Oscillococcinum — the homeopathic flu remedy concocted from duck or goose liver — doesn’t work. Its proponents may disagree vehemently, but the evidence for its lack of efficacy is compelling. In this it shares a direct parallel with the latest developments in propulsion technology.
Space, as Douglas Adams observed, is big. And the cost of getting from one place to another is — petrol price hikes aside — astronomical.
But the experimental EmDrive has sparked hopes of slashing those costs, leading space agencies such as Nasa and the China National Space Administration to build prototypes for testing — here on Earth and, perhaps some day, in orbit.
Cheap and efficient space travel would be a golden goose for any nation that cracked it, giving it a head start on the race to neighbouring planets and the mineral riches of the asteroid belt, before presumably ushering in a new age of interstellar exploration. And great hope is invested in the EmDrive.
Traditionally, propulsion has relied on Newton’s third law of motion — for every action, there is an equal and opposite reaction — and the all-important conservation of momentum that follows from it: when bodies in a closed system interact, the total momentum remains constant provided no external force acts on the system.
So, a rocket is able to move in space without having anything to push against by forcefully expelling part of itself — ignited fuel — in one direction, which propels the rocket in the opposite direction.
A useful way to demonstrate this is to put on a pair of roller skates, pick up a bowling ball and then hurl it away from you. This would cause you to roll backwards, without having pushed against anything.
On Earth, with gravity and friction acting on objects in motion, you would stop rolling fairly quickly. But up beyond the planet’s pull there is nothing to slow you down, so the more bowling balls you throw, the faster you zoot along on your space skates. In space, as in life, however, you will eventually run out of bowling balls.
This is why interplanetary space travel is expensive: you need to take a massive amount of fuel (bowling balls) with you to a) get up into and then out of orbit; b) accelerate to get to where you’re going as quickly as possible; and then c) flip the direction your rockets (roller skates) are facing so that you can decelerate enough to slip delicately into the orbit of your destination planet instead of overshooting or smashing into it.
This is where the EmDrive comes in. Short for electromagnetic field drive, the EmDrive is a fuel-free engine that is purported to produce thrust by bouncing an electromagnetic signal around inside a cavity within the engine — without ejecting any mass at all. No balls required.
So not only would you save money on fuel, but you’d save on your total mass, too, as you sailed your ship sveltely across the solar system.
Before being taken seriously by Nasa and the like, the EmDrive had been ridiculed by establishment physicists because it supposedly violated Newton’s third law — by not expelling anything, so no conservation of momentum. It was bunkum, they said. Quackery. A wild goose chase. The equivalent of strapping into roller skates while holding a microwave, and instead of throwing it anywhere, just pressing the “reheat” button and waiting.
This is reminiscent of the critics of the OG rocket scientist Robert Goddard, who was mocked by The New York Times in a 1920 editorial, which said of his ideas that thrust could be produced in the vacuum of space: “He seems to lack the knowledge ladled out daily in high schools.” (The paper eventually issued an apology, a day after the launch of Apollo 11, in 1969.)
Undeterred and encouraged by history, proponents of the EmDrive have built prototypes that seemed to show a minuscule amount of thrust being created by the physics-busting engine. This hint of success has in turn prompted further study, and even plans for orbital tests by the leading space agencies.
But results from new experiments presented at the Space Propulsion 2018 conference in Seville, Spain, three weeks ago, have poured some very cold water on their dreams.
Martin Tajmar and his team from the Institute of Aerospace Engineering at the Technische Universität Dresden showed that in extensive testing of the EmDrive, no thrust had been created at all. Previous positive results they attributed to interactions with the Earth’s magnetic field.
And so the golden goose of space travel is finding itself not just reheated, but properly cooked. Because, just like oscillococcinum — the homeopathic remedy that has been shown to be no more effective than sugar pills — the EmDrive does not work.*
* The Mail & Guardian looks forward to issuing an apology to the creators of the EmDrive in 2069.