In the spring of 2019, the novel "AHRES-B" hybrid rocket engine was successfully tested on the "Viererblock" test stand at the German Aerospace Center (DLR) in Trauen. For the researchers, this was a special reason to be pleased, because hybrid rocket engines are not only fundamentally cheaper and safer than conventional rocket propulsion systems, but AHRES-B is also significantly more effective than all its predecessors. The current test has shown: The technological development of hybrid rocket engines is now sufficiently advanced to be used, for example, on sounding rockets.
The advantage: hybrid rocket engines are combinations of solid and liquid fuel engines and combine the best features of both engine types. The liquid oxygen carrier - in this case highly concentrated hydrogen peroxide - and the solid fuel HTPB (hydroxyl-terminated polybutadiene) are initially separated in AHRES-B and only meet in the combustion chamber. Therefore, there is no risk of explosion during storage and operation. In addition, the materials used are non-toxic and not hazardous to the environment.
During the test run in Trauen, the catalytically decomposed hydrogen peroxide entered the fuel block at about 650 °C. The released heat was converted into kinetic energy - into a thrust of about 2700 Newton. AHRES-B fully utilized the fuel over a period of 21 seconds and achieved a doubling of the burnup rate compared to preliminary tests. The high burnup rate is important for the design of an efficient and compact engine. This was made possible by an innovative, twisted "fin geometry".
The experimental results of the validation test show quite clearly: The AHRES-B engine, which was developed in the DLR projects AHRES and ATEK and is now being tested in the DLR cross-sectional project Simulation Based Certification (SimBaCon), is far more efficient than previous hybrid rocket engines.
The development and supervision of the production of the AHRES-B engine was carried out at the DLR Institute of Aerodynamics and Flow Technology in Braunschweig. Test preparations and commissioning were carried out by a team from the Spacecraft Department at the institute's own test bed for hybrid rocket engines at the Trauen site. This test stand is equipped with numerous modern measuring and control devices and enables the safe test operation of hybrid rocket engines. The infrastructure for the safe, environmentally friendly handling of large quantities of hydrogen peroxide is unique in Germany.
The tests serve to validate the design software AHRES, which is being further developed and tested in the cross-sectional project SimBaCon. In its final version, AHRES should allow the design of hybrid and solid-fuel engines on a large scale within 100 days. The described test proved that the software works excellently. Since the underlying numerical approaches are oriented towards large engines, the next experimental phase will now test the "VISERION" engine, which is already under construction and will allow a thrust of up to 15000 Newton over 30 seconds. VISERION is being built with the support of the Investitions- und Förderbank des Landes Niedersachsen (NBank).