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  Gemini (SE-6) Reentry Control System engine

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Author Topic:   Gemini (SE-6) Reentry Control System engine
SpaceAholic
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posted 10-25-2009 02:39 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Acquired a second Gemini SE-6 engine (thrust chamber on the right in the first image) and, although I lack specifics on provenance, have concluded it was flown based on the following:
  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.
Anybody concur/non-concur and if so please provide rational.

space1
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posted 10-25-2009 06:16 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
All of your points are good ones, and I can't really argue against any of them. But it should be helpful to compare the thruster with the flown thruster in my collection.

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.

------------------
John Fongheiser
Historic Space Systems

SpaceAholic
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posted 10-25-2009 09:36 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Here is the Tag (click for higher res images). Note "1Q 64", which was well into the production window for the spacecraft (Q2 saw the first flights) and "D 6637" stamped on casing.

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?

SpaceAholic
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posted 10-25-2009 10:04 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Here's an example of an SE-8 in my collection (the phenolic ablative nozzle is of essentially the same design as that used in the SE-6). This SE-8 has undergone extensive firing, yet no evidence of external ablation. Click for larger image:

dsenechal
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posted 10-25-2009 10:16 AM     Click Here to See the Profile for dsenechal   Click Here to Email dsenechal     Edit/Delete Message   Reply w/Quote
The Cosmosphere in Hutchinson did a restoration one of the Gemini spacecraft (6?). Perhaps they have some photos or other documentation available.

Regarding the orientation on Scott's thruster, it looks as if it had been removed at some point, and then re-affixed. This may explain the horizontal vs. vertical placement.

Robert Pearlman
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posted 10-25-2009 11:12 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The Cosmosphere's Gemini 6 restoration diary and photographs is archived here.

space1
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posted 10-25-2009 11:47 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
Let's tabulate some numbers:

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).

Regarding the evidence of the sticker being removed, it looks as though the removed sticker may have been square.

SpaceAholic
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posted 10-25-2009 02:38 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
quote:
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.
Material from the ablator has been splattered back off the face of nozzle onto the can... I am virtually certain the type of environmental conditions required to do that were not replicable in a lab during the 60's.

space1
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posted 10-25-2009 06:04 PM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
Having ablator spattered on the can is actually not likely for an installed thruster. The RCS section skin sheltered the interior of the RCS section. And the oval cutouts for the thrusters were sealed with a fiberglass seal that covered the mating surface (the white material seen in the Gemini 7 photo).

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.

So I'm still not sure if it is flown, only that it might be flown.

SpaceAholic
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posted 10-25-2009 06:51 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
John... I was referring to the residue which lay adjacent to the ablater/nozzle where the engine attaches to the flight vehicle mold line (similar to the material deposited at the same location on your thrust chamber)...the material is worn down, probably discolored and looks a bit like burned ablator but could just as easily be phenolic resin...

space1
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posted 10-26-2009 04:18 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
I think you are right about that residue. It also looks similar to the flown thruster shown on the Gemini 6 restoration diary.

Does the can have other numbers and markings? The thruster in my collection has quite a few all around.

SpaceAholic
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posted 10-26-2009 08:14 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Many - but they are challenging to image. (Click for larger photos):

space1
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posted 10-26-2009 09:33 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
Thanks for the good pictures.

I have to agree that everything physical about the thruster indicates it is flown. All the can markings are consistent with a flight article. The only confusing factor is the tag. Since another tag was obviously removed, I'm going to go with this being a flown thruster which was then re-tagged, perhaps for testing purposes. A new part number was probably assigned, making it higher than the numbers for the other flown examples. It may be very difficult to determine the flight, especially if numbers on the tag were changed.

SpaceAholic
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posted 10-26-2009 09:45 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Probably the only way to correlate with a specific vehicle is to review archival images of the installed RCS engines taken post flight and try to match physical characteristics (thats if sufficiently resolved images exist)...

SpaceAholic
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posted 10-27-2009 12:01 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
The below reply received from retired Rocketdyne Engineer Tim Harmon, an authoritative expert on ablatively cooled engines who developed the SE-7, SE-8 and Lunar Module Ascent Engine, responding to my inquiry regarding the probability that the engine is flown. SE-6 development/testing was concurrent with the SE-7/SE-8's.

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.

space1
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posted 12-14-2009 11:40 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
I have found a "smoking gun," or really a smoking thruster, that I believe places this thruster on Gemini 3 before its flight.

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.
The serial number matches this artifact. It is apparent that the thruster was later used for tests and was given a new ID tag with new part numbers, and a prefix for the serial number, "NA". But the exact match of the serial number, combined with the evidence presented by the artifact itself. leads me to conclude that this artifact flew on Gemini 3 as TCA #4 on Ring "B".

(TCA #4 was a yaw right thruster, mounted at the lower [edit]left of the Reentry Control System section. Ring "B" is the aft set of the two sets of thrusters.)

SpaceAholic
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posted 12-14-2009 12:46 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
That's a heck of a sleuthing job John - I am delighted (and grateful) beyond words this engine's history could be reestablished; the high confidence determination it had a direct role in the first manned Gemini mission makes the discovery even more savory. Thanks for going "above and beyond".

space1
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posted 12-14-2009 01:26 PM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
I'm just lucky I got such a helpful document. It's a bit ironic that you now know more about your thruster than I do about mine :\

Lou Chinal
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posted 12-14-2009 01:51 PM     Click Here to See the Profile for Lou Chinal   Click Here to Email Lou Chinal     Edit/Delete Message   Reply w/Quote
Scott, I would just like to point to a photo of Gemini 3 posted at the "Virgil Grissom Memorial and Museum" on this site. The thrusters have been removed.

SpaceAholic
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posted 12-14-2009 02:27 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Where is that Lou? This site has gotten so expansive its getting more difficult to keep track of where everything is located...

Robert Pearlman
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posted 12-14-2009 02:33 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
I beleive Lou is referring to this topic: Virgil Grissom Memorial and Museum.

freshspot
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posted 12-14-2009 03:08 PM     Click Here to See the Profile for freshspot   Click Here to Email freshspot     Edit/Delete Message   Reply w/Quote
Nice one Scott and John. Evidence of flown status for an artifact like this is terrific.

Dave Scott (not the astronaut)
Apollo Artifacts

Zero G
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posted 02-15-2013 06:55 PM     Click Here to See the Profile for Zero G   Click Here to Email Zero G     Edit/Delete Message   Reply w/Quote
I purchased this SE-6 engine from Bonhams last April.

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.

Editor's note: Threads merged.

SpaceAholic
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posted 02-15-2013 06:56 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Compare with the above examples of a couple of SE-6 engines, which are established as flown thrusters.

space1
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posted 02-15-2013 08:32 PM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
I don't have any data about Gemini 6 thruster serial numbers.

Robert Pearlman
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posted 02-15-2013 08:43 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
As noted above, the Cosmosphere restored Gemini 6 in 2003. From the restoration journal they produced for collectSPACE, here are two RCS engines from that flight:

Based on a comparison of the above with the auction photo of your SE-6 engine, I would say there is no chance that it flew.

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