Mission Summary
Astrobotic’s Peregrine Mission One (PM1), the first American commercial lunar lander, launched aboard United Launch Alliance’s maiden Vulcan rocket on January 8, 2024 with the goal of landing on the Moon. While Peregrine successfully separated from Vulcan and activated its systems, a significant anomaly occurred during propulsion system initiation that prevented the spacecraft from landing on the lunar surface.
During the propulsion system commissioning, a helium pressure control valve (PCV2) failed to properly reseat after actuation, causing uncontrolled helium flow into the oxidizer tank. This led to rapid over-pressurization and rupture of the oxidizer tank. The propulsion system could no longer achieve the pressures needed for lunar landing.
After the anomaly, Astrobotic stabilized the spacecraft and shifted priorities to gathering data for the investigation, operating payloads to collect science, and testing subsystems to increase technology readiness levels for future missions. Peregrine operated for 10 days and 14 hours, traveling over 535,000 miles to and from cislunar space before conducting a controlled reentry into Earth’s atmosphere over the South Pacific on January 18, 2024.
Anomaly Investigation Findings
Astrobotic assembled a review board of 34 government, industry and in-house experts chaired by Dr. John Horack of Ohio State University to investigate the mission anomaly. The board concluded the most likely cause was a mechanical failure of the PCV2 valve, leading to a loss-of-seal capability.
Spacecraft telemetry data confirmed the location and timing of the anomaly coincided with the actuation of PCV2. Ground testing replicated the failure mode, showing the threaded joint in the valve loosened and the primary O-ring seal was damaged.
The board traced contributing factors that led to PCV2’s failure:
- In 2019, Astrobotic contracted an outside vendor to develop the propulsion feed system.
- In 2021, the vendor had technical and supply chain issues that jeopardized the schedule.
- In early 2022, Astrobotic terminated the vendor’s contract and completed the system in-house.
- From April-Nov 2022, Astrobotic encountered repeated failures with the vendor’s pressure control valves during testing.
- In Aug 2022, Astrobotic pivoted to an alternate PCV supplier to maintain schedule.
- The new valves were installed. PCV1 encountered leaks but was repaired. PCV2 passed testing.
- PCV2 was still a risk but likelihood of failure was low after successful acceptance testing. Its location made repair difficult without major disassembly and schedule impact.
- Astrobotic decided to proceed to flight without alterations to PCV2 to avoid missing launch.
Corrective Actions
The review board recommended corrective and preventative actions Astrobotic is implementing to mitigate risk on future missions:
- Redesign primary PCVs to address mechanical sealing flaw and test all valve designs for similar issues
- Use multiple, dissimilar PCVs on future landers so no single failure results in loss of mission
- Embed Astrobotic personnel at key suppliers to manage schedule, quality and performance
- Resolve the 24 total in-flight anomalies encountered, 8 of which were mission critical
- Hire additional quality management personnel to enhance mission assurance
- Strategically reinforce workforce with industry experts Steve Clarke and Frank Peri to strengthen mission assurance
Achievements and Future Missions
Although PM1 did not achieve lunar landing, it successfully operated in cislunar space for over 10 days and raised nearly all spacecraft subsystems to technology readiness level 9. With this flight heritage, Peregrine remains available for future science, exploration, defense and commercial missions.
Astrobotic’s next mission, Griffin Mission One, will launch by end of 2025 to the lunar south pole carrying payloads for NASA, the Canadian Space Agency, and European Space Agency. Astrobotic remains committed to making the Moon accessible through successful, precise, and affordable lunar landings.
Peregrine Mission Account
Launch, Separation and Power
Peregrine was encapsulated and fueled in preparation for launch in late 2023. On January 8, 2024, Vulcan lifted off at 2:18am ET carrying PM1. The rocket successfully placed Peregrine into its targeted translunar injection orbit.
At 3:09am, PM1 separated from Vulcan’s upper stage, activating power to the lander. By 7 minutes after separation, PM1 established downlink with Astrobotic Mission Control and was in a nominal attitude with all subsystems functioning as expected.
The PCV2 Failure
PM1 began its autonomous propulsion system initiation sequence after separation. Helium flows from the pressurant tank to the fuel and oxidizer tanks through pressure control valves PCV1 and PCV2 to pressurize the system.
The priming valves were actuated and the system was nominal. PCV1 then actuated and performed nominally. However, when PCV2 was actuated, telemetry showed continued uncontrolled pressure rise in the oxidizer tanks and decrease in the helium tank, indicating PCV2 failed to properly reseat.
Less than 90 seconds later, the oxidizer tank pressure sensors pegged at their maximum readable value. Astrobotic assessed an oxidizer tank likely ruptured due to over-pressurization, causing oxidizer to leak and torque the spacecraft into a tumble.
Attempts to re-seat PCV2 were unsuccessful as helium pressure continued decreasing, confirming an internal leak through PCV2 even when commanded closed. This was later determined as the most likely root cause of the mission anomaly.
Lunar Transit and Mission Operations
The oxidizer leak made Peregrine’s ability to perform trajectory correction maneuvers and lunar orbit insertion burns uncertain. The abnormal mixture ratio also risked heat damage to the engines.
After stakeholder input, Astrobotic decided to call off the landing attempt and instead focus on maximizing Peregrine’s remaining lifespan to return as much spacecraft and payload data as possible. Payload operators worked to develop new procedures to collect data during each communication window.
Four days post-launch, Peregrine reached lunar distance while remaining stable and operable. It collected data from all 9 communicating payloads, with 3 gathering publishable scientific data. Most of the lander subsystems were also operated and raised to TRL 9.
As Peregrine returned from the Moon, updated orbit predictions showed it was on a collision course with Earth due to the ongoing leak. Astrobotic consulted with NASA and determined a controlled reentry was the safest option to prevent creating cislunar orbital debris.
A series of short engine pulses were performed to target Peregrine’s reentry over an unpopulated region of the South Pacific. After 10 challenging days of operations, Peregrine reentered Earth’s atmosphere on January 19, 2024.
Summary
PM1 demonstrated pioneering commercial lunar missions will face failures on the path to sustainable success. But through resilience, adaptability, and diligence in learning from experience, Astrobotic’s team maximized PM1’s duration, tested critical systems, and enabled a safe controlled reentry.
The lessons from PM1 are already being applied to make Astrobotic’s next mission, Griffin Mission One, and future commercial lunar missions more reliable and capable of unlocking the Moon’s vast potential for science, exploration and commerce.
