Hobby Boss Me163 Komet

[Mitch K]

I bought this at the same time I got my He 162. It suffers similar issues (no cockpit, thick trailing edges) but looks like it will be a fun build. In a momentary lapse, I didn't do a full "before" shot of the sprues, but with so few bits there isn't much to see anyway. Here's the cockpit as provided - not really what we want, is it?

 

The Me 163 is a classic design, its tailless airframe was ahead of its time and influenced a number of postwar types. The propulsion system, a bi-fuel rocket has become near-legendary as being lethally dangerous. Although there is some truth in this, the tale seems to have been inflated with time.

 

The Walter rocket motor in the Me 163 used two fuel components: one of these was a mixture of hydrazine in methanol. Both hydrazine and methanol are toxic and flammable, and hydrazine is both carcinogenic and given to explosive decomposition in the presence of a catalyst, but both are reasonably common laboratory reagents, and I've used both over the years without incident.

 

I kicked off the build by hacking out the floor from the upper fuselage to give me the right depth for the cockpit. I thinned out the sides of the cockpit too, to give some sense of the correct width.

The other fuel was high-test hydrogen peroxide. Most people are familiar with hydrogen peroxide, as a bleach, tooth whitener or disinfectant. About the strongest you can buy over the counter is "30 volume" which contains about 9% actual peroxide, and is gentle, pretty harmless stuff. High-test peroxide contains 70%+ and is a different beast altogether.

 

With my least favourite tool, the profile gauge, I made a rear bulkhead.

High-test peroxide will decompose to oxygen and water, which due to the amount of energy released, comes in the form of superheated steam. This reaction allows high-test peroxide to be used as a monopropellant rocket fuel, the steam and oxygen providing the driving impulse in what is called a "cold" motor - "cold" is a relative term! This was used extensively in RATO systems

 

The roof of the undercarriage bay and the cockpit floor are at the same level, so adding this gives me both in one go, along with the rear bulkhead.

If you introduce a fuel source (such as a solution of hydrazine in methanol) into the decomposing hydrogen peroxide stream, the heat generated in that decomposition is sufficient to light off that fuel without any separate ignition source (a hypergolic reaction), and the fuel burns ferociously in the oxygen present to give a tremendously powerful impulse.

 

The seat is scratch-build from metal foil of various thicknesses with wire buckles.

On landing, any residual fuel and oxidant can mix uncontrollably, resulting in a catastrophic explosion. Even in the absence of fuel, any residual peroxide can, and will, soak into organic materials and decompose, leaving them saturated with oxygen and prone to violent, spontaneous ignition. The fuel tanks were washed out carefully between fuellings, as the effects of putting the wrong fuel into a tank containing even a small residue of the other can be all too easily imagined.

 

Here's the headrest added from Kneadtite, along with the head and back armour. 

As I say, I've handled hydrazine a few times and that's been uneventful. However, I only ever used high-test peroxide on one project, long ago, and that was more than enough! My boss at the time referred to it as "tricky stuff". He reserved the term "tricky stuff" for such nasties as diazomethane, aflatoxins, chromic acid and chlorinated dioxins, putting it some very unpleasant company.

 

The instrument panel is a simple flat unit with a small central panel (which I think held the key flight instruments). This was scratched up and handpainted.

All that being said, the stories that if the fuel touched the pilot he would simply dissolve are just that - stories. Exposure would leave the pilot at risk of poisoning or severe burns, but not this latter dramatic effect.

 

Here's the seat painted up, plus rudder pedals, side consoles and the like. Time to button up the fuselage!

Post war, hypergolic liquid-fuelled rockets were still used, although the oxidant used later was often changed from high-test peroxide to red fuming nitric acid, which ironically probably WOULD dissolve a pilot if he were exposed!

[Chillidragon]

Yes, hazardous indeed that T-Stoff and C-Stoff.  Tankers carrying each were, of course, never used for anything else, and were not allowed onto the field at the same time.  Each and every piece of equipment was flushed after use, and pilots wore a Neoprene suit to protect them from the Peroxide - the tanks formed the cockpit walls!

 

The pilot wouldn't dissolve completely, but at that concentration his flesh would.  This I have seen and done, with a clinical solution (much lower concentration than the oxidant, but higher than that available over the counter) used for wound debridement. 

[Mitch K]

Following a large number of camera and computer disasters, I've lost a considerable number of pictures of this and other builds! This and others have also been slowed by the impact of "real life", but here's a shot of the 163 with the camouflage on. 

 

 

The decals are on and I'll get a shot or two of that, but the next job is to build a decent undercarriage. The wheeled dolly and tailwheel are fine, and the landing skid just needed a bit of hollowing out on the inner faces, but the support system provided by the kit are two slightly pyramidal "lumps" rather than the structure of rods and plates on the real thing. I've got a good supply of fine steel rod/tube which I'll use, but it's going to be a tricky sort of job, I fear.