A selfie of the Orion capsule with the Earth-Moon system in the background, when it was at its furthest distance from our planet, more than 430,000 km. © Nasa
Despite difficult beginnings, the Artemis I mission is on the way to becoming a major success for NASA, which intends to establish itself permanently on the Moon. After almost three weeks of travel, the Orion spacecraft, which will carry the crew of the future Artemis II and III manned missions, is now on its way to Earth.
The opportunity for the European Space Agency (ESA) et his American counterpart to return to the trajectory and the trials that await Orion until its plunge into the Pacific Ocean on Sunday, December 11, 2022.
Harnessing Lunar Gravity
Before heading towards Earth, the capsule had to extricate itself from its distant retrograde orbit (in the opposite direction to the rotation of the Moon), then from the gravitational well of our natural satellite. What she did on December 5 in a maneuver described by ESA as “the firing back […] the longest and strongest the European Service Module has flown, and the last major burn before the end of the Artemis I mission”. In reality, Orion only left the Moon’s sphere of influence on December 6.
At 5:43 p.m. (French time), while Orion was behind the Moon, deprived of communications with the Earth, because our satellite was obstructing the signal, the service module started its engines to accelerate it for 3 min 26 s until to reach a speed of 1054 km/h. The device also changed its trajectory to head towards our planet. Fully automated, the maneuver involved pulling take advantage of the force of gravity lunar to further accelerate the ship while limiting energy consumption.
Orion’s route during the Artemis I mission. © ESA
Equipped with 33 engines in total, the Orion service module was developed by ESA and not NASA. In addition to propelling the vessel, it is in charge of supplying electricity and regulating the temperature on board, tasks which it accomplishes wonderfully according to the European agency. “The four solar wings have produced 15% more energy, while we are consuming less electricity, as the spacecraft’s temperature fluctuates less than expected”welcomed the head of mission of the ESA, Philippe Deloo.
Dive into the ocean at high speed
On his way home, a total of six days, Orion continues to perform various tests. For example, NASA engineers want to take advantage of the calm of this part of the journey to activate the side thrusters of the spacecraft and observe the movement of fuel in the tank in the absence of gravity and its impact on Orion. Three minor trajectory corrections must also be made before the capsule enters the Earth’s atmosphere.
A little less than an hour before the shuttle plunges into the Pacific after 25 days of travel, it will separate from its service module, which will disintegrate in the upper layers. Then it will pierce our atmosphere at 39,590 km/h, 24 times that of a rifle bullet and 30% faster than an astronaut returning from the ISS. The opportunity for NASA to test Orion’s heat shield, made up of 186 blocks of an ablative material called Avcoat. The device will indeed be exposed to a temperature of 2760°C, half that of the Sun on its surface approximately.
The entry into the atmosphere of the ship will be unprecedented. NASA will test a maneuver called skip entry. Instead of entering directly, the shuttle will somehow bounce off the atmosphere, which will slow its speed. Once in free fall, a system of 11 parachutes will activate to slow it down further. Having landed off the Californian coast, a Navy team will come to recover it and NASA will then be able to celebrate the success of its Artemis I mission.