It might seem an unlikely topic for a Java convention, but NASA Aerospace Engineer Dr. Anita Sengupta’s keynote talk on “Engineering the Red Planet” was well received by a crowd of technically minded software engineers. After all, who wouldn’t want to hear from someone who was part of the team that successfully landed Curiosity on Mars?
That was a feat that required half a million lines of code. And it all boiled down to what happened in the final few minutes of the descent—the time required for the capsule to hit the edge of Mars’ atmosphere and complete the treacherous descent to land the rover safely on the surface of the planet. The visuals accompanying Dr. Sengupta’s address showed the harrowing flight in great detail, stage by stage. “It takes you seven minutes to get from the top of the atmosphere down to the surface of the planet. We created a wonderful video called ‘Seven Minutes of Terror’ which shows the challenges of landing something on a planet so many millions of miles away.”
Taking Curiosity down to Mars
First, the capsule’s heat shield came into play, bravely protecting the Curiosity from the scorching heat generated by friction with Mars’ thin atmosphere. This portion of the entry process slowed the capsule from a shocking 30,000 miles per hour to a modest 1,000 miles per hour. Of course, this was still far too fast to make a safe landing. The heat shield was stripped away and a giant parachute deployed to provide additional drag on the rocket. Yet the massive surface area of the chute was still not enough to slow the packaged down to a safe landing speed.
Next, the chute was released and retro rockets were activated to quickly divert the capsule away from the parachute and then provide propulsion away from Mars’ surface at a rate that slowed the package down even more. However, the rockets could not approach too close or they would kick up excessive dust and damage the delicate rover equipment. For the last 60 feet, the rover was lowered on several long tethers by a Sky Crane to gently touch the dusty surface at a rate of just 2 miles per hour.
Because of the time delay of 14 minutes for communication between the spacecraft and the Earth-side team, the rover had already reached the surface by the time the first image of the capsule reaching the planet’s outer atmosphere came through. The engineering crew waited with bated breath to discover whether or not all their hard work and careful calculations had paid off, or if they had just crashed a 2.5 billion dollar robot into smithereens. When they finally received the first image of Mount Sharp from Curiosity’s cameras, they knew all was well.
This “Seven Minutes of Terror” was quite a riveting story, rivaling any science fiction movie. NASA’s Jet Propulsion Lab even has a Java-based web simulator called Eyes on the Solar System that allows online users to relive the experience at will.
What’s on board a rover?
The suite of instruments on board Curiosity is broad ranging and complex. The technology to explore the Martian environment includes chemical evaluation, imaging, weather tracking, radiation measurement, a drill, scoop, brush, and sieve, equipment to detect subsurface hydrogen, and even a laser to vaporize rocks and analyze the spectrographic results. The information gleaned from these instruments is made public as it comes in and is freely available on the web to anyone with an interest in exploring the red planet from the comfort of their living room. The Curiosity team is particularly interested in tracking weather patterns including temperature, wind, and pressure and how they correlate with fluctuating levels of radiation throughout the day/night cycle and season to season. This data will go a long way toward determining the challenges that might face a manned flight to Mars or long-distant terraforming efforts.
Curiosity also includes sophisticated guidance and navigation systems. There is no way to remotely control the rover live from Earth because of the time delay. This means that the day’s route is determined in advance commands are uploaded in the morning and evening. The flight software in the loop coupled with the diagnostic system on board allows the rover to operate itself, avoiding surface hazards like cliffs and rocks.
Why go to Mars in the first place?
For those driven by more practical concerns than pure curiosity, this is the obvious question. It’s a long, long way from home. Yet, as Dr. Sengupta pointed out, the third and fourth rocks from the sun actually have much in common. They were formed at the same time and both have mountains, canyons, and moons. . “We now believe that Mars did have an atmosphere, a thick atmosphere and appreciable water flowing on the surface.” Something happened that changed Mars, and it may be worthwhile to figure out what that was.
Now that frozen subsurface water deposits and seasonally flowing surface water have been discovered on Mars, there is more reason than ever to explore this planet as a potential arena for colonization. Since it is relatively close compared to planets circling other stars, it would also serve as the first true proving ground in humankind’s quest to spread out into the universe.
Of course, even if the red planet was made habitable, there’s still the really big question, “Do we want to become Martians?” It’s a decision that would impact future generations in unimaginable ways. Dr. Sengupta revealed the sobering truth: it’s a one way ticket. “Kids born on Mars could not go back to Earth. They would not be able to survive in the Earth’s environment.” The gravity that is comfortable to the typical human would be an insurmountable obstacle for a native born Martian. Yet, in the end, as with all great human endeavors, it is our choice.