These are notes, observations, and links distilled from discussions on the Space Modelers E-mail list. This External Tank discussion is from October 1999. Specific topics are as follows:
The STS-96 photo gallery featured some excellent close up images of Discovery's external tank, taken during repairs of some hail damage it sustained. The ET cone tip for that mission was a very strange, dark metallic color and it looked almost like it was made out of Inconel or Carbon Fiber. Also, the ET texture was very easy to make out, as well as the color for the current ET flight hardware. Another interesting marking change I've noticed on the pictures of the recent orbiters is that the wing hinge cover panels are no longer a dark metallic color, but instead are white with black edges. Columbia appears to be the only shuttle with the metallic hinges right now, but this may change when it returns from Palmdale, for it's next flight in 2001.
[space-modelers] "Found some interesting shuttle pics", 10/6/99
All the tanks come in from the factory a light tan in color, and as you know, can eventually reach a chocolate brown depending on how long it sits on the pad in the sun. Any orange tinting should be very subtle. Actually, I think the orange influence is attributed more to what the sunlight is contributing that day whether it be close to sunrise or sunset than anything else.
And it gets worse than that. The super-lightweight ET's, which first flew in 1998, have an even lighter color initially, it seems. See:
The color of that ET on first arrival was a cream or butter-cream color, with some areas (such as the aft attach struts for the orbiter) appearing white. By the time those tanks are flown, they are darker, but not nearly as dark as the previous tanks were.
Compare the tank color of Columbia being taken to the pad March 23 1998:
......With the color of the tank when it actually flew on April 17, 1998:
You can see how much darker it got due to exposure to the sun and elements in about 3.5 weeks. And in some other pics it looks almost like the ET nose got a little darker than the rest of the tank, like the nose got "sunburned".
Bottom line though is that the tanks now are not as dark as they had been. I do not know why. Since they are super-lightweight tanks I could speculate that the spray-on foam itself might be of a different formulation than before, so that it is lighter in mass and happens to be lighter in color initially.
In any case to take note of the graphite ET nose cap and the graphite fairing over the Lox line at the intertank.
For other photos of other missions to check over, try this index:
- George Gassaway
There are just so many variables involved. Sometimes there is a covering over the open end of the barge carrying the ET causing less sunlight exposure during the trip from the factory. In some cases, the vehicle spends less time on the pad before launch, especially if it comes to the pad with the payload already installed. Also, public affairs now shoots a lot of their images with digital cameras and I've noticed the digital cameras sometimes have trouble reproducing reds, yellows, and tans. But like you said, you've got the full range from a very light tan/butter kind of color to chocolate brown. So you just can't go wrong with that variety.
BTW, the darker band just aft of the black phenolic nose cone is sanded foam covered by topcoat, which is a darker color/light brown. This is done to provide a good sealing surface for the GOX vent seals.
[space-modelers] "Repeat Question: ET Colour", 10/7/99
Before the Super Lightweight Tanks, the intertank area has always been noticeably lighter in color than the rest of the tank. This is because they sand or shave off the harder, darker outer layer (the rind) revealing the lighter colored material underneath. This is done to reduce the weight of the ET. The chemical composition of the foam insulation was changed recently due to the ban on the use of freon. The "new" foam doesn't maintain integrity quite as well under high heating conditions and some pieces have been coming off, so we have sanded the foam still thinner to design "minimums" to still protect the aluminum skin, yet decrease the amount of foam that potentially could come off.
Edited from: [space-modelers] "Re: ET Tank Color", 10/8/99
More directly related to modeling, those numerous light-colored areas on the ET are "close outs" done by hand where some contour trimming and sanding of the foam has taken place (and the textured, darker "rind" removed). These areas are well defined, can be easily seen in photographs, and have remained fairly constant in terms of modifications for some time now. These areas are light tan, or "butter" colored, in appearance and darken at a very, very slow rate. So you can incorporate those into your model no matter where in the flow you have "captured" the Shuttle.
Edited from: [space-modelers] "Re: ET Tank Color", 10/8/99
In a message dated 02/26/2000 10:46:37 PM Eastern Standard Time, email@example.com writes:
>> Are the struts that attach the shuttle to the external tank >> always white or are they the same variable rust color?
There are a total of 11 structural connections. Depending upon the level of detail you want to model......
As Karl pointed out, the forward attach struts (bipods) between the Orbiter and ET are no longer top-coated brown. The natural color of the ablator, a weird kind of light pink, is now fully exposed for flight.
The big, heavy duty metal fittings on the ET that provides the (aft) structural attach points to the Orbiter is a light korpon (not sure of the spelling at this time of the morning) green.
The two forward attach points from each SRB to ET are a variety of colors. The large metal fittings that carry the flight loads are the same as the forward skirt - a flat white. Above each fitting, the various covers and closeout panels are white, tan, and dark brown topcoat.
The aft struts connecting SRBs to ET total 6 in number. The diagonal and lower struts (farthest away from the Orbiter by way of positioning) are just polished metal. The two upper struts contain the electrical cables, which must be protected. So these struts are encased in fairings - flat white in color.
[space-modelers] "Repeat Question: ET Colour", 10/8/99
In a message dated 10/08/1999 6:34:13 PM Eastern Daylight Time, JMChladek@aol.com writes:
> Hey Greg, I have another ET question. What color are the attachment struts > for the orbiter and the LOX LHX feedlines on the new tanks? Looking at my > references, it appears that they are done in the lighter shaded ablative > coatings, like portions of the tank itself, but I haven't found any > definitive color shots yet.
The LOX umbilical has four connections between the ET and the Orbiter. The 17-inch LOX feedline and the cable tray are covered by foam insulation, which has been sanded smooth (reference all previous discussions here where the exterior, darker, rough "rind" has been removed) and is a light tan, or "butter" kind of color. As you know, these areas can reach a dark brown color depending on the length of time the ET sits on the pad in the sun. For the most part, it retains the light tan to "butter" color and is extremely slow to darken compared to the "acreage" areas of the ET.
The 2-inch pressurization line is not insulated (it is bare metal) and is gunmetal color. The adjacent cable tray formerly was top-coated (brown), but now we just fly the plain ablator covering, which in this case is a type of charcoal gray.
The LH2 side is exactly the same, but there is also a 4-inch recirculation line covered with the sanded foam and is light tan/"butter" colored. Both the LOX and Hydrogen feedlines entering the Orbiter (near the two green structural fittings) are covered by sanded foam and are the light tan to "butter" color.
Edited from: [space-modelers] "Repeat Question: ET Colour", 10/8/99
I have tried in the past to match the ET color and have done so with some satisfaction on my part. The problem of the ever changing tones of the ET makes it a bit difficult. I usually tell people that the color should be done to "taste" - newer or having been on the pad for a while.
For the record, I like to start with this mix of Testors Model Master paint:
This is not a hard and fast color mix, but for those of you trying to get the color to your satisfaction, it's a good starting place.
[space-modelers] "Re: Repeat Question: ET Colour", 10/7/99