciated. What Larry posted is what I was looking for cjames, but you are right, the object is already moving at Earth orbital speed and which I had managed to overlook. :doh: