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Re: A few points
Posted By: SiliconDream=PN= <querl@uclink4.berkeley.edu>	Date: 1/9/00 2:57 p.m.
In Response To: Re: A few points (Bachus) > Are you sure 17,500mph is correct? I wish I had my big thick > astronomy book with me, but until Monday I have to go with web > resources. Anyway, I found this on the NASA web-site: Shuttle_escape_velocity.txt > And what it says is that a shuttle needs to go 36,000fps (feet > per second) to achieve escape velocity. Now 36,000fps is equal > to 6.82mps. There are 3600 seconds in an hour, so that gives > 24,552mph. Feel free to check my math, dispute me, show other > sources, etc... I don't mind, really. : ) Whoops, you're right. I forgot to divide by two at one point. :) See, this is why I want to do *theoretical* physics, where my frequent math errors won't cause reactors to melt down or satellites to plunge from the sky... Anyway, that completely reverses both of my conclusions. Crashing onto the Halo is less painful, and firing missiles across it is easier. Sigh... <snip> > Now assuming I'm correct, we can find some more things out. The > diameter of Halo has been reported at 10,000km. That gives it a > circumference of 31,400km. The Earth has a circumference of > appr. 25,000m and rotates at about 1000mph. To get a gravity of > 1g, you need to spin at a speed of 32feet/sec/sec. Gravity is > proportional, so taking the escape velocity of Earth and Halo, > that gives Halo a gravity .81 that of Earth's. Which means it > rotates at 26.082feet/sec/sec. Of course, this figure tells us > nothing. So, g = v^2/r and V=2*pi*r*rpm/60. So > 26.082=v^2/1.64042e+07 Feet. v=20684.6. > 20684.6=(2*pi*1.54042e+07)*(rpm/60). rpm=.012. This is basically the opposite of what I did. I assumed the Halo had Earth-normal gravity and calculated its escape velocity accordingly--making that divide-by-2 error as I did so. BTW, you can't assume that the Halo's and Earth's gravity strengths are in the same proportions as their escape velocities. The Halo's pseudogravity falls off in a very different way from a planet's; also, for Earth you're calculating the velocity necessary to coast to infinity but for the Halo you're calculating the velocity necessary to reach the center. Oh, and Joe Staten says it's miles, not kilometers. I asked him if he was sure and he said yes, he really meant to say miles. > So, what does all this tell us? First, Halo has a gravity a > little bit less than Earth. The moon's gravity is about .16g > versus Halo's .81g. Next, Halo spins fast. Real fast. Appr. > 14,048mph, or 14 times Earth's speed of rotation. Earth's > gravity is based on it's mass, while Halo needs to spin to > maintain gravity. Of course, speed is all relative. So while on > the ring, you won't notice it's speed. All you'll feel is the > gravity. Afterall, the Earth rotates the sun at a speed of > 67,000mph. I think it's best to start with the assumption that the Halo has Earth-normal gravity, not with anything about the escape velocity. We can estimate the gravity from the movies we've seen, but we know nothing about the escape velocity as yet (except as can be calculated from the gravity). > Hah! I knew all this physics and astronomy would pay off! Oh, > and on an unrelated note. The Earth has 5 lagrange points. The > first three are unstable. If you're at the very center, no > problem, but the second you move even a little off, you'll fall > out of orbit. L-4 and 5 actually actract objects. Not sure about > the L-4 point, but the L-5 point is at the third tip of an > equilateral triangle with sides of 384,000km. The Earth and Moon > are at the other two points. In the Halo system, the points > stability should all be the same. The positions would all change > though since the planet and moon are different masses and have > different size orbits. Yes, Nathan's said that the Halo is either at the L4 or L5 point. --SiliconDream

Message Index

A few points	SiliconDream=PN=	1/8/00 11:45 p.m.
Re: A few points	Mark Levin	1/9/00 12:30 a.m.
Re: A few points	SiliconDream=PN=	1/9/00 4:00 a.m.
I saw it too.. I think...	DeusExMachina =PN=	1/9/00 4:13 a.m.
What I don't understand.	Manus_Lacatus	1/9/00 12:32 p.m.
Re: What I don't understand.	Mark Levin	1/9/00 1:26 p.m.
Re: What I don't understand.	Chris Huff	1/9/00 1:42 p.m.
Re: What I don't understand.	Mage	1/9/00 2:26 p.m.
Bungie is doing this on purpose...	Daft Shadow =PN=	1/9/00 3:19 p.m.
Re: Bungie is doing this on purpose...	Dr. Nick	1/9/00 4:37 p.m.
Re: Bungie is doing this on purpose...	SiliconDream=PN=	1/9/00 5:38 p.m.
Re: Bungie is doing this on purpose...	Mage	1/9/00 6:00 p.m.
Re: Bungie is doing this on purpose...	Daft Shadow =PN=	1/9/00 6:19 p.m.
Re: Bungie is doing this on purpose...	Mage	1/9/00 9:13 p.m.
Ouch...	Daft Shadow =PN=	1/10/00 12:06 a.m.
Re: Ouch...	Draeger	1/10/00 6:14 a.m.
I can fly....really I can...(NT)	Magh Tuireadh	1/10/00 7:44 a.m.
After a mortar hit :) NT	Draeger	1/10/00 2:51 p.m.
Re: Ouch...	Someguy	1/10/00 3:24 p.m.
Re: What I don't understand.	SiliconDream=PN=	1/9/00 3:52 p.m.
Re: What I don't understand.	Mage	1/9/00 4:15 p.m.
Heh we asked for it, but....	DeusExMachina =PN=	1/9/00 8:01 p.m.
Re: Heh we asked for it, but....	Magh Tuireadh	1/9/00 8:07 p.m.
Re: Heh we asked for it, but....	Otokam	1/9/00 8:35 p.m.
Gah....Gravity!	Magh Tuireadh	1/9/00 9:07 p.m.
Re: Gah....Gravity!	Otokam	1/10/00 2:55 a.m.
Really?	Magh Tuireadh	1/10/00 7:38 a.m.
Re: Really?	SiliconDream=PN=	1/10/00 4:18 p.m.
Unfortunately not...	SiliconDream=PN=	1/9/00 9:40 p.m.
Hey, cool!	DeusExMachina =PN=	1/10/00 12:45 a.m.
Re: What I don't understand.	Magh Tuireadh	1/9/00 8:03 p.m.
Re: What I don't understand.	SiliconDream=PN=	1/9/00 9:32 p.m.
Atmosphere?	Goat	1/9/00 4:19 p.m.
Re: Atmosphere?	Mage	1/9/00 4:20 p.m.
Re: I saw it too.. I think...	SiliconDream=PN=	1/9/00 3:05 p.m.
Re: A few points	Bachus	1/9/00 4:08 a.m.
Re: A few points	Dead Glory	1/9/00 11:51 a.m.
Re: A few points	SiliconDream=PN=	1/9/00 2:57 p.m.
Re: A few points	Bachus	1/9/00 4:24 p.m.
Re: A few points	Mage	1/9/00 4:32 p.m.