Richard Tenney wrote:
An amateur rocket friend of mine was telling me yesterday at lunch that Rutan's rocket ran on recycled tire rubber and laughing gas! Doesn't sound too exotic or expensive to me, but I'm sure he was oversimplifying it just a bit.
He was not kidding (except maybe for the part about the recycled rubber tires). On some scale the SS1 engine is complicated but certainly not when compared to the engines being used on shuttle, Arianne and H-IIA.
From the Scaled Composites web site FAQ:
***** What's the deal with laughing gas and rubber? All rocket motors have some form of "fuel" and an "oxidizer". In solid rocket motors the oxidizer is embedded into the fuel (like an Estes rocket motor) and when lighted will burn until depleted. In liquid rockets the oxidizer is usually liquid oxygen and the fuel another liquid like hydrogen or kerosene. In our hybrid motor we use Nitrous Oxide (N2O or laughing gas) as an oxidizer and hydroxy-terminated polybutadiene (HTPB or rubber) as the fuel. Both of these can be safely stored without special precautions and will not react when put together. Finally N2O has the nice quality of self-pressurizing when at room temperature so that the space ship doesn't need complicated turbo pumps or plumbing to move the oxidizer into the combustion chamber. ***** Patrick