by
In a partial response to a report alleging evidence of several major irregularities during a recent launch of private astronauts that could affect a crew of NASA astronauts launched last month, the space agency issued a statement denying the allegations. However, the same statement also revealed that SpaceX recently discovered a different problem with a different Crew Dragon spacecraft component during ground tests.
On May 23, Space Explored published a report claiming that a SpaceX Crew Dragon spacecraft encountered significant problems during Axiom-1, the company’s first all-private astronaut launch at the International Space Station (ISS). According to information and a possible internal note from SpaceX, one of the Dragon toxic propellants leaked during the 17-day flight, destroying or weakening parts of its thermal shield and “[caused] dangerously excessive wear on re-entry “. In general, the report seemed to have good sources and even claimed that the NASA Center for Engineering and Security (NESC) had launched an investigation. In addition, when approached for comment, neither NASA nor SpaceX were initially willing to speak to the file, which also meant that neither of them denied the allegations.
A day later, NASA issued an official statement to Space Explored, expressly denying that there was a propellant leak, thermal shield contamination or excessive thermal shield wear in any of the “recent re-entries of the Dragon crew.”
NASA has also dismissed concerns about the reuse of a previously flown Cargo Dragon 2 thermal shield. structure at Crew-4, which was launched just two days after the Axiom-1 recovered and is scheduled to spend another four to five months in orbit. He also noted that the reuse of the Dragon’s thermal shield tiles – structures that take the heaviest weight of re-heating and immerse in salt water after each shipment – are extremely limited and have been attempted only occasionally Load Dragon missions.
At the same time, NASA revealed that “a new composite thermal shield structure intended for flight in the Crew-5 did not pass the acceptance test” at the SpaceX plant in Hawthorne, California Dragon. The unrelated failure of the test was attributed to a construction defect and NASA showed no sign of serious concern in its statement, suggesting that the problem may be less serious than it sounds. In response, NASA says SpaceX will simply use a different composite thermal shield structure for the Crew-5, which is scheduled to launch no earlier than September 2022 (NET).
The data related to the recent re-entries of the Dragon crew was normal – the system worked as designed without question. There was no hypergol leak on the return of a Dragon mission with a crew or contamination with the thermal shield causing excessive wear. SpaceX and NASA conduct a full mechanical review of the thermal shield’s thermal protection system after each return, including before the launch of the Crew-4 mission currently stationed on the International Space Station. The composite structure of the heat shield (structure under the tile) was repositioned according to the normal design and renovation procedures. The thermal protection system on the main thermal shield for the Crew-4 was new, as it was for all human spaceflight missions. SpaceX has only demonstrated the reuse of selected PICA (Phenolic-Impregnated Carbon Ablator) tiles, which is a lightweight material designed to withstand high temperatures as part of the thermal shield in cargo flights.
NASA and SpaceX are currently in the process of determining the distribution of material for the organization’s upcoming SpaceX Crew-5 mission, including the Dragon thermal shield. SpaceX has a rigorous testing process to put every component and system at its own pace to ensure security and reliability. In early May, a new composite thermal shield designed for flight in the Crew-5 did not pass an acceptance test. The test did its job and found a construction defect. NASA and SpaceX will use another in-flight thermal shield that will undergo the same rigorous pre-flight tests.
Crew safety remains a top priority for both NASA and SpaceX, and we continue to aim for the Crew-5 launch in September 2022.
NASA – May 24, 2022
Some quirks remain. Although NASA’s outspoken denial should be taken as the final word on the matter, it is still very unusual for NASA and SpaceX to deny or fail to publicly deny the allegations within hours of Question. This could simply be due to poor internal and external communication between NASA and SpaceX or the desire of both parties to withhold information from taxpayers about systems and technologies for which taxpayers themselves have paid.
On the other hand, after the Crew Dragon Demo-2 run with more than expected thermal shield wear in 2020, it is almost impossible to imagine that NASA and SpaceX would have launched the Crew-4 two days later. the recovery of Axiom-1 without verifying with certainty that the corrosion of the thermal shield was within normal limits. Dragon thermal shield tiles from SpaceX Phenolic-Impregnated Carbon Ablator (PICA-X) are designed to corrode [PDF] less than an inch thick in 2017 ~ 7.5 cm (3 inches) after each re-entry. Musk has gone even further, stating in 2012 that “[PICA-X] it can potentially be used hundreds of times to re-enter Earth orbit with only a slight degradation each time. ” If true, it would be extremely It is difficult even for a quick inspection after the flight of the Axiom-1 Dragon capsule to lose what Space Explored described as “dangerously excessive wear”.
Theoretically, during recovery, even a small propellant leak should also have been immediately detected by the SpaceX recovery team, as the first part of the practical procedure includes a small group with gas masks and detectors approaching the floating capsule to ensure that it is safe for others to approach. Crew Dragon’s liquid monomethylhydrazine (MMH) fuel and nitric oxide oxidant (NTO) are extremely toxic in small quantities and MMH is a known carcinogen.
Overall, the news of a possible propellant leak and abnormal thermal shield performance appears to have been a false alarm, although – coincidentally or not – a seemingly minor anomaly with a Crew Dragon thermal shield structure that had not been flown. He made happen earlier this month. Despite this anomaly, Crew-4 and Crew-5 go by different names and NASA seems to be happy with the performance of the Crew Dragon during many recent launches and recoveries.
