TU Delft students improve rocket

After a tense day waiting for the wind to turn in the right direction the Stratos II+ rocket was finally launched from a launch base on the south coast of Spain October 16, 2016, at 16:33. The rocket, built by a team of students from the TU Delft, reached an altitude of 21,457 m. This achievement smashed their own European student record of 12.5 km.

The rocket had three experiments on board and was developed and built in its entirety by the students, including the most important part: the ‘hybrid’ rocket engine. The fuel core consisted of a mixture of aluminium powder, candle wax and sorbitol (also used as a sweetener), through which nitrous oxide is blown under high pressure. Following the successful launch of the rocket, the students can focus their attention on their next and ultimate goal: to become the first student team to launch a rocket that reaches the edge of space (100 km).

Altitude record

The students launched Stratos I in 2009. This predecessor to the current rocket reached an altitude of 12.5 km, a European altitude record for amateur rockets at the time. An attempt to break that record was made in October 2014 using Stratos II, but it was unsuccessful. One of the safety systems, the Flight Abort System, failed and a leaking oxidation tank also put an end to hopes of a successful launch at the last minute. “Fortunately, this gave us time to carry out extra tests and make improvements where necessary,” said Project Manager Jeroen Wink of DARE.

Improvements

The rocket underwent a number of significant improvements since 2014. The Flight Abort System was completely redesigned to ensure that the flight would not be unnecessarily aborted. The component that leaked was also been improved. “We also improved the rocket's ergonomics, which makes it much easier to replace components. Last time we had the same problem that you get with some modern cars – in order to replace a headlight, you sometimes have to take off the entire bumper. We had a similar situation with Stratos II, but now the components are much more accessible,” said Ralph Huijsman, a member of the team who is studying Aerospace Engineering.

Hybrid rocket engine

The rocket engine itself was also revised. The engine generates enough thrust to launch a small car, and was designed, built and tested by the students themselves. The rocket engine was ignited four times this year in a TNO bunker in Rijswijk, while anchored to the ground. The engine type is a hybrid: a cross between a solid-fuel and a liquid-fuel rocket. “The noise of the engine is overpowering,” said Jeroen Wink. “It is fantastic to see your own rocket actually fly.”

Laughing gas, candle wax and coffee sweeteners

Stratos II+’s hybrid rocket engine has a combustion chamber with solid fuel into which an oxidiser (nitrous oxide, also called laughing gas) is injected. For the engine’s propellant, the students used an unusual fuel combination of ingredients also found in coffee sweeteners and candle wax. When combined with the nitrous oxide, this composition delivers efficient propulsion. The rocket travelled at 2,545 km/h, about twice the speed of sound.

Experiments

Stratos II+ carried three experiments on board. The most important was a radio astronomy experiment from Radboud University measuring how far radio waves from space penetrate into Earth's atmosphere. Another onboard experiment belonged to the Dutch company Xsens and was used to measure position and speed without GPS. This experiment made it possible to determine the altitude of the flight. Finally, the rocket was carrying a technical experiment for transmitting live images from the rocket to the ground.