Part 7, 2 January, 2006
By Mark Uitendaal and Leon Krancher
- Spectre II, part 1, 30 June, 2004
- Spectre II, part 2, 7 July, 2004
- Spectre II, part 3, 22 October, 2004
- Spectre II, part 4, 13 January, 2005
- Spectre II, part 5, 9 June, 2005
- Spectre II, part 6, 23 September, 2005
- Spectre II, part 8, 15 April, 2006
Disclaimer: all liability waved! The contents of this page is presented for informational purposes only. Do not try to recreate any experiments presented in this page. The NAVRO and the author of this article cannot assume responsibility for any use readers make of this information. In The Netherlands it is forbidden by law to own this type of propellant if you do not have an exemption of the "Wet Explosieven Civiel Gebruik" (WECG).
Testing and building in Koog aan de Zaan
To bad, no thrust curve yet! We ran into some problems with our casting tubing. The previous test was conducted with a cardboard tube specially designed to transport TL lighting. But, like always in rocketry, some delivery problems occurred. We searched for a replacement tube and found the casting tube for the 75mm RMS systems. The great advantage of this casting tubing is that it is broadly available in the Europe and the US. Fortunately our vendor Caveman Rocketry had these in stock so we could continue. Unfortunately these tube seems to be 1mm shorter in diameter, so some alterations in the design had been done. The grain and thus the whole motor has been elongated to maintain its klemmung. This alteration alters the thrust curve, and put some risk on the next test. We decided to do a static firing without measuring thrust to save our test bench in case it will go horribly wrong. This test will be performed in daylight so we can film the test and take pictures of it. This will boost the scientific value of this test dramatically with respect to the previous test. The casted grains where all within 1.5% of the desired mass!
The rocket is painted! With the new colour scheme we try to eliminate the sun glance reflected by the rocket. This has been done with a black stripe along the rocket body. The booster is also finished and will be painted orange. This is done to be clearly visible along its ballistic trajectory. Another advantage is that this paint can be applied with a spray canister, so it will save us a lot of effort.
PVC (which is the material of the casing) is very brittle in low temperatures. This tendency can result in an explosion instead of a properly working motor. It was very cold on the test site, and so we decided to store the motor in the heath of the car. Just prior to ignition, when everything was set up, the motor was quickly placed in position and was not allowed to cool down. After the ignition commando a small plop was heard and some smoke escaped the nozzle. A fraction of a second later the motor roared to life! After a good and steady burn of about 3 seconds the effective burn was over and the smoke changed colour from white to grey. This is a clue that some of the grains are burned and the inhibitors are now burning. A perfect burn!
The video shows Bernoulli's law in action! Some of the residual smoke of the ignition is sucked into the fast flowing exhaust jet! Science in progress!
We are now ready for the full instrumented test. We are going to test the motor in its original faring. In this way we can also determine if the thermal loads on the structure are within the material specs. We expect a total impulse of ± 2KNs.
Next part: Spectre II, part 8, 15 April, 2006