Researchers at Germany’s DLR aerospace center hope to complete final ground tests of the Shefex 2 (Sharp-Edged Flight Experiment) hypersonics demonstrator in the next two to three weeks in preparation for a June launch.
The mission initially was due to take place last year, but was delayed so different issues discovered during ground testing could be resolved. The new launch date being eyed is June 18.
Data gathered during the flight will be critical to designing Shefex 3. Work on the follow-on hypersonics test article, which will be similar in design to DLR’s Rex Free Flyer concept, has begun.
The June test will unfold at Norway’s Andoya Rocket Range. The Shefex 2 demonstrator, aimed at validating a range of thermal protection and other technologies, will be launched using a Brazilian-made VS-40 sounding rocket. The first stage will boost the system to 80-90 km (50-56 mi.) altitude, where the trajectory will be flattened and the second stage ignited. The Shefex 2 will then separate and reenter the atmosphere at a 30-deg. angle.
The core of the experiment will take place with Shefex 2 descending to 20 km altitude from 100 km at Mach 9-11, says Hendrik Weihs, DLR’s program coordinator for reentry systems at the Institute of Structures and Design. During that phase, the vehicle is due to perform two maneuvers; one is to slightly change its angle and the other is a roll maneuver. Various structural and airflow measurements also will take place.
Once the experiment phase is over, the vehicle will separate into two parts to slow it down and initiate parachute decent at around 4 km. DLR hopes to recover the vehicle and has located a splash-down location in relatively shallow waters to ease recovery even if the parachute mechanism fails. Several telemetry stations will be used to gather data in flight but if those fail, data is being recorded onboard that could be used to extract information after the flight.
Various different ceramic and metallic thermal protection systems are being investigated. An active cooling system also is being examined that uses carbon dioxide to create a thermal protection layer to keep the hot temperatures encountered during reentry from the ceramic structure.
Weihs notes that the test results will help decide what technologies are incorporated into Shefex 3. That vehicle is expected to validate a subscale version of an operational reentry vehicle. The smaller sizes means relevant test data can be gathered at speeds of Mach 20-24, so DLR can remain within a suborbital test regime.
Shefex 3 is to lead to the test flight of an actual Rex Free Flyer prototype (also referred to as Shefex 4). The agency was targeting a 2020 flight test, but funding uncertainties will likely push that event further out.