Continuing a “drama-free” test flight, NASA’s Orion spacecraft is set to fire its main engine Thursday to leave a distant orbit around the moon, heading for a flyby close to the lunar surface next week to swing onto a trajectory to bring it back to Earth for splashdown in the Pacific Ocean on Dec. 11.
The burn with the Orion spacecraft’s orbital maneuvering system engine is planned at 4:53 p.m. EST (2153 GMT). The 6,000-pound-thrust, hydrazine-fueled engine will fire for 1 minute and 45 seconds, enough to nudge the spacecraft out of its distant retrograde orbit around the moon, where it’s been flying since Nov. 25. The maneuver will change Orion’s velocity by roughly 310 mph (454 feet per second; 498 kilometers per hour).
The orbit departure burn is the fourth of five main engine firings the Orion spacecraft will execute on on NASA’s Artemis 1 mission, a test flight of the agency’s new deep space capsule and heavy-lift rocket before astronauts strap in for a trip around the moon on Artemis 2, scheduled for late 2024. NASA plans to land astronauts on the moon beginning with Artemis 3, debuting a commercial moon lander derived from SpaceX’s Starship rocket program.
Artemis 1 launched Nov. 16 from NASA’s Kennedy Space Center in Florida on the inaugural flight of the Space Launch System moon rocket, a 322-foot-tall (98-meter) behemoth that took a decade and more than $20 billion to develop.
The rocket performed flawlessly, NASA officials said, sending the Orion capsule on a five-day track toward the moon, where it zoomed about 80 miles (130 kilometers) from the surface Nov. 21. The close flyby used lunar gravity to swing the Orion spacecraft into a distant retrograde orbit, or DRO, some 50,000 miles (80,000 kilometers) from the moon.
Another main engine burn Nov. 25 placed the Orion spacecraft into the DRO, so named because it is not a low-altitude orbit like the Apollo capsules of the 1960s and 1970s flew in, and because Orion is moving around the moon in the opposite direction the moon travels around Earth.
Mission planners chose the orbit for the Artemis 1 mission for several reasons. First, the Orion spacecraft’s propulsion system does not have the capability to steer the capsule into a low-altitude orbit around the moon as the Apollo missions did. And the DRO is stable because it is near the balance point between the pull of gravity from Earth and the moon, reducing the fuel Orion needs to burn to maintain its orbit.
The Orion spacecraft spent about six days in the distant retrograde orbit performing tests and checkouts, long enough to complete one-half of a lap around the moon. On Saturday, the capsule broke the distance record for a spacecraft designed to carry humans into space and return them to Earth, according to NASA.
The record was previously set on NASA’s Apollo 13 mission, which reached a distance of 248,655 miles (400,171 kilometers) from Earth when it looped around the far side of the moon with a three-man crew in 1970. Apollo 13’s moon landing was aborted when one of its oxygen tanks exploded on outbound journey from Earth, and the spacecraft steered onto a “free return” trajectory that took it farther from Earth than any of the other Apollo missions.
While there are no humans on-board Artemis 1, there are three instrumented mannequins inside the Orion spacecraft’s pressurized cabin to gather data on accelerations, vibrations, and radiation on the flight to the moon and back.
The Orion spacecraft reached its greatest distance from Earth on Monday, Nov. 28, at more than 268,500 miles (432,000 kilometers).
After Thursday’s 105-second main engine burn to leave the distant retrograde orbit, the moon’s gravity will pull the Orion spacecraft toward a high-speed flyby just 79 miles (127 kilometers) from the surface on Monday, Dec. 5. The Orion main engine will fire again at 11:43 a.m. EST (1643 GMT) for 3 minutes and 27 seconds, the spacecraft’s longest burn on the Artemis 1 mission.
The return powered flyby maneuver will aim Orion toward its splashdown point in the Pacific Ocean. The spacecraft will jettison its European service module just before re-entry, then perform two dips into the atmosphere to bleed off speed before deploying parachutes for splashdown off the coast of San Diego on Dec. 11.
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