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Home / Features / Alternate Propulsion
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Editorial by STEPHEN D. ROBERSON
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Saturday, May 01, 1999 |
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 ALL THE LATEST UPROAR over BATF involvement has got me (and no doubt many others) thinking about alternate forms of propulsion. Let's face it, no matter what the outcome of the NPRM that is coming, I think we are in for a dramatic increase in the cost of AP based rocket motors. Either licensing and regulations will drive up the prices, or many casual fliers will be driven from the hobby, which will also cause a price increase for those serious enough to stick with it. Postings on rec.models.rockets show that there is a lot of interest in 'making motors', which scares me, because the average Joe doesn't really know what they are getting into.
I think that the thing to remember is that there really is no reason to reinvent the wheel. NASA, JPL, and the military have been doing rocket science for many decades. Most of this data is available for us to look over and pick out the best technologies to keep our hobby growing and out of trouble. However, the majority of us will still be dependent on the manufacturers to supply us with something. I call upon all motor manufacturers to start work now on legal propulsion that will be as neat and easy as the current crop of reloadable motors.
Just to promote discussion, I'd like to pass on a few comments on techniques that are currently being worked on, or that I've read about in various places.
Nitrous Oxide: The obvious front runner, since it is already on the market. Hypertek is to be commended for a fine AP-free product and I hope they continue to improve it and create both smaller and larger versions of their motor. Maybe they should license the design to Dr. Rocket? Aerotech needs to get with the program here and give up their pyro-based nitrous motors.
Ammonium Nitrate: I've seen several of these successfully test flown. Though they have a lower impulse than AP motors, there is a great potential here for new products. I'd like to see some reload kits that fit existing cases, and disposable E-F-G motors based on AN. With fertilizer so readily available I find it hard to believe the ATF will get involved with this substance.
Peroxide & gasoline: We've all seen the ads for the liquid fueled rocket from System Solaire, which may be the first one available to the hobby. Seems a bit expensive. I have not yet seen one in the flesh, or flown, but it is intriguing. I wonder if there is a way to increase the thrust and burn rate on this reaction, to loft a heavier rocket to lower altitudes. How well does this technology scale up? Time will tell.
"Traditional" Amateur: These are the venerable zinc & sulfur and sugar based propellants, including Homer Hickam's "Zinc-o-shine". Much work has already been done here. With a proper design program and modern manufacturing techniques, there is no reason these motors cannot be certified and sold just like other motors.
Smokeless rifle powder: I tend to put this into the same category as pipe bombs and playing with fire. Definitely not the sort of thing you'd want to experiment with in your garage! But there are a wide variety of powders available, and in the right binder one of them might make a respectable propellant. The ATF would probably not look kindly on this sort of thing.
Black Powder: We all know the old saying "Fly and Die with FSI!" Deserved or not, BP motors have well documented problems with scaling up. There may be a solution to this, but even industry expert Estes could not get a motor bigger than a D to work reliably.
Water rockets: Now don't laugh! Some people have made some pretty sophisticated flights using only pop bottles. Think what this technology could do if carried to extreme. Imagine a scuba tank with the appropriate amount of pressure in it! Of course, the compressor that creates that pressure in the first place is very expensive, and takes a long time to fill the bottles. Also, the release valve for such a beast is liable to be complex and potentially dangerous.
Chemical reaction: When I was a kid, I had a neat little rocket that would fly a dozen feet into the air with just a little baking soda and vinegar. Surly there are more potent reactions out there that do not involve flame in any way. Obviously the impulse of these would be low and the flights "just for fun" but it might be worth looking at.
So you see, there is still a lot of room to maneuver here. Just because AP becomes hard to get does not mean we are shut down! We have to let the manufacturers know that there will be a market for rocket motors no matter what form they take. Perhaps the demise of AP would open new doors that we cannot imagine. Give us those whoosh generators and we will fly them!
Stephen D. Roberson is the creator of WINROC simulation software and a frequent flying high power rocketeer from the Mesa, Arizona area. You may reach him by email at
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