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**'''Mode IC (one charlie):''' From 30.5 km until the LES is jettisoned, turning the CM-LES combination around into the CM-forward position would still be necessary, but in the now thin air the canards are useless. Instead, the small engines of the CM's reaction control system ([[Reaction control system|RCS]]) would do the job. During One-Charlie, the first staging occurs, that is the jettisoning of the spent first stage ([[S-IC]]) and ignition of the second stage ([[S-II]]). One-Charlie ceases about 30 seconds after the staging when the LES is jettisoned. |
**'''Mode IC (one charlie):''' From 30.5 km until the LES is jettisoned, turning the CM-LES combination around into the CM-forward position would still be necessary, but in the now thin air the canards are useless. Instead, the small engines of the CM's reaction control system ([[Reaction control system|RCS]]) would do the job. During One-Charlie, the first staging occurs, that is the jettisoning of the spent first stage ([[S-IC]]) and ignition of the second stage ([[S-II]]). One-Charlie ceases about 30 seconds after the staging when the LES is jettisoned. |
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*'''Mode II:''' Abort early during S-II burn. With the LES gone, the [[Apollo Command/Service Module|Command/Service Module]] (CSM) would |
*'''Mode II:''' Abort early during S-II burn. With the LES gone, the [[Apollo Command/Service Module|Command/Service Module]] (CSM) would separate as a whole from the rocket and use its large engine and RCS engines to move clear of the rocket and align itself. The CM would then separate from the SM and splash down. |
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*'''Mode III''', also known as '''Contingency Orbit Insertion (COI)''' or '''S-IVB to COI:''' In case of an S-II failure, it would simply be jettisoned early. For the first time in the flight, the rocket is now high and fast enough that the third stage ([[S-IVB]]) engine, followed by the [[Apollo Command/Service Module|Service Module]] (SM) engine, have enough power to place the spacecraft in Earth orbit. The spent S-IVB would not have fuel to perform [[trans lunar injection]], so only an earth orbit mission would be performed. |
*'''Mode III''', also known as '''Contingency Orbit Insertion (COI)''' or '''S-IVB to COI:''' In case of an S-II failure, it would simply be jettisoned early. For the first time in the flight, the rocket is now high and fast enough that the third stage ([[S-IVB]]) engine, followed by the [[Apollo Command/Service Module|Service Module]] (SM) engine, have enough power to place the spacecraft in Earth orbit. The spent S-IVB would not have fuel to perform [[trans lunar injection]], so only an earth orbit mission would be performed. |
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During the launch of an Apollo spacecraft by the Saturn V rocket, the flight could be aborted to rescue the crew if the rocket failed catastrophically. Depending on how far into the flight the crew were, they would use different procedures or modes. None of the abort modes ever had to be used.
Houston's announcements of the current abort mode and the spacecraft commander's acknowledgements belong to the few things being 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.
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:
Apollo's planned-for abort modes were, in chronological order:
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.
