Angst+Pfister is sharing its passion for advanced technology and engineering with the ambitious university students running the “Delft Aerospace Rocket Engineering” rocket project. The stars of Angst+Pfister’s sponsoring commitment are the O-rings able to perform in extreme cold environments, while remaining pressure resistant. They will be in use above and beyond the stratosphere at this altitude “only” for the time being.
Everyone holds their breath: “Five, four, three, two, one lift off!” There’s not much that beats a rocket launch countdown for excitement, is there? A boys’ and girls’ dream of today? That dream is being lived by the university students of the “Delft Aerospace Rocket Engineering” – acronym DARE – in the Netherlands. Based at the Delft University of Technology, this is one of the most advanced amateur rocket clubs in the world. In July 2018, the students of the club launched the rocket “Stratos III”. The goal was to break the European altitude record of 33 kilometres. Unfortunately, the rocket disintegrated over the sea 20 seconds after launch at an altitude of 10 kilometres - and speed of 3500 kilometres per hour. After improving this design, the aim is to make their Stratos IV rocket the first student-built rocket in space. However, the current propulsion system is not powerful enough to reach even higher altitudes. A cryogenic liquid propulsion system is now in development for exactly this purpose, that is, flying the DARE rocket higher than ever. This propulsion system uses sealing technology made by Angst+Pfister.
For a new generation of engineers
More than a hundred students with an infectious zeal for space, rockets and the accompanying science are working on this project. “We agreed to help the minute we got the request,” says Jan Boomsma, product application engineer at Angst+Pfister in the Netherlands. After all, this is about promoting the profession for a new generation of engineers. Angst+Pfister is not alone: The list of partners and sponsors the enthusiastic students have convinced to contribute to their project reads like a “who’s who” of international advanced technology.
“It is not simply about firing a rocket into the sky,” declares Jan Boomsma. As well as facilitating scientific publications, the project in this highly innovative environment also stimulates knowledge transfer with the Delft University of Technology. Many of the students who had previously taken part in the project have gone on to a career with one of the project partners after graduation. The ambitious student team is always looking to go one step further. “It’s our dream to get to space as the first amateur rocketry team in the world,” says the student Krijn de Kievit.
Operation under extreme conditions
Future Stratos missions will very likely be powered by liquid oxygen and bioethanol. The students have chosen this propellant combination because it is much more efficient than the fuels currently used. The problem is oxygen can only be liquid at cryogenic temperatures, that is, extremely low temperatures. Angst+Pfister’s O-rings seal the oxygen tank – under no circumstances can the liquid escape from the tank. “If a leak led to it coming into contact with the bioethanol, there would be a very high chance of the rocket exploding,” explains Jan Boomsma. In other words, everything is at stake. The O-rings supplied by Angst+Pfister have to provide a perfect seal at minus 183 degrees Celsius – and a pressure of 40 bar. “Under such extreme conditions, conventional materials such as polytetrafluoroethylene (PTFE) cannot be used,” adds Jan Boomsma. Pure metal rings in the sizes required would have been excessively expensive and virtually impossible to install in this design of tank. Angst+Pfister decided to go for a FEP-O-Seal type O-ring, whereby a Cryolox stainless steel core is encapsulated with FEP. “We would be happy to provide the students with other products such as our hoses – and technology expertise.”
Significant amounts of frost showing on the top of the liquid oxygen tank. These are the conditions the O-ring has to cope with.
The first three tests of the rocket system and the sealing rings in the spring of 2018 went well, however, in these tests we used liquid nitrogen and water as substitutes, because these liquids are not explosive. “We first wanted to test the complete operation of the system and our procedures in a much safer, but still thermally-equivalent environment to the one present during an actual launch. Moreover, we wanted to validate our design calculations with these tests,” explains Krijn de Kievit. Nonetheless, this was the first time the system had been subjected to a temperature of almost minus 200 degrees Celsius. “Our O-rings gave a tight seal,” comments a happy Jan Boomsma. Now, the first test involving fire is due – expectations are running high. If this test is successful, a big milestone will have been achieved in the quest to build a rocket that reaches an altitude higher than ever before.
The skilled engineers of Angst+Pfister have long been fascinated by the idea that the world record will be broken and that their solutions and the company logo may one day be transported into space...
Overview of the test setup.
High-pressure expulsion of liquid nitrogen and water.
Ice on the main line to the machine.
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published: 12 Ağu 2020 11:41:00 by: Angst+Pfister Group