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ETH - Eidgenoessische Technische Hochschule Zuerich - Swiss Federal Institute of Technology Zurich
Section: Science Life
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Published: 12.10.2006, 06:00
Modified: 11.10.2006, 17:17
X-Station: First test flight of a stratospheric balloon
Reaching for the stars

He is pushing ahead unwaveringly with his amazing project: the aviation engineer Kamal Alavi who intends to revolutionise wireless data communications in a few years with his X-Station positioned in the stratosphere. Several ETH institutes are collaborating in the project. The first test balloon ascended to a height of 21 kilometres from the Lake of Zug on Friday 29 September 2006.

Norbert Staub

The shore of the Lake of Zug not far from Walchwil, the home of Kamal Alavi’s StratXX company, was chosen for the first stratosphere test on Friday 29 September. He is an aeronautical engineer, inventor and the driving force behind the project. The helium-filled balloon, about eight metres long and fitted with sensors, began its ascent at 10:30 hrs. A few hours later it was at its target altitude of 21 kilometres.

The start of the prototypes phase

Kamal Alavi is satisfied with this test flight for the X-Station, the flying platform that will carry Internet, TV and radio transmissions as well as mobile phones, and whose purpose is to suddenly put both terrestrial and satellite transmission into the shade. Alavi says: “This test is a milestone in the X-Station’s development and provides proof of the operability of our near-space technology. It is the same time the green light for the prototype phase of the project.”

The project’s plan is to package the most advanced antenna technology into an unmanned light aircraft suspended below a helium-filled balloon about 70 metres long shaped like a Zeppelin. This balloon will be located in a geostationary positioning the stratosphere and stabilised by the light aircraft’s propeller drive. According to StratXX, a single platform can cover a ground area more than 1000 kilometres in diameter from the stratosphere. (see also the “ETH Life” article “Flying mobile phone antenna” (1)) However, an essential pre-condition to allow the whole scheme to operate is the new WiMAX mobile phone protocol (Worldwide Interoperability for Microwave Access). This enables transmission over a distance of 30 kilometres. Its bandwidth is also enormous. A laptop equipped with WiMAX can receive and transmit 40 Megabytes per second.

Solar cells as the energy source

Kamal, who was born in Iran, explains the background of the test flight: “In the first place we have tested how the X-Station’s solar cells behave under the extreme temperature conditions in the stratosphere.” He says the cells are responsible for the system’s entire energy supply. “Thus the central question is how they cope with the conditions.” Various other measurements that are important to the project were also made. “For example in addition to the external temperature we checked the temperature fluctuations of the helium in the balloon envelope.”


Stratospheric flight with ETH participation: StratXX owner Kamal Alavi’s experimental balloon fitted with sensors ascended to an altitude of 21 kilometres on 29 September 2006. large

The latter is a critical aspect because the heating up and cooling down of the gas affects the balloon’s flight altitude. Another test involved the special camera attached to the balloon; this anticipated another possible use, namely surveillance. According to Alavi “The camera produced images of excellent quality.”

Hopes of market maturity in 2009

Alavi explains that these tests are needed to check the ongoing development of the station via computer models and possibly to correct it. “Seven more tests are planned before the scheduled first launch of the X-Station. I expect the system to reach market maturity and to be ready for continuous operation in 2009.” After a few hours at an altitude of 21 kilometres the test balloon was disconnected from the helium supply by a timer, causing it to descend towards the ground and land.

Commitment and scepticism

Among other research institutions, Kamal Alavi was able to gain the co-operation of both ETH, the EMPA (Swiss Federal Laboratories for Materials Testing and Research) and the Swiss aerospace group RUAG Aerospace in the development of the flying mobile phone antenna. The people from ETH Zurich who are involved in the project include the Center for Product Design and the Chairs of Professor Siegwart (Autonomous Systems) and Ermanni (Structural Technologies).

Rüdiger Vahldieck, ETH Professor for Field theory at the Laboratory for Electromagnetic Fields and Microwave Electronics, questions Alavi’s optimism about the predicted capacities of the flying antenna. He thinks it might be true at present to say that a single station could render mobile phone antennas in Switzerland superfluous, but the capacity of an individual platform would be insufficient in the future to process the data record rates, which are still increasing exponentially. This would continue to require terrestrial systems as well, said Vahldieck in Swiss Television’s “10 to 10” news broadcast on Tuesday 26 September 2006.(2)

(1) You will find the “ETH Life” report of 29 June 2006 at::
(2) Swiss Television broadcast on the subject, 26 September 2006:

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