Author Topic: Apollo aborts? - Mode II, Saturn-I Block-II, Little Joe-II with LIVE SM abort  (Read 2489 times)

Offline georgegassaway

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I have an Apollo abort question which is somewhat two parts, towards an ultimate goal.

According to this wiki abut Apollo abort modes, Mode II.

https://en.wikipedia.org/wiki/Apollo_abort_modes

Quote
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.

OK, so…. with LES jettisoned already, the CSM would separate. I knew that already, but never heard any specifics.  What I am wondering is the sequence of events, what would fire when? I do not mean a second by second timeline.  The most immediate and fastest would be to fire explosive bolts on the LM shroud and immediately fire the SM main engine, “fire in the hole” style.  But that would produce a lot of pressure inside the shroud panels, which would need some time to open up otherwise, possibly damaging the engine that way.

But then if the CSM only used the RCS thrusters, and the LM shroud had not opened up the panels significantly, there could have been some side contact of the SM engine bell with a panel if it did not come exactly straight out.

Of course a big part of that would be how much of an immediate problem might there be, by that point of the flight.  By then it’s almost, if not already in “Space”, so with the engines shut down the vehicle could just be floating along, even if in a slow pitch rate that would be bad aerodynamically at 30,000 feet but no big deal at 300,000 feet.  Time to carefully separate.

Now, there is actually a different reason why I ask this.  It relates to the Little Joe-II program which tested out the Apollo LES abort system. 

There was a proposal, never flown, to fly with a “Live” Service Module, and do a high altitude abort using the SM engine instead of using the LES.  Now, the Little Joe-II never flew with room for a real SM engine bell. So, it would need  a different cylindrical adapter long enough to hold the engine.  This mock-up photo is not related to the Little Joe-II, but it is the best example I have for what would have been needed as an extension to be added to a Little Joe-II if one had launched with a live SM.



And this drawing from a Block-II Saturn-I, shows a similar cylindrical adapter:   



However, none of the Block-II Saturn-I’s flew a live SM, so the SM’s never separated.  So it is unclear to me how, if a live SM ever was going to be flown on a Block-II Saturn-I, the SM was going to separate cleanly from the S-IV stage without risk of damage if all four RCS thrusters did to fire exactly equally, or what.  I will say I clarified with an expert that the convex dish shapes  in the instrument ring were not blowout panels, they were guidance related.  So that sort of kills the idea of a “fire in the hole” firing of the SM engine, much like Titan-II staging.

One of the things I wonder, if they had flown a live SM, is whether the adapter would have been split into four 90 degree panels as the LM shroud was. So the panels for a cylindrical adapter would have been jettisoned much the same way, allowing for a safer and cleaner separation.

The ultimate reason for asking this, is that I’m working up a model to represent that proposal for a Little Joe-II to have carried a live SM for an abort.  I’m trying to decide on some realistic detailing to do for it.

- George Gassaway



Compare above with this:


« Last Edit: 03/22/2016 10:25 PM by georgegassaway »

Offline Jim

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.  But that would produce a lot of pressure inside the shroud panels, which would need some time to open up otherwise, possibly damaging the engine that way.


The SLA panels open up quickly much like payload fairing jettison and the SME could fire
« Last Edit: 03/22/2016 10:48 PM by Jim »

Offline indy91

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Well, first of all I think the Wiki page is wrong. A Mode II wouldn't involve the SPS engine. Mode II is just getting away from the booster with the RCS and then landing somewhere in the Atlantic. The SPS is used for Mode III (landing in the Atlantic Discrete Recovery Area (ADRA), south of the Canary Islands) or Mode IV (SPS to Orbit).  Mode III and S-IVB to COI capability are also not the same thing.

Anyway, the sequence during an abort is:

-Initiate Abort by Translational Hand Controller into counterclockwise detent.
-Booster Engine Cutoff (BECO). The automatic sequence allows 3.0 seconds for this phase to make sure the thrust residuals of the booster engine don't make it crash into the separating CSM.
-CSM is separated from the LV by severing and jettisoning the SLA panels, CSM/LV and LM/GSE umbilicals.
-After additional 0.8 seconds automatic direct ullage is activated, so RCS thrusting forward, until the THC is returned to neutral. The CDR would stabilize the spacecraft, if necessary, and use the RCS for additional 20 seconds to get away from the S-II or S-IVB.
-Depending on the abort mode the SPS would be ignited at 2 minutes after the abort.

Sources and more info in the Apollo Operations Handbook, Volume 1, Section 2.9 (Sequential Systems) and Volume II, Section 5.1 (Abort Procedures).

You might be specifically interested in figure 2.9-25 (Adapter Separation System) of the first source. Link for convenience: http://history.nasa.gov/afj/aoh/aoh-v1-2-09-seqsys.pdf
« Last Edit: 03/22/2016 11:41 PM by indy91 »

Offline catdlr

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thought I would include this video for this thread for reference:

Little Joe II SC 002 lanch

Published on Feb 23, 2016
Little Joe II A-004 Apollo SC-002 launch. Two angles. Apollo Launch Escape System test from 1966.



Tony De La Rosa

Offline georgegassaway

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Thanks for the information.

I know I went a sort of long way to get to my actual objective, which was how would a CSM do an abort from an extended cylindrical fairing such as a Little Joe-II would have needed to allow the engine bell vertical length (For a live SM abort test).  If the Block-II Saturn-I’s had ever done it, then the answer would be out there. But since the Block II Saturn-I’s never carried a live SM, then there may not have been the proper cylindrical adapter built for that task.

Lacking any better info, I end up wondering if a cylindrical adapter therefore right have been split into 4 panels, and then such an abort could go as described:

Quote
-CSM is separated from the LV by severing and jettisoning the SLA panels, CSM/LV and LM/GSE umbilicals.
-After additional 0.8 seconds automatic direct ullage is activated, so RCS thrusting forward, until the THC is returned to neutral. The CDR would stabilize the spacecraft, if necessary, and use the RCS for additional 20 seconds to get away from the S-II or S-IVB.
-Depending on the abort mode the SPS would be ignited at 2 minutes after the abort.

Certainly in any case, it is now clear that there would have been no SPS firing until way later (2 minutes). Lacking any other info, I think for the model I will make up the cylindrical adapter with 4 seams, as though it would have separated the four much as the LM adapter panels did, rather than the CSM needing to gingerly accelerate forward without the SPS bell nozzle hitting a fixed adapter.

BTW - thanks for posting the link to the Little Joe-II A-004 / SC-002 launch, I knew it was there.  I had asked Tom Beach awhile back if he still had that footage on video tape, and if so, if he might post it on YouTube, which he did.

There is a lot of Little Joe-II information on my website, though I have not updated it for awhile (need to add links to Tom’s video and the great new Estes 1/45 scale kit):

http://georgesrockets.com/GRP/Scale/DATA/LJoeMain.htm

- George Gassaway

« Last Edit: 03/23/2016 05:07 AM by georgegassaway »

Online Ronpur50

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OK, that is a fantastic model!! And it an Estes?

Offline catdlr

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Bump for additional historic film...

HACL film 01007 General Dynamics Little Joe II assembly transport firing Apollo Program


sdasmarchives
Published on Nov 17, 2017


Film from the Atlas-Centaur Heritage Film Collection which was donated to the San Diego Air and Space Museum by Lockheed Martin and United Launch Alliance.  The Collection contains 3,000 reels of 16-millimeter film.

https://www.youtube.com/watch?v=HUexBxh0xLs?t=001

Tony De La Rosa

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