It's the Bering Strait all over again

[Iron_Maiden]

http://news.yahoo.com/space-junk-litter ... 3QD;_ylv=3

Intresting article about human litering in space. Too much crap here, too much crap up there, next its the moon, then Mars, and eventually we will just fire it into the sun or a black hole and be done with it. I certainly hope no nutjob catches a peice of the debris composed of bio-metal and seels it on e-bay, I just know the Cerberi and Chinese are working together to assemble an army to take us over!

Also, Happy Labor Day (Early)

[Psychedelic Rhino]

It is indeed getting to be a ~problem~.

But also consider that 99% of the "problem" is in low earth orbit. Sort of the ghetto of the debris space. Once past the 100-400 mile orbits, the problem with man-made debris is almost non-existent.

Geosynchronous is crowded, but those tend to have little to no delta-V to each other at a specific location.

But even in the "crowded lower orbits", they are not the 'mine-field' as the imagery of many articles suggest. Consider this thought experiment. . . take all the debris. . .maybe the volume of a couple boxcars. . .a few hundred thousand pieces. That seems like a lot, but let's spread it around the surface of the entire planet AND enlarge each piece, each washer, each paint flake, to the size of a motorcycle. Set all these bikes racing around at 150mph in straight trajectories, but ONLY on the landmass of the planet, exclude the surface of the oceans (of course). So we've excluded 72% of the available surface area. Let's assume you can just make out a motorcycle at eight miles. You could very well live your entire life only seeing a few dozen pass by off in the distance, let alone being struck by one. And that's with the bikes traveling around on the same plane as you and on the 'restricted surface area'.

Now, let's add the entire earth surface and several hundred miles of vertical volume for the bikes to travel around in. . . and you might not see one in a lifetime.

Of course having a paint flake the size of a fingernail with a delta-V of 30,000 feet per second, hit someone conducting an EVA would not end well.

[APCs r Evil]

I don't see what the problem is. If NASA would just switch to using ground-based wormhole generators like the rest of us, it wouldn't matter if Earth were surrounded by asteroids.

[Psychedelic Rhino]

What we may see in the next 25 years is the "space elevator".
Nano-tech appears it may provide the tensile strength in 10-15 years, but the design,
ultra high volume manufacturing and funding may not appear for two decades.
What I find stunning is these designs need to reach out to geosynchronous orbit.
They can certainly release payloads at pretty much any height once in vacuum,
but needing geosynchronous orbit height, if not at least for the counterweight,
to work, blows me away.

[HitchcockGreen]

I've been waiting for work to start on the space elevator for over ten years now.

[MrTwosheds]

You'll be waiting allot more than 10 years. While insurance company's still exist, space elevators will not.

[Psychedelic Rhino]

Nano cables/ribbons are just not there yet.

[GSH]

There's a saying about another bit of technology:

"Fusion is the energy source of the future. And it always will be."

Some technology speculated about in science fiction requires just a few too many steps of the "then a miracle occurs" to get from where we are now to where people want us to be. It's nice to dream. But, there needs to be a realistic understanding of how far things are off from current technology and engineering. Especially engineering. Engineering can optimize the last 5% of the way. But, if we're not already in mass production within the last 5%, it's not ready yet.

-- GSH

[HitchcockGreen]

Nano cables/ribbons are just not there yet.

Not yet.

[MrTwosheds]

Allot of idea's just don't get thought through, like nuclear reactors, cheap energy! as long as you ignore the whole cost of obtaining the fuel and dismantling the reactor afterwards... So any of you daydreaming engineers got any good ideas as to how you would dismantle a space elevator once it reached the end of its life? chop it off at the bottom and let it just float away? Or take it apart from the top until it just falls down...

Hmm I suppose you could just carry on adding stuff to the top until it had enough mass-inertia to drag the whole lot out into space, and then use it to make a space ship.

[Psychedelic Rhino]

As I suggested in my first post, the idea of taking a cable to geosynchronous orbit seems totally insane.

Having a cable reach to LEO seems impossible enough, going out several hundred miles, but going out another ~20,000 miles seems ultra impossible.

For example, let's say the ribbon cables (I foresee at least a two strand link for redundancy) have an average cross section of 12sq/in x 2. That's a ribbon volume of 399 fifty three foot tractor trailers loaded to capacity! So the upper end of the nano ribbon must support that 400 tractor trailers full of ribbon as a minimum, not including centrifugal operating tension, payloads and elevator.

[edit] Actually the ribbon does not have to support its ENTIRE length. There will be a CG point somewhere down the length of the ribbon.

[APCs r Evil]

One thing I haven't heard anyone mention about space elevators is how all that mass hanging off one side of the planet would affect the orbit of not just Earth around the sun but various objects around Earth.

I don't much like the idea of some half thought-out government-run space elevator sending Earth on a collision course with Venus. That's something I'd like to avoid.

[Psychedelic Rhino]

One thing I haven't heard anyone mention about space elevators is how all that mass hanging off one side of the planet would affect the orbit of not just Earth around the sun but various objects around Earth.

I don't much like the idea of some half thought-out government-run space elevator sending Earth on a collision course with Venus. That's something I'd like to avoid.

You haven't heard anything because even if you had a counter balance mass in geosynchronous orbit tethered to the planet the size of an aircraft carrier, you probably wouldn't shift the center of mass between the earth and the object much past a millimeter or two inside the earth's core. I'm quite confident tidal shift of the oceans is several billion times more severe than anything mankind could ever do to appreciably move the earth's CG point by tethering a mass to a geosynchronous orbit. And once you add more elevators, their geosynchronous mass tend to cancel each other out.

I suppose what is conceivable, but extremely unlikely many decades from now, is we have several dozen ribbon systems holding mass the size of several aircraft carriers each. . . small cities. And like a dancer conducting a pirouette, spinning quickly, then spreading her arms in and out, her spin quickens and slows. Imagine a fairy tale world where we increase and decrease the mass on the tethers to completely offset the varying rotation period of the earth and set it to an exact 24 hour period. That's buying 3 or 4 minutes. I imagine that's a crap load of mass to hang out there.

Anyone volunteer to do the math