June 22, 2012

Engineers who designed the entry, descent and landing system for NASA's Mars rover Curiosity candidly talk about the new landing system, and describe the challenges of Curiosity's final moments before touchdown on Aug. 5, 2012, at 10:31pm PDT.


Adam Steltzner: When people look at it... uhhh, it looks crazy. That's a very natural thing. Sometimes when we look at it, it looks crazy. It is the result of reasoned, engineering thought. But it still looks crazy.

From the top of the atmosphere, down to the surface. It takes us seven minutes. It takes 14 minutes or so for the signal from the spacecraft to make it to Earth that's how far Mars is away from us.

So, when we first get word that we've touched the top of the atmosphere, the vehicle has been alive... or dead, on the surface, for at least seven minutes.

Tom Rivellini: Entry, descent and landing, also known as EDL, is referred to as the '7 minutes of terror'. Because we've got literally seven minutes to get from the top of the atmosphere to the surface of Mars going from 13,000 miles an hour to zero, in perfect sequence, perfect choreography, perfect timing and the computer has to do it all by itself, with no help from the ground.

If any one thing doesn't work just right, it's game over.

Adam Steltzner: We slam into the atmosphere and develop so much aerodynamic drag, our heat shield, it heats up and it glows like the surface of the sun. 1600 degrees!

Miguel San Martin: During entry, the vehicle is not only slowing down- violently, though the atmosphere, but also we are guiding it, like an airplane to be able to land in a very narrow, constrained space. This is one of the biggest challenges that we are facing, and one that we have never attempted at Mars.

Tom Rivellini: Mars - it's actually really hard to slow down, because it has just enough atmosphere that you have to deal with it otherwise, it will destroy your spacecraft. On the other hand, it doesn't have enough atmosphere to finish the job. We're still going about 1000 miles an hour. So at that point we use a parachute.

Anita Sengupta: The parachute is the largest and strongest super-sonic parachute that we've ever built to date. It has to withstand 65,000 pounds of force! Even though the parachute itself only weighs about 100 pounds.

Tom Rivellini: When it opens up that fast, it's a neck-snapping 9G's!

Steve Lee: At that point we have to get that heat shield off. It's like a big lens cap, blocking our view of the ground to the radar. The radar has to take just the right altitude and velocity measurements at just the right time or the rest of the landing sequence won't work.

Tom Rivellini: This big huge parachute that we've got it'll only slow us down to about 200 miles an hour and that's not slow enough to land. So we have no choice but we've got to cut it off! And then come down on rockets. Once we turn those rocket motors on if we don't do something, we're just going to smack right back into the parachute!

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