Ten Republican Congress members led by Rep.
The letter, dated Thursday, also cited SpaceX's prior explosion in June 2015 while carrying cargo for NASA to the International Space Station. The Hawthorne space company led its own investigation for that launch failure.
Under federal law, SpaceX is allowed to conduct its own investigation. SpaceX, whose full name is Space Exploration Technologies Corp., and other companies lobbied successfully to extend the law last year. The FAA oversees such investigations.
A recent report from NASA's office of inspector general on SpaceX's 2015 launch failure similarly asked whether SpaceX's lead role in its own investigation "raises questions about inherent conflicts of interest," though it said the investigation was "transparent" and noted that outside observers such as the FAA and Air Force had access to the data and analysis.
The Congress members said the investigation responses raised "serious concerns about the authority provided to commercial providers and the protection of national space assets."
"Although subject to FAA oversight, it can be asserted the investigation lacked the openness taxpayers would expect before a return-to-flight," the letter says. "We feel strongly that the current investigation should be led by NASA and the Air Force to ensure that proper investigative engineering rigor is applied and that the outcomes are sufficient to prevent NASA and military launch mishaps in the future."
In 2015, SpaceX was certified by the Air Force to carry national security satellites, breaking up a longtime and lucrative monopoly held by a joint venture of Boeing Co. and
Coffman's congressional district includes United Launch Alliance's headquarters. Many of the congressmen represent states where ULA has operations.
SpaceX declined to comment on the letter. NASA did not respond immediately to a request for comment.
The FAA said it "has not had a chance to review" the letter but would respond "in a timely manner."
The letter also includes a list of questions for each agency including whether the Air Force will reconsider certification of the Falcon 9 rocket for national security launches; whether NASA will reevaluate the use of the Falcon 9 rocket for its commercial resupply and upcoming commercial crew missions; and whether the FAA would reconsider issuing licenses to SpaceX after its September launch pad explosion.
The Air Force had not received the letter, but if it does, it will respond directly to the congressman, said Ann Stefanek, an Air Force spokeswoman.
SpaceX's investigation into its September explosion is being aided by NASA and the Air Force. Last week, SpaceX said it found evidence that a "large breach" took place in the helium system of the rocket's second-stage liquid oxygen tank.
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Sept. 30, 10:50 a.m.: This article was updated with additional information about a NASA inspector general report on the SpaceX June 2015 explosion.