Engineers are troubleshooting two leaks, one helium and one nitrogen, in the plumbing of the shuttle Discovery's right-side orbital maneuvering system rocket pod.

Credit: NASA

Discovery's countdown to launch on a space station resupply mission is scheduled to begin at 3 p.m. today. Liftoff on the shuttle's 39th and final mission is targeted for 4:40:27 p.m. EDT (2040:27 GMT) Monday. The current launch window extends through Nov. 7.

It is not yet known what impact, if any, the two leaks might have on the countdown or launch. An engineering report said both are "under review" and engineers are meeting this morning to discuss repair options.

"This is not a huge deal, but we just have no cushion in the schedule," said a NASA official.

Two interim problem reports, or IPRs, were written up overnight, one because of a gaseous nitrogen leak at a quick disconnect fitting and another in the helium pressurization system that is used to push propellants into the OMS pod engines.

The first problem showed up during a gaseous nitrogen fill valve leak check and the second issue was discovered after the helium system was pressurized for launch. An inspection revealed an internal O-ring in a ground-system helium coupling was partially stuck inside its shuttle counterpart. That fitting apparently will have to be replaced.

The right-side OMS pod was re-installed in July after work to fix a helium isolation valve that had problems during Discovery's most recent mission in April. A leak in a fuel crossfeed line associated with the right OMS pod was repaired last weekend when two internal seals were replaced.

It is not yet known whether the helium and nitrogen leaks could be related to last weekend's repair work or the rocket pod's removal and reinstallation.

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