EM Drive…

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NASA has recently announced that their research team has confirmed that the EM drive described above, when tested in a near vacuum, produced thrust.

The graph shows their raw data with error bars and the dotted line is their best fit line to show how the thrust in micro-newton (μN) is plotted against input power measured in watt (W). Let’s do some rough estimates based on the data above by rounding off their numbers to a convenient level. To produce 100 micro-newtons it seems to require 85 W; lets call this 100 W for ease. We could also call the thrust 0.1 milli-newton (one thousandth of a newton) because that might be easier to handle.

I was intrigued by the flying car that Roger Shawyer (the EM drive’s inventor) mentioned in the video above. I have been promised a flying car since I was a small boy and I am still waiting! If the EM drive is to lift a car it is going to need a bit more than 0.1 milli-newton. I want a flying Mini Cooper, which has an unladen mass of between 1340 kg and 1500 kg. Let’s keep the sums easier and assume that my flying car is built from less dense materials such that is has a mass of 1000 kg. If gravity on Earth, keeping my Mini on the ground, is 10 N/kg then I need a minimum force of 1000 kg × 10 N/kg = 10,000 N in order to take off.

The EM drive is claimed to produce one tenth of a thousandth of a newton if given 100 watts of power. How much power would it take to produce 10,000 N of force? 10,000 times 100 W would produce 1 N of force – that’s one million watts. So 10,000 times as much, or ten billion watts, would be needed to produce a force of 10,000 N. 1000 W is a kilowatt (KW), 1,000,000 W is a megawatt (MW) so we are going to need 10,000 times more or ten gigawatts (GW). How easy is it to produce ten gigawatts of power? This year the total solar power capacity of India is expected to reach 10 GW. That is 9 GW of commercial solar power plants and 1 GW of private, rooftop solar panels. It is a staggering amount of power and far more than could possibly be carried by a flying car.

It is possible that if further tests confirm that the EM drive really does produce thrust in a vacuum then a tiny constant thrust in the vacuum of space might enable a space vehicle to accelerate and reach seriously high speeds. Of course, to pass further tests the EM drive has to overcome the hurdle of breaking one of the most fundamental principles in physics; the conservation of momentum. That is a story for another time.