On Thursday, 6 September 2018 01:29:45 UTC+10, wrote:
There is only one pump which requires a certain minimum voltage to start but then produces too much flow rate into the igniter resulting in excess fuel.

I'm glad you mention the pump.....

Thanks for that. Good information on break in of the pump.

As for close clearances just contemplate the clearances in the crankshaft and bearings of a two stroke or the clearances in the cylinders. BTW your piston engine ought to melt. The fuel burns hotter than the melting point of the metal but there is a boundary layer in the gases at the surface of the metal.

The origins of the M&D engine mentioned are in accordance with what I was told by someone who ought to know.
Last time I looked the certification on jets for sustainer use was that it wasn't allowed to blow up or catch fire. M&D seem to handle the blow up bit by limiting the number of cycles before overhaul. HpH in the Sharkjet went the ballistic shielding route.
The turbine blade of a Titan weighs about the same and moves at the same speed as a standard velocity 0.22 rifle bullet. It was fun doing ballistic shielding tests. 1 mm of 4130 dents but does not break. 8 layers of 170 gm Kevlar catches the bullet. Interesting.