technical question

Enforcer Talen · Post by **Enforcer Talen** » 2003-01-05 09:47pm

how much does a city of one million weigh?

and how much explosive would be needed to put it in literal orbit?

jaeger115 · Post by **jaeger115** » 2003-01-05 10:07pm

Why?

What are you thinking?

Durandal · Post by **Durandal** » 2003-01-05 10:11pm

Enforcer Talen wrote:how much does a city of one million weigh?

and how much explosive would be needed to put it in literal orbit?

I'm not going to try and answer the first question, but the second question depends on what kind of orbit you want to put it into. It'll be roughly 6E7 J of energy required per kilogram of mass.

Does this have to do with Macross?

SyntaxVorlon · Post by **SyntaxVorlon** » 2003-01-05 10:15pm

A:If you are planning on sending an entire city into orbit you're mad.
B: When you're considering weight of so large an area, assuming your sending a big dome or sphere into space, you also have to consider the force needed to push several million tons of atmosphere.
Experiment: Take a sheet of newspaper and lay it flat on the edge of a table at waist height. Slip a piece of plywood underneath halfway so half of the plywood is in the air. Whack the plywood with your hand or with a meter stick as hard as possible. Observe carefully as the plywood breaks as it tries to lift several tons of air out of the way all at once and observe that you have a splinter lodged in your eye from the shattered plywood.

Any cities in orbit around the planet, stations or mobile, would be built entirely in orbit. It's far more likely that any cities or habitats built in space would be stationed at the 4th and/or 5th LaGrange points, the safest, cheapest place to build in space.

Durandal · Post by **Durandal** » 2003-01-05 10:18pm

Also, using explosives won't propel the city into orbit, just destroy it.

jaeger115 · Post by **jaeger115** » 2003-01-05 10:22pm

If u want to use explosives to propel an city into orbit, you'll have to put a HUGE shield under the sewers. The bigger the city is, the wider and heavier the shield will have to be. And if you pit the shield against nuclear weapons.....

Slartibartfast · Post by **Slartibartfast** » 2003-01-06 03:17am

It wouldn't work unless you're a Looney Toon, in which case numbers are irrelevant.

Enforcer Talen · Post by **Enforcer Talen** » 2003-01-06 03:51pm

not a city itself, but the weight of. how much armor would be neccessary?

it's for a sci fi I'm working on. simple solutions for simple problems.

Durandal · Post by **Durandal** » 2003-01-06 04:02pm

Well, find the mass of a city the size you're looking for and use my 60MJ/kg figure. No offense, but I'm not about to go out and do all your research for you.

Enforcer Talen · Post by **Enforcer Talen** » 2003-01-06 04:06pm

well, I dont know what to look for. science is not exactly my strong suit.

Durandal · Post by **Durandal** » 2003-01-06 05:18pm

Enforcer Talen wrote:well, I dont know what to look for. science is not exactly my strong suit.

There's this thing called Google ... perhaps you've heard of it.

Malecoda · Post by **Malecoda** » 2003-01-06 08:04pm

why not just assume a spherical cow? I mean, suppose solid shapes made of concrete and steel. Or find out the weight of a skyscraper, or assume that skyscrapers weigh 50,000 tons. and so on.

Enforcer Talen · Post by **Enforcer Talen** » 2003-01-06 09:09pm

yeah, I've heard of google, but I wouldnt understand what I've found. lacking in science skills, remember.

Durandal · Post by **Durandal** » 2003-01-06 09:39pm

All you need is the mass of a skyscraper or building. Then just use my 60MJ/kg figure.

DPDarkPrimus · Post by **DPDarkPrimus** » 2003-01-07 12:30am

Slartibartfast wrote:It wouldn't work unless you're a Looney Toon, in which case numbers are irrelevant.

It just has to be a small shed full of red dynamite, ignited by a match lit unwittingly.

Post by **Darth Wong** » 2003-01-07 12:41am

Keep in mind that an entire city does not have the structural strength to be lifted and moved. It would simply disintetgrate. And anything but the most cushiony-soft ride would make all the tall buildings collapse. The last thing those buildings need is a jerky 6G acceleration upwards.

Zoink · Post by **Zoink** » 2003-01-07 10:34am

Well there goes my plans to stick big booster rockets on the island of montreal....

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Enforcer Talen:

If you want the weight of the city and ground the city is on, simply neglect the buildings and people.

Take the area of a typical city (for example montreal is about 1 million) multiply by desired ground depth (ie leftover crater, 20 ft?) and density (density of clay?).

This will give you an estimate that is reasonable since the majority of the weight is the ground.

Enforcer Talen · Post by **Enforcer Talen** » 2003-01-07 12:05pm

mind you, I'm not planning for the story to lift a literal city right out of the ground, skyscrapers and all. . . deep space would be unpleasant for all those unprepared windows, methinks. I'm looking for the weight of a city so I can say, it takes this much to get it off the ground and into space - the weight is placed better, made for the bumpy ride, all that.

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