Following the flight of the SHEFEX II spacecraft on 22 June 2012, researchers at the German Aerospace Center have performed an initial assessment. "The flight of Shefex II followed the precomputed trajectory and we received extensive and valuable data from all the experiments in real time," says DLR Project Manager Hendrik Weihs. With SHEFEX II, researchers are investigating technologies to make spacecraft re-entry less expensive.

The spacecraft landed west of Spitsbergen; here, a boat was intended to rescue the payload from the sea, but missing data during the last seconds of the flight and the harsh weather conditions have complicated this task. The researchers are now assessing the viability of locating and recovering it from the ocean floor.

Shortly after the completion of the 10-minute flight from the Andoya Rocket Range in Norway on the evening of 22 June 2012, a search aircraft received the first weak signals from SHEFEX II. "We know that the landing went as planned because the spacecraft was designed to emit a signal only after the parachute had opened," explains Weihs. Ideally, data from the last seconds of the flight would have been transferred to the ground station in Spitsbergen.

"Unfortunately, the station was unable to track the spacecraft." It was planned that the experimental phase of the SHEFEX II flight through the atmosphere would last 55 seconds; researchers are missing data from the last five seconds. For the researchers, this was not such a great loss; the real challenge was the spacecraft's recovery from the ocean.

"The signal received could only be from our spacecraft; we have analysed images acquired with the TerraSAR-X satellite and no other objects were visible at the landing site," says Weihs. But waves nearly three metres high prevented the salvage vessel from getting to the landing zone. On 24 June 2012, the search was called off. "We are now trying to determine where, exactly, the spacecraft sank, and whether it can be salvaged."

Active control and cooling
To evaluate their experiments, the researchers acquired large quantities of data from the spacecraft, down to an altitude of 29 kilometres, from the ground stations at the launch site and on a nearby mountain. The experiment phase of the flight began at an altitude of approximately 100 kilometres, as the rocket re-entered the atmosphere, and ended at an altitude of 20 kilometres.

"We know already that the 'fins', known as canards, functioned properly," says Weihs. The researchers were able to actively control the spacecraft, unlike SHEFEX I, which was launched in 2005. It was already clear during the flight that SHEFEX II had carried out the control manoeuvres as planned. In one of the experiments, nitrogen flows through a porous tile, actively cooling the craft during re-entry. "We have data for the gas outflow, and we have the spacecraft's surface temperatures - now, the evaluation begins."

The researchers are also happy with the accurate trajectory of the spacecraft. "This is the first time that our mobile rocket base has developed and flown a launch system in this configuration."

The experience gained with SHEFEX II will be incorporated to the follow-up project SHEFEX III - a spacecraft, whose atmospheric re-entry is scheduled to last up to 15 minutes. "The salvage of the spacecraft would be the icing on the cake," says Weihs.