The New Horizons spacecraft approaches Pluto...

[Vandal]

[SpacemanSpiff]

This is a great accomplishment, but it seems a shame to spend nine years getting there and just whiz past into nothingness. I wonder why they didn't design it to go into orbit, or at least crash into the surface. Maybe that would have required too much mass for fuel and propulsion systems.

Real simple - no brakes.

I'm not sure what orbital velocity around Pluto would be (Earth's is about 17,500 MPH, and I think the Apollo craft orbited the moon at something less than 3000 MPH, and Pluto has about 70% of the moon's mass, so you can figure something less than that), but braking a craft from 36,000 MPH into a parking orbit would require some serious rocket power.

Dragging this from the archives to introduce an article about how far away Jupiter is -- and how it's a lot harder to stop than it is to do a fly-by (unless you're a gangsta rocket, in which case it would be a drive-by... )

http://www.universetoday.com/128259/lon ... t-jupiter/

Remember, this is a planet that has a big hunk of gravity to help slow things down -- or provide a nice slingshot.

So, if you’re going to do a flyby, you’ll need about 550-650 days to make the journey.

But if you actually want to slow down and go into orbit around Jupiter, you’ll need to take a much slower journey. The only spacecraft to ever stick around Jupiter was NASA’s Galileo spacecraft, which launched on October 18, 1989.

Instead of taking the direct path to Jupiter, it made two gravitational assisting flybys of Earth and one of Venus to pick up speed, finally arriving at Jupiter on December 8, 1995. That’s a total of 2,242 days.

There's a new probe, Juno, that's about to hit Jupiter's orbit and stay awhile. That one will take 1795 days, having launched back in August 2011.

So, given the nine years it took for the New Horizons craft to get there, image how long an orbiter would take!