We recently had the pleasure of chatting with Miguel San Martin, chief engineer for Guidance, Navigation, and Control at NASA's Jet Propulsion Laboratory, where he has worked on four Mars spacecraft. On Twitter he's @MigOnMars.
In case you're just tuning in: On August 6 (it was still August 5 on the West Coast), the Mars rover Curiosity landed on Mars amid enormous celebration among space enthusiasts. The one-ton rover put its wheels on Mars through a complicated process known as "seven minutes of terror." A supersonic parachute and a sky crane had to be utilized in order to safely get Curiosity there. The mission cost $2.5 billion.
San Martin, who worked on Curiosity's landing system, spoke in November at the High Museum of Art in Atlanta at a special Holy Innocents' Episcopal School event called "Pushing Boundaries." We caught up with him before he gave an inspiring talk to students, parents and faculty about his career. Here is an edited transcript:
Light Years: What are you doing now that Curiosity has landed?
San Martin: We're doing three things: One, there's a lot of interest around it so I'm giving a lot of talks about Curiosity.
As far as my work at JPL, we are working - the whole team is working - on doing a reconstruction of the events that took place and how the landing on Mars worked.
The spacecraft was accumulating a lot of telemetry (data) that it couldn't send us because our Internet bandwidth is very low from Mars, right, so we cannot send all the information we are taking. So we accumulated it, so if you land successfully, and we did, we have this treasure of data that we've downlinked that tells us exactly how things progressed through the landing process, which is very important for us to design the next mission.
It tells if we got very close to failure, (so) we can fix that, or if we learn something that we did not know, and we got lucky, so we can fix that and make it better, or just simply say, "No, it worked this well." So it's very important, because we don't get to test the system here on Earth.
And also I'm working on a study, it's not a mission, on how to go to a comet and take a sample of the comet and bring it back to Earth. It's called Comet Sample Return.
Light Years: How was the Curiosity landing for you?
San Martin: It was a fun thing. Actually, we felt that people were watching, for the first time, because of the seven minutes of terror. Social media helped a lot to bring up awareness. This is my fourth Mars landing, and this was the first time it felt like we achieved actually something that we always wanted to do, which was: Come watch this thing! It might not work! This is exploration; you might see a moment of defeat, you might see a moment of triumph. They're both moments of life, so you should try to join us and be part of that.
In the past, people kind of felt that they found out the next day. They opened the paper: Oh, they landed on Mars! And they still got very excited. But I feel like this time there were more people who were part of the event.
Light Years: How long were you working on the Mars Science Laboratory/Curiosity before it landed?
San Martin: Eight years. So essentially I finished working on Spirit and Opportunity (the twin rovers in the Mars Exploration Rover, MER, program), and even during that time participated in a couple of meetings. Actually I believe, if I remember correctly, I'm pretty sure that the meeting that took place where we came up with the sky crane concept occurred before the end of MER. So a lot of us, the moment that we finished the Mars Exploration Rover mission that we landed, we moved onto MSL. That was in 2004.
Light Years: Did people think the sky crane idea was ridiculous?
San Martin: The lab (Jet Propulsion Laboratory) was divided between the people who thought we were total crazy nuts and then the people who thought, "Oh yeah, that's actually a pretty cool idea and it should work." I understood both types of people, because really to understand why it was a good idea, you needed to actually go through the whole intellectual journey, starting with Pathfinder and MER. So we didn't get there just in an instant.
Maybe when we ... started going to Mars in the '90s, when we put Pathfinder on Mars, if somebody had proposed that back then, we probably would have said no, that's not a very good idea. So we actually had to go through the experience of (landing rovers on Mars) and see how. Actually the problem was getting harder, because we were landing bigger rovers and bigger rovers.
Light Years: What did you think about the sky crane?
San Martin: I was one of the ones that right from the beginning thought it was a good idea. I did not invent it, you know, it was a group of people who said that would be an advantageous thing to do. I'm on the side of guidance, navigation and control, so I had to figure out how to control it during that time, so a lot of people looked at me in terms of, "Can we control such a thing, or it's crazy and it's going to go out of control and crash." So that was my contribution, to say, "Yeah, we can control it."
We have done similar things with the previous (rovers). The airbag landers actually have thrusters on top. People don't realize that. They were a different type of thruster, but some of the dynamics that we experienced were very complicated, in some ways more complicated, so that emboldened us to say yeah, we can do this.
And then you know a lot of very smart people said it would be advantageous to put the rover on the bottom (of the spacecraft) because then we can land it on the wheels. And the moment they said that, I said yeah, of course we can do that. So I was part of the beginning of the gestation of the whole thing.
Light Years: Do you think you'll ever use the sky crane again?
San Martin: Yeah, oh yes, I mean the sky crane now is a proven architecture. I think that all of the fears, a lot of people said that's very complicated, the fact that we didn't test it on Earth ... our argument was that it looks complicated, but actually the physics of the problem are pretty simple. And (in the) simulation we felt very confident. Now, the only thing missing from that argument was to actually try it.
And now we've tried it and we can say it looked easy and it was easy. And when I say easy, I mean not that it's cake, but simply that with a simulation you can prove (the system). You don't actually have to fire the rockets and do the whole thing. There are certain engineering designs and engineering architecture like the airbags ... you really need to test it in very similar environments, because we don't have the technology by simulation to feel comfortable that it's going to work.
So yes, we'll be using the sky crane again for these type of missions. There might be some other ones where things are small, where we might go back to the airbags just because of the cost issue. The sky crane requires good thrusters and good radars and that brings the cost up.