Back to the future with pneumatic technology
In an increasingly crowded world, there are signs compressed air may have its day, writes MICHAEL HANLON.
Back in the 1890s, steam power was becoming passé. But the newfangled internal combustion engine was noisy and unreliable — and while electricity offered a future of silent, clean transport, the technology was still in its infancy. Many engineers wondered whether, in the world of the future, we would travel not in cars and trains driven by steam, electricity or fossil fuels, but via the quiet whoosh of compressed air. The 20th century, they thought, would be the pneumatic century.
We now know, of course, that it was not to be. Yet the idea of whisking around information, goods and even people in brass tubes filled with air took a surprisingly long time to die. In 1890, pneumatic mail pipes under Milan allowed the composer Verdi and his associate Arrigo Boito to have an almost real-time conversation about the opera they were working on — a sort of air-powered email. Systems were actually built in many cities to deliver post through metal tubes: Prague only shut its network down in 2002, after it was flooded. On a smaller scale, such pneumatic pipe-networks are still in use in thousands of offices and hospitals.
Like the airship, Concorde and the hovercraft, the pneumatic pipe looked to be one of those also-ran technologies which promised much but eventually faded away, to be replaced by something less glamorous, more mundane but economically more viable. Pneumatic networks were ripped out, to be replaced by courier firms. Plans to abolish Germany’s kitchens in the 1930s and replace them with a food delivery system based on pneumatic tubes, with ready-prepared meals delivered to the Hausfrau from some Nazi version of a Brake Brothers factory, proved a casualty of war.
There are signs, however, that pneumatic technology may yet have its day. In an increasingly crowded world, where fuel is becoming more expensive and traditional transportation technologies seem stuck forever in the 1970s, a rethink is certainly needed.
Take the transportation of food, for example. Drive down any European motorway and at least half the available road space will be occupied by large trucks carrying cargo. Many of these are ferrying food from supplier to warehouse to supermarket. Trucks are noisy, slow, dirty, inefficient and dangerous. Could a better way be found?
Five years ago, an organization called Foodtubes was set up in Britain to look into using metre-wide pods propelled by compressed air to deliver food to supermarkets. One large firm was interested, but the upfront costs were prohibitive. Yet if someone could build a viable prototype and show how costs could plummet, then, says consultant Jonathan Carter, quoted in New Scientist, Foodtubes “could snowball.”
While Foodtubes hopes compressed air could take freight off the roads, tycoon Elon Musk is planning to use a different system to slay three old technologies at once — the conventional railway, the highway and the short-haul flight.
Musk, a South African-born entrepreneur-engineer now based in California, is said to be the inspiration for Robert Downey Jr.’s take on Iron Man. Unlike his fellow billionaires such as Bill Gates and Sergey Brin, Musk is unusual because he makes stuff as well as software. He first invented PayPal, then founded the SpaceX private rocket company (he says he wants to retire to Mars) and the Tesla electric car firm.
Last week, to much fanfare, he unveiled a new way to move people around. The solar-powered “Hyperloop” will cover the 644 kilometres from Los Angeles to San Francisco in just 30 minutes, travelling at 1,448 kilometres per hour. Passengers will step into smallish pods (it seems transport systems of the future must always involve pods) that will then be moved into a tube containing a near-vacuum. Propulsion would come from linear-magnetic-induction motors built into a pair of rails in the floor, with the pods floating on a cushion of compressed air jetted out through skis on their bases.
The Hyperloop is thus a mixture of maglev train and pneumatic railway (the concept is a modified version of the “vactrain” — using evacuated tunnels as low-resistance conduits for ultra-high-speed trains). Skeptics point to potential problems: compressing air makes it hot, and some way must be found to dissipate this heat. Buying the land on which to erect the “tracks” — which will be on pylons above street level — will also, they say, cost a lot more than Musk thinks.
To many, in fact, the Hyperloop sounds utterly mad — one of those “nice idea, but it will never be built” fantasies. But Musk has form for getting things done. His rockets have flown cargo to the International Space Station; his electric cars are by far the most convincing yet built, and PayPal has become the default global electronic payment system. He says the Californian system would cost $8 billion US; if he is even half right, this would massively undercut the dismal conventional high-speed rail network proposed for the state.
If the Hyperloop does get built, it will be a case of back to the future. In the 1930s, there was what American science historian Holly Kruse calls a “utopian discourse about the pneumatic subway.” It was not just the Nazis with their ready meals — people dreamt, among other things, of building submarine tunnels across the Atlantic to carry people from New York to Britain in a matter of hours.
Nor is Musk the first engineering genius to come up with the idea of a silent, hyper-fast transportation system relying on compressed air. In 1799, George Medhurst, a British engineer, patented an “Aeolian engine” to use “the well-known and wonderful properties of common air” to drive close-fitting, piston-like fourwheeled carriages at 97 km/h along underground tunnels some two metres across. The compressed air would be created by steam pumps.
Medhurst’s Georgian Hyperloop was never built, but 40 years later Isambard Kingdom Brunel, the Elon Musk of his day, also wondered whether pneumatic railways could be made to work. Existing steam trains were quite expensive. Brunel thought compressed air, generated centrally, could slash operating costs.
Small experimental pneumatic railways had already been built in Ireland, but Brunel improved on the design. Instead of sitting in a tube, the “pods” (actually carriages) ran on conventional rails; horizontal pistons projecting from their undersides were driven by compressed air generated in trackside pumping stations, fed via a metal tube laid across the railway ties.
The Atmospheric Railway was built between Exeter and Newton Abbot in Devon. And it really did work — in 1847, passengers could experience speeds of near 113 km/h in virtual silence. The problem was the leather contraption that Brunel used to keep the air sealed away. First it rotted in the sea breeze; when treated, it was eaten by rats. In the end, the Atmospheric Railway turned out to be even more expensive than conventional steam power.
In 1910, the rocketry pioneer Robert Goddard unveiled plans for a 1,609 km/h maglev-vac train. But by then, steam trains had become faster and more efficient, with diesel and electric power on the horizon, and the pneumatic railway was forgotten for 100 years.
Today, pneumatic power has the whiff of steampunk about it, with its old-fashioned idea of buried tubes slicing silently under our cities and through our buildings. But the world does desperately need a new transportation technology. The airports are full, high-speed conventional rail is horrendously expensive and contentious, ships are as slow as they ever were, and the roads are becoming a global nightmare, with a million people killed on them every year.
With a world of eight-billion people looming, we face global gridlock. Perhaps the solution is as simple as a puff of fresh air.