Every facility needs an emergency escape plan. Schools have fire escape plans and they practice fire drills. Space Shuttle astronauts practice for an emergency escape from the Orbiter. The space term for this maneuver is called an emergency egress. Should an emergency situation arise, astronauts have several options for quickly exiting the crew compartment area, depending on how far the launch has progressed.
Image to left: Astronauts practice emergency evacuation from the Orbiter. Credit: NASA
When the Orbiter is on the ground awaiting liftoff, astronauts have access to the Emergency Exit System. It's positioned 59 meters (195 feet) above the ground, at the same level as the Orbiter Access Arm, and includes seven baskets suspended from seven slidewires that extend to a landing zone 366 meters (1,200 feet) to the west. After the astronauts climb into the baskets, a braking system, catch net and drag chain slow, and then stop the baskets as they slide down the wire. The angle of the slidewire causes the baskets to move the astronauts as far away from the Space Shuttle as possible. The braking system stops the baskets from hitting the ground too hard.
Once launched, the spacecraft can make an emergency return to Earth, with the astronauts staying inside and exiting just as with a normal landing. If there were a problem inside the Orbiter, however, the astronauts wouldn't want to wait to touch down. They'd want to get out much faster than that, so they'd use the Inflight Crew Escape System.
At an altitude of about 9,150 meters (30,000 feet), astronauts would pull a handle that turns on the depressurization valve in the crew compartment bulkhead. This equalizes the cabin pressure and outside air before the side hatch is released.
At 7,620 meters (25,000 feet), the hatch is jettisoned and two telescoping sections of the aluminum and steel escape pole deploy through the hatch. Each crew member hooks a Kevlar® strap onto the pole, jumps out the hatch opening, slides down the 3.1-meter (10-foot) pole and goes into a freefall until the parachute opens to ease the journey to the ground. It takes approximately 90 seconds for a crew of eight to bail out of the Space Shuttle, and by that time, the vehicle is at 3,050 meters (10,000 feet) altitude.
If the Space Shuttle has made a safe landing, but the astronauts need to exit the vehicle immediately, they can use the Emergency Egress Slide. This operates much like the emergency slide on commercial airplanes, inflating with a self-contained supply of air. The slide allows a safe exit to the ground within one minute of the hatch opening. As a backup, the Secondary Emergency Egress allows the astronauts to lower themselves to the ground over the side of the Space Shuttle, once they've escaped through the left overhead window of the Orbiter. This window is equipped with pyrotechnic firing circuits to quickly remove the windowpane.
Image to left: Training includes learning to maneuver in the water. Credit: NASA
The crew wears protective launch suits during launch to help in the event of an emergency egress. The suit includes an emergency oxygen system; pilot, drogue and main parachutes that operate automatically and have manual backup; a seawater activation release system; flotation devices; a life raft and survival equipment. This multipurpose suit weighs approximately 32 kilograms (70 pounds).
Because emergency egresses can involve so many potential risks, astronauts train extensively before their mission so that they'll be prepared for any eventuality. They slide down the slidewire baskets, practice using the Inflight Crew Escape System and learn to maneuver in the water in case their emergency exit takes place over the ocean.