Do microwave drones dream of frozen pizzas?, Part 2
Welcome back, my reading friend. Isn’t the story of the Stationary High-Altitude Relay Platform (SHARP) fascinating? You wish to read more about it, don’t you? Let us proceed, then. Between 1982 and 1986, the Communications Research Centre (CRC), in Ottawa, Ontario, conducted some studies to see if and how the SHARP could be used to deliver a wide variety of telecommunications and broadcasting services across Canada, in a cost-effective fashion. Meanwhile, a University of Toronto Institute for Aerospace Studies (UTIAS) team designed a small model airplane to test the experimental rectennas developed by CRC engineers. This biplane first flew in May 1985.
It was sometimes before or after that time that the researchers came up with a totally new configuration for the SHARP: a slender fuselage with a pylon-mounted wing and a circular rectenna array informally known as the pizza to collect the microwaves. More rectennas of the type patented by CRC were mounted underneath the wing and fuselage. This configuration offered the best achievable compromise between maximum aerodynamic efficiency and minimum variation in microwave beam power density.
CRC approved the construction of a 1:8 scale SHARP flight demonstrator model in 1985. The UTIAS team constructed an unknown number of these in 1985-87. It conducted several flights in Toronto, Ontario, using batteries rather than microwaves to provide the electricity needed by the motor. In late June or early July 1987, as the team got ready for the first microwave-powered flight, in Ottawa, a nesting field mouse chewed through part of the balsa wood structure of the test vehicle, the SHARP-5, and cut a number of control cables. This small rodent later took up residence inside the vehicle. The damage was such that flight testing was delayed by several weeks.
Finally, on 17 September, a CRC researcher, Tom Ohno, hand launched the SHARP-5. The red and white model flew on battery power until it intercepted, at a height of about 100 metres (330 feet), the powerful microwave beam emitted by a parabolic antenna on CRC’s grounds. An employee and experienced pilot of radio-controlled gliders by the name of Gerry Bower kept the model inside the beam for 20 minutes. This low-key event was a first for Canada and the world.
The first public flight of the SHARP-5 took place on 6 October. The federal Minister of Communications, Flora MacDonald, was on hand, as was the father of modern microwave wireless power transmission, retired American researcher William C. Brown. There were also researchers, government officials and 50 or so media representatives from Canada and abroad. A few people spoke briefly. MacDonald apparently compared the importance of this flight with that of the Wright brothers, back in December 1903. And yes, my reading friend, yours truly will talk about Brown at a later date. Be patient.
Despite wind gusts of up to 20 kilometres per hour (12 miles per hour) and a fair amount of mud on the ground, Ohno successfully hand launched the SHARP-5. As before, the model flew on battery power until it intercepted the microwave beam, at a height of about 100 metres (330 feet). The 4-minute climb had not been easy, however, as Bower had to struggle to keep the SHARP-5 under control. For some reason or other, a turkey vulture got uncomfortably close to it. With some difficulty, Bower managed to keep the SHARP-5 inside the beam for about 3 and a half minutes, and then landed it. Bower pointed out it had never flown in such bad conditions before. One might argue that, had an official presentation not been scheduled on that day, the model would have remained firmly on the ground. In any event, this brief demonstration was the first ever public flight of a microwave-powered airplane.
The Paris-based Fédération aéronautique internationale, the world organisation responsible for registering all types of aviation-related records (speed, distance, altitude, etc.), later granted a certificate to CRC in recognition of the fact that the SHARP-5 had made the first officially recognised flight of a microwave-powered airplane. If truth be told, the SHARP programme was the most advanced of its type in the world.
While team members were certainly optimistic about the future, one worry they expressed was the public’s concern about the health and environmental impact of microwaves. The researchers recognized that the energy levels in the immediate vicinity of a full scale SHARP would exceed the Canadian safety guidelines for chronic exposure to microwaves. Even so, they believed that a warning system could be developed to turn off the beam if an aircraft got too close, to ensure that its avionics would not be affected. In most of the coverage area, the microwave energy levels would be within the guidelines.
Interestingly enough, an improved version of the SHARP was almost ready for testing by the time of the October 1987 flight. This SHARP-6 was similar in size to its predecessor but had a much improved wing. The improved performance of this new design meant that it would form the basis of the full scale SHARP. This being said, it looks as if the SHARP-6 only flew using batteries rather than microwaves to provide the electricity needed by the motor. And yes, attentive reader, the SHARP-6 is the vehicle portrayed in the cover of the January 1988 issue of Popular Science that we saw in the first part of this article.
The next phase of the programme was the construction of a much larger, 1:4 or 1:2 scale model. Able to fly at an altitude of up to 5 000 metres (16 500 feet), this model would be used to test the endurance of the SHARP concept. That part of the programme might take 2 or 3 years. Even though preliminary (design?) work on it had begun by the summer of 1989, the large scale model of the SHARP was never tested. Indeed, it was never built. This being said (typed?), the SHARP-5 or -6 was tested near Kingston, Ontario, in 1991.
By late 1991, a consortium was still trying to find investors willing to help build a full scale SHARP. This consortium included a provincial electricity provider, Ontario Hydro; one of Canada’s two main cellular telephone companies, Cantel Incorporated, a company owned by Rogers Communications Incorporated; the Ministry of Transportation of Ontario; and the University of Toronto.
In spite of its potential, the SHARP programme came to an end in the early 1990s. The Department of Communications was unable to obtain the significant funding required for the next phase of demonstration. It has been suggested that lobbying on the part of people or companies involved in the construction of communications satellites in Canada played a role in the demise of the SHARP programme – a sad end for such a promising concept. And yes, the SHARP-5 is part of the collection of the Canada Aviation and Space Museum, in Ottawa. How cool is that, my reading friend?
The author of these lines wishes to thank all the people who provided information. Any mistake contained in this article is my fault, not theirs.