India lost contact with its spacecraft just before touchdown. Why is it so hard to stick a lunar landing?
Half a century is a blip on cosmic timescales, but feels like an age in technological innovation, long enough to transform a task once considered impossible into something quite doable. So it might seem that, 50 years after human beings touched the surface of the moon, landing a spacecraft on our next-door neighbor should be less difficult, perhaps even easy.
The latest attempt to land on the moon may have failed this week, after an Indian spacecraft — an uncrewed, robotic mission — appeared to have potentially crashed. The Chandrayaan-2 mission, developed and launched by India’s space agency, began orbiting the moon in August and released a lander yesterday. Mission Control lost contact with the lander, named Vikram, as it neared the surface. Indian officials have not yet announced the cause of the failure.
The people working on lunar missions today, from engineers at government agencies to billionaire businessmen who own multiple companies, are certainly not starting from zero, as the United States and the former Soviet Union did.
“In some ways it’s much easier,” says Yoav Landsman, a spacecraft engineer. “But in the end, it’s not easy at all.”
Landsman would know. In April, his own lunar mission smashed into pieces on the surface. Like Vikram, the Beresheet lander, built by the Israeli nonprofit group SpaceIL, stopped calling home just before it was supposed to touch down. The only successful attempt this year was made in January, when China landed a spacecraft, with rover included, on the far side of the moon, the face that never turns toward Earth — a world first.
Chandrayaan, Sanskrit for “moon craft,” launched in July, poised to make India only the fourth country to land something on the moon, after the United States, China, and the former Soviet Union. A decade earlier, the Chandrayaan-1 mission delivered an orbiter carrying a probe that was deliberately crashed into the surface as a test run. This time, the orbiter would deploy a lander and rover for a gentle landing. They were bound for the side of the moon that we can see, to a spot near its south pole, a place other spacefaring nations, including the United States, are eyeing for its potentially numerous reservoirs of frozen water — an indispensable resource for a future moon base.
Landing on the moon is certainly easier now than in the 1960s, for many reasons, some rather obvious, such as the strain of technological achievement in software and hardware that created supercomputers small enough to fit into pockets. During the space race, engineers had to figure out how orbital mechanics worked from scratch. And if an agency wanted something for its spacecraft, it probably had to invent the thing first.
Now many accoutrements of a space mission come off the shelf, and buying them is made easier by something else that didn’t exist during the Apollo era: the internet. Landsman says mission teams can shop online for sensors, computers, solar panels, and propulsion systems. Even the rockets are ready-made. “You can go out and buy a launch,” says John Thornton, the CEO of Astrobotic, an American company developing a lunar lander called Peregrine. Astrobotic is paying the United Launch Alliance, a rocket manufacturer, to launch Peregrine in 2021. Beresheet, the Israeli lander, launched on a SpaceX rocket.
Today we know more about what the moon looks like up close, thanks to orbiting spacecraft with high-resolution cameras that provide mission planners detailed photos that they need to carefully select landing sites. A small NASA mission, sent to lunar orbit in 2011, provided data about the gravitational forces around the moon that, Landsman says, every engineer uses now.
But some mysteries persist (such as the provision of funding and political will — another story). The lunar regolith, as fine as powder, is still poorly understood, says Alicia Dwyer Cianciolo, an aerospace engineer at NASA working on the agency’s new plans to send robotic missions to the moon. “I don’t know if we got lucky on the other missions, but we feel like some of the new engine types and the thrust levels that we will have — we really don’t understand how it will stir up the different kinds of regolith in different locations on the moon,” Cianciolo says. Landers could kick up a cloud of dust that blocks sensors from detecting the craters or boulders that a last-minute engine burn might avoid. And the thrust could displace enough lunar matter that the spacecraft lands tilted, a position that could prevent a rover from rolling out safely.
The mysteries of the lunar environment make it difficult to predict, let alone perfect, the complicated maneuvers of a landing sequence. Simulations on Earth provide incomplete pictures of a preprogrammed process that unfolds autonomously thousands of miles away. The spacecraft must go from a speed of thousands of miles an hour to nearly zero in about 15 minutes. It has to ignite its engines and thrust itself against the direction it is hurtling toward. As it slows, it falls, and more engine burns are needed to keep it from plummeting too fast.
“It’s actually like landing a missile,” Landsman says.
The spacecraft is covered in sensors that track its altitude and scan the surroundings for any perilous obstacles below. The inputs can help the spacecraft make a snap decision right above the surface, but the moon’s gravity, faint but influential, will eventually take over. If India’s attempt had worked, the Vikram lander would have coasted to a gentle stop.
As Vikram began its descent yesterday, the atmosphere at the headquarters of the Indian Space Research Organisation, in Bangalore, was tense but buoyant. The agency had set up a live-stream from the control room, and an array of people, including Prime Minister Narendra Modi, could be seen monitoring telemetry displays and mingling. The spacecraft was about two kilometers (1.2 miles) above the surface when something went wrong.
The mood in the room darkened instantly. The faces, now serious and uncertain, prompted tingles of déjà vu in anyone who had watched the Beresheet live-stream five months earlier. All eyes in the room remained on a massive computer display, where a green dot representing the Vikram lander now hovered, motionless. The final data suggested that the lander had deviated from its planned route.
I messaged Landsman, whom I’d interviewed earlier in the day, and asked whether he was watching. It was nearly midnight in Israel. “Looks too familiar, I’m afraid,” he wrote back. Landsman and his colleagues believe that a technical glitch doomed their lander, but they can never know the details; the systems that would answer their questions are likely scattered on the lunar surface.
It was after 2 a.m. in India when, the fate of the Vikram lander still unclear, Modi gave the head of the space agency a pat on the back and delivered a pep talk to the team. “You’ve done a great job and the country is proud of you,” Modi said, according to a translation by Shiv Aroor, a journalist at India Today. Before the failed attempt, India had plans for a Chandrayaan-3, another mission to the moon’s south pole.
The Vikram lander now joins the many other artifacts that humankind has delivered to the lunar surface, whether in one piece or many. The orbiter of the Chandraayan-2 mission will never touch down. It is designed to circle the moon until it malfunctions or deteriorates, perhaps keeping vigil over the bits and pieces of a missed moonshot.
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