Arrow in The Blue
Here is an interesting article published in the DLR Magazine (sept. 2012 - English Edition) describing the campaign to launch the german experiment SHEFEX II, held at Andoya Rocket Range (Norway) in June this year. The German experiment was launched into space by a Brazilian Sounding Rocket VS-40, which completed its third flight and mission with great success.
Arrow in The Blue
Near The Artic Circle, The Sharp-Edge SHEFEX II Spacecraft
Flew Into The Bright Summer Night Sky
By Manuela Braun
The roof of the launch hall has moved aside and the
launch tower with SHEFEX II rises to the vertical position
On 22 June 2012, SHEFEX II shot skyward like an arrow from the Norwegian Andoya rocket base. After a 10-minute flight, the angular spacecraft re-entered Earth’s atmosphere to land in the ocean close to Spitsbergen. Seven years of preparations for the project concluded with a launch campaign in Norway that lasted just weeks. The final days before the launch were a nervous time – assembling, testing, waiting for results and conducting practice countdowns. Then, more waiting – this time for a windless, rain-free day to ensure a perfect launch – until the critical moment finally arrived. The DLR Magazine accompanied the researchers during their preparations and launch.
|Launch preparations at the Andoya Rocket|
Range. In the integration hall, DLR researchers
assemble the various parts of the spececraft.
Saturday, a few days before launch
In science, the devil is in the details, and that implies a close up view. In the integration hall at the Andoya Rocket Range, a group of scientists crawl across the concrete floor on all fours. They have spent all morning assembling the various components of SHEFEX II, carefully positioning edge on edge, tightening screws, and measuring everything measurable. Suddenly, a tiny metal pin falls out of a special tool. Project leader Hendrik Weihs shuffles his upper body under the trolley that is supporting the dart-like spacecraft. All eyes are directed to the ground in concentration. Just where did it go? Hannah Böhrk, who is responsible for the porous heat resistant tiles on the angular edges of SHEFEX, carefully moves her hand across the concrete floor. Design engineer Henning Elsäßer crawls on his knees. Without the metal pin in the tool, and without the final adjustment, there will be no launch; and with no launch, there will be no data on the fiery re-entry of this new type of vehicle into the atmosphere. “Have you…?” No, nobody has, so the search goes on. “Aha!” Weihs triumphantly holds up a tiny piece between his thumb and index finger, grinning; work in the integration hall can continue.
Today is assembly day; one component after another is put in position until the nose can finally be placed on the vehicle. Measuring instruments, cabling, locking rings – everything must be precisely positioned to the millimetre. Researchers from Stuttgart, Braunschweig and Oberpfaffenhofen are at work around the vehicle. SHEFEX II is a project to which seven DLR institutes and facilities are contributing their knowledge. Andreas Bierig from the institute of Flight Systems climbs onto the transport vehicle and gets up close to the canards. These small wings, which will steer SHEFEX during re-entry, must be precisely aligned prior to launch. When SHEFEX is flying, the scientist from Braunschweig will be among those sitting in the control room carrying out the flight manoeuvres. Hannah Böhrk from de Institute of Structures and Design runs a hand over ‘her’ heat-resistant tiles once again. During the flight, nitrogen will flow out of small holes in the tiles to cool the spacecraft. The nose of SHEFEX will have to withstand temperatures of over 2000 degrees Celsius as friction generates heat during re-entry. This nitrogen will form a protective layer between SHEFEX and the scorching environment.
Outside, in front of the hall, the Sun has almost reached its lowest point. Here, north of the Arctic Circle on the Vesterålen archipelago, the soft afternoon light will last all night. The Andoya Rocket Range lies in a bay between mountains and a white sandy beach. It is actually the most beautiful rocket range in the world, according to a somewhat rapt Kjell Bøen, Head of the Sounding Rocket and Balloon Department at the rocket range. Those without a role in the integration hall, stand in front of the hall entrance, freezing in the icy wind but enjoying the view.
It is finally time to roll the six-metre-long space vehicle on its transporter towards the launch platform. A black and yellow foam protector has been stuck on the sharp nose at the front so that no one will be hurt on the angular vehicle. Mobile phones, cameras, anything that can take a picture is pulled out. The majority will never get this close to their spacecraft again. But they can only go as far as the access road to the launch platform: “Only those who need to work on the launcher, on this side of the barrier now please,” says Peter Turner, Head of the DLR MoRaBa mobile rocket base. The payload is going to be mated with its Brazilian-made launcher. This is too dangerous for spectators , so access is strictly forbidden. SHEFEX II rolls slowly out of sight and disappears into the launch hall.
Prior to the launch of SHEFEX II into the sky above Andoya,
the little ‘wings’ are carefully aligned and the thermal
insulation tiles stroked once again
Tuesday – all antennas ready to receive
A day of waiting. Waiting for confirmation that the payload and engines are assembled and all the connections to the instruments in the nose are functioning. Waiting for the practice countdown. Waiting for a favourable weather forecast. It is the nerve-wracking calm before the storm for scientists with experiments on SHEFEX II. Meanwhile, the staff of the MoRaBa mobile rocket base are working frantically. Among other things, they are responsible for the two-stage launch system and for controlling the rocket.
Two minutes’ drive from the rocket range is the DLR telemetry station, which will record the data during the flight. There are screens, keyboards and bundles of cables. On a tray a box of sweets – comfort snacks for MoRaBa staff members Frank Hassenpflug and Anke Stromsky. Hassenpflug opens cupboards within which hundreds of cables and connectors are arranged in an orderly manner. “We have set all this up over the last few weeks,” he explains. In front of the door is the satellite dish that will track SHEFEX II during its flight on Friday evening.
In the meantime, Dietmar Kail and his colleagues are sitting in the DLR MoRaBa radar station near the rocket range. It is cramped and a little sombre in the mobile container. On top, a large dish antenna turns and tilts during the practice run. It will follow the spacecraft flight path and record it using multiple cameras. It is relatively calm around the launcher itself. In the interior of the hall, SHEFEX is attached horizontally to the extendable launch platform, while MoRaBa staff work with Brazilian colleagues on the vehicle and rocket engines. Five tons of fuel will accelerate the sharp-edged vehicle into the sky.
Finally the voice of Kjell Bøens rings out over the loudspeakers; SHEFEX II is going to be lifted into the vertical position on the launch platform for the practice run. Now, everyone can approach the launch complex for the first and last time. SHEFEX is attached to the launch tower, resembling a large, dark grey arrow. The roof of the launch hall opens with a loud thumping noise. The two halves of the roof move apart, and powerful hydraulic motors slowly raise the launch tower and its dart-like passenger. Thick clouds cling to the mountains as the wind whistles around the launcher.
SHEFEX II has to be assembled with millimetric precision.
John Turner of the DLR Mobile Rocket Base, MoRaBa, pays
attention to cabling, measuring instruments and locking rings
Thursday – the rehearsal
You could cut the control room’s atmosphere with a knife. The practice countdown has been running for almost four hours. John Turner, Project Leader for SHEFEX at the mobile rocket base – not to be confused with MoRaBa Department Head Peter Turner – is concentrating on four screens simultaneously. On the screen over their heads, a clock counts down the final three minutes. Everything happens as it would during a real launch; only the final push of the button to ignite the rocket engines will not occur. Kjell Bøens’ voice can be heard over the headphones. “Start the data storage systems.” Every station gives its status in order: the telemetry station, the radar station, and the receiving station on Spitsbergen, in the Svalbard Archipelago. Recording equipment is now running everywhere. Finally there is a sound like an old-fashioned doorbell. Everyone laughs. During a real launch, they would now be hearing the sirens that announce the evacuation of the launch area around the launch platform. Sixty seconds remaining. A computerized voice marks the 10-second intervals in the countdown. Even though this is just a rehearsal and everyone knows that SHEFEX must spend another night on the launch platform; the mood in the control room is one of concentration and tension. Tomorrow, the weather conditions are at last expected to be suitable. Then, everything will come together for a smooth countdown.
“Three, two, one, fire.” Those will be the critical seconds before SHEFEX is launched into space on its 10-minute flight, making its way through the atmosphere then returning. Numbers are called out throughout the control room; John Turner keys data into his PC. “Canards activated,” calls Andreas Bierig. This is the Tensest phase for the scientists: “Re-entry at 100 kilometres,” says the announcer. Hannah Böhrk is standing right behind John Turner. “Gas on,” she shouts. Nitrogen gas now flows through the heat-shield tiles on the vehicle. The computer voice stoically announces how many seconds have passed since the launch. “OK, thank you, we are finished,” says John Turner. The tension drops, and celebrations start – even though SHEFEX did not actually launch. Launch date – Friday. The real countdown is scheduled to start at 16:30.
A rehearsal for the big day at the control
room – where all things come together
Friday – lift off!
Lift-off minus 01:10. Just over an hour until the rocket is ignited. SHEFEX II is the biggest rocket to be launched from the Andøya Rocket Range. Those not actively working at the rocket range must now leave the area. They drive in convoy to the telemetry station. From there, at a safe distance, the spectators can watch the ascent. A screen shows what the cameras on board the spacecraft are transmitting back to Earth. Now only those staff members who have actual jobs to do during the flight of the spacecraft are sitting in the control room and the tower. The launch platform is precisely aligned. L minus 00:12. The countdown continues as police block the adjacent road between the small island towns of Andenes and Bleik. L minus 00:08. During the final eight minutes before the launch, it is forbidden for car engines to be running, and mobile phones must be switched off. Scientists, tourists and locals gather at the telemetry station. The Norwegian range launches up to 40 rockets a year, but SHEFEX launch has attracted quite a few curious onlookers all the same.
L minus 00:03. Everything that was practiced in the rehearsal is now happening for real. As soon as all the participants have given their green light via radio, SHEFEX will start its flight. The warning siren echoes over the surrounding area. Then it’s “GO”, and a burst of smoke and flame appears under the slender vehicle. Even before the sound is audible, at 21:18, the rocket with SHEFEX on top starts climbing into the sky. A powerful noise then rolls towards the mountain. In a flash, SHEFEX disappears into the clouds towards Spitsbergen. Seven years of planning and preparation are rewarded with a perfect launch. The spacecraft will now fly at 11,000 kilometres per hour to an altitude of 180 kilometres, before plunging back through the atmosphere.
On Spitsbergen, a search aircraft takes off to try and locate the spacecraft in the sea as it returns. Several days beforehand, a recovery ship set out from Andenes to be on station in good time. On the range, hands are shaken and congratulations exchanged. But finally there is disappointing news – the aircraft has picked up the signal , but has not found SHEFEX. Three-metre waves are making it difficult for the recovery ship to reach the landing area. Also, the station on Spitsbergen was unable to track the spacecraft on the very last part of its journey and record the relevant data. Five seconds of the experimental phase below an altitude of 29 kilometres are missing. This gives the team pause for a moment. However, the critical phase during which the angular vehicle flew through the atmosphere began at an altitude of 100 kilometres. “We have 95 percent of the data,” says project leader Hendrik Weihs reassuringly. All of the scientists will be able to work on the data from the SHEFEX flight and carry out research. The tension reduces. There is nobody without a smile in the corridors of the rocket range. “The recovery of SHEFEX now would be the icing on the cake,” says Weihs.
Sunday – post-launch is pre-launch
Although the aircraft picked up the signals from SHEFEX, the space vehicle has not been recovered. The search is finally abandoned. The researchers know the parachute opened: “Otherwise the probe would not have sent a signal,” says Hendrik Weihs. “But the heavy swell, the wind and the poor visibility were against us.” The scientists will now use the data they have acquired to research a spacecraft that can use angular edges to create aerodynamic benefits when re-entering the atmosphere and withstand high temperatures while doing so. The design resembles a mini-space shuttle, but with flat protective tiles providing extra benefits. “We are on the way to having a spacecraft that is as easy to build as a space capsule but has control and flight capabilities,” he adds. Then experiments could fly in microgravity for days and return safely to Earth. Plans for the next mission, SHEFEX III, will now start. Launch date – 2016.
Hand in Hand
The SHEFEX experiment platform was a collaboration between a number of DLR institutes and facilities. The Institute of Aerodynamics and Flow Technology was responsible for the aerodynamic design of the vehicle, numerous wind tunnel tests and computation of the flow field during re-entry , together with instrumentation to measure temperatures, pressures and thermal loads on the vehicle. The Institute of Structures and Design manufactured the vehicle and designed and produced, among other things , the ceramic thermal protection systems. In one of these systems, nitrogen flows through porous tiles and cools the vehicle during re-entry. The Institute of Flight Systems conducted the test of the canards, which are the control surfaces used for active flight control of SHEFEX II. The Institute of Materials Research made the ceramic tiles for the thermal protection systems. The Institute of Space Systems created simulation software and technology and developed a navigation platform for determining the position of the spacecraft during its flight. DLR’s Mobile Rocket Base MoRaBa contributed to the two-stage launch system, controlled the rocket and received the data sent by SHEFEX during the flight.
Source : DLR Magazine - pages 39, 40, 41, 42 and 43 - September 2012