Space Shuttle Abort Simulation with live audio
From a different video this comment from CopperHampster who sounds like they know what they’re talking about:
In-flight abort modes:
Abort Return to Launch Site (RTLS). If one engine goes down while the boosters are still attached, the shuttle doesn’t have enough energy to make it anywhere useful, so they wait till they can jettison the SRB’s normally, flip the shuttle back right side up and yaw around till it is pointed back at the Cape, and throttle the remaining engines to maximum. The shuttle returns to the Cape, jettisons the tank about 50 miles out, and then lands. If it loses a second while still attached to the boosters, the stack (shuttle/tank/boosters) will exceed it’s attachment loads and most likely break apart. Even if it doesn’t, with only one engine there isn’t enough energy to return to the Cape after SRB seperation. All three engines will cause the stack to break up, the stresses are too high without the SSME’s pushing the shuttle along with the SRBs.
They cannot separate the Solid Rocket Boosters until they are almost burnt out (the normal separation point) because they would shear away in an unpredictable manner and likely pierce the tank.
Second abort mode is Abort: Remote Landing Site. There are several sites pre-selected out of roughly 60 candidates. If the shuttle has too much energy to return to the Cape, it jettisons the SRBs and tank at appropriate times, then lands at one of these other locations. Examples include some major airports in Spain, France, Saudi Arabia, Australia, and India, and even some western US locations.
The third abort mode would be the rarest possible mode; Abort Once Around. This is where the orbiter will complete one circumnavigation returning to land at the Cape. The reason it would be very rare that once AOA becomes available, the final abort mode becomes available 8-10 seconds later. There’s a very tiny window during which they would want/be able to do an AOA.
The final abort mode is ‘Abort To Orbit’ or ATO. When they say ‘Press to ATO’ they mean the shuttle has enough energy to reach an orbit, even if it isn’t as high as the intended one. 5:35 they specifically say ‘They have been instructed to abort to orbit’.
What some may not know is Challenger was almost lost. At 6:44 is when they nearly lost it. The shuttle was too high and fast to return properly without achieving orbit. At 6:44 the same sensor failure which automatically shut down the center engine (Fuel turbine temperature sensors failed) also failed on another engine. The controller overrode the system which would have shut down the second engine, which would have resulted in what is abbreviated LOCV. Loss Of Crew and Vehicle. Challenger would have been unable to reach any orbit but would have been going too fast to re-enter, and would have had no time to turn around, use the remaining engine to shed speed then line up for re-entry.
There was a final abort mode added after the actual Challenger disaster, called a Contingency Abort. Essentially, there were times when RTLS, ARLS, AOA could be implemented but further events (such as a loss of a second engine) could prevent the orbiter from reaching land. The structural attachments between the shuttle, tank, and boosters were strengthened to the point that they should hold even with all 3 main engines down before the boosters are done burning, and they added bail out capabilities because simulations indicated the shuttle was incapable of a survivable water ditching. When NASA says ‘Contingency’ they are referring to either the loss of the vehicle or both the vehicle and crew. You will note if you watch either shuttle disaster that once it sinks in what is going on they start talking Contingency this and that.