Enlarge / The Falcon 9 first stage approaches Just Read the Instructions in the Atlantic Ocean after successfully launching CRS-6 to the International Space Station, April 14, 2015. (credit: SpaceX)

NASA advisers are continuing to express concerns about a SpaceX fueling process known as “load and go,” in which chilled fuel is loaded onto the rocket just 30 minutes before a scheduled launch. This week the agency’s Aerospace Safety Advisory Panel strongly encouraged NASA top management to “scrutinize” this issue as part of an annual report on safety concerns in US spaceflight, which could have significant implications for the commercial crew program.

SpaceX has gained notoriety during the last 13 months for landing the first stage of its Falcon 9 rocket on land, and at sea aboard an autonomous drone ship. One critical component to this success has been the use of a new fueling process that chills liquid oxygen to below -200 degrees Celsius, allowing more of this denser oxidizer to fit within the rocket’s fuel tanks. The additional fuel has provided SpaceX the margin needed to fly its boosters back to Earth after they delivered their payloads into space, especially those bound for geostationary orbit.

Because this super-chilled oxygen can warm quickly after it is loaded onto the rocket, SpaceX has adopted the “load and go” strategy. After implementing the new fueling process in December, 2015, SpaceX had been working toward using the same fueling methods when beginning crew flights to the International Space Station next year.