> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Charlie Bell > Sent: Wednesday, April 16, 2008 6:49 PM > To: Killer Bs (David Brin et al) Discussion > Subject: Re: An interesting response > > > On 17/04/2008, at 3:14 AM, Dan M wrote: > > The speed of sound barrier is rather > > significant, and we have not found a way to develop efficient planes > > that go > > at Mach 1.1 almost 60 years after we first went above Mach 1. > > So-called supercruise. The biggest problem with going over Mach 1 is > political and legal, not technological - had Concorde not been killed > by politics.
Well, Concord was a political animal from the very beginning wasn't it? It was a tax subsidized showcase for Britain and France from the start. IIRC, it never really was a profit center. > its successor would have been an "efficient" supersonic plane. I don't doubt that a successor would have been better, but you putting "efficient" in quotes seems to indicate that you aren't arguing against the fundamental increase in cost per passenger mile when a plane goes at Mach 1.05 compared to Mach 0.95. That's not political. The decision to use tax money to subsidize the travel of the richest businessmen is, of course, political. > >> Can you be specific about what you mean here? > > > > Sure, to be effective, power would have to be transmitted down in a > > fairly > > dense fashion. One needs mechanisms that provide feedback to turn > > the power > > off should the aim stray. > > Current designs seem to show a wide collection with a diffuse beam, so > that it's relatively safe to be under the beam. OK, then there would be the cost of a wider array, earlier designs had cheaper local receivers with feedback required to keep the beam on. I'm not saying that this would be a showstopper, it's just that it's part of the price that has to be figured in. http://en.wikipedia.org/wiki/Boeing_747 > And 747s, beyond the basic airframe and control systems, are very > different to what they were in the 70s. (by the way, they were > "brought online" in 1970.. OK, the first commercial flight was Jan, 22, 1970...my apologies for rounding. But, the 747 is still in competition, sometimes on the same routes as smaller planes...and there are still a number on order (see site given above). > Point on this part is that there is huge inertia when there's huge > capital expenditure - if you've spent a few tens of millions on a > plane in 1970 or 1980 you're going to keep using it as long as you > can, 'cause a similar plane costs a few hundred million in 2008. I understand that, but there was a huge inertia > All that said, I'd like to see you, Dan, try to put together a cost- > analysis on a powersat project. Sure, be glad to. The cheapest commercially available launch to geosynchronous orbit (GEO) that I know of is the Russian Zenit program. For about 90 million, one can get a payload of just over 1800 kg into GEO. That's just under 50,000 per kg. http://en.wikipedia.org/wiki/Zenit_rocket OK, so lets calculate output per kg. of weight. From a site that is promoting their solar cells for use in orbit http://www.mdatechnology.net/techprofile.aspx?id=226 we get an output of 150W/kg. That gives us a launch cost of about $325 per watt (I'm rounding down now instead of up). Nothing works 100% of the time, but lets assume a 95% efficiency, or running 8322 hours/year. The cost is, then, about $39 per kWh. Dan M. > tenacious posting to naysay, so I'd like to see you attempt to solve > the problem so I can see where the problems are. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
