When people look at it, uh, 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 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.
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 thirteen thousand 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.
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, sixteen hundred degrees. During entry, the vehicle is 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 constrained place. This is one of the biggest challenges that we are facing, and one that we have never attempted on Mars.
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 a thousand miles an hour. So at that point we use a parachute. The parachute is the largest and strongest super-sonic parachute that we've ever built to date. It has to be able to withstand sizty-five thousand pounds of force, even though the parachute itself only weighs about a hundred pounds. When it opens up that fast, it's a neck-snapping 9G's.
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.
This big huge parachute that we've got, will only slow us down to about two hundred miles an hour. That's not slow enough to land. So we have no choice that 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 gonna smack right back into the parachute!
So the first thing we do is make this really radical "Divert Maneuver". We 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.
We can't get those rocket engines too close to the ground. Because if we were to descent propulsively, our engines all the way to the ground, we would essentially create this massive dust cloud. That dust cloud could then go on land on the rover. It could damage mechanisms, and it could damage instruments. So the way we solve that problem, is by using the skycrane maneuver.
Twenty meters above the surface, we have to lower the rover below us on a tether that's twenty-one feet long. And then gently deposit it, on its wheels, on the surface. As the rover touches down and is now on the ground, the descent-stage, is 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.