By Hein Olthof (only uploaded by Frank)

On Friday, May 13th 2011, the solid propulsion group reached a great milestone at ASK ‘t Harde: the first rocket powered by an ammonium nitrate rocket propellant was successfully launched. After a year of thorough theoretical studies and testing, it is now proved that the newly designed ALAN-7 propellant has the potential to reach its most important requirement: delivering enough thrust to lift a rocket out of the launch tower.

After some initial burn tests under atmospheric conditions, the solid propulsion group was confident that the ALAN-7 propellant had all the necessary characteristics to be used in a rocket motor. To prove this, a test motor was designed and built.

The very simple motor consists of an aluminum casing and a steel nozzle and endcap. All parts are connected together with threading, for easy loading and assembly. The motor casing is shielded from the heat of combustion by an ablative liner. It houses four propellant grains, which form a bates-grain configuration (circular propellant blocks with a circular port in the middle). It weighs approximately 500 grams and contains 112 grams of propellant.

The motor was tested two times on the ground and from these tests, a thrust curve was deduced. This curve shows that the performance of the motor is beyond expectations: it reached a specific impulse of 191 seconds, a little above the 185 seconds which we aimed for. Unfortunately, the heat shielding during the first test, which was made of cardboard, proved to be insufficient to protect the casing from the heat of combustion. The motor casing got hot and its crystal structure changed. Due to the cheap type of aluminum that was used, this lead to weakening of the structure, so that it failed spectacularly during the second test. A lesson was learned and a new, thicker liner was produced of PVC to provide better shielding.

We decided that it was worth the risk of building a rocket around this motor and fly it on the next launch day as an ultimate technology demonstrator, proving that it could launch a rocket. A lightweight body tube, made of glass fiber composite material was produced. To this tube, four fins and a nosecone were added, as well as two bulkheads, made of aluminum. No recovery mechanism was used, but the rocket was designed such that the upper part of the body tube would act as a crash barrier, protecting the motor for too much damage. We painted the rocket with a fluorescent orange color and called it Fulgor (lightning flash), after the bright orange flame that the motor produces and later the Flaming Tiger, because of the pattern of stripes that was found on the body tube after curing. The rocket was only 74 centimeters long and weighed 300 grams, motor excluded.

The motor was prepared for launch and fitted inside the rocket on the day prior to the launch day. Because of the highly experimental nature of the launch, the Flaming Tiger was scheduled for the last launch window of the day, right after the Stratos Concept Launcher. Finally, the tiny rocket was placed in the tower and connected to the ignition wires. After the relief of the successful launch of the Concept Launcher, the adrenaline started pumping again: would we have another casing failure? Or would the propellant fail to ignite? All these possibilities crossed our minds. But finally, the red button was pushed and after some hesitation, the rocket leapt off the pad with a roar and a bright trail of sparks! The motor thrusted for three seconds, accelerating the rocket straight into the clear blue sky. When the rocket reached its apogee of 750 meters, the rocket was barely visible. It turned over plummeted towards the ground at terminal velocity, as planned, with a whistling sound. It impacted very close to the launch tower. A recovery group of military personnel was dispatched to try and find the remains of the rocket back. However they did not find a trace and assumed that the rocket was buried deep in the ground. However, after some searching by team members, the rocket was found only 25 meters from the tower. Its front end was completely shredded, but the important back part, containing the motor was still intact! This was a 100% mission success!

With a great feeling of happiness, we accepted congratulations of the fellow rocketeers and shared some cigars in good DARE tradition. Now, we are ready to scale things up and make bigger, better rockets powered by ALAN-7.