This Friday DARE was invited to the Demonstration Center of Linde in Schiedam we were instructed on the safety and operational risks of cryogenic liquids. After the launch of Stratos II+ to 21.5 km, DARE is looking ahead to develop high performance engines which will eventually carry a successor rocket into space. However Stratos II+ was already approaching the efficiency limits of the nitrous oxide based propulsion system. In order to overcome these limitations, DARE will develop a liquid propulsion system based on liquid oxygen. Using liquid oxygen, the efficiency of the rocket is increased as well as its density, resulting in a more powerful and compact system.

The use of liquid oxygen will however be accompanied with a number of new safety risks. Oxygen is extremely reactive and will combust with virtually all materials, imposing strict requirements on material selection and feedsystem design. In its liquid state, oxygen has a temperature of -183 ⁰C, introduction the risk of frostbite for personal and embrittlement of materials. Because of these properties, the use of liquid oxygen requires a lot of insight and experience. Linde, the world’s largest supplier of industrial gasses, has this experience and was willing to share it with DARE such that we can start our new endeavor to reach space in a safe manner. In this context members of the new cryogenic propulsion team and the DARE safety board travelled to the demonstration center of Linde for an in-depth safety instruction.

preliminary Feedsystem architecture of the cryogenic liquid rocket engine test setup

Wilbert Wissink and Paul Verhage from Linde started the day with a presentation on the basics high pressure and liquefied gasses. After the basics and the production process was explained, the presentation focused on the do’s and don’ts when it comes to the design of pressurized gas systems and the handling of pressurized gas cylinders and dewars. Finally the instruction focused on the specific risks of liquid oxygen with respect to material compatibility, prevention and mitigation of ignition risks and the recommended safety gear. After the Q&A session that followed the lecture, it was time for a number of practical demonstrations where the DARE team could observe firsthand what the implications of cryogenic liquid on materials and operations are.

Demonstration of the effects of cryogenic liquids

The lessons learned today will prove an invaluable addition to the existing operational experience of DARE with respect to the handling of high pressure gasses. Furthermore, the lessons will not end today as Linde safety engineers will review the designs and operational procedures of the new cryogenic liquid rocket engine test setup. With the assistance of Linde, DARE is confident that it can safely step into the realm cryogenics to propel new rockets on their giant leap to space.