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Apollo abort modes: Difference between revisions





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{{Short description|Plans for mission abort during an Apollo spacecraft launch}}
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.▼
{{More citations needed|date=August 2021}}
 
▲During'''Apollo abort modes''' were procedures by which the nominal launch of an [[Apollo spacecraft]], byeither the [[Saturn IB]] or [[Saturn V]] rocket, could be terminated. The abort of the flight couldallowed befor '''aborted''' tothe rescueof the crew if the rocket failed catastrophically. Depending on how far into the flight thehad crew wereprogressed, they would use different proceduresprocedureor'''modes''' would be used. NoneIn the history of the [[Apollo program|Apollo Program]], none of the abort modes were ever hadused toon beany usedof the fifteen crewed Apollo spacecraft flights.
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.▼
 
▲Houston's announcements of the current abort mode and the spacecraft commander's acknowledgements belongwere toamong 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.
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==Overview==
 
Of the five abort modes, the modes up to twothree (IIIII) are variations of jettisoning the entire rocket followed by an immediate landing in the sea ''([[Splashdown (spacecraft landing)|splashdown]])''. Mode threefour (IIIIV) and upthe Saturn V-specific modes 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 [[Apollo command and service module#Command module (CM)|Command Module]] (CM) with the astronauts performs a splashdown by:
* dumpingDumping the [[hypergolic]] fuel overboard since the toxic substance would be an unnecessary risk to recovery personnel.
* ifIf high enough, deploying high-speed parachutes ''([[drogue parachute]])''.
* jettisoningJettisoning the drogues and deploying the main parachutes.
* splashingSplashing down in the sea and waiting for recovery team to arrive.
 
==Details Pad abort ==
*'''Pad abort[[Image:'''Launch escape system diagram.jpg|thumb|Apollo Launch Escape System diagram]]If the rocket failed in the last five minutes before launch, the CM and the [[Apollo_spacecraftApollo (spacecraft)#Launch_Escape_System_.28LES.29Launch escape system (LES)|launch escape system]] (LES, see figure) would separate from the remainder of the rocket below with the LES propelling itself and the CM beneath it upward and eastward to the sea using a small solid-fuelledfueled enginemotor (the pitchlaunch controlescape motor) at the top of the tower on the launch escape system. The launch escape tower would then be jettisoned in anticipation of the parachute deployment and the CM would splash down. (Preparation for a pad abort is seen in Apollo video footage: five minutes before launch, the umbilical arm connecting to the CM retracts and swings clear of the rocket. It does so because the swing arm must be out of the way in case the EDS decides to abort.)▼
Apollo's planned-for abort modes were, in chronological order:
 
Two tests of the LES were conducted:
[[Image:Launch escape system diagram.jpg|thumb|Apollo Launch Escape System diagram]]
 
**[[Pad Abort Test-21 (Apollo)|Pad Abort Test-21]]: LESLaunch padEscape System (LES) abort test offrom nearlaunch Block-I CMpad with Apollo [[Boilerplate B(spaceflight)|Boilerplate]] BP-23A6.▼
▲*'''Pad abort:''' If the rocket failed in the last five minutes before launch, the CM and the [[Apollo_spacecraft#Launch_Escape_System_.28LES.29|launch escape system]] (LES, see figure) would separate from the remainder of the rocket below with the LES propelling itself and the CM beneath it upward and eastward to the sea using a small solid-fuelled engine (the pitch control motor) at the top of the tower on the launch escape system. The launch escape tower would then be jettisoned in anticipation of the parachute deployment and the CM would splash down. (Preparation for a pad abort is seen in Apollo video footage: five minutes before launch, the umbilical arm connecting to the CM retracts and swings clear of the rocket. It does so because the swing arm must be out of the way in case the EDS decides to abort.)
**[[Pad Abort Test-12 (Apollo)|Pad Abort Test-12]]: LaunchLES Escape System (LES)pad abort test fromof launchnear padBlock-I CM with Apollo [[Boilerplate (spaceflight)|Boilerplate]] BPB-623A.
▲**[[Pad Abort Test-2 (Apollo)|Pad Abort Test-2]]: LES pad abort test of near Block-I CM with Apollo Boilerplate B-23A.
 
== Mode I ==
*'''ModeAn I:''' Abortabort using the LES, this abort mode could be conducted from launch until the LES jettisonwas jettisoned 30 seconds after [[S-II]]the ignition of the second stage.
**'''Mode IA (one alpha):''' During the first 42 seconds of flight [up to {{convert|3000|m}},] 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. Fourteen seconds into the abort, the LES tower is jettisoned, leading to splashdown.▼
**'''Mode IB (one bravo):''' From {{convert|3000|m}} to 30.5&nbsp;km <!--That's 100,000 ft in the original-->(100,000 feet) (117 seconds after launch), the rocket is tilted eastwards far enough that firing the pitch control motor is unnecessary. After the LES main motor moved the CM away from the rocket, the tower would deploy canards (small wings at the tip). They would force the CM-LES combination to fly with the CM bottom forward (''blunt-end forward'' or BEF attitude), necessary because the parachutes stowed at the CM top can only be deployed in a [[downwind]] direction.▼
**'''Mode IC (one charlie):''' From 30.5&nbsp;km (100,000 feet, or about 19 miles) 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 IA (one alpha) ===
*'''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.▼
▲**'''ModeDuring IAthe (onefirst alpha):'''42 Duringseconds of flight for the firstSaturn 42V or 60 seconds of the flight &#91;upfor tothe {{convert|3000|m}}Saturn IB,&#93; the rocket is still relatively upright and an abort is much like a pad abort, lasting up to {{convert|3000|m}}. TheDuring mainthe andabort, the main pitch control motors move the CM out of the flight path of the possibly exploding rocket. FourteenAt 14 seconds into the abort, the LES tower is jettisoned, leadingin the lead upto the splashdown.
 
=== Mode IB (one bravo) ===
*'''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, has 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 IB (one bravo):''' From {{convert|3000|m}} to 30.5&nbsp; km <!--That's 100,000 ft in the original-->(100,000 feet) (117 seconds after launchft), the rocket is tilted eastwards far enough that firing the pitch control motor is unnecessary. After the LES main motor movedmoves the CM away from the rocket, the tower would deploy [[Canard (aeronautics)|canards]] (small wings at the tip). They would force the CM-LES combination to flypitch over with the CM bottom forward (''blunt-end forward'' or BEF attitude.), This was necessary because the parachutes stowed at the CM top canwere only designed to be deployed in a [[downwind]] direction.{{refn|group=note|name=parachutes|As it turned out, however, the parachutes would still successfully deploy even with the CM traveling nose-forward; this was discovered during the [[A-003]] abort test, when the canards deployed, but failed to flip the spacecraft blunt-end-forward due to an extremely high roll rate resulting from a booster malfunction.}}
 
=== Mode IC (one charlie) ===
*'''S-IVB to orbit:''' As in Mode III, the failing S-II would be jettisoned early, but Earth orbit insertion is now possible by the S-IVB alone. Other than not using the SM engine, this is identical to a Mode III abort. This abort mode ends with normal S-II jettison.▼
▲**'''Mode IC (one charlie):''' From 30.5&nbsp; km (100,000 feet, or about 19 milesft) until the LES is jettisoned, turningpitching the CM-LES combination aroundover 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, at an altitude of about 90 km (295,000 ft or 55 miles).
 
== Mode II ==
*'''Mode IV:''' Abort during S-IVB burn. Should the S-IVB fail, the [[Service Module]] engine can now place the CSM in Earth orbit to perform an Earth orbit mission.▼
▲*'''Mode II:''' Abort early during S-II burn. With the LES gonejettisoned, 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 Service Module (SM) and splash down.
 
== Mode III ==
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.▼
A Mode III type abort would be used when a Mode II type would risk the spacecraft coming down over land, or landing in the cold water of the [[Atlantic Ocean|North Atlantic]]. The CSM would separate from the rocket in the same manner as a Mode II abort, but would additionally use the SPS engine to make either a posigrade burn (''Mode IIIA'') or retrograde burn (''Mode IIIB'') to land in a specific area on the eastern side of the Atlantic. Mode III was only available as a primary abort mode for 10–15 seconds during a Saturn IB launch, and was only used as a backup abort mode for Saturn V launches, in case of an abort requiring the immediate landing of the spacecraft.
 
== SeeMode alsoIV ==
▲*'''Mode IV:''' Abortwas an abort mode that occurred during the [[S-IVB]] burn. Should the S-IVB fail, the [[Service Module]] engine can now place the CSM ininto Earth orbit to perform an Earth -orbit mission.
 
== Mode V ==
A Mode V abort was only planned for use during the [[Apollo-Soyuz Test Project]] launch. In the event of an early S-IVB shutdown, the CSM RCS thrusters would be used to insert the entire stack (including the docking adapter) into orbit. The time window for a Mode V abort was only 1.5 seconds before nominal S-IVB cutoff.
 
== Saturn V specific abort modes ==
During orbital abort phases (S-IVB to COI, S-IVB to orbit and Mode IV), modes II and III were available as backup modes in the event of further problems.
 
▲The EDS iswas enabled for the pad abort (beginning 5 minutes prior to launch) through abort mode IB phases. Beginning in mode IC, the EDS iswas switched off and aborts mustwould have had to be commanded manually.
 
=== S-IVB to COI ===
▲*'''Mode("Saturn IIIIV-B (NASA''',s alsodesignation knownfor asthe Saturn V'''Contingencys Orbitthird Insertionstage (COIburn)''' orTo '''S-IVBContingency toOrbit COI:'''Insertion") In case of ana failure of the [[S-II]] failuresecond stage, itthe stage would simply be jettisoned, early. For the first time in the flight,and the rocket is now high and fast enough that the third stage ([[S-IVB]]) enginethird stage, followed by the [[Apollo Command/Service Module|Service Module]] (SM) engine, has enough powerpropellant to place the spacecraft in Earth orbit. The spent S-IVBThere would not havebe enough fuelpropellant to perform [[trans -lunar injection]], so only an earth Earth-orbit mission would be performed.
 
=== S-IVB to Orbit ===
▲*'''S-IVB to orbit:''' As in Mode III, theThe failing S-II would again be jettisoned early, but Earth orbit insertion is now possible by the S-IVB alone. Other than not using the SM engine, this is identical to aan ModeS-IVB IIIto abort. ThisCOI abort mode ends with normal S-II jettison.
 
==See also==
* [[it:Apollo pre-launch abort modes]]▼
* [[Space Shuttle abort modes]]
* [[Orion abort modes]]
* [[Soyuz abort modes]]
 
==Notes==
{{Reflist|group=note}}
 
==References==
*[https://history.nasa.gov/astp/documents/Astp-recoveryreq.pdf ASTP Recovery Requirements - NASA History Office]
*[http://www.hq.nasa.gov/office/pao/History/ap15fj/01launch_to_earth_orbit.htm Apollo 15 Flight Journal]
* [httphttps://klabsntrs.orgnasa.gov/history/apollo_experience_reports/tn-d7083_apollo_launch_escape_propulsionsearch.pdfjsp?R=19730010175 NASA TN D-7083: Launch Escape Propulsion Subsystem]<!--http://klabs.org/history/apollo_experience_reports/tn-d7083_apollo_launch_escape_propulsion.pdf-->
*[httphttps://klabsntrs.orgnasa.gov/history/apollo_experience_reports/tn-d6847_apollo_abort_planningsearch.pdfjsp?R=19720017278 NASA TN D-6847: Apollo Experience Report—Abort Planning]<!--http://klabs.org/history/apollo_experience_reports/tn-d6847_apollo_abort_planning.pdf-->
*[https://apollo11.spacelog.org/glossary/ Apollo 11 Glossary - spacelog.org] {{Webarchive|url=https://web.archive.org/web/20190513181851/http://apollo11.spacelog.org/glossary/ |date=2019-05-13 }}
 
[[Category:Apollo program]]
[[Category:Abort modes]]
 
▲[[it:Apollo abort modes]]

Retrieved from "https://en.wikipedia.org/wiki/Apollo_abort_modes"
  




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