...100 MW of Space Solar Power ...per single launch!
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From: Sylvia Else on 14 Dec 2009 20:00 Peter Fairbrother wrote: > Sylvia Else wrote: >> Uncle Al wrote: >>> Sylvia Else wrote: >>>> Uncle Al wrote: >>>> >>>>> 80% bullshit business plan number for RF >>>>> conversion >>>> At 80%, the remaining 20%, or 80MW, is heat that has to be got rid of, >>>> by radiation alone. >>>> >>>> Sylvia. >>> >>> Given 0% carbon footprint, 80 MW continuous ground heating cannot add >>> to Global Warming. Besides, it is add over a broad area. It's not >>> like lighting a candle or grilling a steak - both of which are >>> Enviro-whiner atrocities. >>> >> >> I wasn't talking about on the ground. If the space side conversion of >> generated power to microwaves is only 80% efficient, then there's 20% >> loss in heat. That heat has to be got rid of, or the system will melt. >> Given that it's in a vacuum, the heat has to be got rid of entirely by >> radiation. > > For physics reasons (in order to get a small enough beam spread) the > transmitter will need to be 0.5-1 km across, regardless of power; and > there is no real reason why it should not be made from heat-tolerant > materials, excepting maybe some of the electronics. Typically, the transmitting antenna would be a mesh to minimise the mass - the holes merely have to be small compared with the transmitted wavelength. But a mesh doesn't have a large surface area, which would be required to radiate away the heat. > > Even for my proposed 100 GW systems, cooling the transmitter isn't a big > problem. No external cooling systems are needed, just sunshades. Indeed > if it can operate at a few hundred C even sunshades are not required. What's the blackbody radiation per square metre at a few hundred Celsius? Sylvia.
From: Autymn D. C. on 14 Dec 2009 20:10 On Dec 13, 12:02 pm, "Jorge R. Frank" <jrfr...(a)ibm-pc.borg> wrote: > That's correct. The beam power density will be about one-fourth the intensity
From: Peter Fairbrother on 14 Dec 2009 20:12 tadchem wrote: > On Dec 13, 11:18 am, Peter Fairbrother <zenadsl6...(a)zen.co.uk> wrote: >> tadchem wrote: >>> [..] >>> Nice, if there's somebody in orbit who can use 400 MW. >>> If you want to use it planet-side, you have to get it down here. >>> THAT creates problems. >>> A storage device has mass, which brings all the transport problems of >>> a safe re-entry and recovery. >> Anti-matter? >> >>> A conduit would require materials with properties we have not >>> developed yet. >>> A beam would present an enormous safety and environmental hazard. You >>> could cook an Airbus in milliseconds with a 400 megawatt microwave. >>> That's about 200,000 heavy-duty microwave ovens - at once. >> Not so, actually - an Airbus weighs about 400 tons, call the exposure 1 >> kW/kg, or perhaps 1 degree C per second, so it would take several >> minutes, not milliseconds, before the Airbus might start losing >> structural strength. If it was flying rather than parked, the air would >> cool it so much that it wouldn't be affected at all. > > How long would the Airbus' avionics last in a 400 megawatt microwave > beam? > > You can't fly those crates by the seat-of-the-pants. Knock out the > electronic fly-by-wire systems and the plane becomes a brick. Indeed, the power level in the beam is above the FAA standards - aircraft would be required to avoid the area. However if there are only a few beams, say six in the US, and each exclusion area would be about 15 miles across, and probably located far from airports - not a big problem, eg you can't fly over Area 51 or whatever nowadays. I was just pointing out that the aircraft, even a composite one, wouldn't melt or anything like that! -- Peter Fairbrother
From: Autymn D. C. on 14 Dec 2009 20:20 On Dec 13, 11:57 am, Uncle Al <Uncle...(a)hate.spam.net> wrote: > 3) Solar cell efficiency real world is no better than 20% with > crystalline silicon. 80% bullshit business plan number for RF > conversion, 80% bullhshit^2 number for ground recovery. > (0.2)(0.8)(0.8) = 13% orbita; insolation to ground electrical > transfer, assuming absolute perfection. Look up the solar constant > for square mileage of solar cells required. 20% on Earth, and why silicon? > 4) After the power plant delivers 2.5x10^6 kW/hr of electricity it > covers its launch energy. After it delivers another 10^11 kW/hr of > electricity at $0.10/kW/hr net profits, it covers its launch cost. <smirk> > 5) At 400 megawatts 24/7, the bottom of the hole reaches ground > level - assuming no intermediate costs, after 28.52 years (including > leap years). > 6) Add in amortization of the cost of materials, maintenannce, > salaries, pensions, healthcare coverage, expense chits... and teh lfie > of a soalr cell installation under solar hard UV, radiation, meteor > showers, and orbital debris. Ground solar cells last about 20 years. What happens after 20 years? Not much, square. -Aut
From: Autymn D. C. on 14 Dec 2009 20:22
On Dec 14, 4:55 pm, Sylvia Else <syl...(a)not.at.this.address> wrote: > >> I wasn't talking about on the ground. If the space side conversion of > >> generated power to microwaves is only 80% efficient, then there's 20% loss > >> in heat. That heat has to be got rid of, or the system will melt. Given > >> that it's in a vacuum, the heat has to be got rid of entirely by > >> radiation. > > >> Sylvia. > > > It had to arrive entirely by radiation. Didn't you know the Sun is hot? > > Yes, and if the transmitter could run at the temperature of the surface > of the sun, there'd be no problem. Then why not make a plasma transmitter? |