NASA’s Orion Spacecraft Is Officially Headed Back Toward Earth
It has already been over two weeks since the Space Launch System lifted off with Orion on top. In the time since then, Orion has traveled over a quarter million miles away from Earth and set records previously held by the Apollo missions. Now in early December, the spacecraft is officially on its way back toward Earth after completing multiple burns.
Specifically, yesterday Orion left its distant lunar orbit and is now on its return journey home. The spacecraft successfully completed the distant retrograde departure burn at 3:53 p.m. CST, firing its main engine for 1 minute 45 seconds to set the spacecraft on course for a close lunar flyby before its return home. This is one of two necessary maneuvers for the entire return journey.
While so far this mission has been a major success, arguably one of the most challenging aspects is right around the corner. In this case, Orion will attempt to enter the atmosphere in just over a week faster and hotter than ever before. Here I will go more in-depth into the spacecraft’s recent return maneuver, what to expect in the next few days, the upcoming splashdown, and more.
Heading Toward Earth
As of yesterday afternoon, Orion is officially on its way back toward Earth. Specifically, yesterday NASA tweeted saying, “We’ve left lunar orbit! @NASA_Orion fired its main engine today to exit distant retrograde orbit and set itself on a course for Earth. The burn is one of two maneuvers we’ll make ahead of splashdown on Dec 11. Next up? Return powered fly by on Dec 5.”
Some of the final preparation for this maneuver began on November 30th. On Flight Day 15, Orion also performed a planned orbit maintenance burn to maintain the spacecraft’s trajectory and decrease its velocity. During the burn, Orion used six of its auxiliary thrusters on the European Service module to fire for 95 seconds. The burn was initially planned for a shorter duration but was lengthened as part of the team’s effort to add test objectives to the mission. The 95-second burn provided additional data to characterize the thrusters and the radiative heating on the spacecraft’s solar array wings to help inform Orion’s operational constraints. All previous thruster burns were 17 seconds or less.
This led up to yesterday’s official departure. The burn changed Orion’s velocity by about 454 feet per second and was performed using the Orion main engine on the European Service Module. The engine is an orbital maneuvering system engine modified for use on Orion and built by Aerojet Rocketdyne. The engine has the ability to provide 6,000 pounds of thrust. The proven engine flying on Artemis I flew on 19 space shuttle flights, beginning with STS-41G in October 1984 and ending with STS-112 in October 2002. As partially highlighted in the tweet, the burn is one of two maneuvers required ahead of Orion’s splashdown in the Pacific Ocean on Dec. 11. The second will occur on Monday, Dec. 5, when the spacecraft will fly 79.2 miles above the lunar surface and perform the return powered flyby burn, which will commit Orion on its course toward Earth.
Teams also continued thermal tests of the star trackers during their eighth and final planned test. Star trackers are a navigation tool that measures the positions of stars to help the spacecraft determine its orientation. In the first three flight days of the mission, engineers evaluated initial data to understand star tracker readings correlated to thruster firings. To put it in perspective, just after 4:30 p.m. CST on Dec. 1, Orion was traveling 237,600 miles from Earth and 52,900 miles from the Moon, cruising at 2,300 mph.
In other Artemis 1 news, just two days ago on the 30th NASA tweeted again pointing out, “As I mentioned, we’re adding new objectives to #Artemis I because @NASA_Orion is performing so well. We’re orienting the spacecraft up by 20 degrees to understand Orion’s thermal performance when we’re not in a perfect tail-to-sun attitude and collect more data for Artemis II.” All of which is a great sign as the spacecraft continues to display promising results and begins its journey back home.
Upcoming Splashdown
Now that we know more about Orion’s most recent maneuver to exit its distant retrograde orbit, we can take a closer look at its remaining 9 day journey, some other important updates on the spacecraft, and more. With the first maneuver complete, in 3 days Orion will do another close flyby of the Moon’s surface. Here, the spacecraft will use another precisely timed engine firing of the European-provided service module in conjunction with the Moon’s gravity to accelerate back toward Earth.
This maneuver will set the spacecraft on its trajectory back toward Earth to enter our planet’s atmosphere traveling at 25,000 mph (11 kilometers per second), producing temperatures of approximately 5,000 degrees Fahrenheit (2,760 degrees Celsius) – faster and hotter than Orion experienced during its 2014 flight test. Specifically, Exploration Flight Test-1 or EFT-1 (previously known as Orion Flight Test 1 or OFT-1) was the first test flight of the crew module portion of the Orion Multi-Purpose Crew Vehicle. The mission was a four-hour, two-orbit test of the Orion crew module featuring a high apogee on the second orbit and concluding with a high-energy reentry at around 8.9 kilometers per second (20,000 mph). The flight was intended to test various Orion systems, including separation events, avionics, heat shielding, parachutes, and recovery operations prior to its flight aboard the Space Launch System on the Artemis 1 mission.
After an almost month long journey and a total distance traveled exceeding 1.3 million miles, the mission will end with a test of Orion’s capability to make a precision landing within eyesight of the recovery ship off the coast of Baja, California. Following splashdown, Orion will remain powered for a period of time as divers from the U.S. Navy and operations teams from NASA’s Exploration Ground Systems approach in small boats from the waiting recovery ship. The divers will briefly inspect the spacecraft for hazards and hook up tending and tow lines, and then engineers will tow the capsule into the well-deck of the recovery ship to bring the spacecraft home. If fully successful, this mission will mark a major milestone for the agency and help provide the confidence necessary for Artemis II with the first humans.
Orion’s European-built service module has provided the propulsive capabilities to adjust the spacecraft’s course in space via its 33 engines of various types, and serves as Orion’s powerhouse, supplying it with electricity, thermal control, and air and water for future crews, in addition to propulsion. Artemis I is the first time NASA is using a European-built system as a critical element to power an American spacecraft. Provided by ESA (European Space Agency) and its partner Airbus Defence and Space, the service module extends NASA’s international cooperation from the International Space Station into deep space exploration. These relationships also play an important role in future moon infrastructure necessary for upcoming Artemis missions. The agency’s Gateway, a multi-purpose outpost in development to orbit the Moon that will provide essential support for long-term lunar exploration, includes contributions from ESA as well as the Canadian Space Agency and the Japan Aerospace Exploration Agency. Agencywide, NASA has more than 600 active international agreements with organizations and space agencies around the world.
Focusing back on flight day 15, teams elected to add four additional test objectives to Orion’s return trip to Earth to gather additional data on the spacecraft’s capabilities. Two will evaluate whether opening and closing a valve in the pressure control assembly affects a slow leak rate in that system; a third will demonstrate Orion’s ability to perform attitude maneuvers at the rate that will be necessary for a test on Artemis II; and the fourth will test its capability to fly in a three degree of freedom attitude control mode, as opposed to the six degree of freedom mode it typically flies in. Prior to the orbital maintenance burn on the 30th, a total of 5,681 pounds of propellant had been used, 203 pounds less than values expected before launch. Some 2,004 pounds of margin is available beyond what is planned for use during the mission, a 94-pound increase above prelaunch expected values.
With this first exploration mission, NASA is leading the next steps of human exploration into deep space where astronauts will build and begin testing the systems near the Moon needed for lunar surface missions and exploration to other destinations farther from Earth, including Mars. The SLS rocket will evolve from an initial configuration capable of sending more than 26 metric tons to the Moon, to a final configuration that can send at least 45 metric tons. In the coming days, even more information will be released as NASA gets closer to some of the final maneuvers and events.
Conclusion
NASA is only days away from the final burn of Orion to put it on a trajectory for Earth. Just yesterday the agency completed the first burn helping the spacecraft exit its distant retorgrade orbit. In 9 days we can expect to watch Orion splashdown and make history with a successful Artemis I mission. We will have to wait and see how it progresses and the impact it has on the space industry.