Shuttle external tank

[smeds]

Anyone know of a good colour for the Shuttle external fuel tank. The Monogram instructions call out for orange !

[GordonD]

Anyone know of a good colour for the Shuttle external fuel tank. The Monogram instructions call out for orange !

The colours varied because the foam tended to fade in the sunlight, so any shade of reddish-brown would be appropriate.

[Jay]

Yep Gordons right. The tanks are cream coloured when they are delivered, but once they are sitting on the pad for a while being exposed to sunlight, they can turn from a orangey rust to chocolate brown colour. Best bet is to check your references for the shuttle you are going to build.

[Mike]

I was given a bottle of a Games Workshop colour that looked pretty good to me. One of the Chaos colours IIRC, and a sort of Korma brown/orange... Julien gave it to me with a 1:144 shuttle I bartered off him

[GordonD]

I was given a bottle of a Games Workshop colour that looked pretty good to me. One of the Chaos colours IIRC, and a sort of Korma brown/orange... Julien gave it to me with a 1:144 shuttle I bartered off him

I read that as "...a 1:144 shuttle I battered off him", giving me the impression you'd beaten him up and nicked it!

[smeds]

Thanks for the info guys

[bootneck]

Thanks for the info guys

Hi Smeds,

the ET's were not a uniform single colour as you can see by the first image below.

The other images show the changes in colour, as already mentioned.

Check out the NASA website for more details

cheers

Mike

[JMChladek]

The full color range of the ETs starts at a slightly off white shade once sprayed and then darkens to tan, light tan yellow (almost like pancake batter color), then darker yellow, to orange, burnt orange and finally the browner shades. If the surface of the foam is chipped or sanded to expose the inside color, the process starts all over again. The best bet here is to pick a photo for a specific mission and match to it.

As for colors I've used, I've got access to the Floquil Railroad colors in this country and they work very well when doing 1/72 tanks as the colors come in BIG bottles. I typically only try to mix two colors at most as to me, witches brew paint formulas of three or more colors make work initially. But if you have to do a touchup (and you can mix a GALLON of the stuff and still run out), trying to duplicate the formula is tough, especially with orange shades. Be aware also that orange shades in pictures can look very different depending on the lighting. So with those two moving targets in mind, pick photos from one mission and match to that as best as you can.

Colors I have in my ET tank shade arsenal include (all Floquil shades):

SO Freight Car Brown

UP Armor Yellow

UP Light Orange

SP Daylight Orange

By mixing the different oranges with freight car brown, I can usually get the orange/brown shades to my satisfaction as needed. Granted some of these may not be available in UK markets (check the model train shops for these), but if you can stock up on some different orange shades and maybe a couple light browns (hence Citadel colors would probably work fine) you should be in good shape.

Here's the colors in action on my STS-117 stack (the real ET had some patches applied to it due to hail damage, which forced a launch delay)

STS-107 1/144 Airfix stack. Colors for the ET here were a three color mix (and when I had to do touchups, it was TOUGH to duplicate the shades). I use this as an example to show a different tank coloring.

And finally, STS-131 in real life (RSS rollback, less than 24 hours before launch). The slightly lighter shade you see on the lower section of the ET is due to the Rotating Service Structure around the orbiter covering up part of the tank. So it gets a tan line. The back side of the tank will have a more uniform color shade since it gets sun exposure, just like the nose of the ET.

Edited June 10, 2012 by JMChladek

[John]

This is a pdf from the most recent boxing of the Airfix kit - it's available on Airfix.com.

http://www.airfix.com/_assets/files/A10170%20H.pdf

John

[smeds]

Thanks guys, a wealth of info there

[Tabio]

Yeah it starts off a yellowy colour until the sun gets on it, if you want some good pictures and a great read I'd recommend the Haynes manual for the shuttle

[smeds]

Thanks Tabio,

I have the Squadron walkaround, now I'll have to get the Haynes manual.

[pigsty]

I never realised that about the coating darkening. Just how long do they leave tanks exposed to the light before launch?

Edited June 14, 2012 by pigsty

[smeds]

That makes two of us, I thought the lighter colour was some sort of primer/undercoat.

[GordonD]

That makes two of us, I thought the lighter colour was some sort of primer/undercoat.

The tanks are unpainted (apart from the first two launches when they were white) - that's the colour of the spray-on foam.

[Jay]

Here's some awesome detail shots Smeds, should be useful.

http://www.spaceflightnow.com/shuttle/sts135/110705gallery/

and another site.

http://troymcclellanphotos.smugmug.com/Spa...8&k=nMsjjDq

Edited June 14, 2012 by Jay

[Mike]

Cool pics on that first site

[JMChladek]

The first two tanks were painted in white FRL paint. FRL was NASA's acronym for Fire Retardant Latex and they reason why they did it is they were concerned that the darkening of the foam due to UV exposure might also weaken it and make it more prone to cracking off. Eventually, they discovered that the foam worked just fine even when exposed to months of UV light, regardless of whether it was painted over or not. So they left the paint off and saved about 500 lbs. in flight weight in the process.

The foam applied is either machine sprayed or hand applied (either sprayed on with a special hand gun or poured and molded). Where you see lighter color areas on the tanks are typically the hand applied foam around the intertank, access doors and ramps where fuel line brackets are located (to clean up the aerodynamics). Most of the darker spots are machine applied acreage foam and they are typically rougher in texture than the hand applied pieces (which are either made in molds or shaped by hand with cutting blades and/or files). The 1/72 Monogram shuttle stack kit tried to duplicate this rough texture. IMHO, they did a decent job with it, although trying to deal with the seams and match the texture can be a bit of a chore during construction (texture paint works well for duplicating it though IMHO).

As for how long the tanks are exposed to UV light? Well, that depends on how long the tank spent manufactured before use and how long the shuttle sits at the pad. During the shuttle missions where everything went like clockwork, the colorings stayed close to the same as the shuttle might be stacked at the pad for a month at most (although a shuttle stacked in the spring summer months is going to get more sun than one stacked in the winter). But, if a shuttle had to get rolled back to the VAB for repairs, then rolled out again (such as on STS-133, or STS-117 with its hail damage), it would be a little darker in spots. If the shuttle spent two to three months at the pad, such as for a main engine change out (caused by an abort, since the SSMEs have to be replaced once they are fired) then the tanks can almost get milk chocolate brown in color.

The foam formula NASA used on the external tanks was changed a little in the mid-1990s when they switched from a CFC based propellant in the spray nozzles to something more environmentally friendly and I understand this changed the appearance of the colorings a little. But I think part of that was also due to how long a tank would stay in storage before use. Going back to the very early days of shuttle with the dark brown tanks, NASA was trying to ramp up to about 12 flights a year before Challenger was lost in 1986, so they had A LOT of tanks in production and in storage before use. So I believe the reason why several of those tanks got as dark as they got was not because of anything really all that different about the foam, but rather because they spent months in storage after assembly.

As I said before though, the moral of the story is to match photos of a specific mission. Color recommendations can be provided, but EVERY external tank was a little different in its colorings due to so many variables. So what may work for one ET may not work for all of them. You'll likely have to mix your final color shades to get close to an exact match.

[pigsty]

^^ all very informative, thanks. Though it does lead me to ask, why park the thing for a month in all weathers before firing it? Even my car gets less abuse than that!

[JMChladek]

^^ all very informative, thanks. Though it does lead me to ask, why park the thing for a month in all weathers before firing it? Even my car gets less abuse than that!

Well, by the same token, your car isn't "one use" is it? You don't just drive to work and jettison it, do you? Partly due to when the shuttle was designed and partly due to the budget NASA had to develop it under (they sacrificed operational costs to keep the development costs down) it takes a little while and a certain amount of manpower to prepare a shuttle for launch with all the methodical fit checks and tests that need to be conducted. Arming devices are also installed at the pad.

When a shuttle stack gets to the pad, the orbiter itself gets covered over with the Rotating Service Structure (RSS) which acts as a garage on the pad. At the RSS, they can load payloads. Typically ones that have fuels onboard are loaded at the pad vertically through the RSS while other payloads are put in horizontally when the shuttles are in the Orbiter Processing Facilities (OPFs). This is done for safety since the bird sitting on the pad is a semi-live vehicle. So if it blows up out there, there is less danger than doing it in the VAB or an OPF. Of course, the VABs were also kept off limits during the shuttle program due to storage of the solid rocket boosters.

Inside the RSS, the orbiter is VERY well protected since the payload loading section is a cleanroom environment. There are other areas of the shuttle that need de-humidified dry air blown on them to protect the structures from the Florida weather. The RSS can handle most weather issues that crop up, although in the event of a tropical storm or a hurricane, a shuttle typically gets rolled back to the VAB. Florida weather also typically has two seasons, hot and wet or hot and not as wet. There are times the temperatures dip below freezing, but that doesn't happen very often. The ET itself can handle being outside in the rain since it was designed to be disposable (its an oversized drop tank). The SRBs are also pretty heartily built since they are designed to crash back into a harsh salt water environment.

So the orbiter in a sense has a garage on hand almost everywhere it goes on the ground. Once it comes back from space, it gets trucked into an OPF and stays there. Only time it comes out is when it gets transfered to the VAB to mate with the ET and SRBs. After that, rollout to the pad (which takes place when the weather is forecasted to be calm) takes about a day and the orbiter gets covered up again by the RSS for about a month. After that, the RSS comes off the orbiter less than 24 hours before scheduled launch, but it can be put back over rather quickly in the event of a launch scrub. Other than those times, the only period where a shuttle orbiter can remain outside for a few days is if it has to be ferried back to KSC from Edwards AFB, or if it was being sent back for a refit in California. Your car never had it so good.

[GordonD]

So the orbiter in a sense has a garage on hand almost everywhere it goes on the ground. Once it comes back from space, it gets trucked into an OPF and stays there. Only time it comes out is when it gets transfered to the VAB to mate with the ET and SRBs. After that, rollout to the pad (which takes place when the weather is forecasted to be calm) takes about a day and the orbiter gets covered up again by the RSS for about a month. After that, the RSS comes off the orbiter less than 24 hours before scheduled launch, but it can be put back over rather quickly in the event of a launch scrub. Other than those times, the only period where a shuttle orbiter can remain outside for a few days is if it has to be ferried back to KSC from Edwards AFB, or if it was being sent back for a refit in California. Your car never had it so good.

Ever read a novel called Shuttle Down? It's by the aerospace writer G. Harry Stine, under the pen-name Lee Correy. It concerns a Shuttle which suffers a main engine failure shortly after launch from Vandenberg - they have to make an emergency landing on Easter Island and the novel covers the efforts (both technical and political) in getting the Orbiter back to the USA. No doubt it's long out of print but you might be able to pick up a copy on eBay or in a second-hand bookshop somewhere.

[JMChladek]

Ever read a novel called Shuttle Down? It's by the aerospace writer G. Harry Stine, under the pen-name Lee Correy. It concerns a Shuttle which suffers a main engine failure shortly after launch from Vandenberg - they have to make an emergency landing on Easter Island and the novel covers the efforts (both technical and political) in getting the Orbiter back to the USA. No doubt it's long out of print but you might be able to pick up a copy on eBay or in a second-hand bookshop somewhere.

I have actually. I borrowed a friend's copy and read it about 8 years ago. Very good book.

[Anthony Kesterton]

The book sounds interesting - there are a few copies available on Amazon (-1 that I just bought :-)

Back to the topic - this is a really interesting discussion on the tank colours.

anthony