Why the Peregrine moon lander was burned up in Earth’s atmosphere

The Peregrine lander’s mission is over. The US company that built the thwarted lunar lander, Astrobotic, has brought the spacecraft home to burn up in Earth’s atmosphere after a fuel leak kept it from completing its journey to the moon.

What went wrong with the Peregrine lander?

Just 7 hours after its 8 January launch atop a Vulcan rocket, engineers noticed that Peregrine wasn’t pointing in the right direction, so its solar panels weren’t charging the batteries that ran its electronics. Shortly after that, it became clear that fuel was leaking from the craft. Eventually, it was found that an oxidiser tank had ruptured, perhaps because of a stuck valve, and the leak was generating a small amount of thrust that changed the probe’s orientation. By the time it was all figured out, Peregrine had already lost too much fuel to make it to the moon, let alone perform the manoeuvres necessary for a gentle landing on the lunar surface.

Peregrine was in space for days – what was it doing all that time?

Astrobotic’s engineers were able to correct Peregrine’s orientation, so once its solar panels were pointed in the right direction, its batteries charged up. This allowed Peregrine’s operators to briefly test-fire the main engine and turn on its on-board rover, which can help them better understand the operations of the craft in space and help determine what went wrong. They also remotely switched on some of its scientific instruments and made measurements of radiation in interplanetary space that could provide useful scientific insights. Operating the craft for a few days also gave Astrobotic time to decide whether to try to divert from the planned moon landing and extend the mission in open space or to let it continue on its path back towards Earth.

Why did they have to bring it back to Earth instead of just leaving it in space?

Peregrine could have potentially survived for a bit longer in orbit around Earth, but leaving it there carried some risks. Eventually, the spacecraft would have run out of fuel entirely, which would have left it as essentially a cannonball hurtling uncontrollably around the planet. This kind of space junk can badly damage active satellites. A statement from Astrobotic read: “Ultimately, we must balance our own desire to extend Peregrine’s life, operate payloads, and learn more about the spacecraft, with the risk that our damaged spacecraft could cause a problem”.

Isn’t bringing it back to Earth dangerous too?

It is actually much safer to steer the spacecraft back to Earth – satellites are de-orbited like this regularly, and they generally burn up from the incredible heat they experience as they plummet through the atmosphere. Peregrine was also carefully aimed towards the Pacific Ocean, just east of Australia, to minimise any risk of surviving fragments hitting populated areas.

What about the other things that Peregrine was carrying?

Aside from its scientific instruments, the spacecraft also carried two controversial payloads sent to space by a company called Celestis, which provides what it called “memorial spaceflights”. These two canisters held cremated human remains, including those of Star Trek creator Gene Roddenberry and actors James Doohan and Nichelle Nichols. Whether or not the capsules survived the trip through Earth’s atmosphere to fall into the ocean is unclear.

Why do missions to the moon keeping going badly?

It is true that this is the third mission over the last year to fail to make it to the moon, but that is only partially because of the difficulty of sending probes into space and making them land softly hundreds of thousands of kilometres away. Attempts to land on the moon are also drastically increasing in number, and many are using new and untested equipment and protocols. It is natural for there to be some growing pains, but there are more planned lunar landings coming up, and Astrobotic executives are already talking about their plans to try again.