I recently researched buying an electric on-demand water heater for my own home. Such heaters consume around 10-20kW and can demand 100 amps of current, they are however very efficient (as someone else noted) and so there is little waste to squeeze out of the system (a few percent at most I expect).
Using microwave generating magnetrons is likely to be less efficient imo, so it is very hard to see how this company can live up to its claims. Whether by microwave or resistive heating, the same amount of energy needs to get into the water, it is not at all like a food stove where microwave ovens are genuinely more efficient (less heat loss and only the item being cooked is heated, not the stove walls too).
The reason I didn't purchase an on-demand heater is that the electric service in my house would have to be upgraded, at a cost of around $3000. A new water tank, with heater, cost $700. The microwave heater would also have this cost issue.
A better way to save power (nationally) would be to have dual-band power pricing (as is done in the UK) where power used in off peak hours costs less than in peak hours -- in this case a storage tank is potentially MORE efficient than on-demand since it can shift demand to off-peak hours when there is unused capacity. In any event, I doubt that a properly insulated water tank actually loses much heat, the main advantage of on-demand is that there is a never-ending supply of hot water.
Andy
Being an SE enthusiast and having presented at two of the SE conferences, perhaps I can provide some useful background.
The single greatest challenge to building an SE remains that of producing suitable material for its main structural element - the cable.
A practical Space Elevator requires a material of ultimate strength of at least 50 GPa. Individual nanotubes have been made with several times this strength, but no bulk material has approached it yet. Pure single walled carbon nanotube fibres of length 4mm or greater should produce a spun yarn with strength in excess of 100 GPa and such nanotubes have been produced in 40mm lengths, but not in useful quantities. Steel reaches 5 GPa, but has 4 or 5 times the density of CNTs and so only has a fortieth of the specific strength needed. Aramid fibres such as spectra, dyneema and kevlar come closer, but are only useful for lunar or martian SEs, not earth ones.
Almost all other issues, such as terrorism / securing the base station / wind / lightning / discharging the ionosphere / lunar and solar tidal effects / atomic oxygen erosion / radiation damage / collisions with the ISS / swarf infall / cyclic heating and cooling / broken ribbon fragments landing on people or damaging the environment etc. either turn out to be insignificant or are fairly easily solved with a little thought and effort.
The two problems that are harder to solve are: micrometeoroid impact and what has been called 'fratricide' -- where fragments from one SE failing hit other SEs. The likely solution to the micrometeoroid (mm) problem is to make the size and shape of the SE ribbon such that mms do not degrade its strength significantly during the lifetime of the SE. Fratricide is very hard to deal with and will require that ribbons be designed to be VERY unlikely to fail and that they incorporate ways to affect the paths of fragments.
Beyond these problems there remain numerous areas of investigation such as the fundamental 'mode' or shape of SE to use -- a single straight cable, or a loop, or a straight cable with pieces that are cut from the upper end. Will a material be available that will allow loops or constant-thickness cables (requires 96GPa strength) or must we use a tapered cable? How to design and, crucially, power and cool the climbers -- or will they be 'clingers' on a moving ribbon? But all of these things are engineering design choices, not impediments.
NASA has been active in funding and encouraging SE research, including several studies by NIAC (by Brad Edwards and Jerome Pearson in particular) and in promoting the Centennial Prizes for tether technologies.
Given the uncertainty in producing a suitable material, and despite my enthusiasm for SEs I believe that NASA should not yet commit any large budget to the SE, but continue its excellent efforts in promoting the idea through smaller means. It could, however, usefully commit additional funds to CNT research since any progress in high specific strength materials would benefit it even if this research does not result in material strengths useful for an SE.
Re:Where is that report? I couldn'y find it ...
on
Space Elevator Update
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· Score: 1
Actually the strength needed for an untapered ribbon isn't too bad: Blaise Gassend calculates it at 64GPa, which is only 1/3 of the strength of individuals CNTs.:)
Cheers, Andy.
>>Catastrophe. Yes Bad Things can happen. The amount of damage done is less than might be expected.
IS less? So this has been tested, has it?
Of course not, but physics allows us to make sensible predictions. Early elevators would mostly burn up on reentry, or break into pieces with all the lethality of snowflakes. Chemical poisoning issues from burning/powdering are a more valid concern, but reseach thus far indicates the risk is not great (forest fires produce the same stuff in larger quantity). Large elevators would be more of a direct kinetic threat, but are also much less likely to fail. Even very high capacity SEs are very long, but still only a meter or two in cross section.
>I'll tell you what I'd expect. I'd expect if something went wrong and a "load" plummeted to earth from 5km up it would be pretty difficult to predict what sort of damage it would do... There's one of many possible catastrophes we'd like to hear whay you'd expect the damage to be
Ever heard of parachutes?
>Terrorism. The thing is less a target than might be expected. Again, IS less? This fact comes from where? A poll of known terrorists, or off the top of your head?
I think people use present tense merely for convenience. Everyone knows there is no SE yet.
Only the bottom few km are accessible to terrorists (assuming one searches cargo/passengers carefully) and the SE would be easy to guard (being at sea), and hard to hit (1m x 1mm or less). There may well also be ways to mitigate a failure near ground level.
>Yes, I know... people were executed for suggesting that the world wasn't flat, etc etc... but please - if you want a rational discussion on this thing pushing "facts" like these at us is hardly likely to sway any opinion.
This is analysis, not facts. If it seems unreasonable to you, you should explain your own reasoning rather than bloviating.
Reposting my reply from an above posting -- this time with line breaks. Sorry about that.
Single point of failure: Dead wrong. The SE's greatest strength is that it enables rapid, cheap construction of ever larger more robust versions of itself. A feature that no other space access technology promises. All other system have to survive SPF problems forever.
Small benefits: Dead wrong, ubeliev. As mbrother pointed out, the energy cost of raising something to GEO via SE is quite small. In contrast, rockets wildly inefficient. An SE can also be engineered to be highly reliable (comparable to present day shipping or rail), whereas chemical rockets seem incapable of doing much better than 1 failure in 100 launches, no matter how much money and talent is expended on them.
All the investment is up front: True for the R&D phase, but how is this different from any other technology? The SE is unique in that the first one makes subsequent and larger ones dramatically cheaper. Given a 1T payload SE it only takes a year (I think) to erect at 10T payload one. Given a couple of these, making a 100T one is fast... and so on. SEs scale amazingly well -- in a way rockets and other aerodynamic devices never can.
Look folks, dozens of us in the SE 'community' have examined the SE concept from every angle we can think of, and many of us (not me) are professional physicists. While it's possible we have missed something, I wish people would give us a little credit for thinking through the obvious problems.
The points I try to make about the SE are:
1. Yes we need strong material (for Earth SEs anyway, aramids are possible for the moon) -- 64GPa is a nice target, so far only 10GPa seems imminent. Individual CNTs have been directly measured at 200GPa.
2. The SE will be much safer than any current technology, or any future one I have seen discussed. Vulnerable SEs don't comprise much mass; conversely heavy SEs are not very vulnerable. So mass * vulnerabilty stays low => safe. Also, contrary to uninformed opinion, complete SE cable failures are quite survivable for both passengers and bystanders.
3. The SE will scale exponentially -- much better than any existing or posited method I have seen. Million ton payload SEs? Given an appropriate material, not all that tough once the first one is in place.
Single point of failure: Dead wrong. The SE's greatest strength is that it enables rapid, cheap construction of ever larger more robust versions of itself. A feature that no other space access technology promises. All other system have to survive SPF problems forever.
Small benefits: Dead wrong. As mbrother pointed out, the energy cost of raising something to GEO via SE is quite small. In contrast, rockets wildly inefficient. An SE can also be engineered to be highly reliable (comparable to present day shipping or rail), whereas chemical rockets seem incapable of doing much better than 1 failure in 100 launches, no matter how much money and talent is expended on them.
All the investment is up front: True for the R&D phase, but how is this different from any other technology? The SE is unique in that the first one makes subsequent and larger ones dramatically cheaper. Given a 1T payload SE it only takes a year (I think) to erect at 10T payload one. Given a couple of these, making a 100T one is fast... and so on. SEs scale amazingly well -- in a way rockets and other aerodynamic devices never can.
Look folks: dozens of us in the SE 'community' have examined the SE concept from every angle we can think of, and many of us (not me) are professional physicists. While it's possible we have missed something, I wish people would give us a little credit for thinking through the obvious problems.
The points I try to make about the SE are:
1. Yes we need strong material (for Earth SEs anyway, aramids are possible for the moon) -- 64GPa is a nice target, so far only 10GPa seems imminent. Individual CNTs have been directly measured at 200GPa.
2. The SE will be much safer than any current technology, or any future one I have seen discussed. Vulnerable SEs don't comprise much mass; conversely heavy SEs are not very vulnerable. So mass * vulnerabilty stays low => safe. Also, contrary to uninformed opinion, complete SE cable failures are quite survivable for both passengers and bystanders.
3. The SE will scale exponentially -- much better than any existing or posited method I have seen. Million ton payload SEs? Given an appropriate material, not all that tough once the first one is in place.
Cheers,
Andy
The favored name at the third SE conference was 'Space Bridge'.
One of the more legitimate concerns about constructing an SE is ensuring that longitudinal tension waves do not wreak havoc with climbers and/or base stations. This is probably solvable, but needs to be attended to. If we do not then 'Yo-yo' might be all too apt.
Andy
I absolutely loved Unreal and UT.
UT2k3, Unreal 2 and UT2k4 were horrible for me.
Nice graphics, utterly stupid gamplay.
If you liked 2003, this game may appeal, otherwise a waste of d/l time. Call of Duty and ET are waay better, actually requiring some brain.
Just my 2c
I presented at the 2nd SE conference in Santa Fe last year, offering a different way of constructing it, but my comments apply to Dr Edwards' design too.
One of the best things about space elevators is that they are inherently much safer than any other method of reaching space. In fact once a couple of them are operating one can use the exponentially increasing payload capability to builds space elevators with any desired safety factor.
Slashdot Mirror
I recently researched buying an electric on-demand water heater for my own home. Such heaters consume around 10-20kW and can demand 100 amps of current, they are however very efficient (as someone else noted) and so there is little waste to squeeze out of the system (a few percent at most I expect). Using microwave generating magnetrons is likely to be less efficient imo, so it is very hard to see how this company can live up to its claims. Whether by microwave or resistive heating, the same amount of energy needs to get into the water, it is not at all like a food stove where microwave ovens are genuinely more efficient (less heat loss and only the item being cooked is heated, not the stove walls too). The reason I didn't purchase an on-demand heater is that the electric service in my house would have to be upgraded, at a cost of around $3000. A new water tank, with heater, cost $700. The microwave heater would also have this cost issue. A better way to save power (nationally) would be to have dual-band power pricing (as is done in the UK) where power used in off peak hours costs less than in peak hours -- in this case a storage tank is potentially MORE efficient than on-demand since it can shift demand to off-peak hours when there is unused capacity. In any event, I doubt that a properly insulated water tank actually loses much heat, the main advantage of on-demand is that there is a never-ending supply of hot water. Andy
Being an SE enthusiast and having presented at two of the SE conferences, perhaps I can provide some useful background.
The single greatest challenge to building an SE remains that of producing suitable material for its main structural element - the cable.
A practical Space Elevator requires a material of ultimate strength of at least 50 GPa. Individual nanotubes have been made with several times this strength, but no bulk material has approached it yet. Pure single walled carbon nanotube fibres of length 4mm or greater should produce a spun yarn with strength in excess of 100 GPa and such nanotubes have been produced in 40mm lengths, but not in useful quantities. Steel reaches 5 GPa, but has 4 or 5 times the density of CNTs and so only has a fortieth of the specific strength needed. Aramid fibres such as spectra, dyneema and kevlar come closer, but are only useful for lunar or martian SEs, not earth ones.
Almost all other issues, such as terrorism / securing the base station / wind / lightning / discharging the ionosphere / lunar and solar tidal effects / atomic oxygen erosion / radiation damage / collisions with the ISS / swarf infall / cyclic heating and cooling / broken ribbon fragments landing on people or damaging the environment etc. either turn out to be insignificant or are fairly easily solved with a little thought and effort.
The two problems that are harder to solve are: micrometeoroid impact and what has been called 'fratricide' -- where fragments from one SE failing hit other SEs. The likely solution to the micrometeoroid (mm) problem is to make the size and shape of the SE ribbon such that mms do not degrade its strength significantly during the lifetime of the SE. Fratricide is very hard to deal with and will require that ribbons be designed to be VERY unlikely to fail and that they incorporate ways to affect the paths of fragments.
Beyond these problems there remain numerous areas of investigation such as the fundamental 'mode' or shape of SE to use -- a single straight cable, or a loop, or a straight cable with pieces that are cut from the upper end. Will a material be available that will allow loops or constant-thickness cables (requires 96GPa strength) or must we use a tapered cable? How to design and, crucially, power and cool the climbers -- or will they be 'clingers' on a moving ribbon? But all of these things are engineering design choices, not impediments.
NASA has been active in funding and encouraging SE research, including several studies by NIAC (by Brad Edwards and Jerome Pearson in particular) and in promoting the Centennial Prizes for tether technologies.
Given the uncertainty in producing a suitable material, and despite my enthusiasm for SEs I believe that NASA should not yet commit any large budget to the SE, but continue its excellent efforts in promoting the idea through smaller means. It could, however, usefully commit additional funds to CNT research since any progress in high specific strength materials would benefit it even if this research does not result in material strengths useful for an SE.
Excellent! Thanks. :)
... at cleantechnano :)
Actually the strength needed for an untapered ribbon isn't too bad: Blaise Gassend calculates it at 64GPa, which is only 1/3 of the strength of individuals CNTs. :)
Cheers, Andy.
Given a stong enough material it seems quite achievable -- though not easy.
Cheers, Andy
>>Catastrophe. Yes Bad Things can happen. The amount of damage done is less than might be expected. IS less? So this has been tested, has it?
Of course not, but physics allows us to make sensible predictions. Early elevators would mostly burn up on reentry, or break into pieces with all the lethality of snowflakes. Chemical poisoning issues from burning/powdering are a more valid concern, but reseach thus far indicates the risk is not great (forest fires produce the same stuff in larger quantity). Large elevators would be more of a direct kinetic threat, but are also much less likely to fail. Even very high capacity SEs are very long, but still only a meter or two in cross section.
>I'll tell you what I'd expect. I'd expect if something went wrong and a "load" plummeted to earth from 5km up it would be pretty difficult to predict what sort of damage it would do... There's one of many possible catastrophes we'd like to hear whay you'd expect the damage to be
Ever heard of parachutes?
>Terrorism. The thing is less a target than might be expected. Again, IS less? This fact comes from where? A poll of known terrorists, or off the top of your head?
I think people use present tense merely for convenience. Everyone knows there is no SE yet.
Only the bottom few km are accessible to terrorists (assuming one searches cargo/passengers carefully) and the SE would be easy to guard (being at sea), and hard to hit (1m x 1mm or less). There may well also be ways to mitigate a failure near ground level.
>Yes, I know... people were executed for suggesting that the world wasn't flat, etc etc... but please - if you want a rational discussion on this thing pushing "facts" like these at us is hardly likely to sway any opinion.
This is analysis, not facts. If it seems unreasonable to you, you should explain your own reasoning rather than bloviating.
Cheers, Andy
Reposting my reply from an above posting -- this time with line breaks. Sorry about that.
... and so on. SEs scale amazingly well -- in a way rockets and other aerodynamic devices never can.
Single point of failure: Dead wrong. The SE's greatest strength is that it enables rapid, cheap construction of ever larger more robust versions of itself. A feature that no other space access technology promises. All other system have to survive SPF problems forever.
Small benefits: Dead wrong, ubeliev. As mbrother pointed out, the energy cost of raising something to GEO via SE is quite small. In contrast, rockets wildly inefficient. An SE can also be engineered to be highly reliable (comparable to present day shipping or rail), whereas chemical rockets seem incapable of doing much better than 1 failure in 100 launches, no matter how much money and talent is expended on them.
All the investment is up front: True for the R&D phase, but how is this different from any other technology? The SE is unique in that the first one makes subsequent and larger ones dramatically cheaper. Given a 1T payload SE it only takes a year (I think) to erect at 10T payload one. Given a couple of these, making a 100T one is fast
Look folks, dozens of us in the SE 'community' have examined the SE concept from every angle we can think of, and many of us (not me) are professional physicists. While it's possible we have missed something, I wish people would give us a little credit for thinking through the obvious problems.
The points I try to make about the SE are:
1. Yes we need strong material (for Earth SEs anyway, aramids are possible for the moon) -- 64GPa is a nice target, so far only 10GPa seems imminent. Individual CNTs have been directly measured at 200GPa.
2. The SE will be much safer than any current technology, or any future one I have seen discussed. Vulnerable SEs don't comprise much mass; conversely heavy SEs are not very vulnerable. So mass * vulnerabilty stays low => safe. Also, contrary to uninformed opinion, complete SE cable failures are quite survivable for both passengers and bystanders.
3. The SE will scale exponentially -- much better than any existing or posited method I have seen. Million ton payload SEs? Given an appropriate material, not all that tough once the first one is in place.
Cheers, Andy
Single point of failure: Dead wrong. The SE's greatest strength is that it enables rapid, cheap construction of ever larger more robust versions of itself. A feature that no other space access technology promises. All other system have to survive SPF problems forever. Small benefits: Dead wrong. As mbrother pointed out, the energy cost of raising something to GEO via SE is quite small. In contrast, rockets wildly inefficient. An SE can also be engineered to be highly reliable (comparable to present day shipping or rail), whereas chemical rockets seem incapable of doing much better than 1 failure in 100 launches, no matter how much money and talent is expended on them. All the investment is up front: True for the R&D phase, but how is this different from any other technology? The SE is unique in that the first one makes subsequent and larger ones dramatically cheaper. Given a 1T payload SE it only takes a year (I think) to erect at 10T payload one. Given a couple of these, making a 100T one is fast ... and so on. SEs scale amazingly well -- in a way rockets and other aerodynamic devices never can.
Look folks: dozens of us in the SE 'community' have examined the SE concept from every angle we can think of, and many of us (not me) are professional physicists. While it's possible we have missed something, I wish people would give us a little credit for thinking through the obvious problems.
The points I try to make about the SE are:
1. Yes we need strong material (for Earth SEs anyway, aramids are possible for the moon) -- 64GPa is a nice target, so far only 10GPa seems imminent. Individual CNTs have been directly measured at 200GPa.
2. The SE will be much safer than any current technology, or any future one I have seen discussed. Vulnerable SEs don't comprise much mass; conversely heavy SEs are not very vulnerable. So mass * vulnerabilty stays low => safe. Also, contrary to uninformed opinion, complete SE cable failures are quite survivable for both passengers and bystanders.
3. The SE will scale exponentially -- much better than any existing or posited method I have seen. Million ton payload SEs? Given an appropriate material, not all that tough once the first one is in place.
Cheers,
Andy
The favored name at the third SE conference was 'Space Bridge'. One of the more legitimate concerns about constructing an SE is ensuring that longitudinal tension waves do not wreak havoc with climbers and/or base stations. This is probably solvable, but needs to be attended to. If we do not then 'Yo-yo' might be all too apt. Andy
Actually, SWNTs can now be made with sufficient length -- 4mm is long enough, I believe, to braid them into thread/string/ropes.l ingParticiple.nsf/plinks/APRE-64TPER
The remaining problem is quantity.
See here: http://www.healthspace.ca/websites/staff/AJP/Dang
Cheers, Andy
I absolutely loved Unreal and UT. UT2k3, Unreal 2 and UT2k4 were horrible for me. Nice graphics, utterly stupid gamplay. If you liked 2003, this game may appeal, otherwise a waste of d/l time. Call of Duty and ET are waay better, actually requiring some brain. Just my 2c
I presented at the 2nd SE conference in Santa Fe last year, offering a different way of constructing it, but my comments apply to Dr Edwards' design too.
One of the best things about space elevators is that they are inherently much safer than any other method of reaching space. In fact once a couple of them are operating one can use the exponentially increasing payload capability to builds space elevators with any desired safety factor.
-- Andrew Price