Concentrated solar thermal gets much better performance than nuclear thermal because you're only limited by the materials properties of your heat exchanger, not your reactor fuel. The problem with solar thermal is three fold.
First, you have to be able to see the sun, so your burns are restricted to times where you're not in Earth's shadow. That could make transfer windows difficult to hit, of course if you have a thousand seconds or higher ISP, that's not such an issue.
Second, we're talking about high thrust rockets so you don't have astronauts sitting in the radiation belts for days as a low thrust rocket spirals out. That means you're going to have to have significant structure to support that concentrator, and it's no longer going to be very lightweight. Of course with such a high ISP, this may no longer be such an issue.
Third, this reflector cannot simply be static. It needs to be able to articulate to whatever angle you need to thrust, which greatly increases the complexity and mass of such a system.
But if you want to move great masses you'll need something more powerful.
No one here has actually made an argument about why they can't be scaled up, but just waved their hands and said "Nope."
No one has ever said they can't be scaled up. The problem is one of electrical power. ISP is directly proportional to exhaust velocity. While high ISP means high propellant efficiency, it also means low power efficiency. 200kW fed into a moderately high ISP NTR is going to offer much more thrust than a very high ISP ion drive. On top of that, the NTR uses the thermal output of the reactor directly, while the ion drive is going to suffer huge losses first converting that to electrical.
Now wait a minute. I thought BMW had hardpoints on the side of their vehicles, and a special jack that fit those hardpoints, specifically to make it easier to jack up.
You've still got a fairly expensive asset sitting idle.
Perhaps, but look outside any active distribution center and you'll find acres of idle trailers. I know Walmart even uses them as long term storage.
Then there's the extra labour to move one box at a time
If you're already moving one box at a time, because you're building the pallet, you may as well move one box at a time directly into the container. That was the whole point I was trying to make. There is no extra labor. The container itself is the unit of transport, rather than the pallet.
with ladders. You might be eight feet tall, but most people aren't.
My visibility may be skewed for only facilities with conveyor systems, but every high volume distribution center I've seen either does fluid loading, is in the process of transitioning to fluid loading, or is seriously considering fluid loading, rather than pallet loading.
You can unload 3,000 cases of palletised goods far faster than two or three people stuck in the back of a semi-trailer can put them on a conveyer belt. It takes a warehouse 20 minutes to unload a full 26 pallet load semi-trailer, it takes 2hrs to unload 1500 cases on a conveyer belt.
That's only relevant if the driver and truck has to stay with the trailer. In a major distribution network where it's the same company on both ends, that does not apply.
Sure, pallets take some vertical space, but the amount of space taken is small compared to the ability for one person to move close to two tons of cargo single-handedly across smooth floors with no more than a jack.
That requires one person and one hand truck or fork lift to shuttle each pallet of two tons of cargo back and forth. It's cheap, but it's very low throughput, and it doesn't scale up to high throughput well. If you need high throughput, you're going to use conveyor. You use pallets for storage, for items that cannot be conveyed, or for things like LTL receiving where you can't keep the trailer, and don't want to hold up the driver while you hand unload.
Re:Feed 8 million GI, what about USSR?
on
The Magic of Pallets
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· Score: 4, Insightful
They were defending their own country, rather than on the other side of an ocean.
It takes time to build pallets. It takes time to break apart, resort, and rebuild pallets. It costs money to repair and replace the pallets themselves. Pallets require extra ceiling space to actually pick them up and put them into a truck or container, resulting in wasted volume in that truck or container. The logistics industry is quickly moving away from pallets for everything but long term storage.
Ideally, nothing. Groups are already investigating the use of cavitators along the hull to reduce surface friction and fuel consumption. If that pans out, this would basically be a bonus effect.
There's no reason biological organisms cannot have an indefinite lifespan. Stasis would only be necessary for the purposes of reducing energy consumption and preventing boredom, which would both be issues in a machine intelligence.
Branson has a track record of seriously underestimating the difficulty of the challenges he picks. Plus he seems to believe he can replicate serious engineering achievements - eg space flight - on a shoestring budget.
You're overestimating the capability of SpaceShipOne/Two. It goes to space for all of a couple minutes. It does not go to orbit. The engineering requirements aren't nearly as tough. We've been sending unmanned vehicles up there since the early 40's, and manned ones up since the late 50's, back when NASA was still called NACA.
The Apollo program cost ~$20B, over the better part of a decade, during a time when the US GDP was rose from around $600B to $1T. So, it used roughly 0.3% of the GDP over that time period.
There's even a type of energy storage system you can make with superconductors - one of the highest power density and efficiency energy storage methods known to man.
The ultimate capacity of one of these systems is on the par with supercapacitors, and an order of magnitude lower than traditional chemical batteries. Their high power, low capacity, and functionally unlimited cycle life make them useful as a transient power filter, rather than a meaningful energy storage mechanism. Their sudden and nearly instantaneous quench makes them downright frightening as a sizable energy storage mechanism.
You're suggesting that instead of giving it some simple sensors and a radio, we task a satellite capable of real-time spectrographic imaging with sub-decimeter resolution in order to spot the changes in color of some oversized flying test strip?
This site is based in the US. Therefore, the convention it follows should be that of the US. Any use of a comma as a decimal delimiter here is simply wrong.
Besides that, the use of six digits when only two or maybe three are actually significant is just clumsy.
Like I use energy to lift a stone, and I get 100% of that energy back if the stone drops.
No body is fully elastic. You will have infinitesimally small energy losses due to changing internal stresses in the two bodies. You get very very close to 100% recovery, but not 100% recovery. The energy is still there. It hasn't escaped your hypothetical closed system. It is simply not recoverable in a useful form. It is disordered. Reversible processes are those "special cases".
Those numbers already take into account the difference in traffic volume. An individual loaded tractor trailer causes several thousand times the damage as a single sedan. In other words, there would have to be 80x the volume of passenger traffic on the road to cause the same amount of damage as present truck traffic.
Doesn't matter much, it's the same people that drive their cars that also buy supplies that require trucking.
So what? You're artificially buoying up industries that perhaps shouldn't be. Nearly all of our shipping is done over the road, due to cost and convenience. Make roadway shipping pay to repair its fair share of damage done to the roadway. Initially, shipping costs will rise. Costs for all products would rise across the board as those increased operating costs trickle down to consumers. Over time, those companies will find new ways to reduce costs. Money would be pumped into the rail system, expanding and modernizing it to improve speed and throughput. Manufacturing would become more regionally diverse so less has to be shipped across the country. Fewer vehicles on the road means lower traffic congestion. Less roadway maintenance further means lower traffic congestion. Locomotives are more efficient per unit of shipped material are more easily managed in terms of emissions. Fixed, limited access railways can be more easily converted to electric.
The trucking industry would suffer, unquestionably, but it's a much more complicated issue than you give it credit for, and perhaps the advantages in other areas outweigh those effects.
Slashdot Mirror
What do you think a "solar-electric" drive would be?
Concentrated solar thermal gets much better performance than nuclear thermal because you're only limited by the materials properties of your heat exchanger, not your reactor fuel. The problem with solar thermal is three fold.
First, you have to be able to see the sun, so your burns are restricted to times where you're not in Earth's shadow. That could make transfer windows difficult to hit, of course if you have a thousand seconds or higher ISP, that's not such an issue.
Second, we're talking about high thrust rockets so you don't have astronauts sitting in the radiation belts for days as a low thrust rocket spirals out. That means you're going to have to have significant structure to support that concentrator, and it's no longer going to be very lightweight. Of course with such a high ISP, this may no longer be such an issue.
Third, this reflector cannot simply be static. It needs to be able to articulate to whatever angle you need to thrust, which greatly increases the complexity and mass of such a system.
But if you want to move great masses you'll need something more powerful.
No one here has actually made an argument about why they can't be scaled up, but just waved their hands and said "Nope."
No one has ever said they can't be scaled up. The problem is one of electrical power. ISP is directly proportional to exhaust velocity. While high ISP means high propellant efficiency, it also means low power efficiency. 200kW fed into a moderately high ISP NTR is going to offer much more thrust than a very high ISP ion drive. On top of that, the NTR uses the thermal output of the reactor directly, while the ion drive is going to suffer huge losses first converting that to electrical.
Now wait a minute. I thought BMW had hardpoints on the side of their vehicles, and a special jack that fit those hardpoints, specifically to make it easier to jack up.
You've still got a fairly expensive asset sitting idle.
Perhaps, but look outside any active distribution center and you'll find acres of idle trailers. I know Walmart even uses them as long term storage.
Then there's the extra labour to move one box at a time
If you're already moving one box at a time, because you're building the pallet, you may as well move one box at a time directly into the container. That was the whole point I was trying to make. There is no extra labor. The container itself is the unit of transport, rather than the pallet.
with ladders. You might be eight feet tall, but most people aren't.
Large molded plastic step stools, actually.
My visibility may be skewed for only facilities with conveyor systems, but every high volume distribution center I've seen either does fluid loading, is in the process of transitioning to fluid loading, or is seriously considering fluid loading, rather than pallet loading.
... two trips over one,
Unless the previous trailer just waits around until the next one is dropped off.
And where is this happening?
Anywhere you're shipping freight between two of your own facilities.
You can unload 3,000 cases of palletised goods far faster than two or three people stuck in the back of a semi-trailer can put them on a conveyer belt. It takes a warehouse 20 minutes to unload a full 26 pallet load semi-trailer, it takes 2hrs to unload 1500 cases on a conveyer belt.
That's only relevant if the driver and truck has to stay with the trailer. In a major distribution network where it's the same company on both ends, that does not apply.
Sure, pallets take some vertical space, but the amount of space taken is small compared to the ability for one person to move close to two tons of cargo single-handedly across smooth floors with no more than a jack.
That requires one person and one hand truck or fork lift to shuttle each pallet of two tons of cargo back and forth. It's cheap, but it's very low throughput, and it doesn't scale up to high throughput well. If you need high throughput, you're going to use conveyor. You use pallets for storage, for items that cannot be conveyed, or for things like LTL receiving where you can't keep the trailer, and don't want to hold up the driver while you hand unload.
They were defending their own country, rather than on the other side of an ocean.
It takes time to build pallets. It takes time to break apart, resort, and rebuild pallets. It costs money to repair and replace the pallets themselves. Pallets require extra ceiling space to actually pick them up and put them into a truck or container, resulting in wasted volume in that truck or container. The logistics industry is quickly moving away from pallets for everything but long term storage.
Just make sure they're not chemically treated before tossing them in the fire.
Ideally, nothing. Groups are already investigating the use of cavitators along the hull to reduce surface friction and fuel consumption. If that pans out, this would basically be a bonus effect.
There's no reason biological organisms cannot have an indefinite lifespan. Stasis would only be necessary for the purposes of reducing energy consumption and preventing boredom, which would both be issues in a machine intelligence.
Branson has a track record of seriously underestimating the difficulty of the challenges he picks. Plus he seems to believe he can replicate serious engineering achievements - eg space flight - on a shoestring budget.
You're overestimating the capability of SpaceShipOne/Two. It goes to space for all of a couple minutes. It does not go to orbit. The engineering requirements aren't nearly as tough. We've been sending unmanned vehicles up there since the early 40's, and manned ones up since the late 50's, back when NASA was still called NACA.
The Apollo programme was 4% of GDP, by itself
The Apollo program cost ~$20B, over the better part of a decade, during a time when the US GDP was rose from around $600B to $1T. So, it used roughly 0.3% of the GDP over that time period.
There's even a type of energy storage system you can make with superconductors - one of the highest power density and efficiency energy storage methods known to man.
The ultimate capacity of one of these systems is on the par with supercapacitors, and an order of magnitude lower than traditional chemical batteries. Their high power, low capacity, and functionally unlimited cycle life make them useful as a transient power filter, rather than a meaningful energy storage mechanism. Their sudden and nearly instantaneous quench makes them downright frightening as a sizable energy storage mechanism.
You're suggesting that instead of giving it some simple sensors and a radio, we task a satellite capable of real-time spectrographic imaging with sub-decimeter resolution in order to spot the changes in color of some oversized flying test strip?
This site is based in the US. Therefore, the convention it follows should be that of the US. Any use of a comma as a decimal delimiter here is simply wrong.
Besides that, the use of six digits when only two or maybe three are actually significant is just clumsy.
Except those things mostly have real airfoils, and don't need such a high TWR to plow through the air like the flat plate in the article.
Like I use energy to lift a stone, and I get 100% of that energy back if the stone drops.
No body is fully elastic. You will have infinitesimally small energy losses due to changing internal stresses in the two bodies. You get very very close to 100% recovery, but not 100% recovery. The energy is still there. It hasn't escaped your hypothetical closed system. It is simply not recoverable in a useful form. It is disordered. Reversible processes are those "special cases".
Of course doing so has the side effect that no one will give you loans because your currency is too unstable to be of any international value.
Those numbers already take into account the difference in traffic volume. An individual loaded tractor trailer causes several thousand times the damage as a single sedan. In other words, there would have to be 80x the volume of passenger traffic on the road to cause the same amount of damage as present truck traffic.
Doesn't matter much, it's the same people that drive their cars that also buy supplies that require trucking.
So what? You're artificially buoying up industries that perhaps shouldn't be. Nearly all of our shipping is done over the road, due to cost and convenience. Make roadway shipping pay to repair its fair share of damage done to the roadway. Initially, shipping costs will rise. Costs for all products would rise across the board as those increased operating costs trickle down to consumers. Over time, those companies will find new ways to reduce costs. Money would be pumped into the rail system, expanding and modernizing it to improve speed and throughput. Manufacturing would become more regionally diverse so less has to be shipped across the country. Fewer vehicles on the road means lower traffic congestion. Less roadway maintenance further means lower traffic congestion. Locomotives are more efficient per unit of shipped material are more easily managed in terms of emissions. Fixed, limited access railways can be more easily converted to electric.
The trucking industry would suffer, unquestionably, but it's a much more complicated issue than you give it credit for, and perhaps the advantages in other areas outweigh those effects.