NASA first raised questions about SpaceX’s unusual fueling procedures months before the company’s catastrophic Sept. 1 launchpad explosion. On Monday, a NASA advisory committee issued stronger warnings regarding the way SpaceX intends to fuel rockets that will eventually carry humans.
The commercial spaceflight company plans eventually to ferry astronauts between Earth and the International Space Station on its Crew Dragon spacecraft. Yet, unlike other companies, SpaceX plans to fuel its spacecraft while humans are aboard.
"I’m not aware that in any other U.S. human spaceflight launch, the booster is fueled after the crew is aboard," said John Logsdon, professor emeritus of the Space Policy Institute at George Washington University told The Los Angeles Times. "It’s a deviation from the norm, and that’s bound to raise concerns."
SpaceX employs a different fueling strategy than other companies: It uses chilled liquid oxygen in order to be able to fit more fuel in the tank and lift more weight into orbit, an innovative step that has allowed SpaceX to break new ground in cargo carriage. But because of this special fueling method, its spacecraft must be fueled immediately before launch so that the fuel does not warm up, which means that in the future, astronauts will likely be aboard prior to fueling.
Spaceflight officials have raised concerns about fueling conditions for some time. In December 2015, International Space Station advisory committee Chairman Lt. Gen. Thomas Stafford told NASA in a letter that fueling a rocket with crew aboard flies in the face of decades of launch policies.
Following Monday’s meeting, a SpaceX spokesman said that the company "has designed a reliable fueling and launch process that minimizes the duration and number of personnel exposed to the hazards of launching a rocket."
Despite the advisory group’s criticisms, SpaceX officials say they plan to work with NASA to meet technical and safety standards before gaining the certification necessary to carry humans.
"There will be continued work ahead to show that all of these controls are in place for crewed operations and that the verifications meet NASA requirements," SpaceX said in a statement. "These analyses and controls will be carefully evaluated in light of all data and corrective actions resulting from the anomaly investigation."
Some analysts say that the committee’s concerns could delay the launch of crewed SpaceX spacecraft, which SpaceX had hoped to accomplish in late 2017. Currently, NASA pays Russia about $71 million per seat to use Russian Soyuz spacecraft to carry humans to the International Space Station.
After two months of investigation, the Federal Aviation Administration, NASA, SpaceX, and the US Air Force announced over the weekend that they had targeted the problem that likely caused the September launchpad explosion – a helium tank failure that occurred during fueling procedures.
"SpaceX’s efforts are now focused on two areas – finding the exact root cause, and developing improved helium loading conditions that allow SpaceX to reliably load Falcon 9," SpaceX said in a statement Friday. "With the advanced state of the investigation, we also plan to resume stage testing in Texas in the coming days, while continuing to focus on completion of the investigation."