October 7, 1999
Web posted at: 5:16 p.m. EDT (1625 GMT)

By Miles O'Brien
CNN Correspondent

ATLANTA (CNN) - The NASA launch cabal engaged in a multi-variable, multi-layered discussion on Thursday - hoping to achieve some sort of manifest destiny for their fleet of shuttles.

And while they have succeeded in adding some clarity to their future - they have greatly complicated our space coverage plans.

Lest I bury the lead, during a 3-hour "telecon," launch managers in Houston and at the Cape decided to set a launch date for the third Hubble repair mission. Discovery is scheduled to leave Launch Pad 39-B at 4:32 a.m. EDT, on December 2.

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The next day, December 3, The Mars Polar Lander should arrive on the surface of the Red Planet. The first images should be back on earth a few days later.

You see the problem? Two big space stories ongoing simultaneously. It will be an interesting week.

The wiring inspections and repairs are all but complete on Discovery. There are enough splices, (large and small) to necessitate a "full-up" test of Discovery's electrical system. You wouldn't want to find out about a loose connection or a crossed wire on ascent -- or in low earth orbit. Everything electrical will have to be spooled up and checked out. This will take some time -- but not so much time that it would cause an additional delay.

The faulty wiring that led to the lengthy inspections

Meanwhile, there is the problem with the valve in Discovery's Orbital Maneuvering System (OMS) pod. There are two OMS engines on every shuttle. Their nozzles sit above the orbiters three main engines -- protruding from the humps on either side of the tail. Among other things, OMS engines help shuttles reach, circularize and ultimately leave earth orbit.

Each OMS engine can produce 6,000 pounds of thrust, working the same way as their smaller siblings -- the network of maneuvering rockets called the Reaction Control System. Both are hypergolic systems - meaning their fuel and oxidizer spontaneously ignite on contact (no spark plugs required).

So when technicians discovered a leak in one of the valves designed to control the flow of the oxidizer (nitrogen tetroxide) into the thrust chamber at the top of the nozzle, they realized they had a potentially big problem. After using an electronic sniffer to make sure the leak was isolated in one place, they cannibalized a valve from sister ship Columbia.

Hubble Space Telescope

They will be watching the replaced valve closely for 72 hours after it is installed. If it leaks again, they may have to replace the entire OMS pod (also cannibalized from Columbia). Even if that happens, launch managers feel they have enough time to install the OMS pod before Discovery rolls out of the Vehicle Assembly Building at the end of October.

All of this will be finalized at a Launch Readiness Review on November 10. So, assuming things go as planned, during the week of December 6, space fans will receive a holiday treat from NASA: a dramatic series of four spacewalks during East Coast overnight hours - followed during the day by some equally dramatic images from the surface of another world.

As for Endeavour and her mission to create a radar map of the earth: with wiring inspections 90 percent complete on the orbiter NASA lovingly calls OV-105, she is scheduled to launch on January 13.

Atlantis will fly her mission to the International Space Station no earlier than February 10. Wiring inspections -- and work on a leaking ammonia boiler -- lie ahead. So pencil that one in. Matter of fact, I would stick with pencils in general when trying to keep track of all this.