Your original wording was "The Titan II first stage has a sufficient mass ratio to be a SSTO. SSTO is 60s technology, and already flown hardware!"
Now you say: "The real problem is that the engine would need to be throttled down, and the Titan engine was not throttlable."
So it's "already flown hardware," except for the trivial detail that nobody has in fact built and flown it for the function you're claiming. I'll stop being "snide" when you stop playing word games.
Re:Whatever happened to single-stage-to-orbit?
on
NASA's Shuttle Plans
·
· Score: 1
You've still got a long way to go before you can beat Soyuz on both reliability and price, though. The Russians have pretty much nailed that one.
I agree, but the underlying reasons remain obscure, at least to me. I know the large total Proton production (with not-too-ambitious upgrades) has something to do with it, as does the corollary: a large base of flight experience providing more statistical confidence that subsystem X is 96.2% reliable, subsystem Y is 99.44% reliable, etc.
What I'd like to know more about is the economic background. Soviet cost accounting was opaque, and the subsequent semi-privatization of Russian and Ukrainian space capability -- well, opaque would be the kindest description.
So when I hear $20 million for a Soyuz mission, I don't know who paid how much, when, for the Proton manufacturing lines, launch/range/tracking infrastructure, etc. I don't know if or how they are reflected in that "marginal" figure. And I do know those are very significant when properly figured into our costs.
Jim Oberg is great on Soviet and Russian programs, but doesn't often go into costs, let alone how to do meaningful comparisons (e.g. using PPP for labor costs). Anyone got some good references on this topic?
Re:Whatever happened to single-stage-to-orbit?
on
NASA's Shuttle Plans
·
· Score: 1
"Maybe we could get back to actually exploring space instead of endless orbits then."
For 80 years before Skylab and Mir, 100 years before the ISS, people who thought about space figured we'd need an orbital station for three primary reasons:
(1) as a place to learn about actually living and working in free fall for extended periods (2) as an observatory (looking down as well as up), laboratory, comm relay, etc, (3) as a staging area to travel farther
For #1, the ISS actually ain't all that bad. You could say a Bigelow-style design would have saved a lot of money -- but don't forget that Bigelow's team has benefited greatly from data accumulated by the ISS.
#2 has faded because we've become much better than Tsiolkovsky, Oberth, or Clarke 1945 expected at building more or less autonomous scientific instruments as satellites and probes.
#3... well, that's the only thing some people care about, isn't it? "Mom! Dad! I'm tired of my Christmas bike... can I have a motorcycle now?"
"The other issues are building a single vehicle big enough to hold all that fuel needed to get to orbit and still have enough to get back down again, and carry a cargo big enough to be worth it."
Those are important only if your goal is something arcane like, say, improving access to space.
For many in this thread, the goal is (1) NASA bashing and (2) celebrating the cult of What Might Have Been, of the Road Not Taken, and of My Powerpoint Works Better Than Your Hardware.
We now return to our regularly scheduled broadcast of "How I Would Have Avoided All the Obvious Mistakes the Dumb STS Designers Made." (copyright 1981-2005, Hindsight Media Inc.)
"The Titan II first stage has a sufficient mass ratio to be a SSTO."
Gee, then let's just replace the second stage with a satellite or crew capsule and... Oh. Say what? You mean it has a sufficient mass ratio to be a SSTO with zero payload. Kewl.
"Did you know that the Space Shuttle has the worst GLOW:payload ratio in the business? It is 75:1!"
It would be ~15:1 except that we'd like to have the orbiter back. You're playing word games, which apparently impress you more than they impress the rocket equation.
Hence, use biocatalysis to perform the hydrolysis by extracting out the enzymes from the organism. Of course, that technology is a few years off, still.
A few tens of kg of nitrogenase (the enzyme in nitrogen-fixing bacteria and algae) have effects of the same order of magnitude as all the energy-intensive Haber-Bosch fertilizer facilities around the world. So people have been thinking for decades about turning that into a nice industrial process. Imagine blowing air across a membrane loaded with enzyme and watching the ammonia or nitrate solution come pouring off. Fame and wealth ensue.
Trouble is, even if we could synthesize the enzyme (not there yet), it seems to need the physical and metabolic context of those organisms to achieve its high catalytic effect. Similar considerations apply to all attempts at artificial photosynthesis so far.
Nature may be kinder with hydrogenase... but don't count on it.
> My laptop is more powerful than a 1975 supercomputer that filled a room, but a D cell battery hasn't changed its size in 30 years... Is everything shooting along while power generation creeps?
No, information technology is "shooting along" because it manipulates patterns of information -- which can always be instantiated in smaller and less energetic ways. By contrast, any technology whose purpose involves manipulating macroscopic quantities of mass and/or energy (i.e., almost everything *but* IT) necessarily lags behind.
As Ralph Gomory of IBM put it many years ago, "Take the steel and other materials of a 2000-lb car and make 2000 1-lb scale models, and they're useless as passenger vehicles. Do the same with the materials of a 2000-lb computer, and you have 2000 better computers." If you understand that, you'll understand why the persistent refrain of "why hasn't technology X, Y or Z advanced as fast as IT?" is... well... stupid.
> So we're coming to the day when cheap intercontinental ballistic missiles will be available to all.
This point will take a few years to gain traction, but sooner or later we'll all have to think about it more seriously than a/. snarkfest.
The central article of alt.space faith is that the cost of space access will be lowered by high flight rates, mass production of spacecraft, use of ordinary airports rather than specialized launch sites, and other economies of scale. The promise is basically "it'll grow profitably, just like commercial aviation, if there's not too much damn regulation by Big Bad Gummint."
Well... after decades of sporadic concern, terrorism and "rogue states" finally have us seriously focused -- maybe too late, maybe not -- on proliferation of nuclear weapon technology and fissile materials.
Picture a global future in which there are fleets of privately owned and operated suborbital (and eventually orbital) vehicles, all by definition capable of getting anywhere on earth really quickly. Great for access to space, but let's at least acknowledge that there's a potential downside: even without nasty neutron-rich packages on board, they could arrive with quite a bit of kinetic energy and fuel. Rumor has it that's even possible with 767s.
I'm not saying don't do it. I'm not saying it can't possibly be done safely. But those who don't see any potential for a rocketry counterpart of A. Q. Khan's Atomic Bazaar have more faith in human nature than I.
> seems that it would be more fuel efficient to launch vertically and glide in for the landing.
Again, as with a parachute: you have to compare the fuel cost of powered vertical descent to the fuel cost of lifting the wings, stronger airframe, and landing gear.
It's a damn shame, but there's really no alternative to doing the math.
In _The Rocket and the Reich_, historian Michael Neufeld pointed out that Germany spent about the same fraction of its wartime GDP on rocketry (including V-1, Wasserfall AA, etc) as the US did on the Manhattan Project.
Even if they had avoided scientific, technological and organizational dead ends, it's almost impossible to imagine they could have come up with additional resources for a German Hanford, Oak Ridge and Los Alamos.
> Why not just have your tether be a loop with a pully on the satellite? Then you just clamp a payload on and turn a crank on the ground.
Uhh... because that would demand a material about 80% stronger for the same weight, and the simple tether already demands 12-20 times the strength of the strongest existing bulk material?
You can find a lot of discussion of pulley systems and other variants on the Liftport forums. Whether it's worth discussing depends on whether you have a lot of faith in CNT development or a WHOLE lot of faith...
The Nike Zeus (1959) had a range of 320 km, the Spartan (1968) 740 km. As for the chance that either could get its 5-MT warhead close enough to harm a 16-foot lump of rock or nickel-iron rather than a much more delicate RV...
...doesn't the space elevator actually 'steal' momentum from the Earth's rotation when bringing mass into the space, which accounts for the huge "energy savings" when using the space elevator vs. a regular rocket?
The SE advantage is almost entirely from avoiding the rocket equation -- i.e., from not using propellant to make thrust to accelerate the propellant you'll be using later to make thrust to... etc. In other words, it's from avoiding rockets that are 20-50 times as massive on the pad as their payloads.
You do get free transverse ('rotational') velocity as you climb the ribbon to GEO, but it's not a big deal in energy terms. A rocket runs so hot that it's thermodynamically very efficient -- much more so than the conversion chain of electricity-laser-photovoltaics-electric motor for the Edwards SE -- but that is swamped by the rocket equation.
Don't worry about stealing the earth's spin. Tidal sloshing subtracts much, much more than SEs ever will.
I fail to see how climbing a 290 foot ribbon, on battery power, is even relevant to building a space elevator. It's realy just someone's fun little robotics engineering project... the lifter is a simple engineering project that could be built today.
Some might suggest that designing and building a model lifter to climb 290 feet is part of how you get ready to design and build a full-size lifter to climb 23,000 miles.
Some might suggest that the latter, while easier than rockets, is far from "simple" (it requires some mechanical components to be more durable and reliable than any ever made) and that the Liftport people know that better than you seem to.
Some might even be unkind enough to suggest that they're building things, and you're typing.
Small correction, Clark said that it would be 50 years after everyone stopped laughing, not 10.
Further correction: Clarke noted that he was borrowing the words from what physicist Arthur Kantrowitz had previously said about his (AK's) laser-launch ideas.
Space junk and low orbit satellites circle the Earth about every 90 minutes at 16,000mph. Thousands of pieces of junk and hundreds of satellites at various distances from the Earth would make it next to impossible to continually move a space elevator out of the way.
It's so much easier to say "next to impossible" than to do nasty old math, isn't it?
If you can make 23,000 miles of ribbon, it makes more sense to just keep doing that (and get the benefits of an escape-velocity "sling" from the outer portion) than to put a big dumb counterweight just beyond GEO. The latter idea is a vestige from the old scenarios of massive cables, when people thought they'd need to bring in an asteroid for raw materials to make the cable.
In the Edwards scenario, the "spider" climbers that reinforce an initial weak ribbon are simply run on out and parked at the far end; they add up to the small counterweight needed at ~60,000 miles.
Konstantin Tsiolkovsky is acknowledged as the creator of the space elevator concept, in 1895. He even had the concept of a station at geosynchronous orbit on the cable, so Sir Clark can't get credit for coming up with either of those concepts. Sir Clark did come up with the idea of putting a radio satellite in geosynchronous orbit though and it is for this idea that the orbit is called the Clark orbit.
Tsiolkovsky spoke of a tower, not a cable -- it was Artsutanov 1960 who first published on a tension structure, which makes all the difference in plausibility.
As Clarke himself notes, Noordung envisioned a space station with radio in GEO in the 1920s. What Clarke did in 1945 was to point out explicitly that GEO offers line of sight to almost a hemisphere, and therefore makes a great relay.
> At 100 km/hour (they are talking about a friction based drive mechanism), it would take 330 hours to get into orbit. And that limits your total throughput too much!
Um, you might want to compare the total mass lifted to orbit by rockets last year with the total annual throughput of Edwards' baseline 20-ton model.
There is a limited throughput problem. But it isn't the elevator's...
"Though these programs were not complete successes..."
Yeah, I guess that describes programs that never put a Delta Clipper or Venture Star in LEO at any cost, let alone a reasonable cost. I have nothing against them or a dozen other prototypes -- but if a program was aimed at orbiting hardware, and nothing orbited, there's a shorter name than "not a complete success."
Rutan has a leg up, yes. Don't mistake that for seven-league boots.
> The last 5-10% of the cable slaps the earth in a couple of the final frames. So what are the energy dynamics?
Just work the magnitudes of your own words: "the last 5-10% of the cable" is roughly 40 to 80 tons, stretched over roughly 5000 to 10000 kilometers. Were there big weather effects when the ~45-ton Skylab or the ~120-ton Columbia burned and disintegrated within a much smaller zone of the atmosphere? A falling SE cable would be moving faster, but not *that* much faster.
I agree that the "fratricide" issue (also discussed at Blaise Gassend's MIT pages) needs more analysis, and that much more massive SE cables *would* make a worst-case catastrophic failure a real concern. There'll be a trade-off somewhere between "more" and "bigger."
> If too much energy is released too quickly in too small a space you will have some serious conseqeunces.
True-- but what does that have to do with broken space elevators? There is NO physically reasonable scenario in which all or most of the ribbon encounters the atmosphere EITHER in a small space OR in a short time. No matter how you model it, the encounter is stretched over tens of thousands of miles and at least a few hours, more likely several days. So with all due respect, I find your joules to kilotons conversion meaningless -- because the latter is a unit exclusively used for very sudden, very local processes.
I'm in the middle of a multi-MEGATON event right now -- but since it's otherwise known as a sunny September day in southeast Pennsylvania, I'm staying pretty calm about it.
I agree that there's plenty of "real science and engineering" to be done yet. But I'd be a lot more worried about, say, a 20-ton climber+payload that somehow falls off the ribbon at a worst-case altitude than about the ribbon itself.
Slashdot Mirror
Your original wording was "The Titan II first stage has a sufficient mass ratio to be a SSTO. SSTO is 60s technology, and already flown hardware!"
Now you say: "The real problem is that the engine would need to be throttled down, and the Titan engine was not throttlable."
So it's "already flown hardware," except for the trivial detail that nobody has in fact built and flown it for the function you're claiming. I'll stop being "snide" when you stop playing word games.
You've still got a long way to go before you can beat Soyuz on both reliability and price, though. The Russians have pretty much nailed that one.
I agree, but the underlying reasons remain obscure, at least to me. I know the large total Proton production (with not-too-ambitious upgrades) has something to do with it, as does the corollary: a large base of flight experience providing more statistical confidence that subsystem X is 96.2% reliable, subsystem Y is 99.44% reliable, etc.
What I'd like to know more about is the economic background. Soviet cost accounting was opaque, and the subsequent semi-privatization of Russian and Ukrainian space capability -- well, opaque would be the kindest description.
So when I hear $20 million for a Soyuz mission, I don't know who paid how much, when, for the Proton manufacturing lines, launch/range/tracking infrastructure, etc. I don't know if or how they are reflected in that "marginal" figure. And I do know those are very significant when properly figured into our costs.
Jim Oberg is great on Soviet and Russian programs, but doesn't often go into costs, let alone how to do meaningful comparisons (e.g. using PPP for labor costs). Anyone got some good references on this topic?
"Maybe we could get back to actually exploring space instead of endless orbits then."
For 80 years before Skylab and Mir, 100 years before the ISS, people who thought about space figured we'd need an orbital station for three primary reasons:
(1) as a place to learn about actually living and working in free fall for extended periods
(2) as an observatory (looking down as well as up), laboratory, comm relay, etc,
(3) as a staging area to travel farther
For #1, the ISS actually ain't all that bad. You could say a Bigelow-style design would have saved a lot of money -- but don't forget that Bigelow's team has benefited greatly from data accumulated by the ISS.
#2 has faded because we've become much better than Tsiolkovsky, Oberth, or Clarke 1945 expected at building more or less autonomous scientific instruments as satellites and probes.
#3... well, that's the only thing some people care about, isn't it? "Mom! Dad! I'm tired of my Christmas bike... can I have a motorcycle now?"
"The other issues are building a single vehicle big enough to hold all that fuel needed to get to orbit and still have enough to get back down again, and carry a cargo big enough to be worth it."
Those are important only if your goal is something arcane like, say, improving access to space.
For many in this thread, the goal is (1) NASA bashing and (2) celebrating the cult of What Might Have Been, of the Road Not Taken, and of My Powerpoint Works Better Than Your Hardware.
We now return to our regularly scheduled broadcast of "How I Would Have Avoided All the Obvious Mistakes the Dumb STS Designers Made." (copyright 1981-2005, Hindsight Media Inc.)
"The Titan II first stage has a sufficient mass ratio to be a SSTO."
Gee, then let's just replace the second stage with a satellite or crew capsule and... Oh. Say what? You mean it has a sufficient mass ratio to be a SSTO with zero payload. Kewl.
"Did you know that the Space Shuttle has the worst GLOW:payload ratio in the business? It is 75:1!"
It would be ~15:1 except that we'd like to have the orbiter back. You're playing word games, which apparently impress you more than they impress the rocket equation.
A few tens of kg of nitrogenase (the enzyme in nitrogen-fixing bacteria and algae) have effects of the same order of magnitude as all the energy-intensive Haber-Bosch fertilizer facilities around the world. So people have been thinking for decades about turning that into a nice industrial process. Imagine blowing air across a membrane loaded with enzyme and watching the ammonia or nitrate solution come pouring off. Fame and wealth ensue.
Trouble is, even if we could synthesize the enzyme (not there yet), it seems to need the physical and metabolic context of those organisms to achieve its high catalytic effect. Similar considerations apply to all attempts at artificial photosynthesis so far.
Nature may be kinder with hydrogenase... but don't count on it.
> My laptop is more powerful than a 1975 supercomputer that filled a room, but a D cell battery hasn't changed its size in 30 years... Is everything shooting along while power generation creeps?
No, information technology is "shooting along" because it manipulates patterns of information -- which can always be instantiated in smaller and less energetic ways. By contrast, any technology whose purpose involves manipulating macroscopic quantities of mass and/or energy (i.e., almost everything *but* IT) necessarily lags behind.
As Ralph Gomory of IBM put it many years ago, "Take the steel and other materials of a 2000-lb car and make 2000 1-lb scale models, and they're useless as passenger vehicles. Do the same with the materials of a 2000-lb computer, and you have 2000 better computers." If you understand that, you'll understand why the persistent refrain of "why hasn't technology X, Y or Z advanced as fast as IT?" is... well... stupid.
> So we're coming to the day when cheap intercontinental ballistic missiles will be available to all.
/. snarkfest.
This point will take a few years to gain traction, but sooner or later we'll all have to think about it more seriously than a
The central article of alt.space faith is that the cost of space access will be lowered by high flight rates, mass production of spacecraft, use of ordinary airports rather than specialized launch sites, and other economies of scale. The promise is basically "it'll grow profitably, just like commercial aviation, if there's not too much damn regulation by Big Bad Gummint."
Well... after decades of sporadic concern, terrorism and "rogue states" finally have us seriously focused -- maybe too late, maybe not -- on proliferation of nuclear weapon technology and fissile materials.
Picture a global future in which there are fleets of privately owned and operated suborbital (and eventually orbital) vehicles, all by definition capable of getting anywhere on earth really quickly. Great for access to space, but let's at least acknowledge that there's a potential downside: even without nasty neutron-rich packages on board, they could arrive with quite a bit of kinetic energy and fuel. Rumor has it that's even possible with 767s.
I'm not saying don't do it. I'm not saying it can't possibly be done safely. But those who don't see any potential for a rocketry counterpart of A. Q. Khan's Atomic Bazaar have more faith in human nature than I.
> seems that it would be more fuel efficient to launch vertically and glide in for the landing.
Again, as with a parachute: you have to compare the fuel cost of powered vertical descent to the fuel cost of lifting the wings, stronger airframe, and landing gear.
It's a damn shame, but there's really no alternative to doing the math.
In _The Rocket and the Reich_, historian Michael Neufeld pointed out that Germany spent about the same fraction of its wartime GDP on rocketry (including V-1, Wasserfall AA, etc) as the US did on the Manhattan Project.
Even if they had avoided scientific, technological and organizational dead ends, it's almost impossible to imagine they could have come up with additional resources for a German Hanford, Oak Ridge and Los Alamos.
> Why not just have your tether be a loop with a pully on the satellite? Then you just clamp a payload on and turn a crank on the ground.
Uhh... because that would demand a material about 80% stronger for the same weight, and the simple tether already demands 12-20 times the strength of the strongest existing bulk material?
You can find a lot of discussion of pulley systems and other variants on the Liftport forums. Whether it's worth discussing depends on whether you have a lot of faith in CNT development or a WHOLE lot of faith...
> If it is a space elevator , then why dont they transfer the power through the tether
Soon as you tell 'em how to get any useful amount through tens of thousands of miles of it, I'm sure they will.
CNTs are very good conductors. They are not superconductors. There *is* a difference.
The Nike Zeus (1959) had a range of 320 km, the Spartan (1968) 740 km. As for the chance that either could get its 5-MT warhead close enough to harm a 16-foot lump of rock or nickel-iron rather than a much more delicate RV...
Let us pray.
...doesn't the space elevator actually 'steal' momentum from the Earth's rotation when bringing mass into the space, which accounts for the huge "energy savings" when using the space elevator vs. a regular rocket?
... etc. In other words, it's from avoiding rockets that are 20-50 times as massive on the pad as their payloads.
The SE advantage is almost entirely from avoiding the rocket equation -- i.e., from not using propellant to make thrust to accelerate the propellant you'll be using later to make thrust to
You do get free transverse ('rotational') velocity as you climb the ribbon to GEO, but it's not a big deal in energy terms. A rocket runs so hot that it's thermodynamically very efficient -- much more so than the conversion chain of electricity-laser-photovoltaics-electric motor for the Edwards SE -- but that is swamped by the rocket equation.
Don't worry about stealing the earth's spin. Tidal sloshing subtracts much, much more than SEs ever will.
I fail to see how climbing a 290 foot ribbon, on battery power, is even relevant to building a space elevator. It's realy just someone's fun little robotics engineering project... the lifter is a simple engineering project that could be built today.
Some might suggest that designing and building a model lifter to climb 290 feet is part of how you get ready to design and build a full-size lifter to climb 23,000 miles.
Some might suggest that the latter, while easier than rockets, is far from "simple" (it requires some mechanical components to be more durable and reliable than any ever made) and that the Liftport people know that better than you seem to.
Some might even be unkind enough to suggest that they're building things, and you're typing.
Small correction, Clark said that it would be 50 years after everyone stopped laughing, not 10.
Further correction: Clarke noted that he was borrowing the words from what physicist Arthur Kantrowitz had previously said about his (AK's) laser-launch ideas.
You're borrowing momentum from the ribbon/counterweight to accelerate the cars up to orbital velocity
No, you're borrowing momentum from the ribbon, counterweight, and six sextillion tons of rotating planet.
Space junk and low orbit satellites circle the Earth about every 90 minutes at 16,000mph. Thousands of pieces of junk and hundreds of satellites at various distances from the Earth would make it next to impossible to continually move a space elevator out of the way.
It's so much easier to say "next to impossible" than to do nasty old math, isn't it?
If you can make 23,000 miles of ribbon, it makes more sense to just keep doing that (and get the benefits of an escape-velocity "sling" from the outer portion) than to put a big dumb counterweight just beyond GEO. The latter idea is a vestige from the old scenarios of massive cables, when people thought they'd need to bring in an asteroid for raw materials to make the cable.
In the Edwards scenario, the "spider" climbers that reinforce an initial weak ribbon are simply run on out and parked at the far end; they add up to the small counterweight needed at ~60,000 miles.
Konstantin Tsiolkovsky is acknowledged as the creator of the space elevator concept, in 1895. He even had the concept of a station at geosynchronous orbit on the cable, so Sir Clark can't get credit for coming up with either of those concepts. Sir Clark did come up with the idea of putting a radio satellite in geosynchronous orbit though and it is for this idea that the orbit is called the Clark orbit.
Tsiolkovsky spoke of a tower, not a cable -- it was Artsutanov 1960 who first published on a tension structure, which makes all the difference in plausibility.
As Clarke himself notes, Noordung envisioned a space station with radio in GEO in the 1920s. What Clarke did in 1945 was to point out explicitly that GEO offers line of sight to almost a hemisphere, and therefore makes a great relay.
> At 100 km/hour (they are talking about a friction based drive mechanism), it would take 330 hours to get into orbit. And that limits your total throughput too much!
Um, you might want to compare the total mass lifted to orbit by rockets last year with the total annual throughput of Edwards' baseline 20-ton model.
There is a limited throughput problem. But it isn't the elevator's...
Kazrath> Small efficent shuttle from surface - orbit.
Be careful it doesn't run into the rocket equation. Hurts worse than the Van Allen belts, they say.
Boy oh boy, SSTO is just so freakin' great, I'm afraid somebody might actually build one and fly it, and it would be a letdown.
That no one has done so in 47 years is a small comfort, but I still worry.
"Though these programs were not complete successes..."
Yeah, I guess that describes programs that never put a Delta Clipper or Venture Star in LEO at any cost, let alone a reasonable cost. I have nothing against them or a dozen other prototypes -- but if a program was aimed at orbiting hardware, and nothing orbited, there's a shorter name than "not a complete success."
Rutan has a leg up, yes. Don't mistake that for seven-league boots.
> The last 5-10% of the cable slaps the earth in a couple of the final frames. So what are the energy dynamics?
Just work the magnitudes of your own words: "the last 5-10% of the cable" is roughly 40 to 80 tons, stretched over roughly 5000 to 10000 kilometers. Were there big weather effects when the ~45-ton Skylab or the ~120-ton Columbia burned and disintegrated within a much smaller zone of the atmosphere? A falling SE cable would be moving faster, but not *that* much faster.
I agree that the "fratricide" issue (also discussed at Blaise Gassend's MIT pages) needs more analysis, and that much more massive SE cables *would* make a worst-case catastrophic failure a real concern. There'll be a trade-off somewhere between "more" and "bigger."
-Monte
> If too much energy is released too quickly in too small a space you will have some serious conseqeunces.
True-- but what does that have to do with broken space elevators? There is NO physically reasonable scenario in which all or most of the ribbon encounters the atmosphere EITHER in a small space OR in a short time. No matter how you model it, the encounter is stretched over tens of thousands of miles and at least a few hours, more likely several days. So with all due respect, I find your joules to kilotons conversion meaningless -- because the latter is a unit exclusively used for very sudden, very local processes.
I'm in the middle of a multi-MEGATON event right now -- but since it's otherwise known as a sunny September day in southeast Pennsylvania, I'm staying pretty calm about it.
I agree that there's plenty of "real science and engineering" to be done yet. But I'd be a lot more worried about, say, a 20-ton climber+payload that somehow falls off the ribbon at a worst-case altitude than about the ribbon itself.