Space Elevators and Other Alternatives

[JaredJames]

A hollow asteroid for example would be a *much* safer and more stable place for humans to live than this planet, because there wouldn't be any tsunamis, climate change, super-volcanoes, etc. and they would be out Earth's gravity well so space travel would be very cheap.

Are you just ignoring all the problems that go with such an idea?

Let's just start with radiation - we have a lovely atmosphere to deal with the majority of it, what does an asteroid have?

 

[mistergrinch]

A hollow asteroid has thick rock walls to block cosmic rays and solar storms, obviously...

 

[JaredJames]

A hollow asteroid has thick rock walls to block cosmic rays and solar storms, obviously...

How sweet, you make it sound so simple.

 

[mistergrinch]

Simple? Definitely not, but clearly possible once our space industry has reached the asteroids. In general, colonizing space will be the hardest thing human beings have ever attempted, but it's also the most necessary thing if we want to have any kind of long-term future, wouldn't you agree?

 

[JaredJames]

Simple? Definitely not, but clearly possible once our space industry has reached the asteroids. In general, colonizing space will be the hardest thing human beings have ever attempted, but it's also the most necessary thing if we want to have any kind of long-term future, wouldn't you agree?

It's going to be a lot easier to get our food / population under control than to colonise space.

Once we've got those two out of the way, we're good for a few billion years. Long enough for you?

 

[mistergrinch]

We will never get things under control on this planet. There is no reason why we have to accept random catastrophes like tsunamis and super-volcanoes killing millions of people, other than a lack of imagination and ambition!

 

[JaredJames]

You do realize that no other place in the solar system is as hospitable as Earth?

You're only plagued by those things if you live in areas prone to them - when was the last time London was destroyed by a natural disaster?

Obviously, we can't stop them, neither can we relocate everyone. We can work to limit damage and it's a hell of a lot easier to solve our problems here than simply overflow into space - where the problems will continue.

 

[mistergrinch]

Sorry but I don't see what is inhospitable about a suitably designed space habitat like a rotating hollow asteroid. A network of such worlds with an independent industrial base should be able to maintain its technology and population long after Earth civilization has returned to a post-industrial Stone Age or been wiped out by some catastrophe!

 

[Nano-Passion]

Its interesting, across space exploration arguments I usually see two sides. Enthusiasts vs. pessimists of the idea.

I stand somewhere in the middle, though the idea of space exploration/colonization is very exciting to say the least.

 

[JaredJames]

Its interesting, across space exploration arguments I usually see two sides. Enthusiasts vs. pessimists of the idea.

I stand somewhere in the middle, though the idea of space exploration/colonization is very exciting to say the least.

I love the idea of space travel and exploration.

But, I also see the more pressing needs of the planet.

It's a balancing game and on these scales, space travel just doesn't weigh up.

 

[Vanadium 50]

when was the last time London was destroyed by a natural disaster?

Um...1666?

Seriously, while not London, people often forget Lisbon was destroyed by an earthquake in 1755.

 

[sophiecentaur]

What makes me smile is the assurance of the pro-spacers that humans will, somehow, change their basic nature and create ideal environments by starting from scratch on assorted asteroids and small planets. The only reason that we haven't died out already is surely because the Earth is (even now) still capable of absorbing the worst of our irresponsible behaviour.

It may well be possible to battery-rear humans in artificial worlds but to what end? This figure of 10^16 humans all 'living' in the solar system is just so grotesque. What would be the point? Who would benefit from it? How would that solve the situation on an over-crowded Earth? However you do the sums, the cost in energy of getting a person from Earth to somewhere else in the Solar System would be more than they would consume, in other ways, in a lifetime down here. How could one suggest we ship them all off to Mars (equivalent to Australia and the new world as in the past)?

Humane (with an 'e') population regulation is the only solution to a happy future for our life on Earth. It's only the wealthy few who promote such extravagant expense as Space Tourism. Unmanned investigations are such good value for finding out about our universe compared with Buck Rogers type zapping around the Cosmos. Perhaps, when we can honestly say that everyone 'down here' is catered for adequately, there may be a time for a large off-Earth presence.

btw, I am heartened by the number of other contributors on this forum who share my skepticism about all this stuff. A very mature population; not just boy racers.

 

[sophiecentaur]

Um...1666?

Seriously, while not London, people often forget Lisbon was destroyed by an earthquake in 1755.

The 'great fire' was man made and could just as easily be caused in a space station. The difference with Earth bound disasters is the inherent healing process in the natural system of which we are a part. Just leaving Earth wouldn't solve the problem of disasters.

 

[JaredJames]

Um...1666?

My point exactly (although I'm not entirely sure I'd go with it being a natural disaster, a tad too man made for my liking ).

Seriously, while not London, people often forget Lisbon was destroyed by an earthquake in 1755.

Wow, as close as 1755

My point is that there are places on the planet that are relatively 'inactive' so far as these things go and other places that are built right on top of the fault lines.

I agree that there are natural disasters that could affect these areas, but they are 1 in a 10,000 year (or what ever the rather large number is) events that we really don't consider or have need to.

I subscribe very much to the thought of "you build on a volcano/fault line etc, you accept the risk". Poor or otherwise, we know the dangers and it is constant pro vs con.

Anyhow, back to my point, mistergrinch is making far too big a deal out of natural disasters so far as the planet goes. As sophie says, Earth is very good at absorbing the crap we through at it and frankly, I'm not surprised it "lets off some steam" every now and then and don't see how anywhere else in the solar system offers us a safer / more hospitable environment.

 

[bonker]

The thing that gets me with the space elevator is the basic physics. How is angular momentum conserved? The glib response is usually that the Earth is slowed as the payload rises to conserve angular momentum. But this does not address the possibility of the orbiting station being slowed and essentially dragged back to earth, also conserving angular momentum. You'll need to keep sending fuel to keep the station moving to counter this, yes?

 

[mistergrinch]

Sophie that's always the argument of the timid, the fatalists and the non-visionaries, that we have to wait for everything to be perfect where we are before we look for new frontiers. You could have said the same thing to the first humans who left the east African plains, the first Americans who walked over the land bridge, the European explorers or even to the first fish who crawled onto land, and where would you be now? That's just not how these things work, sorry!

In fact it probably will be the mega-rich who make this happen, since they will have the resources and the motivation to leave our chaotic planet if & when things start to get really bad. This drive to expand is some kind of evolutionary imperative that is more powerful than anyone's do-gooder moralizing. Space pioneers will have the opportunity to become the progenitors of a vast population which dwarfs Earth's current population, or even to become the saviors of our species in the event of a truly apocalyptic event, so trying to talk our selfish genes out this adventure is just silly.

 

[mistergrinch]

As far as natural disasters go, do I need to bring up the last super-volcano eruption, Toba, which nearly wiped out the human species? These things are very rare, but potentially so devastating that it makes perfect sense to have a backup population off Earth.

And if you're worried about overpopulation of the solar system, it seems fairly likely that if our civilization reaches that level we will have figured out how to get ourselves to other star systems, and by then we will undoubtedly have found *many* habitable planets which we can settle. The point is, there are probably no practical limits to growth in this universe for the foreseeable future, and since it's not clear that there is any desirable steady-state for our species, the choice is to grow or die. I prefer growth.

 

[sophiecentaur]

The parallel with Earth exploration is just not there, I'm afraid. The cost of the most costly Earth expedition has never been, in real terms, anything to compare with the simplest space adventure. Migration on Earth has always been achievable with very low tech means and the huge numbers of failed attempts didn't cost the rest of a population much. The timescale involved for round the World exploration was not great and there was always the possibility of somewhere to stop for R&R.
What vision is it that the 'visionaries' have? Can you paint a picture of a typical day in the life of a Mars Colonist? Would you really like to be there? The Pilgrim Fathers moved to somewhere which was very very similar to the place they came from and the trip was self-financed.

This space thing is just an extension of the survivalist thing. It's much easier to fantasise about escaping from a poor situation than to think about improving it. Space is not the 'backwoods' and it's nto a way out of a bad situation here.

Why should we want to be "progenitors of a vast population"? How many people can one person relate to? Have you no idea of "pioneering" in your head and exploring what can be done to improve the world a bit? The simple "selfish gene" notion has superceded, didn't cha know? The idea is now that co operation accounts for as much evolutionary success as competition. When populations of an organism get too big, they tend to run into more problems than they can deal with.

Words like adventure, pioneer, evolutionary imperative,explorers all bring to mind past excitements and glories (and which cost a lot of people a lot of grief). It's time to grow up and to see the present, more complex situation which just may not be soluble by buying bigger guns and bigger rockets, fun though they may be.

 

[JaredJames]

mistergrinch, you do realize that "sweeping the problems under the carpet" only solves things in the short term don't you?

So we put colonies in space, why don't they become over populated? Why don't we start having problems with growing populations? At what point between being here and then up there do we suddenly 'forget' our nature and stop doing what we are currently doing to ruin Earth?

You are talking about extremely rare occurrences, so rare that they aren't worth planning for - it's a waste of money.

You have to realize that people don't care what happens 1000, 10000, 1000000 years down the line, they only care about the here and now. They don't care that spending trillions now *may* (and yes, spending the money guarantees nothing) give some person a chance to live off Earth under identical conditions that we have now, minus the threat of natural disaster.

And this is all before we factor in the other dangers of living in space and how only minor problems on Earth are incredibly serious and potentially deadly in space. We effectively take a natural, 1 in a 10,000 year event and replace it with a far more serious and far more likely problem to arise in space.

 

[mistergrinch]

I can paint a picture of a day on Mars, and I'd love to be there! I understand that not everyone has this sense of adventure and curiosity, and those folks can do what such people have always done: stay home where it's safe. This is why I'm putting my hopes in bold entrepreneurs more than dull, risk-averse space bureaucracies at this point -- governments tend not to attract the kinds of people you need for this enterprise.

Debating this issue is like debating religion and just as pointless -- people just see the world differently. Having said that, I won't stop evangelizing for space exploration, because for me it literally is a kind of religion, part of a cosmic religion I subscribe to, inspired by great thinkers like these:

"We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars." —Carl Sagan

"There is no way back into the past; the choice, as Wells once said, is the universe—or nothing. Though men and civilizations may yearn for rest, for the dream of the lotus-eaters, that is a desire that merges imperceptibly into death. The challenge of the great spaces between the worlds is a stupendous one; but if we fail to meet it, the story of our race will be drawing to its close. Humanity will have turned its back upon the still untrodden heights and will be descending again the long slope that stretches, across a thousand million years of time, down to the shores of the primeval sea." —Arthur C. Clarke

"Teetering here on the fulcrum of destiny stands our own bemused species. The future of the universe hinges on what we do next. If we take up the sacred fire, and stride forth into space as the torchbearers of Life, this universe will be aborning. If we carry the green fire-brand from star to star, and ignite around each a conflagration of vitality, we can trigger a Universal metamorphosis. Because of us, the barren dusts of a million billion worlds will coil up into the pulsing magic forms of animate matter. Because of us, landscapes of radiation blasted waste, will be miraculously transmuted: Slag will become soil, grass will sprout, flowers will bloom, and forests will spring up in once sterile places. Ice, hard as iron, will melt and trickle into pools where starfish, anemones, and seashells dwell — a whole frozen universe will thaw and transmogrify, from howling desolation to blossoming paradise. Dust into Life; the very alchemy of God". —Marshall T. Savage

“If the human species, or indeed any part of the biosphere, is to continue to survive, it must eventually leave the Earth and colonize space. For the simple fact of the matter is, the planet Earth is doomed… Let us follow many environmentalists and regard the Earth as Gaia, the mother of all life (which indeed she is). Gaia, like all mothers, is not immortal. She is going to die. But her line of descent might be immortal. . . . Gaia’s children might never die out–provided they move into space. The Earth should be regarded as the womb of life—but one cannot remain in the womb forever.” —Frank Tipler

 

[ngc1333]

Air pollution kills millions of people every year, just to put things in prospective.

I sort of see where you're coming from but two wrongs don't make a right.

Are you certain that air pollution was "wrong"? The only alternative I can see would have been to avoid the industrial revolution.

The number of deaths caused by some sources of pollution has been reduced greatly, by legislation.

That's true, but we could still do a lot more. We could shut down all non-essential industries to reduce our power needs, outlaw non-essential driving . . . Nobody wants to do that. We accept pollution as the cost of our lifestyle. I don't see why we should insist on zero casualties when it comes to space travel.

 

[russ_watters]

A hollow asteroid for example would be a *much* safer and more stable place for humans to live than this planet, because there wouldn't be any tsunamis, climate change, super-volcanoes, etc. and they would be out Earth's gravity well so space travel would be very cheap.

It also wouldn't have any of the good things about living on earth: soil on which to grow food, air to breathe and water to drink.

We will never get things under control on this planet. There is no reason why we have to accept random catastrophes like tsunamis and super-volcanoes killing millions of people, other than a lack of imagination and ambition!

Don't let your imagination control you. It's making you think illogically. The only natural disasters ever to kill millions of people have been diseases and living on an asteroid doesn't help with that. In the grand scheme of things, few natural disasters are really that big of a problem and most of those that are are only a problem to 3rd world countries - so the way to deal with them is to fix third world countries. Ie, the earthquake in Hati and the tsunami in Indonesia each killed about 250,000 people. The earthquake and tsunami in Japan was about the same intensity and appears to have killed on the order of 10,000 people. There are many reasons for the difference, but the main reason is that Japan is more developed. So, for example, their buildings don't all collapse in an earthquake.

So we don't really need to move to an asteroid to deal with natrual disasters well enough for them to be only minor problems, we just need to have countries be developed enough to prevent them from being major problems.

 

[russ_watters]

It may well be possible to battery-rear humans in artificial worlds but to what end? This figure of 10^16 humans all 'living' in the solar system is just so grotesque.

Agreed. The idea isn't even science fiction, it's fantasy. We have no clue if such things will be possible, much less what such a society would even look like. Fantasizing about such things - which if even possible are at least hundreds if not thousands of years in our future - are a far cry away from evaluating the still science fiction but at least theoretically possible in the next 50 years space elevator concepts.

 

[russ_watters]

As far as natural disasters go, do I need to bring up the last super-volcano eruption, Toba, which nearly wiped out the human species?

If you think it's relevant, by all means...But as much as you're fantasizing is wildly disconnected from current reality, I don't expect you'll succeed in making it connect.

These things are very rare, but potentially so devastating that it makes perfect sense to have a backup population off Earth.

Heh. No. What do I care about the survival of the species? I live on earth, so if a massive comet comes and wipes us all out, I wouldn't much care if there is a "backup" somewhere else. I'll be dead, so it won't provide me any comfort.

And that's besides the fact that we have no capability to do it, so it certainly does not make any sense.

...and since it's not clear that there is any desirable steady-state for our species, the choice is to grow or die. I prefer growth.

Population growth is already leveling-out and has a good chance of reaching that steady-state this century.

I can paint a picture of a day on Mars, and I'd love to be there! I understand that not everyone has this sense of adventure and curiosity, and those folks can do what such people have always done: stay home where it's safe.

I thought you said it was safer in space? So now you acknowledge it isn't?

This is getting silly.

Having said that, I won't stop evangelizing for space exploration, because for me it literally is a kind of religion...

On that much, at least we agree. The trouble is, this is a science forum, not a religion forum. So unless this discussion can return from the realm of religious fantasy to the realm of scientific reality, it will need to be shut down.

 

[Nano-Passion]

Wait wait, I love your enthusiasm mistergrinch, but please don't get my topic shut down. :( So let's keep this to the realm of scientific reality. ^.^ With that said:

Farming a new Earth environment in a different habitat sort of speak seems scientifically feasible. I wonder if we have the scientific capabilities ( such as air circulations, growing food, soil, water circulations, etc. )?

I mean, the knowledge and technology seems to be there. We can take zygotes of different animals aboard the space shuttle. Perhaps we can engineer a large amount of soil from surrounding atoms by combining and arranging them in a certain way (nanotechnology anyone?). With that, we can farm whole lands and have a big growth in animals. With 3d printing (strong enough?) or perhaps engineering the material needed in the selected habitat of choice we can extend our living space as long as we collect the elements we need. We can also farm our own energy with our ever better increasing energy technology.

The only thing that seems to hold us back is energy usage to get there (money) and the question: is it worth it?

 

[mistergrinch]

If you doubt the scientific plausibility of space colonies, please google Gerard O'Neill, a physicist I'm sure many of you know about. He and his students at MIT created detailed plans for orbiting colonies back in the 1970's that, as far as I know, are still sound. What exactly about space colonization do people find so fantastical?

I understand that it's very unlikely a natural catastrophe will wipe out humanity, but there are many other threats which are potentially worse -- Astronomer Royal Martin Rees only gives us a 50% chance of surviving this century! But my main point was that there can be much less chaos and danger and a higher quality of life in habitats designed from the ground up for humans (at least after a period of dangerous pioneering work, which is the risk I was talking about), but it takes some imagination to see that. If you want to call such things fantasy then we might as well not be discussing space elevators either.

I'm very surprised at the can't-doism and negativity I'm hearing on a forum of physicists. I'm trying to imagine what people of Feynman's generation would have said on these topics compared to you folks. Of course they were busy building rockets to the moon instead of chatting on internet forums, which might be a big part of our problem today. When I hear people talking like this I’m reminded of the scientists who confidently claimed in the late 19th century that heavier than air flight was impossible/impractical/contrary to God’s plan etc. and in the 1930's said similar things about space flight. This lack of hubris makes me very sad!

"There shall be wings! If the accomplishment be not for me, 'tis for some other." –Leonardo da Vinci

 

[JaredJames]

I understand that it's very unlikely a natural catastrophe will wipe out humanity, but there are many other threats which are potentially worse -- Astronomer Royal Martin Rees only gives us a 50% chance of surviving this century!

So? I give us a 100% chance of surviving this century. It doesn't mean anything. They are non-sense comments.

But my main point was that there can be much less chaos and danger and a higher quality of life in habitats designed from the ground up for humans (at least after a period of dangerous pioneering work, which is the risk I was talking about), but it takes some imagination to see that. If you want to call such things fantasy then we might as well not be discussing space elevators either.

Humans on habitat = humans on Earth. We would over consume and over populate just the same. The threat of disaster and disease is ever present. Again, why do you believe the humans up there would be different to those down here?

I'm very surprised at the can't-doism and negativity I'm hearing on a forum of physicists.

This stems from the fact it's a forum of physics, not a forum of fantasy. The physics don't allow us to do this - this is the key point you are failing to grasp. Our current technology means we either need the raw materials in situ or we need to carry them with us - even when in situ we'd still need enough with us until a processing system is up and running.

I'm trying to imagine what people of Feynman's generation would have said on these topics compared to you folks. Of course they were busy building rockets to the moon instead of chatting on internet forums, which might be a big part of our problem today.

Or, shall we stick with reality and realize that they had funding and were supported by the public? They were in the space race. First man in space, first man on the moon, big things. After those events, interest died and now people are more concerned with things that actually affect them.

When I hear people talking like this I’m reminded of the scientists who confidently claimed in the late 19th century that heavier than air flight was impossible/impractical/contrary to God’s plan etc. and in the 1930's said similar things about space flight. This lack of hubris makes me very sad!

Out of curiosity, I take it you are a Nuclear Engineer, Aerospace Engineer, Mechanical Engineer, Astrologist, Cosmologist, Physicist, Biologist, Chemist, or any space related field? As such, I take it you are speaking from vast experience and/or knowledge in said fields? And by extension not speaking from a purely fantastical point of view - which is all you have demonstrated so far.

 

[sophiecentaur]

The thing that gets me with the space elevator is the basic physics. How is angular momentum conserved? The glib response is usually that the Earth is slowed as the payload rises to conserve angular momentum. But this does not address the possibility of the orbiting station being slowed and essentially dragged back to earth, also conserving angular momentum. You'll need to keep sending fuel to keep the station moving to counter this, yes?

Which bit of Physics tells you this would happen? Of course the tether would be tilted back a fraction but what would make it fall down?

 

[bonker]

Which bit of Physics tells you this would happen? Of course the tether would be tilted back a fraction but what would make it fall down?

Conservation of momentum and Newtons third law require both the Earth to slow and the satellite to get pulled down out of orbit.

"Tilted back" as you put it actually means pulled back to earth. This is basic mechanics, angular momentum must be conserved.

 

[Nano-Passion]

I sense some sort of fallacy in the argument. It appears the argument just keeps going in circle. mistergrinch I know you feel very strongly but that feeling won't win you the argument. Put a little more scientific support, its really side-tracking. I don't want my topic closed.

With that said, I hope cheaper ways of getting into space comes into reality. I mean the 10,000-11,000 dollars per pound is just too much.

Space elevator seems flawed.. What are other future alternatives?

 

[sophiecentaur]

Conservation of momentum and Newtons third law require both the Earth to slow and the satellite to get pulled down out of orbit.

"Tilted back" as you put it actually means pulled back to earth. This is basic mechanics, angular momentum must be conserved.

Your "Basic Mechanics" needs to be applied correctly. The total angular momentum will, of course, be conserved and so the Day would be shorter by an amount you couldn't measure. Irellevant.
The tilting I refer to is just a smallish angle which will bring the tethered mass to a position at which the forces will be balanced.
I think you need to re-consider your position on this and bear in mind that the theory of the proposal has been gone over and verified by far smarter people than you (Niether of us can doubt this and no offense should be taken). If you start off by assuming that you have got something wrong in your reasoning and that you won't overturn the whole of Physics then you can get to understand why it Will work, rather than Won't work.

 

[Zentrails]

Which bit of Physics tells you this would happen? Of course the tether would be tilted back a fraction but what would make it fall down?

The fundamental problem of Space Elevator physics that I keep seeing is mixing up the physics of "really high towers" and the physics of geosynchronous orbiting objects. There's no question you can run a tether down from an object in geosynchronous orbit as long as you simultaneously move a counterweight in the other direction.

The real question is how close to the Earth can you get with that tether before the equilibrium becomes impossible to maintain.

 

[D H]

There's no question you can run a tether down from an object in geosynchronous orbit as long as you simultaneously move a counterweight in the other direction.

No question? The longest tether experiment to date was TSS-1R, which deployed a satellite at the end of tether. The tether was eventually reeled out to a length of 19.7 km. This was one of those NASA "successes" never to be repeated again because it was a success on paper only.

We haven't the foggiest idea how to safely reel out a 20 km-long cable, let alone scale up by 3+ orders of magnitude. There are huge questions as to whether "you can run a tether down from an object in geosynchronous orbit as long as you simultaneously move a counterweight in the other direction".

 

[sophiecentaur]

I don't think anyone is considering doing this in the next few weeks.

But, as a project, it has a lot more feasibility than many of the whacky schemes I have read about in some other places on the web! It certainly has some elegance.

 

[Zentrails]

No question? The longest tether experiment to date was TSS-1R, which deployed a satellite at the end of tether. The tether was eventually reeled out to a length of 19.7 km. This was one of those NASA "successes" never to be repeated again because it was a success on paper only.

We haven't the foggiest idea how to safely reel out a 20 km-long cable, let alone scale up by 3+ orders of magnitude. There are huge questions as to whether "you can run a tether down from an object in geosynchronous orbit as long as you simultaneously move a counterweight in the other direction".

I agree with you. I should have said that there is no question that the physics is sound as long as you can figure out a way to keep all sections of the tether at the correct tangential velocity, no easy feat.

Can you tell me if that tether was stationary with respect to it's center of mass or was it rotating? Rotation would be the result I would expect if you simply shot a tether towards the Earth and another one directly away from the Earth at the same time using something similar to the TOW antitank missile. I would expect the thing to start rotating, then eventually becoming a tangled mess unless you could keep it "taut" somehow.

I was in the US Navy and we used to routinely launch hundreds of expendable bathythermographs:

http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_09.htm

with no failures that I can remember, so perhaps because of that, I probably incorrectly think a tether wouldn't be too hard to send out in space as long as you could "send" it out at a reasonably constant velocity and keep tension between the end going out and the reel somehow.

Maybe you could put a small ion engine on the projectile to give it a little boost to correct the tangential velocity as it is reeling out? I would think it would be a considerable engineering challenge, but the physics is pretty simple. Obviously as the tether gets longer, the difficulties increase, probably exponentially.

They were able to measure an induced current as well in that tether experiment didn't they? suggesting a possible future source of power for orbiting devices?

I, too, wonder why the tether experiments have not continued, it is fascinating to speculate about. Maybe that experiment was not very successful at all, like you said.