One issue that was primary for me is representative of the back-and-forth that the panel went through on many topics: The items astronauts would need for a longer stay would fill pages and include food, fuel, oxygen, energy, breathable air, some type of living quarters, roving equipment, and a return vehicle. Even if we counted on pre-supply missions, they would probably require a spacecraft of 30 to 70 metric tons. How could we possibly bring that much stuff to a stop at a precise location on Mars?
When the conversation turned to decelerating from supersonic speeds, the first item addressed was parachutes. In the group were two of the nation’s leading experts in parachute design. Juan Cruz, from the NASA Langley Space Center in Virginia, is a part-time professor at Georgia Tech and has a reputation as NASA’s best expert for supersonic parachutes and supersonic deceleration. He and I knew each other well, since he had worked on the chutes for Spirit and Opportunity and was deeply involved in the design analysis for the MSL parachute. We also had on the panel a longtime builder of Mars parachutes. Al Witkowski, of Pioneer Airspace, is one of the world’s most prolific designers of aerospace chutes.
Juan explained the fundamentals and design limitation of large supersonic chutes. He reminded us that the largest ever tested supersonically was about 85 feet in diameter. But the people who had been asked to do human Mars EDL simulations years earlier reminded us that they had done computer studies of simulated but much larger parachutes that would allow a human-scale lander to slow from somewhere just above Mach 3 down to less than Mach 1 over a few tens of seconds, but with a rather large back-breaking jerk as the parachute inflated.
Al and Juan just laughed. Juan told them, “We can’t scale parachutes up to the size of the Rose Bowl! Not without understanding the physics of parachute deployment and inflation of something that size. We can’t even say that the parachute will open in time before the lander hits the ground.”
I asked Juan, “Are you telling us we don’t have any parachute solution for going from supersonic speed down to subsonic speed for a large-scale lander?”
“That’s right,” he said.
The room went silent.
We created a subgroup to brainstorm various technology options to address the issue of slowing. Its members came back with an alphabet soup of possible technologies, but by then it was beginning to sink in: At this stage, none of the experts was able to offer a single effective way of slowing down.
We spent the last day brainstorming a schedule or timeline that we would need to solve the EDL problem and get it to the point that it would be usable for landing humans on Mars. We figured that, like the Apollo project, one or more Earth flight tests of bits and pieces of the full-scale EDL design would be required.
Although I was not a big fan of the idea, the team also assumed that we would at some point land at least one smaller robotic Mars mission to test some of the new technologies. When you stacked all of these up and counted forward, we calculated that the final EDL design concept would have to be ready by 2015. On that timetable, the first human footprints would not appear on the Martian soil until about 2032, and that would be if the project were funded soon.
Budgetary worries aside, in these fascinating workshops spread over six months, my human planetary roadmap team had created guidelines for dealing with some of the more challenging technical problems we’ll face in the effort to land humans on Mars. As an outcome of our efforts, some of the needed technologies are actually being developed right now.