NASA is choosing to fly its next Orion deep space crew capsule “as it is” next year, after the agency discovered that one of the spacecraft’s power tools had failed. Engineers thought about replacing the instrument before the vehicle flew, but eventually decided that there was enough redundancy in the system to withstand the defective component.
“NASA is confident in the health of the overall energy and data system, which has gone through thousands of hours of operations and electricity tests,” the agency wrote in a blog post announcing the decision. “Engineers will perform additional tests and continue to monitor the health of the spacecraft while Orion is up and running to provide continued confidence in the system.”
In November, NASA engineers and Lockheed Martin, Orion’s main contractor, discovered that part of an instrument known as a power and data unit or PDU had failed. One of the eight PDUs on the Orion, the instrument is needed to activate various functions while the capsule is in flight. It is also in a rather difficult place to reach. This PDU is located in the adapter that connects the Orion capsule to its service module, a cylindrical trunk that supports the vehicle during flight.
Replacing the PDU would not be exactly a quick fix. Engineers were looking at options that would take four to 12 months to complete. The remedies would have involved either dismantling the vehicle or tunneling through the exterior walls to reach the PDU, and the extra time could have caused a delay in the target date of the Orion launch in November 2021. Instead, NASA chose not to replace the PDU. The tool can still work; it has just lost one of its power channels used for redundancy. This means that this PDU will fly without a backup system in case its main channel fails.
NASA claims that fixing the PDU was more risky than flying with PDU. “[Engineers] established that, due to the limited accessibility of this box, the degree of intrusion of global spacecraft systems and other factors, the risk of collateral damage exceeded the risk associated with the loss of a redundancy leg in an extremely redundant system. ” “Therefore, NASA has decided to continue processing the vehicles,” the agency wrote in its blog post.
No one will be on board this Orion spacecraft when it flies. The vehicle is expected to fly unmanned over NASA’s future massive rocket, Space Launch System or SLS. That rocket is also being tested before that flight and it is unclear whether it will be ready by November 2021.