Sunday, August 5, 2012

Can Mars Curiosity Rover Get It Done?

MSL Rover
Image of the Mars Curiosity Rover, set to land tonight on the Red Planet

After millions of miles traveling from Earth, $2.5 billion in costs (still barely a quarter of what the Afghan Occupation costs us each month), and five years planning to find the ideal site - the Mars Science Laboratory (nicknamed 'Curiosity') is slated for touchdown on Mars sometime this evening.

Ironically, the tension will arrive not from the long flight itself, but during the final approach, starting from an altitude of roughly 10 km (6 miles) when the two metric ton (2,000 lb. ) spacecraft deploys a parachute 50m (150') long and 21.5 m in diameter to begin its descent to the Martian surface.  This is critical because designing the chute was no easy task and even the experts (if honest) will admit that "the physics of how a parachute inflates at supersonic speeds is not well understood and extremely difficult to model" (Scientific American, July, 2012, p. 41).

Having descended to an altitude of 2 km (1.2 miles) the craft will be traveling at nearly 100 meters a second (330 ft/ sec) and that's using the parachute. This "terminal velocity" is the slowest the thin Martian atmosphere can brake an incoming spacecraft but still much too fast for a safe landing. Hence, this is the most critical point: the stage at which the craft needs to "drop  out" from the parachute and when a rocket powered backpack fires thrusters in the skyward direction, to slow its descent - ultimately to ~ 20 m/ sec. If at any time during this critical phase either the rover fails to separate enough from the chute or the thrusters fail to fire, it will be all over before it even starts. You will then read tomorrow morning or see tonight the news of a crash landing at 100 m/s.

Even this isn't enough for a slow enough landing to retain the delicate equipment, so in addition to the reverse thrusters, three cables will emerge (the "sky crane" so-called, at a height of about 20 m)  on which the rover will be gradually lowered. The end result (hopefully!) will be a "soft"  landing at 0.75 m/sec with wheels and suspension fully deployed. (But note even at this 'slow' speed, the momentum just before impact will exceed 700 kg m/s)  Meanwhile, the powered thrusters package will crash land roughly 450 m away.

It doesn't take a lot to see that failure could occur at any of these critical steps on the final approach to Mars. Needless to say, if even a minor failure occurs (say the suspension and wheels failing to deploy) NASA will have 'egg' all over its collective face, particularly as it elected to eschew working with the European Space Agency (ESA) to send collaborative missions in 2016 and 2018, opting to go it alone. The risks are enormous given the agency is eyeing further exploration of the Red Planet, and any kind of disaster would have serious repercussions in the eyes of the budget cutters. This will be especially so if the  Repugs get in power in November, and grab all branches of government.

Curiosity itself is the most technologically advanced craft ever - of the 6 to successfully land on Mars - out of the 14 total attempts made by all Mars-faring nations. The Rover (see image, compliments of NASA) is nuclear -powered and equipped with more than a dozen high tech cameras, a weather station and tools to drill, and 'sniff' the environment in search of life. Perhaps the neatest instrument is a laser-induced breakdown spectrometer which can zap holes in rocks and soil up to 7 m (21 ft.) away and remote sense their chemical composition.

The "rudimentary life form" optimists at NASA are keenly awaiting such tests, along with those from the 'SAM' or sample analysis device, because they believe the pre-selected landing site (Gale Crater) merits it.  Of 50 original candidates this was the one finally chosen based on a number of factors: including the exposure of ancient river deposits compliments of wind erosion over the ages, and mineral-rich terrain analogous to those on Earth which lie near groundwater aquifers. My own view is that despite all the shiny new toys, no life will be found - even microbial single-celled life. I simply don't believe any life exists on Mars, if it ever did.

Within an hour of its successful landing the Curiosity rover will commence its work, mainly getting some terrific imagery of the surface. Within another month and certainly by the end of the 2nd, barring mishaps, the onboard lab will have analyzed the first rock and soil samples.

Let us hope, for NASA's sake, and that of future exploration (including manned, since we can't stay on this one world forever) that this latest Martian endeavor turns out to be as big a success as its purveyors and creators are now hyping!

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