When a space shuttle shuts down in the last seconds before liftoff, the launch team has its most important work to do.
- By Gregory Freiherr
- Air & Space magazine, January 1996
(Page 3 of 5)
"Then we have a decision point," Pierce says. "Are we still hot?" If so, members of the launch team will continue to turn off the shuttle's various systems. Throughout the process, the NTD is getting updates on temperatures from environmental control engineers. If the temperature doesn't drop to an acceptable range, he will order an emergency power-down and get the crew off the shuttle. Without electrical power on the shuttle, the launch crew no longer sees data from its systems, a situation that would require an emergency egress for the flight crew. "They open the hatch, jump out, run across the arm, and do the slide wire thing," Pierce says.
"The slide wire thing" is the astronauts' escape system: seven flat-bottom baskets that slide down 1,200-foot wires to safety. Each basket is made of steel and heat-resistant fiber surrounded by netting and can carry up to three persons. They slide down wires into catch nets, which drag chains to stop them near a bunker designed to withstand the force of a shuttle explosion.
In a real emergency, the astronauts would take a brisk walk--no more than 50 feet--across the shuttle access arm and fixed service structure to the baskets. Their trip would be complicated by a steady stream of water being sprayed to protect them from flames or heat. To ensure that no one gets lost, crew members are trained to grab a mitt full of each other's spacesuits. A crew of five, for example, splits into groups of two and three. They would follow a "yellow brick road"--gold and black chevrons painted on the metal grate floor--aiming them toward the baskets.
Riding the slide wires has its own risks--ones serious enough that during the abort simulations NASA fills the baskets with weights and dummies rather than people. But the agency has man-rated the system. George Hoggard, a training officer on the pad rescue team, is one of only three people who have ever ridden in a slide-wire basket at the launch pad. The ride began 195 feet above the ground and ended 21 seconds later. The basket reached 53 mph before striking the net.
The only part of the ride Hoggard found unnerving came near the end, when the basket slapped the restraining net with a bang. "It was like a shotgun going off," Hoggard says. "But nothing hurt, so I figured I was still okay." The net and drag chain broke free from their poles, as they were designed to do, and the chain dragged through sand to bring the basket to a gradual stop.
The bunker, located about 30 feet from the end of the slide wire, is stocked with water, oxygen, and medical supplies. But if one of the crew is hurt and needs more than first aid, an M113 armored personnel carrier, parked next to the bunker, can be used to get the astronaut to any of several points for evacuation by helicopter.
Several weeks before scheduled lift-off, the crew members take turns driving the M113, an acquired skill. It takes only a minor miscalculation to make a big mistake, as an astronaut discovered last spring when she took a corner too sharply and drove the M113 into a pond behind one of the launch pads.
The exercise isn't designed to turn astronauts into tank drivers; it's part of building a team, says Captain David M. Walker, four-time space veteran and commander of the five-member STS-69 crew, which was launched on September 7. "It gives us a chance to interact with the fire and rescue people, who are going to be the folks who save our bacon if something goes really wrong," he says.