” I have recently worked on what I thought was a novel design for a hybrid engine, and obtained a provisional patent for the concept. Unfortunately, others had had the same idea earlier, so with or without patent, it is not novel.

The concept may be of interest to you, if you have not already investigated it. Basically, it is designed to increase the power of a hybrid rocket engine. The regression rate of a hybrid is usually limited by the rate of mixing the liquid oxidizer and solid fuel. My provisional patent described a method of increasing the oxidizer/fuel mix rate.

The concept is augmentation of the solid fuel, typically HTPB, with a crystalline oxidizer, ammonium perchlorate for example. Typical ratios would be 75% HTPB to 25% perchlorate. Ferric oxide or other additives might also be included in the formulation. This ratio would not burn without the added flow of liquid oxidizer, and would be extinguished by termination of the liquid flow. Burn rate could be over 300% over that for a 100% HTPB fuel grain.

Thus, for a very small increase in risk during manufacturing and handling, a significant increase in burn rate could be achieved. Reduction of oxidizer flow rate is also a possibility.”

The idea was originally investigated, as far as I know, by engineers at Thiokol, Huntsville.

I wonder if this option has been explored.

If they are testing the full scale SS2 motor I hope they release video or photos soon anyhow.

As for the construction of SS2 we all saw that video they released of it being 40% done back when they unveiled the design of WK2 and SS2. Then reading the press release Scaled made about the accident they indicated that they’d be moving from a plastic liner (on their oxidizer tank) to a metal one (given that certain plastics burn quite well in an oxidizer rich environment). So I’m guessing that they had to disassemble SS2 to remove that tank (and I’m not sure that they designed it to be removed). The SS1 tank was bonded to the inside of the fuselage, all the way around, with an elastomeric compound so it wasn’t a permanent epoxy bond but still??? Just curious if they had to do some serious hacking to remove the tank or even start from scratch if it’s not removable.