The basic idea of the project was to finally fly a 6DOF motion sensor, originally developed for another project by Per Lundberg and myself. This sensor would require the entire electronics package of Muren to be replaced. Also, a new motor was needed for the rocket. Micrograin motors are known for their high thrust and short burns, but as the intention of flying a 6DOF sensor was to measure the rockets cross wind sensitivity, a motor with moderate thrust and a fairly long burn was prefered. This led to the development of a composite motor with a 3.8s burn duration.

The motor was based on an aluminum casing designed by Niels Andreassen with a four segment bates grain propellant configuration. Actually, the motor was designed for one more propellant segment, but in order to better fit within the requirements at ASK, the fifth segment was replaced with a dummy. Below, fellow DARK members Dennis Mikkelsen, Niels Andreassen and Henrik Nissen are preparing for test.

The static tests vent well, and also a final pressure test of the casing. This meant go ahead for manufacturing the remaining mechanical parts of the rocket.

Then came the final hectic phase of assembling and calibrating the electronics, writing software and testing. A major bug in the flight computer software was discovered and corrected, and after all, the many hours of testing was rewarded with a full working system.

Well arrived at the ASK preparations for the launch took place after breakfast June 10'th. The final preparations went smooth, and took only about 30 minutes. On the picture below, Henrik Nissen and me are attaching the motor to the payload section of the rocket.

... Well, that's me, posing with the rocket.

Finally, the rocket has been placed in the launch tower, ready to launch - well not yet: suddenly there was a jeep driving around in the middle of the launching area, and we just had to wait until it had gone.

The 3.8 sec. burn duration made the launch quite impressive. Muren made its way to a 2500m altitude, where it deployed its parachute. Since the total descent time had to be less than 120 sec., a small parachute giving a descent speed of 22m/s was chosen. This is twice as much as originally intended, but surprisingly the rocket was almost intact after impact. Only the nosecone and one of the fins were slightly damaged.

Documentation for later use - the landing spot is marked as waypoint on my GPS receiver.

The launching campaign was a great success. A total of 15 rockets built by clubs in three different european countries was launched during a two day event. Fellow DARK members Peder Cabion Hansen and Niels Andreassen wrote DARK history by launching the SmallTom2 rocket, that transmitted the very first onboard video (and sound) from a DARK rocket. Also many thanks goes to the hosts of the campaign - the Ducth organization NERO, that marked their 40 years celebration with a couple of noticeable launches. On the picture below, Frans den Boer of NERO untangles the parachute lines of the H8 rocket, that successfully carried a canard control experiment for measuring the dynamic characteristics of the rocket.

Results from the flight:

The flight computer onboard Muren made the most comprehensive flight recording of any DARK rocket to date. Investigation of the data will go on for quite a while. Sample data of acceleration, pressure and rotational movements are presented below.

Measurements of the atmospheric pressure reveals a pressure drop corresponding to a peak altitude of approximately 2530m - slightly better than the expected 2400m. However, the pre timed parachute release just after apogee was perfect. Also the parachute decent speed may be calculated to 22.2m/s - pretty close to the expected 22m/s.

Acceleration data reveals, that the motor is performing as expected. Also the air drag is very close to the estimated value.

Pitch and Yaw angular velocities. Note, that the environment gets quieter after burnout.