Apollo SM RCS units.
 

Does anybody have a true color photo or diagram of the RCS nozzle quads on the Apollo Service Module? I’m pretty sure they’re not suppose to be just plain white.

Thanks!

Looks like it's all silver (Apollo 15).

All of the RCS motors were test fired after manufacture. I took this picture at NARCON last year in Houston. They are sort of goldish and silver. One recommendation that I heard was a burnt platinum. I would not go straight white or silver.

Chas

Chas beat me to it, with a better picture than the one I would have put up (but taken of the same vehicle - the full Saturn V that is on display at Space Center Houston). The nozzles look to me as if they are either titanium or stainless steel discolored by heat. Based on Chas' picture I am leaning toward the latter.

The ones I have photographed at KSC and NASM (in D.C.) have had silver quad 'boxes' like this one (my photos are not immedialtely accessable).

As can be seen, there is printing on the top of the box, which I forget the exact nature but seems to deal with quad firing order or something similar.

Here's a link to the photo: https://upload.wikimedia.org/wikipe...lo_RCS_quad.jpg


Earl

Hey Jeff!

Yeah, basically the quad "boxes" are white, and the nozzles are sort of a "gunmetal" color...
Actually, "gunmetal" isn't quite right... they sorta have a slightly "gold" color to them, or "brass" color maybe. I got curious in the middle of digging these up and searched for it and found the Apollo operations handbook on PDF and here's what it actually says about the thruster quad construction materials...

"Combustion chamber- The combustion chamber is constructed of unalloyed molybdenum which is coated with molybdenum disilicide to prevent oxidation of the base metal. Cooling of the chamber is by radiation and film cooling.

Nozzle extension- The nozzle extension is attached to the chamber with a waspalloy nut. The nozzle extension is machined from a cobalt base alloy (stainless steel). The stiffener rings are machined."

Here's some pics of the CSM display at Kennedy Space Center, below the Saturn V, and of the Saturn V itself.

I'll see what I have regarding the CSM on the Saturn V in Huntsville and of course the one here in Houston as well...

Later! OL J R :)

Take a look at the photo link in my prior message and a second look at your photos (I have similar photos of those same RCS quads at KSC myself).

The quad *boxes* themselves are silver...that 'top of the box' white you see is the 'printing' I mentioned above. I think it might actually be a label applied to the top of the quad box.


Earl

Here's pics of the ones at JSC... remember these were outdoors in the terrible Texas coastal weather and salt air, hurricanes, heavy rainfall, and tons of nearby chemical plant pollution for over 30 years before they built the building over it... So that will definitely have SOME effect on things...

later! OL J R :)

Here's some from the Kansas Cosmosphere... these are on the CSM in the Apollo/Soyuz Test Project display, which shows a Soyuz and Apollo CSM with the docking adapter...

Note the writing and color of the nozzles... these are probably the most accurate. The others on display may have painted "boxes" or otherwise have been either weathered, refurbished, or both.

The lighting in the Cosmosphere may throw off the pics, as it's rather subdued, but you can at least get the idea... this is probably the closest I've gotten to them...

I'll see what I have in my Marshall Space Flight Center (USSRC) pics since the Davidson Center is lit mostly by natural light and will probably have the best color rendition on the camera...

later! OL J R :)

Here's the pic I have of the Saturn V at Marshall in Huntsville... obviously of no use since it's some sort of mock-up to stand in for the CSM/SLA panels on top of the S-IVB. They have a trainer mockup of the CM there as well that you can actually slide into.

Later! OL J R :)

Yep hard to go by museum stuff, particularly the ones that have been on outside display... the get corroded or paint or coatings become discolored or peel and get painted over with "whatever is available" or "whatever they can afford" and that's that... particularly years ago when keeping it "as close to original as possible" wasn't any particular priority...

The writing appears to be a chart that helps with wiring and orientation for translation... the motors had to be wired correctly to fire in the appropriate pairs or orientation to provide the required rotation of the vehicle in the +/- X, +/- Y, and +/- Z axes, as well as thrusting forward and aft, and translating the spacecraft up/down and side to side in those planes...

Later! OL J R :)

I think the JSC Saturn V was completely restored/repainted when it was enclosed, and maybe the same for the KSC and ASRC Saturns as well.

I am surprised, somewhat, to see the JSC Service Module (and quads) with the paint scheme it shows. The main 'body' of the Service Module has been rendered in a plain gray, which I'm pretty sure NO flight Saturn V ever had. The radiator panels as white is correct, but the solid white quad boxes is not.

John Pursley, who posts here some, was heavily involved with the JSC project as I recall and is one of the foremost Saturn V modelers/historian. Maybe he can fill us in at some point on some of those color choices, but they seem out of place to me when compared to many, many flight vehicle images.

The KCS Service Module and Command Module you featured in your first batch of photos is, as I recall, actual leftover flight hardwear and appears to have never been mollested from a 'restoration' effort. I have looked over that hardware there on a number of visits to KSC over the years and have some extensive photos of it, but they are not easily at hand (a la paper prints).

Earl

I have a closer shot of the Cosmosphere CSM...I took it precisely because this question came up during my Saturn 1B scratch build

Comrades:

I use flat aluminum and Testors Jet Exhaust for the thrusters. They look great and just like the picture above.

Apollo 6's Service Module was mostly white (it was the only one of that color), while the others had various combinations of metallic finishes (not painted, at least for the most part). The Skylab Command Modules were mostly white (I think), due to their longer in-space stays and sunlight/darkness exposure cycles; this doesn't seem to have necessitated any surface finish changes for the Skylab Service Modules (even Vanguard 1, which has an all-metallic finish, didn't have any day/night thermal cycle problems, as it transmitted for six years, until radiation finally degraded its early-type solar cells).

Yes, of the Apollo missions, specifically the Saturn V missions, Apollo 6 was kind of the odd man out with that pretty much fully white SM. Here again though, it was not the gray color as shown on the JSC Saturn V currently on display, so I'm still not sure where the JSC folks came up with that color combination.

As best I can tell from the harware I have seen on display (some of which was actual excess flight hardware), the 'silver' color of the SM appears, in many places, to be a silver paint (high temp one would assume) over the outer structure. I had assumed for many years until I actually saw some of this hardware that the 'silver' we all saw in the launch photos and such was actual 'bare metal'. Not the case in most instances. It seems that, as I recall, a good portion of the SM outer surface is covered in a layer of somewhat thin insulation (possibly a cork-type material, as was the case for a portion of the Boost Protective Cover or BCP for the Command Module) which was then painted with this silver paint. From any real distance however it appears to be a metallic surface.

The 'silver' of most Command Modules (save for the Skylab CM's as you noted above) is a covering of relatively narrow strips of what I recall to be highly reflecitve mylar, definately giving it the appears of a bare 'metal' finish (as a kid, I thought this outer surface was some type of relatively light stainless steel shell of some sort). These strips of material can be seen burnt off and hanging in small, torn sections on many CM's during recovery operations in the ocean.

Earl

This is what John Pursely told us as he was leading us in a tour of the JSC Saturn V at NARCON last year.

My thanks to all of you for your help with this! I’ll paint the RCS units when I return home from a job in Kittery, Maine in March. Yes, it’s cold here!

Ah--that makes sense. The cork-like insulation likely had a somewhat shiny outer coating (possibly for rain protection on the pad), which made it look like an unpainted but somehow "treated" (anodized, sand- or bead-blasted, etc.) bare metal surface (and here is a Skylab CSM docked to Skylab: https://space.stackexchange.com/que...csm-white-paint ). Also:

I once read that Maxime Faget didn't think the metallized Mylar was necessary on the Command Module for re-entry protection because it was on the lee side, behind the heat shield (it helped for thermal control in space, but the Skylab CMs' white finish worked just as well for that), and that NASA was being "old hen-ish" and overly conservative by requiring it to be applied to the spacecraft. After Apollo 4 landed after a lunar return velocity re-entry (although it might have been Apollo 8 or a later lunar-return Apollo, as I'm not sure if Apollo 4's CM had the metallized Mylar sheathing), he triumphantly showed a removed, un-burned swatch of the metallized Mylar to the NASA personnel who had insisted that it was necessary for re-entry protection.

It might not have been necessary, but it sure made the Apollo 9 EVAs look cool wth Scott's and Schweickart's red helmets in the frames.

Oh, yes--in photographic composition, good contrast makes a big difference, and the shiny CM sides did that for Rusty's spacesuit. That red-helmeted suit reminds me of the 1969 movie, "Marooned," where David Janssen's character (Ted Dougherty) flew the experimental X-RV lifting body to effect the rescue.

the nozzles look like they are constructed of a Cadmium and Nickel Alloy. Cadmium gives off that Yellow / pink hue. my guess would be that these motors are probable Hypergolic.

Those thruster nozzles are related to our hobby. Back in the mid to late 90's, some friends down in Huntsville decided to do an amateur high altitude project. It was a rockoon (balloon launched rocket). My buddy Jim built the motor hardware and we cast a few propellant grains for the hybrid. However, they wanted it to be a "dirt rocket". I.E. use tar for the propellant grain. Jim's grains were more potent, but the tar was just something they wanted to use because somebody said it wouldn't work. We did test firings at Tim Pickens' (eventual designer of Spaceship One motor) parents' land. The rocket was successfully tested via a ground launch in Manchester, TN that used every bit of the 15k waiver. The balloon was eventually launched off a barge in the Gulf and the rocket made a successful flight, but I don't recall the altitude. It was in Guinness as the highest amateur flight for a few years.

Now to relate it to the space program's reaction control thrusters. A lot of old hardware from NASA ended up in a couple of junkyards in Huntsville. Tim found some of them and used an expansion bell from one to make a mold for the dirt rocket's high altitude motor. The more I think about it, I'm pretty sure it was from Surveyor instead of Apollo, but it's still cool as heck. Maybe Tim, Dan or one of the old crew is lurking and can remember it better than me.

Wow--talk about melding (or molding, in this case) past and present! Those Surveyor verniers (three per lander) stabilized the spacecraft while the big, spherical STAR-37 solid motor (a derivative of which served as the Thor-Burner II and Thor-Burner IIA second stage: https://en.wikipedia.org/wiki/Thor-Burner ) did the "heavy lowering," then--after the spent STAR-37 was jettisoned at about 6 miles up and 250 miles per hour--braked the lander to 0 mph about 13 feet above the surface, then shut down. The 13' free-fall was equivalent to just a 2' one on Earth, whose impact the landing gear shock absorbers and crush-able footpads (which were never compacted, to my knowledge) easily absorbed. Also:

The World War II-era Private A and/or Private F used asphalt-fueled composite solid propellant. It worked well, but got very soft at tropical/desert temperatures and cracked at very cold temperatures; tar, I imagine, is more physically stable over such a temperature range.