Re: A proposed solution to the problem of space flight
On Tue, Mar 31, 2009 at 8:07 PM, hkhenson hkhen...@rogers.com wrote: The laser stage does require a substantial amount of power, 4-5 GW (equal to a ton of TNT per second). You missed your posting time by 3 hours, 53 minutes. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: A proposed solution to the problem of space flight
Keith wrote: I don't know who on this list is up to understanding the technical parts . . . . I think I am. Or I was. Probably now I switched from being one of the good guys (working in the space industry) to become one evil minion (working in the oil industry) :-) The root problem is the same space flight has had all along--the rocket equation. All sins flow from the fact that at best one part in 60 of the liftoff mass gets to GEO or lunar orbit with chemical fuels. Here it is in graphical form. If you want to play with the rocket equation, just use this javascript: http://www.geocities.com/albmont/relroket.htm It's a relativistic rocket equation, but it works (obviously) for v c. The whole problem is that you need energy/power/speed/name-it to get the rocket away from Earth's athmosphere. Right now, the only way to do it is by chemical rockets. Now comes the second problem. Suppose you get to LEO. Theoretically, it's possible to use more efficient ways to transfer to GEO. One way is to continously thrust with a high-specific-impulse engine. But this would make the transfer take eons - and now economy plays a very important part in the equation: you don't want to _wait_! Time is money. So, the pretty little mathematical and physics of transfer bows to the implacable and ruthless laws of economics, and we use chemical rockets. Darth Alberto Monteiro ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Is this thing on?
I woke up this morning wondering if moving the Brin-L list to Bluehost has somehow killed it... because I realized that I'm not getting any messages, only digests. This is weird. I just double-checked everything and there's no reason I can see that would prevent me from getting the mail. I'd ask if anybody else hasn't been getting list mail, but, well, you know. Nick ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: Is this thing on?
Nick Arnett moderated: I woke up this morning wondering if moving the Brin-L list to Bluehost has somehow killed it... because I realized that I'm not getting any messages, only digests. This is weird. The move was transparent to me - as far as receiving goes. OTOH, it seems that the list now encourages html-e-mail, and this is an evil thing that should be eradicated. I'd ask if anybody else hasn't been getting list mail, but, well, you know. You can just send one message to the list and add in the BCC: field a list of subscribers. Then ask if anyone received it just once. As list-overlord you have this list, don't you? Alberto Monteiro ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: Is this thing on?
On Wed, Apr 1, 2009 at 9:26 AM, Alberto Monteiro albm...@centroin.com.brwrote: You can just send one message to the list and add in the BCC: field a list of subscribers. Then ask if anyone received it just once. As list-overlord you have this list, don't you? Ah, I actually received this, after switching settings around. One of the rotten things about using a hosted mailing list service is that there's no simple way to get the subscriber list. Nick ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Weekly Chat Reminder
The Brin-L weekly chat has been a list tradition for over ten years. Way back on 27 May, 1998, Marco Maisenhelder first set up a chatroom for the list, and on the next day, he established a weekly chat time. We've been through several servers, chat technologies, and even casts of regulars over the years, but the chat goes on... and we want more recruits! Whether you're an active poster or a lurker, whether you've been a member of the list from the beginning or just joined today, we would really like for you to join us. We have less politics, more Uplift talk, and more light-hearted discussion. We're non-fattening and 100% environmentally friendly... -(_() Though sometimes marshmallows do get thrown. The Weekly Brin-L chat is scheduled for Wednesday 3 PM Eastern/2 PM Central time in the US, or 7 PM Greenwich time. There's usually somebody there to talk to for at least eight hours after the start time. If no-one is there when you arrive just wait around a while for the next person to show up! If you want to attend, it's really easy now. All you have to do is send your web browser to: http://wtgab.demon.co.uk/~brinl/mud/ ..And you can connect directly from the NEW new web interface! -- William T Goodall Mail : w...@wtgab.demon.co.uk Web : http://www.wtgab.demon.co.uk Blog : http://radio.weblogs.com/0111221/ This message was sent automatically using launchd. But even if WTG is away on holiday, at least it shows the server is still up. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: A proposed solution to the problem of space flight
At 11:00 AM 4/1/2009, John Williams wrote: Keith wrote: I don't know who on this list is up to understanding the technical parts . . . . I think I am. Or I was. Probably now I switched from being one of the good guys (working in the space industry) to become one evil minion (working in the oil industry) :-) The root problem is the same space flight has had all along--the rocket equation. All sins flow from the fact that at best one part in 60 of the liftoff mass gets to GEO or lunar orbit with chemical fuels. Here it is in graphical form. If you want to play with the rocket equation, just use this javascript: http://www.geocities.com/albmont/relroket.htm It's a relativistic rocket equation, but it works (obviously) for v c. The whole problem is that you need energy/power/speed/name-it to get the rocket away from Earth's athmosphere. Right now, the only way to do it is by chemical rockets. There are other ways that would almost certainly work. Laser ablation, which takes a GW/ton of payload, and various methods that accelerate a vehicle to escape plus enough to get through the atmosphere. But your point is correct in that rockets or something closely related seem to be the current and possibly the best way to get above the atmosphere. Though in the long run (and assuming we can get the cable) you can't beat a moving cable space elevator for efficiency. 15 cents of electric power per kg to GEO. Now comes the second problem. Suppose you get to LEO. Ah, but you didn't read the specifications. The first stage in this design does not go to LEO, and the second (laser) stage doesn't either. It heads directly to GEO on one continuous burn. Amazing what you can do with 12-17 km/sec exhaust velocity and over a g of thrust. The energy in the laser beam is equal to a ton of TNT per second. Theoretically, it's possible to use more efficient ways to transfer to GEO. One way is to continously thrust with a high-specific-impulse engine. But this would make the transfer take eons - and now economy plays a very important part in the equation: It's not as bad as you think. Ion engines will take a power sat constructed in LEO to GEO in a few months. Unfortunately by the time it got there it would be full of holes and in dire need of repair. They are big enough to intercept a *lot* of space junk. you don't want to _wait_! Time is money. If you put another batch of lasers on the ground or build a set at GEO, then lift off to GEO is 5 hours. Initially, with only one set of bounce mirrors, we let the laser stage go around the Hohmann transfer orbit one and a half times. This puts the laser and bounce mirrors in the right place to circularize the laser stage to GEO. The time is money is certainly true. The design to cost criteria is to have parts delivered to GEO be incorporated into a finished satellite in a week or less. Starting at GW of power sat every day or two, ramping up over time to 2 GW/day or more. The intent is to displace fossil fuel entirely by mid century. So, the pretty little mathematical and physics of transfer bows to the implacable and ruthless laws of economics, and we use chemical rockets. They are ok for the first step, but using high exhaust velocity laser propulsion for the second stage reduces the lift off mass by a factor of 5 and the cost by a factor of 6. It's the difference between 5 cent per kWH which won't really compete with nuclear and 1 cent, which takes over even the oil market. Keith ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: Is this thing on?
Alberto wrote: The move was transparent to me - as far as receiving goes. OTOH, it seems that the list now encourages html-e-mail, and this is an evil thing that should be eradicated. Why is it evil, out of curiosity? Doug ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Why not HTML email
Reasons not to use HTML email... http://www1.american.edu/econ/notes/htmlmail.htm ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: Why not HTML email
At 07:17 PM Wednesday 4/1/2009, Euan Ritchie wrote: Reasons not to use HTML email... http://www1.american.edu/econ/notes/htmlmail.htm 3. You have no other way to access the character set you require to communicate with someone using another language*, and yet you wish to write that person. *Mathematics, frex . . . 10MB Of Allegedly Funny Pictures You Have Already Received Twenty Times Today Maru . . . ronn! :) ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
