AN ISRAELI COMPANY is developing a unique high-altitude long-endurance hovering platform designed to act as a low-cost substitute for a communications or surveillance satellite.
The Rotostar, is being developed by Silver Arrow, one of Israel's leading unmanned-air-vehicle (UAV) manufacturers. The Israeli Government, is funding part of the programme and a scaled-down prototype is scheduled to be flown, in about five years' time.
The concept is based on four or more UAVs orbiting a platform suspended between them. The number of UAVs depends on the size and weight of the payload to be put on the platform. The cable, which connects the platform to each UAV also, serves to transmit electrical power to their motors.
Silver Arrow will test two variants - one powered by solar energy. A central solar-panel system on the platform will collect the solar energy, which will be transmitted to the electrical motors of the UAVs.
The second version will have a ground-based microwave radiator, which will direct a radiation beam to the platform, to power the UAVs.
According to Elie Gamzon, vice-chairman of Silver Arrow, the Rotostar is designed to hover at an altitude of about 17km and have a theoretical endurance of one year.
The solar-energy variant will weigh 1,000kg and will be capable of carrying a 200kg payload. The microwave-powered version will also weigh 1,000kg, but will be able to carry a 300kg payload.
The microwave-beaming station will require an antenna with a diameter of 60m, which will transmit a 200kW beam towards the Rotostar's platform. The microwave 32GHz beam will supply 50kW of power to the rectifying antenna on the lower side of the hovering platform.
The Rotostar will require a special, circular, take-off strip, with the platform being lifted from a specific depression in the ground. The prototype now being developed will weigh 100kg and will hover at an altitude of 6,500ft (2,000m). Silver Arrow, jointly owned by Elbit and the Federman group, is involved in some of Israel's most classified UAV programmes.
Source: Flight International
