This is probably incredibly naive... but couldn't this all be put to bed by someone putting such a drive on a cubesat, lifting it into orbit, and seeing if it works under practical conditions?
Maybe Hawking and Milner should be considering this for Starshot?
1. The power requirements to run one of these would be larger than what would fit in a basic Cubesat form factor. It's not going to be a 1U, perhaps something like a 3U or 6U at best. Then there is the thermal management of the large power supply (getting rid of heat in a vacuum is not simple) which is even more equipment and mass. Those larger satellites are a bit more expensive.
2. A lot of the "Launch a 1U Cubesat for $100k" figures are for the launch itself. That ignores other stuff like engineer wages, legal, etc. and is mostly hyperbole. Launching two for $200k is much more common as the second one take a lot less time to put together once the initial R&D is done. Then these "$100k" Cubesats, capability wise, are fairly useless. Think Sputnik type satellites. Want a working payload? Prepare to do more R&D. Oh and Cubesats have about a 50% rate of actually operating in orbit. First one doesn't work? Now you need to find more money to launch another if you weren't lucky.
3. The number of people who are willing to throw millions after something that currently isn't explained by science and is a lot harder to debug when you don't have someone sitting next to it in orbit, when it can done on the ground for an order of magnitude cheaper, is very small. Most people interested in using this are waiting for someone to pay for the testing first. Hell most satellite engineers I know for now still believe it to either be a hoax or will end up being just a measurement error. So people are riding this out until there is more hard evidence.
Milner is a billionaire. He could easily pay for a full-size satellite lofted up by one of Musk's $5M reusable Falcon 9 boosters in a couple of years... Double that number to build the satellite if you have to and he could still find the change in his pockets...
EDIT: and once I convince Milner to finance this boondoggle can I sign you up to be my lead satellite engineer?
There are so many variables in leo. Magnetic field, ions, drag, radiation pressure from the sun, radiation pressure from the earth, variable gravitation fields due to the irregular nature of the earth, and I'm not a rocket scientist, so I'm sure there are many more I'm just not thinking of.
Plus, upthread someone cites the Eagleworks guys as preparing to test an EM drive capable of 'producing' 100uN (yes, microNewtons) of thrust; LEO's various weirdnesses are more than capable of fucking with that small of a delta-v.
Nitpick: that's the force supposedly produced by the engine, not delta-V. Delta-V, should the drive work, would be limited by the available electrical power.
A Falcon 9 can lift 10,000 kg to LOE (or more). Let's say we could get a simple Em-drive and basic satellite and solar panel in for under 100kg. (We can do better, but let's start there). That's 1/100 of the load, so (in theory) we could maybe pay 1/100 of the $60m cost for a Falcon 9 lift, or $600,000.
Half a million bucks plus some change, let's say.
Edit: Less if we can get on board a previously-enjoyed rocket!
You also have to add in the payload integration fees, testing (very, very expensive), the actual payload development, insurance, and also be in a launch configuration such that you can piggyback behind a payload taking up most of the F9 capacity.
I'd be astonished if the cost of this was less than $2-3M.
It takes about $100k to get a cubesat into orbit, plus costs for building the sat itself (custom fabricating a miniaturized drive plus a suite of sensors).
So not much, but the larger problem is we don't know how this drive works. Miniaturizing it could impact performance, as could other electronics in the satellite... given the unknowns it makes sense to let NASA do some more terrestrial due-diligence before going to space.
Maybe Hawking and Milner should be considering this for Starshot?