It was a flawless launch. In the early hours of Monday morning, the Vulcan Centaur rocket rumbled over Cape Canaveral in the dark, shedding its solid rocket boosters and releasing the Peregrine spacecraft on the perfect trajectory for its landmark mission to the moon.
The success led to a “Yee-haw!” from Tory Bruno, CEO of United Launch Alliance, which built the rocket: it was the Vulcan’s maiden flight, after all. But it wasn’t long before the mood changed. Astrobotic, the firm behind Peregrine, found that the spacecraft was propellant leaking. And without enough fuel, the chances of landing softly on the moon are slim quickly dropped to zero.
It has been more than half a century since Nasa landed astronauts on the moon and brought them all home safely. Shouldn’t landing on the lunar surface today be, if not quite trivial, then at least simple? Hasn’t the rocket science of the mid-20th century become the basic knowledge of the 21st?
Peregrine is not the only recent failure. While China and In the placed both robotic landers on the moon, Russia’s Luna 25 crashed landed last year, nearly 60 years after the Soviet Union’s Luna 9 nailed the first soft landing. Landers built by private companies have a 100% failure record on the moon: the Israeli Beresheet lander crashed in 2019while a Japanese lander built by ispace crashed last year. Peregrine makes it three out of three losses.
One fundamental challenge, says Jan Wörner, former director general of the European Space Agency (Esa), is weight. “You’re always close to failure because you have to be light or the spacecraft won’t fly. You can’t have a huge margin of safety.”
In addition, almost every spacecraft is a prototype. Apart from rare cases, such as the Galileo communications satellites, spacecraft are custom machines. They are not mass produced with the same proven systems and designs. And once they’re deployed in space, they’re on their own. “If you have trouble with your car, you can have it repaired, but in space there is no opportunity,” says Wörner. “Space is another dimension.”
The moon itself presents its own problems. There is gravity – one sixth as strong as on Earth – but no atmosphere. Unlike Mars, where spacecraft can fly to their destination and brake with parachutes, lunar landings depend entirely on engines. If you have a single engine, as smaller probes tend to do, it must be steerable because there is no other way to control the descent.
To complicate matters, the engine must have a throttle, so that the thrust can be switched up and down. “Usually you light them on fire and they provide a steady state boost,” says Nico Dettmann, Esa’s lunar exploration group leader. “Changing the drive during operations adds a lot more complexity.”
And yet, with the first moon landings back in the 60s, it can be hard to fathom why the moon remains such a difficult destination.
Moon mission records provide a clue: soon after the Apollo program, lunar landers fell out of favor. When China’s Chang’e 3 spacecraft landed in 2013, it made the first soft landing on the moon since the Soviets’ Luna 24 in 1976.
“There were decades when people didn’t develop landers,” says Dettmann. “The technology is not so common that you can easily learn from others.”
So testing is critical. But while rockets can be bolted on and put through their paces, the options are more limited for spacecraft. Tests can check that power and propulsion, navigation, communications and instruments are working, and spacecraft are shaken to ensure they can withstand the intense vibrations of launch, but there is no good way to simulate a moon landing. “It is much more difficult to qualify and validate a lunar lander than many other space systems,” says Dettmann.
During the space race, Nasa had a staggering 4% of US GDP to spend. It continued to track failure after failure before reaching the moon. It now has 70 years of institutional knowledge and a culture dedicated to designing, building and testing spacecraft. However, under its new Commercial Lunar Payload Services (CLPS) scheme, the agency wants to cut costs and stimulate the US space industry by paying private companies, such as Astrobotic and Houston-based Intuitive Machines, to deliver its instruments to the moon.
The trade-off is a greater risk of failure, so more lost missions are to be expected. “These companies are all relatively new. And in comparison, they’re doing these missions on pocket money,” says Joshua Rasera, a research fellow at Imperial College London. But the strategy should pay off, he adds, because companies learn from their failures. “It’s still cheaper than the total number of missions,” he says, “even if the first few might fall in.”
