posted 10-25-2009 02:39 AM               

1. application of red paint band around the fuel (propellant) valve/injector... this would have been applied by McDonnell in conjunction with integration of the engine into the flight vehicle RCS module (note that the stock SE-8 on the left of the first photo was excessed directly from Rocketdyne and lacks this band (a similar green band would have been applied on the oxidizer injector by McDonnell);

2. Oxidizer feed line, valve and injector and portion of mounting boss have been cut (likely the result of post-flight extrication from the flight vehicle RCS system)

3. Ablation external of the nozzle (engine firing only results in internal nozzle ablation); the external charring is consistent with reentry heating of the nozzle.

posted 10-25-2009 06:16 AM               

Some differences I note: The ID tag is turned 90 degrees, which may be significant. It differs from any photos I have seen of flown thrusters (Gemini 7, 8, 9, 12).

Note the proliferation of stamps and other markings on the housing of the thruster in my collection.

The part number on its tag starts with "SCD" (Specification Control Drawing).

Can you show a better image of the ID tag?

Here are closer views of the Gemini 7 RCS thruster and tag from the NASA photo on my site:

Note a stamped assembly date "3Q64" and a stamped number just below the tag "D3948." These types of numbers appear similarly on the Gemini 9 flown thruster in my collection.

posted 10-25-2009 09:36 AM               

Stamped date is two quarters preceding yours - possibly indicative of this SE-6 seeing flight on an earlier capsule; maybe the process changed a bit with respect to application of the decal. The partial drawing number is different then yours (starts as 52-5... and ends with "9" with a portion of the tag damaged) but I don't think the difference excludes its use as there would have been improvements/changes in the design as the program progressed.

Would be nice to get our hands on images of RCS systems from say GT-3 or its design specifications.

Over the years, I have seen several SE-6's that have not been flown but were test fired and none of them exhibited ablation around the exterior of the nozzle. How does one account for external ablation absent flight history?

posted 10-25-2009 11:47 AM               

Gemini 7 thruster (ref NASA photo):
Part: 20891[?]
Serial: 4003948
McDonnell: SCD52-527[??]
Assy: 3Q64

Gemini 9 thruster (HSS collection)
Part: 208915-61
Serial: 4070772
McDonnell: SCD52-52700-275
Assy: 2Q65

Mystery thruster:
Part: 209532
Serial: NA820148
McDonnell: 52-520[??]-9
Assy: 1Q64

The Gemini 7 and 9 numbers harmonize rather well. The mystery thruster has many commonalities, but a few nagging differences. I agree the time frame is right. And the thruster face has certainly seen some heat. As you said, we need more early flight numbers.

We know these thrusters saw a lot of early development and testing. Maybe this is an early flight thruster that was subjected to additional ground testing. But I don't know if any testing was ever done that could simulate the external heat effects expected for reentry.

Another item of data is that the 52-520XX series of McDonnell drawing numbers relates to the RCS and OAMS systems (equipment installation, for example).

posted 10-25-2009 02:38 PM               

quote:

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Originally posted by space1:
We know these thrusters saw a lot of early development and testing. Maybe this is an early flight thruster that was subjected to additional ground testing. But I don't know if any testing was ever done that could simulate the external heat effects expected for reentry.

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posted 10-25-2009 06:04 PM               

The Gemini 7 photo does show a dark red material that appears to have seeped from within the can and even past the seal. I'm guessing it is some kind of resin from the fabrication of the thruster. I am also guessing that this photo was taken to document this apparent failure of the thruster. The artifact in my collection has a small amount of similar material beginning to seep out. Otherwise its can is clean.

posted 10-27-2009 12:01 PM               

I think this is a good exercise, first to better understand the visible characteristics/signature of flown ablative engines as a number of SE-6's (and CM SE-8's) were de-installed from returned Gemini capsules for post flight analysis and may still be circulating in the public (all flown SE-7 variants were jettisoned with OAMS packages in space). It's also important to solicit an understanding of the type of testing Rocketdyne was capable of conducting (and its attendant limitations) from the folks who actually worked these programs prior to loosing them.

Your guess is probably correct...that is probably an engine that has flown and re entered. We did not have a way of simulating re entry at Rocketdyne.

posted 12-14-2009 11:40 AM               

In a recent auction I acquired some Gemini reports. One of them is a McDonnell report entitled "SAR - Spacecraft 3 Acceptance Review - Phase I," November 30, 1964. In the Propulsion section, a table lists the Thrust Chamber Assemblies (TCA's) by part number and serial number. Amazingly, the table lists:

RCS "B" Ring
TCA #4
MAC P/N: 52-52700-217
S/N: 820148
Guarantee Life or Cycles: 136 sec.
Accumulated Time or Cycles: 3.0 sec.

posted 02-15-2013 06:55 PM               

Based on the charring on the interior of the nozzle I concluded that the engine has been fired, probably during ground testing.

From the serial number can anybody confirm for me whether the SE-6 was flown on GT-6? Thank you.

SE-6 rocket engine made from steel, other metals, and ablative material at the nozzle end, 10 inches long and 4 inches wide. A black and silver identification tag reads in part: "PART NAME: Thrust Chamber Assy(Assembly), MFD BY ROCKETDYNE FOR MCDONNELL. PART NO. 208130-71, MOD. NO. SE-6, SER 4060122.... MCDONNELL PART NO. SCD52-52700-239." The tag includes two inspection stamps. With a 5½ x 4 inch red Rocketdyne nozzle cover which reads: "RK 395-3001, INSTALL 1/6 UNIT DESICCANT."

A set of eight of these bi-propellant engines were located in the equipment section aft of the crew compartment which was part of the Orbit Attitude and Maneuver System (OAMS). Yaw, pitch, and roll spacecraft torques were obtained by firing these engines in pairs. Sixteen additional SE-6 engines made up the Reentry Control System (RCS) in the nose of the Gemini spacecraft. SE-6 engines produced 25 pounds of thrust. Each engine assembly consisted of a fuel and oxidizer valves with injector systems, a combustion chamber, and expansion nozzle. The fuel value system on this engine was removed for testing.

Signed by Wally Schirra and Tom Stafford near the identification tag. Each has added "GT-6." The SE-6 engines on the Gemini 6 spacecraft assisted Schirra and Stafford in performing the world's first rendezvous with Gemini 7 in December 1965.

posted 03-14-2020 11:21 PM               

quote:

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Originally posted by SpaceAholic:
Here's an example of an SE-8 in my collection

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Nozzle extension scarfing angle suggests either a yaw or roll engine variant.

Based on a number of different artifact attributes, have determined this engine was de-installed from a Command Module RCS following flight (most likely CSM-111).

posted 06-17-2022 11:07 AM               

Design changes between the early and late models included the transition from a silicon carbide to ceramic throat (the silicon carbide throat was legacy to the Gemini SE-6 RCS and SE-7 OAMS engines which served as the initial model for SE-8 design; silicon carbide during developmental testing of the Apollo RCS engines was determined to be susceptible to cracking during the higher dynamic reentry loads/shock associated with the Apollo vs Gemini missions); another obvious difference between the early SE-8s and flight version was a redesign of the solenoid housing located at the top of the engine.

Additionally the engine includes a rare intact scarfed nozzle extension. The integration of the 12 SE-8 RCS engines on each conically shaped Apollo CM required conformal geometry and orientation to provide the necessary thrust vectoring for Roll/Pitch/Yaw. To reduce cost and simplify RCS system architecture, Rocketdyne adopted the identical SE8-9 design for each of the 12 CSM installation locations; the correctly shaped nozzle extension was attached to facilitate the proper orientation of the engine at a given location on the flight vehicle.

The nozzle extension on the newly acquired artifact configures the engine for application in the negative (-) Pitch role.

Heritage during its cataloging process did not fully image the artifact; only two lateral shots were offered and from those images it was apparent (based on the presence of Dow Corning RTV on the “can” ) that the engine had been mounted to a fixture. It wasn’t until receipt, and after examining the engine that it because apparent the engine was formally affiliated with CM 008 (the Command Module that was utilized to conduct manned test “flights” within the confines of a vacuum chamber).

From the final image below (NASA S66-59221 depicting CSM-008 in prep for testing), definitive correlation established the artifact was indeed associated with that test effort and more specifically as the upper (-) Pitch engine. One of many differences between the Block I and Block II CSMs is that the two (-) Pitch engines on the Block 1 were configured vertically; this changed on the Block II (mounted side by side) presumably to facilitate implementation of other design fixed such as the Unified Hatch on the Block II.

posted 06-19-2022 01:21 PM               

Re scarfed/scarfing/scarfing-angle, learning a new term here.

Trying to understand if the 'scarfed' refers to the wrapping/sleeving aspect of the ablative nozzle extension or is it related to ablative fitment with metal nozzle as in scarfed joinery in woodworking? I gather scarfing angle refers to an oblique exhaust exit plane vs direction of thrust.

I found the terms widely used but not cleanly-defined, though this 1968 Boeing document was helpful.