and that if we threw enough money at the problem (which we won't), it would be solved.
No. "Feasible" doesn't mean it's just a matter of throwing money at it. A lunar elevator could still turn out to be impossible with existing materials/technology, even with an unlimited budget. (As I said, I think the repair systems alone are beyond the state-of-the-art in robotics. Not just that the specific equipment doesn't exist at Walmart, I mean it's beyond the available or reasonably projected level of AI. That's without allowing for them operating in space, in full chip-killing radiation...) It might be possible with an unlimited budget and unlimited time to allow science to advance enough to catch up.
There's a bunch of stuff required for the lunar elevator which might be possible given enough money, but there's also likely to be a whole bunch which, in spite of being theoretically "feasible", are probably in reality beyond our current scientific ability to create even with if you threw the entire US GDP at them.
For a more limited example of "feasible but...", the Orion capsule is "feasible... but" it's now likely to be so heavy that it may exceed the ability of the Navy to recover it onto an aircraft carrier after it splashes down. That doesn't mean you can't design a dedicated recovery ship for it, or more likely adapt another ship such as a amphibious or semi-submersible ship. But that wasn't the intention, so Orion was clearly "unfeasible" as originally conceived: You can't make the capsule they proposed, at the mass they wanted, with the technology available.
Likewise, the SLS is "low-risk" according to NASA definitions... but if it aborts too early during launch, the expanding cloud of solid-fuel particles from the SRBs would still be burning if the capsule descends back through that region, setting fire to the abort-parachutes and causing the crew to fall to their deaths. (See the random path of the shuttle SRBs before they were detonated, during the Challenger explosion. There's no way to eliminate the chance of the SRB's detonating under the descent path of the capsule.)
Missed? No, they are right there in the report. Ie, technologies that we do not have, which would individually be a major NASA program, and which are the minimum requirement for a space elevator of any type. (The robotic repair systems alone are probably beyond the current state of the art of robotics, IMO. But the ground station, the "tramway" tower construction (let alone ISRU fabrication), the L1 ribbon deployment system, the actual elevator "cars", even the single use "tramway" cable tow-vehicle, etc etc etc. Possibly within current technological limits, but each hideously expensive to develop.)
A single 1km lunar tower construction would be the largest (and most expensive) project NASA has even done, even if the parts were already sitting in crates on the lunar surface. Pearson needs over 50 of them (more if they are smaller). And they are a small side-part of his proposal.
Likewise, a lunar facility which could produce tower-parts from lunar materials would be the most technologically advanced research project NASA has attempted in decades, even without the actual construction of towers. Much more demanding than anything going on at the $3b/yr ISS, or any of the $3b/yr SLS development, or the $9b JWST. And that's just something capable of taking regolith and outputting a small number of tower components; not something capable of actually producing a full 1km tower's-worth, let alone 50+. Just being able to produce the required types of parts at all. And ignoring that it has to be mobile and capable to tracking from the equator to the poles. (Or have a fleet of delivery vehicles capable of relaying parts to and from the construction sites. Each of which would be the largest and most advanced vehicles ever produced by NASA. Making the Mars Curiosity rover look like a toy.)
There's probably a thousand other technologies of similar difficulty and expense that I'm missing, too. These few just jumped out at me. Components which would individually be multi-decade multi-$billion/yr Agency-wide flagship programs. The 180,000km ribbon itself is beyond me to even speculate over the difficulty or cost, plus the ribbon's deployment system...
It's the difference in the definition of "Feasible". A lot of impossible/difficult/expensive proposals are deemed "feasible" by NASA standards. "No show-stoppers" as they say. Venture Star was "feasible", NASP was "feasible", Freedom Space Station was "feasible". Hell, SLS is considered not just "feasible" but "low-risk". Similar reports in the seventies of giant space-stations (Stanford Torus, Bernal sphere, or O'Neill cylinders) were considered "technologically feasible". And they likewise required impossibly huge projects as small sub-sets of their development (such as mining, processing, and giant mass drivers on the moon just to supply the raw materials for their construction.)
Pearson's elevator, while simpler than an O'Neill cylinder, would nonetheless make the Apollo program look like NASA's Christmas video.
[Aside: My throw-away comment in last post "or the sort of autonomous in-situ manufacturing that would have already replaced the entire manufacturing industry on Earth" is unclear. I meant if you had the technology to automate the construction of 1km lunar towers from nothing but lunar regolith and solar power, the same technology would have already revolutionised and replaced the majority of manufacturing and especially construction if used here on Earth. Imagine being able to construct, say, concrete and steel buildings or bridges by feeding iron ore, limestone, coke, water, etc, into an automated (solar powered) construction system.
Further aside: BTW, we should be developing lunar and asteroidal ISRU technologies. But proposing a giant space project which treats this radical and revolutionary technological advance as if it's already proven and mature... Hence, "you have to have an industry in place in space so large that you must have already solved the problem you are trying to solve with a space elevator."]
Keep reading until you get to the list of operational requirements.
As I said, you have to have an industry in place in space so large that you must have already solved the problem you are trying to solve with a space elevator (or the sort of autonomous in-situ manufacturing that would have already replaced the entire manufacturing industry on Earth if it was possible with current technology).
[Space elevators are a bit like He3 mining. While the claims might technically be right, by the time we are capable of performing the task, the assumptions underlying the entire equation would have changed. Therefore, outside of nerdy what-if thought-experiments, there's really no point "planning" them today, nor using them to justify any kind of advocacy.]
Minimal length for a lunar elevator is about 80,000km, assuming a large counterweight. Longer if you are only using the deployment-system itself as the sole counterweight. Your gravitational "mid-point" is L1, about 60,000km from the moon. So you have to have a sufficient balancing mass (ribbon+counterweight) beyond 60,000km. A "true" elevator (ribbon only, no counterweight) is over 200,000km, or more than half way from the moon back to Earth.
The industry required to built that suggests you already have low cost access to space, and enough lunar surface activity to justify it. Which means you must have already solved the problem the lunar elevator is intended to solve. A space elevator doesn't get you "there", you already have to be "there" to justify (or afford) a space elevator; and if you are already "there", why do you need a space elevator?
Actually, that's an excuse. The actual concern is solved by having a big red switch saying "Auto/Manual" which physically connects/disconnects the data-line between the avionics computer and the flight-deck. OTOH, making it physically impossible to fly the shuttle remotely was a management decision to reinforce the fiction of the necessity of manned space flight.
But do you think that they said to themselves, "Well this might kill people, but that's a risk I'm willing to take?"
No, it wasn't "a risk I'm willing to take", it was the "risk I'm personally not willing to take" which allowed the greater risk. Actively avoiding information to ensure they don't have to make the big expensive risky decision. (Whether to attempt a hugely risky rescue, or to leave them to die, both are no-win situations for the managers. That makes "we didn't know" and "there's nothing we can do", the least risky personal scenario. And so that's what they chose. Over and over and over.)
For example, according to NASA people who were there at the time (like the flight director), management didn't just refuse to ask DoD for help imaging the orbiter, they actively blocked attempts by others to ask for help. There was only a 50/50 chance the images would be useful, but there was no risk to anyone if they weren't. So why block it? Not just "I don't think it's worth it", but actively preventing others from requesting it.
On orbit repair sounds great, except that building all the hardware is more expensive than just letting the shuttle burn up and riding back down on a soyuz.
Rubbish. They put it into production after Columbia. And flew the repair kits on nearly every flight afterwards. Repair (and rescue) scenarios were considered from the beginning of the shuttle program. And they were constantly blocked or undermined by senior management. The loss of Columbia was a culmination of that attitude.
Certain functions physically couldn't be activated remotely. Starting the APUs to power up the hydraulics, deploying the air-speed pitot tube, lowering the landing gear, and popping the drag 'chutes after touchdown. The orbiters had normal on-board auto-pilots, but these also couldn't be activated or controlled from the ground.
The last few missions (post-Columbia) had a 28 foot long cable to physically connect the flight controls to the avionics computer in the mid-deck, to allow remote reentry control, if the crew had to be brought home on a rescue shuttle. http://en.wikipedia.org/wiki/STS-3xx#Remote_Control_Orbiter. It's only wiki, but it was the easiest to dig up.
Re: Autopilot landings. It was never used during landing. During the third mission, the autopilot controlled the descent to 200ft, then the pilot took over. He found it awkward and landed hard, and the review committee (made up of astronaut-pilots) concluded that a pilot would have difficulty taking over during an emergency, because they wouldn't have time to get a "feel" for the flight. So after that no mission ever attempted to landed on auto-pilot. (It was still used during reentry, but as soon as the orbiter had enough atmosphere to use its flight-controls, the pilot took over.) There was a group who still wanted to use the autopilot, but the whole idea was officially killed around 1984.
The shuttles weren't able to land unmanned, due to quite deliberate decisions made during their development, against engineer requests, which shows just how long the current management style has been operating.
Actually, first you would have to ask the Columbia crew if they wanted to take the risk of doing an (untrained) EVA to go out and assess the actual damage, or take the risk of landing without knowing.
According to NASA people there at the time, there was a very deliberate campaign by senior management to block attempts to assess damage, or get help from outside the agency (they refused DoD's offer to image the shuttle), or prepare for the worst. They had decided at the first meeting that "nothing could be done", and any attempt to tell them otherwise was shut down.
An example of that attitude is in the report itself, the only rescue scenario even looked at was rushing Atlantis into service. No analysis of sending up a Proton with supplies, or an empty Soyuz to retrieve three (maybe four) crew to reduce the demand on the LSS and extend the time available to stage the Atlantis rescue. [Ie, rushing the launch of an unmanned rocket to reduce the risk from rushing the manned rescue.]
Columbia could have been their finest hour. Instead it was a perfect example of how the agency is rotting away. And failing to call them on that, because we don't want to offend their delicate sensibilities, just begs for a continuation of the rot.
Do I need to remind you of Feynman's shredding of NASA's credibility in the Challenger investigation? Or the more recent report that showed using a solid stage on SLS would likely result in an unsurvivable abort scenario (due to burning solid fuel destroying the parachutes). Or the recent report that says Orion is too heavy for the Navy to recover...
How about the fact that on-orbit repair scenarios had been suggested and studied by engineering groups ever since the shuttle was built, but not one piece of hardware was even allowed to be built, let alone flown. Not even after Challenger.
The agency repeats the same mistakes over and over and over...
[And it's not just manned missions: http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure"The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed."]
(Every beancounter in the government will tell you, NO orbiter is expendable, if there's even a remote chance to bring back that multi-billion dollar device -- which is why they created the 28ft/5lb "RCO IFM" cable after Columbia... the crew can plug it in, bug out, and let Huston land the thing.)
Necessitated by the very deliberate decision, widely criticised at the time, to not design remote landing capability into the shuttle in order to enforce the "need" to use astronaut-pilots.
Weird. Every phone I've ever owned has a removable battery. Not one has ever done this, even when accidentally I drop them on the floor. How hard are you slamming them down?
The short version is that horizontal velocity of the surface of Earth at the equator is about 800 m/s. The horizontal velocity of GEO is 3000 m/s. The car has to gain that horizontal velocity as it climbs (and lose it as it falls), and it does so by stealing it from the cable, this causes that section of the cable to "lag" behind as it passes the loss to the ground (eventually stealing the energy from Earth's rotation). That creates the moving kink in the cable.
However, the industry itself only really exists because of that modularity. Small vendors being able to assemble niche systems from modular components, without having to do high-end electrical engineering and manufacturing.
Modular "phones" won't be modified by more than a fraction of the most nerdish end-users, but they will be a boon to other device makers. Companies are already using cellphone and tablet parts as cheap, standardised, easy-to-design-for control systems and/or displays for their products. Likewise, companies are making niche products that plug into a standard cellphone, rather than require their own computer/display/battery/etc.
With modularity, that ability increases exponentially.
The number of people talking about the issue of balancing the elevator makes me think perhaps I have misunderstood.
Different emphasis depending on what you are trying to explain. The system is almost in balance. The amount of tension at the ground is completely arbitrary. So when discussing payload movement, it's the "almost" that's important. When explaining how the concept works to someone (Chas) who thinks it's a billion-tonne "tower" pressing on the ground, it's the "balance" that's is emphasised to them.
Want to put a heavy load on the ribbon bottom? Send a signal to have the counterweight climb further up
That would work, but IMO if the ribbon is capable of handling the force from the climber+payload, then why not use a base-anchor heavy enough to handle the tension when there isn't a climber? Ie, leave the system in permanent tension.
For early versions (small ribbon, no GEO station), apparently they want to have winches on Earth feed out excess ribbon to increase tension, or pull it back to reduce it. The idea is to keep the tension on the ground-station roughly constant, and fairly light. This is because they assume the first version will be at the very edge of possible, and kept as small and light as possible in order to be able to build it at all. For example, the counterweight would be the rocket-stage and drum from the original deployment. You start in GEO and let out the ribbon, the drum naturally moves outwards to balance the descending arm. [Rather than the usual image of a central deployment at GEO feeding out two arms in balance.]
Re: wobbling versus retracting.
It would also take a long time to winch up and redeploy it each time, during which the the system is useless. Given the number of satellites (especially in LEO) and orbital debris that it would have to dodge out of the way of, it wouldn't spend enough time in operation to justify its existence. During a ship-driven "wobble", otoh, it can still be launching and retrieving climbers.
There's a torque force on the tether due to Coriolis. Because it causes a moving bend in the cable, it's a nastier effect than the simple linear forces on the cable. The faster the car travels, the more severe the force, the sharper the bend. (From an engineering standpoint, it's like a shockwave travelling up the cable. Go above the speed-of-sound-in-the-material, and it's a supersonic shockwave inside the tether. But even below the speed of sound, it's a nasty effect.)
Actually there are proposals that take the properties of modern super materials (carbon composites) and calculate the maximum height of a (compression) tower. And, depending on your assumptions, you can actually get above 100km. Even steel towers could theoretically get to 10-15km using modern designs.
There are also designs for rotating orbital tethers which have a tip-velocity equal to the Earth's surface velocity, dipping into the atmosphere to pick up airborne payloads. (Or tower-borne if you combined it with the 100km carbon-tower.) From an engineering and economic standpoint, these are much simpler than a full space elevator, since they require much less strength in the materials, and are built at much shorter lengths.
There are also proposals for neutral buoyancy towers which are... theoretically... possible. (Essentially a series of hydrogen-filled balloon toruses stacked on top of each other, creating a net lift sufficient to hold another tower on top, above the bulk of the atmosphere.)
Seriously, we're talking about a 22,000 mile cable
No. It's at least double that. A space elevator doesn't just go up to GEO, it's "balanced" at GEO, there's an entire outward arm. (And in reality it would be under tension, so the outer arm would be more massive than the inner, the balance point would be well below GEO.)
where a single fault could cause the whole thing to come crashing down.
No fault could cause the "whole thing to come crashing down". Only the portion below the break could fall. And since it's a known failure mode, you'd have built-in separation points at various lengths. When there's a failure, you release a piece of cable/ribbon at the top and/or bottom ends of sufficient mass to allow the centre section to go into a stable orbit. This allows recovery and repair.
Show me any application of continuous nanotube material beyond trivial length. Just one example. Not some guy pontificating in a podcast, but an actual example of use.
A space elevator requires tens of thousands of kilometres of cable or ribbon at close to the theoretical maximum strength of nanotubes.
From what I've seen, the longest true lengths outside a lab are millimetres. The longest lengths of usable "thread" are metres, but are made of a tangle of sub-millimetre nanotubes not a continuous length, and so are well below the theoretical minimum strength required for a space elevator, let alone the much greater practical engineering strength required for a real one.
No-one is making macro lengths of nanotubes. No-one is making macro lengths of any material at close to the strength required for space elevators.
You are contradicting yourself. If a single car is sufficient to pull a "balanced" tether out of orbit, then only a similarly small outward force is necessary to counter the force of a car, therefore even a small base-mass (such as a ship or barge) is sufficient to counter that outward force. Ie, if a one tonne car pulling down at 1.5g would pull the tether out of orbit, then you only need a few tonnes outward force (measured at the base) to prevent that. And thus only a few tonnes beyond that to sufficiently anchor the tether down.
Therefore you do not need to "drill really deep into bedrock to suitably anchor this beast".
(In reality, you'd want an outward force a full order of magnitude higher than the cargo capacity. And an anchor-mass another order of magnitude higher than that. So a 1 tonne payload, a ten tonne outward force, a 100 tonne base. Double or triple for reserve. Well within the capability of even a small ship or barge.)
A bigger problem is actually the sidewards torque due to Coriolis as the cars rise and fall. This creates not only additional pull on the cable/ribbon, but specifically bends or crimps the ribbon as the car passes. This will stress the material well beyond the simple linear forces.
Slashdot Mirror
and that if we threw enough money at the problem (which we won't), it would be solved.
No. "Feasible" doesn't mean it's just a matter of throwing money at it. A lunar elevator could still turn out to be impossible with existing materials/technology, even with an unlimited budget. (As I said, I think the repair systems alone are beyond the state-of-the-art in robotics. Not just that the specific equipment doesn't exist at Walmart, I mean it's beyond the available or reasonably projected level of AI. That's without allowing for them operating in space, in full chip-killing radiation...) It might be possible with an unlimited budget and unlimited time to allow science to advance enough to catch up.
There's a bunch of stuff required for the lunar elevator which might be possible given enough money, but there's also likely to be a whole bunch which, in spite of being theoretically "feasible", are probably in reality beyond our current scientific ability to create even with if you threw the entire US GDP at them.
For a more limited example of "feasible but...", the Orion capsule is "feasible... but" it's now likely to be so heavy that it may exceed the ability of the Navy to recover it onto an aircraft carrier after it splashes down. That doesn't mean you can't design a dedicated recovery ship for it, or more likely adapt another ship such as a amphibious or semi-submersible ship. But that wasn't the intention, so Orion was clearly "unfeasible" as originally conceived: You can't make the capsule they proposed, at the mass they wanted, with the technology available.
Likewise, the SLS is "low-risk" according to NASA definitions... but if it aborts too early during launch, the expanding cloud of solid-fuel particles from the SRBs would still be burning if the capsule descends back through that region, setting fire to the abort-parachutes and causing the crew to fall to their deaths. (See the random path of the shuttle SRBs before they were detonated, during the Challenger explosion. There's no way to eliminate the chance of the SRB's detonating under the descent path of the capsule.)
Missed? No, they are right there in the report. Ie, technologies that we do not have, which would individually be a major NASA program, and which are the minimum requirement for a space elevator of any type. (The robotic repair systems alone are probably beyond the current state of the art of robotics, IMO. But the ground station, the "tramway" tower construction (let alone ISRU fabrication), the L1 ribbon deployment system, the actual elevator "cars", even the single use "tramway" cable tow-vehicle, etc etc etc. Possibly within current technological limits, but each hideously expensive to develop.)
A single 1km lunar tower construction would be the largest (and most expensive) project NASA has even done, even if the parts were already sitting in crates on the lunar surface. Pearson needs over 50 of them (more if they are smaller). And they are a small side-part of his proposal.
Likewise, a lunar facility which could produce tower-parts from lunar materials would be the most technologically advanced research project NASA has attempted in decades, even without the actual construction of towers. Much more demanding than anything going on at the $3b/yr ISS, or any of the $3b/yr SLS development, or the $9b JWST. And that's just something capable of taking regolith and outputting a small number of tower components; not something capable of actually producing a full 1km tower's-worth, let alone 50+. Just being able to produce the required types of parts at all. And ignoring that it has to be mobile and capable to tracking from the equator to the poles. (Or have a fleet of delivery vehicles capable of relaying parts to and from the construction sites. Each of which would be the largest and most advanced vehicles ever produced by NASA. Making the Mars Curiosity rover look like a toy.)
There's probably a thousand other technologies of similar difficulty and expense that I'm missing, too. These few just jumped out at me. Components which would individually be multi-decade multi-$billion/yr Agency-wide flagship programs. The 180,000km ribbon itself is beyond me to even speculate over the difficulty or cost, plus the ribbon's deployment system...
It's the difference in the definition of "Feasible". A lot of impossible/difficult/expensive proposals are deemed "feasible" by NASA standards. "No show-stoppers" as they say. Venture Star was "feasible", NASP was "feasible", Freedom Space Station was "feasible". Hell, SLS is considered not just "feasible" but "low-risk". Similar reports in the seventies of giant space-stations (Stanford Torus, Bernal sphere, or O'Neill cylinders) were considered "technologically feasible". And they likewise required impossibly huge projects as small sub-sets of their development (such as mining, processing, and giant mass drivers on the moon just to supply the raw materials for their construction.)
Pearson's elevator, while simpler than an O'Neill cylinder, would nonetheless make the Apollo program look like NASA's Christmas video.
[Aside: My throw-away comment in last post "or the sort of autonomous in-situ manufacturing that would have already replaced the entire manufacturing industry on Earth" is unclear. I meant if you had the technology to automate the construction of 1km lunar towers from nothing but lunar regolith and solar power, the same technology would have already revolutionised and replaced the majority of manufacturing and especially construction if used here on Earth. Imagine being able to construct, say, concrete and steel buildings or bridges by feeding iron ore, limestone, coke, water, etc, into an automated (solar powered) construction system.
Further aside: BTW, we should be developing lunar and asteroidal ISRU technologies. But proposing a giant space project which treats this radical and revolutionary technological advance as if it's already proven and mature... Hence, "you have to have an industry in place in space so large that you must have already solved the problem you are trying to solve with a space elevator."]
Mr. Pearson's calculations
Keep reading until you get to the list of operational requirements.
As I said, you have to have an industry in place in space so large that you must have already solved the problem you are trying to solve with a space elevator (or the sort of autonomous in-situ manufacturing that would have already replaced the entire manufacturing industry on Earth if it was possible with current technology).
[Space elevators are a bit like He3 mining. While the claims might technically be right, by the time we are capable of performing the task, the assumptions underlying the entire equation would have changed. Therefore, outside of nerdy what-if thought-experiments, there's really no point "planning" them today, nor using them to justify any kind of advocacy.]
Minimal length for a lunar elevator is about 80,000km, assuming a large counterweight. Longer if you are only using the deployment-system itself as the sole counterweight. Your gravitational "mid-point" is L1, about 60,000km from the moon. So you have to have a sufficient balancing mass (ribbon+counterweight) beyond 60,000km. A "true" elevator (ribbon only, no counterweight) is over 200,000km, or more than half way from the moon back to Earth.
The industry required to built that suggests you already have low cost access to space, and enough lunar surface activity to justify it. Which means you must have already solved the problem the lunar elevator is intended to solve. A space elevator doesn't get you "there", you already have to be "there" to justify (or afford) a space elevator; and if you are already "there", why do you need a space elevator?
Actually, that's a safety mechanism
Actually, that's an excuse. The actual concern is solved by having a big red switch saying "Auto/Manual" which physically connects/disconnects the data-line between the avionics computer and the flight-deck. OTOH, making it physically impossible to fly the shuttle remotely was a management decision to reinforce the fiction of the necessity of manned space flight.
5lbs is a lot of dead weight
[Laughs]
But do you think that they said to themselves, "Well this might kill people, but that's a risk I'm willing to take?"
No, it wasn't "a risk I'm willing to take", it was the "risk I'm personally not willing to take" which allowed the greater risk. Actively avoiding information to ensure they don't have to make the big expensive risky decision. (Whether to attempt a hugely risky rescue, or to leave them to die, both are no-win situations for the managers. That makes "we didn't know" and "there's nothing we can do", the least risky personal scenario. And so that's what they chose. Over and over and over.)
For example, according to NASA people who were there at the time (like the flight director), management didn't just refuse to ask DoD for help imaging the orbiter, they actively blocked attempts by others to ask for help. There was only a 50/50 chance the images would be useful, but there was no risk to anyone if they weren't. So why block it? Not just "I don't think it's worth it", but actively preventing others from requesting it.
On orbit repair sounds great, except that building all the hardware is more expensive than just letting the shuttle burn up and riding back down on a soyuz.
Rubbish. They put it into production after Columbia. And flew the repair kits on nearly every flight afterwards. Repair (and rescue) scenarios were considered from the beginning of the shuttle program. And they were constantly blocked or undermined by senior management. The loss of Columbia was a culmination of that attitude.
Certain functions physically couldn't be activated remotely. Starting the APUs to power up the hydraulics, deploying the air-speed pitot tube, lowering the landing gear, and popping the drag 'chutes after touchdown. The orbiters had normal on-board auto-pilots, but these also couldn't be activated or controlled from the ground.
The last few missions (post-Columbia) had a 28 foot long cable to physically connect the flight controls to the avionics computer in the mid-deck, to allow remote reentry control, if the crew had to be brought home on a rescue shuttle. http://en.wikipedia.org/wiki/STS-3xx#Remote_Control_Orbiter. It's only wiki, but it was the easiest to dig up.
Re: Autopilot landings.
It was never used during landing. During the third mission, the autopilot controlled the descent to 200ft, then the pilot took over. He found it awkward and landed hard, and the review committee (made up of astronaut-pilots) concluded that a pilot would have difficulty taking over during an emergency, because they wouldn't have time to get a "feel" for the flight. So after that no mission ever attempted to landed on auto-pilot. (It was still used during reentry, but as soon as the orbiter had enough atmosphere to use its flight-controls, the pilot took over.) There was a group who still wanted to use the autopilot, but the whole idea was officially killed around 1984.
The shuttles weren't able to land unmanned, due to quite deliberate decisions made during their development, against engineer requests, which shows just how long the current management style has been operating.
Actually, first you would have to ask the Columbia crew if they wanted to take the risk of doing an (untrained) EVA to go out and assess the actual damage, or take the risk of landing without knowing.
with full knowledge.
Clearly not.
According to NASA people there at the time, there was a very deliberate campaign by senior management to block attempts to assess damage, or get help from outside the agency (they refused DoD's offer to image the shuttle), or prepare for the worst. They had decided at the first meeting that "nothing could be done", and any attempt to tell them otherwise was shut down.
An example of that attitude is in the report itself, the only rescue scenario even looked at was rushing Atlantis into service. No analysis of sending up a Proton with supplies, or an empty Soyuz to retrieve three (maybe four) crew to reduce the demand on the LSS and extend the time available to stage the Atlantis rescue. [Ie, rushing the launch of an unmanned rocket to reduce the risk from rushing the manned rescue.]
Columbia could have been their finest hour. Instead it was a perfect example of how the agency is rotting away. And failing to call them on that, because we don't want to offend their delicate sensibilities, just begs for a continuation of the rot.
Do I need to remind you of Feynman's shredding of NASA's credibility in the Challenger investigation? Or the more recent report that showed using a solid stage on SLS would likely result in an unsurvivable abort scenario (due to burning solid fuel destroying the parachutes). Or the recent report that says Orion is too heavy for the Navy to recover...
How about the fact that on-orbit repair scenarios had been suggested and studied by engineering groups ever since the shuttle was built, but not one piece of hardware was even allowed to be built, let alone flown. Not even after Challenger.
The agency repeats the same mistakes over and over and over...
[And it's not just manned missions: http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure "The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed."]
No... I don't think so.
(Every beancounter in the government will tell you, NO orbiter is expendable, if there's even a remote chance to bring back that multi-billion dollar device -- which is why they created the 28ft/5lb "RCO IFM" cable after Columbia... the crew can plug it in, bug out, and let Huston land the thing.)
Necessitated by the very deliberate decision, widely criticised at the time, to not design remote landing capability into the shuttle in order to enforce the "need" to use astronaut-pilots.
without approximately 12,600 ft/sec of translational capability. Columbia had 448 ft/sec of propellant available.
Who the fuck measures delta-v in foot/seconds?
Weird. Every phone I've ever owned has a removable battery. Not one has ever done this, even when accidentally I drop them on the floor. How hard are you slamming them down?
The short version is that horizontal velocity of the surface of Earth at the equator is about 800 m/s. The horizontal velocity of GEO is 3000 m/s. The car has to gain that horizontal velocity as it climbs (and lose it as it falls), and it does so by stealing it from the cable, this causes that section of the cable to "lag" behind as it passes the loss to the ground (eventually stealing the energy from Earth's rotation). That creates the moving kink in the cable.
Sayeth the wikipedia...
However, the industry itself only really exists because of that modularity. Small vendors being able to assemble niche systems from modular components, without having to do high-end electrical engineering and manufacturing.
Modular "phones" won't be modified by more than a fraction of the most nerdish end-users, but they will be a boon to other device makers. Companies are already using cellphone and tablet parts as cheap, standardised, easy-to-design-for control systems and/or displays for their products. Likewise, companies are making niche products that plug into a standard cellphone, rather than require their own computer/display/battery/etc.
With modularity, that ability increases exponentially.
The number of people talking about the issue of balancing the elevator makes me think perhaps I have misunderstood.
Different emphasis depending on what you are trying to explain. The system is almost in balance. The amount of tension at the ground is completely arbitrary. So when discussing payload movement, it's the "almost" that's important. When explaining how the concept works to someone (Chas) who thinks it's a billion-tonne "tower" pressing on the ground, it's the "balance" that's is emphasised to them.
Want to put a heavy load on the ribbon bottom? Send a signal to have the counterweight climb further up
That would work, but IMO if the ribbon is capable of handling the force from the climber+payload, then why not use a base-anchor heavy enough to handle the tension when there isn't a climber? Ie, leave the system in permanent tension.
For early versions (small ribbon, no GEO station), apparently they want to have winches on Earth feed out excess ribbon to increase tension, or pull it back to reduce it. The idea is to keep the tension on the ground-station roughly constant, and fairly light. This is because they assume the first version will be at the very edge of possible, and kept as small and light as possible in order to be able to build it at all. For example, the counterweight would be the rocket-stage and drum from the original deployment. You start in GEO and let out the ribbon, the drum naturally moves outwards to balance the descending arm. [Rather than the usual image of a central deployment at GEO feeding out two arms in balance.]
Re: wobbling versus retracting.
It would also take a long time to winch up and redeploy it each time, during which the the system is useless. Given the number of satellites (especially in LEO) and orbital debris that it would have to dodge out of the way of, it wouldn't spend enough time in operation to justify its existence. During a ship-driven "wobble", otoh, it can still be launching and retrieving climbers.
Or...
Christians
Jews
Communists
White supremacists
Environmentalists
Neo-luddites
Unionists.
And whatever the fuck these guys are.
There's only three buttons.
There's a torque force on the tether due to Coriolis. Because it causes a moving bend in the cable, it's a nastier effect than the simple linear forces on the cable. The faster the car travels, the more severe the force, the sharper the bend. (From an engineering standpoint, it's like a shockwave travelling up the cable. Go above the speed-of-sound-in-the-material, and it's a supersonic shockwave inside the tether. But even below the speed of sound, it's a nasty effect.)
Actually there are proposals that take the properties of modern super materials (carbon composites) and calculate the maximum height of a (compression) tower. And, depending on your assumptions, you can actually get above 100km. Even steel towers could theoretically get to 10-15km using modern designs.
There are also designs for rotating orbital tethers which have a tip-velocity equal to the Earth's surface velocity, dipping into the atmosphere to pick up airborne payloads. (Or tower-borne if you combined it with the 100km carbon-tower.) From an engineering and economic standpoint, these are much simpler than a full space elevator, since they require much less strength in the materials, and are built at much shorter lengths.
There are also proposals for neutral buoyancy towers which are... theoretically... possible. (Essentially a series of hydrogen-filled balloon toruses stacked on top of each other, creating a net lift sufficient to hold another tower on top, above the bulk of the atmosphere.)
Seriously, we're talking about a 22,000 mile cable
No. It's at least double that. A space elevator doesn't just go up to GEO, it's "balanced" at GEO, there's an entire outward arm. (And in reality it would be under tension, so the outer arm would be more massive than the inner, the balance point would be well below GEO.)
where a single fault could cause the whole thing to come crashing down.
No fault could cause the "whole thing to come crashing down". Only the portion below the break could fall. And since it's a known failure mode, you'd have built-in separation points at various lengths. When there's a failure, you release a piece of cable/ribbon at the top and/or bottom ends of sufficient mass to allow the centre section to go into a stable orbit. This allows recovery and repair.
The world.
Show me any application of continuous nanotube material beyond trivial length. Just one example. Not some guy pontificating in a podcast, but an actual example of use.
A space elevator requires tens of thousands of kilometres of cable or ribbon at close to the theoretical maximum strength of nanotubes.
From what I've seen, the longest true lengths outside a lab are millimetres. The longest lengths of usable "thread" are metres, but are made of a tangle of sub-millimetre nanotubes not a continuous length, and so are well below the theoretical minimum strength required for a space elevator, let alone the much greater practical engineering strength required for a real one.
No-one is making macro lengths of nanotubes. No-one is making macro lengths of any material at close to the strength required for space elevators.
You are contradicting yourself. If a single car is sufficient to pull a "balanced" tether out of orbit, then only a similarly small outward force is necessary to counter the force of a car, therefore even a small base-mass (such as a ship or barge) is sufficient to counter that outward force. Ie, if a one tonne car pulling down at 1.5g would pull the tether out of orbit, then you only need a few tonnes outward force (measured at the base) to prevent that. And thus only a few tonnes beyond that to sufficiently anchor the tether down.
Therefore you do not need to "drill really deep into bedrock to suitably anchor this beast".
(In reality, you'd want an outward force a full order of magnitude higher than the cargo capacity. And an anchor-mass another order of magnitude higher than that. So a 1 tonne payload, a ten tonne outward force, a 100 tonne base. Double or triple for reserve. Well within the capability of even a small ship or barge.)
A bigger problem is actually the sidewards torque due to Coriolis as the cars rise and fall. This creates not only additional pull on the cable/ribbon, but specifically bends or crimps the ribbon as the car passes. This will stress the material well beyond the simple linear forces.