Apollo abort modes

During the launch of an Apollo spacecraft by the Saturn IB or Saturn V rocket, the flight could be aborted to rescue the crew if the rocket failed catastrophically. Depending on how far the flight had progressed, they would use different procedures or modes. None of these launch abort modes was ever used on any of the fifteen manned Apollo spacecraft flights.

Houston's announcements of the current abort mode and the spacecraft commander's acknowledgements were among the few things said on the radio link during the first minutes of flight.

If the rocket failed during the first phases of the flight, the Emergency Detection System (EDS) would automatically give the command to abort. The reason is that life-threatening situations can develop too fast for humans to discuss and react to. In the later, less violent phases of the ascent, the EDS was turned off and an abort would have to be initiated manually.

Overview

Of the five abort modes, the modes up to two (II) are variations of jettisoning the entire rocket followed by an immediate landing in the sea (splashdown). Mode three (III) and up are variations of jettisoning only the failing rocket stage, using the other stages to continue into Earth orbit. Once there, a backup Earth-orbit mission could be performed so that the flight was not entirely in vain. In all cases, the Command Module (CM) with the astronauts performs a splashdown by:

Details

Apollo's planned-for abort modes were, in chronological order:

Apollo Launch Escape System diagram

The EDS is enabled for the pad abort (beginning 5 minutes prior to launch) through abort mode IB phases. Beginning in mode IC, the EDS is switched off and aborts must be commanded manually.

See also

References

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