Shot Into The Air
The aviation catapult has replaced the battleship’s big gun as the sharp end of American naval power. In 2.5 seconds a modern steam catapult can accelerate a 78,000-pound airplane, which would otherwise require a quarter-mile for takeoff, to 160 mph within 300 feet. Using a ship’s four catapults, a well-trained crew can launch two aircraft and land one every 37 seconds in daylight. But disable an aircraft carrier’s catapults, and the $4.5 billion, 105,500-ton behemoth becomes an impotent liability. Perhaps the most surprising thing about this device is that it’s a century old. And most of its current features were present at the very beginning.
The need to accelerate aircraft quickly at takeoff has been a problem since the early days of heavier-than-air flight research. On January 8, 1894, a decade before the Wright brothers’ first powered flight, two of America’s leading scientists watched workmen hoist a 10-pound aircraft model to the top of a framework 25 feet above the Potomac River. With Alexander Graham Bell looking on, Samuel Pierpont Langley, the secretary of the Smithsonian Institution, was expecting to take a historic step forward in his attempt to build a powered man-carrying airplane. When its twin steam-driven propellers reached 600 rpm, Langley gave the signal for the model’s release. “Aerodrome No. 4” splashed straight into the river.
Langley had encountered a basic fact of aeronautics that would challenge every aircraft designer from then to the present day. As Langley put it, “It is necessary for an aerodrome [i.e., airplane], as it is for a soaring bird, to have a certain considerable initial velocity before it can advantageously use its own mechanism for flight, and the difficulties of imparting this initial velocity with safety are surprisingly great, and in the open air are beyond all anticipation.”
The device that Langley designed to get around those difficulties was the ancestor of every aviation catapult. The aircraft was held firmly by a clutch on a light “car” running on a pair of rails 5 feet apart and 80 feet long. A cable ran from helical trolley-car springs to the forward end of the track, passing through pulleys that multiplied its speed, then back along the track to the front of the car. As is true with just about all catapults, Langley’s aircraft was pulled, not pushed, into the air. When the car neared the end of its run, it struck a trigger, opening the clutch and supposedly allowing the aerodrome to lift off.
A catapult is a device that stores a large amount of energy and imparts it to a projectile—in this case, an airplane—in a short period of time through a moving mechanical intermediate. To be effective, an aviation catapult needs a convenient way to store energy and an efficient way to transmit it to the airplane. Over the years storage methods have run the gamut from physical to chemical to electrical, while transmission methods have included pulleys, pistons, and direct drive.
On October 7, 1903, a 750-pound steel-frame flying machine, the Great Aerodrome , sat on Langley’s houseboat-mounted catapult, its tandem 50-foot wings vibrating to the throb of its 52.4-horsepower gasoline engine. At a signal, a workman cut the restraining rope, and the catapult’s springs pulled the car forward with a thrust of 400 pounds. Charles Matthews Manly, Langley’s 28-year-old assistant and volunteer pilot, has left us an account of the world’s first manned catapult launch:
“No sign of jar was apparent when the machine was first released, but with lightning-like rapidity it gathered its speed as it rushed down the sixty feet of track, the end of which it reached in three seconds, at which time it had attained a speed of something over thirty-two feet per second [about 22 mph]. Just as the machine reached the end of the track the writer felt a sudden shock, immediately followed by an indescribable sensation of being free in the air, which had hardly been realized before the important fact was intuitively felt that the machine was plunging downward at a very sharp angle… . The tremendous crash of the front wings being completely demolished as they struck the water had hardly become apparent before he found himself and the machine plunging downward through the water.” The catapult’s outrigger struts, which steadied the craft and were meant to release when it reached the end of the track, had jammed, dragging the nose of the Aerodrome down and killing its lift. It slid into the river “like a handful of mortar.”
But the principle was sound, and Langley tried again on December 8, 1903. This time the Great Aerodrome collapsed before reaching the end of its catapult run, an accident that was originally blamed on another catapult failure, though it is now usually attributed to structural deficiencies in the Great Aerodrome itself. There would be no third chance for Langley. His money had run out—much of it spent on the $50,000 catapult—and so had his time. Nine days later the Wright Flyer lifted off from a simple $4.00 monorail at Kitty Hawk.
The Wrights’ Kitty Hawk launcher was not a catapult, just a launching rail, with the plane picking up speed under its own power—aided by a stiff 22-mph headwind that boosted its apparent speed above the 27 mph needed for take-off. When they found that their airplane would not fly in calm conditions, however, the Wrights achieved another milestone by building the first successful aviation catapult. The power source was gravity, stored by lifting a 1,200to 1,400-pound weight to the top of a 20-foot tripod. A half-inch cable ran from the weight to a pulley at the foot of the derrick, then to the front of the monorail track and back to the airplane. The 16.5-foot drop of the weight was multiplied three times by the pulley system to produce a run of 50 feet. It was another example of the Wrights’ genius for utilitarian simplicity.
The Wrights believed that all future heavier-than-air flying machines would be catapult-launched. As aero engines became more powerful, though, European pilots were able to take off unassisted on pneumatic tires. Even the Wrights substituted wheels for their catapults. Yet the catapult was not destined to become a relic of the age of underpowered engines. It survived, and eventually flourished, in a specific application where the other item needed for unassisted takeoffs—a long runway—was not available. That application was naval aviation.
In March of 1912 Orville Wright wrote to Capt. Washington Irving Chambers, the head of what little there was of American naval aviation. It was less than a year since the Navy had bought its first airplane, and officers were still figuring out how to use the new technology. As a temporary expedient, a platform could be constructed on the deck or turret of a cruiser or battleship to serve as a runway, but everyone knew it was a stopgap that would not be satisfactory for wartime use. Large flight decks on dedicated aircraft carriers represented a better approach, but such ships (which Chambers called “floating garages”) would be expensive and therefore limited in number. For smaller ships, Orville Wright suggested a different solution: “The system of launching the machine with a catapult would be the easiest.”
The Navy built a catapult based on the system it used for launching torpedoes. Compressed air, a power source available on every major American warship, was applied to a piston, whose speed was multiplied by a factor of seven with a system of sheaves. (Expanding gas working on a piston has remained the power source of most aviation catapults to this day.) On July 30, 1912, Lt. Theodore G. (“Spuds”) Ellyson attempted a catapult launch from the USS Santee . Unfortunately, the Navy had not learned from Langley’s downfall.
The Curtiss A-1 seaplane rested on the catapult car with its nose free to rise as it rushed down the track. As the wings’ angle of attack increased with the abrupt release of compressed air, the sudden lift caused the airplane to rise, stall, and plunge into the water. (Ellyson managed to escape from the wreck without serious injury.) The solution to this problem was a nose hold-down and a cam arrangement that opened the compressedair valve gradually. Ellyson made the Navy’s first successful catapult launch on November 12, 1912, from a stationary coal barge, and on November 5, 1915, Lt. Cdr. H. C. Mustin made the first catapult launch from a moving ship.
Beginning in April of 1916, the Navy mounted 103-foot catapults on the armored cruisers North Carolina , Huntington , and Seattle . The catapults took up about 20 percent of each cruiser’s weather deck, masking half its main battery. They were removed in 1917, when America entered World War I, a war that saw little advance in catapult technology. Given the low weight and takeoff speeds of the era’s biplanes and the increasing power of their engines, there were easier ways to launch aircraft, even from ships. The Royal Navy dallied briefly with a 60-foot compressed-air catapult mounted on a dedicated ship aptly named HMS Slinger , but it soon concentrated on developing the first purpose-built aircraft carriers.
One wartime innovation did come about in the course of developing the Navy’s unmanned flying bomb, a direct ancestor of the German V-1 of World War II. After trying unsuccessfully to launch this early cruise missile from a 150-foot catapult utilizing the Wright brothers’ principle, dropping a three-ton concrete block 30 feet, the developers commissioned Carl L. Norden to design a new catapult. Norden’s device stored energy in a heavy flywheel spinning at 2,175 rpm. He used a clutch-and-drum arrangement to impart a constant acceleration to the catapult car, enabling it to launch the 1,950-pound drone at 100 mph in 150 feet. The war ended less than two months after the first successful launch, on September 23, 1918, so the project was terminated. Norden went on to develop his famous bombsight, which was used in World War II, and the flywheel launcher was forgotten.
Then, on July 21, 1921, in a dramatic demonstration of the traditional warship’s vulnerability, U.S. Army Gen. Billy Mitchell bombed and sank the captured battleship Ostfriesland . The exercise showed that without airplanes to defend them, warships were highly vulnerable. The shipboard catapult became a politically driven technology. Within three months the Navy unveiled an advanced catapult and promised that all battleships would rapidly be supplied with catapults to launch, as The New York Times put it, “their own airplanes to fight those of the enemy in their own element.”
The experimental 28,000-pound catapult mounted on the Maryland was 79 feet long and could launch a 3,500-pound aircraft at 48 mph. Within a few years a 7,500-pound aircraft could be launched at 60 mph in 55.5 feet. By the mid-1920s the Navy was operating catapults routinely, first from battleships and then from cruisers. The service had arrived at the basic setup that would govern catapults on the cruisers and battleships of major navies until the end of World War II.
The launchers were mounted on turntables positioned clear of the ships’ guns. They could be swung out 90 degrees on either beam, allowing most takeoffs to be made in the direction of greatest opposing wind. Using compressed air, and later gunpowder packed in eight-inch shell casings, to drive the pistons, they could handle airplanes up to 7,500 pounds. That seemed enough for the limited scouting and gunnery spotting the planes were designed to do. The concept of the catapult-launched fighter plane was quietly dropped, as the future of naval aviation lay with the aircraft carrier, whose deck would provide enough takeoff room for the fighters of the day.
The Navy’s first experimental carrier, the Langley , commissioned in March of 1922, originally mounted compressed-air catapults. They were removed in 1928 after three years of disuse. Takeoffs from Langley ’s 523-foot flight deck were no problem, even at the ship’s low speed of 15.5 knots (which provided that much of an apparent wind, added to the natural wind into which the ship sailed). The catapult seemed permanently banished from first-line naval aviation with the launch in 1925 of the Navy’s first nonexperimental aircraft carriers, the majestic 43,055-ton Lexington and Saratoga . Taking advantage of the ships’ 30-knot-plus speed, their planes became airborne in about 400 feet. That left the remainder of the 888-foot flight deck available as a deck park for more planes, something essential if all the aircraft in a strike were to take off in quick succession.
The hangar decks of the turboelectric Lex and Sara were initially fitted with Norden-style flywheel catapults. Energy generated by electric motors was stored in six-ton flywheels and transmitted to the catapult through a cone-type friction clutch. The cable transmitting the power ran off a tapering drum, keeping acceleration as constant as possible to avoid giving pilot and plane too much of a jolt. These devices could launch 10,000-pound twin-float seaplanes at 55 mph, but clutching was a continuing problem for the fast-turning flywheels. The catapults were rarely used, and soon they were removed. Deck launches worked fine for the airplanes of the day, and few Navy officers seemed concerned about what would happen when carrier airplanes got a lot bigger, faster, and heavier.
For a period during the 1920s and 1930s the catapult initiative passed to Germany, the one major maritime nation with no blue-water navy at all (this was one of the terms of the Versailles Treaty). Instead, a private German firm used catapults commercially, in the only nonmilitary development of catapults since the Wright brothers’ day. Beginning on July 22, 1929, the airline Deutsche Lufthansa catapulted small mail-carrying seaplanes from the passenger liners Bremen and Europa , launching them as far as 1,272 miles from their destination. This procedure cut more than 40 percent from the normal four-day, 18-hour transatlantic mail time.
In 1932 the writer Eric Hodgins captured some of the wonder that this technology held for a generation most of whose members had rarely even seen an airplane up close: “Now, with course changed slightly and speed reduced, the whole ship waits while the airplane engine roars. In a moment the pilot’s arm will drop and the catapult carriage, driven by 30 atmospheres of compressed air (supplied by the tireless engine room), will shoot the plane over the side. It is a sight that must not be missed—so genuinely exciting that no ship’s officer is blasé enough not to see it if he is lucky enough to be off watch. Now the pilot’s arm drops, there is a final roar from the engine, the hand of an engineer wrenches a valve, the compressed air tanks hiss like ten thousand cobras, and the plane is suddenly no longer of the ship but of the air. It banks sharply, circles twice, waves a goodbye, and is gone.”
The next step was airmail clear across the Atlantic. Even the most efficient airplanes of the day lacked the range to carry a reasonable payload over the shortest transatlantic distance, 1,835 miles between Bathurst, Gambia, and Natal, Brazil. However, if mail-carrying seaplanes could rendezvous at sea with catapult-equipped ships for refueling, the gap might be bridged.
In May of 1933 an eight-ton Dornier Do J II “Wal” flying boat made the first catapult launch from the Westfalen , a 428-foot steamer with a massive fixed catapult occupying most of her foredeck. (The plane had landed alongside the ship and had been hoisted aboard.) Regular service began in February of 1934. By abandoning the turntable catapult, with its limited throw-weight, and acquiring dedicated catapult ships, Lufthansa had greatly increased the permissible size of its planes and the distance and reliability of their service. Eventually the 110-foot catapults accelerated four-engine, 38,691-pound Blohm und Voss Ha 139B floatplanes and 44,092-pound Dornier Do 26 flying boats, machines eight times as heavy as the scout planes then being handled by the U.S. Navy’s turntables.
Lufthansa’s catapults could achieve 95 mph in two seconds. The system was neither safe enough nor comfortable enough for passengers, but it was sufficient to expedite regularly scheduled mail service between Germany and Buenos Aires via Africa. Lufthansa performed 328 catapulted crossings, including a few flights over the North Atlantic, before the arrival of World War II ended the service and returned the aviation catapult to its military role.
While Germany was developing seaborne catapults, Britain reconsidered the old idea of land-based launchers. The Royal Air Force calculated that a bomber, once airborne, could carry 8,000 pounds to its target, but the same plane could lift only 3,400 pounds with a standard 700-yard unassisted takeoff. In 1931 the RAF catapulted a 14,000-pound Vickers Virginia bomber to 60 mph in three seconds. The idea was eventually abandoned as bomber takeoff performance was addressed with a combination of controllable-pitch propellers, high-lift devices, and the extension and paving of runways. But throughout World War II, RAF four-engine bombers carried the serious weight penalty of being built extra rugged to withstand catapult launches.
Japan entered that war with the only modern dedicated catapult warships, the 15,200-ton, 35-knot heavy seaplane cruisers Tone and Chikuma . The entire aft portions of their weather decks were devoted to catapults and aircraft, including a spacious hangar accommodating five seaplanes. To maximize the value of these ships, the Japanese designed the world’s best catapult scout plane. The Aichi E13A1 “Jake” had a range of 1,300 miles and could stay aloft for almost 15 hours. It was 480 hp more powerful and 70 mph faster than its U.S. Navy counterpart, the Curtiss SOC. The first Japanese airplane over Pearl Harbor on the early morning of December 7, 1941, was a “Jake” catapulted from the Chikuma .
Other applications of catapults proved less useful. Of all the naval powers, Japan alone persevered in the interwar delusion of the submarine-launched scout plane, entering World War II with 11 catapult-equipped submarines. On September 9 and again on September 29, 1942, a seaplane assembled on deck from 12 components and launched from the 66-foot compressed-air catapult on the forward deck of submarine I-25 dropped the war’s only enemy bombs to land on the contiguous United States. The total damage: seven trees destroyed in an Oregon forest.
Another project that ended up being abandoned was the use of catapults in the merchant marine. On September 27, 1940, after Britain had lost more than 90,000 tons of shipping in two months to German long-range Focke-Wulf 200 Condor maritime bombers, Winston Churchill, recently installed as prime minister, fired one of his famous “minutes” at the Admiralty: “What have you done about catapulting expendable aircraft from ships in outgoing convoys?”
Expendable was indeed the word—for the planes, at least, though it was hoped that their pilots could survive. With no facilities for landing planes on deck, a flight launched out of range of land could end only with a parachute jump or by flying the plane directly into water that was sometimes so cold that sailors who fell overboard died before their ships could stop and lower a boat.
Each of the 70-foot catapults that had been hurriedly mounted on the fo’c’s’le heads of the merchant ships was powered by a cluster of 13 rockets. Using multiple rockets was risky, as some might misfire. The worst situation for all naval catapult pilots is not a total malfunction but a “cold cat,” a partial failure that dumps the aircraft with insufficient flying speed into the sea under the ship’s forefoot. On the plus side, rockets exerted their force evenly over the run, so pilots remarked on the absence of an initial jolt.
On August 3, 1941, the Royal Navy lieutenant Robert W. H. Everett took off from the Maplin in a worn-out Hawker Hurricane fighter, shot down a shadowing Condor, and survived a ditching in the Mediterranean with the help of an inflatable “Mae West” life preserver. The case for high-performance shiplaunched aircraft was proved, and catapulted planes recorded five more kills before the end of the year, but throwaway airplanes were at best a stopgap. To protect convoys, ships with true flight decks were needed immediately, and in quantities that could never be met with big, expensive fleet carriers. A way had to be found to put flight decks on smaller ships, and the catapult played a key role in meeting that need.
An urgent problem facing naval aviation as World War II began was that planes were getting too big. The heavy carrier aircraft of the early 1940s could take off from the decks of 800-foot, 30-knot fleet carriers but not from the 500-foot decks of the far more numerous 19-knot escort or “jeep” carriers. The Grumman TBF Avenger, the standard Navy bomber of the day, could not lift a military load from a jeep carrier, and even with no load, it could not take off unassisted with full fuel. To solve the problem, the Navy revived an almost abandoned technology, the flush-deck catapult.
Back in September 1931 the Navy had started designing a launcher whose mechanism would be contained below the launching deck, with nothing protruding to interfere with the use of the deck for regular takeoffs. At first these were powered by compressed air or gunpowder, but by 1934 the Navy’s thinking had switched to hydraulics. In August of 1939 the first takeoffs were made from hydraulic flush-deck catapults on the newly commissioned Yorktown and Enterprise . For the first time airplanes could taxi into launching position and then be catapulted on their own wheels in rapid sequence.
Unfortunately, no one seemed interested. The Navy was still thinking in terms of big, fast fleet carriers, which at first could get along quite well without catapults. As late as April 1943 the captain of the Enterprise asked to have its catapult removed. The advent of the smaller, cheaper, quickly built jeep carriers—115 of them, as against 30 fleet and light fleet carriers—changed all that. They made almost all their launches with flush-deck catapults, and their success led the Navy to take a second look at catapults for fleet carriers as well, as a space-saving measure: By catapulting the first few planes of each strike, the big ships could save enough space for a deck park. The Army Air Forces equipped all its fighter planes destined for the Pacific Theater with catapult fittings, and many of them were launched from carriers. The naval historian Norman Friedman called the rise of the catapult perhaps the most important wartime development in carrier operations.
Immediately after the war the early jets, with their sluggish takeoff performance, made the hydraulic flush-deck catapult mandatory even on the largest carriers. A hydropneumatic engine located below the hangar wound a steel cable attached to a trolley. The trolley, which pulled the aircraft, ran on a track flush with the flight deck. It was Professor Langley’s pulleys, cable, and car all over again, though the power source had changed. As takeoff weight increased, hydraulic catapults were upgraded. The most powerful hydraulic catapult could launch a 15,000-pound airplane at 120 mph or a 62,500-pound airplane at 70 mph. These launchers were operated at increasingly dangerous pressures, eventually leading to tragic results. On May 26, 1954, the port catapult accumulator aboard the Bennington burst, releasing hydraulic vapor under tremendous pressure. The explosion killed 103 men and injured 201 others.
The hydraulic catapult had reached its limit, but the demand for power had not. The Grumman F9F Cougar, the standard Navy fighter at the time of the explosion, weighed 21,000 pounds fully loaded. The Douglas A-3 Skywarrior, which had first flown the year before, would reach a gross weight of 82,000 pounds, well beyond the capacity of any conceivable hydraulic catapult. Fortunately, the Royal Navy had long recognized the limitations of hydraulic catapults, and by 1950 Comdr. Colin C. Mitchell had designed and built an entirely new type of launcher, based on one of the Industrial Revolution’s oldest motive fluids. Mitchell’s steam catapult, as refined over the next five decades, can still be seen aboard today’s Navy carriers.
Abraham Lincoln –class carriers each mount four C13 Mod-1 catapults. Together they weigh 1,913 tons, as much as a World War II destroyer. The heart of each catapult is a pair of parallel slotted cylinders, each 21 inches in diameter and 325 feet long. They lie in a trough 333.6 feet long, 5.2 feet wide, and 3.8 feet deep. Each cylinder contains a rodless piston, and the two are joined rigidly together and connected to a wheeled shuttle running on a track directly beneath the flight deck. A spreader connected to the shuttle pulls the airplane by means of a launch bar attached directly to the nose-wheel strut of the airplane. Steam stored in accumulators and released on command moves the pistons to drive the catapult directly. Direct drive provides a tremendous gain in strength and simplicity—no piston rod to occupy hundreds of feet of space and no pulley or cables to stretch or break.
What does a steam catapult look like in operation? As the previously launched airplane climbs away, the retraction engine pulls the shuttle and the attached steam pistons back to the aft end of the catapult, ready for the next plane, which now taxis forward. The yellow-shirted plane director guides it to the waiting shuttle, and the launch bar on the plane’s forward landing gear strut is locked into the shuttle. The pilot releases his brakes and applies full power.
The airplane is now “tensioned,” straining against the holdback, a link attached to a point on deck. The holdback restrains the airplane until the catapult generates sufficient force for a safe launch. Once the plane is tensioned up, the pilot will be careful not to retard his throttle, even if there has been a “hangfire” and the catapult has failed to launch. Should the catapult then fire with the airplane’s engine at less than full power, the plane would strike the water in front of the ship. In case of a hangfire, the pilot will reduce power only if the deck safety observer demonstrates his confidence that the operator has turned the emergency cutoff valve. He does this by standing on the catapult directly in front of the airplane, where he would be killed if the catapult fired accidentally.
All goes smoothly on this launch. The pilot puts his helmet firmly against the headrest and salutes the catapult officer. After one last check, the operator presses the “fire” button. Below the flight deck, the launch valve begins to open, admitting steam into the two cylinders and driving the pistons, the shuttle, and the airplane forward. The amount of steam forced into the cylinders, and thus the catapult’s acceleration, has been determined for each launch on the basis of the type of plane, its takeoff weight, the wind speed and direction, and even the air temperature.
In his evocative 1996 book Ironclaw: A Navy Carrier Pilot’s War Experience , Sherman Baldwin recalled his sensations during a night launch: “My head slammed against the ejection seat’s headrest, and I groaned audibly over the intercom as I strained against the rapid onset of G forces from the catapult shot. The instruments looked fuzzy as my eyeballs compressed into the back of their sockets, and the jet shook violently as it rattled down the catapult track toward the pitch-black abyss.”
In each launch, Baldwin was initially battered by about six times the acceleration of gravity (6g), though the acceleration quickly fell to between 3g and 4g. (For comparison, an ordinary car can accelerate up to 0.5g; the peak acceleration of a space-shuttle launch is less than 3g; and a roller coaster maxes out between 3g and 4g.) The plane must be built strong enough to withstand the initial acceleration, and pilots must be chosen and trained to overcome it. A steady acceleration with no sudden peak would be a great help in increasing payload and aircraft life and reducing the strain on pilots.
To soften the impact of the initial jolt, the Navy is testing a totally different type of launcher, the Electromagnetic Aircraft Launch System. EMALS is a combination of several existing technologies in which the cart that pulls the plane will be powered not by a steam-driven piston but by a linear induction motor (LIM).
An ordinary electric motor consists of a rotor, or magnetized armature, spinning in an electric field generated by stationary surrounding coils, known as the stator. If the coils are arranged in a straight line instead of a circle, however, the stator’s electric field will drive the armature straight ahead. This is called a linear motor, and it is a proven technology. In 1944 the Luftwaffe tested a LIM anti-aircraft gun, and LIMs have powered monorails at Euro Disney and on Vancouver’s rapid-transit system. They also drive roller coasters into the 100-mph range, and an experimental LIM-powered train has reached 250 mph.
The challenge in adapting the lim for catapults lies in the power source. In carriers slated for completion in 2014–15, a single launch will use 75 million foot-pounds of energy, enough to lift the Empire State Building 1.23 inches or hurl a Volkswagen Beetle 10 miles through the air. Not even the planned CVN-21 “all-electric” ships, with three times the electrical capacity of the current Nimitz class, could supply electricity at anything like that sustained rate, but by storing energy in advance, the catapult is able to supply a short but very intense burst.
For each catapult, the ship’s electrical system provides power to energy-storage devices. At the drop of the launch flag, the storage devices supply a controlled surge of current to power the linear motor. As the airplane moves down the track, segmented coils of the stator are turned off behind it and those ahead are energized. This saves energy and allows more precise control of the movement of the airplane than other methods. At the end of the run the shuttle is stopped, not by a water-brake, as with a steam catapult, but by electromagnetic forces applied in reverse. Now the storage devices draw power again to prepare for the next launch.
EMALS should deliver 29 percent more energy than the steam system and be capable of accelerating a 100,000-pound aircraft to better than 150 mph. Moreover, this acceleration can be controlled precisely to avoid the peak stresses of the steam system, prolonging aircraft life by up to 31 percent. With EMALS, the Navy expects to be capable of more sorties per day with fewer personnel.
An elegant system, but will it work at sea? Naval scientists have been studying the behavior of steam for two centuries, but much less is known about linear motors and sustained levels of high magnetism. Can shielding against magnetic fields prevent harmful effects on flight-deck personnel? Will the magnets disrupt the airplanes’ avionics? To prevent a leap forward from becoming a leap in the dark, the Navy is constructing a $145 million full-scale EMALS catapult system at its naval air engineering station at Lakehurst, New Jersey, the catapult capital of the world. In the meantime, construction of the first CVN-21 all-electric ships is progressing.
One way or another, aircraft launchers are certain to develop further to keep pace with the performance of the airplanes they propel. And as they do so, each one will owe at least a little bit to the thinking of Professor Langley as he watched his cherished model plunge into the Potomac more than a century ago.