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*'''Mode I'''—Abort using the LES, from launch until LES jettison 30 seconds after [[S-II]] ignition |
*'''Mode I'''—Abort using the LES, from launch until LES jettison 30 seconds after [[S-II]] ignition |
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**'''Mode IA''' (one alpha)—During the first 42 seconds of flight (up to 3000 metres), the rocket is still relatively upright and an abort is much like a pad abort. The main and pitch control motors move the CM out of the flight path of the possibly exploding rocket. 14 seconds into the abort, the LES tower is jettisoned, leading to splashdown. |
**'''Mode IA''' (one alpha)—During the first 42 seconds of flight (up to 3000 metres), the rocket is still relatively upright and an abort is much like a pad abort. The main and pitch control motors move the CM out of the flight path of the possibly exploding rocket. 14 seconds into the abort, the LES tower is jettisoned, leading to splashdown. |
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**'''Mode IB''' (one bravo)—From 3000 metres to 30.5 km <!--That's 100,000 ft in the original-->(117 seconds after launch), the rocket is tilted eastwards far enough that firing the pitch control motor is unnecessary. After the LES main motor has moved the CM away from the rocket, the tower would deploy canards (small wings at the tip). They force the CM-LES combination to fly with the CM bottom forward (''blunt-end forward'' or BEF |
**'''Mode IB''' (one bravo)—From 3000 metres to 30.5 km <!--That's 100,000 ft in the original-->(117 seconds after launch), the rocket is tilted eastwards far enough that firing the pitch control motor is unnecessary. After the LES main motor has moved the CM away from the rocket, the tower would deploy canards (small wings at the tip). They force the CM-LES combination to fly with the CM bottom forward (''blunt-end forward'' or BEF attitude). That is necessary because the parachutes stowed at the CM top can only be deployed in [[downwind]] direction. |
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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 be 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. |
*'''Mode II'''—Abort early during S-II burn. With the LES gone, the [[Apollo Command/Service Module|Command/Service Module]] (CSM) would be 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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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. |
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. |
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== See also == |
== See also == |
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 for that. 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.