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Author
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Topic: Saturn S-IVB Auxiliary Propulsion System Engines
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SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 10-22-2010 08:37 PM
   
Many are unaware that in addition to the well know F-1 and J-2 engines powering the Saturn V, there were two other bi-propellant engines integrated into the launch system, which resided on the S-IVB (third stage). They were housed within two pods installed at 180 degrees from each other and known as the Auxiliary Propulsion System (APS). The APS provided roll control during J-2 engine powered phases of flight, pitch, yaw, and roll (attitude) control during coast periods; maneuvering impulse during undocking and extraction of the Lunar Module, and also propellant settling (ullage). As a final act of glory, the APS was continuously fired until depletion to propel the S-IVB to lunar impact. Each APS pod included four engines; a single Rocketdyne manufactured SE 7-1 (adapted from the Gemini program) 72 pound thrust (310 newton) for ullage and three TRW manufactured TR-204 150 pound thrust (670 newton) chamber assemblies to perform attitude control functions. The TR-204 shown in the following images was the most robustly designed engine flown during the program, having quad redundant propellant solenoids (even the LM Ascent Engine VPA was only dual redundant). Quad redundancy was necessary as the loss of any single TR-204 was sufficient to abort the mission prior to CSM separation from the launch vehicle. The APS system had its own independent propellant and pressurization supply (all of the engines burned hypergolic propellant).  
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Scott Schneeweis, LCDR, USN(Ret);
SPACEAHOLIC.com |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 10-22-2010 08:38 PM
This image shows the relative positions of the TR-204 and SE 7-1 to each other within the APS as well as placement on the S-IVB / Saturn V Third Stage. The 200 series S-IVB (those used on the Saturn IB) excluded the ullage engine as J-2 restart was not required. 
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Jeff
Member Posts: 474
From: Fayetteville, NC, USA
Registered: May 2009
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posted 10-22-2010 10:20 PM
Very nice find Scott...well done. |
ilbasso
Member Posts: 1522
From: Greensboro, NC USA
Registered: Feb 2006
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posted 10-22-2010 11:48 PM
I happen to have a control panel from the Launch Control Center which dealt with the S-IVB APS engines...
(Click here for larger image.) |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 10-23-2010 10:02 AM
That panel really helps tie things together....your artifact includes four toggles identified as "FILL VALVE" (two for each APS pod/module); these switches operated the Helium Fill Valve modules on the APS shown in the following images (Helium was the pressurization gas that fed propellants into each of the engines). 
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