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Space Travel: would this work?

If the Slingshot doesn't work, something else needs to

Related to this discussion proceeding into practical matters of how to travel to, and perhaps colonize, other systems, Stephen Hawking is appealing to everyone to speed up the R & D effort.
Why?

"We gotta get out of this place
If it's the last thing we ever do!"

'Know The Mind Of God'
Sky News 13:24, Thursday November 30, 2006
Mankind will need to evacuate Earth and live in space to ensure the survival of humanity, Professor Stephen Hawking warned.

The theoretical physicist said Star Trek-style rockets would be used to colonise suitable planets orbiting other stars.

And Prof Hawking said he wants to journey into space himself - and asked Sir Richard Branson for help.

He told the BBC that scientists may be within 20 years of reaching his prediction in A Brief History of Time that mankind would one day "know the mind of God" by understanding all the laws which govern the universe.

And he said this knowledge may be vital to the human race's continued existence.

Prof Stephen Hawking "The long-term survival of the human race is at risk as long as it is confined to a single planet," he said.
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There is more, about Richard Branson sending Prof Hawking up into space sometime soon, but that's the gist of it.

DR
 
Earthborn said:
I don't think it is that flawed. It is probably not even as flawed as many of the concepts included in Star Trek.
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Like the concept of going back in time by slingshotting around the Sun at speeds so much greater than escape velocity that you'd barely have time to say "Howdy" as the Sun zipped past your viewscreen and disappeared in the rear-view mirror?
 
Darth Rotor said:
He told the BBC that scientists may be within 20 years of reaching his prediction in A Brief History of Time that mankind would one day "know the mind of God" by understanding all the laws which govern the universe.
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Hawking hasn't done enough condensed matter physics. If he had, he'd know that having a "master equation" to tell you all the laws of physics doesn't actually solve the problem. Hell, even the three-body Newtonian gravity problem is analytically intractable, let alone the full quantum mechanical states of the 10^20+ particles in the dirt under your fingernail. It would be real nice to get a master equation, but even with it, we won't "know the mind of God", not by a bloody long shot, and certainly not within the next few decades.
 
Hawking is quoted as saying:
"There isn't anywhere like the Earth in the solar system, so we would have to go to another star."
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I think the most practical point anyone can make to speed up space colonization is that we don't need planets to do it. O'Neill colonies can scale up to large cities/states. Ultimately they may turn out to be a much more flexibile place for humans to live: They can have multiple gravity levels, mixed nearby timezones, and no escape velocity. Planets are an extremely ineffective way to deliver surface area to live on, quadrillions of tons of mass to deliver only millions of square miles of surface area. Their crusts are frequently depleted in many interesting elements and their gravity wells are obstacles to getting at the real resource base in the asteroid belt.
 
RecoveringYuppy said:
I think the most practical point anyone can make to speed up space colonization is that we don't need planets to do it. O'Neill colonies can scale up to large cities/states. Ultimately they may turn out to be a much more flexibile place for humans to live: They can have multiple gravity levels, mixed nearby timezones, and no escape velocity. Planets are an extremely ineffective way to deliver surface area to live on, quadrillions of tons of mass to deliver only millions of square miles of surface area. Their crusts are frequently depleted in many interesting elements and their gravity wells are obstacles to getting at the real resource base in the asteroid belt.
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All true, but they have one MAJOR advantage: they don't leak air. That is, in truth, no small thing. Our largest space-faring objects are puny - we do not yet have any experience making large vessels air-tight, or even small vessels air-tight for very long periods of time. We do not know how hard that is to do, but I can guarantee you that anybody who hasn't dealt with vacuum technology is going to seriously underestimate how big a problem that really is. And should an accident ever occur in which a large station would need to resupply with air (something the builders had better plan on), that air can only be obtained from planets, it cannot be mined from asteroids.
 
Cor, this is delving back into history for me, but isn't the gravitational pull of even the sun only a tiny fraction of the speed of light? I thought I remembered working this out once upon a time and that the resultant speed wasn't anywhere near what I would have picked after years of Star Trek.

Anyone have a potential speed for sun's gravity?
 
Ziggurat said:
...All true, but they [planets] have one MAJOR advantage: they don't leak air.
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That is a good point but I suspect we can solve that before we figure out interstellar travel. And we're going to have to solve the leakage problem if we're ever going to build the world ship that the original poster proposed we might use to get to planets in other solar systems.

Ziggurat said:
...that air can only be obtained from planets, it cannot be mined from asteroids.
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Not generally true. The moon and many asteroids have plenty of oxide minerals that can easily provide oxygen. Oxygen, in the form of oxides, is the most common element on the Moon.
 
The Atheist said:
Anyone have a potential speed for sun's gravity?
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You're mixing apples and oranges comparing a speed to an acceleration (gravity). But, IIRC, escape velocity from the sun is about 600 km/sec. That would be the ballistic velocity required to leave the sun from it's surface. And, not coincidentally, the maximum velocity that something can gain from falling in to the Sun. And, you're right, that's approximately standing still compared the speed of light.
 
RecoveringYuppy said:
You're mixing apples and oranges comparing a speed to an acceleration (gravity). But, IIRC, escape velocity from the sun is about 600 km/sec. That would be the ballistic velocity required to leave the sun from it's surface. And, not coincidentally, the maximum velocity that something can gain from falling in to the Sun. And, you're right, that's approximately standing still compared the speed of light.
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Yeah, well played, my wording wasn't the best, but you got it.

Cheers
 
aggle-rithm said:
Like the concept of going back in time by slingshotting around the Sun at speeds so much greater than escape velocity that you'd barely have time to say "Howdy" as the Sun zipped past your viewscreen and disappeared in the rear-view mirror?
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Well, it's at least plausible, if you admit FTL travel (which is kind of like saying that if you admit that 1/0 might not be undefined, it's at least plausible that 1 = 2). Of course the big problem is with FTL travel in the first place. It necessarily permits causality violations.
 
RecoveringYuppy said:
Not generally true. The moon and many asteroids have plenty of oxide minerals that can easily provide oxygen. Oxygen, in the form of oxides, is the most common element on the Moon.
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I haven't crunched the numbers, but if you're going to extract oxygen from metal oxides (minerals), I'm not sure you're really going to be able to hold onto the energy advantage you get from staying in space rather than going planet-side and launching back out into space.
 
aggle-rithm said:
Mars does. It has practically none left.
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Not over time scales we're interested in, it doesn't. If you want to talk about hundreds of millions of years it took for mars to lose much of its atmosphere, well, there's almost no chance we could ever seal a spaceship that well.
 
Ziggurat said:
I haven't crunched the numbers, but if you're going to extract oxygen from metal oxides (minerals), I'm not sure you're really going to be able to hold onto the energy advantage you get from staying in space rather than going planet-side and launching back out into space.
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I suppose that depends on the planet and how far away from it you are.

It also depends on the various costs of energy. If you've got more specifics I'm always willing to crunch numbers.

I am fairly sure that the energy recovered in moving minerals from the Moon's surface to LEO (Low Earth Orbit) is approximately the same as the energy required to reduce those minerals to elements. So I don't how we could gain anything by "going planet-side". But an accurate specific example would change my mind.
 
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