The United States' space shuttle Discovery will be equipped with a 10-foot-long aluminum pole to enable crew members to bail out during a landing emergency, the National Aeronautics and Space Administration announced Thursday.
The decision to install the escape device came after 66 tests by Navy parachutists who used it to exit a C-141 transport plane outfitted with a hatch similar to the shuttle exit. NASA said the telescoping pole, to be located in the orbiter's mid-deck, will be installed in time for Discovery's four-day flight, now scheduled for launch Aug. 4.
Concern over the absence of an emergency escape system in the space vehicle was heightened by the January, 1986, Challenger tragedy, which claimed the lives of seven crew members.
A presidential commission investigating the accident urged the space agency to address the emergency bail-out problem, and NASA spent months evaluating designs of an emergency escape system.
But long before settling on the simple aluminum pole, the space agency opted not to undertake the costly, time-consuming redesign that would have been required to enable astronauts to eject from the shuttle during launch or during a high-altitude mishap such as the one that struck Challenger.
In opting to install the aluminum pole, engineers also decided against a "tractor" rocket system that would have been designed to jerk crew members out the side hatch of a stricken vehicle during its descent.
'Simpler to Operate'
"The telescoping pole was selected as it has shown to be safer, simpler to operate, lighter weight and easier to support than the tractor rocket system, while meeting all escape system performance requirements," said Arnold D. Aldrich, shuttle program official.
In the first test flights of the shuttle, when only two crewmen were aboard, the orbiter was equipped with ejection seats similar to those used in fighter planes, but they were removed once additional crew members, riding in the mid-deck below the pilots' compartment, were added.
In case of an abort on launch, plans called for the shuttle to ditch in the ocean, with crew members scrambling into the sea after landing.
Studies in the wake of the Challenger disaster showed that astronauts probably would not survive an ocean ditching. A simple parachute bail-out from the side hatch was discounted because of the likelihood that astronauts would be hit by the wing or by the orbital maneuvering engines that bulge out at the rear of the vehicle.
Sliding Clear of Shuttle
The pole design adopted Thursday would enable crew members to slide clear of the shuttle structure before jumping free to descend by parachute.
There is still no way for crew members to escape from the vehicle in the event of a catastrophic accident such as the failure of the Challenger's solid booster and the explosion of its external fuel tank.
With the new system, the plan calls for the crew to remain aboard the orbiter until it descends to an altitude of about 22,000 feet.
Then, the hatch would be blown away by explosive bolts and the pole extended.
NASA officials said eight crew members could leave the shuttle in a two-minute period as it descends and that it would be possible to escape from an altitude as low as 1,000 feet.
Partial Pressure Suits
In recent months, officials have also added partial pressure suits for crew members to use in launching or landing emergencies and an escape slide, similar to that on commercial airliners, to speed emergency evacuation after landing. The slide pole was favored over the tractor rocket system because of its simplicity and because it weighs about 70 pounds less than a rocket escape system.
During launch and landing, the pole will be positioned behind the closed hatch where it can be deployed within seconds. Once the shuttle is in orbit, it will be stowed on the ceiling so that it will not interfere with crew activities.
SHUTTLE ESCAPE SYSTEM
1. Once the shuttle has descended to an altitude of about 22,000 ft., the cabin would depressurize and the side hatch would be blown off.
2. The telescoping pole, which is made of lightweight aluminum and steel and weighs 241 pounds would then be extended through the open hatch.
3. Each astronaut would attach a line with a hook on it to his or her parachute harness, assume the tuck position and slide down the pole to safety.