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CAPE CANAVERAL—A SpaceX Falcon 9 rocket poised to deliver the first satellite of the U.S. Air Force’s next-generation GPS III network remained on the ground Dec. 18 after the onboard flight computer detected a first-stage liquid oxygen sensor approaching an out-of-bounds temperature reading, triggering an automated abort.
Liftoff had been planned for 9:34 a.m. EST from Cape Canaveral Air Force Station Space Launch Complex 40. In attendance to watch the launch was Vice President Mike Pence, who used the occasion to announce the Trump administration’s plan to establish a new U.S. Space Command to oversee all of the military’s space activities.
But about 7 min. before liftoff, the launch director halted the countdown. “It looks like the Falcon 9 has hit an abort condition,” SpaceX launch commentator Tom Praderio said.
With the 26-min. launch window, which opened at 9:11 a.m. EST, about to close, SpaceX scrubbed the flight and reset the launch for 9:07 a.m. EST Dec. 19.
SpaceX later posted on Twitter that the scrub was due to “an out-of-family reading on first-stage sensors.” The company did not say if the temperature readings were too high or too low.
SpaceX uses highly densified liquid oxygen, chilled to a temperature of about minus 340F, which is pumped into the first stage beginning 35 min. before liftoff and into the second stage 16 min. before liftoff.
The GPS III launch is the first for SpaceX awarded under the Air Force’s Phase 1A procurement initiative for competitively sourced National Security Space launch services. Since then, SpaceX has won a total of five GPS launch contracts, with a combined value of about $470 million.
SpaceX and United Launch Alliance are the only companies certified to compete for high-value national security space launch services.