Yeah, that's what he's saying. Though with more motion, and less respect for gravity. Similarly, too much digitalis can make things look like this. Generalizations about exactly what LSD hallucinations look like are a bad idea, though -- it's highly variable, with strong dependence on the person, the dose, the setting, the person's mood...
In this case, it's appropriate. The study authors suggest that there may be causation, but also state that all they have evidence of is correlation -- and that the causation may go the other direction. The/. summary fabricated the causation without regards to the linked article, let alone the study.
The study authors imply only a link, not causation. "Correlation is not causation" is a bit overused around here, but in this case it's worth repeating since the/. summary introduced the error. FTFA:
The researchers believe that caffeine could heighten the effect that stress has on the body, triggering the hallucinations.
However, they also suggest that people who are more prone to hallucinations could also be more stressed and more likely to consume large amounts of caffeine.
For the most part, LSD doesn't cause true hallucinations -- it distorts things. You'll see the wood grain on your desk flowing, or the tree waving at you... but you won't see a pink unicorn in the room next to you that doesn't correspond to some vaguely similar object that's actually there. Take a high enough dose, and the level of distortion gets high enough that it's hard to figure out whether that's still the case. But at the 1 dose level, the vast majority of people don't experience true hallucinations -- and it sounds like they're suggesting that with caffeine, that's not true.
Because if they do that, you'll save it. Normally, that would be a good thing -- invested money promotes growth and all that. In a recession, though, everyone is worried that their investments will go down, so they just hold their dollars. These concerns apply to money in your savings account that the bank would normally invest as well. However, if the government spends the money, that doesn't happen.
You can view the economic situation right now as a Prisoner's Dilemma. Everyone would be better off if everyone would just get over it and spend money. But, short term, the economy is on shaky ground at best, so I'm better off not spending regardless of what other people do. So no one spends money, even though everyone would be better off if everyone spent money. Once the cycle starts, it's no longer a PD problem, but the initial state is. One way out of a PD is by agreement -- both players make a contract to not rat each other out (ie spend money). That contract needs enforcing, though, and one way to do that is to have the government spend money via taxes and deficit spending (ie delayed taxes / tax by inflation).
In other words... lower taxes promote growth, normally. But when the trust that is the basis of our economy starts to crumble, it can make sense to have the government spend money by spending it rather than by cutting taxes.
Patents are supposed to be about the non-obvious. Most software, and most software patents, are relatively obvious improvements to the current state of the art. The fact that it is obvious does not mean the problem does not exist, or that your solution is not useful and marketable. For the software industry as it stands today, patents are more of a hindrance to innovation than a component of it. Your customers want the software, so you write it. You patent it so you can sue your competitors and as a defensive act -- but the profit to be made from a patent, either in licensing it or in keeping competitors out, is rarely part of the decision to develop the software. Most of the competitive advantage a software company has is well protected by copyright, without any need for patents.
And if the software in question was open source, those customizations could be contributed back upstream and used by more people. Which means they'd be less likely to be broken by other changes, and other people's customizations would be more likely to be compatible... in other words, less of a support nightmare. (Not trying to claim it would be easy... just better than it is now.)
The first paper includes cost estimates. There's nothing hard about the cables to hold it down; they can be as thick as they need to be. The original paper has numbers for them using ordinary steel cable -- they're tapered, so they're a little abnormal, but strength certainly isn't a problem. The weight problem is more likely to be keeping the sheath light enough that the ribbon can stay up. Each kg of ribbon can lift a little less than 1 kg of other stuff, including sheath, cables, and payload. Seriously, the materials science is not the hard part, and neither is the physics.
Building a test model is actually a place where the launch loop does well in comparison to the other mega-scale engineering proposals. A small scale launch loop is useful, unlike an elevator. A launch loop that's an arch capable of lofting your payload to 50km and 2km/s is decidedly useful -- that's an excellent starting point for the second stage of a rocket.
I'll have to get back to you on a lab bench scale test. I don't know of any that have been done; I do, however, have some magnets in the mail for exactly that purpose. It's very much a back burner project, though, so don't expect results for a couple months. (Try building a laser launch demonstrator in your garage by yourself on a 3-digit budget...)
What part needs magic materials? The ribbon is made of soft iron iron or steel, probably woven in a manner not unlike normal cables, or possibly in solid sheets. That's not exactly difficult to make. The sheath is a kevlar or carbon fiber composite with an aluminized mylar liner. The control magnets are copper windings over soft iron. You didn't actually read any of the papers, did you?
What part of "mega-scale engineering project" made you think this would be small?
Surprising as it may seem, every one of your questions is addressed in published papers. Many of them can be found in the references section of the Wikipedia article I linked to.
Your argument in favor of laser launchers has no meaning without either some numbers to back it up or at least some sound logic as to why the expensive capital investment is less than for a [launch loop|space elevator|rocket fleet] or is made up for by reduced operating costs (including but not limited to energy consumption).
You don't have to hang it up there; it stays up by itself. The ribbon is moving faster than orbital velocity (14 km/s -- orbital is a bit over 7), so its natural tendency to go in a straight line means that the Earth's surface curves away from it. You then have to apply tension with cables to hold it down and make it follow the curvature of the Earth (from 80 km up, of course). The problems with the launch loop lie in things like the control systems and the quantity of stored energy, not the basic physics. Wrapping your head around it takes a little work, but in many ways it works for the same reason that the space elevator counterweight does -- both the ribbon and the counterweight are moving at a higher velocity than orbital velocity for their altitude, so they try to "fall" away from the Earth and thus maintain tension in the cable[s].
IMHO the laser launcher is yet another result of the common fallacy that mass ratio actually matters. It doesn't; cost does. If you save a lot of mass while making the whole thing more expensive, that's not a win. I should add the caveat that I'm not current on the detailed numbers, so I may be mistaken, but that's my general impression of it. (Obviously mass ratio matters to the extent it has an impact on cost; but that is the *full* extent to which it matters.)
Oddly enough, that is precisely the problem. A Faraday cage works because the conductive shield allows eddy currents to flow, which create fields in opposition to the original event. This prevents things inside the cage from seeing what happened outside. Unfortunately, the cage in this case is our power grid -- and the eddy currents in it are precisely the things causing concern.
The rocket is not perfectly efficient; neither is the elevator. As I explained above, plausible estimates put the efficiency difference at about a factor of 5. That number can vary by a factor of at least 3 (in either direction) depending on which kool-aid you prefer. The implication of this is that for the short and medium term, the reduced capital cost of the rockets dominates. For the long term, where energy costs are actually relevant, the elevator wins -- but that problem is properly classed as "a very nice problem to have." It will be a long time before we do, and until then, rockets make more sense.
Have you actually run the numbers on efficiency? I have. A rocket (built from space elevator class magic nanotubes, of course) is somewhere around 5-8% efficient at converting energy on the ground to energy in the payload; somewhat more if you use hydrogen instead of dense propellants, and somewhat more if you count the rocket bits in orbit as useful rather than dead weight.
How efficient the space elevator is varies depending on your assumptions about beamed power efficiency (or other means of getting power to the climber). You still have to put the vast majority of the energy into the payload directly. At geosynchronous altitude, the vast majority of your energy is in the form of gravitational potential energy that comes from your climber, not kinetic energy that comes from Coriolis forces. The climber will probably have an unexciting payload fraction (motors and energy collectors are heavy), and less than stellar conversion efficiencies. 50% overall would imply roughly 70% payload fraction and 70% conversion efficiency; that seems optimistic to me. 25% efficiency seems much more reasonable, but still a definite engineering challenge (especially if you want to climb quickly).
That says that a rocket launch uses only 5x the energy of the elevator for a given payload. The capital costs are dramatically reduced. A notional nanotube SSTO has a nanotube tankage mass noticeably less than its payload mass. It can fly several times per day, if you have an equatorial launch site or aren't too picky about destination orbit. A space elevator is *massive* compared to its payload, and has a limited number of climbers launching each day (weight limits on the lower portion of the cable are severe). The capital cost per lofted kg per day is vastly lower with the rockets than the elevator. For unproven markets, this difference is important. For current rocket launches, and any sane model for early elevator launches, the capital costs dominate the energy costs. Until there is enough of a proven launch market that you can take a business plan to investors that reasonably assumes near-100% utilization of your elevator for several years of useful life, the rockets win. The fact that the rocket version of the business plan can be made workable at much lower launch rates is a nontrivial benefit.
Sure, the space elevator makes sense many years from now, when there is a thriving space-based economy with regular demand and plenty of destinations. That world is not the one we live in today. For the near term, and even medium term, rockets will beat space elevators on price per kg launched -- especially if you give the rocket engineers space-elevator class building materials.
Yeah, when you start applying space elevator class building materials to your rocket tankage, the usual assumptions simply don't apply. For example: with 65GPa tensile strength (the low end of the strength range Wikipedia gives for an elevator material) material for tankage, a 1000 psi tank filled with dense propellants (which, depending upon your models, might be better) has a mass ratio of somewhere over 1000. The exact number depends on your assumptions about anisotropic winding strength efficiency, but is probably around 1500 before you include a safety margin.
The helium to pressurize it with is actually the most problematic part -- but with that kind of tank mass ratio, it's not unreasonable to decide you're going to operate in blowdown mode (or regulated, but decaying to a lower final pressure) so that you have less helium mass at burnout. That lets you get the high initial chamber pressure (good atmospheric expansion ratio) without all the helium mass required to pressurize the entire tank. And using the ullage helium for the circularizing burn isn't hard (you could even include a peroxide monoprop heater and get a reasonable Isp out of it).
You can get slightly better Isp than that, actually. For example, I get 4664 m/s vacuum Isp for O:F of 6:1 and 3000 psi expanded to 1 psi. I don't know what pressure they run at, but for a wide altitude range I would imagine it's high. Furthermore, I believe they plan to still be using some outside air even at Mach 5 -- and at that altitude, they've also got some delta-v in the altitude itself, not just the velocity. Small effects, but they help... Anyway, I don't know the details of their flight plan, but I do know that the engineers behind it are decidedly competent, and do have a detailed trajectory plan that includes good estimates of air drag and such. If you can find trajectory details, though, I'd love to see them...
(Oh, to pick a few nits about your dv budget... 7.2 km/s is orbital velocity; don't forget nearly 500 m/s of Earth rotational velocity. So if you ignore air and gravity drag, it's actually slightly under 7 km/s total delta-v, though air and gravity drag will usually add more than 2 km/s to that.)
I don't much like the idea of a space elevator, at least for short- or medium-term applications. (Long term, is 50 years from now, is different... but also not very relevant.) Why, you ask? Simple. Give me a space-elevator class building material, and I'll make rocket tankage out of it long before it's fully developed to space elevator performance levels. Those tanks will be so vastly superior in weight performance to current materials that I can give you a rocket that is not only single stage to orbit, but does it on *pressure fed* engines. Who needs turbopumps and all their associated machinery when you can just put enough pressure in the tanks (and run at a lower chamber pressure... which is more conducive to high reliability anyway)?
For a given payload rate, my pressure fed SSTO will use somewhere between 3 and 10 times the energy (depending on which kool-aid you drink when it comes to getting the power from the ground to the elevator car). It will have a *vastly* lower capital cost. It will be faster (no radiation worries for cargo that spends days passing through the van Allen belts). Perhaps more importantly, it will scale down better. It starts with a lower investment and lower flight rate to prove out demand, and then grows as more customers appear and more rockets get built.
Oh, reusability? It gets a lot easier when you don't have to jettison a stage a third of the way there -- and when your reentry vehicle is as light and fluffy as these building materials imply, it gets even easier. Engine reusability is pretty trivial when you don't have 60,000 rpm turbines wearing out all the time.
There are plenty of engineering problems to be overcome for a space elevator. They're not impossible, but they're far from trivial. But the real problem is the competition from rockets -- it makes zero sense to compare a space elevator built with magic nanotubes to a lithium-aluminum tankage rocket; it should be compared to a magic nanotube rocket. When you do that, you discover that for any unproven market (ie, where capital costs matter) the spaceship fleet is far, far cheaper.
Yep, all good points... I will observe, however, that the Shuttle SRB *is* a gimballed engine. Yes, they have a flexible hot gas joint that can handle that much flow and that much thrust. It obviously can't do roll control with only one engine (which means another new system...) but it can handle pitch/yaw just fine. The reason? The Shuttle doesn't have enough control authority with just the SSMEs to handle unexpected aerodynamic loads or thrust asymmetry between the SRBs, so they had to have thrust vectoring to make the Shuttle work.
Oh, yes, that's absolutely true. But the parent posts assertion that simply because my premium saved over long enough means I can save up for a $10k hospital bill I can afford to not have insurance against said hospital bill is horribly self-centered... not everyone is in the same financial position he's in.
Just have it send him a notification email that the email he just tried to sent appeared to be spam, and while it was sent successfully he should verify that his system is in fact virus-free. One notification per email sent, of course.
Let's suppose a [coworker|friend|colleague] sends an email to me, ccing three other people. I want to respond and CC those same people. Exactly what button should I press, if not reply all? Or are you one of those people that think forcing me to do things the hard way and copy those addresses manually to the CC line is a feature, because you don't know how to set up a mailing list so this doesn't happen?
Slashdot Mirror
Yeah, that's what he's saying. Though with more motion, and less respect for gravity. Similarly, too much digitalis can make things look like this. Generalizations about exactly what LSD hallucinations look like are a bad idea, though -- it's highly variable, with strong dependence on the person, the dose, the setting, the person's mood...
In this case, it's appropriate. The study authors suggest that there may be causation, but also state that all they have evidence of is correlation -- and that the causation may go the other direction. The /. summary fabricated the causation without regards to the linked article, let alone the study.
The study authors imply only a link, not causation. "Correlation is not causation" is a bit overused around here, but in this case it's worth repeating since the /. summary introduced the error. FTFA:
The researchers believe that caffeine could heighten the effect that stress has on the body, triggering the hallucinations.
However, they also suggest that people who are more prone to hallucinations could also be more stressed and more likely to consume large amounts of caffeine.
For the most part, LSD doesn't cause true hallucinations -- it distorts things. You'll see the wood grain on your desk flowing, or the tree waving at you... but you won't see a pink unicorn in the room next to you that doesn't correspond to some vaguely similar object that's actually there. Take a high enough dose, and the level of distortion gets high enough that it's hard to figure out whether that's still the case. But at the 1 dose level, the vast majority of people don't experience true hallucinations -- and it sounds like they're suggesting that with caffeine, that's not true.
Because if they do that, you'll save it. Normally, that would be a good thing -- invested money promotes growth and all that. In a recession, though, everyone is worried that their investments will go down, so they just hold their dollars. These concerns apply to money in your savings account that the bank would normally invest as well. However, if the government spends the money, that doesn't happen.
You can view the economic situation right now as a Prisoner's Dilemma. Everyone would be better off if everyone would just get over it and spend money. But, short term, the economy is on shaky ground at best, so I'm better off not spending regardless of what other people do. So no one spends money, even though everyone would be better off if everyone spent money. Once the cycle starts, it's no longer a PD problem, but the initial state is. One way out of a PD is by agreement -- both players make a contract to not rat each other out (ie spend money). That contract needs enforcing, though, and one way to do that is to have the government spend money via taxes and deficit spending (ie delayed taxes / tax by inflation).
In other words... lower taxes promote growth, normally. But when the trust that is the basis of our economy starts to crumble, it can make sense to have the government spend money by spending it rather than by cutting taxes.
Patents are supposed to be about the non-obvious. Most software, and most software patents, are relatively obvious improvements to the current state of the art. The fact that it is obvious does not mean the problem does not exist, or that your solution is not useful and marketable. For the software industry as it stands today, patents are more of a hindrance to innovation than a component of it. Your customers want the software, so you write it. You patent it so you can sue your competitors and as a defensive act -- but the profit to be made from a patent, either in licensing it or in keeping competitors out, is rarely part of the decision to develop the software. Most of the competitive advantage a software company has is well protected by copyright, without any need for patents.
And if the software in question was open source, those customizations could be contributed back upstream and used by more people. Which means they'd be less likely to be broken by other changes, and other people's customizations would be more likely to be compatible... in other words, less of a support nightmare. (Not trying to claim it would be easy... just better than it is now.)
The first paper includes cost estimates. There's nothing hard about the cables to hold it down; they can be as thick as they need to be. The original paper has numbers for them using ordinary steel cable -- they're tapered, so they're a little abnormal, but strength certainly isn't a problem. The weight problem is more likely to be keeping the sheath light enough that the ribbon can stay up. Each kg of ribbon can lift a little less than 1 kg of other stuff, including sheath, cables, and payload. Seriously, the materials science is not the hard part, and neither is the physics.
Building a test model is actually a place where the launch loop does well in comparison to the other mega-scale engineering proposals. A small scale launch loop is useful, unlike an elevator. A launch loop that's an arch capable of lofting your payload to 50km and 2km/s is decidedly useful -- that's an excellent starting point for the second stage of a rocket.
I'll have to get back to you on a lab bench scale test. I don't know of any that have been done; I do, however, have some magnets in the mail for exactly that purpose. It's very much a back burner project, though, so don't expect results for a couple months. (Try building a laser launch demonstrator in your garage by yourself on a 3-digit budget...)
What part needs magic materials? The ribbon is made of soft iron iron or steel, probably woven in a manner not unlike normal cables, or possibly in solid sheets. That's not exactly difficult to make. The sheath is a kevlar or carbon fiber composite with an aluminized mylar liner. The control magnets are copper windings over soft iron. You didn't actually read any of the papers, did you?
What part of "mega-scale engineering project" made you think this would be small?
Surprising as it may seem, every one of your questions is addressed in published papers. Many of them can be found in the references section of the Wikipedia article I linked to.
Your argument in favor of laser launchers has no meaning without either some numbers to back it up or at least some sound logic as to why the expensive capital investment is less than for a [launch loop|space elevator|rocket fleet] or is made up for by reduced operating costs (including but not limited to energy consumption).
I have not actually tried the beta yet. I hear it's quite pleasant and hardly Hitler-y at all.
(For those that don't read it regularly, you should really read the alt text as well.)
You don't have to hang it up there; it stays up by itself. The ribbon is moving faster than orbital velocity (14 km/s -- orbital is a bit over 7), so its natural tendency to go in a straight line means that the Earth's surface curves away from it. You then have to apply tension with cables to hold it down and make it follow the curvature of the Earth (from 80 km up, of course). The problems with the launch loop lie in things like the control systems and the quantity of stored energy, not the basic physics. Wrapping your head around it takes a little work, but in many ways it works for the same reason that the space elevator counterweight does -- both the ribbon and the counterweight are moving at a higher velocity than orbital velocity for their altitude, so they try to "fall" away from the Earth and thus maintain tension in the cable[s].
IMHO the laser launcher is yet another result of the common fallacy that mass ratio actually matters. It doesn't; cost does. If you save a lot of mass while making the whole thing more expensive, that's not a win. I should add the caveat that I'm not current on the detailed numbers, so I may be mistaken, but that's my general impression of it. (Obviously mass ratio matters to the extent it has an impact on cost; but that is the *full* extent to which it matters.)
Yes. Your user screen -> preferences -> authors. Uncheck the box of any you don't want to see.
So would a tiny blob of dimethyl mercury. For all that successful delivery would be a pain, it would be easier than this thing.
Oddly enough, that is precisely the problem. A Faraday cage works because the conductive shield allows eddy currents to flow, which create fields in opposition to the original event. This prevents things inside the cage from seeing what happened outside. Unfortunately, the cage in this case is our power grid -- and the eddy currents in it are precisely the things causing concern.
The rocket is not perfectly efficient; neither is the elevator. As I explained above, plausible estimates put the efficiency difference at about a factor of 5. That number can vary by a factor of at least 3 (in either direction) depending on which kool-aid you prefer. The implication of this is that for the short and medium term, the reduced capital cost of the rockets dominates. For the long term, where energy costs are actually relevant, the elevator wins -- but that problem is properly classed as "a very nice problem to have." It will be a long time before we do, and until then, rockets make more sense.
Have you actually run the numbers on efficiency? I have. A rocket (built from space elevator class magic nanotubes, of course) is somewhere around 5-8% efficient at converting energy on the ground to energy in the payload; somewhat more if you use hydrogen instead of dense propellants, and somewhat more if you count the rocket bits in orbit as useful rather than dead weight.
How efficient the space elevator is varies depending on your assumptions about beamed power efficiency (or other means of getting power to the climber). You still have to put the vast majority of the energy into the payload directly. At geosynchronous altitude, the vast majority of your energy is in the form of gravitational potential energy that comes from your climber, not kinetic energy that comes from Coriolis forces. The climber will probably have an unexciting payload fraction (motors and energy collectors are heavy), and less than stellar conversion efficiencies. 50% overall would imply roughly 70% payload fraction and 70% conversion efficiency; that seems optimistic to me. 25% efficiency seems much more reasonable, but still a definite engineering challenge (especially if you want to climb quickly).
That says that a rocket launch uses only 5x the energy of the elevator for a given payload. The capital costs are dramatically reduced. A notional nanotube SSTO has a nanotube tankage mass noticeably less than its payload mass. It can fly several times per day, if you have an equatorial launch site or aren't too picky about destination orbit. A space elevator is *massive* compared to its payload, and has a limited number of climbers launching each day (weight limits on the lower portion of the cable are severe). The capital cost per lofted kg per day is vastly lower with the rockets than the elevator. For unproven markets, this difference is important. For current rocket launches, and any sane model for early elevator launches, the capital costs dominate the energy costs. Until there is enough of a proven launch market that you can take a business plan to investors that reasonably assumes near-100% utilization of your elevator for several years of useful life, the rockets win. The fact that the rocket version of the business plan can be made workable at much lower launch rates is a nontrivial benefit.
Sure, the space elevator makes sense many years from now, when there is a thriving space-based economy with regular demand and plenty of destinations. That world is not the one we live in today. For the near term, and even medium term, rockets will beat space elevators on price per kg launched -- especially if you give the rocket engineers space-elevator class building materials.
Yeah, when you start applying space elevator class building materials to your rocket tankage, the usual assumptions simply don't apply. For example: with 65GPa tensile strength (the low end of the strength range Wikipedia gives for an elevator material) material for tankage, a 1000 psi tank filled with dense propellants (which, depending upon your models, might be better) has a mass ratio of somewhere over 1000. The exact number depends on your assumptions about anisotropic winding strength efficiency, but is probably around 1500 before you include a safety margin.
The helium to pressurize it with is actually the most problematic part -- but with that kind of tank mass ratio, it's not unreasonable to decide you're going to operate in blowdown mode (or regulated, but decaying to a lower final pressure) so that you have less helium mass at burnout. That lets you get the high initial chamber pressure (good atmospheric expansion ratio) without all the helium mass required to pressurize the entire tank. And using the ullage helium for the circularizing burn isn't hard (you could even include a peroxide monoprop heater and get a reasonable Isp out of it).
Actually, if you want a mega-scale engineering project, my personal preference is for the launch loop.
You can get slightly better Isp than that, actually. For example, I get 4664 m/s vacuum Isp for O:F of 6:1 and 3000 psi expanded to 1 psi. I don't know what pressure they run at, but for a wide altitude range I would imagine it's high. Furthermore, I believe they plan to still be using some outside air even at Mach 5 -- and at that altitude, they've also got some delta-v in the altitude itself, not just the velocity. Small effects, but they help... Anyway, I don't know the details of their flight plan, but I do know that the engineers behind it are decidedly competent, and do have a detailed trajectory plan that includes good estimates of air drag and such. If you can find trajectory details, though, I'd love to see them...
(Oh, to pick a few nits about your dv budget... 7.2 km/s is orbital velocity; don't forget nearly 500 m/s of Earth rotational velocity. So if you ignore air and gravity drag, it's actually slightly under 7 km/s total delta-v, though air and gravity drag will usually add more than 2 km/s to that.)
I don't much like the idea of a space elevator, at least for short- or medium-term applications. (Long term, is 50 years from now, is different... but also not very relevant.) Why, you ask? Simple. Give me a space-elevator class building material, and I'll make rocket tankage out of it long before it's fully developed to space elevator performance levels. Those tanks will be so vastly superior in weight performance to current materials that I can give you a rocket that is not only single stage to orbit, but does it on *pressure fed* engines. Who needs turbopumps and all their associated machinery when you can just put enough pressure in the tanks (and run at a lower chamber pressure... which is more conducive to high reliability anyway)?
For a given payload rate, my pressure fed SSTO will use somewhere between 3 and 10 times the energy (depending on which kool-aid you drink when it comes to getting the power from the ground to the elevator car). It will have a *vastly* lower capital cost. It will be faster (no radiation worries for cargo that spends days passing through the van Allen belts). Perhaps more importantly, it will scale down better. It starts with a lower investment and lower flight rate to prove out demand, and then grows as more customers appear and more rockets get built.
Oh, reusability? It gets a lot easier when you don't have to jettison a stage a third of the way there -- and when your reentry vehicle is as light and fluffy as these building materials imply, it gets even easier. Engine reusability is pretty trivial when you don't have 60,000 rpm turbines wearing out all the time.
There are plenty of engineering problems to be overcome for a space elevator. They're not impossible, but they're far from trivial. But the real problem is the competition from rockets -- it makes zero sense to compare a space elevator built with magic nanotubes to a lithium-aluminum tankage rocket; it should be compared to a magic nanotube rocket. When you do that, you discover that for any unproven market (ie, where capital costs matter) the spaceship fleet is far, far cheaper.
Yep, all good points... I will observe, however, that the Shuttle SRB *is* a gimballed engine. Yes, they have a flexible hot gas joint that can handle that much flow and that much thrust. It obviously can't do roll control with only one engine (which means another new system...) but it can handle pitch/yaw just fine. The reason? The Shuttle doesn't have enough control authority with just the SSMEs to handle unexpected aerodynamic loads or thrust asymmetry between the SRBs, so they had to have thrust vectoring to make the Shuttle work.
Oh, yes, that's absolutely true. But the parent posts assertion that simply because my premium saved over long enough means I can save up for a $10k hospital bill I can afford to not have insurance against said hospital bill is horribly self-centered... not everyone is in the same financial position he's in.
Just have it send him a notification email that the email he just tried to sent appeared to be spam, and while it was sent successfully he should verify that his system is in fact virus-free. One notification per email sent, of course.
Let's suppose a [coworker|friend|colleague] sends an email to me, ccing three other people. I want to respond and CC those same people. Exactly what button should I press, if not reply all? Or are you one of those people that think forcing me to do things the hard way and copy those addresses manually to the CC line is a feature, because you don't know how to set up a mailing list so this doesn't happen?