Quote:
Originally Posted by geolindon
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?
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It really depends on the mission. Of course the speed is linked to the orbit the object is on. For example the Earth is travelling faster than Venus, relative to the Sun, but Mars is travelling faster than the Earth.
This page has a good comparison of the 5 spacecraft currently on escape trajectories:
http://www.heavens-above.com/SolarEscape.aspx. You can see that the craft have very different velocities so they're not all around 16-17km/s.
How long it would take to Proxima Centauri depends on a lot of things. But just for the sake of discussion let's assume it's a small spacecraft that we can accelerate to 20km/s, which would be realistic using traditional chemical propellants. In this case it would take about 63000 years to reach our nearest neighbour system.
If you really wanted to do this though, and you were still happy to wait many generations you could employ existing ion propulsion with some kind of long term power generation (most likely nuclear fission or thermal for smaller stuff). then you could potentially accelerate to much higher speeds.
Then there are also solar sails which could get you moving even faster but these have only had small scale, short duration tests and, while very promising, are still in need of more research to make them viable.