It was ten p.m. Rudolf Diesel had finished dinner and retired to his cabin aboard the SS Dresden, traveling from Belgium across the English Channel. His nightclothes were laid out on his bed, but Diesel did not change into them. The inventor of the engine that bears his name was thinking about his heavy debts and the interest payments that would soon come due. He couldn’t afford them. In his diary, today’s date—September 29, 1913—was marked with an ominous X.
Before the trip, Diesel had gathered what cash he could and stuffed it into a bag, together with documents laying bare the financial mess he was in. He gave the bag to his wife, telling her not to open it until a week had passed; she seems not to have suspected anything. Diesel stepped outside his cabin. He removed his coat, folded it, and laid it neatly on the ship’s deck. He looked over the railings, at the black and swirling waters below. And he jumped.
Or did he? While this seems the most plausible account of Rudolf Diesel’s final moments, it remains an assumption.1 Conspiracy theorists have speculated that Diesel was assisted overboard. But who might have had an interest in the impecunious inventor’s demise? Two possible candidates have been fingered. The conspiracies may well be entirely baseless; nonetheless, they help us understand the economic significance of the engine Diesel invented in 1892.
For context, rewind another twenty years, to 1872 and industrial economies in which steam supplied the power for trains and factories but urban transport depended on horses. That autumn, equine flu brought cities in the United States to a standstill. Grocery store shelves were bare; saloons ran out of beer; garbage piled up in the streets.2 A city of half a million people might have 100,000 horses, and each one liberally coated the streets with thirty-five pounds of manure and a gallon of urine every day. An affordable, reliable, small-scale engine that could replace the horse would be a godsend.3
The steam engine was one candidate: steam-powered cars were coming along nicely. Another was the internal combustion engine, early versions of which ran on gasoline, gas, or even gunpowder. But when Rudolf Diesel was a student, both types of engine were woefully inefficient: they converted only about 10 percent of heat into useful work.4
The young Diesel’s life was changed by a lecture on thermodynamics at the Royal Bavarian Polytechnic of Munich that discussed the theoretical limits to the efficiency of an engine. The 10 percent efficiency achieved in practice looked very low by the standards of the lecturer’s theorems, and Diesel became obsessed with the goal of making an engine that came as close as possible to converting all heat into work. Of course, in practice perfect efficiency is impossible—but his first working engine was more than 25 percent efficient, which was more than twice as good as the state of the art at the time. Today, the best diesel engines top 50 percent.5
Gasoline engines work by compressing a mixture of fuel and air, then igniting it using a spark plug. But compress the mixture too much and it can prematurely self-ignite, which causes destabilizing engine knock. Diesel’s invention avoids that problem by compressing only the air, and more so, making it hot enough to ignite the fuel when it’s injected. This allows the engine to be more efficient: the higher the compression, the less fuel is needed. Anyone who’s researched buying a car will be familiar with the basic trade-off of a diesel engine: they tend to be more expensive to buy but more economical to run.
Unfortunately for Rudolf, in early versions of his engine these efficiency gains were outweighed by reliability issues. He faced a steady stream of refund demands from unhappy customers; it was this that dug the inventor into the financial hole from which he never managed to escape. It’s ironic: the inventor of one of the most straightforwardly practical machines in the modern economy was motivated by an inspiring lecture rather than by money, which is just as well, since he failed to make any.
Still, he kept working to improve his engine, and it kept getting better. Other advantages became apparent. Diesel engines can use a heavier fuel than gasoline engines—specifically, a heavier fuel that’s become known as “diesel.” As well as being cheaper than gasoline to refine from crude oil, diesel also gives off fewer fumes, so it’s less likely to cause explosions.6 This made it particularly attractive for military transport: after all, you don’t want your bombs going off accidentally.7 By 1904, Diesel had gotten his engines into France’s submarines.8
This brings us to the first conspiracy theory around Rudolf Diesel’s death. In 1913 Europe, the drumbeats of impending war were quickening; the cash-strapped German was en route to London. One newspaper headline luridly speculated: “Inventor Thrown into the Sea to Stop Sale of Patents to British Government.”9
It was only after World War I that Diesel’s invention really began to realize its commercial potential, in heavier-duty transport applications than cars. The first diesel-powered trucks appear in the 1920s; trains in the 1930s; by 1939 a quarter of global sea trade was fueled by diesel. After World War II, ever more powerful and efficient diesel engines led to ever more enormous ships. Diesel’s invention, quite literally, is the engine of global trade. 10
Fuel accounts for about 70 percent of the costs of shipping goods around the world.11 You can see why the scientist Vaclav Smil reckons that if globalization had been powered by steam, rather than diesel, trade would have grown much more slowly than it did.12
The economist Brian Arthur isn’t so sure about that. Arthur views the rise of the internal combustion engine over the last century as an example of “path dependence”—a self-reinforcing cycle in which existing investments and infrastructure mean we keep doing things in a certain way, even if we’d do them differently if only we could start from scratch. As late as 1914, Arthur argues, steam was at least as viable as crude oil for powering cars, but the growing influence of the oil industry ensured that much more money was going into improving the internal combustion engine than the steam engine. With equal investment in research and development, who knows where breakthroughs might have happened; perhaps today we’d be driving next-generation steam-powered cars.13
Alternatively, if Rudolf Diesel had had his way, perhaps the global economy would run on peanuts.
Diesel’s name has become synonymous with a crude oil derivative, but he designed his engine to use a variety of fuels, from coal dust to vegetable oils. In 1900, at the Paris World’s Fair, he demonstrated a model based on peanut oil; and, as the years went by, he became something of an evangelist for the cause. In 1912, a year before his death, Diesel predicted that vegetable oils would become as important a source of fuel as petroleum products.14
This was, no doubt, a more appealing vision for the owners of peanut farms than for the owners of oil fields—and the impetus to make it happen largely dissipated with Rudolf Diesel’s death. Hence the second conspiracy theory to inspire a speculatively sensationalist headline in a contemporary newspaper: “Murdered by Agents from Big Oil Trusts.”15
There’s recently been a resurgence of interest in biodiesel. It’s less polluting than oil fuel, but it’s controversial—it competes for land with agriculture, pushing up food prices. In Rudolf’s era, this was less of a concern: the world’s population was much smaller, and the climate was more predictable. Rudolf was excited by the idea that his engine could help develop poor, agricultural economies. How different might the world look today if the most valuable land during the last hundred years wasn’t where you could drill for oil but where you could cultivate peanuts?
We can only guess—just as we’ll never know what happened to Rudolf Diesel. By the time his body bobbed up alongside another boat ten days later, it was too badly decomposed for an autopsy—indeed, for the crew to be willing to take it on board at all. They extracted from Diesel’s jacket his wallet, pocketknife, and spectacles case, which his son later identified. The inventor’s body was retaken by the waves.