Night of Nozzleless Rockets - Nozzleless 7:3:1 BP Rockets

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Date: 2006-01-16


Four nozzleless blackpowder motors. Two on Steve Majdali's SBR tooling, two on Rich Wolter tooling.

Based on the results of the burn rate and flight experiments it was believed that Commercial 7:3:1 propellant would probably CATO on SBR tooling with a nozzle and be borderline on Wolter's tooling, but should operate correctly on both nozzleless. This experiment was all about proving the growing analytical model of these motors is valid, at least as a rule of thumb.

The two motors on Wolter tooling were almost identical, with the exception that one had two increments of Salicylate Whistle pressed above its core, the other just continued with 7:3:1. Both had just paper wadding plugging the end of the tube, no clay in the device at all.

The two SBR motors were very different though. One used the standard NEPT tube for the SBR toolset, charged as usual with a clay bulkhead plug. The other was charged into a Pyrotube 50 mm long casing. The 50 mm long tube is *just* long enough for one increment of propellant over the core. This configuration is known to be unstable and a CATO risk, but it was assumed that pressure would be lower in the nozzleless mode and perhaps allow successful operation. A small amount of clay was rammed into the remaining space sealing the top as an extra measure.

All rockets had identical sticks, hot-melt glued to the case and fused with blackmatch, folded over the last 5 mm and pushed all the way up the core.


All worked well.

The nozzleless motors are quieter and a little slower than the more conventional versions. However they seem to achieve similar apogees. Future static thrust testing will determine their payload lifting capacity.

The tail seems a little better on these rockets too, but as the propellant has never been flight tested before this might be a property of it, rather than the nozzleless configuration, especially after comparison with the previous nozzleless SBR videos which used different charcoal and much more oxidiser by mass.

The SBR versions definately take off faster and fly higher, but they burn out quite quickly. There is simply less end-burning region in them. To get good timing for payloads it might be necessary to use slower composition above the core.


title type size
Wolter Tooling Video video/x-msvideo 1.296 Mbytes
Wolter Tooling with Whistle Delay Video video/x-msvideo 2.200 Mbytes
SBR Tooling with NEPT Tube Video video/x-msvideo 1.305 Mbytes
SBR Tooling with Pyrotube Video video/x-msvideo 951.458 kbytes
Pre-Test Picture image/jpeg 41.648 kbytes