On Their Own Steam

If you ride the train in Britain’s West Country, between Exeter and Torquay, you will pass some distinctive early Victorian brick buildings, some still with tall chimneys. Most people looking at them will not guess that they are linked with the history of naval aviation, but in fact they represent the first of two innovations in aircraft carrier design that have a connection to revolutionary, if unsuccessful, British rail technology.

In the 1840s, rail was still a spluttering, puffing, red-faced infant. Heavy and inefficient, steam locomotives worked hard to haul their own weight over flat terrain, and could tolerate only shallow grades. Building a railway in hilly ground was grueling work for an army of laborers.

So the invention proposed by Jacob Samuda, a London ironmaster (and other pioneers) looked attractive, and would-be shareholders lined up to pour money into it. Big static pumping engines—everyone knew how to make those. Hook them up to an air pump, then connect the pump to an iron tube midway between the rails. In the top of the tube was a continuous slot sealed by an ingenious valve. The train had no locomotive: the lead car had a piston, running in the tube. With the pump sucking out the air ahead of the train, atmospheric pressure behind it would push it along. A chimney-like smokestack allowed smoke to escape the boiler.

The atmospheric railway worked for a season or two. Its Achilles heel was the valve seal, which could not endure rain, snow, dirt, or summer heat. None of the atmospheric lines lasted long, and conventional locomotives were improving rapidly. A century later, steam locomotives were in the last years of their prime, and the world’s new motive technology was the jet engine. Combined with the swept-back wing, it promised far higher top speeds for military airplanes—but that also resulted in higher speeds on landing and takeoff, a huge problem for aircraft carriers, which were already among the longest ships afloat.

Many fixes were tried. The U.S. Navy Bureau of Aeronautics ordered the F7U Cutlass, a tailless fighter designed to land and take off at an extreme nose-high angle for high lift. It was such a nasty piece of work that one Navy test pilot, told he would be flying it for the Blue Angels, resigned on the spot. There was the variable-sweep Grumman Jaguar—fat, slow, complex, and even more ill-mannered than the Cutlass. BuAer ordered prototypes of supersonic seaplanes and tail-sitter vertical-takeoff fighters. None of those worked either.

Part of the practical solution to the problem was the British-invented steam catapult—simpler and with a longer stroke than the pre-war hydraulic and electric cats, and far more powerful. It was the atmospheric railway with the pressure gradient reversed and the linear valve flipped upside down, and its inventors gave credit to its Victorian ancestor in a 1953 interview with Popular Mechanics. As the steam cat arrived, so did Navy swept-wing fighters.

The steam catapult consigned another U.S. Navy project to the pages of dusty magazines: Westinghouse’s Electropult, a catapult based on a linear motor. It worked, but it was heavy and inefficient.

A few years later, the British public was as excited about the invention of the hovercraft as their ancestors had been about the atmospheric railway. In 1966, my father took me to the Hovershow, at Gosport on the south coast, starring the world’s biggest hovercraft, the 37-ton SRN.3. It also featured a length of sub-scale track for the next step in rail transport: the Hovertrain, lifted by an air cushion and propelled by a linear electric motor. The motor, developed by pioneering electrical engineer Eric Laithwaite, drove the train without physical contact with the track.

The Hovertrain got as far as a large-scale working prototype, but the project stopped in 1973, and interest switched to maglevs—the train is both lifted and propelled by powerful electromagnets. But Laithwaite’s innovations with the Hovertrain’s motor pointed to much greater efficiency than the Electropult could achieve.

So perhaps it is not surprising that the U.S. Navy’s newest aircraft carrier, the Gerald R. Ford, its first since the 1950s to owe nothing to the long-lost atmospheric railways, has electromagnetic airplane catapults.

Bill Sweetman | READ MORE

Bill Sweetman is senior international defense editor for Aviation Week & Space Technology and has been an Air & Space contributor for 20 years. He is the author of more than 30 books, and has written about almost every aspect of aerospace and military technology.