Mars orbiter faces NASA’s ‘Ghoulish’ past

Swallowed whole by the Ghoul?
The 1993 loss of Mars Observer is similarly shrouded in myths and half-truths. This is the probe that suddenly disappeared just short of arriving at Mars, according to the modern folklore. Weird theories about hostile space forces, phantom meteor swarms and even government cover-up conspiracies have been wrapped around this mishap.

Mars Observer, of course, never "disappeared" at all. It just stopped sending radio signals, which was the only way controllers back on Earth could know what was happening. And the timing of this silence was a crucial clue to what had gone wrong. It fell silent on Aug. 21, 1993, just three days before it was due to enter Martian orbit.

This was just after small explosive bolts had been fired to pressurize the rocket thruster fuel tanks that would be used in the braking rocket burn. The probe's transmitter had been commanded off because it was feared that the impact of the small detonations might break the heated cathode in the radio's amplifier.

In hindsight, investigators concluded that the failure most probably was caused by the inadvertent mixing and the reaction of nitrogen tetroxide and monomethyl hydrazine within the titanium pressurization tubing. These two chemicals are hypergolic propellants, designed to explode spontaneously when mixed in a rocket chamber. If mixed somewhere else, they explode with equal enthusiasm but less happy results.

NASA Mars Observer, shown in this artist's conception, was lost in 1993 — apparently because a cost-cutting measure led to problems with its fuel pressurization system.

The explosive fuel was supposed to have been safely isolated inside a pair of tanks, but the valve seals probably leaked. Based on tests performed at the Jet Propulsion Laboratory, the review board concluded that "an energetically significant amount" (NASA talk for "enough to blow up") of the nitrogen tetroxide had gradually leaked through check valves and accumulated in the tubing during the spacecraft's 11-month flight to Mars.

The report especially criticized NASA for relying on hardware originally designed for near-Earth missions. To save money, NASA tried to redesign a Pentagon spacecraft that had been built for launching into geostationary Earth orbit. The original mission called for a six-hour rise to orbit, not the almost yearlong cruise needed to get to Mars, and was therefore "fundamentally different from the interplanetary Mars Observer mission," the report said.

The idea of saving money by reusing similar-looking space hardware is a fallacy based on the mistaken impression that the costliest component of a spacecraft is the materials of which it is made. The biggest cost is actually the human effort required to verify that all parts work together properly and to make sure the reliability levels of all the components and combinations of components stays high enough. Thus, using a short-lived fuel tank valve that has to last 1,000 times longer than the lifetime for which it was designed will ultimately cost far more, take far longer, and be less safe.

In 1993, NASA learned that lesson from Mars Observer's death. Then, in 1999, the loss of Mars Climate Orbiter taught space engineers that making convenient safety assumptions and taking budget-driven shortcuts would cost far more in the end.

Happily, the team that built Mars Reconnaissance Orbiter were smart enough to incorporate these lessons from the start, with plenty of ground tests, independent reviews and stringent reliability standards. The Ghoul could still strike, of course. But if it does, it won't be because NASA has forgotten what it learned from those past orbiter failures.

Sadly, the public remains largely in the dark about the lessons from Mars — which, after all, can be applied to earthly matters as well as space shots. If you check NASA's online postmortem on Mars Climate Orbiter, you'll learn only that "engineers concluded that the spacecraft entered the planet's atmosphere too low and probably burned up." For Mars Observer, the text reads that "the mission ended with disappointment on August 22, 1993, when contact was lost with the spacecraft shortly before it was to enter orbit around Mars."

Taxpayers paid for these lessons, too, and NASA needs to share them more openly and more thoroughly.

NBC News space analyst James Oberg spent 22 years at NASA's Johnson Space Center as a Mission Control operator and an orbital designer.

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