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WASHINGTON – NASA will not repair a faulty electronics unit on the recently completed Orion spacecraft for the Artemis 1 mission after concluding that there is sufficient redundancy in the overall system.
In a Dec. 17 statement, NASA said it had decided to “use as is” one of the eight power and data units (PDUs) on the Orion spacecraft, which provide communications between computers. of the spaceship and other components. One of the two redundant channels of one of the two communication cards of this PDU is not functioning.
NASA announced the problem with the PDU on November 30, saying only that it “solves the problem.” The issue was first reported by The Verge, which said presentations by prime contractor Lockheed Martin warned that it could take up to a year to replace the PDU because it is located in an adapter between the crew module and the service module which is inaccessible now that the two modules are mated.
This time estimate assumed that the crew module would be dismantled from the service module, the PDU repaired, and the two modules combined again and tested. An alternate option could complete repairs in just four months, but would require removing the adapter panels to reach the PDU, which the hardware was not designed for.
NASA, in its statement on the decision not to replace the PDU, did not go into details on repair options, but said the risks of damaging the spacecraft during the PDU repair outweighed on any loss of data in the event of a complete malfunction of the unit.
Engineers, the agency said, “determined that due to the limited accessibility to this particular box, the degree of intrusion into the spacecraft’s overall systems, and other factors, the risk of damage collateral outweighed the risk associated with losing a leg of redundancy. in a highly redundant system. ”
“NASA has confidence in the health of the overall power and data system, which has undergone thousands of hours of powered operations and tests,” the agency added, noting that the PDU in question was still ” fully functional ”.
Even before the statement, NASA officials were playing down the possibility of performing a thorough repair of the spacecraft to replace the PDU. “You will get a first report, and the first report will show all the worst possibilities,” Ken Bowersox, deputy associate administrator of NASA’s human exploration mission and operations directorate, said at a press briefing. Dec. 7 on a planned science report for the Artemis 3 lunar landing mission. “At best, we can find that this is something we can live with.”
At the time of this briefing, Bowersox said NASA was still studying the issue, but was optimistic that it wouldn’t have a major effect on the Artemis 1 mission. “Looking at it, we really don’t think it will have a real impact. significant impact on the final schedule, ”he said.
With the decision not to replace the PDU, NASA is moving forward with the final closure of the spacecraft. In mid-January, it will be moved from the Kennedy Space Center facility where it was assembled to the multi-load processing facility there, where it will be powered and ready to be installed on the space launch system. .
The critical path for the launch of Artemis 1, still slated for November 2021, remains the main stage of SLS, which undergoes a series of tests called Green Run at the Stennis Space Center. NASA said on December 17 that it had restarted preparations for a refueling test called a wet dress rehearsal after it canceled a first attempt at that test in early December because liquid oxygen flowed into the center stage at temperatures slightly higher than desired.
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