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Topic: Battlefield Earth (Read 498 times) |
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rmsgrey
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Battlefield Earth
« on: Jun 16th, 2004, 4:15am » |
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Having re-read the book (yet) again, I find that the author's mathematical knowledge (or lack thereof) leaps out at me even more on each reading.
An example to start off with, and let people try and come up with an example of:
Early on, it is mentioned that a Psychlo (the nasty aliens) tank has been cunning shaped so that "any incoming projectile would impact at a glancing angle"
Assuming that a glancing angle is defined as being more than 45 degrees off the normal, that the points of spikes can be ignored, but that "valleys" and saddle points cannot and that projectiles come in along straight lines "from infinity", can anyone come up with such a solid? Or proof that it's impossible?
If anyone wants a follow-up, what's the maximum angle such that a surface can be constructed where any incoming projectile must be at least that far off the normal?
If I still feel sufficiently worked up, I may post a chunk of text from later in the book for people to dissect later.
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towr
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Re: Battlefield Earth
« Reply #1 on: Jun 16th, 2004, 4:41am » |
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on Jun 16th, 2004, 4:15am, rmsgrey wrote:
Early on, it is mentioned that a Psychlo (the nasty aliens) tank has been cunning shaped so that "any incoming projectile would impact at a glancing angle"
Assuming that a glancing angle is defined as being more than 45 degrees off the normal, that the points of spikes can be ignored, but that "valleys" and saddle points cannot and that projectiles come in along straight lines "from infinity", can anyone come up with such a solid? Or proof that it's impossible? |
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You could have a look at fort designs. But I think there is always a way to shoot flat out onto the sides of the spikes..
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Grimbal
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Re: Battlefield Earth
« Reply #2 on: Jun 16th, 2004, 6:54am » |
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I don't think it is possible, except maybe with a fractal. But I have no proof.
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rmsgrey
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Re: Battlefield Earth
« Reply #3 on: Jun 17th, 2004, 12:30pm » |
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That's about what I've managed to get as well: probably impossible, but no clue where to start in proving it...
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Speaker
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Re: Battlefield Earth
« Reply #4 on: Jun 20th, 2004, 7:05pm » |
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There is a star shaped fort located in Hakodate Japan (on Hokkaido, the northernmost island in the archipelego). It is called Goryokaka (Go ryo ka ku). It was quite large, and is a park now, but it had some interesting features.
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Grimbal
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Re: Battlefield Earth
« Reply #5 on: Jun 21st, 2004, 5:50am » |
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The particular star shape of forts is designed to avoid places where the enemies can hide at the bottom of the walls. If you had a simple flat wall, you would have to lend over the wall to shoot people at the bottom. But with these multiple corners, you can protect the bottom of any wall from another corner of the wall.
This has nothing to do with avoiding front attacks.
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towr
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Re: Battlefield Earth
« Reply #6 on: Jun 21st, 2004, 8:18am » |
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on Jun 21st, 2004, 5:50am, Grimbal wrote:| If you had a simple flat wall, you would have to lend over the wall to shoot people at the bottom. |
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Actually, they'd usually poor liquid led over the edge, or burning tar and stuf..
Anyway, they did use the star design with deflecting cannon balls in mind.. And later designs improved that characteristic further..
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| « Last Edit: Jun 21st, 2004, 8:23am by towr » |
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Three Hands
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Re: Battlefield Earth
« Reply #7 on: Jun 21st, 2004, 9:48am » |
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The problem with flat walls was not so much that defenders had to lean over the edge - they could put up hoardings/machicolations or pour rather unpleasant things over the attackers, and so could deal with that. The bigger problem was that corners acted as "blind spots" for the defenders. Hence why shell keeps and round towers on corners were used for later castles. Once cannon was refined to being reliable, fortifications became more along the lines of large, but not very tall earth banks with appropriate slopes to absorb/deflect cannon balls, and having gun-loops so that you could shoot back. Add to this the aim of making attackers run through a route where you can shoot at them a lot, and fort design became more low-to-the-ground star-designed with nice sunken pathways just in front of the main walls to provide platforms to fire cannon from, defence against cannon fire, and a long, exposed channel of attack where you can kill most of the attackers before they get inside.
However, in most cases of these fortresses, the theories generally haven't ben tested much, because battles became more open-field orientated than sieges, which were typical during the castle age.
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