Orion continues its journey back to Earth on day 22 of the 25.5-day Artemis I mission with flight controllers and engineers continuing to test the spacecraft and its systems in preparation for future flights with humans aboard.

Engineers conducted the second part of the propellant tank slosh development flight test, called propellant slosh, which is scheduled during quiescent, or less active, parts of the mission. Propellant motion, or slosh, in space is difficult to model on Earth because liquid propellant moves differently in tanks in space than on Earth due to the lack of gravity.

The test calls for flight controllers to fire the reaction control system thrusters when propellant tanks are filled to different levels. The reaction control thrusters used are located on the sides of the service module and can be fired individually as needed to move the spacecraft in different directions or rotate it into any position. Each engine provides about 50 pounds of thrust Engineers measure the effect the propellant sloshing has on spacecraft trajectory and orientation as Orion moves through space.

The test was first performed after the outbound flyby burn, and now again after the return flyby burn, to compare data at points in the mission with different levels of propellant onboard. Approximately 12,060 pounds of propellant has been used, which is 215 pounds less than estimated prelaunch, and leaves a margin of 2,185 pounds over what is planned for use, 275 pounds more than prelaunch expectations. The first prop slosh test objective was completed on day eight of the mission as it prepared to enter the distant retrograde orbit.

A few key milestones for Orion remain, including the entry system check outs and propulsion system leak checks on mission days 24 and 25, respectively.

Orion will travel at around 25,000 mph while reentering Earth's atmosphere, testing the world's largest ablative heat shield by reaching temperatures up to 5,000 degrees Fahrenheit - approximately half the heat of the sun. The heat shield is located at the bottom of the Orion capsule, measuring 16.5 feet in diameter, and sheds intense heat away from the crew module as Orion returns to Earth. The outer surface of the heat shield is made of 186 billets, or blocks, of an ablative material called Avcoat, a reformulated version of the material used on the Apollo capsules. During descent, the Avcoat ablates, or burns off in a controlled fashion, transporting heat away from Orion. Learn more about Orion's heat shield in the Artemis I reference guide.

Artemis I - Flight Day 21: Orion Leaves Lunar Sphere of Influence, Heads for Home
Orion exited the lunar sphere of gravitational influence Tuesday, Dec. 6, at 1:29 a.m. CST for the last time on the Artemis I mission less than a day after completing the return powered flyby burn that put the spacecraft on course for splashdown Sunday, Dec. 11. Earth's force of gravity is now the primary gravitational force acting on the spacecraft.

Orion successfully performed the fourth return trajectory correction burn at 4:43 a.m. using the reaction control system thrusters. The burn lasted 5.7 seconds and changed the velocity of the spacecraft by 0.6 feet per second.

Flight controllers used Orion's cameras to inspect the crew module thermal protection system and European Service Module, the second of three planned external spacecraft inspections. Teams conducted this survey early in the mission to provide detailed images of the spacecraft's external surfaces after it had flown through the portion of Earth's orbit containing the majority of space debris, and teams reported no concerns after reviewing the imagery. This second inspection during the return phase is being used to assess the overall condition of the spacecraft several days before re-entry.

During both inspections, the Integrated Communications Officer, or INCO, commanded cameras on the four solar array wings to take a series of still images. Engineers and flight controllers at NASA's Johnson Space Center in Houston will review the imagery over the coming days. A final photographic survey will be conducted Friday as Orion continues its journey home.

Teams responsible for recovering Orion after its splashdown are continuing preparations ahead of the Dec. 11 splashdown off the coast of California. The mission management team will determine the landing site location Thursday, Dec. 8. Listen to NASA's Artemis I recovery director, Melissa Jones, talk about what it takes to fetch the Orion spacecraft from the Pacific Ocean at the end of the mission on "Houston We Have a Podcast."

Related Links
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NASA's Orion spaceship slingshots around Moon, heads for home
Washington (AFP) Dec 6, 2022
NASA's Orion spaceship made a close pass of the Moon and used a gravity assist to whip itself back towards Earth on Monday, marking the start of the return journey for the Artemis-1 mission. At its nearest point, the uncrewed capsule flew less than 80 miles (130 kilometers) from the surface, testing maneuvers that will be used during later Artemis missions that return humans to the rocky celestial body. Communication with the capsule was interrupted for 30 minutes when it was behind the far side ... read more

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