...100 MW of Space Solar Power ...per single launch!
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From: Pat Flannery on 16 Dec 2009 20:25 Rick Jones wrote: > In which case, one presumes a flight path that went withing some > chosen distance of these beams would have a minimum enroute altitude > of GEO expressed in whatever the customary units would be right? Considering that: 1.) The rectennas would be built in uninhabited areas, like deserts or unproductive farmland. 2.) They would be only a few miles in diameter (that sounds big, but when you compare it to the total land area of the US, it's minuscule) ....your odds of flying through one by chance would be very low, even if your GPS navigation system couldn't be set to warn you if you were approaching one, and suggest you navigate around it. Even if an airliner flew right through one, its speed would mean it would be clear of it in a matter of seconds, before the skin suffered any noticeable heating. Although I'm sure the FAA would make the beams a no-fly zone, the worst you probably would encounter from passing through one is a short interruption to communications and a possible cut-out of GPS data while you were in the beam. And of course, if these SPS systems came into use, aircraft avionics would be modified to make sure no damage occurred if you did accidentally fly through one, in the same way present aircraft avionics are designed to tolerate lightning strikes on the aircraft. Pat
From: jimp on 16 Dec 2009 18:15 In sci.physics Pat Flannery <flanner(a)daktel.com> wrote: > jimp(a)specsol.spam.sux.com wrote: >> >> Buildings are visible and don't extend from the surface all the way through >> the atmosphere. > > That's what you have GPS collision avoidance systems for. While such a system has been in the proposal stage for years, there is no such thing. > When the GPS display panel in the aircraft catches fire, it means you > have accidentally wandered into the microwave beam. ;-) OK. -- Jim Pennino Remove .spam.sux to reply.
From: Dr J R Stockton on 16 Dec 2009 15:33 In sci.space.history message <00851e07$0$16793$c3e8da3(a)news.astraweb.com >, Tue, 15 Dec 2009 11:55:56, Sylvia Else <sylvia(a)not.at.this.address> posted: > >Yes, and if the transmitter could run at the temperature of the surface >of the sun, there'd be no problem. We know that a body at Earth's distance from the Sun, heated by solar radiation and cooled by its own natural radiation, has an equilibrium temperature of about (a little below?) the melting-point of ice. (The Earth is such a body, but has an atmospheric greenhouse effect making the surface warmer.) Such an object that is transmitting a large portion of the incident energy as microwaves to Earth must necessarily tend to run cooler than that, overall. The transmitting components themselves will dissipate heat, and must be cooled; but it is only necessary to transfer that heat to the rest of the structure. The components will be distributed across the structure, so the transfer should not be unduly difficult. Perhaps you do not have a background in the physical sciences? -- (c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05 MIME. Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
From: Rick Jones on 16 Dec 2009 18:55 In sci.space.history Pat Flannery <flanner(a)daktel.com> wrote: > Rick Jones wrote: > > In which case, one presumes a flight path that went withing some > > chosen distance of these beams would have a minimum enroute altitude > > of GEO expressed in whatever the customary units would be right? > Considering that: > 1.) The rectennas would be built in uninhabited areas, like deserts > or unproductive farmland. I don't think that "a plane might fly through the beam" is a sufficient reason to veto SSP, yet, just how far out into the boonies are power plants these days? Sure, you want these things out in the sticks, but the farther out, the more of your hard-earned, somewhat expensive, space-electricity you lose to terrestrial transmission losses right? > 2.) They would be only a few miles in diameter (that sounds big, but > when you compare it to the total land area of the US, it's > minuscule) > ...your odds of flying through one by chance would be very low, even > if your GPS navigation system couldn't be set to warn you if you > were approaching one, and suggest you navigate around it. Even if > an airliner flew right through one, its speed would mean it would be > clear of it in a matter of seconds, before the skin suffered any > noticeable heating. There is more in the skies than just UFOs and airliners :) And if you were flying past in your kit-built Rutan Long-EZ? For the "if it saves a single child" crowd - how about if that hoax runaway balloon with the kid inside story were real? http://www.cnn.com/2009/US/10/18/colorado.balloon.investigation/index.html > Although I'm sure the FAA would make the beams a no-fly zone, the > worst you probably would encounter from passing through one is a > short interruption to communications and a possible cut-out of GPS > data while you were in the beam. Would the chocolate bar in your pocket start to melt?-) http://en.wikipedia.org/wiki/Microwave_oven#History rick jones -- I don't interest myself in "why." I think more often in terms of "when," sometimes "where;" always "how much." - Joubert these opinions are mine, all mine; HP might not want them anyway... :) feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
From: Peter Fairbrother on 16 Dec 2009 19:01
Pat Flannery wrote: > Peter Fairbrother wrote: >> >> >> There is another, not obvious, advantage in building such a >> high-capacity launch system (almost certainly it would be a TSTO with >> a winged reusable first stage) - the lower the cost per pound of >> launch, the cheaper the hardware gets. > > When these systems were first proposed in the 1970s-80s the favored > launch system was a massive single or two-stage-to-orbit vehicle that > did a vertical takeoff and landing. One design used no less than twenty > F-1 engines, all firing during ascent, and six firing for landing. That's a different sort of system, a very large one and not winged. > Building a horizontal takeoff and landing or vertical > take-off/horizontal landing first stage for the size payload required to > make it economical would be daunting, as it would probably dwarf a C-5B > Galaxy as far as size and weight went. I'd try stick to something which could still land at an airport - which means a maximum of about 450 tons MTOW for a HTHL, and 1000 tons for a VTHL (it only has to land, empty). Using Lox/kero first stages and LOX/LH2 second stages a 1,000 ton VTHL could launch maybe 25-30 tons, and a 450 ton MTOW HTHL could launch maybe 8-9 tons into equatorial LEO. The difference is partly from scale, and partly because a HTHL would probably need to take off from an airport on jets rather than rockets - but this also means a HTHL TSTO booster stage can go-around, and loiter, on the landing approach. I favour the lighter system, about a 450 tons MTOW HTHL SSTO - about the MTOW of a 747, but a bit smaller. It also means you can use existing aircraft parts for eg landing gear, flap actuators, and so on. Also a HTVL has to be carrier from the airstrip to the expensive launch pad, then winched from horizontal to vertical between flights. The lighter VTVL option just uses an existing airfield. Also, since most booster designs > that use this design philosophy try to get up to around Mach 6-7 before > they release the orbital stage, you are going to have a huge square-foot > area of thermal protection materials that will need going over after > every flight to check them for damage, and that's a real pain in the > rear with even the far smaller Shuttle as far as man-hours go. John Carmack once said that the first stage should just go up and down, and the second stage should do the translation - but I don't entirely agree. The Shuttle TPS is made from carbon-reinforced-carbon, foamed silica tiles, and silica blankets in order of heat rejection capacity. CRC and foamed silica are very fragile, although silica blankets aren't nearly so fragile. A winged first stage, even with a Mach 6-7 horizontal component, has to dissipate less than a *tenth* of the energy per unit mass than a Shuttle re-entry. While it would some sort of TPS, we are not talking about the kind used by Shuttle, something much simpler and much more robust would be enough. We are talking about less than the silica blanket end of the range, not CRC or foamed silica. Also there isn't such a need for ultra-light weight in the TPS [*] so a much heavier TPS could be used. There are several possibilities, and in general it is quite do-able. It's a bit of a challenge but not in any way a deal-breaker. [*] it's a first stage, a bit of extra mass here has much less effect on overall performance than a bit of extra mass on a second or orbiting stage. > The fewer flights you need to get all of the materials for the SPS into > LEO (it can be moved slowly out to GEO via ion engines once assembled, > and building it in LEO really cuts back on assembly crew launch costs, > as well as removing the radiation threat to the assembly crew from solar > storms) the better from a economic viewpoint, NO NO NO! The number of flights is not relevant, the cost for the total mass launched is the important metric (okay there are other considerations like minimum component size and assembly costs, but that's the most important one). Large is not necessary if you can fly several times per day - I envisage a 10 ton payload HTHL TSTO flying once every 90 minutes from a ground site to a location in orbit with three launchers, giving a turnaround time of 4.5 hours. Break-even for a resuable system vs a disposable system comes at about 15 flights per year (general opinion, lower range) or 30 flights per year (NASA/Congress opinion), or 50 flights per year (pessimistic) - but if you are flying 1,000 flights per year the saving is enormous, and undoubted, even if the solution is high-tech - and we are not talking about high-tech in the Shuttle sense (and price range), but in the reliability sense. Jets fly that often or more, and much of the rocket technology (engines etc) pretty well already exists. [...] > Also, maybe the expendable upper stage can be used for something once > it's in orbit, like the proposals to use the Shuttle ET as a cheap space > station module. Yes, that sort of thing could be done - my preferred system returns the second stage engines, electronics, RCS and (maybe) LOX tank, but the LH2 tank is left in orbit for either living space or constructional material. There are other possibilities. -- Peter Fairbrother |