NASA advisory board worried about SpaceX fueling processes
Experts on a NASA advisory board have expressed concerns about SpaceX’s plan to fuel Falcon 9 with astronauts aboard. The safety advisory springs, in part, from the explosion of a Falcon 9 rocket during a static test on September 1.
According to a Reuters report, during a conference call on October 31, former Apollo astronaut Tom Stafford, who chairs the International Space Station Advisory Committee, conveyed the group’s concerns: “It was unanimous … Everybody there, and particularly the people who had experience over the years, said nobody is ever near the pad when they fuel a booster.”
Stafford’s teleconference comments were accompanied by a letter he addressed to NASA Associate Administrator Bill Gerstenmaier discussing the fueling issue. The letter stated:
There is a unanimous, and strong, feeling by the committee that scheduling the crew to be on board the Dragon spacecraft prior to loading oxidizer into the rocket is contrary to booster safety criteria that has been in place for over 50 years, both in this comttry and internationally. Historically, neither the crew nor any other personnel have ever been allowed in or near the booster during fueling. Only after the booster is fully fueled and stabilized are the few essential people allowed near it.
Furthermore, in addition to the personnel risk, there is the risk of operating the engines outside their design input conditions. As an experienced “Prop” guy you know the problem here as well as anyone. Pump-fed chemical engines require a sufficient and consistent input pressure to reduce the likelihood of cavitation or unsteady flow operations. We are concerned that there may be insufficient precooling of the tank and plumbing with the current planned oxidizer fill scenario, and without recirculation there may be stratification of oxidizer temperature that will cause a variation in the input conditions to the oxidizer pump.
In summary, we are deeply concerned about introducing the practice of fueling with the crew onboard, and about the lack of even a recirculation pump for oxidizer conditioning on Falcon 9.
The Los Angeles Times reported that this recommendation would not affect SpaceX’s progression returning to flight. However, it could delay the company’s plans to launch astronauts to the space station under the Commercial Crew Program.
The causes of the September 1 explosion are still under investigation, but SpaceX has stated on its blog that they have been able to replicate the anomaly. The problem derives from a failure of a composite overwrap pressure vessel (COPV) failure containing liquid helium. “These conditions are mainly affected by the temperature and pressure of the helium being loaded.”
Members of the eight-member Advisory Committee includes veterans of NASA’s Gemini, Apollo, and Space Shuttle programs. The Committee noted that all previous space launch vehicles carrying people have been fueled before astronauts got to the launch pad.
In a statement prepared by NASA on November 1, 2016:
Spacecraft and launch vehicles designed for the Commercial Crew Program must meet NASA’s safety and technical requirements before the agency will certify them to fly crew. The agency has a rigorous review process, which the program is working through with each commercial crew partner. Consistent with that review process, NASA is continuing its evaluation of the SpaceX concept for fueling the Falcon 9 for commercial crew launches. The results of the company’s Sept. 1 mishap investigation will be incorporated into NASA’s evaluation.
Independent advisory groups provide input on commercial crew safety considerations, among which the Aerospace Safety Advisory Panel is the primary independent adviser for commercial crew activity. Other groups, such as the ISS Advisory Committee, also seek information, and we treat all inquiries seriously. The ISS Advisory committee focuses on the International Space Station and international systems.
SpaceX moving forward
Reuters also reported that SpaceX sent them an e-mail stating that its fueling system and launch processes will be re-evaluated pending the results of the accident investigation. The e-mail stated:
As needed, any additional controls will be put in place to ensure crew safety, from the moment the astronauts reach the pad, through fueling, launch, and spaceflight, and until they are brought safely home.
In an interview with Space.com, SpaceX President and COO Gwynne Shotwell said: “The escape system slated for the second version of Dragon would have — should certainly have taken the astronauts to a safe place after an anomaly like this.”
Shotwell also expressed confidence that SpaceX was planning to return to flight by the end of this year.
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.