User:Autumn Wind/sandbox

Anyone reading this

This is from Apollo abort modes. I have made a summary of the topics to be discussed, but I need to read through the technical document again. A few times. IMO The technical info is very relevant but too much for the WP article. Also not all of the modes are clearly labelled; mentions of abort modes appear out of nowhere having not been defined. Another source could probably help.

update: I found another source and am sorting through it. Given that I am learning this as I research, I will want to make sure that I'm getting it right before publishing.

Apollo abort modes

The Apollo program had abort profiles established for all phases of the missions. Depending on the situation, some actions were to be executed immediately, even automatically, while others were up to the discretion of the ground and/or flight crew. The abort situations are categorized into several phases: Launch, Trans-Lunar Injection (TLI), Trans-Lunar Coast (TLC) Lunar-Orbit Insertion (LOI), Lunar Orbit, Lunar Descent, Lunar Ascent, Trans-Earth Injection and Trans-Earth Coast.

Launch Phase

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:

• Dumping the hypergolic fuel overboard since the toxic substance would be an unnecessary risk to recovery personnel.
• If high enough, deploying high-speed parachutes (drogue parachute).
• Jettisoning the drogues and deploying the main parachutes.
• Splashing down in the sea and waiting for recovery team to arrive.

Details

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

Apollo Launch Escape System diagram

• Pad abort: If the rocket failed in the last five minutes before launch, the CM and the 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-fueled motor (the launch escape 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-1: Launch Escape System (LES) abort test from launch pad with Apollo Boilerplate BP-6.
  • Pad Abort Test-2: LES pad abort test of near Block-I CM with Apollo Boilerplate B-23A.
• Mode I: Abort using the LES, from launch until LES jettison 30 seconds after S-II ignition.
  • Mode IA (one alpha): During the first 42 seconds of flight – up to 3,000 metres (9,800 ft) – 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 3,000 metres (9,800 ft) to 30.5 km (100,000 ft) (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 km (100,000 ft, 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 (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: Abort early during S-II burn. With the LES gone, the 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.
• 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 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.
• 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 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.

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.

Translunar injection (TLI)

Having achieved a nominal Earth parking orbit, and given a go for TLI, the Saturn IVB would begin its burn to the moon. The only pre-planned abort at this stage is a retrograde burn to re-entry. However, given that most possible anomalies would have ample time to plan and choose an alternate mission profile, it was generally not considered there would ever be a need to do this. In fact, later missions favored completing the TLI attempt over an immediate abort to earth. Part of the TLI would likely occur without ground contact, and that could be re-established quicker if the burn is at least more complete. Also there is more time to plan an ideal landing solution if necessary.

In the unlikely event that a critical failure occurred, an abort to earth landing was possible (again, maintaining orbit was preferred.) Guidelines were established such that a ten minute delay would be enacted, in which time the flight crew would re-orient the spacecraft, and prepare to burn for de-orbit. The delay would also possibly allow re-establishing communication with ground, better tracking ability, and choice of landing site. Attitude was set at an optimal 5° for the retrograde burn with the SPS engine, and was consistent for the entire range of possible TLI burn completion.

001:30:38 Fullerton: Roger. I have a TLI plus 90 and lift-off plus 8 abort PADs, when you're ready.

   [Throughout the mission, large lists of numbers, called PADs, will be read up to the crew which give them the information necessary to carry out a particular maneuver. PAD stands for Pre-Advisory Data. Some of these "block data" are for planned maneuvers such as the TLI (Translunar Injection) or LOI (Lunar Orbit Insertion) burns. Other PADs, such as the "TLI plus 90" and "Lift-off plus 8" mentioned here are the first of 27 abort options which will be read up to the crew at scheduled times throughout the early and middle portions of the mission. Note that the TLI+90 PAD has nothing to do with TLI itself but would occur 90 minutes after a successful TLI burn in the event of an abort. However, mission planners have decided that at no time beyond Earth orbit will the crew be without a get-us-home PAD. Then, any time they might lose communication with Earth, they will have the information to hand to get themselves back manually.]

http://www.hq.nasa.gov/office/pao/History/ap15fj/02earth_orbit_tli.htm

Translunar coast

Once in TLC, the CSM was separated and docked with the LM. The S-IVB was expended at this point, but any aborts at this stage could potentially make use of either the LM or CSM engines and guidance systems depending on the situation. While the actual method of execution would essentially be determined real-time, there were 3 basic profiles: direct-return, circumlunar, and post-pericynthion aborts.

TLI plus 90

Direct-return abort

The SPS is used to re-establish an earth trajectory. While the LM DPS could be used for this technically, guidelines were established that should not be done this way in preference for circumlunar abort if possible. The LM may or may not be jettisonned.

Circumlunar abort

The SPS or LM DPS is used to obtain an earth intercept trajectory. The LM may or may not be jettisonned. This abort option was only be used within the lunar sphere of influence. The ship would continuing coasting to pericynthion before an abort maneuver. Notably, this was the action taken with Apollo 13, as the ground crew decided it was a safer route (Although a course correction was required.) Some missions would not necessarily even have needed more than minor course corrections if they were still in a free-return trajectory.

Post-pericynthion abort

The SPS or LM DPS is used to obtain an earth intercept trajectory. This mode would be used if the other two were not possible for some reason.

Lunar orbit insertion and orbit

LOI occurred on the "far" side of the moon out of contact with the ground crew. A failure of the CSM engine during LOI would leave the LM DPS engines as the only recourse for earth return. The LM APS engines however were not part of the abort procedures due to control problems that would arise. Specifics would depend on actual trajectory after the LOI attempt. They possible lunar orbits were classified as follows:

• Class I: escape trajectory
• Class II: unstable, or impacting ellipse
• Class III: stable or non-impacting ellipse

Class III orbits that are not nominal may result in an alternate mission, rather than an abort, depending on the situation

Each class corresponds to a mode. more or less. who wrote this crap?

Lunar descent and ascent

Primary concern for aborts once the LM has separated up until the ascent stage docks is to establish the rendezvous. This can either be accomplished by actions from the CM or LM depending on the situation.

Transearth injection and coast

At this point, the return to earth is the actual mission profile. Any abort procedure after incomplete burn is to restart the engine and try again. During TEC, an abort would essentially only be a procedure that altered the time or landing location of the craft.