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SCALED FLIES VERSATILE PROTEUS

When it comes to unique shapes, Burt Rutan is the right man. Rutan, being "one of the century's most innovative designers" (Time magazine), and his team from Scaled Composites is currently flight testing an aircraft at the Mojave airport in California the roots of its design appears to go back to the record setting Voyager with which in 1986 Rutan's brother Dick together with Jeana Yeager flew non-stop around the world without refueling.

With its long and thin fuselage, main wings at the rear of the fuselage, two vertical stabilizers and long canard wings in the forward fuselage area, the twin-jet Proteus is especially designed for long missions at altitudes up to 60000 ft.

The high altitude aircraft's name was not choosen incidently: According to the Greek mythology, Proteus was a God that could change his shape at his own will. The Proteus aircraft is designed in such a way that the middle segment of the fuselage, the so called payload barrel, can be exchanged, giving the aircraft a broad range of possible payload options.

Along with atmospheric research or reconnaissance missions, Proteus was meant to accomplish primarily one mission which, in the civil sector, has so far only been done by satellites or transmission towers: the wireless data and communication transmission.

The idea is not entirely new. Several companies worldwide are developing concepts for high-flying aircraft which would carry communication payloads. Washington D.C. based Sky Station International, for example, is working on an unmanned airship which would hover at 70000 ft over metropolitan areas.

The St. Louis based Angel Technologies also started to think about such concepts at the beginning of the nineties. The idea of using an unmanned airship was abandoned soon. "There were to many unanswered technical issues and, today, there are several certification and safety issues attached to using unmanned vehicles over large populated areas", says Marc Arnold, Angel Technologies' CEO and chairman.

Rutan's Proteus on the other side seemed to be promising for use as a so called HALO aircraft (High Altitude Long Operation). Meanwhile, Angel has the exclusive right for using the Proteus design for these missions. Not entirely incidentally either: Wyman-Gordon, the parent company of Scaled Composites, is the largest investor in Angel Technologies.

In principle, the Proteus in the HALO configuration with a large antenna payload (diameter: 18 ft) would operate like an atmospheric satellite. In shifts, a fleet of these aircraft will fly over metropolitan areas, ensuring a continous telecommunication, data transfer and multimedia service. The data rates would be much higher than any satellite in low or geostationary orbit can supply today and would be comparable to the performance of fibre optical cables.

As compared to satellites, high flying aircraft are much closer to the users on the ground (about 10 to 1000 times, depending on the satellites' altitude and inclination). The HALO's antennae could be supplied with much more energy from the aircraft systems than conventional transponder payloads on satellites. The Proteus' two Williams/Rolls-Royce FJ44-2 turbofans will supposedly be able to generate 40 Kilowatts for the payload, allowing an initial data rate of 16 Gigabit per second.

Angel sees its projected HALO network "as the last mile to the user". "We don't want to substitute satellites but compliment them", says Marc Arnold. Along with the local service, HALO could communicate with satellites such becoming part of a global network.

A Proteus in HALO configuration would typically fly a 9 to 14 kilometer circular pattern at altitudes of 51,000 to 60,000 ft. The antenna underneath the belly of the aircraft will be roll-stabilized, ensuring a horizontal orientation of the payload at normal bank angles.

Out of 51,000 ft altitude, the antenna would cover a footprint on the ground with a diameter of approximately 90 kilometers. Positioned over New York City, this footprint would cover 4,8 million households and roughly 12 million people.

Still, the maximum number of users per payload would be much less. According to Angel, one system would be able to serve approximately 100,000 to 750,000 users. Private households can expect data rates from one to five Megabit per second, business application can connect up to 12,5 Mbit/s and specific applications even up to 155 Mbit/s. Angel is planning to use the frequency bands at 28 and 38 GHz which are currently earmarked for terrestrial applications.

In order to connect with the aircraft, the users will have to install a special roof antenna. The clients are then connected via the aircraft's antenna payload either directly to other users or via a central HALO gateway to other networks and Internet providers. One big marketing advantage of the HALO network would be that it would eliminate the requirement for costly installations of fibre optical cables on the ground to each customer.

As compared to satellite systems, Angel sees a major advantage in the HALO network by being able to set-up a system over one city in a short period of time and to build-up the system city by city. "Satellite constellations, on the other side, are an all-or-nothing investment", says Marc Arnold, "such systems would often require the investment of billions of dollars before becoming operational." Angel sees a worldwide market potential for up to 300 cities and has already signed options for 100 Proteus aircraft, a contract that could be worth 760 million dollars. The aircraft would be manufactured at Scaled Technology Works in Colorado, a new sister company of Scaled Composites.

In each of the envisioned HALO networks, a fleet of three aircraft (two operational aircraft plus a back-up) would ensure a 24-hour service on seven days of the week. Los Angeles is one of the potential candidates for a first application. Angel is considering to set up a test operation with precertified aircraft in about two years from now. The actual certification of the Proteus aircraft, which first flew in July of 1998, would then take another one or two years.

While Angel Technologies' current focus is on the final configuration of the antenna payload, Burt Rutan is pushing the Proteus flight tests at Mojave.

The aircraft structures are primarily made of epoxite graphite composite materials. Only the left wing tip is made of glass fibre, since, unlike carbon, this will not block radio waves in turns.

The elevators are located at the canard wings and the ailerons at the main wings. The rudders are mechanically connected to sidesticks in the two-crew cockpit. Proteus does not have any spoilers or high-lift devices. However, in order to be able to increase the maximum descent rate in case of emergency descents from stratopheric altitudes, Scaled is currently considering alternatives such as a brake chute in the aft fuselage.

Because of the canard design, the aircraft takes off and lands in a characteristic three-point attitude. The take-off and landing rolls are quite short, allowing the aircraft to be operated from regional airports.

The Proteus cockpit is being optimized for the two pilots and the long mission durations (up to 14 hours). The seats are reclining, allowing the non-flying pilot to rest. In the long term, Angel is still considering an unmanned and "pilot optional" version of the aircraft. Along with former airline captains (older than 60 years), Angel plans to mainly hire young pilots who want to accumulate a lot of flying hours fast for a further career with the airlines.

Proteus will have its European debut at the Paris airshow in June. Then, Scaled plans to present first concepts and prototypes of potential payloads for the high-flying aircraft. Burt Rutan himself has his own plans with the aircraft. He wants to use Proteus as the launch platform for a small space capsule that would take three space tourists to a suborbital flight above 100 kilometers. With this plan and the Proteus already flying, Rutan is currently the strongest applicant for the $10 million X-Prize which is set by the St. Louis based X-Prize foundation.

From page 36 of FLUG REVUE 5/99