Name of person interviewed: Dan Moser
Profession: Retired propulsion/test engineer / technical consultant
During this interview, we spoke primarily about ablation, silica phenolic, and the structuring of the supporting/gluing of the combustion chamber parts together, machining, starlite and just a lot of material science and what specifically makes carbon so good in ablative materials.
We began talking about the specifics of silica phenolic, which is a NASA grade material that ablates really well and can handle the pressures within the combustion chamber. It is incredibly good at dealing with super high heat flux situations but not so much at being a load bearing structure. So for our solution we would need to get a small section of glass epoxy into a ring around the throat which would be silica phenolic and it would all be bound together using a steel split ring and a high temperature PVT Sealant. Glass epoxy is essentially a kind of thermoset plastic that has glass fibers woven into it and cured in an epoxy binder, and as a note this is how silica phenolic is made albeit a little differently. There’s a whole science dedicated to thermosets, quite fun stuff.
To machine this one would have to wear a respirator and hook up a vacuum (not in a vacuum chamber, just a good ol’ shop vacuum) to the tool end and it sucks away all of the shavings and dust generated by the machining process. This stuff tends to get everywhere, wear out tools and is a pain to work with, luckily it survives fire pretty well and we won’t have to machine it very much, mostly lathe work.
Starlite was a material conceived in the late 90s by an English man named Maurice Ward who was noted to be very paranoid about his material and gained national notoriety when he set an egg in this material on television and the egg survived intact and uncooked. It was a rather unreal demo, it still blows me away. Essentially the material is amazing at dissipating heat and ablates by generating a Carbon foam that expands and physically pushes the flame towards the source of flame and slowly burns away the material. Thermosets tend to do this but in a less dramatic fashion. Starlite was rediscovered last year by a fellow and the materials are fairly accessible so I’ll make some next quarter for another project I have in mind. The nice thing about Carbon is that the foams it makes are extremely heat resistant and just incredibly good at dissipating heat both physically and by their nature and material properties.