SHEFEX II

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The assembled SHEFEX-II body

SHEFEX II was the second experimental missile of the development and flight test program SHEFEX of the German Aerospace Center (DLR) with the aim of making space capsules and space shuttles with the ability to return to the air layer of the earth much safer and much safer through several new construction concepts and new materials cheaper to manufacture. The project manager of SHEFEX II, in which nine institutes and facilities of the DLR as well as cooperation partners are involved, as well as the overall program is the DLR engineer Hendrik Weihs .

The project name SHEFEX is an abbreviation for Sharp Edge Flight Experiment , i.e. in German that: sharp-edged flight experiment , and stands for the fundamentally new idea of ​​the heat shield required for the entry of spaceships from space into the atmosphere through flat heat protection elements that are cheaper to manufacture and assemble to construct. In the past, all space capsules (such as Soyuz and Apollo ) or space gliders ( Space Shuttle , Buran ) were constructed with rounded heat shields. The connection of the flat heat protection tiles to a body suitable for hypersonic flight in the air layer with a good aerodynamic shape inevitably leads to sharp edges in the construction.

With the development of SHEFEX II, 9 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 .

SHEFEX II was equipped for the first time with active aerodynamic control elements, which enable active flight control during the re-entry phase. These ceramic so-called canards with their mechanical actuators and a flight control system represent another major development goal of the project.

Launcher and overall configuration

VS-40 missile on display in Parque Ana Lídia , Brazil

While a Brazilian VS-30 combined with a HAWK rocket was used as a launch vehicle for SHEFEX I , the DLR used the more powerful Brazilian VS 40M for the SHEFEX II experimental body .

The VS 40M launch vehicle is a sounding rocket , the two stages of which are each powered by a solid rocket motor, the lower stage with the S 40 , the upper stage with the S 44 . The total length of the launcher and the payload tip is 12.6 m, the total weight 6.7 t, of which 400 kg are payload.

Flight plan

According to the flight plan, the S-40 rocket motor of the lower stage has to propel the SHEFEX-II rocket with its four tons of fuel almost vertically to a height of 54 km within 60 seconds. The rocket is stabilized by rotation. The upper stage with the payload is then inclined towards a flatter angle of attack. Then the ignition of the upper stage takes place, whose 800 kg fuel shoots the payload tip in a flat ballistic path. When the fire is closed, the rotation is stopped and the rocket motor is separated from the payload tip.

The SHEFEX-II tip is controlled for a re-entry angle into the atmosphere of approx. 35 °. The re-entry into the atmosphere from an altitude of 100 km occurs at 11 times the speed of sound (approx. 3 km / s). With the re-entry into the earth's atmosphere, the actually relevant phase of the experimental flight begins, in which the quality of the nine different thermal protection variants must be proven through the measurements of the sensors, the configuration of the shape and the quality of the control surfaces including their control through the flight path. At the high entry speed, extreme heat flows occur at the payload tip and at the sharp leading edges of the canards and stabilizing fins, which heat the structures to over 1,800 ° C. The back pressure increases up to 4 bar at the end of the re-entry. During flight in the atmosphere, the re-entry angle is controlled by the aerodynamic control surfaces. The aim is to dampen the almost undamped natural vibrations and to regulate the roll position to a specified value. In addition, some taxiing maneuvers are flown in order to check some parameters that are difficult to predict on the basis of the flight data. The experimental phase ends when an altitude of about 20 km or after about 45 s is reached.

At a height of 20 km, the payload is separated roughly in the middle and both parts, which are then aerodynamically unstable, are further decelerated by the resulting tumbling movement. At a height of 5 km, a parachute system is ejected from both subcomponents, which reduces the landing speed to approx. 9 m / s.

A sea area 800 km from Andoya southwest of Svalbard was selected as the landing area.

Pre-test

In April 2012, SHEFEX II was tested in Astrium's environmental laboratory in Ottobrunn to see whether it could withstand the stresses of take-off and the subsequent flight. In the first few seconds of take-off, the payload is stressed by the vibrations. SHEFEX II was exposed to up to 2000 vibrations per second on the laboratory shaking table.

John Turner, responsible for the use of the DLR's MORABA mobile missile base , which Shefex uses to launch into space from the Norwegian missile station, explained: “ In order to stabilize itself during flight, the missile must rotate continuously. “Much like a car tire being balanced, engineers have to balance the missile for these rotations. SHEFEX II was therefore exposed to two revolutions per second on the spin table.

The missile survived both tests.

Takeoff and flight

Originally it was planned SHEFEX II in Woomera , Australia , to start the DLR ultimately chose the used even at SHEFEX I rocket launch site Andøya in Norway .

Andøya took off on June 22, 2012 at 9:18 p.m. The space capsule reached a height of almost 180 kilometers and flew through the atmosphere at around nine times the speed of sound. On re-entry into the deeper layers of the atmosphere, SHEFEX-II sent a large amount of measurement data to the ground station, the evaluation of which by the scientists involved took several years.

The flight went mostly according to plan. Unfortunately, a ground station in Spitzbergen could not receive any signals. Therefore, there is no measurement data below 27 kilometers above the ground. The missile itself was most likely located by a search aircraft, but could not be found by the rescue team when visibility was poor. Because of waves three meters high, the rescue ship could not drive close enough to the suspected landing site.

The project manager Hendrik Weihs praised the experiment as follows: "With the flight of Shefex II we are one step further on the way to developing a spacecraft that is simply built like a space capsule, but has control and flight options such as this Space Shuttle - only significantly cheaper. "

Web links

Individual evidence

  1. ^ Hendrik Weihs, German Aerospace Center (ed.): SHEFEX II, development and flight test program. With contributions from the institutes and facilities AS, BK, FT, RB, RY, RM, SC, WF and MORABA , February 19, 2010 (PDF; 5.5 MB, no longer available online).
  2. ↑ SHEFEX II spacecraft will be launched in Norway in September 2011 ( Memento from March 14, 2014 in the Internet Archive ). DLR, April 7, 2011.
  3. ↑ "Top" technology from Germany: Sharp-edged DLR spacecraft presented ( memento from February 10, 2013 in the web archive archive.today ). DLR, July 16, 2010.
  4. ^ "Flight control systems for re-entry vehicles - SHEFEX. DLR, January 6, 2015
  5. ↑ a b c d e SHEFEX II Another step in the flight test program for re-entry technology ( Memento of December 17, 2013 in the Internet Archive ). DLR (PDF file)
  6. ^ Hendrik Weihs: SHEFEX II, development and flight test program. With contributions from the institutes and facilities AS, BK, FT, RB, RY, RM, SC, WF and MORABA, slide 8. DLR, February 19, 2010 (PDF; 5.5 MB, no longer available online).
  7. ↑ Endurance test for the Shefex spacecraft ( memento of October 17, 2012 in the Internet Archive ). DLR, April 18, 2012.
  8. ↑ "SHEFEX II": salvage team is looking for hypersonic missiles. In: Spiegel Online . June 23, 2012, accessed June 10, 2018 .
  9. ↑ SHEFEX II researchers satisfied with Shefex flight. Astronews / DLR, June 29, 2012.
  10. ↑ Through the atmosphere with sharp edges ( Memento from June 7, 2013 in the Internet Archive ). DLR, June 22, 2012.