“Today is an extraordinary day.” “It’s historic because we’re going to go into deep space with a new generation.” Bill Nelson, NASA administrator, showed his joy after the uncrewed Artemis 1 mission successfully landed in the Pacific this afternoon.
On December 1, still in lunar orbit, engineers turned on the Orion spacecraft’s engines and the Artemis 1 mission officially began its long return home. The impulse, in effect, took it before thousands of km beyond the Moon, where all the systems that will be necessary for future manned missions were checked.
Afterwards, the ship returned to approach our satellite for its final maneuver. At 5:42 p.m. (Spanish time) on December 5, Orion approached just 127 km from the lunar surface, took advantage of its gravity to achieve more speed and, at the precise moment, a new engine ignition placed it in the way back to Earth.
Now, a week later, the complex landing trajectory has been completed exactly as planned. In a move never attempted before, the Orion did not shoot straight in, as the Apollo lunar missions did, but ‘bounced’ off Earth’s atmosphere just like a flat stone would on water.
Initially, in effect, the spacecraft touched the atmosphere at an altitude of about 61 km and then turned on itself 180 degrees (so that future astronauts would be face down), which changed its center of gravity and caused it to jump back towards up, up to 99 km above sea level. After this maneuver, the ship resumed its descent, with its guidance system pointing directly at the point chosen for splashdown.
With this maneuver, called ‘jump entry’, two things were achieved: that the gravitational forces inside the ship did not exceed 4G (the astronauts on the Apollo missions had to endure up to 6.8G) and, not least , that ground control could choose with precision both the moment and the splashdown point, something that had not been possible until now.
Suffice it to recall, as an example, that the crew of Apollo 8, the first to orbit the Moon, splashed down in December 1978 in the middle of the night (mission control would have preferred daylight) in some shark infested waters, reason for which neither the rescue divers nor the astronauts themselves dared to move until dawn almost two hours later. Something that will not happen again thanks to the new ‘jump input’ tested this Sunday.
The idea of this maneuver already existed in the time of Apollo, but the power of the computers of the time did not allow it to be calculated safely. After the success of this Sunday, the next time it will be attempted will be in 2024, when Artemis 2 take a crew of astronauts around the Moon, bring them back to Earth, and make a smooth, controlled splashdown close to home.
A new heat shield
At the moment of entering the atmosphere, the Orion spacecraft plunged into the sea at a speed of 32,000 km per hour. Which served to test, also for the first time, its innovative thermal shield, which had to withstand up to 2,760 degrees Celsius during the descent. Of a completely new design and lacking proper ground facilities, the only way to test the new shield was in actual flight. Considered as one of the main objectives of the missionyour good behavior also contributes to clear the future of the upcoming Artemis 2 and 3 missions.
During the descent, the friction of the air slowed down the ship, so that just a few minutes after the very rapid entry, its speed had been reduced to the close to 500 km/h necessary for the deployment of the two large braking parachutes, which They opened at an altitude of 7,600 meters and, in just one minute, reduced the fall speed to 160 km/h. Shortly after, already at 2,000 meters, the three main parachutes opened, each 35 meters in diameter, which took Orion to the splashdown point at just under 30 km/h. Unlike the shield, the parachutes had previously been subjected to 47 different tests.
Finally at 18:40, Spanish peninsular time, the Orion gently splashed down off the coast of Baja California, in the Pacific. Once in the water, the USS Portland USS Portland will retrieve the capsule from her. During that time, the descent and temperature data will be checked during the novel entry into the atmosphere maneuver.
The Orion will then be taken to the San Diego naval base and from there sent to the Kennedy Space Center in Florida, where all of its systems will be examined over the next few weeks.