/sci/ - Science & Math

>>5561662
You could get a pile of solar panels and fly out into space with one.

Or put one above the clouds and moving so fast it coutneracts the earths rotation, giving infinite solar power while allowing luxuries such as atmospheric oxygen

>>5561676

>>5561662
>small modular nuclear reactors
you need to understand that, at any scale, nuclear reactors are bitchin heavy. the core itself is heavy, the coolant is heavy, the shielding around the core and primary coolant loop is heavy, the turbines are EXTREMELY heavy unless you're using high velocity gas turbines only, and that's a whole other ballgame of efficiencies.

might be kinda cool for something like a nuclear aircraft carrier, if you put two or three other navy reactors in there, and ran them at full power all the time, but shit is just too heavy

call me when we hit 100kN per kilowatt

>>5561676

>>5561662
Photons satisfy
E = pc.
This means that a perfectly collimated beam would achieve a ratio of thrust to power of 1/c, or 3e-9 kN per kilowatt.

Anyone who claims a higher figure is bullshitting.

>>5561921
wait, shit, this might actually kinda work on large scales.

>two A4W 4th gen westinghouse naval reactors in the uss george w bush
>combined 165 megawatts electrical (peak), running in paralell
>=165,000 kilowatts electrical
>30 kilonewtons per kilowatt
>4,950,000 kilonewtons
>the USS george w bush is 102,000 long tons (114,000 short tons) (103,419,000 kg)
>the gorge w bush requires 1,014,540,390 newtons to counteract gravity, 1,014,500.39 kilonewtons
>the reactors could, hypothetically, provide 5 times the necessary thrust to levitate an aircraft carrier

this is assuming i got my mass and force numbers right

but 30kN per kilowatt sounds kinda fishy from the start

>>5561947
aaaand after reading the wiki article i can see why
>reactionless drive
i'll believe it when a peer reviewed paper is published, and a test platform can lift itself

>flying nuclear reactors

That sounds lik a good idea

>>5561940
but that's an EM drive, it doesn't send out photons, it works by magic where it violates all knows physics and doesn't conserve momentum.

>>5561662
>fantastical flying cities of science fiction a real possibility

Not in any real or practical sense.

Just because a device exists for one scale doesn't mean it will work for anything much larger.
Also, since the entire point of applying such devices in the real world is their practicality, did you calculate just how much ENERGY would be needed for, let's say, a car without wheels.
Or, if you really need the 'city' example, an aircraft carrier.

>>5561662
>small modular nuclear reactors

So, you don't know a hell of a lot about nuclear power, huh?
a nuclear reactor isn't just a power device we can make in any size -- the minimum amount of fissile material alone is huge.
But all the other stuff that goes along with it is insane -- it isn't compressible. Shielding, pumps, control systems, and a supply of cooling water the size of a lake.
You can't just say 'make a nuclear reactor real tiny' and make any sense.

>superconducting

You need to cool it the fuck down to keep it superconducting. The added weight would screw things up.

>>5562000

We already put some of our most powerful and least-reinforced on 'boats' that automatically sink and are basically blind when they move.

>>5561662
OP, did you not read the page you cite?

It resounds LOUDLY with objections to the blithering nonsense and unscientific claims.

The aside that you quoted about a German superconductor (which leaves out massively critical details) comes right after Shawyer's noted attempt to create a drive which can run 1000 times weaker -- which has not happened.

>>5562089
the US military a had a reactor down to the size of a big room in a trench in the greenlandic ice cap

>>5562163

The reactor itself, perhaps -- but not INCLUDING the equipment, tanks of coolant, controls, monitoring and management equipment.

I've seen several articles about building reactors small enough for an apartment building; it occupies just a basement. But those, too, are not including all the ancillary stuff.

Just because those articles talk about a part being smaller doesn't mean they are almost mobile.

>>5562394
Toshiba is actually doing some pretty baller stuff with small, disposable reactor cores the size of two stacked water heaters, which they bury underground for shielding, and just have the power plant and sub station on the surface, the entirety of which takes up the size of a small house. i think they rated it at like 50 megawatts? which is actually pretty respectable for its size
http://en.wikipedia.org/wiki/Toshiba_4S