Astrobotic knew its first area mission can be rife with dangers. After all, the corporate’s Peregrine spacecraft would try one thing by no means finished earlier than—touchdown a industrial spacecraft on the floor of the Moon.
The most hazardous a part of the mission, truly touchdown on the Moon, would occur greater than a month after Peregrine’s launch. But the robotic spacecraft by no means made it that far. During Peregrine’s startup sequence after separation from its United Launch Alliance Vulcan rocket, one of many spacecraft’s propellant tanks ruptured, spewing valuable nitrogen tetroxide into area. The incident left Peregrine unable to land on the Moon, and it threatened to kill the spacecraft inside hours of liftoff.
“What a wild journey we had been simply on, not the end result we had been hoping for,” mentioned John Thornton, CEO of Astrobotic.
Astrobotic’s management staff, understanding of the corporate’s headquarters in Pittsburgh, swung into motion to avoid wasting the spacecraft. The propellant leak abated, and engineers wrestled management of the spacecraft to level its photo voltaic arrays towards the Sun, permitting its battery to recharge. Over time, Peregrine’s scenario stabilized, though it did not have sufficient propellant remaining to try a descent to the lunar floor.
Peregrine continued on a trajectory out to 250,000 miles (400,000 kilometers) from Earth, about the identical distance because the Moon’s orbit. Astrobotic’s authentic flight plan would have taken Peregrine on one lengthy elliptical loop round Earth, then the spacecraft would have reached the Moon throughout its second orbit.
On its manner again towards Earth, Peregrine was on a flight path that will carry it again into the environment, the place it might expend on reentry. That meant Astrobotic had a choice to make. With Peregrine stabilized, ought to they try an engine burn to divert the spacecraft away from Earth onto a trajectory that would carry it to the neighborhood of the Moon? Or ought to Astrobotic maintain Peregrine in line to reenter Earth’s environment and keep away from the danger of sending a crippled spacecraft out to the Moon?
Making lemonade out of lemons
This was the primary time Astrobotic had flown an area mission, and its management staff had a lot to study. The malfunction that brought on the propellant leak seems to have been with a valve that didn’t correctly reseat throughout the propulsion system’s initialization sequence. This valve activated to pressurize the gas and oxidizer tanks with helium.
When the valve did not reseat, it despatched a “rush of helium” into the oxidizer system, Thornton mentioned. “I describe it as a rush as a result of it was very, very quick. “Within a little bit over a minute, the strain had risen to the purpose within the oxidizer aspect that it was properly past the proof restrict of the propulsion tank. We imagine at that time the tank ruptured and led to, sadly, a catastrophic lack of propellant … for the first mission.”
Thornton described the glum temper of Astrobotic’s staff after the propellant leak.
“We were coming from the highest high of a perfect launch and came down to the lowest low, when we found out that the spacecraft no longer had the helium and no longer had the propulsion needed to attempt the Moon landing,” he said. “What happened next, I think, was pretty remarkable and inspiring.”
In a press briefing Friday, Thornton outlined the obstacles Astrobotic’s controllers overcame to maintain Peregrine alive. Without a wholesome propulsion system, the spacecraft’s photo voltaic panels weren’t pointed on the Sun. With a couple of minutes to spare, considered one of Astrobotic’s engineers, John Shaffer, devised an answer to reorient the spacecraft to start out recharging its battery.
As Peregrine’s oxidizer tank misplaced strain, the leak charge slowed. At first, it regarded just like the spacecraft might need solely hours of propellant remaining. Then, Astrobotic reported on January 15 that the leak had “virtually stopped.” Mission controllers powered up the science payloads aboard the Peregrine lander, proving the devices labored and demonstrating the spacecraft may have returned knowledge from the lunar floor if it landed.
The small propulsive impulse from the leaking oxidizer drove Peregrine barely off target, placing it on a course to carry it again into Earth’s environment. This arrange Astrobotic for a “very tough determination,” Thornton mentioned.
Nudging Peregrine off its collision course with Earth would have required the spacecraft to fireplace its foremost engines, and even when that labored, the lander would have wanted to carry out extra maneuvers to get near the Moon. A touchdown was nonetheless out of the query, however Thornton mentioned there was a small likelihood Astrobotic may have guided Peregrine towards a flyby or affect with the Moon.
“The factor we had been weighing was, ‘Should we ship this again to Earth, or ought to we take the danger to function it in cislunar area and see if we are able to ship this out farther?'” Thornton mentioned.