Date: June 28, 2012
Title: Curiosity Rover: Seven Minutes of Terror
Podcaster: Mat Kaplan
Organization: The Planetary Society
Links: Planetary Society: http://planetary.org, National Air and Space Museum: http://airandspace.si.edu
Description: Curiosity, the Mars Science Laboratory Rover, arrives at Mars late at night on Sunday, August 5. That’s when an incredible seven minutes of drama begins, as the spacecraft must slow from 13,000 miles per hour to zero in a fascinating and terrifying sequence of precisely choreographed actions. You’ll hear JPL engineers dramatically describe this harrowing end to an interplanetary journey in today’s podcast.
Bio: Mat Kaplan is the Planetary Society’s Media Producer. He has also hosted and produced Planetary Radio, the Society’s award-winning weekly podcast and public radio series about space exploration and development, for nine years. The show presents the men and women who are leading our push into the final frontier, along with regular contributions from Bruce Betts, Emily Lakdawalla, and Planetary Society CEO Bill Nye the Science Guy. Catch it on a local radio station, Sirius XM Satellite Radio, in the iTunes Store, or at http://planetary.org/radio . With this return to 365 Days, Mat and the Society kickoff a monthly contribution on the last Thursday of each month in 2012. (With the exception of August, when it will be heard on Thursday the 23rd.)
Today’s Sponsor: This episode of 365 days of Astronomy is sponsored by iTelescope.net – Expanding your horizons in astronomy today. The premier on-demand telescope network, at dark sky sites in Spain, New Mexico and Siding Spring, Australia.
Transcript:
Seven Minutes of Terror: The Entry, Descent and Landing of Curiosity, the Mars Science Laboratory Rover
Mat Kaplan: Hello again, podcast fans. I’m Mat Kaplan of the Planetary Society, where I host our own radio show and podcast, Planetary Radio. My intent this month was to bring you a quick interview about Curiosity, the Mars Science Laboratory rover. I wanted to share the seemingly nuts way it is designed to descend from space to the surface of Mars, and do it in just seven minutes. But nothing I could have come up with would have equaled the thrill and excitement of a video the Jet Propulsion Lab has already created about exactly this subject. You’ll definitely want to see the video itself, and we’ve provided the link, but the soundtrack all by itself is, well, amazing. It’s like a really good radio drama from the 1940s or 50s. You think I’m exaggerating? Let’s see if you still feel that way after you hear it, and here we go.
Adam Steltzner, EDL Engineer: When people look at it, uh, it looks crazy! It’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. The top of the atmosphere down to the surface, it takes us seven minutes. It takes fourteen 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, EDL Engineer: Entry, descent and landing, also known as EDL, is referred to as the seven 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: When we slam into the atmosphere we develop so much aerodynamic drag our heat shield, it heats up and it glows like the surface of the Sun. 1,600 degrees.
Miguel San Martin, EDL Engineer: During entry, the vehicle not only slowing down violently through the atmosphere, but also we are guiding it, like an airplane, to be able to land in a very narrow constraint e. This is one of the biggest challenges that we’re facing, and one that we have never attempted on Mars.
Tom: Mars is 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 a thousand miles an hour, so at that point we use a parachute.
Anita Sangupta, EDL Engineer: The parachute is the largest and strongest supersonic parachute that we’ve ever built to date. It has to be able to withstand 65,000 pounds of force, even though the parachute itself on weighs about 100 pounds.
Tom: When it opens up that fast, it’s a neck-snapping nine gs.
Steve Lee, EDL Engineer: 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: This big, huge parachute that we’ve got, it will only slow us down to about 200 miles an hour. That’s not slow enough to land. So, we have no choice but we’ve gotta cut it off, and come down on rockets. Once we turn those rocket motors on, we don’t do something, we’re just gonna smack right back into the parachute. So the first thing we do is make this really radical diverting movement. Fly off to the side. Diverting away from the parachute, killing our horizontal velocity and our vertical velocity. Getting the rover moving straight up and down so it can look at the surface with its radar, and see where we’re going to land. And we head straight down to the bottom of a crater, right beside a six kilometer high mountain.
Anita: We can’t get those rocket engines too close to the ground, because if we were to descend propulsively with our engines all the way to the ground, we would essentially create this massive dust cloud. That dust cloud would then go and land on the rover. It could damage mechanisms and it could damage instruments. So the way we solved that problem is by using the Skycrane.
Tom: Twenty meters above the surface we have to lower the rover below us on a tether that’s 21 feet long and then gently deposit it on its wheels, on the surface.
Miguel: As the rover touches down and it’s now on the ground, the descent stage, it’s on a collision course with the rover. We must cut the bridle immediately, and fly the descent stage to a safe distance from the rover.
Mat: Was I right or was I right? I bet you, like me, were picturing all that in your mind. Now you can go see the real thing. And another thing you can do is join us at Planetfest 2012, Curiosity Knows No Bounds. It’s the Planetary Society’s two-day celebration of this mission, ending late Sunday evening with that nail-biter of a landing on our big screens in Pasadena, California. You can learn more at planetary.org/Planetfest. That’s planetary.org/Planetfest, where Bill Nye the Science Guy will welcome you with a video. You’ll also be able to join the party through our live webcast, or possibly at a Planetfest event near you. That’s Planetfest 2012, Saturday and Sunday, August 4 and 5. Thanks for listening. I’ll be back on Thursday, July 26 with another 365 Days contribution from the Planetary Society. Clear skies.
End of podcast:
365 Days of Astronomy
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