Re: Steam Engine Prize

Most interesting that Xcor will supply you with 500psi steam (presumably saturated), air, or N2. If their goal was for a lightweight steam engine, one might think that operating on steam would be required. Designing for the thermal expansion and lubrication under heat would be important considerations, and the addition of steam-specific items like cylinder cocks would go against the 10 kg/5 kg design weight limits.
On the other hand, an engine with a 1 hour operating life (10 min between overhauls) might not need much lube. Dump in a bunch of graphite and let it go at that.