Columbia’s Many Scrubs

Three Columbia missions account for a large percentage of its total scrubs: STS 61-C in 1986, STS-35 in 1990, and STS-73 in 1995. These three missions had a total of 16 launch delays; almost one fifth of all the delays in the entire shuttle program. Only three non-Columbia missions (out of 85 missions) needed more than four launch attempts to get off the ground. Statistically on the average the shuttle launches on one out of two launch attempts and the remainder are scrubbed due to technical problems or the weather.

The STS 61-C’s six delays included additional time needed to close out the aft compartment, a T-14 second scrub due to a faulty reading in a solid rocket booster’s hydraulic power unit, an error which resulted in the accidental draining of 14,000 pounds of liquid oxygen from the External Tank, bad weather at the emergency landing sites, a sensor failure, and heavy rains. In hindsight it’s clear that some scrubs were caused by heavy pressure to keep launching on schedule with an extremely tight schedule resulting in an overworked launch crew.

STS-35's four delays over six months are at least partially explainable. Columbia had a liquid hydrogen leak in its plumbing, but the leak only showed up when the engineers loaded hydrogen into the External Tank. Engineers were satisfied that if the leak didn’t show up it would be safe to launch. With the high cost associated with loading the tank with propellants and a desire to keep the shuttle flying on schedule and minimize delays the decision was made to change a proposed tanking test into a full-up launch attempt. There was also pressure to try to launch three shuttle flights before the end of the year. But the hydrogen leaks kept Columbia grounded for over six months, and it took five launch attempts before it finally flew. During the many STS-35 delays Columbia got the derisive nickname "The Penguin" - a white and black bird (the colors of the tiles) which doesn't fly.

But STS-73's six delays were just bizarre unrelated problems. They included a leaky fuel valve, hurricane Opal approaching Florida, a problem with the hydraulics, a problem with the master event controller, a crack on a turbopump on a test engine in Mississippi, low clouds and rain, and another rocket already on the schedule to launch from Florida which needed many of the same tracking radars as the shuttle.

As far as anybody has been able to determine, there was no common thread among Columbia's different delays—other than bad luck.

All together, Columbia spent 1,208 days on the launch pad -- 200 more than any other shuttle. That averages out to 43.1 days per mission, 6.5 days more than the average for all other shuttles. Columbia’s excessive pad time was addressed by the CAIB because damage due to exposure to KSC’s salt-air ocean environment might accumulate slowly over time.

Because of its memorable delays, Columbia got the reputation as the shuttle that had the most problems on the ground, but almost always performed flawlessly in space.

All of STS-107’s many delays were schedule slips – not launch attempts. When Columbia rolled out of its Orbiter Processing Facility in November 2002 it was scheduled to launch on January 16, 2003 at 10:39 a.m. and didn’t encounter any additional delays.

The STS-107 mission launched on the first launch attempt at the beginning of its window. Launch director Mike Leinbach said after the launch, "Typically, Columbia's a little difficult to get off the pad and then works outstandingly on orbit. Today it was very easy, we launched on time."

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