BROOMFIELD, Colo. — A last-minute problem with a rocket ignition system halted a Falcon 9 launch of a NASA commercial crew mission Feb. 27, delaying the launch by at least three days.

Launch controllers halted the countdown for the launch of the Crew-6 mission about two and a half minutes before its scheduled 1:45 a.m. Eastern liftoff because of a problem with the ignition system, which uses a chemical combination called triethylaluminum triethylborane, or TEA-TEB. The launch director informed the four-person crew in the Crew Dragon of the issue a few minutes earlier.

In a statement two hours after the scrub, NASA said controllers halted the launch “to investigate an issue preventing data from confirming a full load” of TEA-TEB. SpaceX noted in a tweet that it was a ground system issue.

“I’m proud of the NASA and SpaceX teams’ focus and dedication to keeping Crew-6 safe,” NASA Administrator Bill Nelson said in a statement about the scrub. “Human spaceflight is an inherently risky endeavor and, as always, we will fly when we are ready.”

This was the first scrub for technical issues in a SpaceX human spaceflight launch. Crew-6 is the ninth such mission for SpaceX, after the Demo-2 test flight, five International Space Station crew rotation missions and the Inspiration4 and Ax-1 private astronaut missions.

While a backup launch opportunity exists Feb. 28, NASA said it and SpaceX would not attempt a launch that day because of poor weather conditions. At a pre-launch briefing Feb. 25, Mike McAleenan, launch weather officer for the U.S. Space Force 45th Weather Squadron, said that conditions at the launch site would remain good, but there would be high winds and wave conditions along the ascent corridor up the East Coast.

“The weather is not looking good at all for that particular opportunity,” said Steve Stich, NASA commercial crew program manager, of a Feb. 28 launch at that briefing. NASA previously said it would skip a March 1 launch because of an unfavorable trajectory.

The next three opportunities start March 2, and NASA said it selected 12:34 a.m. Eastern March 2 as the next launch attempt pending resolution of the TEA-TEB issue. Stich said at the briefing it was too early to forecast weather conditions for the early March attempts.

Crew-6 is transporting NASA astronauts Stephen Bowen and Warren Hoburg, who will serve as mission commander and pilot, respectively. Also on Crew-6 are mission specialists Andrey Fedyaev of Roscosmos and Emirati astronaut Sultan Alneyadi. The four will spend about six months on the station.

The Crew-6 scrub is not affecting plans for two other SpaceX Falcon 9 launches scheduled for Feb. 27. One Falcon 9 is slated to lift off from Cape Canaveral Space Force Station in Florida at 1:38 p.m. Eastern, followed less than an hour later by another Falcon 9 launching from Vandenberg Space Force Base in California at 2:31 p.m. Eastern.

Both rockets are carrying Starlink satellites, although the Florida launch is carrying the first “V2 Mini” Starlink satellites: larger spacecraft that SpaceX says have four times the capacity than previous Starlink satellites. The Florida launch carries 21 V2 Mini satellites that will go into orbits authorized by the Federal Communications Commission for its Gen2 system, while the Vandenberg launch will carry 51 first-generation Starlink satellites.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...