By Mark Uitendaal and Leon Krancher
- Quick and Dirty, part 2, Mark Uitendaal and Leon Kranchers rocket project page.
Dordrecht, 4 March, 2007 - Finally a test day! On 4 March we completed the instrumented tests of the booster and upper stage motors of the Quick and Dirty, project. These motors are considerably different from our previous motors, since the casing is constructed of glass fibre reinforced plastic. Both motors were tested on our analogue static test bench at the club house of the Scouting club "Van Speijk".
This construction method saves a lot of weight! The burnout weight of the booster motor is almost half of the burnout weight of our previous booster motor of the Spectre IIb and has more than 15% more impulse! The sustainer motor of the upper stage is not optimized and therefore the total impulse and the burnout-weight are in the same order of magnitude as its previous PVC counterpart. This is not a problem because of altitude restrictions.
The booster motor is specially designed to produce a neutral thrust during a relative long duration (±3.5 sec). Also the start up time of this motor is kept extremely short, because half of the grains are painted with rapid ignition primer on their complete burning-surface.
The booster motor was closed with a plastic cap in the nozzle, which keeps the motor free of the moisture of the open air. This cap also provides support for the igniter when the motor is "nozzle down" in the rocket. The thrust-up of this motor was fairly good, as can be seen in the thrust-diagram. The thrust itself behaved as predicted: slightly regressive.
When the motor was silent again, the nozzle was so hot that it melted its way down into the soft thermal-liner. This is a strange sight, since it looks like the motor is equipped with some sort of thrust-vectoring, but it isn't (sadly).
After the burn, the motor produced some unintended smoke because of the melting and burning of the O-rings in the nozzle. This is nothing to worry about, since this happens only after the motor is burned out. But this could become a problem with motors with longer burn time.
The sustainer motor is a 580 Ns motor with tracking smoke, basically a slimmed down version of the upper stage motor of the Spectre IIb. The motor is just for this project and is not intended to be developed further. Probably there will be some development in this diameter, but this will be a motor in a higher impulse class, but this was for this project not feasible due to altitude and time restrictions.
The motors performed as predicted. All results are within 5% of the simulations. Both motor casings had no leakage.
(This text is a fragment from Quick and Dirty, part 2.)