Chair Force Engineer

Sunday, October 12, 2008

Mars: From Surface Lab to Sample Return

Rocket Man has an interesting piece about the problems encountered by the Mars Science Laboratory program, which threaten to end the next Mars science mission before it even gets off the ground.

When I first read about the SkyCrane descent method, it seemed pretty needlessly complex in my view. How long would the "flying bedstead" need to sustain a hover in order to lower and free the science rover? How do you ensure a clean separation as the "flying bedstead" flies away from its rover? The concept could work, but it adds a lot of risk to the mission that I don't think is necessary.

Instead of pursuing MSL, Rocket Man proposes spending its budget on built-to-print copies of the Spirit and Opportunity rovers. Such a move would give NASA-JPL a reliable means of investigating multiple sites of scientific interest on the Red Planet.

But I would take the idea one step further, and tie the "multiple rovers" concept into the long-anticipated mission to robotically return soil samples from Mars. While a single Sample Return mission would have scientific value, the expensive Sample-Return mission could provide a much greater science return if multiple areas on the Martian surface could be sampled.

Conceptually, using several copies of the Spirit/Opportunity rover to grab soil samples for return to earth is an excellent idea. The problem is getting all of those samples back to earth. At the pace the rovers travel, they'd have to be landed fairly close to the rocket that will lift off from the Martian surface to bring the samples back to earth. This would defeat the purpose of having multiple rovers for a sample return mission.

Alternately, each rover could be delivered to the Martian surface with its own ascent vehicle. Bigger ascent vehicles could return to earth independently, increasing the chances that at least one Martian soil sample will make it back to earth. A more complex design would use smaller ascent vehicles, and make them rendezvous with a mother-ship in Mars orbit.

In closing, the successes of the Spirit and Opportunity rovers in exploring Mars should serve as the basis for future exploration efforts. Unfortunately, Mars Science Lab discards many of these proven concepts and systems in favor of a high-risk SkyCrane approach. If SkyCrane does not work out, JPL should seriously consider a return to the Spirit/Opportunity rover design, and perform science missions with an armada of simple, cheap rovers instead of a single, expensive rover. The "constellation of rovers" approach to science missions may be the best way to ensure the success of Mars Sample Return.