NASA’s Curiosity Rover landed on the surface of Mars on Monday, August 6 and the event was described as “seven minutes of terror”. Forbes reports that much was at stake during those seven minutes, including a $2.5 billion investment, years of effort, and hopes of keeping a cash strapped nation interested in the future of space exploration.
The technology behind the descent could be summarized in several basic categories that include heat shielding, a slowdown, the “Transformer” phenomenon, Rover separation and the “sky crane”. According to Information Week, the craft is about the size of an SUV at 14.8 feet (4.5 meters) in diameter and it weighs about 6,950 pounds (3,152 kilograms).
The Heat Shielding
The Curiosity craft had to be shielded from heat that built up during the slamming descent through the atmosphere. The craft’s shielding is called the Aeroshell. The top forms a rounded pod that looks like a metal lampshade, and the base and is a honeycomb arrangement of special materials that looks like a lens. The Aeroshell proved itself capable of protecting the craft and its innards from temperatures that reached 2,100 Centigrade, or 3,812 Fahrenheit.
Inside the shell, the Rover stayed at between 32 to 77 degrees Fahrenheit or 0-25 degrees Celsius, which was a comfortable range. The heat shield has an instrument called MEDLI that was designed to record valuable descent parameters that will be of use in planning future landings.
The heat shielding also served as part of the “braking” system by cutting the kinetic energy by 90 percent. This process cut the speed from 13,200 miles per hour to 1,000 miles per hour, or 5.9 kilometers per second to 0.45 kilometers per second.
The Center of Mass Move
Two solid tungsten weights were deployed. Each weight was about 165 pounds (75 kilograms) and the weights were the size of a laptop computer. These weights shifted the spacecraft’s center of mass. Small thrusters gave even more control to decrease the size of the landing zone. With the thrusters, the craft was able to negotiate a series of “S” curves through the atmosphere instead of going straight in.
The Hypersonic Aero Maneuvering
This is a complicated concept that is based in the Curiosity’s design. The craft now behaved like a kind of “aircraft wing” that creates life. But this “wing” was flying at the incredible speed of Mach 5. The fastest fighter jets only travel at around Mach 2. At Mach 5, air molecules break apart. Hot plasma forms and surrounds the spacecraft. Then there is air compression, various waves form and the craft is buffeted around. This was the most treacherous part of the landing mission.
The Slowdown
After the hypersonic phase of the landing, the parachute deployment had to work. Curiosity’s parachute was 7 miles above the surface and headed downward at Mach 2, which is 900 miles per hour or 405 meters per second. The parachute slowed the craft to 9 percent of it’s original speed when it entered the atmosphere.
Curiosity had gone through a massive slowdown process that took the craft from 13,000 miles per hour to Mach 0.7. This is about 310 miles per hour or 140 meters per second.
The “Transformer Phenomenon”
Curiosity went through five or six unique and very exciting physical changes that resembled the way that the “Transformer toys and film robot characters make their transformations.
First, the heat shield at the bottom of the capsule separated and whisked away. It was much like removing a camera lens cap. Curiosity now had a clear view of the land beneath it, which allowed the bottom cameras to start filming.
The radar system also went into operation. Pictures and videos were not enough to tell how close the land was getting.
The back shell separated and flew away. Curiosity was no longer completely contained like a pea in a pod. The retro rockets fired, allowing the exposed rover to move away from the back shell and the huge parachute so they would not all land together.
Rover Separation, Mobility Deploy and “The Sky Crane”
This is an image of the “Sky Crane”.
The craft was going 1.7 miles per hour or .75 meters per second. Four of the eight retro rockets were shut down. The “Sky Crane” deployed. This was a combination of three nylon ropes that created a bridle, and an “umbilical cord” that spooled out. The cord was 25 feet or 7.5 meters long.
The cradle and “umbilical cord lowered Curiosity to a height of about 66 feet, or 20 meters above the surface.
The craft was at about 12 seconds before touchdown when Curiosity’s wheels and suspension system deployed and locked into place. The suspension system was also the landing gear.
Touchdown
The craft touched down, perhaps with a little “bounce”. Then, something very interesting happened!
The Flyaway
The Cradle and the Umbilical Cord actually detected that they were no longer needed, so they detached, picked themselves up and flew away! The flight carried the rather large mass of equipment to a distance of at least 490 feet or 150 meters from the rover.
The Final Form of the Mars Rover
Now the rover is in its final configuration and it looks quite different than it did when it left the Earth. This is a model of the Curiosity Rover in its final form.
For an excellent explanation of the process, visit NASA’s website to explore along with the Rover.
This is a map of Curiosity’s “harrowing arrival”.
