Slow Space Elevator

[Kristopher]

Re: Slow Space Elevator

 

Again, transit times. I asked before, but didn't see an answer. How long does it take to assemble, fuel, and preflight the Space Shuttle for launch? Assuming the weather cooperates. Aren't there months at a time when it's too cold or too windy to launch the shuttle?

 

SSTO, even in an emergency, is going to involve more prep time than taking a car out of a garage.

 

If the materials for building the thing had held up, the planned turnaround time for Venture Star was under... 72 hours, IIRC. Can't find a reference right now.

[McCoy]

Re: Slow Space Elevator

 

If the materials for building the thing had held up' date=' the planned turnaround time for Venture Star was under... 72 hours, IIRC. Can't find a reference right now.[/quote']

But it didn't. Handwavium.

 

Anyone got the original spects on the Space Shuttle? IIRC before it was built the turnaround time was suppost to be weeks. Turned out to be months.

[Sundog]

Re: Slow Space Elevator

 

But it didn't. Handwavium.

 

Anyone got the original spects on the Space Shuttle? IIRC before it was built the turnaround time was suppost to be weeks. Turned out to be months.

 

 

To be fair, a large part of that was the reapplication of the heat shield. The original model wasn't supposed to need an add-on shield, but Congress balked at the cost of making it out of Titanium.

 

Oddly enough, that probably saved the program. Later modeling showed that the Titanium shell would not have withstood the temperature of reentry the way NASA had though it would

 

Nyrath - very cool links.

[Kristopher]

Re: Slow Space Elevator

 

But it didn't. Handwavium.

 

Anyone got the original spects on the Space Shuttle? IIRC before it was built the turnaround time was suppost to be weeks. Turned out to be months.

 

So why expect a beanstalk to turn out any more like some hope?

[Captain Obvious]

Re: Slow Space Elevator

 

So why expect a beanstalk to turn out any more like some hope?

 

Most things don't turn out as planned. You can't just quit on them because of that.

[The Weapon]

Re: Slow Space Elevator

 

Only if you have a steerable baloon. Rocoons were used in the 50's' date=' and I believe maybe even back to the 40's, when altitude was all that mattered, but they introduce an element of positional uncertainty to the launch that would have to be paid for later in delta-v if you destination was anything other than "up."[/quote']

 

I can't see how. Being even 500kms off course just means that you have to add 100m/s of velocity for 5,000 seconds (less than an hour and a half) and then take it off again. That's a lot less than the thousands of m/s you have to add to get up to orbit. Take a day and it's 4 times less. The real problem is that balloons don't add a lot to your energy. Sure your up a bit, but the real energy problem is going fast enough relative to the ground to stay there.

[The Weapon]

Re: Slow Space Elevator

 

There's plenty of use for high tensile-strength materials in a rocket. For example, the fuel tank. These are pretty complex structures, after all.

 

And there's no question about the superiority of the energetics of a space elevator. It's just that the economics doesn't reduce to the energetics. You have to build the darn thing. And, apparently, support the nontrivial costs of long transit times.

 

No doubt high-tensile materials will help in a rocket but not that much. The problem with beanstalks is a a very long thing has to support it's weight. The lower the strength-to-weight ratio the more it has to weigh so the more weight it needs to support etc. It's an exponential function like (weight = payload * e ^ (1/strength-to-weight). Adding to stw ratio makes a big difference.

 

The costs of long transit times are pretty trivial for most things. The projects are long term and sophisticated enough that they'll be planned to the nth degree so it should be rare that someone says "Oh drat, we forgot to get the xxx, we'll have to stop the project while it's delivered.". Delivering things slowly basically costs interest rate * delay. Even if it took a month at 24% (a pretty high rate) that's only 2%. Beanstalks save you more than that if they can be made. The other problem is personnel. Again not that expensive to waste their time compared to the cost of rocketing them up (unless they're truly unique individuals). And they don't even waste that time, they can train and do paperwork on the way up*.

 

* Well electron work really, since they're not going to be sending paper back down to earth.

[McCoy]

Re: Slow Space Elevator

 

So why expect a beanstalk to turn out any more like some hope?

The physics of the thing. Once the tether is in place it is for all intents and purposes a stationary object. Cable cars can be redesigned. Different power sources experimented with. Multiple cables strung, easier and cheaper than the first. More suited to incremental design change than a rocket.

[Lawnmower Boy]

Re: Slow Space Elevator

 

 

Delivering things slowly basically costs interest rate * delay.

 

That's an interesting claim. Having never done any formal business studies, I'd be interested in its origins, because I do have to deal with the costs of slow delivery, which for me are dominated by storage issues.

 

Anyway, the issue raised by the revelation that beanstalks are slow has less to do with turnaround than with the additional costs of environmental conditioning in transit.

The case here is twofold. First, turnaround (for any kind of 'spaceplane') is a red herring. If it takes a year to turn your spaceplane around, and you have 365 of them, then you can offer one flight a day. This is a huge advantage for spaceplanes over space elevators, although not one that I was going to emphasise.

Second, much of the discussion has turned on energetics, where it should turn on economics. I've brought up the urban public transit analogy before. The nature of service between two nodes is not determined by an analysis of the favourable outcomes delivered, or there would be a separated grade rail link providing service to every block.

 

I can't emphasise enough that it is not. It is determined by whether the fares charged will service the capital investment. How much money is there to be made from space? How much will the beanstalk cost? In the financial space between these two questions will be found the case for or against building it.

(In the vanishingly unlikely case that it will ever be feasible to spin a 23,000 long mile cable!)

 

The proponents of the beanstalk haven't addressed this much, if at all. What they have talked about is the energetic advantage of the beanstalk over spaceplane. This is all well and good, but if this is the entire economic case for the beanstalk, than any erosion of the energetic advantage has to be greeted with alarm. Better spaceplanes erode it. So does the revelation that we will have to provide human passengers (and some other kinds of cargo) with maintenance for a 4 week transit.

[Vondy]

Re: Slow Space Elevator

 

I'm not sure there's much dirtside profit in space beyond gas mining (such as helium-3), some specific manufacturing or bioengineering that would benefit from 0G, or the construction of sufficient SPS arrays to give an essentially limitless power source. Unless we actually move to building orbital colonies I'm not sure a space-elevator (beanstalk style) would ever be economically viable.

[Sundog]

Re: Slow Space Elevator

 

I'm not sure there's much dirtside profit in space beyond gas mining (such as helium-3)' date=' some specific manufacturing or bioengineering that would benefit from 0G, or the construction of sufficient SPS arrays to give an essentially limitless power source. Unless we actually move to building orbital colonies I'm not sure a space-elevator (beanstalk style) would ever be economically viable.[/quote']

 

 

The point isn't making the beanstalk economically viable; it's making building the colonies economically viable.

[McCoy]

Re: Slow Space Elevator

 

I'm not sure there's much dirtside profit in space beyond gas mining (such as helium-3)' date=' some specific manufacturing or bioengineering that would benefit from 0G, or the construction of sufficient SPS arrays to give an essentially limitless power source. Unless we actually move to building orbital colonies I'm not sure a space-elevator (beanstalk style) would ever be economically viable.[/quote']

 

The point isn't making the beanstalk economically viable; it's making building the colonies economically viable.

Not to mention all the things manufactured in ziggy from asteroid steel.

[Vondy]

Re: Slow Space Elevator

 

The point isn't making the beanstalk economically viable; it's making building the colonies economically viable.

 

Which requires someone to convince the lowly ground pounders planet-side that its economically viable for them to have colonies in the first place. So, to work several steps ahead the way you want to, you need to formulate an argument as to how the colonies profit the homeworld. And I don't mean a hundred years or more after the project begins. I mean within decades. You have to sell a tangible benefit.

 

Considering the astronomical cost and materials for sufficient beanstalks to build colonies in a timely fashion, and that doesn't deal with the space-born infrastructure you will need for such an endeavor (more astronomical costs), let alone colony construction itself (even more astronomical costs) I don't think you will be able to convince anyone to just go for all three steps without justifying the profit margin on each step of the project.

 

You're going to have to make each step economically worthwhile. If you say do this now and 2-3 steps down the road (after your lifetime) there will be benefits IT WILL NEVER HAPPEN. Our global culture simply isn't that evolved. Now, I can think of ways to make each step economically attractive while building towards the greater goal, but sitting around saying "making the beanstalk economical isn't the point..." will kill the project dead faster than any technological hurdles will.

 

It has to be economical. Else, no one will build it.

[The Weapon]

Re: Slow Space Elevator

 

That's an interesting claim. Having never done any formal business studies, I'd be interested in its origins, because I do have to deal with the costs of slow delivery, which for me are dominated by storage issues.

 

Anyway, the issue raised by the revelation that beanstalks are slow has less to do with turnaround than with the additional costs of environmental conditioning in transit.

The case here is twofold. First, turnaround (for any kind of 'spaceplane') is a red herring. If it takes a year to turn your spaceplane around, and you have 365 of them, then you can offer one flight a day. This is a huge advantage for spaceplanes over space elevators, although not one that I was going to emphasise.

Second, much of the discussion has turned on energetics, where it should turn on economics. I've brought up the urban public transit analogy before. The nature of service between two nodes is not determined by an analysis of the favourable outcomes delivered, or there would be a separated grade rail link providing service to every block.

 

I can't emphasise enough that it is not. It is determined by whether the fares charged will service the capital investment. How much money is there to be made from space? How much will the beanstalk cost? In the financial space between these two questions will be found the case for or against building it.

(In the vanishingly unlikely case that it will ever be feasible to spin a 23,000 long mile cable!)

 

The proponents of the beanstalk haven't addressed this much, if at all. What they have talked about is the energetic advantage of the beanstalk over spaceplane. This is all well and good, but if this is the entire economic case for the beanstalk, than any erosion of the energetic advantage has to be greeted with alarm. Better spaceplanes erode it. So does the revelation that we will have to provide human passengers (and some other kinds of cargo) with maintenance for a 4 week transit.

 

The energetic benefits of better materials are minimal for spaceplanes compared to the benefits for beanstalks. Double the strength of materials and you maybe reduce the material requirements for the spaceplane by 40% not including the fuel, if you're lucky. The fuel is most of the weight though. The materials reduction for beanstalks (and by implication their construction energetic requirements) is square rooted by the same increase!

I don't see how storage is a problem for slow delivery times unless there is an unpredictable change in requirements. Even then I don't see how it's hard to store extras in space.

I don't imagine that the cost of enviromental conditioning would be high compared to cost of transit. I mean it's just some food, O2 and scrubbers, all pretty basic really. And of course by the time we get beanstalks we'll have edible GMO algea so the weight will be some multiple of the amount you eat each day. This is far easier to make than the beanstalk.

[The Weapon]

Re: Slow Space Elevator

 

That's an interesting claim. Having never done any formal business studies, I'd be interested in its origins, because I do have to deal with the costs of slow delivery, which for me are dominated by storage issues.

 

Anyway, the issue raised by the revelation that beanstalks are slow has less to do with turnaround than with the additional costs of environmental conditioning in transit.

The case here is twofold. First, turnaround (for any kind of 'spaceplane') is a red herring. If it takes a year to turn your spaceplane around, and you have 365 of them, then you can offer one flight a day. This is a huge advantage for spaceplanes over space elevators, although not one that I was going to emphasise.

Second, much of the discussion has turned on energetics, where it should turn on economics. I've brought up the urban public transit analogy before. The nature of service between two nodes is not determined by an analysis of the favourable outcomes delivered, or there would be a separated grade rail link providing service to every block.

 

I can't emphasise enough that it is not. It is determined by whether the fares charged will service the capital investment. How much money is there to be made from space? How much will the beanstalk cost? In the financial space between these two questions will be found the case for or against building it.

(In the vanishingly unlikely case that it will ever be feasible to spin a 23,000 long mile cable!)

 

The proponents of the beanstalk haven't addressed this much, if at all. What they have talked about is the energetic advantage of the beanstalk over spaceplane. This is all well and good, but if this is the entire economic case for the beanstalk, than any erosion of the energetic advantage has to be greeted with alarm. Better spaceplanes erode it. So does the revelation that we will have to provide human passengers (and some other kinds of cargo) with maintenance for a 4 week transit.

 

The energetic benefits of better materials are minimal for spaceplanes compared to the benefits for beanstalks. Double the strength of materials and you maybe reduce the material requirements for the spaceplane by 40% not including the fuel, if you're lucky. The fuel is most of the weight though. The materials reduction for beanstalks (and by implication their construction energetic requirements) is square rooted by the same increase!

 

I don't see how storage is a problem for slow delivery times unless there is an unpredictable change in requirements. Even then I don't see how it's hard to store extras in space.

 

I don't imagine that the cost of enviromental conditioning would be high compared to cost of transit. I mean it's just some food, O2 and scrubbers, all pretty basic really. And of course by the time we get beanstalks we'll have edible GMO algea so the weight will be some multiple of the amount you eat each day. This is far easier to make than the beanstalk.

[Sundog]

Re: Slow Space Elevator

 

Which requires someone to convince the lowly ground pounders planet-side that its economically viable for them to have colonies in the first place. So, to work several steps ahead the way you want to, you need to formulate an argument as to how the colonies profit the homeworld. And I don't mean a hundred years or more after the project begins. I mean within decades. You have to sell a tangible benefit.

 

Considering the astronomical cost and materials for sufficient beanstalks to build colonies in a timely fashion, and that doesn't deal with the space-born infrastructure you will need for such an endeavor (more astronomical costs), let alone colony construction itself (even more astronomical costs) I don't think you will be able to convince anyone to just go for all three steps without justifying the profit margin on each step of the project.

 

You're going to have to make each step economically worthwhile. If you say do this now and 2-3 steps down the road (after your lifetime) there will be benefits IT WILL NEVER HAPPEN. Our global culture simply isn't that evolved. Now, I can think of ways to make each step economically attractive while building towards the greater goal, but sitting around saying "making the beanstalk economical isn't the point..." will kill the project dead faster than any technological hurdles will.

 

It has to be economical. Else, no one will build it.

 

Not so. You simply need a non-economic reason to build it.

 

The Apollo program provided basically nothing in terms of tangible economic benefit. Scientifically it was a marginal success - we actually learned more in a few months of the Skylab program than we did in the 10+ years of Apollo. We got some nice rocks, learned about the nature of the lunar surface, and solved some tricky engineering problems. Any or all of which could have been done by unmanned probe systems.

 

And it threw our national prestige into the stratosphere. Which was the REAL reason for doing it at all.

 

Economics is NOT the be all and end all of why we do things. If we an convince the populace or the government to do this for other reasons, it can be done.

[Vondy]

Re: Slow Space Elevator

 

Not so. You simply need a non-economic reason to build it.

 

/snip

 

Economics is NOT the be all and end all of why we do things.

 

I agree. Immigrating wasn't the best economic decision I could have made. And yet I made it. On the other hand, where's this glorious non-economic reason that will sell the world on the idea? Proponents of colonies and space elevators have been proposing "good non economic reasons" since the early 60's. They've been saying "we just have to convince the public" for that long, too. I don't see any colonies or space elevators. I don't see a serious interest in making them happen, either. Simply put: it hasn't happened.

 

Bottom line: the proof is in the pudding. More rock, less talk. Lay it on me: give us the big reason that will sell the world on it. If you don't have one that will get people fired up and moving in the here and now, then I recommend you stop spitting into the wind. Because the world still isn't convinced its worth doing. Ideals are great. I operate on them. But there comes a point where an idealist has to get realistic in terms of achieving his goals. The fastest, most pragmatic, most effective way to make this happen is demonstrate a profit margin and make the project economical each step along the way. Because the bottom line is that someone has to pay for it. The costs are not trivial.

 

The government may be willing to build one if it becomes convinced its cheaper than other launch options (though being forced to maintain multiple launch options is going to be a hard sell), but enough for a colonization project? That's more than a few. Plus additional infrastructure.

 

Stop dreaming. Get real. Its the only way it will happen.

[Kristopher]

Re: Slow Space Elevator

 

The physics of the thing. Once the tether is in place it is for all intents and purposes a stationary object. Cable cars can be redesigned. Different power sources experimented with. Multiple cables strung' date=' easier and cheaper than the first. More suited to incremental design change than a rocket.[/quote']

 

Why expect the tether to work as is hoped? Why expect the concept to work as hoped?

 

Ideas fail all the time, and it strikes me as foolish to condemn all research into reusable lifting vehicles to the dustbin on the hope that you can fling a string into space and then run something up it.

[Kristopher]

Re: Slow Space Elevator

 

Some would say that the point of going into space is going into space, and the point of putting a person on Mars is to put a person on Mars.

[jtelson]

Re: Slow Space Elevator

 

Some would say that the point of going into space is going into space' date=' and the point of putting a person on Mars is to put a person on Mars.[/quote']

 

Why Mars? Because it's what's next. I just wish more people understood and agreed with that

[Vondy]

Re: Slow Space Elevator

 

I'm all for research and exploration for its own sake. So, I won't debate the point beyond the caveat: "insofar as there is a surplus of resources to apply to the endeavor." At the same time, you have to sell the idea to people who don't necessarily share such high falutin' intellectual notions. And you have to compete for those surplus resources.

 

Wishing for a sudden, mass ideological conversion is daydreaming. You have to make an attractive, pragmatic argument to buttress the unfettered "to infinity and beyond" ideal. What's more, in doing so you come up with ways to help finance it and relieve some of the overhead in terms of "surplus resources" that will ultimately be allotted amongst competing interests.

 

This is a big problem with being a dreamer, and dreamers in general. Its all too common to expect others to be inspired by our dreams for their own sake (I mean, we're inspired right?) instead of laying out how our dreams benefit them in tangible terms they are willing to work towards in the here and now.

[Nyrath]

Re: Slow Space Elevator

 

Why expect the tether to work as is hoped? Why expect the concept to work as hoped?

 

Ideas fail all the time, and it strikes me as foolish to condemn all research into reusable lifting vehicles to the dustbin on the hope that you can fling a string into space and then run something up it.

Why expect the tether to fail? Why expect the concept to fail?

 

And if a company starts developing a space elevator, do you really think that a law will be passed making it illegal to develop SSTO? For that matter, if people are now working on SSTO, why should it be illegal to work on a space elevator?

 

These matters will be decided by market forces. If a viable design for a space elevator is not forthcoming, the venture capitalist who bankrolled development will be out some cash.

 

But if a viable design appears and manages to be implemented, those clients with huge payloads they want to get into orbit will naturally take their business to the less expensive option. Then as I said before, the space elevator will become the orbital version of the trucking and rail road train transport company, and the SSTO will become overnight air freight.

[Kristopher]

Re: Slow Space Elevator

 

Why expect the tether to fail? Why expect the concept to fail?

 

Because most ideas do.

 

And it's more likely to fail than reusable lifting solutions (SSTO, MSTO, whatever) because there's more to it that's unproven and more that's hypothetical. We've built a reusable MSTO, and it was pretty good for a first try. The two catastrophic failures were caused by human error (in the system at NASA, etc, not crew), and not by inherent flaws in the concept.

[McCoy]

Re: Slow Space Elevator

 

Because most ideas do.

 

And it's more likely to fail than reusable lifting solutions (SSTO, MSTO, whatever) because there's more to it that's unproven and more that's hypothetical. We've built a reusable MSTO, and it was pretty good for a first try. The two catastrophic failures were caused by human error (in the system at NASA, etc, not crew), and not by inherent flaws in the concept.

The big thing you are overlooking is that unlike rockets, once the teather is in place it has no moving parts. It's just -- there.

 

Beanstalk vs SSTO is a false delema. If I had to make the decision and could only back one program, I'd go with big, dumb boosters, suchas the Saturn V. IIRC Saturn V could boost larger payloads to LEO cheaper than the Shuttle. Skylab, for example.

[Querysphinx]

Re: Slow Space Elevator

 

Which requires someone to convince the lowly ground pounders planet-side that its economically viable for them to have colonies in the first place. So, to work several steps ahead the way you want to, you need to formulate an argument as to how the colonies profit the homeworld. And I don't mean a hundred years or more after the project begins. I mean within decades. You have to sell a tangible benefit.

 

Considering the astronomical cost and materials for sufficient beanstalks to build colonies in a timely fashion, and that doesn't deal with the space-born infrastructure you will need for such an endeavor (more astronomical costs), let alone colony construction itself (even more astronomical costs) I don't think you will be able to convince anyone to just go for all three steps without justifying the profit margin on each step of the project.

 

You're going to have to make each step economically worthwhile. If you say do this now and 2-3 steps down the road (after your lifetime) there will be benefits IT WILL NEVER HAPPEN. Our global culture simply isn't that evolved. Now, I can think of ways to make each step economically attractive while building towards the greater goal, but sitting around saying "making the beanstalk economical isn't the point..." will kill the project dead faster than any technological hurdles will.

 

It has to be economical. Else, no one will build it.

 

There's actually a good STRATEGIC reason to build beanstalks (assuming they are technically feasible) Space is the ultimate high ground, and the first country to build beanstalks will essentially own LEO.

 

The first thing I do with a beanstalk is build more beanstalks, I sell access to space to all people with an economic intrest at pennies on the dollar (except that I don't use my beanstalk to let you build your beanstalk). I quickly establish a monopoly on space exploitation.

 

In the meanwhile my military has basiclly unfettered access to LEO. Maybe they don't send up troops, but they surely have access to every sattelite in orbit. Lust for example, let's go fetch a few enemy spy satellites and re tool them to work for us.