- DLR flies a three-stage sonic rocket for the first time.
- Component structures, measurement methods, and estimation algorithms tested for the re-entry phase.
- A modular and distributed data collection system allowed efficient recording of data from the various experiments.
- Focus: space travel, aerodynamics, sonic rockets.
ANDOYA, Norway (DLR PR) — Reusable launch systems are exposed to high loads and temperatures when returning to the surface. The German Aerospace Center (DLR) has now successfully tested the component structures, measurement methods and evaluation algorithms for the re-entry phase with the STORT flight experiment (Key Technologies for High Energy Re-entry from Carrier Stages).
In the early morning of June 26, 2022, the three-stage rocket experiment was launched from the Andøya Space launch pad in northern Norway. At the top of the trajectory at an altitude of 38 kilometers, the upper stage reached a flight speed of about 9,000 kilometers per hour, corresponding to a Mach number above eight. It then fell into the Atlantic Ocean more than 350 kilometers from its starting point.
“To achieve higher flight speeds, for the first time we used a DLR sounding rocket with three instead of two rocket stages,” explains Dorian Hargarten of the DLR Institute for Space Operations and Astronaut Training. “Furthermore, the third stage with various scientific payloads flew a particularly flat trajectory at an altitude of 38 kilometers at Mach numbers up to eight. Here – analogous to the development of heat upon re-entry into the Earth’s atmosphere – various high-temperature experiments were carried out at the high heat loads to be investigated.”
Testing of ceramic segments and lamellae
Materials that withstand the high heat loads and dissipate them are critical to heat development in the re-entry phase. Robust heat sensors that closely monitor temperature developments are also essential.
“In STORT, the pre-body of the rocket’s third stage consists of five ceramic segments,” explains STORT project leader Prof. Ali Gulhan of the DLR Institute of Aerodynamics and Flow Technology. “We equipped the pre-shell with multiple heat flow sensors, thermocouples and pressure sensors every 90 degrees along the four longitudinal lines and are now very excited about the data analysis.”
To carry out the thermal management experiments, the researchers used three fixed canaries with ceramic outer shells on the rocket, which were developed by the DLR Institute of Structures. While one channel was actively cooled, the second channel was passively cooled. The third reference canard (no cooling) was also used to study the shock-boundary layer interaction. All three canards showed different structural responses during flight under the same thermal load.
A modular and distributed data collection system allowed efficient recording of data from the various experiments. In the previous ATEK design, a standard module made of aluminum alloys was replaced by a hybrid module consisting of a CFRP structure with metal flanges to reduce the weight of the cylindrical payload segments. In the STORT project, researchers are now testing a significantly lighter module made entirely of CFRP.
Next to DLR is the Technical University of Munich, participating in the STORT flight experiment, producing the CFRP module. Another international partner is the University of Arizona, which performed simulations for the Shock-Boundary Layer Interaction experiment on the canard. Mission planning and execution was the responsibility of the DLR Space Operations and Astronaut Training Institute’s Mobile Rocket Base Unit (MORABA).
The preliminary bodywork was designed and manufactured by the DLR Institute for Construction Methods and Structure Technology. The DLR Institute of Aerodynamics and Flow Technology, which is also responsible for project management, contributed to aerothermal design, active thermal management, payload measurement and their modular data collection.
About the STORT project
The flight experiment, now successfully conducted, is an element of the STORT research project. The project is part of the focus of the DLR sub-programme ‘Reusable Space Transport Systems’. It aims to develop selected technologies and methods regarding thermomechanical analysis and evaluation of load-bearing systems. For this purpose, the component structures, measurement methods and evaluation algorithms that were developed in basic research were adapted for flight experiment and finally qualified with flight. In addition to ground experiments, flight data provide validation data for physical modeling, numerical simulations, and system analysis, thereby enabling reliable design and evaluation of future carrier systems.