THREEPIO: Sir, the possibility of successfully negotiating an asteroid field is approximately 3720 to 1!
HAN : Never tell me the odds!
Threepio's comment may be an example of how mathematics can be misleading. The odds he quoted may be those of a spaceship travelling straight through the asteroid field. (Robots tend to think linearly.) Fortunately Han and the Millenium Falcon can STEER, avoiding the biggest asteroids. Let us hope that people in science learn to think outside the box.
Earlier this year asteroids were the subject of a series of posts. In many ways an asteroid mission is easier than reaching the Moon, January 22. The DAWN mission will explore two of the largest asteroids, January 23. The lines between asteroids, comets and minor planets are becoming more blurred, January 24. In 2029 Apophis will pass closer to Earth than a communications satellite, January 29. A "gravity tug" could be used to deflect dangerous asteroids, January 30.
Last week the private company Digital Space released video of a notional asteroid mission. Darnell of Colony Worlds has posted the whole video here. Once a spacecraft achieves Earth escape velocity, reaching an asteroid is relatively easy. Unlike the Moon, there is no deep gravity well to descend into. A Orion spacecraft could virtually hover over an asteroid using thrusters. Digital Space envisions a landing craft based upon Lunar Surface Access Module designs. The spacecraft could "hop" from one landing site to another. The lower stage is designed to be left behind as a science station.
Check out those big old spacesuits! Using skintight suits could save 600-1200 pounds from the mission weight. When astronauts are ready to return home, the bulky outer layers could be left behind with the lower stage. Asteroids are probably dusty, and all that dust would be left behind too.
Concerning thrusters,Orion is still going through redesigns. As with many projects, weight is a growing problem. Like Apollo, Orion will now use hypergolic propellants for the thrusters. To save the mass of airbags, Orion is now planned to splashdown in the ocean. I hope they realise that the US has fewer aircraft carriers than in the 1960's. The Orion 3 unmanned mission is scheduled to land off the coast of Australia in September 2012. Watch out for the box jellies, and we'll put another shrimp on the barbie for you.