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The robotic spaceship was spinning wildly. The first mission of Trevor Bennett’s bold space start-up seemed doomed to failure. But then Bennett, co-founder of Starfish Space, and his team began the calculations.

Over several weeks, they designed algorithms on whiteboards, carried out computer simulations and hardware tests, and developed a solution: by reprogramming the satellite software, they were able to could create a magnetic current that would push against the Earth’s magnetosphere and eventually slow its rotation.

And so, Early one morning last July, they pressed send and sent the software fix from Starfish headquarters in Seattle to a ground station in Norway and then to the spacecraft hovering 340 miles above Earth — in the hope that it would work.

In an earlier generation, the stars of the space age were the astronauts – John Glenn, Neil Armstrong, Alan Shepard – men with military training and the “right stuff” attitude. Today, it’s the software engineers and computer scientists who are driving the space economy from their laptops.

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A revolution in satellite technology has produced spacecraft that are smaller and more powerful, capsules that fly themselves, and autonomous rockets that can reach space, turn around, and make pinpoint landings to fly again. Ground engineers and computer experts have always played an important role in spaceflight, but their role is even more pronounced today, with software changes being sent to spacecraft as routinely as iPhone updates.

“Software engineers are essential,” said Abhi Tripathi, the mission manager at the Space Sciences Laboratory at the University of California, Berkeley, who has also held several senior positions at SpaceX. “Today’s spacecraft should be really good software wrapped around a spacecraft.”

When Tripathi worked at SpaceX, now the recognized leader in the commercial space industry, the company valued software engineers so highly that it continually hired them, even without official job postings. “The rule was that there was always a software position open,” Tripathi said. “Today, even when I hire junior engineers, mission control operators or thermal engineers, I always ask: Can this person program?”

Earlier this year, clever software engineering saved a lunar landing mission. Engineers at a company called Intuitive Machines discovered that the sensors on their lunar module were never turned on. This meant that their spacecraft, Odysseus, was essentially flying blind, unable to search the moon’s rocky and hilly landscape for a safe landing site.

During a press conference earlier this year, CEO Steve Altemus recalled breaking the news to his chief technical officer and mission director, Tim Crain.

“I said, ‘Tim, we have to land without a laser rangefinder,'” Altemus said. “And he turned white because it was like a punch in the gut that we were going to lose the mission.”

The team thought they could replace the broken sensor system with a NASA-developed instrument that would be mounted on the outside of the spacecraft as an experiment for future landings. But because the main sensors weren’t working, that instrument had to be put into service. Replacing such important technology while it was still in service wasn’t easy.

“We started thinking about what it would take to basically short-circuit the system,” said James Blakeslee, a software architect at the company, in an interview. To buy time, the team decided to fly the spacecraft around the moon again while programmers tested their software update on a simulator. “We worked in the back room and the developer responsible for it wrote it on a Post-it note and brought it into the living room,” Blakeslee said.

Normally, such a solution would have taken “a month,” Crain said at the time. The calculations would have been checked through thousands of simulations, which would normally have found errors, forcing the programmers to try again. Instead, he said, “our team basically did it in an hour and a half. It was one of the best engineering feats I’ve ever had the pleasure of being a part of.”

The spacecraft landed on its side after catching on one of its legs. This partial success allowed the company to claim the first commercial lunar landing – and the first by the United States since the last Apollo mission in 1972.

A similar drama unfolded in 2019. when Boeing’s Starliner spacecraft ran into trouble. The spacecraft’s onboard computer system was disrupted for 11 hours, meaning it was executing commands for a completely different part of the mission and wasting valuable fuel in the process. Software programmers were able to send commands to the spacecraft, fixing the problem.

They were also able to fix other potential problems – and found one. When separating from the crew capsule before re-entering the Earth’s atmosphere, the service module could cause a collision and possibly damage the capsule. The software engineers were able to fix that too.

Although the spacecraft completed an uncrewed test flight and did not dock with the International Space Station, it landed safely back on Earth. Boeing launched an investigation to examine all 1 million lines of code in the spacecraft to ensure there were no further errors.

There is probably no space company that attaches more importance to software development than Elon Musk’s SpaceX. Its huge rocket engines fly back to Earth and land on autonomous ships at sea or on landing platforms on land. Its Dragon spacecraft flies autonomously to the space station, relegating the astronauts on board to little more than passengers.

But SpaceX has also encountered some exciting challenges that required a bit of improvisational creativity. In 2013, a Dragon spacecraft got some valves stuck as it approached the space station. So a programmer sent a command to build pressure in front of the valves and then suddenly release it to provide the necessary push to open the valves. At the time, Musk called it “the spacecraft equivalent of the Heimlich maneuver.”

As is often the case, this solution was not the result of completely new code, Tripathi said, but rather an adaptation of the existing code to produce new results. It also came after engineers had extensively tested the software before deploying it to the spacecraft.

Some startups do not have the resources to fully test their systems before launch and plan to make adjustments during flight.

“Many companies have a set launch date that they have to meet, and then if they don’t make any revenue, their investors aren’t happy,” Tripathi said. “So many of these companies launch something before they’ve done the necessary software testing. They say, ‘We have a software test bed. We have good programmers. We’ll figure it out in no time.'”

That’s exactly where Bennett and his Starfish team found themselves last summer when their spacecraft tumbled. The spacecraft, named Otter Pup, was supposed to detach from what’s called an Orbital Transfer Vehicle (OTV), a separate spacecraft that acts like a tugboat and takes it to a specific location in space.

If all went well, the tug would release Otter Pup, which would then fly back to the tug on its own and reattach itself – proof that Otter Pup could dock with satellites in space and move them into different orbits, or even repair and maintain them to extend their lifespan.

Instead, the OTV began to rotate, causing Otter Pup to spin as well.

“It literally rotated once every second,” Bennett recalled in an interview. “And someone said, ‘Oh, one revolution per second, that’s got to be a typo. You mean one degree per second.’ They said, no – that was so far from the norm that people thought it was a typo.”

It was spinning, but the spaceship was active.

To keep the spacecraft as light and simple as possible, it didn’t have many engines. However, it did have what were called “torque rods” that could slow it down by sending out a magnetic pulse. The trick was to send out the pulse at just the right moment while the spacecraft was spinning, so that it pushed against the Earth’s magnetic field.

Bennett, who has a PhD in aerospace engineering and previously worked on Blue Origin’s orbital rocket, worked on some calculations and eventually called the company’s chief engineer over. “Sit with me for half an hour. Just do me a favor,” he said to his colleague. “I’ll do some quick calculations and I need you to tell me where I went wrong.”

But when he scribbled his calculations on a whiteboard, the chief engineer confirmed his calculations.

“My goodness,” Bennett said, “I think we could do this.”

They tested the plan using torque rods they had on the ground, sending up to 10 commands per second due to the high tumbling speed. They were confident it would work. But the spacecraft was rotating so fast that communicating with it was difficult: they could only send 20 lines of code at a time. So they painstakingly edited their formula into bite-sized chunks and ran them through the simulator.

On July 31, about six weeks after launch, they began transmitting the code. Almost immediately, the spacecraft began to slow down. After several hours of executing the commands, it finally became stable.

The OTV was lost. But this year, Starfish discovered another spacecraft that offered a rendezvous opportunity. In April, it came within about half a mile of that satellite.

To demonstrate this victory, it took a photo.

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