Hello,
I am developing a new hybrid propellant concept that I would like to discuss...It's basically very similar to any hybrid, except that the propellant consists of a cylindrical grain of lightly bonded magnesium powder onto which is sprayed through injectors the oxidizer. The oxidizer is a solution of water and various nitrates and perchlorates at high concentrations. There are many possibilities for testing and would like to get people together to explore the concept.
I have placed a brief description on the Australian Experimental web site, which I will update with any developments made.
The motor is a concept at this stage, but tests of the reactivity of lightly bonded magnesium powder and water / oxidizer solutions indicate a highly energetic reaction that with a little luck will produce a workable hybrid propellant.
Any and all ideas and help is welcome...I think it's an interesting idea worth some investigation...
I see "lightly bonded" as a red flag on this -- if the stuff is bonded lightly, I see a serious possibility of cracking or shedding of the fuel grain, which could lead to significant pressure excursions from the change in burning area or from nozzle restriction. Neither is quite the issue with a hybrid that it would be with a conventional solid, but on top of that you have the traditional problems with metallic fuels, in that the primary combustion products are likely to be or become solid before the exhaust is beyond the nozzle; though the phase change gives up heat to the remaining gas in the exhaust, it also reduces the amount of gas and in general is a net loss (not even to mention the nozzle erosion problems resulting from particle impacts at transonic speed).
Overall, I'd be interested in seeing static tests, but I'd also want to see tests where the motor is fired vertically in a test stand that simulates the vibration (and ideally acceleration) environment of rocket flight -- I'm inclined to believe there will be serious problems under flight conditions that might not show up on a solid test stand. Using water as an oxidizer (which it certainly is for magnesium, at least once combustion is established) sounds interesting (agueous solutions are much safer to handle than most liquid oxidizers), but I'd have to suggest a high solids percentage traditional composite over whatever "lightly bonded" might mean. I'd also suggest testing aluminum as a fuel in a similar motor, preferably milled and bonded in vacuum or nitrogen to prevent surface oxidation; a strong perchlorate solution should react nicely with aluminum, though the problem of solids in the exhaust remains.
Of course, there are significant handling hazards with both magnesium and aluminum as fine powders prior to bonding, especially if the powder is prepared in a manner that prevents oxide layer formation; both metals, when powdered, are pyrophoric and can also self-ignite if exposed to high humidity or actual liquid water. Both are nearly impossible to extinquish once ignited in air.
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