The dream was of a personal jet-pack and not just for the high flyer. However this blue skies technology never took off David Hambling This 21st century is not what it was cracked up to be. It is not that I actually wanted to live in a gleaming glass skyscraper attended by robot butlers, and I never liked the idea of food pills or silver lam’ jumpsuits anyway. What bothers me is the lack of jet packs. We should all have one by now, a device you can strap on to your back and take off into the wild blue yonder. Imagine the freedom of flight without the trouble of airports. Commuting in minutes, with no need to worry about traffic or parking spaces. In the 1930s Buck Rogers’s flying belt was pure fiction, but by the 1960s there were serious articles like Over Hill, Over Dale In Army’s New Rocket Belt and Man Learns To Fly In A Steam-Powered Corset. James Bond used one for a quick getaway in Thunderball. Personal flight seemed to be just around the corner – what happened? The first practical device was the Bell Rocket Belt. Hydrogen peroxide fuel was injected into a chamber where a catalyst broke it into water and oxygen. The exhaust of superheated steam produced an ear- splitting scream and propelled the wearer over hill and dale, but only for the 20- second duration of the rocket motor. An improved version lasts only 30 seconds. Although still used for displays, the design is limited to curiosity value. The military liked the idea and funded a second project, the Bell Aerospace Jet Belt. This was based on a small turbojet engine with thrust nozzles directed downwards from the operator’s shoulders. By 1969, the prototype was flying at up to 38kph for four minutes at a time. The makers reckoned that it would eventually be capable of more than 128kph for 20 minutes. Unfortunately, some design weaknesses became apparent, especially during landing, when pilots had to cope with 100kg of jet on their backs. Falling over with a jet engine running is hazardous, with the risk of ingesting foreign objects. After years of frustration, Bell sold the rights to Williams Research Corporation. Williams built the next model to take to the skies, the Wasp, sometimes described as a flying pulpit. The pilot stood astride the engine, with a 63 000 revs-a-minute jet between his legs. “What if it tossed a rotor blade?” asked writer Terry Metzgar. The designers covered the engine with Kevlar shielding to lessen the risk of damage if the worst happened. Landing wasn’t a problem, but the military decided that it lacked the endurance for a mission and turned it down in 1982. Undaunted, Williams went on to produce the X-Jet. Similar to the Wasp but with a highly efficient turbofan engine from a cruise missile, it could fly for 30 minutes at a top speed of 96kph. The X-Jet was highly manoeuvrable and much more stable than it looked. By 1989 the United States Army had turned it down; the reasons are given in official reports, which are still classified. Perhaps it was the cost, which was described as being “more than a Jeep, less than a helicopter” depending on the size of the production run. A more basic issue was that the X-Jet was competing with helicopters that were faster, had longer range and were capable of carrying more than just a single soldier. The one area where it might have had an advantage was reconnaissance, where small size and agility are an advantage. Unfortunately, this niche was already being taken up by small unmanned aircraft. There was no application to persuade the army that the X-Jet was an unmissable opportunity.
Personal flight languished for almost a decade until taken up by Millennium Jet, a civilian aerospace company. Its programme started secretly in 1997, aided by Nasa and the Defence Advanced Research Projects Agency. Their device, the SoloTrek XFV, is an exoskeleton surrounding the pilot, with two enclosed fan blades overhead. The power plant is a two-cycle petrol engine running on ordinary unleaded, which should give two hours of flight at up to 120kph. Millennium Jet is keen to emphasise the huge number of safety features built into the SoloTrek. These range from multiple back-up systems and sensors on critical components to a persuasion system that encourages the operator to land when fuel starts to get low. If all else fails there is a parachute to ensure a safe landing. There is even a retinal scan device in the control helmet that confirms the pilot’s identity. The SoloTrek looks great, and, more importantly, it is technologically feasible. But however safe the machine itself, it is still akin to a flying motorcycle, on a road with no markings and other fliers coming from all directions. Flying at night or in bad weather would be impossible without special equipment. Then there are environmental considerations: no aircraft is quiet, and few people would be happy to have flyers buzzing over their garden.
It seems unlikely that the SoloTrek is going to be replacing the commuter train, though it might still be useful for police and fire-fighters, and it looks like a wonderful toy. Millennium Jet has yet to put a price on the SoloTrek. The firm suggests that it will be similar to a high-end sports car. This is beyond the means of many potential customers, and with two-seater helicopters available for oe60E000 (about R600E000), it faces stiff competition. The other problem is that although the mock-ups look good, SoloTrek has not yet actually flown. There have been some delays in the development cycle and it is currently at the stage of wind tunnel testing.
Millennium Jet is still looking for investors, and there is a way to go before they can apply to have their vehicle certified, let alone start production. A representative from Nasa said: “It may turn out that the SoloTrek is not feasible, yet it will take us a step closer to a more feasible system.” This brings us back to where we started. Personal flight is still tantalisingly just around the corner. But now it really is the 21st century. Perhaps the crucial difference will not be the technology, but the number of people who have grown up looking forward to being able to buy a jet pack.