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strangequark
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« Reply #15 on: 04/24/2012 07:49 PM » |
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What is problem with pressure ? Is this type of hydrogen under too much pressure that it is a safety problem?
Have they done this in science lab ?
And how much cheaper with this be than what they are using now ?
There's no way of sustaining that large a pressure for any sizable amount of propellant. They can get something like a microliter of hydrogen to metallize when compressed between two smooth facets of a diamond under immensely concentrated force. This is the Diamond Anvil Cell that's been previously referenced. It's not even that it's a safety problem. It's that there is nothing that can hold a substance at that pressure except a DAC. If we had some super-tank that could handle this pressure, then pressurized water alone would get you an Isp of 2000 seconds.
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aquanaut99
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« Reply #16 on: 04/24/2012 07:50 PM » |
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What is problem with pressure ? Is this type of hydrogen under too much pressure that it is a safety problem?
To put it into perspective: 330 to 360 Gigapascals is the pressure inside Earth's Inner Core. That's the kind of pressure we are talking about here. We'd have to be able to contain that in a rocket fuel tank... And the resulting fuel would burn hotter than the surface of the sun... This is way beyond our current and future technical ability to control. Also, I seriously doubt metallic hydrogen, even if feasible, could ever be produced in sufficient quantities and at a reasonable price. More likely, it is going to cost about as much to creat 1 mg of MH as it would cost to create 1 mg of anti-matter. And, in which case, we'd be better off going directly with anti-matter, which is only slightly more dangerous...
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Downix
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« Reply #17 on: 04/24/2012 08:01 PM » |
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It's probably easier to fuse hydrogen protons together with a device built in your garage to generate fusion energy than it is to compress
large numbers of hydrogen atoms to form a (questionably) stable solid form for hardware purposes.
Um, *pst*, it *is* easy to fuse hydrogen protons together with a device built in your garage: http://www.fusor.net
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93143
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« Reply #18 on: 04/24/2012 08:31 PM » |
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Say you want to build the pressure vessel to contain this 200 GPa pressure out of carbon fiber that has a maximum stress of 6.3 GPa (just going off of a wikipedia table for the fiber only, the actual laid up material would be weaker). In order to keep material stresses below yield in a tank with a diameter of 5 m, you'd need a tank 6.25 cm thick. You've done that wrong. For a 5 m spherical pressure vessel, using the thin-walled assumption, keeping the hoop stress below 6.3 GPa requires a wall thickness of 40 m. Of course, that's not strictly accurate, since the calculation assumes that the wall thickness is much less than the tank radius... but it gives you an idea.
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nec207
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« Reply #19 on: 04/24/2012 10:08 PM » |
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What is problem with pressure ? Is this type of hydrogen under too much pressure that it is a safety problem?
To put it into perspective: 330 to 360 Gigapascals is the pressure inside Earth's Inner Core. That's the kind of pressure we are talking about here. We'd have to be able to contain that in a rocket fuel tank... And the resulting fuel would burn hotter than the surface of the sun...
This is way beyond our current and future technical ability to control. Also, I seriously doubt metallic hydrogen, even if feasible, could ever be produced in sufficient quantities and at a reasonable price. More likely, it is going to cost about as much to creat 1 mg of MH as it would cost to create 1 mg of anti-matter. And, in which case, we'd be better off going directly with anti-matter, which is only slightly more dangerous...
Anti-matter is very costly to make and hard to control. That is why I think they are looking at this it is much cheaper. But like other people here say on big scale it is hard to do .
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strangequark
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« Reply #20 on: 04/24/2012 10:27 PM » |
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To put it into perspective: 330 to 360 Gigapascals is the pressure inside Earth's Inner Core. That's the kind of pressure we are talking about here. We'd have to be able to contain that in a rocket fuel tank... And the resulting fuel would burn hotter than the surface of the sun...
This is way beyond our current and future technical ability to control. Also, I seriously doubt metallic hydrogen, even if feasible, could ever be produced in sufficient quantities and at a reasonable price. More likely, it is going to cost about as much to creat 1 mg of MH as it would cost to create 1 mg of anti-matter. And, in which case, we'd be better off going directly with anti-matter, which is only slightly more dangerous...
Anti-matter is very costly to make and hard to control. That is why I think they are looking at this it is much cheaper.
But like other people here say on big scale it is hard to do .
His point was that metallic hydrogen would likely be as costly to make, and as hard to control. My professional opinion is that it would be harder to control metallic hydrogen. As for estimating cost at this juncture for either "technology": At best, it's like Goddard debating the relative merits of using iridium-coated rhenium versus disilicide coated niobium for combustion chambers. At worst, it's debating whether you can fit more dancing seraphims or cherabims on the surface of a pin.
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8900
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« Reply #21 on: 04/26/2012 03:37 PM » |
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What is problem with pressure ? Is this type of hydrogen under too much pressure that it is a safety problem? 200 GigaPascal's is 29 million pounds per square inch.
Have they done this in science lab ? Yes. But the equipment is relatively heavy (and small scale), and controlled extraction of energy at those pressures (in this context) hasn't been done (to my knowledge).
How about laser confinement?
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kkattula
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« Reply #22 on: 04/26/2012 04:08 PM » |
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To put things in perspective:
Pump-fed rocket tanks (light) = 50 to 100 PSI
Pressure-fed rocket tanks (heavy) = 300 to 1000 PSI
Rocket turbo pumps = 600 to 3000 PSI
Metallic Hydrogen tank (impossibly heavy) = 30000000 to 45000000 PSI
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aero
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« Reply #23 on: 04/26/2012 05:42 PM » |
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To put things in perspective:
Pump-fed rocket tanks (light) = 50 to 100 PSI
Pressure-fed rocket tanks (heavy) = 300 to 1000 PSI
Rocket turbo pumps = 600 to 3000 PSI
Metallic Hydrogen tank (impossibly heavy) = 30000000 to 45000000 PSI
compare that to the theoritical maximum tensile strength of the strongest material known, multiwall carbon nanotubes, 43 511 321.402 pound/square inch. Current laboratory tests are a long way from reaching the theoritical maximum with the highest strength measured to date being 9 137 377.494 5 pound/square inch
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nec207
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« Reply #24 on: 04/30/2012 10:27 PM » |
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To put it into perspective: 330 to 360 Gigapascals is the pressure inside Earth's Inner Core. That's the kind of pressure we are talking about here. We'd have to be able to contain that in a rocket fuel tank... And the resulting fuel would burn hotter than the surface of the sun...
This is way beyond our current and future technical ability to control. Also, I seriously doubt metallic hydrogen, even if feasible, could ever be produced in sufficient quantities and at a reasonable price. More likely, it is going to cost about as much to creat 1 mg of MH as it would cost to create 1 mg of anti-matter. And, in which case, we'd be better off going directly with anti-matter, which is only slightly more dangerous...
Anti-matter is very costly to make and hard to control. That is why I think they are looking at this it is much cheaper.
But like other people here say on big scale it is hard to do .
His point was that metallic hydrogen would likely be as costly to make, and as hard to control.
My professional opinion is that it would be harder to control metallic hydrogen.
As for estimating cost at this juncture for either "technology":
At best, it's like Goddard debating the relative merits of using iridium-coated rhenium versus disilicide coated niobium for combustion chambers.
At worst, it's debating whether you can fit more dancing seraphims or cherabims on the surface of a pin.
So in other words it is a sensational news article ( to give feel to public some thing found ) and the part saying bring space cost down is so very wrong.. It is the other way around not bring space cost down but make it very very very costly !!! Thay need to say that than this sensational news article .
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93143
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« Reply #25 on: 04/30/2012 10:46 PM » |
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It is the other way around not bring space cost down but make it very very very costly !!! No. This is something we can't do at all. Cost doesn't factor into it. If we eventually figure out how to use metallic hydrogen as propellant, it might turn out to be cheaper than modern chemical rockets, or whatever we're using by then. Or it might not. More importantly, we may not ever figure out how to do it - there may not be a way.
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JohnFornaro
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« Reply #26 on: 05/01/2012 03:37 PM » |
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It is the other way around not bring space cost down but make it very very very costly !!!
No. This is something we can't do at all. Cost doesn't factor into it.
If we eventually figure out how to use metallic hydrogen as propellant, it might turn out to be cheaper than modern chemical rockets, or whatever we're using by then. Or it might not.
More importantly, we may not ever figure out how to do it - there may not be a way.
+1 No holy grails of any near term utility have yet been found in this exotic propulsion technology.
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simonbp
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« Reply #28 on: 02/04/2013 12:34 AM » |
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For practical applications however (not only rocket fuel) it must prove to be metastable.
Which is the point that most of the commentators so far have missed. Noone is ever going to use metallic hydrogen if it doesn't prove to have a metastable state: a high-density phase of matter that is triggered by super-high pressure (the 200 GPa), but which is stable at lower pressures (>5 MPa). Quantum theory predicts that it should be there, but it's been so far hard to experimentally prove it. It's important not simply for exotic propulsion, but also understanding the interior of Jupiter, which is mostly metallic hydrogen by mass. So, even if the metastable state does not exist, this is still good science to do.
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IRobot
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« Reply #29 on: 02/04/2013 12:50 AM » |
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Considering the current testing process, I'm not sure they can make it cheap in large quantities, so achieving metastability might not be enough. Quantum theory predicts that it should be there, but it's been so far hard to experimentally prove it.
Quantum theory is a tool, there are limits for what it can predict. It does not explain how the universe works, it just gives some results that fit some observations, just like Newtonian physics.
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