The Mars Landing Approach: Getting Large Payloads to the Surface of the Red Planet
Nobody knows how to do it.
Surprised? Most people are, says Rob Manning the Chief Engineer for the Mars Exploration Directorate and presently the only person who has led teams to land three robotic spacecraft successfully on the surface of Mars. "It turns out that most people aren't aware of this problem and very few have worried about the details of how you get something very heavy safely to the surface of Mars," said Manning.
...
But what about airbags, parachutes, or thrusters that have been used on the previous successful robotic Mars missions, or a lifting body vehicle similar to the space shuttle? None of those will work, either on their own or in combination, to land payloads of one metric ton and beyond on Mars.
...
The major conclusion that came from the session was that no one has yet figured out how to safely get large masses from speeds of entry and orbit down to the surface of Mars. "We call it the Supersonic Transition Problem," said Manning. "Unique to Mars, there is a velocity-altitude gap below Mach 5. The gap is between the delivery capability of large entry systems at Mars and the capability of super-and sub-sonic decelerator technologies to get below the speed of sound."
Plainly put, with our current capabilities, a large, heavy vehicle, streaking through Mars' thin, volatile atmosphere only has about ninety seconds to slow from Mach 5 to under Mach 1, change and re-orient itself from a being a spacecraft to a lander, deploy parachutes to slow down further, then use thrusters to translate to the landing site and finally, gently touch down.
...
The air is so thin that a heavy vehicle like a CEV will basically plummet to the surface; there's not enough air resistance to slow it down sufficiently. Parachutes can only be opened at speeds less than Mach 2, and a heavy spacecraft on Mars would never go that slow by using just a heat shield. "And there are no parachutes that you could use to slow this vehicle down," said Manning. "That's it. You can't land a CEV on Mars unless you don't mind it being a crater on the surface."
...
Supersonic parachute experts have concluded that to sufficiently slow a large shuttle-type vehicle on Mars and reach the ground at reasonable speeds would require a parachute one hundred meters in diameter. "That's a good fraction of the Rose Bowl. That's huge," said Manning. "We believe there's no way to make a 100-meter parachute that can be opened safely supersonically, not to mention the time it takes to inflate something that large. You'd be on the ground before it was fully inflated. It would not be a good outcome."
В общем, получается, что технологий посадки на Марс больших, тяжелых аппаратов просто не существует. Пока.
