Astrobotic knew its first area mission could be rife with dangers. After all, the firm’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, really 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, certainly one of the spacecraft’s propellant tanks ruptured, spewing treasured 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 consequence we had been hoping for,” mentioned John Thornton, CEO of Astrobotic.
Astrobotic’s management staff, understanding of the firm’s headquarters in Pittsburgh, swung into motion to save the spacecraft. The propellant leak abated, and engineers wrestled management of the spacecraft to level its photo voltaic arrays toward the Sun, permitting its battery to recharge. Over time, Peregrine’s state of affairs 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 similar distance as 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 means again toward Earth, Peregrine was on a flight path that will deliver it again into the ambiance, the place it could dissipate 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 deliver 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 danger of sending a crippled spacecraft out to the Moon?
Making lemonade out of lemons
This was the first time Astrobotic had flown an area mission, and its management staff had a lot to be taught. The malfunction that brought about the propellant leak seems to have been with a valve that did not 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 bit of over a minute, the strain had risen to the level in the oxidizer facet that it was nicely 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 major 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 hold Peregrine alive. Without a wholesome propulsion system, the spacecraft’s photo voltaic panels had been not pointed at the Sun. With a couple of minutes to spare, certainly one of Astrobotic’s engineers, John Shaffer, devised an answer to reorient the spacecraft to begin recharging its battery.
As Peregrine’s oxidizer tank misplaced strain, the leak price slowed. At first, it seemed 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 might have returned knowledge from the lunar floor if it landed.
The small propulsive impulse from the leaking oxidizer drove Peregrine barely off beam, placing it on a course to deliver it again into Earth’s ambiance. This arrange Astrobotic for a “very troublesome determination,” Thornton mentioned.
Nudging Peregrine off its collision course with Earth would have required the spacecraft to hearth its foremost engines, and even when that labored, the lander would have wanted to carry out extra maneuvers to get shut to the Moon. A touchdown was nonetheless out of the query, however Thornton mentioned there was a small probability Astrobotic might have guided Peregrine toward a flyby or affect with the Moon.
“The factor we had been weighing was, ‘Should we send this again to Earth, or ought to we take the danger to function it in cislunar area and see if we are able to send this out farther?'” Thornton mentioned.