BAC Mustard spaceplane

[Weaver]

Since we have two commercial models in the works (Spot-On Designs and S&M Models) it seems reasonable to start a thread for this.

For those who don't know, MUSTARD (Multi-Unit Space Transport And Return Device) was a 1960s BAC Warton study for a reusable space launcher. It consisted (in it's most developed form) of three lifting-body shaped vehicles stacked together for vertical launch. The outer two vehicles were boosters and the inner one the orbiter. When all three were down to 1/3 fuel, the engines would be cut and the boosters would transfer all their remaining fuel to the orbiter. The three would then separate, and the orbiter would then restart it's engines and continue to orbit, while the boosters would fly back to make a runway landing using auxiliary turbojets. After it's mission was completed, the orbiter would re-enter and then do likewise. The project strenuously avoided any exotic high-risk systems or materials, and the three vehicles were almost identical, leading to cost savings by common design. All-in-all it looked like a very credible project. It died principally because of pre-ESA European space politics and the UK government's unwillingness to invest in it unilaterally. The work done on Mustard got the BAC Warton team invited to take part in the early US Space Shuttle studies and they designed several components for it, but again, the UK government wasn't willing to keep funding their participation.




Now here's a question. What colour should it be?

All the images of MUSTARD in BSP-5 show it with a white topside and black underside and leading edges, and the captions repeatedly make the point that it would probably be wholly or mostly unpainted to save weight, leaving it in it's 'natural' black metal finish. Here's the thing though: the underside was to be made of René 41 alloy and the topside of titanium, and neither of those materials is 'naturally' black: they're both silver-grey, a little duller than aluminium when polished. I've got a picture of an unpainted A-12 (SR-71 predecessor) which is definitely silver-grey and there are many pictures of René 41 available. On the other hand, the outside of the Mercury space capsules was covered in René 41 shingles and they appear to have had a very dark grey colour, which can't be caused by heating 'cos they look pretty much the same on flown and unflow vehicles.

Could it be that the BSP-5 author/artists just took their inspiration from the Space Shuttle (whose heat tiles are totally different), or did they assume that the Blackbird's black was the natural titanium colour (it wasn't: it was paint), or is there something I'm missing? Why were the Mercury shingles so much darker than 'raw' René 41 - oxidation or some kind of coating? Also, what would a MUSTARD underside, however it was finished, look after re-entry?

[zenrat]

...Now here's a question. What colour should it be?...

Easy.  Black/Yellow checks, Chris Foss style.

[PR19_Kit]

Medium Sea Grey over PRU Blue as it'd be the highest altitude PR aircraft ever............ 

B type roundels on the underside of course. 

[Steel Penguin]

Malta shatter brown and yellow. 
my ever tasteful suggestion of berlin block 
all white a-la space 1999 eagle 

and a second vote for zenrats Chris Foss 

[steelpillow]

Dan Smith; British Secret projects 5: Britain's Space Shuttle, Crecy, 2016.
Truly a blast of a book, with enough material to keep the hypersonic whiffer going for more than one lifetime.

BAC pretty much stuck to white upper, black under for its conceptual art and models but never finalised the actual finish.
Protective thermal tiles were considered for the Rene-41 underside. While the bare metal seems to be described as black, could that be an oxide from weathering or annealing? Ablative coatings were also on the cards as a fallback, though horribly messy. ISTR they tended to be grey, though some modern ones are rust-coloured. The top might or might not have been painted white.
Probably, the two boosters would have been finished in less hi-tech thermal clothing than the orbiter. Say, bare charcoal-grey metal under for the boosters, tiles in colour of choice for the orbiter as none had yet been properly developed - maybe assume Shuttle black as the timing would not have been that far off, but some ablative grey on the hot-spots (nose and outer leading edges) that the as-yet not perfected tiles could not wholly protect. Top side of orbiter painted high-reflectivity white to improve thermal insulation, top sides of boosters painted in garish promo liveries as they are the ones seen on lift-off.
Or...

[Mossie]

... Mustard!

[jcf]

The Mercury panels.
M.A.C. Process Specification 13214: Black Oxide Finish for High Emissivity for Model 133

https://www.scribd.com/document/49362587/Mercury-Capsule-No-16-Configuration-Specification-MA-8

[Mossie]

Chris Gibson mentions molybdenum disilicide coatings in BSP 4 as a coating for hypersonic flight. It's a semi metallic charcoal grey, used for heating elements, brake discs etc.
http://www.machdiamond.com/chambers.html

[Snowtrooper]

Based on the descriptions and "gut instinct" I'd go with a lighter shade of "gunmetal" (eg. Vallejo, instead of the very dark Tamiya) for underside and "steel" (darker than aluminium/silver) for uppers. YMMV.

[Weaver]

Medium Sea Grey over PRU Blue as it'd be the highest altitude PR aircraft ever............ 

B type roundels on the underside of course. 

No one would ever see the underside roundels: they'd be shielded at launch and burned off by the time it got low enough for anyone to see it after re-entry....

[Weaver]

Thanks Jon and Mossie: it looks like a very-nearly-black dark grey is indeed correct then. 

[PR19_Kit]

Medium Sea Grey over PRU Blue as it'd be the highest altitude PR aircraft ever............ 

B type roundels on the underside of course. 

No one would ever see the underside roundels: they'd be shielded at launch and burned off by the time it got low enough for anyone to see it after re-entry....

It's the thought (and RAF Regulations) that count though. 

[Weaver]

Dan Smith; British Secret projects 5: Britain's Space Shuttle, Crecy, 2016.
Truly a blast of a book, with enough material to keep the hypersonic whiffer going for more than one lifetime.

BAC pretty much stuck to white upper, black under for its conceptual art and models but never finalised the actual finish.
Protective thermal tiles were considered for the Rene-41 underside. While the bare metal seems to be described as black, could that be an oxide from weathering or annealing? Ablative coatings were also on the cards as a fallback, though horribly messy. ISTR they tended to be grey, though some modern ones are rust-coloured. The top might or might not have been painted white.
Probably, the two boosters would have been finished in less hi-tech thermal clothing than the orbiter. Say, bare charcoal-grey metal under for the boosters, tiles in colour of choice for the orbiter as none had yet been properly developed - maybe assume Shuttle black as the timing would not have been that far off, but some ablative grey on the hot-spots (nose and outer leading edges) that the as-yet not perfected tiles could not wholly protect. Top side of orbiter painted high-reflectivity white to improve thermal insulation, top sides of boosters painted in garish promo liveries as they are the ones seen on lift-off.
Or...

Some of the later X-15s had a white ablative coating, although IIRC it didn't work out too well. Maybe this is what insired BAC's all-white artwork?

[Weaver]

Medium Sea Grey over PRU Blue as it'd be the highest altitude PR aircraft ever............ 

B type roundels on the underside of course. 

No one would ever see the underside roundels: they'd be shielded at launch and burned off by the time it got low enough for anyone to see it after re-entry....

It's the thought (and RAF Regulations) that count though. 

But what about Ministry Of Space regulations? 

[NARSES2]

Based on the descriptions and "gut instinct" I'd go with a lighter shade of "gunmetal" (eg. Vallejo, instead of the very dark Tamiya) for underside and "steel" (darker than aluminium/silver) for uppers. YMMV.

Games workshop do some good metallic colours. Only problem is they change the names of them  I have to take a crib sheet with me when I replace any.