Failed Russian space mission shows difficulty of exploring Mars
The Phobos-Grunt spacecraft launched from Russia this week destined for Mars has yet to leave Earth orbit – and looks increasingly likely to tumble back to Earth with its full tanks of toxic fuel.
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In the end, engineers tend to lay awake nights worrying not as much about the systems they've checked a dozen times as the so-called unknown unknowns – serendipitous combinations of system failures that can tank a mission but only become slap-the-forehead moments after they happen.Skip to next paragraph
Even then, clever engineers can often devise work-arounds. McNutt cites NASA's highly successful Galileo mission to Jupiter as an example. During Galileo's cruise phase, engineers commanded the craft's high-gain antenna to unfurl. This was the antenna the craft would use to beam large volumes of data from the science instruments to salivating mission scientists back on Earth.
But the antenna failed to deploy. Speculation regarding the cause centered on the antenna's lubricants evaporating en route to Jupiter.
During the craft's seven-year cruise to Jupiter, engineers were able to compensate by reprogramming the craft's computers to compress the data and by installing more sensitive receivers at tracking stations on the ground. This allowed the team to use the orbiter' less-capable low-gain antenna both for keeping track of the spacecraft's health and for returning research data.
When it comes to the Russian space program, it clearly has had significant successes, McNutt notes. In human spaceflight, the country is providing reasonably reliable transportation for US and Russian crews to and from the International Space Station (ISS) as a bridge to US commercial crew flights to low-Earth orbit expected later this decade.
And while US planetary scientists have struggled to come up with a cost-effective mission to explore Venus, Russian missions to the second rock from the sun "have knocked the ball out of the park," he says. "Most of what we know about the surface of Venus comes from Russian data."
Which makes Russia's 0-fer at Mars a puzzle. The physics involved in getting there are the same, regardless of flag. Russia has a stable of reliable rockets. And Russian engineers are likely to be just as motivated to succeed as any other county's rocketeers.
McNutt speculates that the challenges revolve largely around money and priority. Since the end of the cold war, Russia's space program has struggled for cash, prompting its entrepreneurial foray into space tourism, for instance. US purchases of seats on Soyuz capsules to and from the space station represent another source of badly needed revenue.
Tight budgets not only reduce the number, if not the ambition, of space-exploration missions. They can also shrink investments in the engineering infrastructure needed to support the design and construction of new space probes that do receive approval, McNutt explains, recalling the Mariner 3 failure.
Phobos-Grunt reportedly was using a usually reliable upper stage for putting the craft in its trajectory to Mars. But the stage reportedly had been modified for the mission, potentially turning a less-expensive, off-the-shelf solution into an inadvertent prototype.
As for NASA's Mars Science Lab? Landing will be a thrill. The mission is using an approach for putting a rover on Mars NASA has never used before. No air bags; the rover is too big and heavy. Instead, the lander wears its descent module like an exhaust-spewing cap.
When the module descends to about 25 feet above the surface, the module will lower a bridle carrying the lander, much like a Sikorsky Skycrane helicopter lowers cargo while hovering. Once the lander's wheels touch down, the bridle's tethers are released, the descent module rockets away from the lander, and the lander is free to roam.
The approach was dictated by the rover's size and weight, explained Pete Theisinger, the mission's project manager, during a recent press briefing to preview the launch.
The lab is too big and heavy for air bags, and driving it off a descent module underneath the rover would be cumbersome and complicate.
"That would be a daunting, daunting thing to do," he said.
The various components that make up the system have been thoroughly tested, he said. But he acknowledged that the package hasn't been tested as an integrated system.
"We've done our due diligence. Mars may interfere with us, or there may be something we haven't caught" he continued. "But to the extent we've been able to think of it, we've attacked all the problems and done all the testing we can do."
Here's to a well-lubricated tether release.