After 10 days, over 800,000 km traveled, and a historic flyby of the Moon, Artemis II is set to return to Earth on Friday evening. Orion CM-003 Integrity, which has served as the home for the mission’s four-person crew since April 1, will begin reentering Earth’s atmosphere over the Pacific Ocean before ultimately splashing down off the coast of San Diego, California.
Integrity‘s splashdown is targeted for Friday, April 10, at 5:07 PM PDT (00:07 UTC on Saturday, April 11). Entry interface, or the moment when Integrity enters Earth’s atmosphere, will begin 13 minutes before splashdown at 4:54 PM PDT (11:54 UTC). At that moment, Orion will be traveling at a velocity of over 38,000 km per hour, marking the fastest atmospheric reentry performed by a crewed spacecraft since Apollo 17 in 1972.
Artemis II mission recap
Artemis II launched atop a Space Launch System (SLS) rocket from Launch Complex 39B (LC-39B) at the Kennedy Space Center on Wednesday, April 1, at 6:35 PM EDT (22:35 UTC). Situated within Orion Integrity were three NASA astronauts — commander Reid Wiseman, pilot Victor Glover, and mission specialist Christina Koch — and a Canadian Space Agency (CSA) astronaut, mission specialist Jeremy Hansen.
All components of SLS and Orion performed nominally during launch and ascent, with SLS placing Integrity on a trajectory so accurate that several of the pre-planned orbital trajectory correction burns were canceled.
Following a proximity operation demonstration with SLS’s Interim Cryogenic Propulsion Stage (ICPS) upper stage on Flight Day 1, Integrity fired the AJ10 main engine on its European Service Module (ESM) on Flight Day 2 for the translunar injection burn — the first to be performed in over 52 years. Over the next several days, the Artemis II crew conducted a variety of experiments, demonstrations, and tests with Orion, validating several key systems and procedures for future Artemis missions to the Moon.
Artemis II launches from LC-39B on April 1. (Credit: Max Evans for NSF)
Finally, on Flight Day 6, after entering the lunar sphere of influence the day before, Integrity and her crew performed a flyby of the Moon. During their planned seven-hour observation period, the crew viewed the Moon’s near and far sides through Orion’s windows, imaging the lunar surface and discussing various regions of scientific interest with science teams on Earth. During a communications blackout period, as the Moon blocked Integrity‘s view of Earth, the crew reached the furthest point of their journey — 406,771 km from Earth — breaking Apollo 13’s record as the most distant human spaceflight in history. At its closest approach to the Moon, Integrity was 6,545 km from the lunar surface.
The mission’s lunar flyby period was capped by a solar eclipse, during which, from the crew’s perspective, the Moon eclipsed the Sun for 57 minutes. The eclipse allowed observations of the solar corona and Earthshine, reflected light from Earth that illuminates the night side of the lunar surface. During the entire lunar flyby, the crew regularly captured photos and videos, some of which have already been released by NASA.
On their return journey from the Moon, the crew conducted additional demonstrations and experiments with Orion, including a radiation-shielding demonstration. The crew also took time to debrief the lunar flyby with the science team, discussing notes and analyzing imagery taken during the flyby. The four crew members also participated in several pre-planned public affairs events and media conferences during their outbound and return trips.
Image of the solar eclipse seen by the Artemis II crew on April 6. (Credit: NASA)
Return to Earth
Flight Day 10, the day of reentry and landing, will begin with Christina Koch and Jeremy Hansen continuing to configure Integrity for its return to Earth. This includes removing cargo and locker netting, re-installing their seats in the center of Orion, and securing loose items in the capsule. The crew will also review entry timelines, participate in a recovery weather briefing, and be updated on the status of recovery forces in the Pacific.
As with launch, a variety of weather criteria must be met before a spacecraft’s landing. For Artemis II’s splashdown and recovery operations, wave height, wind speed, and cloud coverage must all be within certain pre-determined ranges, and the chosen splashdown site must have good visibility conditions. Specifically, there cannot be any precipitation or thunderstorms within 55.56 km of the chosen landing site, wave height must be below 1.8 m, and wind speed must be under 25 knots.
Integrity will complete its third and final return trajectory correction burn at a mission elapsed time (MET) of MET+08:20:33 days. This final burn ensures that Integrity is on the correct trajectory for reentry into Earth’s atmosphere. Artemis II will not require a deorbit burn as many low-Earth orbit missions do, as the mission’s return trajectory was established with the translunar injection burn on Flight Day 2. Any trajectory correction burn since Flight Day 2 has made only very small corrections to keep the spacecraft on the correct path.
After donning their orange pressure suits and strapping themselves into their seats, the crew and Integrity will be fully prepared for launch. Integrity and its ESM will separate 42 minutes before splashdown, and at 4:37 PM PDT (11:37 UTC), the capsule will conduct a trajectory-adjustment burn and a series of roll maneuvers to create distance from the ESM. The ESM will burn up in the atmosphere during reentry and not be recovered.
Infographic highlighting Artemis II’s reentry sequence. (Credit: NASA)
Integrity will then cruise toward Earth’s atmosphere, continuing to accelerate all the way to entry interface. Just moments before entry interface begins, Integrity will reach its maximum velocity for the mission — 38,405 km per hour.
Entry interface will begin when Integrity is 122 km above Earth’s surface. At 4:53 PM PDT (11:53 UTC), as plasma begins to form around the exterior of the capsule due to atmospheric friction, Integrity will enter a pre-planned communications blackout period, which is expected to last approximately six minutes. Integrity is forced into this communications blackout period due to the exterior plasma blocking radio communications to or from the capsule. The capsule will experience peak heating during this six-minute period, and the crew is expected to experience up to 3.9 Gs.
Once Integrity exits the blackout and communications are reestablished with the crew, the capsule will continue descending through the atmosphere before jettisoning its forward bay cover. At 5:03 PM PDT (00:03 UTC), at an altitude of 6.70 km, the three drogue parachutes will deploy, beginning the process of slowing Integrity to its splashdown velocity. A minute later, at an altitude of 1.83 km, the drogue parachutes will be cut, and the main parachutes will deploy. After fully unfurling, Integrity‘s velocity will significantly slow, and the capsule will gently descend through the atmosphere at about 32 km per hour.
Artemis I’s Orion CM-002 under parachutes after a successful reentry in December 2022. (Credit: NASA)
Finally, after a historic journey spanning over 800,000 km, Artemis II will splash down in the Pacific Ocean off the coast of San Diego, California, at 5:07 PM PDT (00:07 UTC).
Immediately following landing, Integrity‘s reaction control system, which uses toxic hypergolic propellants, will be shut down and safed. Stationed near Integrity‘s landing zone will be the USS John P. Murtha, from which recovery teams will be deployed to the landing site via helicopters and boats. The Artemis II crew will be assisted out of Integrity and then returned to the USS John P. Murtha by helicopter within two hours after splashdown, where they will undergo medical evaluations.
Once cleared from their post-splashdown medical evaluations, the crew will be returned to the California coast to board an aircraft and travel to NASA’s Johnson Space Center in Houston, Texas. Meanwhile, Integrity will be powered down, recovered, and brought to shore at a later time.
Artemis II’s reentry corridor. (Credit: NASA)
Orion heat shield investigation and trajectory alterations
Artemis I, the uncrewed precursor mission to Artemis II, launched in November 2022 with Orion CM-002, successfully splashing down in the Pacific Ocean in early December. Following post-flight inspections of Orion after reentry and splashdown, NASA engineers noted significant charring and excessive loss of the AVCOAT ablative material used on the capsule’s heat shield. While NASA reported that temperatures within the habitable crew compartment of Orion never exceeded acceptable limits, the agency undertook a large-scale investigation into the Artemis I heat shield issues.
Artemis I marked the first time NASA utilized a skip guidance entry trajectory for reentering Earth’s atmosphere. During reentry, Orion dipped into the upper regions of Earth’s atmosphere, using atmospheric drag to decelerate, before using its aerodynamic lift to increase altitude and “skip” out of the atmosphere. The capsule then completed a second and final descent into the atmosphere, culminating in a splashdown in the Pacific. This “two-step” reentry profile allows for more trajectory flexibility and increased range capabilities, while also reducing the overall G-force load astronauts within the capsule experience.
The heat shield used by Orion CM-002 on Artemis I. (Credit: NASA)
NASA’s investigation into the Artemis I heat shield revealed that the significant AVCOAT charring and loss were due to this skip guidance entry profile. During Orion’s first dip into the atmosphere, the capsule’s exterior and heat shield experience heating from atmospheric friction. While exterior heating rates decreased between the first and second dips, the AVCOAT material retained thermal energy and released gases associated with its ablative material. Due to AVCOAT’s lack of permeability (or porosity), however, these gases became trapped within the material, and when atmospheric pressure began to increase during the second dip, the AVCOAT material in the heat shield experienced cracking and uneven ablation.
At the conclusion of the review, NASA announced it would use the same AVCOAT-based heat shield design from Artemis I on the Orion set to fly on Artemis II, opting to modify the capsule’s reentry trajectory rather than replace the heat shield. This modified trajectory will see Integrity take a steeper descent angle during reentry than Orion CM-002 on Artemis I, limiting the heat shield’s exposure to the heating environment that created the erosion seen on Artemis I. This modified reentry trajectory will not utilize the “skip” technique used on Artemis I.
In addition to our YouTube livestream, NSF’s social media accounts, particularly on X, will post regular updates on Artemis II’s return to Earth.
(Lead image: Earth is seen through the window of Orion Integrity during the Artemis II mission. Credit: NASA)
The post Artemis II set for return to Earth after historic 10-day mission around the Moon appeared first on NASASpaceFlight.com.
Comments
Post a Comment