Ya!  The more I think about it, the better it sounds: instead of military and secret agencies spying on their own people and starting and waging wars, etc., to suit their respective rich, elites' interests, maybe the world's militaries could start building spaceships for them?

Instead of continuing to shoot ourselves in the foot, why don't we shoot ourselves into space?

Official US Military Budget***

Undeath, Einstein,

It's possible, feasible, and as I will argue, necessary for us with our current technology to build thousands, hundreds of thousands of "Ramas" from Authur C Clarke's book Rendezvous with Rama:

"The 20+ crew, led by Commander Bill Norton, enters Rama through triple airlocks, and explores the vast 16-km wide by 50-km long cylindrical world of its interior, but the nature and purpose of the starship and its creators remains enigmatic throughout the book. Inside Rama, the air is discovered to be breathable. The astronauts discover several features, including "cities" (odd blocky shapes that look like buildings, and streets with shallow trenches in them, looking like trolley car tracks) that actually served as factories, a sea that stretches in a band around Rama dubbed the Cylindrical Sea, and seven massive cones at the southern end of Rama - believed to form part of the propulsion system."

http://en.wikipedia.org/wiki/Rendezvous_with_Rama

First, the cylinder itself would necessarily have to be constructed by 3D printers in orbit, essentially satellites launched into space programmed to print layers of portions of the cylinder.  The satellites would print the cylinders with layers of graphene.

http://en.wikipedia.org/wiki/Graphene

Luckily, the material needed to produce graphene is abundant on Earth or anywhere else.  It is just carbon.  It could even be collected from the atmosphere, which would help stem the tide of global warming.  The carbon would have to be shot into orbit from wherever it is being harvested.  You could use nuclear propulsion - essentially using a cannon that uses a small nuclear explosion to propel the carbon into orbit; the opposite of this:

http://www.youtube.com/watch?v=46GBjlUOROY

See, instead of using gunpowder to shoot an atomic artillery shell, you'd use a small atomic explosion to shoot carbon (harvested from the atmosphere even) into space.

The carbon would be collected by the satellites which would produce and print the layers of graphene which would form the cylinder.

They'd also 3D print more 3D printing satellites, increasing the rate of production of cylinders exponentially, to keep up, of course, with the exponential rate of human population increase.

I suggest a good spot for launching the carbon necessary into space would be places which are already contaminated by nuclear waste / disasters - Chernobyl, Fukushima, etc.

Not really. They've been working on it for over 50 years:

http://en.wikipedia.org/wiki/Project_Or … pulsion%29

The colony ships in all likelihood would be powered by nuclear pulse propulsion.

At this point, we're still talking about how to get all the carbon needed to construct the cylinders into orbit.  Nuclear pulse propulsion would be used to essentially shoot the carbon into orbit.

"No, I mean that in the grand list of "things which would be needed to build an indefinitely lasting space colony," that's not the most difficult thing to overcome."

The cylinder would be pretty much as described by Arthur C. Clark in Rendevous with Rama, but with some improvements, for example:

Instead of living on the surface of the cylinder, they'd have apartments or living quarters built in such a way that hover above the surface of the cylinder, because the surface of the cylinder would be used primarily for ecosystem.

This is what it would look like standing on the inside surface of the cylinder:

http://www.yankodesign.com/images/desig … volvo2.jpg

On a clear day, above you would see the curvature of the other side of the cylinder, so, essentially, there would be more ecosystem above you, and more apartments hovering there above you.

There would be a weather systems inside the cylinder,  self-contained ecosystems, within which many generations of human beings could live indefinitely.

The cylinders spin, you see, so there is gravity.   There is also artificial sunlight - an artificial light emitter which which goes back and forth up and then down the center of the cylinder (where there is no gravity) once every 12 hours.

The cylinder can retain all the technology necessary for the people living within the cylinder to extend or even to build another cylinder in the event they can't find a suitable planet before their own population level rises to unsustainable levels.

They can set out with the capacity to live in self-sufficient, self-extendable, self-replicable environments, and, therefore, with the capability of living in space indefinitely. 

Of course, once a sufficiently habitable planet is discovered, they can use the same technology  to terraform and transfer their population to planetary surfaces, if they were to so choose, but, in all likelihood, many human beings would prefer to live in orbit within the cylinders.

It is possible:

"It’s already possible to make everything from guns to food to human body parts. If graphene proves workable as a 3D printable material, we could potentially add computers, solar panels, electronics, even cars and airplanes, [and colonization spaceships] to the list."

http://motherboard.vice.com/blog/3d-pri … the-future

"When 3D printers can use graphene, they’ll truly be able to replicate themselves. That’s only the tip of the iceberg though."

http://www.3dprinter.net/3d-printing-wi … t-graphene

"Hello triple a? I need a new engine and windsheild, ours got holed by micrometeors traveling at .9c. Our location is 500au west, 300au north and 157au up. we are the big colonizer so it wont be hard to miss us."

Graphene molecules 'printed' in the appropriate configuration would be able to withstand impact from micrometeors at 0.2 the speed of light which is about how fast the ships would be expected to go with current nuclear pulse propulsion.

1. if you can build a self-sustaining biosphere we can do that on earth easier than in space

2.  L5 not planets. Google it