NASA posted a statement on one of its websites Friday that it has provisionally approved
SpaceX’s “load-and-go” procedure for commercial crew flights of the SpaceX
Crew Dragon. That refers to fueling the rocket just before launch, after the crew is aboard. The idea has been sharply criticized by many experts, but apparently the company has won over at least some of those critics.
Historically, rockets are fueled when no one is near the launch pad in case something goes awry, such as an explosion. That is exactly what happened in September 2016 when a SpaceX Falcon 9 rocket exploded on the launch pad while it was being fueled as part of a pre-launch test two days before the scheduled liftoff of a commercial communications satellite. The rocket and the AMOS-6 satellite, which was already mated to the launch vehicle, were destroyed and the launch pad severely damaged. No one was near the launch pad or onboard the vehicle so there were no injuries.
SpaceX founder and CEO Elon Musk insisted at the time that if a crew had been aboard in a Crew Dragon capsule, the Dragon’s pad abort system would have pulled them away to safety. SpaceX successfully tested that abort system in May 2015.
SpaceX’s proposal to use the load-and-go procedure when sending astronauts to the International Space Station (ISS) already had raised concerns. Eight months earlier, in December 2015, Gen. Tom Stafford (Ret.) wrote a letter to the head of NASA’s human spaceflight program, Bill Gerstenmaier, on behalf of the NASA International Space Station Advisory Committee that he chairs. “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 country 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.” Stafford is a renowned former astronaut who flew four space missions in the Gemini and Apollo programs.
NASA’s Aerospace Safety Advisory Panel (ASAP) has expressed similar worries in the past. Its January 2018 annual report again urged NASA and Space X to fully assess all the hazards involved and weigh the risks against the benefits.
In recent months, however, some of those concerns apparently have been ameliorated. At its May 17, 2018 quarterly meeting, ASAP expressed a most positive view, concluding load-and-go is a “viable option” as long as “verifiable controls are identified and implemented for all the credible hazards causes which could potentially result in an emergency situation or worse…”
NASA’s own assessment now is even more favorable. The head of the commercial crew program, Kathy Lueders, said in Friday’s statement that the agency agreed with SpaceX to use load-and-go because it has “the least risk.”
“To make this decision, our teams conducted an extensive review of the SpaceX ground operations, launch vehicle design, escape systems and operational history,” said Kathy Lueders, manager of NASA’s Commercial Crew Program. “Safety for our personnel was the driver for this analysis, and the team’s assessment was that this plan presents the least risk.”There are some caveats. “Additional verification and demonstration activities, which include five crew loading demonstrations of the Falcon 9 Block 5, will be critical to final certification of this plan.”
The launch day plan outlined in the statement is as follows:
- Falcon 9 composite overwrap pressure vessels (COPVs) loaded with helium and verified to be in a stable configuration prior to astronaut crew arrival at the pad
- Astronauts board spacecraft 2 hours before launch
- Ground crews depart
- Launch escape systems activated approximately 38 minutes before launch
- SpaceX begins loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch
The countdown can be stopped automatically “up the last moment before launch.” If there is an emergency, the launch abort system “will allow the astronauts to evacuate safely.”