combining greasing and RF engineering - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: May 09, 2020, 02:39:41 am
content: https://newatlas.com/aircraft/microwave-air-plasma-thruster/What do you think about this emerging technology? It's not the EM drive as far as I understand.Cool thing is, it uses a standard magantron as a source, making it accessible to hobbyists.Also, the waveguide dimensions are such for a commercial magnetron, that you can actually fabricate a decent one yourself (error due to weld corners will be small in comparison to higher frequency ones), and the magnetron itself is a beast so you can run it at a poor VSWRI actually expect really good results from careful brazing with correct gap spacing with the correct fluidity rating on the solder to make that. The dangerous part is the water cooled load.. be very careful with this part if you decide to research this.Perhaps this is what the thing made

author: OwO
author_rank: Super Contributor
timestamp: May 09, 2020, 04:12:36 am
content: I don't see how trying to heat up some conductive air with microwaves is any better than good ol' combustion. Electrical power is hard to come by because batteries do not have nearly the required energy density. If electrical power is available, why wouldn't you just drive a propeller with a motor directly (which surely has better efficiency than a magnetron?) Also thrusting by heating up air loses a lot of the energy, because hot air is expelled. In a traditional turbofan engine the jet "core" is very small, extremely high pressure in order to extract as much energy as possible from the heated air, and then it drives an ordinary propeller to actually produce most of the thrust.

author: coppercone2
author_rank: Super Contributor
timestamp: May 09, 2020, 05:24:53 am
content: Quote from: OwO on May 09, 2020, 04:12:36 amthe article has some words on efficiency, and this functions more like a jet engine, so it looks like it might have higher total velocityQuote

author: OwO
author_rank: Super Contributor
timestamp: May 09, 2020, 07:17:07 am
content: Right, it's not very hard to beat turbine engines or other combustion engines in efficiency. The killer though is that hydrocarbons have a few orders of magnitude more energy density than batteries. I can see this having specific niche applications though.

author: coppercone2
author_rank: Super Contributor
timestamp: May 09, 2020, 10:52:49 am
content: Quote from: OwO on May 09, 2020, 07:17:07 amAirbusE-FanelectricairplanePowerplant: 2 ×Electric motor, 30 kW (40 hp) each via eight-bladeducted fans,each producing thrust of 0.75 kN (266 lb st),Battery:Lithium-ion18650, with 207 Wh/kg per cell, total of 29 kWh at abatteryweight of 167 kgQuotethere is little fluid friction compared to a spinning thing

author: mikerj
author_rank: Super Contributor
timestamp: May 09, 2020, 02:20:51 pm
content: Quote from: coppercone2 on May 09, 2020, 10:52:49 amNot sure what point you are trying to make, but that just proves what OwO was saying. Jet fuel has an energy density of around 44 MJ/kg, about 12.2 kWh. 167kg of jet fuel will have a total energy of over 2000 kWh.