Distances in space can seem unfathomable. Each planet comes with a different set of mathematical challenges. The gravity of Jupiter is so huge that it’s slowly tearing its moons apart via tidal forces, for example, while Mars is so small it’s barely holding onto its own atmosphere.
Even if they were in the exact same spot, getting a probe to the moon is going to be wildly different than getting one to the atmosphere of Mars. Orbital physics are so incredibly complicated that it’s a miracle anything makes it anywhere at all! And yet, we’ve landed things on Mars, on the moon, on Venus, on asteroids – and technology makes it just a little easier every time.
Unfortunately, the Mars Polar Lander was not one of those times. It thought it had already touched down with its landing equipment and shut off its engines. It was actually so far away that engine-less impact with the ground destroyed it, about four months after the loss of the Mars orbiter. Talk about an unfortunate year for Mars projects!
Mars Orbiter
This lander was supposed to work in tandem with the Mars orbiter. Unfortunately, that had burnt up in the atmosphere earlier that year. Luckily, the teams in charge of the Mars Polar Lander had already designed multiple redundancies into the system, and it could still send messages back to Earth without the orbiter. It was disappointing to have lost their communications relay, but not world-ending. The sheer number of telecommunication devices built into this robot make its totally preventable death sting worse, but NASA (at the time) was struggling with its chain of command and funding – the lander had to work, or else…
Or else leadership was wrong, and the issues were upper management, not lower.
New initiatives meant that some of the work was being outsourced to the lowest bidder, which – once again – was Lockheed Martin. It’s important to note that in the orbiter’s case, the only thing that killed it was that metric-to-imperial conversion. If it had handled that, there’s no reason to believe the construction would have failed. The same goes for this lander: as far as we know, the issue was a software issue, not a construction one.
Falling Out of the Sky
Once again, the lander was supposed to lose communications as it got into position to land and reconnect afterwards, just like the orbiter. Entry went fine, as far as anyone could tell! The lander didn’t burn up in the atmosphere, or get shaken to pieces, all the equipment was intact – everything was going perfectly fine. Right up until a software bug stopped its thrusters too early, and it hit the surface of the planet at extreme speed. It was carrying two probes with it that were designed to hit the planet at about 200 meters/second, and those didn’t survive the crash either. That’s how fast the thing was going when it hit the ground!
At least, that’s what they think happened. The lander’s communications were interrupted by landing, as planned. All NASA had was their previous tests, which did their best to simulate landing on the surface of the planet.
What (Theoretically) Happened?
The propulsion system was only supposed to stop once it detected a signal from the legs, which would only send that signal once it had touched down. However, one of the legs was sending out bad signals, and the lander shut off its main engines prematurely. It misinterpreted the drag and jostle of moving the legs into position as coming into contact with the surface of the planet.
Once it was sending the signal, it would continue to send it. The machine couldn’t correct itself, and other sensors for location (like the Sun and star trackers) weren’t of much use so close to the planet’s surface. Testing had shown this could happen, but they hadn’t expected it to – it was a bug in the code itself, and it didn’t happen every time. Some say the test sensors were wired incorrectly, but this is a theory and not something NASA verified.
The bug was noticed, and obviously they should have fixed it when they could. However, fixing it would have been a huge undertaking, and NASA was in a hurry to get this thing out the door. They hedged their bets against it happening. Little bug + lot of work to fix it = ignoring the issue.
Much like the Challenger’s O-ring failure, if they’d had the complete picture, they might have held off on launch. Nobody with the authority to delay wanted to, and nobody who wanted to delay had the authority.
Aftermath
NASA spent some time looking for the polar lander with the next Mars probe they sent out… but it was never officially found. Without communications, finding the pieces was like trying to find a needle in a haystack! The microprobes for surface-testing were supposed to land about 50 seconds before the actual lander did, but they’d be an estimated 62 miles away when they hit. That’s the kind of distances they were dealing with. The lander itself definitely flew off-course as soon as the engines cut.
Remember that Malaysia Airlines flight that was never found? They still don’t know for sure where it actually hit the water, even though it was going much slower. The range the plane could have flown in the hours it was missing is impossibly huge – basically the entire Indian Ocean would need to be searched. Granted, people searching for parts to recover also had to deal with the ocean moving and sinking them, but the Mars Polar Lander is in a very similar situation. The lander could be basically anywhere in the top latitudes of the planet. It would take years to find it without the precise data lost in the crash.
Initiatives
The lander failure points towards more rigorous testing procedures. There’s a saying in tech: ‘if you haven’t tested the backup, then you don’t have a backup’. All the redundancies in the world can’t save you if an essential piece of the operation is missing. All those antenna, all that work, lost because there was nothing else to detect distance from the planet itself. No backup. Only legs.
NASA’s Faster-Better-Cheaper initiative, meant to cut down on administrative and material waste, was brought up to the folks in the post-crash conference several times. Two projects were sent out cheaper than previous projects, but not cheaply, and both had failed for seemingly stupid reasons. Why?
Contractors. And a failure to test.
A big part of the issue was miscommunication. Information was passed up the chain of command, but the message would be different by the time it finally made it all the way up – huge issues were reduced to minor problems, and therefore nothing would happen. ‘Little’ issues, like that orbiter’s misreading of its data, never made it upwards: the orbiter that went with this project died because the manufacturer didn’t translate the force measurement to metric, and it was noticed, but the engineers were so low down on the chain that it never got passed upwards.
The contractors involved in production of probes and the like were also part of the problem. The two microprobes allegedly weren’t tested too thoroughly for launch, but if they had been, NASA might have gotten something out of the lander’s failure. The lander itself was tested, but not thoroughly enough. Surely, the other hundred engineers on the project would have noticed something was wrong. But they didn’t, not officially. Concerns landed on deaf ears. Forms were dismissed for being incorrectly filled out. The issue was in the administration of the project, not the physical lander.
Some say that Lockheed had bid too low for what it would actually cost to make the lander, and that they’d cut corners as a result. NASA denies this, and based off of everything I’ve found, they’re right: there’s no reason to doubt it was anything but the sensors and a software bug. The legs themselves were fine, but the programming surrounding the landing equipment wasn’t tested as rigorously as it should have been. If it didn’t continuously send the signal when it was deployed, the lander might have made it; if NASA had delayed launch to fix the issue, the lander might have made it; or if NASA had spent more time on the lander’s ground-response, it might have made it.
There’s a lot of ‘ifs’, and that’s an issue when projects cost millions to make and launch.
Source:
http://www.spaceref.com/news/viewnews.html?id=105
https://mars.nasa.gov/mars-exploration/missions/polar-lander/
https://solarsystem.nasa.gov/missions/mars-polar-lander-deep-space-2/in-depth/
https://www.space.com/1153-mars-polar-lander-clues-crash-site.html