With a crane.
If NASA’s 2009 Mars Science Laboratory (MSL) reaches the red planet’s surface in one piece, the agency will owe a debt of gratitude to the Sikorsky S-64 Skycrane heavy-lift helicopter.
Like its namesake, NASA’s Sky Crane carrier platform will hover above its drop site—albeit with retrorockets rather than rotor blades—and lower its payload, the compact car-sized MSL rover, to the surface using a winch and tether. As soon as the rover is ready to roll, the tether connection will be severed and the Sky Crane will fly off and crash land a short distance away.
The MSL will be the first NASA mission to employ this planetary landing scheme, but it might not be the last. Adam Steltzner, lead engineer for MSL’s entry, descent and landing system at the Pasadena, Calif.-based Jet Propulsion Laboratory, said the Sky Crane approach makes sense for any destination where the terrain is not well understood or when it is especially important not to unduly disturb the landing site. Early lunar lander missions are one possible application, Steltzner said. Mars sample return missions are another, he said.
You can’t use a rotor on Mars because the atmosphere is way too thin, so they’re going to use rockets to hover while they crane down the MSL. If they manage to get it work, I will seriously send JPL a fruit-basket. Getting 3 or 4 rockets to fire simulatenously and at constant force to allow for a crane delivery of a vehicle, then have it disconnect safely, maneuver and crash land nearby is one enormous engineering feat. One reason the Sky Crane can do what it does is that the rotor is a single vector of upwards thrust, so you don’t have any directional components. But with rockets, if there is an imbalance, the whole thing could flip. You have to be incredibly precise with the thrust of each engine.
Good luck with that one, guys. I’m keeping my fingers crossed.