Friday, December 5, 2014
Wednesday, December 3, 2014
Thursday, November 20, 2014
Last week the ESA's Rosetta mission successfully landed the Philae probe onto the surface of Comet 67P/Churyumov–Gerasimenko. Philae bounced several times before finally landing on the side of a cliff. A gentle reminder that for more critical missions which require landing, there is real virtue in having an actual human pilot at the controls.
The total number of bodies in the solar system we have successfully landed anything on intact now stands at seven; the Moon, Venus, Mars, Titan, the asteroids Eros and Itokawa, and comet Chury-Gery. We have returned samples only from the Moon, and asteroid Itokawa.
The next big robotic exploration destination will be when the Dawn spacecraft reaches Ceres next spring. I'm inclined to think that the Dawn Ceres data will be a game-changer in how we prioritize our upcoming human space exploration missions. As such, we'll be following it closely, here.
Friday, November 14, 2014
This is a previously classified video about the US Army's nuclear powered under-ice facility in Greenland, called Camp Century. It didn't work very well, because the Greenland ice sheets were far more mobile than had been previously understood. But the techniques used here could be adapted to Ceres, Europa, or Enceladus. Note however the enormous logistics that were required to make this happen.
Sunday, November 9, 2014
So, if I translate this for a colonization mission to Mars, in order to build any permanent colony of any size at all (on Mars, or the moon, or really anywhere) then I need my rockets to leave earth, land on Mars, leave Mars and then land back on earth, in more or less the same configuration it took off in. This is reasonable, but unfortunately this is not, to date, the way spaceflight has been able to work.
If we look at the Apollo/Saturn V moon landings as a baseline of the physics needed to send and return humans to and from another world, it is apparent that in order to reach space and return from it, a spacecraft must almost continually shed excess weight. Saturn V stood some two million kilograms on the launch pad, whereas the Apollo command module which ultimately splashed down weighed maybe a thousand kilograms. This is sloppy, expensive and wasteful, but it is the only way to get a payload of this size into space with current technology.
Tsiolkovsky's rocket equation;
in which the weight of the rocket and fuel at the beginning of the launch and at the end of the launch must not exceed the effective exhaust velocity of the rocket. With existing propellants, it is nearly impossible to lift a payload of any real size even to low earth orbit with only a single rocket stage.
So, almost certainly, the first spacecraft to land humans on Mars will be of this Saturn V-type design, either SLS/Orion, or something very much like it. For exploration missions, this is fine, albeit expensive. The advantage is, we already know how to do this. For a colonization mission, the spacecraft are going to need to be much more like a 747, as far as re-useability. Elon Musk is going to want his rockets back, so he can use them again. Simply piling up hardware on the Martian surface, or at the bottom of the Atlantic, is a lousy business model.
SpaceX has already developed a vertical takeoff and landing rocket prototype, called Grasshopper. It is elegant, but burns lots and lots of heavy propellant to be able to control its landings. It is noteworthy that to date, no SpaceX cargo rocket to the ISS has actually utilized this technology, opting instead for multistage rockets and parachute descents. Adding the fuel weight for a Martian descent and surface escape launch, and still having the delta-v to reach orbit, is challenging at best. But necessary, if Martian colonization is going to be available to anybody but the very, very wealthy.