Quote:
Originally Posted by pluto
Rosetta is not orbiting the comet, it's orbiting the Sun in an almost identical orbit as the comet, though it will enter orbit around the comet in a few months. The comet will reach it's maximum speed of 135,000 km/h at perihelion and so will Rosetta. Both the comet and spacecraft are travelling much slower than that now.
135,000 km/h is faster than the maximum speed of the Voyagers (Voyager 1 max speed was 62,136 km/h but it's comparing apples with oranges. The Voyagers are technically not in orbit around the Sun, having exceeded escape velocity.
If the Voyagers were moving a bit slower, so that they were still orbiting the Sun, and if they had a similar perihelion to Rosetta then they would be travelling significantly faster than Rosetta when they reached perihelion.
Likewise to raise Rosetta's speed at perihelion to escape velocity would require adding many km/s to it's velocity.
So while Rosetta will achieve a faster top speed, relative to the Sun, the Voyagers/Pioneers/New Horizon have more orbital energy.
This spaceflight is amazing and full of "firsts" but it really relies on tried-and-tested propulsion technology and gravitational assists. 
P.S. I think 135,000 km/h is 37.5 km/s which I get as 0.000125 %c, however maths was never my strong suit  |
thanks Hugh,
that and the discussion with Julian does help me understand it better. 67P has so little gravity that even at 1 m/sec or walking speed they are anchoring Philea to the comet in case it bounces off.
any ideas on why most craft travel at that 16-17 km/sec.?
and with the propulsion and slingshot technology what is the best time we could do the Proxima C. run in?
and yes i embarrassingly missed a 0 in my /hour to /second conversion but then you forgot the "and x by 100 to get %" after the division by the speed of light. so it is .0125%. Just proves 2 heads are better than one . . . us north islanders have these problems!!