>The big question is: why hasn't he been able to convince investors to fund
>his approach? What are their reasons for skepticism?
Good question. For one, investor and public ignorance. As I mentioned, people generally believe that some new technology is needed. There is nothing wrong with new tech, it just takes time and money to develop. Another reason, Bob is getting on in years. More importantly, his booster ideas are in the same boat with every other commercial space launch project, that is, competing for the same small private funding pie. Investors don't understand the technical side so well. That's where a master fund raiser such as Gary Hudson shines.
Note for the record that Bob's small rocket ideas did get privately funded to the tune of several million built, and static fired many times. The Navy bought that project, called it SEALAR, and spent $20-30 million on Bob's little rockets. We dropped rockets in the ocean from helicopters. We fired a dozen different engine designs. We had a warehouse full of surplus Thor missile motors, even full missiles (this was a liquid fueled intermediate range ballistic missile, rather large). The SEALAR test vehicle was finished to the point of being fully integrated with guidance, telemetry, ground station, recovery system, motors, tanks, sea launch ballast, etc., and ready for the last few tests before launch. That's when the Navy cancelled the project. The Naval Research Laboratory (our customer) wanted the project to continue, as did congress (allocating more funding than was asked for), but not the Navy brass. A political problem, not a technological one.
It seems that it is easy to scare up a few million for a rocket project, and a few outstanding efforts have produced $50 million or so (ARC technologies/ Starstruck/ AMROC, for example). That's enough to fly one, but not to finish the job.
One reason for the difficulty in getting funding is that until recently there was no definite market for launch services except to the US government. Low orbit communication networks have changed that. We could see one of these projects succeed in the next few years.
Here's another company working on low cost launch vehicles, but which keeps a lower profile than Rotary Rocket co.: www.aeroastro.com/industry/aeroastro/home.html These folks are building very Truax-style boosters. I give them a better chance than the Roton. Pressure fed, composite tanks, ablatively cooled thrust chambers, two stage to orbit. Very tasty.