NASA Tailors Artemis I-III Lunar Mission Trajectories
HOUSTON—NASA’s uncrewed Artemis I initial test flight of the Space Launch System (SLS) rocket and Orion crew capsule will exercise the first of three flight trajectory strategies intended to kick off the return of human explorers to the lunar surface.
Preparations for the 42-day Artemis I mission are proceeding toward launch from NASA’s Kennedy Space Center on Aug. 29 at 8:33 a.m. EDT, the opening of a 2-hr. departure window, with backup launch opportunities available on Sept. 2 and Sept. 5.
Artemis I will utilize a lunar Distant Retrograde Orbit (DRO). Artemis II, a crewed test flight of the SLS and Orion planned for late 2024, will use a hybrid lunar free trajectory (LFRT) around the Moon. Artemis III, planned for 2025, is to feature the first post-Apollo human landing at the lunar south pole to initiate an annual cadence of astronaut launches. Artemis III is to initiate human operations in the Near Rectilinear Halo Orbit (NRHO) that is to be the long-term home to the Gateway—a small, space station-like outpost and the planned staging point for future human lunar landings. Assembly of the multi-module, human-tended Gateway is planned to begin in late 2024.
Each of the first three Artemis mission trajectories has a specific purpose. The Artemis trajectory is to expose the Orion systems to the SLS launch and cislunar environments and prepare the crew capsule for a daylight splashdown in a Pacific Ocean recovery zone off the coast of San Diego. Following the flight, the spacecraft and its thermal protection system will undergo thorough assessments.
After liftoff, the solar-powered Orion, still attached to the SLS upper stage, will undergo a series of Earth orbit-raising maneuvers that are to set up a 10-min. translunar injection (TLI) maneuver 80-90 min. into flight. The TLI is to send the crew capsule and its European Space Agency-provided service module on their way to the Moon.
After anticipated outbound correction maneuvers and experiencing the forces of lunar gravity, Orion’s service module propulsion system is to conduct an Outbound Powered Flyby maneuver with the capsule 60 mi. over the lunar surface late on the sixth day of the mission to initiate entry into DRO. DRO is so named because the trajectory is to take the spacecraft in the opposite direction the Moon is orbiting the Earth.
“We will be holding our breath,” Artemis I Lead Flight Director Rick LaBrode told participants in an Aug. 5 series of pre-mission briefings at NASA’s Johnson Space Center. “Orion will be on the other side of the Moon. We won’t have communications with it.”
Early on the mission’s 10th day, Orion will enter DRO. After traveling about 240,000 mi. to reach the Moon, DRO will lead the capsule out another 40,000 mi. On the mission’s 11th day, Orion is to surpass by about 30,000 mi. the record distance of just more than 249,000 mi. from Earth reached by the three-member crew of the ill-fated Apollo 13 mission in April 1970.
The flight plan calls for Orion to spend a little more than two weeks in DRO.
If Artemis I maintains a 42-day flight profile, Orion will carry out a DRO exit burn on the 24th day, followed by the critical Return Powered Fly-by maneuver on the 35th day, or early Oct. 3, taking the spacecraft about 500 mi. from the lunar surface.
“That is the most critical burn for the mission,” LaBrode said. “If something happens and we don’t execute it, there is a loss of the Orion capsule. We have to do that right.”
With success, the Artemis mission will come to a conclusion and splashdown on Oct. 10 at 11:53 a.m. EDT, with U.S. Navy recovery vessels and NASA and military personnel standing by.
Artemis II is also to kick off the first crewed test flight of the SLS and Orion by launching into an elliptical Earth orbit. Using SLS upper-stage propulsion, the Orion and its four astronauts will aim for a 235 x 68,000-mi. elliptical orbit, while checking out life support systems and manually executing a proximity operations demonstration after separating from the upper stage. Then using Orion’s service module propulsion, NASA’s Mission Control will command a translunar injection (TLI) burn to propel the Orion crew on its way to the Moon and a hybrid Lunar Free Return Trajectory.
The four-day transit is to take the Orion an estimated 4,600 mi. beyond the Moon’s far side on a figure-eight track that will rely on the Earth-Moon gravity field rather than spacecraft propulsion for a four-day return to Earth, ending a mission estimated to last just more than 10 days in total.
Artemis III, a planned four-person mission that will feature a lunar south pole landing by two of the astronauts, is to place its crew in an NRHO, where it is to dock with a NASA-contracted SpaceX Human Landing System that will transport two of the astronauts to the surface for a six- or seven-day stay, then back to Orion.
In late June, a Rocket Lab Electron launch from New Zealand sent NASA’s $32.65 million small Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (Capstone) satellite on its mission to explore NHRO’s gravitational stability, Earth-Moon communications potential, autonomous navigation assets and other factors. Capstone’s maneuver into NRHO is planned for Nov. 13, the start of at least six months of operations led by Advanced Space, which owns the spacecraft.
Once assembled, Gateway is to support missions to and from an Artemis Base Camp, which is to be established at the lunar south pole, as well as simulated crewed missions to Mars. Gateway is planned for 15 years of operations.
The unusual NRHO has a high point of 43,500 mi. over the lunar south pole and low point of 1,000 mi. over the lunar north pole. The orbital period is one week, enabling Gateway to spend most of its time over the base camp.