By Benjamin Wilkosz
Part 6, 12 March, 2007
- Terminal Velocity, part 1, 23 December, 2004
- Terminal Velocity, part 2, 16 February, 2005
- Terminal Velocity, part 3, 27 April, 2005
- Terminal Velocity, part 4, 1 March, 2006
- Terminal Velocity, part 5, 28 April, 2006
- Terminal Velocity, part 7, 9 October, 2007
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).
Second Avalon008 static Test
After the cancelled NLD24 I decided to conduct a second static test to proof the flight readiness of the Avalon008 Motor. The propellant was the same KNO3/Sorbital mixture (65/35) as with the first test. Only this time I added a few millilitre of sunflower oil to lower the viscosity of the propellant, thereby making it easier to cast en reducing the amount of trapped air. This way the total propellant mass was increased from 2.7kg to 2.8 kg. To shorten the tail of, different grain geometry was chosen. Since the run at NLD23 showed no signs of erosive burning at all, I decided to decrease the core diameter of the last 2 grains to 25mm. This test, all grains had a 25mm core. Both the first two grains were coated with black powder. After ignition, the motor started fast. As with the first run, the motor delivered a very stable Thrust. Because of an unknown reason (maybe the low start temperature), the motor burned for a longer time, delivering a lower Thrust of approximate 740N at full thrust and a total impulse of 2960N (Isp 112 sec). The thrust curve of the static test can be seen below. During this test we could see how the nozzles thought turned bright orange during the run, as seen on the (low res.) picture left. This time a Viton O-ring was used to seal the nozzle and above all expectations, the Viton O-ring survived the run without a scratch. The normal O-ring, used on the first test was partially molten and partially carbonised, but this O-ring could be reused without a problem!
Paintjob and Parachute System
At last! The Terminal Velocity got his final touch. The paintjob was done by my girlfriend Jolijn. And I have to say, it looks awesome! The rocket has a kind of stars and stripes look, with a beautiful gold colour wrapped around it and of course its name "Terminal Velocity" at its side.
To ensure a safe return of the rocket, I conducted a successful full scale test of the parachute system. For deployment of the parachutes I installed two Trax-Arts and one R-DAS. According to plan all the ejection work is should be done by the R-DAS. The first Trax-Art is a backup for the drogue chute, in case the R-DAS does not function or the ejection is not successful. The time is set at approximate 3 seconds after the calculated apogee. The second Trax-Art ignites a small charge, burning through a Kevlar cable, opening the main parachute bay (approximate 8 seconds after apogee). This ensures that the main chute is not deployed to early, since the rocket will reach an altitude over 2.3km. The R-DAS then ends the job by ejecting the main chute at 200m altitude.
Onboard camera
As an extra experiment I installed a wireless camera in the nosecone with a 800mW transmitter (see right). To ensure sufficient current for the receiver three parallel 9V batteries are installed. Tests showed that the module can work 10 minutes with this power supply. Still, the launch sequence should be executed as fast as possible, since there is no second chance. To maximize the range, I installed the receiver in a 0.7m dish aerial, focussing the signal on the antenna. The first test of the wireless system showed that the system is capable of sending a clear signal over 800meter... with the transmitter behind a house. To the left you can see the camera module, containing the camera, three battery connectors and the transmitter. To the right of the 800mW transmitter the original internal 10mW transmitter is shown.
Now I can only hope for a successful launch at NLD 26...
Benjamin Wilkosz
Next part: Terminal Velocity, Part 7, 9 October 2007