Endeavour’s last launch was delayed by NASA on Friday because of a problem with a heating system on one of the hydraulic power generators, leaving thousands of tourists disappointed. The heaters, NASA explained, were vital to keeping the fuel from freezing in the line and causing a rupture in the cold temperatures of space.

NASA has announced that they will attempt the launch again on May 8th. Their engineers hope to have the heating system problem fixed by then. Workers have already replaced an electronics box in the shuttle’s rear engine compartment. The box routes power to the heaters and many other systems.

NASA is now working to replace the switch box and test all the systems again. According to NASA, it will take several days, and the earliest possible attempt to launch Endeavour will be May 8. In the mean time, the crew of the Endeavor have returned to Johnson Space Center in Houston.

Endeavour is the youngest of all spaceship fleet and the replacement ship for the Challenger, the shuttle lost in an explosion shortly after its launch in 1986. It is the second ship of the three surviving shuttles to be retired. Discovery was the first, having been retired in March. Atlantis, Endeavour’s sister ship, will be retired after its final launch, which is scheduled for June 28.