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View Full Version : FXWars! MoonShot!: Ben Bolin


BenBolin
04-07-2005, 03:55 AM
Ok, time to announce my entry. Though this is in the "Fantasy" category, it is based on some fairly solid science. I'm producing a visualization of the "Bifrost Bridge" described by Marshall T Savage in the book "The Millenial Project: Colonizing the Galaxy in Eight Easy Steps."

The title is of course facetious, but the book is essentially an essay charting Savage's thoroughly thought out plan for expanding human civilization beyond our solar system over the next thousand years using currently understood physics, . "Bifrost" is what the Norse called the rainbow, a bridge between heaven and earth across which the Valkyries bore the souls of victorious warriors to paradise in Asgard. In Savage's universe, this bridge is a combination of a superconducting mass-driver and laser propulsion used to launch humans and cargo into space. In order to accellerate a spacecraft to orbital velocity without subjecting passengers to deadly levels of force, the mass driver must be huge... 125km in length! Obviously, building a vertical structure of this size is impossible, so the track will be horizontal and vertical launch is achieved through an upward curvature at the end. The mass driver is placed so that it's muzzle (the exit) lies atop Mt. Kilimanjaro, and the length of the tube is west from there, running underground beneath the Serengeti plain. The tube is evacuated of air so that there is no resistance inside, and a high speed air lock allows the spacecraft to exit without breaching the vaccuum. The spacecraft is mounted on a sled which is levitated with superconducting magnets, and accelerated from the west to the east through the mass driver at a rate of about 980m/s^2 (or 10g's) for about 50 seconds. As the track curves upward at the end, the passengers are subject to 300g's for about 2 seconds, which is extraordinarily unpleasant, but not deadly.( It could be made less unpleasant by suspending passengers in liquid during takeoff, thus distributing the force over the entire body in the form of fluid pressure). The craft leaves the muzzle atop mt Kilimanjaro at about 5km/sec, creating a tremendous shockwave which is reflected upward by the sides of the mountain, away from the copious wildlife below. The sled detaches from the craft and parachutes to the ground, and is recovered and reused. Orbital velocity is 8km/sec, and escape velocity is 11.2km/sec, so we still need more thrust. This is achieved via laser propulsion. Six free-electron lasers rated at 250 megawatts each and each tuned to a different portion of the visual spectrum focus on a slab of ice mounted on the rear of the spacecraft. The surface ice is superheated to 10,000 degrees celsius, turning into steam with an exit velocity of 10,000 m/sec. Because the power is provided from the ground, the craft only needs to carry a fraction of its own weight in ice; Savage gives the example of 4 tons of ice for 10 tons of cargo in an earth orbit launch. Presumably we need somewhat more for a moon mission. Propelled by steam, the craft accelerates upward at an angle of 20 degrees from vertical at 1.25 g's for 20 seconds, then kicks over into a horizontal position. The ground lasers are redirected into oribiting mirrors, which reflect their light again onto the ice propellant, allowing horizontal thrust. Total burn time is about four minutes. (Of course I'm not going to show every second of this.) At that point inertia carries the craft the rest of the way to the moon.

Strangely, Savage is not as explicit about how routine landings on the moon would operate, so I'm extrapolating here. Another laser array, which Savage calls Excalibur, is placed on the moon, and the spacecraft carries enough ice on board to allow it to decelerate to around 1 kps, Lunar orbital velocity. In Lunar orbit, it picks up additional ice (gathered from one of numerous mining operations in the solar system) and Excalibur brings it in for a landing with the assistance of mirrors in lunar orbit. The spacecraft will actually land on a conventional runway, but it will come in backwards, so that a laser at the end of the runway can power the ice thruster during approach, finally bringing it to a stop on the runway. The moon base will consist of a set of domed craters.

(GASP, breathe, breathe...)

Ok, Any thoughts, or suggestions?

rquinn
04-08-2005, 06:40 AM
300g's 2 seconds
hmm
plenty of time to make anyone into a pancake

BenBolin
04-09-2005, 01:07 AM
Hmm... well I figured that Mr. Savage (Dr. Savage? I don't know) had done his homework, but it looks like you're right. According to these guys - http://www.luf.org/talk/fmf-eng/1996/0099.html , 255 gs is well into the lethal range for human beings... which was of course my gut reaction to the idea in the first place. But hey, at least it's not as bad as Jules Vern's spacegun. That thing would turn the crew into extra chunky salsa. Oh well, serves me right for leaving the math and science to a guy with an English degree. (Of course my degree is in "Imaging and Digital Art", so I can't really criticize, now can I?) The gentlemen at that site also say that he got the launch angle wrong and that the visible spectrum isn't really the best choice for the lasers. Of course, they also point out that with a little more ice, you could actually launch a Waverider (the type of vehicle Savage describes in the book) into orbit with lasers (in the near infrared)alone with a continuous acceleration of only 2g's. Or you could build a mass driver with a much longer arc, extending upward through a long east-west equatorial mountain range...Unfortunately, glancing at a world map, I don't think earth has one of those...bugger all. So I have to revise my concept.... Or I could just accept that this is a "fantasy entry" after all.
I managed to get some nice footage of Kilimanjaro I got from the public libarary (screw the Digital Millenium Facist Copyright conspiracy, this is for personal educational purposes, it's fair use I SAY, FAIR USE!) and I was going to try to track against them for the take off shots. Of course herein lies another bit of reality intervening in fantasy... the dvd in question discusses the fact that Kilimanjaro may be becoming active again.... well, you do have to cook pancakes after all.....

rquinn
04-09-2005, 10:01 AM
indeed
well
you are onto something for sure either you keep it as is in the book and make it Fantasy
or bend it a little and make it your own with a twist in the fantasy and hard science together

I opt for the second

;-)

good luck

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