I'm in (very) preliminary discussions with a couple of manufacturers about a replacement for both Rapiers and old Jetex-type motors. I've made my own views known, telling the guys not to stray too far from the Jetex/50 Rapier L-2 specification. Good QA/QC and CE certification de rigeur. 150 mN 20 sec or so, weight no more than 12-15 grams, dimensions no more than a Jetex 50.
This makes sense to me - but what do you other jet jockies think?
Sounds fair to me, I'd be happy with 15 to 20 seconds and not exceeding 200mN. Beggars can't be choosers, I'd just like to know what size / scale to build in. The Germans make very good rockets you know. One nearly had my Grandads name on it. He was in a corrugated iron latrine when a V2 accelerated his motion! He was dug out and hosed down, all true but meant in a humorous sort of way.
Perhaps a miniature Walter rocket with HTP and potassium permanganate. Can you imagine our apparel when igniting, it would look like an orgy for leather perverts.
The prestigious German manufacturer is are looking at a 'one shot' low thrust long burn motor, using the same casing as their smallest A-6 motor to save on the retooling necessary if they were starting from scratch. The A6 is rather larger and than a Rapier L-2, having about the same the diameter (conveniently) of a Jetex 50 and about as long as a Rapier L-3, but they think its case can be shortened on the assembly line without too much trouble, and my suggested specification of 150-175 mN for 20 sec for a weight no more than 15 grams, is achievable.
They are looking at several propellant formulations, AP, KP for starters, but also, interestingly, ones containing Guanidine Nitrate. GN would be great, but is expensive and costs are a large factor here. Being German, they take testing, quality control and certification very seriously indeed, and distribution of their product will be through normal commercial outlets. We are, I would emphasise, at an early stage of consultation and product development, so it would be foolish to get too excited. We will just have to 'wait and see'.
Looking back through this thread I noticed that one of the commercial uses for Guanadine Nitrate is in car airbags. GN is one of several gas generating mixtures used. Such air bags of course must be inflated very rapidly but clearly GN can be persuaded to generate its gas output relatively slowly. Interestingly, the airbag system must be reliable with a long storage life and be triggered electrically. It would be very interesting to see how the chemicals are packaged to maintain themselves ready over a long period.
Naturally, I defer to the chemists among our throng to say if any of these chemicals might be worth considering.
But, good as the Rapiers are, I can't help but think a refillable steel motor like the Jetex that we cut our teeth on might do better. Is there a compound out there waiting to be pelleted and used in our favorite motor?