Sharp Edge Flight Experiment
The Sharp Edge Flight Experiment ( SHEFEX ) ( German sharp-edged flight experiment ) stands for a program of the German Aerospace Center (DLR) to develop some new, inexpensive and safe design principles for space capsules and space gliders with the ability to re-enter the atmosphere and their integration an overall system. The DLR explained the intentions pursued with SHEFEX: The aim of the research work is a space glider that will be available from 2020 for traceable experiments under weightlessness . The space glider project was given the name REX-Free Flyer (REX for Returnable Experiment).
When spacecraft re-enter the earth's atmosphere , temperatures of over 2000 degrees Celsius arise due to the high speed of the spacecraft and the friction between them and the molecules in the air, as well as their displacement. In order not to burn up, spaceships have so far required very expensive and sometimes failing heat shields .
First spacecraft with sharp corners and edges
The eponymous idea for the sharp-edged flight experiment by project manager Hendrik Weihs , coordinator for return technologies at DLR, is a completely new shape for a spacecraft, namely with sharp corners and edges instead of the round shapes that were previously used in space travel . Flat individual components, from which this shape can be composed, can be produced more cost-effectively than rounded ones.
Klaus Hannemann , Head of the Spacecraft Department at the DLR Institute for Aerodynamics and Flow Technology in Göttingen , explained this fundamental advantage of the concept :
“A space shuttle has over 25,000 differently shaped tiles . Due to the simple shape of the SHEFEX tiles, the maintenance costs of the thermal protection system can be reduced and a simple exchange in space would be conceivable. "
Those responsible are also striving for better aerodynamics . Overall project manager Hendrik Weihs explained:
"The capsule almost achieves the aerodynamic properties of a space shuttle, but is smaller and does not require any wings"
The DLR stated programmatically:
“Based on the experience gained in the development of thermal protection systems, it was possible to identify the specification of curved outer contours with high accuracy as a significant cost factor. Large, curved fiber-ceramic structures require complex manufacturing aids and corresponding auxiliary forms and optimized manufacturing processes for each individual component. A possible savings potential therefore represents the simplification of the outer contour by dissolving it into as few flat surfaces as possible. Basically, plate-shaped panels can be produced from a basic shape and adapted by simple trimming. This also leads to significant savings in the maintenance and replacement of damaged elements. In terms of flow, however, problems arise at the edges and corners during re-entry. Very high temperatures occur there, which must be controlled by new technologies such as actively cooled elements. Aerodynamically, however, this shape also results in advantages in hypersonic flight, since in this speed range contours with sharp leading edges generate less drag. "
Fiber-ceramic composite materials for the heat shield
Fiber-ceramic composite materials are used as materials for the shields . So were z. For example, in the second SHEFEX II rocket test, nine different materials were tested, mostly developments by DLR in Stuttgart and Cologne. According to the DLR, these are significantly more heat-resistant, extremely light and dimensionally stable even at high temperatures compared to metallic materials.
Active cooling for the heat shield
In addition, a heat protection system is being developed and tested in which nitrogen flows through a porous tile during re-entry and thus cools the missile. Project manager Hendrik Weihs explained about this sub-project:
"The escaping gas forms a kind of cooling protective layer around the surface so that the atmospheric gas cannot get to the spacecraft"
Control during re-entry at SHEFEX II
The second experiment, SHEFEX II , was equipped with active aerodynamic control elements that enable active flight control during the re-entry phase. These ceramic canards with their mechanical actuators and an autonomous control system are another development goal of the project.
The SHEFEX flying experiment platform is a joint effort by seven DLR institutes and facilities:
- The Institute for Aerodynamics and Flow Technology carried out wind tunnel tests and calculated the flow field on re-entry and equipped the missile with sensors for measuring temperature, pressure and heat load.
- The Institute for Building Methods and Construction Research manufactured the missile and designed and produced, among other things, the ceramic thermal protection systems. In one of these heat protection systems, nitrogen flows through a porous tile during re-entry and thus cools the missile.
- The Institute for Flight System Technology tested canards, which are control surfaces with which the position of SHEFEX II can be actively controlled.
- The Institute for Materials Research produced ceramic tiles,
- The Institute for Space Systems and the
- Facility simulation and software technology developed a navigation platform for determining the position of the spacecraft during flight.
- The DLR's MORABA mobile missile base added the two-stage launch system, controlled the missile and received the data that SHEFEX sent during the flight.
The first experimental vehicle, SHEFEX-I, was launched on October 28, 2005 on a two-stage sounding rocket from a launch facility on the island of Andøya near the Norwegian city of Andenes . SHEFEX-I reached an altitude of over 200 km above the North Sea. The device re-entered the earth's atmosphere within 20 seconds at almost seven times the speed of sound . The measurement data and live images from the on-board camera were transmitted directly to the ground station. Since an error occurred when activating the parachute system , which led to the loss of the parachute system, the SHEFEX-I flight unit was lost. However, according to the DLR, the evaluation of the measurement data provided important insights which, from DLR's point of view, made SHEFEX-I a great success. A missile system was used as propulsion, which was combined from a Brazilian VS-30 lower stage and a HAWK missile as upper stage. The costs of the three-year project amounted to approx. 4 million euros and were raised by the Helmholtz Association of German Research Centers (HGF) and the DLR as part of the space program .
With the development of SHEFEX II, nine different heat protection systems were to be tested on the faceted outer skin. These are predominantly developments made of fiber ceramics from the DLR locations in Stuttgart and Cologne . In addition, test areas were made available to the German space companies EADS Astrium and MT Aerospace as well as to the international partner Boeing . Sensors developed by the DLR Hypersonic Technology department in Cologne were built into the test vehicle . You should measure pressure, heat flow and temperature in the payload tip during flight .
On June 22, 2012 at 9:18 p.m. CEST, the seven-ton, almost 13-meter-long rocket with its SHEFEX II payload was launched from the Norwegian rocket launch site Andøya . The SHEFEX II space capsule reached a height of around 180 kilometers. SHEFEX II flew through the atmosphere at a speed of 11,000 kilometers per hour (eleven times the speed of sound). When it re-entered the atmosphere, SHEFEX II withstood temperatures of over 2,500 degrees Celsius and sent measurement data from over 300 sensors to the ground station.
DLR has envisaged the Shefex III project for 2021, which will be launched with a VSB-30 launcher and should reach a Mach 5 re-entry speed . The aim of the demonstration flight will be to demonstrate an autonomous re-entry and test of key technologies for future reusable booster systems.
REX-Free Flyer (SHEFEX IV)
The REX-Free Flyer was considered as the first application for SHEFEX, the German program for hypersonic and re-entry technology development. As a free-flying platform with high micro-G quality, the system should allow experiments in weightlessness over several days. The possibility of a controlled return as well as a modular design of the experiment racks, which is based heavily on that of sounding rockets, should enable experimenters to access their experiments as quickly and cheaply as possible.
- ↑ a b c d SHEFEX II spacecraft will be launched in Norway in September 2011. DLR, April 7, 2011, accessed on July 9, 2011 .
- ↑ Raumgleiter - REX-Free Flyer ( Memento from February 11, 2013 in the web archive archive.today ), accessed on June 28, 2012
- ↑ a b Test for new spacecraft. Astronews, May 10, 2010, accessed June 29, 2012 .
- ↑ a b c "Top" technology from Germany: Sharp-edged DLR spacecraft presented ( Memento from February 10, 2013 in the web archive archive.today )
- ↑ a b c Through the atmosphere with sharp edges. DLR, June 22, 2012, accessed on July 9, 2012 .
- ↑ a b SHEFEX II - Another step in the flight test program for re-entry technology. (PDF; 2.7 MBarchiv-url = https://web.archive.org/web/20131217125203/http://www.bw-feiert.de/fileadmin/uploads/winners/51_Weihs/handout_rev5-2.pdf ) Retrieved August 16, 2012 .
- ↑ a b SHEFEX flight experiment successfully started. DLR, October 27, 2005, accessed on July 9, 2012 .
- ↑ Waldemar Bauer, Peter Rickmers, Alexander Kallenbach, Sven Stappert, René Schwarz: Upcoming DLR Reusability Flight Experiment . In: Proceedings of the International Astronautical Congress, IAC . Adelaide, Australia September 17, 2017 ( dlr.de [accessed December 14, 2018]).
- Dragon (spaceship) , American new development of a cost-effective spaceship from SpaceX , which uses an ablative heat shield.
- DLR: Because of the atmosphere with sharp edges , with a series of pictures. Retrieved June 28, 2012
- Information on project manager Hendrik Weihs
to SHEFEX I:
- DLR: SHEFEX flight experiment successfully started . October 27, 2005 , accessed June 28, 2012
to SHEFEX II
to the REX-Free Flyer
- DLR: Raumgleiter - REX-Free Flyer. Website of the German Aerospace Center (DLR), Institute for Building and Construction Research
to the launch site:
- Page of the Andøya Rocket Range space airport about the launch of SHEFEX II , with numerous pictures of the construction of the two rocket stages, the assembly of the test body, the launch preparations and the launch.