I believe somebody has already landed on an asteroid, either taken samples or impacted something into it. So I don’t think it is extremely difficult making the rendezvous and matching speeds. I just meant to point out that the dynamics don’t always let you land somewhere just because you’re able to get there. If you do rendezvous with another solar system object, and you plan to do it at a relative velocity slow enough to do something other than crash into it, it is probably at only one place and time. And it may be very far away and way in the future.

I say this because you often hear people say things like

“Asteroid X comes within a million miles of earth every year or so, we should be able to fly there, land, and tour the solar system aboard it, and then jump off and come home next time it approaches earth.”

It doesn’t work like that. When its near earth it may be moving so fast relative to us that matching speeds would be highly energy-expensive. On the other hand, a transfer orbit that meets it on the other side of the solar system a year or two later may be fairly cheap energy-wise. Of course, in order to come home, you may have to stay there a long time, and your trip home won’t start when its near earth.

As I recall, the cheapest trip to Mars takes nine months, the trip back takes the same, and you have to stay there over a year for the alignment to be right to come home. You can do it in less time, but it will cost you.

The Chinese have had ambitious space plans even talk of crashing into a asteroid to divert its orbit and would like to be in the league of Japan’s landing on Hayabusa along with Nasa’s Near landing on Eros. With this encounter of Toutatis Beijing will surely to build on its confidence.

Years away, oh yeah, many and it will probably be other objects.

Their probe passed the asteroid at a relative velocity between the two of almost 11 km/sec. That it very close to Earth’s escape velocity. It would have taken as much delta-vee to slow down and rendezvous with the object as it took to launch the probe off the earth’s surface. There is probably a place and time in both earth’s and Toutatis’ orbits where and when a launch could be arranged so that an orbital match could be achieved very economically. But the the mission might take years, and the encounter might actually occur on the other side of the solar system from us.

It isn’t that difficult energy-wise to rendezvous with solar system objects, but matching speeds with them is very difficult. And it makes no difference whether you’re climbing out of or falling into the Sun’s gravity well, it takes as much energy to speed up as it does to slow down.

One of the posters was asking if anybody knew of a popular elongated island 2 2/2- 3 miles long. The first thing that came to mind was: The China Syndrome-Three Mile Island.

Nice work of the Chinese spacecraft extended mission. A good exercise for possible mining explorations down the road.