Astrobotic knew its first house mission can be rife with dangers. In any case, the corporate’s Peregrine spacecraft would try one thing by no means finished earlier than—touchdown a business spacecraft on the floor of the Moon.
Essentially the most hazardous a part of the mission, really touchdown on the Moon, would occur greater than a month after Peregrine’s launch. However the robotic spacecraft by no means made it that far. Throughout Peregrine’s startup sequence after separation from its United Launch Alliance Vulcan rocket, one of many spacecraft’s propellant tanks ruptured, spewing treasured nitrogen tetroxide into house. 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, figuring out 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 Solar, permitting its battery to recharge. Over time, Peregrine’s scenario stabilized, though it did not have sufficient propellant remaining to aim 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 unique 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 method again towards Earth, Peregrine was on a flight path that will carry it again into the ambiance, the place it might deplete on reentry. That meant Astrobotic had a call 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 hold Peregrine in line to reenter Earth’s ambiance and keep away from the chance 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 induced 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 gasoline 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. “Inside somewhat over a minute, the stress had risen to the purpose within the oxidizer aspect that it was effectively past the proof restrict of the propulsion tank. We consider 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 had been coming from the very best excessive of an ideal launch and got here right down to the bottom low, once we came upon that the spacecraft not had the helium and not had the propulsion wanted to aim the Moon touchdown,” he mentioned. “What occurred subsequent, I feel, was fairly exceptional and provoking.”
In a press briefing Friday, Thornton outlined the obstacles Astrobotic’s controllers overcame to maintain Peregrine alive. With no wholesome propulsion system, the spacecraft’s photo voltaic panels weren’t pointed on the Solar. With a couple of minutes to spare, one in all Astrobotic’s engineers, John Shaffer, devised an answer to reorient the spacecraft to begin recharging its battery.
As Peregrine’s oxidizer tank misplaced stress, the leak price slowed. At first, it seemed just like the spacecraft may 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 might have returned information 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 ambiance. This arrange Astrobotic for a “very troublesome choice,” Thornton mentioned.
Nudging Peregrine off its collision course with Earth would have required the spacecraft to fireside its most important 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 probability Astrobotic might have guided Peregrine towards a flyby or affect with the Moon.
“The factor we had been weighing was, ‘Ought to we ship this again to Earth, or ought to we take the chance to function it in cislunar house and see if we are able to ship this out farther?'” Thornton mentioned.
