Unfortunately, eeehhhhhhh it's on that site....and isn't a plausible theory....like, you can't realistically propel a craft with light because light is really, really, really....light. (it has no mass.)
In all seriousness, yes you can get thrust by spurting out EM waves. No, it is not significant thrust. It
does have a momentum, but that momentum is set by the energy of the wave (and obviously intensity AKA more of them does increase thrust linearly). There's nothing a fancy chamber can do to increase the base thrust. It can absolutely be a lasering chamber, which increases intensity and coherence, which improves efficiency, but it doesn't increase the base thrust.
So here's the momentum of an x-ray. You'll note that that is a very, very small number. That is just one photon, and you'll be sending out billions, perhaps trillions of them at once, but that's still just reducing that negative log by 9-12, and it's over 20. That's still imperceptible.
BUT! And it's a big ol' but. We already use this technology. Kind of. See, while the thrust of this device is so, so, incredibly low, its energy efficiency is so, so incredibly high. It's ludicrously efficient. So we've been using it since I believe the 80s? Just not with x-rays.
With xenon ions. And then there's the solar sail technology which we haven't been able to put into use yet but will probably be put into use at some point. Again, super, super effective, but really, really slow.
Oh, and one last thing. Every single time you see someone say "this can get you to *insert location in the solar system here* even faster!" they have NO IDEA how orbital mechanics works. The issue with intrasystem travel is NOT speed of craft, as most people assume. Speed of craft is completely irrelevant. You actually aren't even thrusting for the vast majority of the trip. The issue is that the best way to get there is either have insane acceleration and go straight there (would kill humans/crush cargo/use inordinate amounts of energy), or simply drift there using gravity. When we go to the moon, or another planet even, all you do is accelerate in the direction of your orbit around the current body at the right time such that you get captured by the target body, and then you thrust against the direction of orbit until you remain in a stable orbit. That's why it takes around 3 days, and that's why we haven't beaten that time on craft that are actually going to the Moon. New horizons made the trip in a little over 8 hours, but it didn't stop, because it couldn't. It was going way too fast, because it was going to Pluto. And I'm sure with conventional means we
could get a rocket there in under 4 hours. But we would not be staying for very long, and indeed would be on our way out of the solar system.
Okay, I lied, one more last thing. The only time in space travel when you would want to be accelerating constantly (most time efficient trip between two points) is when you're traveling intersystem. That is, when you're traveling from one solar system to another. It's a long, long ways between stars, and that's why you'd want to be accelerating constantly: constant positive acceleration with regards to the target until halfway there, and then constant negative acceleration after that. This is where a technology like this can work. However, again, it's completely bunk, and a better method is ion thrusters. Those do use mass however, so you'd be positive accelerating for some amount greater than half and negative the rest, and it would require a LOT of fuel, but this could eliminate the fuel need or at least reduce it. But again, the thrust from this pales in comparison to the ion thruster, which pales in comparison to a chemical thruster.
Okay, I lied again. Two more things, I promise. there's one last issue with this technology. Conservation of energy. Remember I said there's two ways light can carry more energy? Volume and wavelength. Either way you increase energy output this is going to be an issue, but one way is moderately worse than the other. See, when you shoot out light behind you, whatever is behind you is being bathed in that light. If it's x-rays, that's fine for Earth because we have a magnetoshpere and an atmosphere and whatnot, and x-rays aren't THAT powerful. But if you are going to use this form of propulsion, then you're going to be spewing out bundles and bundles of x-rays, which can be a LOT of energy. Accelerating a 1 kg object to 1 m/s/s in classical physics requires an input into the system of .5 joules. Accelerating a 2 Mg object (a little larger than the Apollo lander) that same amount would be 1 kJ. 1 m/s is not fast (walking speed is 2-3), so let's up it to 10: 100 kJ. how about 100 m/s?
10000 kJ. It just keeps getting exponentially bigger. You have to expend that much energy to get to that speed. That means that in order to reach top speed ASAP you have to shoot a LOT of x-rays behind you. The other option, of course, is to use denser waves (more energy/wave). That means you're hitting Earth with gamma rays. Or worse. You're creating a massive nuclear event, so you might as well use
nuclear propulsion.
the last, final thing (I promise) is that this experiment was debunked. See, they weren't getting thrust beyond the margin of error. Which was tiny. This story gets brought up every so often, but it's complete bunk. it's similar to that FTL neutrino story from a while ago (neutrinos arrived a couple nano-seconds before they should have), but it turns out it was within the margin of error because there was a timing issue. There is no thrust being provided by nothing, and the supposed thrust was so tiny as to be useless. It was probably a microwave leak if there was indeed any thrust provided. Maybe a gas leak even. If there was any water inside, microwaves resonate water really effectively (hey. that's how a microwave oven works!), and any tiny hole would have effectively been a tiny rocket. Any wind current in the chamber could have disrupted it and provided more thrust than the engine.
