[Moontanman]

Originally Posted by Pyrotex

Always look for basic assumptions. Then look again.
MoontanMan has logic on HIS side if we must depend on "rockets" to expell reaction mass to lift the megatons we will need per colony.
ThunderBird has logic on HIS side if we don't.
The alternatives?
1. space elevators. Not just 1, but hundreds strung along our equator, each lifting 10 to 100 tons per week.
2. lift the materials from the Moon, which has only 1/6 the gravity. Better yet, use rail guns to "shoot" the raw materials into Lunar orbit.
3. teleportation. No, NOT Star Trek style stuff, but at the atomic level. It just may be possible to teleport simple small atoms at near-zero Kelvins. If we can teleport cryogenic hydrogen and oxygen atoms (rocket fuel!), then you can easily use rockets to orbit the Queen Mary stuffed with all the cargo she will hold. Hell, you can orbit entire prefabricated sections of your colony.

Actually I don't think we need to lift the materials for a colony from the Earth. We need to build them in space from materials already in space. Even a space elevator wouldn't be as cheap as building them in place. Nuclear rockets would be needed to raise up some things at first but most of the stuff is already there, in orbit, ice moons, Lagrange point asteroids and comets. Hydrogen and oxygen are not the rockets of the future. Nuclear energy will be needed to make these things work.

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[Thunderbird]

Originally Posted by Pyrotex

Always look for basic assumptions. Then look again.
MoontanMan has logic on HIS side if we must depend on "rockets" to expell reaction mass to lift the megatons we will need per colony.
ThunderBird has logic on HIS side if we don't.
The alternatives?
1. space elevators. Not just 1, but hundreds strung along our equator, each lifting 10 to 100 tons per week.
2. lift the materials from the Moon, which has only 1/6 the gravity. Better yet, use rail guns to "shoot" the raw materials into Lunar orbit.
3. teleportation. No, NOT Star Trek style stuff, but at the atomic level. It just may be possible to teleport simple small atoms at near-zero Kelvins. If we can teleport cryogenic hydrogen and oxygen atoms (rocket fuel!), then you can easily use rockets to orbit the Queen Mary stuffed with all the cargo she will hold. Hell, you can orbit entire prefabricated sections of your colony.

You could combine a rail gun technology with a low gravity corridor.

The best way to build a space elevator, is by digging a very deep hole in the earth. If you could drill a very large hole on the equator, lower your cargo down to a depth of say 25 miles accelerate it to escape velocity of 25000 miles an hour the moment should carrier it up into orbit. Equatorial launches are as you probably know are easer because of the extra speed provided by the earths rotation. What you may not know is removing so much mass directly under the launch sight will create a low gravity corridor above it. The lower G elevator could also be maximized by waiting for the moon to be positioned directly over head not A lot I know but it would be peak launch time. If you could build this elevator yes it would then become practical to build a very large space station.

[Pyrotex]

Trouble is, TBird, if you want to achieve an orbit, you need 25,000 km/hr not straight up, but perpendicular to your giant hole in the ground. The best you could achieve with the deep hole is to launch cargo on an escape trajectory.

[Thunderbird]

Originally Posted by Pyrotex

Trouble is, TBird, if you want to achieve an orbit, you need 25,000 km/hr not straight up, but perpendicular to your giant hole in the ground. The best you could achieve with the deep hole is to launch cargo on an escape trajectory.

This is true I didn't calculated the trajectory but assumed being launched at the equator would give it that extra bit of a ballistic curve. It seemed that if your escape velocity held up you could achieve a geo-centric orbit., or would it simply begin to fall back to earth? frankly I don't know.

[Pyrotex]

Well, I am a rocket scientist. Although a very humble one.

25,000 km/hr imparted at the surface of the Earth in any "up" direction will either escape entirely or collide with Earth.
You need about 4,000 km/hr imparted at the surface -- straight up -- and at an altitude of several hundred miles, when your upward speed is nearly zero, impart 25,000 km/hr at right angles to the vertical.

Of course, that's inefficient. You want what all our launched rockets do: obtain a smooth increase of velocity that starts in the vertical, and as the vehicle leaves the thickest part of the atmosphere, smoothly transition to accellerate at right angles to the vertical, and push in the horizontal until you achieve orbital velocity. About 50% or more of the rocket fuel is burned NOT to get higher above the surface, but to get FASTER around the surface.

[Moontanman]

Nuclear light bulb rockets will do the job and get one thousand ton payloads into orbit with no fuss at all. launching from the surface with a rail gun would be like slamming into a concrete wall when the the payload hits the atmosphere at 25,000 miles an hour. Rail guns only work well from low gravity wells in a vacuum. far to complex and expensive when nuclear will do the job safely and economically.

[Moontanman]

While it's easy to see what a space colony should look like after it's finished and even while it's being built but filling all the huge space with air, water, and soil would be a less than straight forward operation. Soil could not really be simply ground up rock, there would have to be a biological component. Air would almost certainly have to be processed by microorganisms. Possibly the partially finished colony could be boosted in a slow orbit to an orbit around titan where nitrogen could be pumped up from the low gravity surface. More likely frozen water and ammonia would have to be used to produce Water oxygen and nitrogen for the air. Bacteria could be used to turn ammonia into nitrogen and methane could be used along with water and ammonia to produce bio films to use in the making of soil. Once enough air was made hardy plants that live in areas of the Earth where soil is mostly rock or sand could be grown in the regolith possibly these pants could be used to make bio char to to fortify the soil for less robust plants such as ferns, mosses, grasses, shrubs and eventually trees. Once the first colony was established bio elements from the first colony could be used to make soil in the new ones.

[Moontanman]

At some point humanity will want to decide if Terra forming is the right thing to do to Mars. No matter how Earth like orbiting colonies are there will be a limit to the actual size of these colonies. There will always be people who want a real planet beneath their feet.

I personally think that at some point we as a people will begin to think of the Earth as a zoological park. We will want to allow the Earth to lie fallow to allow the ecology to recover from the actions of humanity and maybe even allow for or even guide the development of other intelligent species.

If we do this I think we will want to have a planet of our won we can justify doing what ever we want to it with out any moral qualms about destroying a ecosystem of what may indeed be a very rare phenomenon, complex life.

If complex life is as rare as some think then it becomes intolerable to cause the extinction of any life forms on the Earth. It is always a tragedy for a species to become extinct, this tragedy becomes many orders of magnitude worse if complex life is as rare as some think it might very well be.

So even though we can support billions maybe even trillions of humans in the relative luxury of space colonies. Space colonies will be a far cry from a wild environment. Terra forming Mars will allow us to "have our cake and eat it too" Once we establish a huge presence of space colonies that are very long lived and low maintenance the move to the nearest stars will begin.....

[DougF]

I think we will build orbiting colonies they will small at first but will grow in stature as we get our foothold in space, we will protect the orbiting colonies with a Plasma field, and use a plasma dome to protect our people while we're mining moons and asteroids.
Trek-Like 'Cold Plasmas' Shield, Cloak

we might start this due to global warming or pollution,
but IMHO we will have to make the jump to space soon.

Moontanman
I personally think that at some point we as a people will begin to think of the Earth as a zoological park. We will want to allow the Earth to lie fallow to allow the ecology to recover from the actions of humanity and maybe even allow for or even guide the development of other intelligent species.

Yes I agree with you, I think as we move to space we will recycle our cities to build the orbiting colonies, leaving only a handful of Vacation Resorts around the world for periodic schooling and vacations, it should be International Policy to return the Earth to it's natural state. IE "that it becomes intolerable to cause the extinction of any life forms on the Earth".

Moontanman
So even though we can support billions maybe even trillions of humans in the relative luxury of space colonies. Space colonies will be a far cry from a wild environment. Terra forming Mars will allow us to "have our cake and eat it too" Once we establish a huge presence of space colonies that are very long lived and low maintenance the move to the nearest stars will begin.....

I don't think we have the time needed for the Terra forming of Mars, but I think we could and should build dome city's first to get the ball rolling, a Plasma dome will hold in the atmosphere while protecting the inhabitance, it would tough at first but Earthlings are a tough breed once we put our minds to it.
the single most important thing is "We will live in space and make (Terra forming) the planets in Earth's image (the clean one) for if we live in space and just visit Earth every now and then we will enjoy it and appreciate it all the more".

Then we can "have our cake and eat it too"