EDITOR’S NOTE: Updated at 10 p.m. EDT Tuesday (0200 GMT Wednesday) with decision to roll back to VIF.
Officials scrubbed the planned launch of a Boeing-built crew capsule Tuesday to examine a potential technical issue in the spacecraft’s propulsion system, delaying the start of a critical unpiloted test flight to prove the ship is ready to ferry astronauts to the International Space Station.
Boeing announced the scrub around three hours before the mission’s scheduled launch time of 1:20 p.m. EDT (1720 GMT) Tuesday. The Starliner crew capsule’s Atlas 5 launch was already loaded with cryogenic propellants when officials announced the delay.
“During pre-launch preparations for the uncrewed test flight of the CST-100 Starliner spacecraft, Boeing engineers monitoring the health and status of the vehicle detected unexpected valve position indications in the propulsion system,” the company said in a statement. “The issue was initially detected during check outs following yesterday’s electrical storms in the region of Kennedy Space Center.”
Teams initially hoped to reschedule the launch for Wednesday, but managers decided Tuesday evening to roll the 172-foot-tall (52.4-meter) Atlas 5 rocket and Starliner spacecraft back to the Vertical Integration Facility, the hangar where United Launch Alliance stacked the vehicle over the past few weeks.
The propulsion system valves in question are inside the Starliner’s service module, which has an array of rocket thrusters designed to propel the spacecraft away from its launcher during an in-flight emergency. Other thrusters on the service module are used for in-orbit maneuvers and spacecraft pointing control.
Boeing said engineers cycled the service module propulsion system valves Tuesday afternoon. Sources said the data continued to indicate the valves were not behaving as expected, but Boeing said it ruled out a number of potential causes for the problem, including software.
“Additional time is needed to complete the assessment and, as a result, NASA and Boeing are not proceeding with tomorrow’s launch opportunity,” Boeing said Tuesday evening.
‘We’re going to let the data lead our work,” said John Vollmer, vice president and program manager of Boeing’s commercial crew program. “Our team has worked diligently to ensure the safety and success of this mission, and we will not launch until our vehicle is performing nominally and our teams are confident it is ready to fly.”
Ground crews planned to power down the spacecraft late Tuesday, then roll the rocket and capsule back to the VIF on Wednesday atop the Atlas 5’s mobile launch platform. Once the vehicle is in the hangar, engineers will perform further inspections and testing on the Starliner service module, which is not physically accessible while on the launch pad.
Boeing and NASA, which manages the commercial crew program, did not announce a new target launch date Tuesday evening. The next launch opportunity after Wednesday is Saturday, but completing the Starliner inspections and testing — and resolving any potential problem on the service module — in time for a weekend launch is unlikely, sources said.
Once the mission is cleared for takeoff, the Starliner spacecraft will dock with the space station, where the lab’s crew will open hatches leading to the crew capsule. The station crew members will unload several hundred pounds of cargo and inspect the capsule’s crew cabin.
A test dummy named “Rosie the Rocketeer” will occupy one of the capsule’s seats during Orbital Flight Test-2, Boeing’s name for the demonstration mission.
The Starliner crew capsule is launching on a do-over of a problem-plagued demo mission in 2019 that failed to reach the space station. Boeing and NASA blamed the botched mission on software programming errors, and managers say extra testing has resolved the software concerns ahead of this mission.
Boeing developed the CST-100 Starliner spacecraft under contract to NASA, which has similar agreements with SpaceX for that company’s Crew Dragon program. SpaceX’s capsule began flying astronauts to the space station last year, and Boeing is now more than a year behind.
Both companies have contracts with NASA for at least six commercial crew missions to the space stations. SpaceX has already launched two of its operational crew rotation flights.
Before Boeing can move on to its first crewed test flight, NASA managers want to ensure the contractor has resolved the software woes that cut short the 2019 test flight. The Starliner test flight will also prove out the spacecraft’s rendezvous and docking systems, which were unused on the 2019 mission.
The OFT-2 mission was supposed to launch last Friday, but officials delayed the mission to allow time to resolve and recover from a problem at the space station Thursday that caused the complex to drift off its proper orientation.
Russia’s Nauka science module began inadvertently firing thrusters a few hours after docking at the space station. The complex temporarily lost attitude control before Nauka’s thrusters stopped firing and other rocket jets on the station could maneuver the nearly one million-pound outpost back to the correct attitude.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.