The adventure of the Odysseus lander ended on the Moon, a story full of twists and turns

After a chaotic moon landing on February 22, the Nova-C vehicle from Intuitive Machines still managed to transmit its data for a week. A technical feat even if it was lying on the surface, achieved with limited means. The teams in Houston have nothing to be ashamed of, they have learned… For next time.

Go back a few weeks. On February 15, with a few days of delay, Falcon 9 took off from the Kennedy Space Center. Apparently, a routine flight for SpaceX which sends its rockets into space twice a week now… And yet, it is indeed a unique lunar mission which is coming. The first shot dedicated to Intuitive Machines and their small public-private lander (largely financed by NASA) Nova-C, named Odysseus for the occasion.

4.3 meters high, 675 kg on the scale and a unique main engine, powered by methane and liquid oxygen, the objective of Nova-C is ambitious: in one week, go straight to the Moon, check all its systems, brake to enter orbit then land on the surface not far from the South Pole, next to a crater named Malapert A. A challenge for the team of 250 people based in Houston.

We must save Odysseus constantly

And despite reassuring messages on social networks, the challenges began as soon as Odysseus was ejected, brought precisely to the desired point by his Falcon 9 rocket. During the start-up and self-diagnosis of his systems , the lunar lander’s star pointer no longer responds. Therefore, it is impossible to precisely orient Nova-C, which slowly rotates on itself and communicates through brief episodes towards Earth. Its batteries are slowly draining… Until the teams manage to send a software patch that resets the pointers.

There were then less than three hours left before having to call a press conference and announce the end of the mission. According to Steve Altemus, the founder and CEO of Intuitive Machines, his engineers and technicians encountered 11 such events in 12 days. Some software fixes worked better than others.

More altitude? Nevermind !

On February 16, the company encountered a problem related to the cooling of the propellants of its main engine, but managed, with a slight delay, to activate it correctly for its first maneuvers en route to the Moon. On February 21, despite new uncertainty in the trajectory, Odysseus managed to slow down and change its trajectory by more than 800 m/s (2880 km/h) to successfully enter lunar orbit!

This is already a great success on the part of the Texan teams, especially when we compare this result with that of the public-private lander Peregrine (Astrobotic) which took off just over a month before that of Intuitive Machines . But on February 22, while everyone was already at their posts to control the descent to the surface and anxiously receive the data, the Nova-C vehicle lost the use of its laser altimeter. Worse, an assembly error prevents resetting the entire block which gives the altitude of the lander.

More instruments? Still no big deal!

Like the surface flown over by Odysseus, the teams will then undergo an incredible series of roller coasters. In an emergency, the landing is pushed back one orbit, while on the engineering side, we try everything for the trick: on the flanks of Nova-C there is a NASA experiment, an instrument that we call a Lidar, with a laser that scans the surface… And which was to study the data during the descent. Neither one nor two, here it is propelled to the rank of main sensor.

There is no more time to procrastinate, the software patch is transferred to Odysseus, who receives the order to brake and land. But the on-board computer has a problem, it cannot process the Lidar data in real time. The gap becomes too significant, to the point of no return: the Lidar data becomes unusable from an altitude of 15 kilometers. The Nova-C lander is then deprived of raw altimeter data. He is flying blind, or rather, it is the opposite: all he has left is his eyes.

At some point you have to hit the ground

Indeed, Nova-C is equipped, like all “modern” vehicles (i.e. those that have attempted to land on the Moon since 2010), with a capacity to study data through images. , to guide yourself to the planned landing site and avoid obstacles that could appear on the slopes at the last minute. It’s this stereo optical system that will save the day for Nova-C. As the lander brakes and descends, its inertial computing unit gave it a braking estimate and the cameras provided it with the images. A solution which allowed him to approach 1.5 km from the planned site (an inefficient precision) with a differential between the calculated altitude and the true surface of only 100m. Well, despite everything it’s still 100 meters, so Odysseus suffered a very rough impact with the lunar soil…

In reality, he hit a 12° inclined slope vertically, which immediately broke one of his 6 feet. And he stayed standing! At least, for a few seconds. He then lay down on the slope, leaning on one of his helium tanks and one of his small experiment platforms. But for the first time since 1972, an American device landed on the Moon and transmitted data.

An active week on the Moon

When it landed on the evening of February 22, Intuitive Machines was unable to provide many details, not understanding why Nova-C was able to communicate, with degraded signals, while having problems reaching the vehicle. In the following half-day, when the teams analyzed exactly its orientation, they understood better. Its two main antennas sent signals that were reflected by the lunar surface… With this exception, Odysseus was doing well, or almost.

The vehicle’s illumination is not optimal, its main solar panel on the top not being illuminated, there was only one surface on its side to fulfill the role. But provided the battery was properly managed, engineers were able to get around the problem. Nova-C operated until the morning of February 29, and there was a small margin left unused just in case, to try to wake up the lander in 3 weeks, after lunar night.

A success ? Yes Yes !

For its part, NASA is happy. Obviously, everything didn’t go as planned. But all the payloads on Odysseus (except one, designed to observe the cloud raised during the landing maneuver) worked and the American agency was able to recover around 650 MB of data for its future lunar missions, so the objectives are -they filled. And of course the company hopes to fix the flaws for next time. Other experiments were able to take place, such as the (delayed) ejection of a small camera companion once on the ground (it was planned to drop it at 30m altitude, but as the computer went from 100 to 0…), but the image did not work.

Overall, Intuitive Machines believes that with everything that worked and the lunar landing, the IM-1 mission is a significant success. It’s difficult to prove them wrong when we know all those who have failed in their attempt in recent years. After the “head down” success of the Japanese SLIM lander, it is therefore a new lunar adventure which ends well. Looking forward to the next one!

Source : Arstechnica