Here is a shuttle abort simulation done around STS-26. The audio is the actual abort; the events are sync'd to video of a successful launch. This simulated abort included a cascade of failures which resulted in inability to RTLS, with ocean ditching the only option:
https://www.youtube.com/watch?v=HGyiLv6mPbg
The simulated failures include:
- AC bus phase 3 failure
- Right engine failure
- MDM (multiplexer/demultiplexer) failure, this is the link between the main computers and secondary computers
- IMU (Inertial Measurement Unit) accelerometer failure. IMUs are the primary on-board navigation method
- Left engine failure
- Center engine failure
- loss of voice communications
Callout terminology used:
"Abort RTLS" -- Return to Launch Site abort, where vehicle pitches around and heads back to Kennedy
"MDM FF2 down at the MDM" -- multiplexer/demultiplexer failure which cuts off communications between computers and other subsystems.
"I/O reset picking up" - Emergency keyboard command, attempt to restore flight avionics after a critical failure
"IMU #1 accelerometer problem" -- Shuttle navigates by three redundant IMUs (Inertial Measurement Units). One failed due to bad accelerometer.
"Deselect/reselect IMU #1" -- try to get IMU back on line by rebooting it.
"Dump in progress" -- emergency firing of the orbital maneuvering engines to lighten the vehicle.
"We're in 601" -- computers are running program 601, designed for RTLS abort
"two engine out blue" -- a procedural call indicating they've lost two engines early in the ascent
"need the pushbuttons" -- automatic engine shutdown upon propellant depletion is unreliable, must manually shut down engines
"any chance of getting this one back?" -- Is shuttle too far downrange for a return to launch, or must it ditch in the ocean
"have you got a predicted IP?" -- Can the ocean landing impact point be calculated?
"602" -- flight computers are running program 602 (RTLS abort subroutine for reentry). RTLS subroutine is used even for a bailout over the ocean.
"need to reduce alpha" -- during reentry the nose is pitched too high, if uncorrected would over-G the vehicle
"He's in the pullout" -- Orbiter is in atmospheric reentry, must pull up, but stay within thermal/G limits.
"Select the lower left antenna" -- Orbiter has several flush-mounted antennas on the upper fuselage which communicate with TDRSS satellites. Request they manually select one to restore comm.