Building solar panels in space using resources gathered in space, and beaming the electricity is an idea recently floated by ULA to create a space economy[1].
RF/microwave engineer here: It would basically be a giant death ray in space, pushing that amount of energy through the air via microwave or laser is scary as shit.
Isaac Asimov has a great short story about robots manning such a satellite. One had a glitch whereby he totally worshipped the sun and beaming the energy was the purpose of his "temple". He wouldn't let the humans interfere, which ostensibly violated the laws of robotics until they realized the robot was effectively committed to saving the earth.
> At the Earth's surface, a suggested microwave beam would have a maximum intensity at its center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm2 outside the rectenna fenceline (the receiver's perimeter).[82] These compare with current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves, which are 10 mW/cm2,[83] - the limit itself being expressed in voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes.[citation needed] A beam of this intensity is therefore at its center, of a similar magnitude to current safe workplace levels, even for long term or indefinite exposure.
Even if we assume the conversion efficiency of microwaves are much better than solar, if the beam at its peak is less than 1/4 ordinary solar irradiation, why would this be more economical than ground-based solar?
If we're building space elevators, we could just cover the uninhabited desert parts of libya and algeria with hundreds of square km of photovoltaics...
Thanks for pointing that out. I'm always amazed to see how many people don't understand the ramification of pushing gigawatts through air. People who are worried about birds getting killed by wind turbines? You have no idea what this much energy will do...
Either the power density is high enough that it roasts anything crossing the beam path, or it's low enough that it's not appreciably higher than regular old sunlight flux.
That wiki doesn't mention it but I remember from an interview something about being able to fly higher and therefore faster because you don't need to worry about a combustion engine and necessary oxygen levels (could be way off though).
Lack of oxygen to burn fuel for the engines isn't the only thing that keeps civilian aircraft generally below 50,000 feet. There's a few other things.
For subsonic aircraft, the higher they go, the smaller the "coffin corner" gets. As air gets thinner, the speed of the aircraft where it will stall goes up (in terms of True Airspeed. In terms of Indicated Airspeed it basically stays the same which is why coffin corner is a thing). At the same time, the speed of the air moving around the wings gets faster and faster. This is because the aircraft has to move faster and faster through the air to move the same amount of molecules of air over the wings to create enough lift to hold the aircraft up. At a certain point, the stall speed of the aircraft equals the speed at which air moves over the wings at supersonic speeds. The aircraft stalls while simultaneously overspeeding. Bad things ensue. It is possible to design around this (see U-2), but for civilian aircraft, there's little benefit compared to flying at more typical flight altitudes.
The other issue is in regards to the length of time the pilots will stay conscious in the even of cabin depressurization. For aircraft that fly at high altitudes, the autopilot will have an emergency descent mode in the event that cabin altitude rises above a certain point. This is less of an issue than the first one, though.
In the end, this means that for an electric aircraft to fly higher and faster, it would end up needing to fly at supersonic speeds, and thus deal with the increased energy requirements of that, as well as the regulatory hurdles.
This doesn't mean we won't eventually see electric airliners, but they probably won't have a much different flight profile than today's aircraft.
Not a rocket engineer, but it might actually be reasonable that MCT use batteries built in the Tesla Gigafactory for energy storage during the trip to Mars.
They would need a football sized field of solar panels just to generate the methane to return, as well as a team of people to keep them clean and operating.
The plan as it stands right now is solar, but nuclear needs to be on the table.
>Now SpaceX only needs to start producing electric rockets, then they can all be unified.
actually electromagnetically driven mass driver - HyperLoop is just a preview or may be a side branch - built in NV/NM, a lot of cheap land with easy permitting and a lot of Sun.
Only small amount of payload - fragile items like humans - has to be delivered in space by rockets, the rest can be shot by the mass driver. And here we come, Martians...
Maybe not electric rockets, but SpaceX could start shooting self-driving cars with robotic arms... into space... to manufacture giant solar panels to beam down energy 24/7 to replace all the nonrenewable baseload.
(Or more prosaically, just use the dropping payload cost to launch some big solar sails with energy collectors and then beam it down as has long been proposed.)
As usual, though, you get what you pay for.
The free energy often comes in at a suboptimal angle, and half the time you can't even use it because there's a planet in the way.
I think it's only a matter of time until Tesla buys out SpaceX, too, though. Tesla will grow by 10x in the next 5-7 years (and that's just the car business), and will keep growing faster than SpaceX will. By the time SpaceX needs to go public, Tesla may just be able to afford it.
See the rest of this thread for the other interpretation of electric rockets (as in, with reaction mass, but external beamed power).