If the prize were $500 for a static test I would try for it with the current Laramie Rose monopropellant engine. I calculated that if we turn down the chamber pressure until the throat is just barely choked then we would see 60 lbf with the current nozzle, and 130 lbf with a properly expanded nozzle. Even if the actual difference is only half that it should be measurable.

The purpose of the boot is to persuade the exhaust to detach from one side in a very smooth predictable manner. Normal overexpanded nozzles can suffer from irregular separations that are potentially damaging. It is not the goal to entrain the air, just have it push the exhaust against one expansion wall in an altitude scheduled manner, exactly like a linear aerospike in operation. The air just has to take a detour on the way.

When there is no separation, overexpansion costs thrust on the ground when you really need it. If we can get a 5% thrust increase, payload benefits can be a multiple of that percentage.

I finally worked out a means of demonstrating the concept with compressed air. Hopefully in a week or so I will be able to test and then youtube a dynamic demonstration. (in the sense that it will be moving) The yarn tuft methods of aircraft should provide a good indication of the nozzle operation. If that part goes well, then an instrumented hot fire contest is in order with a few bucks to make it interesting

Looking back at your original article on “Notchbell and the Boot Compensators”, it seems that you are trying to actively force ambient air into the nozzle in a direction which is against the exhaust gasses. While you might succeed in slightly increasing the pressure along one side of the nozzle, you could possibly be introducing more instabilities into the flow where the two streams meet. Not only that, but in redirecting the ambient air, you are effectively reversing its momentum just to push it into a nozzle where the exhaust gasses will have to turn it around again. It seems to me that you will be suffering losses at both turns. Is the increase in performance really going to be enough to offset the increase in drag that would result from redirecting the ambient air against the direction it naturally wants to flow?

It would appear to me that the thrust augmented nozzle concept is probably one of the best ways to mitigate the low pressure regions in the over expanded nozzle. At least in that case, the gasses introduced into the nozzle are heading in the right direction and are adding energy and momentum to the exhaust rather than contributing further to aerodynamic losses.

I also remember now that several rocket engines, which I’ve seen on display, have the exhaust from their turbo-pumps redirected into their nozzles. In light of this discussion, I can begin to see some additional advantages that might be obtained from this.

Of course this is mostly speculation on my part. I should stop doing CFD in my head and actually do a few runs to see what would really happen. I’ll let you know if I ever get “a round tuit”.

I think if anyone was really interested I could think of a few thesis subjects. From where I sit, it is hard to picture the difficulty of finding interesting problems. If a very few bucks would move things along, it would be interesting to work something out.

There may be a credential problem in me making the thesis suggestions though, I don’t have any. I might be the only one here that actually did drop out of elementary school.

I don’t know what a sponsored study would cost but I think a modest amount of funds could be useful and welcome as an additional incentive if the hardware costs aren’t too high. Jonathan Goff and others around here would know much better than me. It was merely meant as a suggestion and possibility but for example the concept we’ve been talking about here (or very closely related ones) seems like it should be interesting to anyone doing research and papers on fluid dynamics (and finding a thesis subject can be difficult).

It seems to me that a joint project might be beyond the time frames that interest me. If I can make this one attractive, many teams are able to fabricate and test it in a single weekend. This particular concept has the single strength that it can be validated or busted without changing the core hardware at all.

I give this one less than 10% chance of working right on the first set of tries. I would put several other concepts much higher in probability though equally higher in time and material costs. A fast turnaround at minimum cost is my priority.

How much would a sponsored acedemic study cost? For something as complex as the ejector/injector, it might be worth looking into.

About small prizes (like for example the N-Prize which is small in most ways) and so on I wanted to air the idea that some of the concepts might be better off as joint projects (smaller than the Sugar Shot 2 Space project) or sponsored academic study (i.e. offer to sponsor them for engineers looking for thesis material).

Jsuros,
If a few of the ideas pan out and add value to the industry, then that would be a good idea. People moving forward in this business would probably find it worthwhile to contribute.

At this time though, I wouldn’t put my credibility high enough to ask others to send contributions my way. On the gripping hand, if there is an idea that somebody thinks feasible and useful, there is no reason they can’t add a few bucks to the jackpot to be sent directly to the winner(s). If somebody wants to do that, they can suggest the format and concept for me to follow.