Ariane 5 1/96, pt. 15 - the EAPs

Étage d'Acceleration à Poudre. Acceleration stage on powder. How poetic a name for just a long stove pipe that acts like a giant Roman candle. But that is what I have started working on now.

Eventually, I just cut out the hull, rolled it into a small tube and put it aside to more or less set. But as usual when I am working on a model I started to notice incorrect parts and shapes. So I needed to redo them.
More on that after the jump.

Now, there are about four free models of the Ariane 5 to be found on the web, two of which are decent, the other two are just kid's stuff, very simple and no detail at all. The two good ones are both based on one single model, Ton Noteboom's variant. And that is a decent looking Ariane. For the layman, that is. The other is found on Alfonso's AXM paper models site and it is a slightly improved version of Ton Noteboom's model made by David Brown but he initially fell for the same mistakes as Ton did. The flags on the boosters had errors, the CNES logo was just a very rudimentary attempt to look like the official logo and the ESA logo was a bit low in resolution which also could use some improvement. Besides, the boosters aren't white. They are a creamy off-white. And since I wanted them to be correct, I already had done a recolouring and replaced the logos for better ones. But then, when I was building the first booster I noticed some more significant errors. Easy to solve, but errors nonetheless.

Start of the first attempt. Nice shape, nice fit. But.

A detail of the lower section of the EAP. Note the big ring around the booster where the struts are. Note the single gas bottle. Note the line structure at the bottom inside of the booster. Note the inward curving ring below the skirt. Enough to reconsider redoing the whole EAP. If the rest is detailed, why then not these? 
Photo © ESA

One of the most obvious were the 'hips' on the EAP where it attaches to the bottom of the core stage. It is a very noticeable thickening ring shape about three quarters down on the hull, where the attachment struts are located. Further, the ECA version of the Ariane 5, the improved one they use since the early 2000's,  had their EAP's redesigned. There were less seams on the hull and they were simplified, the lower part just above the engine skirt got a kind of protective heat shielding, the two compressed gas bottles at the sides were replaced by just one bottle per rocket, and the upper connection to the core stage was changed.So, as they say, to the drawing board. 

Some additional ideas: I want to keep the EAP's separable. So I need to design a way to attach them to the core and this will be how it must be done. It is very much like the real thing, actually. I have brass rods in mind for it. Drawing the model I am working on improves my understanding in how things have to come together and it also gives me time to get my head around the engineering questions I have building the thing. Having it all separable also means I cannot have it stand on its own so I am thinking about building Michael Knobloch's launch platform. It sure looks good and it might even give the model a little more realism.

Perhaps even a suggestion of the shape of the solid fuel in the booster. It is star-shaped for an optimal amount of power. It even is shaped differently at several heights inside the stove pipe so the thrust is optimal for every moment of the ascent. Clever people.

Of course, printing was a bit of a hassle again since I replaced the empty cartridges of my grumpy old Epson 9800 Deskjet A3 printer with non-brand refills. Mr bloody 9800 Deskjet didn't want to accept them and started to bother me with blinking lights. On, off, on, off, cartridges out, in, out, in, old cartridges in, out, new ones in, off, on, off on, test page, test page, printer sled starting to rattle when going to and fro, shredded test page, opening the hood, discovering a little metal wire under the colour cartridge being bent, bending it back, more of those blinking lights going on, off, on, off, etc. etc. etc. Aarrrgh.

But then, out of the blue, after I just left the grumpy bugger alone to let it think about its behaviour and after I had some coffee, it suddenly all was okay. No more blinking, no more rattles, and a good test page. I didn't even had to use my fists. Nice. So I loaded some semi-gloss photo paper and pressed CMD-P. And the result:

Less segment lines over the hull, smaller CNES logo, heat shield structure. White line just above it indicates where the "hips" must be. I also removed the very prominent lines where the twin-bottled gas unit would go.

Close view of the right part of the EAP heat shield structure. At least, that's what I think it is. 
Correct me if I'm wrong. No, seriously. Please do.

Additionally, I also redesigned the shroud. I already had the Herschel/Planck logo and all the other slogans on one side of the shroud but I discovered the side turned away from view, facing the launch structure also had the logos. So copy-paste and voilà. And yes,  even though the Arianespace logo is without any visible borders, the mission logos are on meticulously white backgrounds on the off-white shroud. It looks a bit tacky and clumsily photoshopped on the model but that is actually the way it is. I presume the Arianespace logo is sprayed on in the factory like it is on every shroud and the mission logos are added in a later stage.

So now it's back to the cutting mat and back to work.