United Launch Alliance (ULA) has postponed for at least 24h the launch of a Lockheed Martin Atlas V carrying a large US military communications satellite from NASA's Kennedy Space Center (KSC) in Florida. After the Atlas was fuelled, but less than 30min before scheduled liftoff, technicians noted a problem with the Centaur interstage adaptor, a piece of hardware that connects the Centaur to the common core body first stage. A helium purge valve in the adaptor appears to be at fault.
"The launch of an Atlas V carrying the United States Air Force's Advanced Extremely High Frequency-2 (AEHF-2) payload was scrubbed today due to lack of helium flow from the ground support equipment to the Interstage Adapter compartment on the launch vehicle," says ULA.
Helium is often used to cool fuel pumps and pressurise fuel tanks due to its nonreactive properties.
The launch is rescheduled for 4 May, but may be delayed further depending on the nature of the valve problem.