The in-flight crew escape system is provided for use only when the orbiter would be in controlled gliding flight and unable to reach a runway. This condition would normally lead to ditching. The crew escape system provides the flight crew with an alternative to water ditching or to landing on terrain other than a landing site. The probability of the flight crew surviving a ditching is very slim.

The hardware changes required to the orbiters enable the flight crew to equalize the pressurized crew compartment with the outside pressure via the depressurization valve opened by pyrotechnics in the crew compartment aft bulkhead that would be manually activated by a flight crew member in the middeck of the crew compartment; pyrotechnically jettison the crew ingress/egress side hatch manually in the middeck of the crew compartment; and bail out from the middeck through the ingress/egress side hatch opening after manually deploying the escape pole through, outside and down from the side hatch opening. One by one, each flight crew member attaches a lanyard hook assembly, which surrounds the deployed escape pole, to his or her parachute harness and egresses through the side hatch opening. Attached to the escape pole, the crew member slides down the pole and off the end. The escape pole provides each crew member with a trajectory that takes the crew member below the orbiter's left wing.

Changes were also made in the software of the orbiter's general-purpose computers. The software changes were required for the primary avionics software system and the backup flight system for transatlantic-landing and glide-return-to-launch-site abort modes. The changes provide the orbiter with an automatic-mode input by flight crew members through keyboards at the commander's and/or pilot's panel C3, which provides the orbiter with an automatic stable flight for crew bailout. This software change, which is required to allow the flight crew commander's departure, automatically controls the orbiter's velocity and angle of attack to the desired bailout conditions.

The crew would make the escape decision at an altitude of approximately 60,000 feet and would immediately make an input to the flight control system software autopilot mode.

When the orbiter descends to an altitude of approximately 30,000 feet, its airspeed must be decreased to approximately 200 knots (230 mph). At approximately 25,000 feet, a crew member in the middeck (referred to as the jump master and seated in the forward left seat in the middeck) raises a cover on the left side of the crew compartment middeck at floor level and pulls the T-handle, which activates the pyrotechnics for the depressurization valve at the crew compartment X o 576 aft bulkhead. This equalizes the crew compartment cabin and outside pressure before the side hatch is jettisoned.

At approximately 25,000 feet, the software for the automatic autopilot mode changes the orbiter's angle of attack to approximately 15 degrees. This angle of attack must remain nearly constant for approximately three minutes until the orbiter reaches an altitude of approximately 2,000 feet.

At approximately 25,000 feet, the jump master jettisons the side hatch by pulling the hatch jettison T-handle next to the depressurization T-handle. When the T-handle is pulled, pyrotechnics separate the hatch assembly by severing the side hatch hinge, and three pyrotechnic thrusters jettison the tunnel/hatch from the orbiter at a velocity of approximately 50 feet per second.

The jump master pulls the pip pin on the escape pole and pulls the ratchet handle down, which permits the two telescoping sections of the escape pole to be deployed through the hatch opening by spring tension.

A magazine assembly located near the side hatch contains a lanyard assembly for each flight crew member. Each lanyard assembly consists of a hook attached to a Kevlar strap that surrounds the escape pole. Five roller bearings on each strap surround the pole and permit the lanyard to roll freely down the pole. Each flight crew member positions himself or herself at the hatch opening and attaches himself or herself to the escape pole via the lanyard hook assembly and jumps out the hatch opening.

Each lanyard assembly incorporates an energy absorber rated at 1,000 pounds. The Kevlar strap consists of two sections of permanent Nomex thread stitching and a section of breakaway Kevlar thread stitching. When the crew member exits the side hatch on the escape pole, the breakaway Kevlar thread stitching can break away, providing the crew member with an energy absorber. The crew member slides down the escape pole and off the end into a free-fall. The escape pole extends downward 9.8 feet from the side hatch and provides the crew member with a trajectory that will carry him or her beneath the orbiter's left wing.

It would take approximately 90 seconds for a maximum crew of eight to bail out. After the first crew member bails out from the middeck, the remaining crew members follow at approximately 12-second intervals until all are out by approximately 10,000 feet altitude.

A handhold was added in the middeck next to the side hatch to permit the crew members to position themselves through the side hatch opening for bailout.

The escape pole is constructed of aluminum and steel. The arched housing for the pole is 126.75 inches long and is attached to the middeck ceiling above the airlock hatch and at the 2 o'clock position at the side hatch for deployment during launch and entry. The escape pole telescopes from the middeck housing through the side hatch in two sections. The primary extension is 73 inches long, and the end extension is 32 inches long. The diameter of the housing is 3.5 inches. The two telescoping sections are slightly smaller in diameter. The escape pole weighs approximately 241 pounds-248 pounds with attachments.

On orbit, the escape pole's primary stowage position requires unpinning the escape pole at the starboard and port attachments, rotating the pole so it is flat against the middeck ceiling and strapping it to the ceiling. An alternate on-orbit stowage approach also requires unpinning the escape pole at the starboard and port attachments, rotating it so it is flat against the middeck ceiling and strapping it to the ceiling.

The side hatch water coolant lines for side hatch thermal conditioning were modified to accommodate the installation of the side hatch pyrotechnic separation system.

The flight crew members' seats were also modified to accommodate the seat/crew altitude protection system suit for each crew member.

The pyrotechnically operated crew compartment depressurization valve consists of two flapper valves with debris screens on the crew compartment side and payload bay side that open to depressurize the crew compartment and close when the pressure equalizes.

It is noted that the hatch jettison features could be used in a landing emergency.

The crew member's altitude protection suit includes an emergency oxygen system, pilot and drogue parachutes that are operated automatically and have manual backup, a main parachute that is operated automatically and has manual backup, a seawater activation release system, flotation devices, a life raft and survival equipment. The crew altitude protection suit and its associated equipment weigh approximately 70 pounds.

The side hatch jettison thruster contractor is OEA, Denver, Colo. The pyrotechnics contractor for the hatch tunnel, hinge and the energy transfer system lines is Explosive Technology, Fairfield, Calif. The escape pole is government-furnished equipment that is supplied by NASA's Johnson Space Center, Houston, Texas, as is the crew altitude protection suit.