Martian cliffhanger resolved at last

Did NASA cut corners on engine testing?
Back in the 1990s, as a cost-cutting measure, Polar Lander's engines were never actually tested. Instead, they were certified purely on the basis of previous flight experience. In the “circle-the-wagons” embarrassment that followed Polar Lander's loss, NASA officials admitted the error but refused to reveal which space vehicle had carried such thrusters in the past.

At the time, there were rumors that the engine was used for a military multiple-warhead carrier mounted on an intercontinental ballistic missile. As such, the engine would be qualified to start up in a warm underground silo, for a mission of no more than 30 minutes ending in nuclear annihilation. The idea that this would be "close enough" for use on a chilly 10-month flight to Mars seemed preposterous — but no one would confirm the rumors.

That was then, and this is now: Lewicki said he had no problem discussing Polar Lander's engine.

“It’s a standard Aerojet engine, model MR-107-N,” he happily told me when asked. “Before it flew on MPL, it had flown on intercontinental ballistic missiles.” Its predecessor, the MR-107, had also flown in an upper stage for the small Athena satellite launcher in the 1990s, the Encyclopedia Astronautica Web site notes.

Bill Smith, executive director of the Aerojet plant in Redmond, Wash., that builds the company's in-space rocket engines, confirmed that this was the engine model involved in both the Polar Lander and Phoenix. "It's the same engine," he said in a telephone interview with msnbc.com late Friday. "It's been used on a number of satellite launch vehicles."

Smith didn't think the cold engine posed a problem for Polar Lander. "After the loss of the lander, we ran ignition tests all the way down to -40 degrees F," he told msnbc.com. "The engine started up and worked just fine." He believes Polar Lander was felled by the premature shutdown.

‘We won't have liftoff ...’
Now that Phoenix Mars Lander's engines are shut down, they'll stay shut down. That means the lander is doomed to be frozen in place during the dark, cold Martian polar winter ahead. Phoenix will become encased in carbon dioxide ice for months, ruling out any prospects for further operations.

So why not "take off" at the end of the mission? Why not keep some fuel around to burp the engines briefly, rise a few meters, and then come back again a short distance from the original site? This would permit observation of the depressions caused by the landing pads and the scouring effects of the engines, and would provide stereoscopic views of portions of the horizon to help determine the distance to nearby features.

This is exactly what the Surveyor 6 moon probe did in 1967. It performed the first-ever launch from the lunar surface on Nov. 17, 1967, when it rose 13 feet (4 meters) above the surface and then landed 8 feet (2.5 meters) from its original landing spot.

The temperature makes a big difference. Surveyor's hop came only eight days after its initial landing, and the tanks had stayed warm in full sunlight. Phoenix, in contrast, is expected to operate in place for months amid frigid conditions. For safety's sake, it's better to dump the fuel. Once this Phoenix alighted on Mars, there would be no rising from the flames or the frost.

The propulsion system's last gasp probably came less than an hour after landing, when the final bit of helium gas hissed out of the dump valve into Mars' thin atmosphere.

The gas coming out of the propellant tank may have had minute traces of hydrazine that seeped through the bladder wall. It might have been enough, Lewicki imagines, to create a spray of small hydrazine snowflakes across the surface, a thin white hoarfrost that would quickly evaporate even at polar temperatures. It would leave behind nothing — nothing, that is, but a spacecraft safely on the surface, delivered by a propulsion system that was awakened from the dead and then died peacefully again.

This is an updated version of a report that was originally published on May 23, 2008.

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