Spaceflight Now: Breaking News

Debby no longer a threat, storm policy under review
Station gyro problem resolved

Posted: August 24, 2000

  Shuttle launch pad
Shuttle Atlantis arrives at its seaside launch pad earlier this month. Photo: NASA/KSC
With Hurricane Debby no longer threatening the Kennedy Space Center, engineers at pad 39B are pressing ahead with work to ready shuttle Atlantis for blastoff Sept. 8 on a space station outfitting mission.

But NASA managers are still debating the agency's hurricane protection policy and the wisdom of having two shuttle's on the spaceport's two launch pads at the same time during the height of hurricane season.

Current plans call for launching the shuttle Discovery Oct. 5 to carry a set of stabilizing gyroscopes to the space station. Discovery had been scheduled for roll out to pad 39A around Aug. 28, but agency managers last week put those plans on hold pending a reassessment.

The delay has no immediate impact on Discovery's planned launch date because engineers have about two weeks of contingency time built into the processing schedule.

At issue is how long it might take to roll two shuttles back to the protection of NASA's cavernous Vehicle Assembly Building should a major storm threaten Florida's east coast.

While NASA has two shuttle transporters -- the powerful tracked crawlers that carry the shuttle and its mobile firing stand from the VAB to the pad and back -- the contractor that operates them only has enough manpower to run one at a time.

It typically takes six or more hours for a shuttle stack to be moved from the pad to the VAB or vice versa and many more hours to ready a shuttle for such a journey.

  Shuttle move
Space shuttle Discovery is moved into the Vehicle Assembly Building for attachment to its external fuel tank and solid rocket boosters. Photo: NASA/KSC
Given manpower constraints and how fast storms can change course and character, NASA managers could be forced to make a roll back decision well before a hurricane's course could be accurately predicted.

As a result, James Halsell, a veteran shuttle commander who now oversees shuttle processing at the Kennedy Space Center, is re-assessing how NASA should operate and process space shuttles during hurricane season.

Discovery was hauled from its processing hangar to the Vehicle Assembly Building earlier today for attachment to a set of solid-fuel boosters and an external fuel tank.

If all goes well, the shuttle will be ready for the trip to pad 39A by Aug. 30. But the trip could be delayed indefinitely depending on what Halsell and his team conclude. As it now stands, Discovery's processing flow includes 10 days of contingency time plus the Labor Day holiday weekend.

In the meantime, engineers have resolved a potential problem with Discovery's payload that otherwise could have posed a threat to the Oct. 5 launch date.

Boeing technicians remove the cover from a Control Moment Gyroscope (CMG) in the Space Station Processing Facility in July 1998. Photo: NASA/KSC
The Z1 truss scheduled for launch aboard Discovery houses four large control moment gyroscopes that will be used to stabilize and re-orient the space station. The gyros will not actually be used until early next year, after arrival of the U.S. laboratory module, Destiny.

During testing of a backup gyroscope, the epoxy holding a speed sensor in place debonded at a temperature of around 50 below zero Fahrenheit. The Z1 gyros will never experience such low temperatures once they are in operation, but they could get cold enough for problems during the five months they will be dormant, awaiting the lab's arrival.

Engineers have developed a two-fold approach to solving the problem. First, the thermostats that regulate heaters in the gyro system will be reset to make sure the temperature never falls too low. In addition, laptop computer software can be used by space station crews to manually control the thermostats if needed.