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Old 2011-09-28, 16:35   Link #161
JMvS
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Originally Posted by Jinto View Post
The most ridiculous idea of the whole concept is the part about nuclear shaped charges. Usually a shaped charge is a charge that is specifically directed and channeled in a certain direction. Shaped charge explosives are used to cut through armor (military) or other stuff like e.g. reinforced concrete (demolition).

However, the idea to shape charge a plasma is just... well okay... the problem is not that it is impossible... the problem is, that it is impossible when at the same time, the nuclear device shall have a good efficiency (the whole point of this project). If you want a nuclear device to detonate most efficiently, then you have to keep the fission material as long as possible in a state of a critical mass that is fissioning. Typically you'ld use a strong container (lots of high strength steel) to confine the fission material. However, the longer - and hence more efficiently - the fission material converts mass into energy, the more energy is released... to the point where the enclosing device entirely vaporates. Whats left then is a plasma. Now to shape charge the plasma you'ld need something that can either reflect/channel the plasma or something else that becomes the charge and is propelled by the plasma. Both principles of shape charging won't work, because there simply is no material that remains stable long enough (before it turns into plasma) to either shape the plasma or being shaped and propelled by the plasma. Additionally that device would be rather weak in space... in the earth's atmosphere a thermonuclear bomb (as its name implies) creates a lot of heat... so much that thermobaric shockwaves are created (when surrounded by air). I think in space most of this heat energy could not even be converted into propulsion because there is no thermobaric effect.
Err, given that at the time the program had some of the top physicists working on it, some which would have been working on nuclear weapon designs, I wouldn't say that this was a ridiculous concept. As most advanced weapon designs precisely had to do with controlling/channeling explosions and plasma flows, be them conventional or nuclear, as in multi-staged fusion devices.


The whole point of the shaped charge design was to add inert reaction mass around the nuclear device, shaped in order to maximise propulsion efficiency.
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Old 2011-09-28, 17:42   Link #162
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Originally Posted by JMvS View Post
Err, given that at the time the program had some of the top physicists working on it, some which would have been working on nuclear weapon designs, I wouldn't say that this was a ridiculous concept. As most advanced weapon designs precisely had to do with controlling/channeling explosions and plasma flows, be them conventional or nuclear, as in multi-staged fusion devices.
Multistage is just a problem of shooting the right stuff at the right time at each other. Nothing like nuclear shape charges actually.

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Originally Posted by JMvS View Post
The whole point of the shaped charge design was to add inert reaction mass around the nuclear device, shaped in order to maximise propulsion efficiency.
Hm, maybe you miss something here... a thermonuclear device creates first and foremost heat and not pressure. The pressure is an indirect result of stuff that is expanding because of the tremendous heat. If you want to burn the nuclear fuel very efficiently/clean you have to burn it as hot as possible. The problem is, that inert mass needs to withstand the heat of the plasma. Even if the inert mass was large enough - so that not all of it was turned into plasma almost immediatly (and which can hardly be directed once it turned into plasma) it would be just too heavy to be carried as "propellant". The plasma will expand rather evenly in all directions (at least in vacuum and zero gravity). So increasing the power output of the charge when keeping the mass constant, means to lose the shaping effect.
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Old 2011-09-28, 18:57   Link #163
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Originally Posted by Jinto View Post
Multistage is just a problem of shooting the right stuff at the right time at each other. Nothing like nuclear shape charges actually.
Multistage is all about focusing shockwaves, neutrons and X-rays, within the volume of the nuclear device, within what is almost an instant, to maximise the output of the device prior to it bein vaporized.

Things that were devised by the very same breed of scientist that those who worked on the Orion project.

Quote:
Hm, maybe you miss something here... a thermonuclear device creates first and foremost heat and not pressure. The pressure is an indirect result of stuff that is expanding because of the tremendous heat. If you want to burn the nuclear fuel very efficiently/clean you have to burn it as hot as possible. The problem is, that inert mass needs to withstand the heat of the plasma. Even if the inert mass was large enough - so that not all of it was turned into plasma almost immediatly (and which can hardly be directed once it turned into plasma) it would be just too heavy to be carried as "propellant". The plasma will expand rather evenly in all directions (at least in vacuum and zero gravity). So increasing the power output of the charge when keeping the mass constant, means to lose the shaping effect.
I am well aware of what a nuclear device produce:
-radiations, ranging over the whole electromagnetic spectrum and further, and which distribution (IR, X-rays, neutrons) are tinkered with in multiple weapon designs.
-pressure: the shockwave propagated in an atmospheric, liquid or solid environment by the expansion of the bomb's vaporized mass.

Now, if a multistage nuclear device can hold itself during the preliminary explosions, why would't a reaction mass, shaped appropriately, fare similarly?

I refer you to the wikipedia entry:

Quote:
The shape of the bomb's reaction mass is critical to efficiency. The original project designed bombs with a reaction mass made of tungsten. The bomb's geometry and materials focused the X-rays and plasma from the core of nuclear explosive to hit the reaction mass (as in a multistage where X-rays and plasma are focused on specific points of the whole device to achieve the sought results). In effect each bomb would be a nuclear shaped charge.

A bomb with a cylinder of reaction mass expands into a flat, disk-shaped wave of plasma when it explodes. A bomb with a disk-shaped reaction mass expands into a far more efficient cigar-shaped wave of plasma debris. The cigar shape focuses much of the plasma to impinge onto the pusher-plate.
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Old 2011-09-29, 01:41   Link #164
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Quote:
Originally Posted by JMvS View Post
Multistage is all about focusing shockwaves, neutrons and X-rays, within the volume of the nuclear device, within what is almost an instant, to maximise the output of the device prior to it bein vaporized.

Things that were devised by the very same breed of scientist that those who worked on the Orion project.

I am well aware of what a nuclear device produce:
-radiations, ranging over the whole electromagnetic spectrum and further, and which distribution (IR, X-rays, neutrons) are tinkered with in multiple weapon designs.
-pressure: the shockwave propagated in an atmospheric, liquid or solid environment by the expansion of the bomb's vaporized mass.

Now, if a multistage nuclear device can hold itself during the preliminary explosions, why would't a reaction mass, shaped appropriately, fare similarly?

I refer you to the wikipedia entry:
Okay, point taken... you can actually shape charge the nuclear fuel prior to vaporizing wich affects its shape when it is vaporizing/reacting.

This however is more important for the way the fuel reacts internally. The result is the same, at the end the wohle device is vaporized.

The heat/radiation (most of the radiation is transformed into heat because of particle interaction) will be way more significant then the actual shockwave created. So, since there is only a plasma shockwave, most of the energy of the explosion will be wasted in heat. If the device does not burn that clean, there would be more non-plasma matter in the shockwave, when those hit the absorbers it might actually provide more porpulsion even though the nuclear fuel is used less efficiently. However, in order to reduce the percentage of isotopes with longer half life times in the fallout you'ld try to burn the nucelar fuel as efficient as possible.

Shaped thin plasma is imo inefficient for propulsion (especially in space). The effect of a thermonuclear device in space is primarily heat/radiation generation, there is no medium to transport shockwaves other than the selfgenerated plasma, that thins out rapidly when it is dispenses over a vast area. The thermobaric effect that adds to the plasma shockwave when the device is used in an atmosphere (air expands rapidly because of the vast/sudden heating) won't work in space.

I mentioned in my first post about this, that it is not impossible to design such a shaped charge that can be used for propulsion... what I tried to say is that you cannot make it very clean/efficient because that would actually reduce the propulsion. To use dirty/inefficient shaped charges that generates lots of dangerous fallout would be good for propulsion and hence is ridiculous.

And the part about the shaped reaction mass in the wikipedia article is just theory. The reaction mass that stays stable long enough to be shaped like that (Hohlladung) doesn't exist when the device is burning very clean/hot/efficient. It does exist when the device is rather dirty.

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Old 2011-09-29, 08:07   Link #165
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Quote:
Originally Posted by Jinto View Post
Okay, point taken... you can actually shape charge the nuclear fuel prior to vaporizing wich affects its shape when it is vaporizing/reacting.

This however is more important for the way the fuel reacts internally. The result is the same, at the end the wohle device is vaporized.

The heat/radiation (most of the radiation is transformed into heat because of particle interaction) will be way more significant then the actual shockwave created. So, since there is only a plasma shockwave, most of the energy of the explosion will be wasted in heat. If the device does not burn that clean, there would be more non-plasma matter in the shockwave, when those hit the absorbers it might actually provide more porpulsion even though the nuclear fuel is used less efficiently. However, in order to reduce the percentage of isotopes with longer half life times in the fallout you'ld try to burn the nucelar fuel as efficient as possible.

Shaped thin plasma is imo inefficient for propulsion (especially in space). The effect of a thermonuclear device in space is primarily heat/radiation generation, there is no medium to transport shockwaves other than the selfgenerated plasma, that thins out rapidly when it is dispenses over a vast area. The thermobaric effect that adds to the plasma shockwave when the device is used in an atmosphere (air expands rapidly because of the vast/sudden heating) won't work in space.

I mentioned in my first post about this, that it is not impossible to design such a shaped charge that can be used for propulsion... what I tried to say is that you cannot make it very clean/efficient because that would actually reduce the propulsion. To use dirty/inefficient shaped charges that generates lots of dangerous fallout would be good for propulsion and hence is ridiculous.

And the part about the shaped reaction mass in the wikipedia article is just theory. The reaction mass that stays stable long enough to be shaped like that (Hohlladung) doesn't exist when the device is burning very clean/hot/efficient. It does exist when the device is rather dirty.
Ahh I think I understand where your concern is. But the whole point of the design is not that all the output of the bomb will be used for propulsion, but that the output is anyway so massive, compared to alternative, that it is much much more efficient compared to conventional rockets or ion propulsion, as long as high thrust and high specific impulse are seeked.

The point of the orion design is that of a pulsed reaction propulsion: the bombs would be launched at very short intervals, exploding at very short range behind the pusher plate.

And actually, the smallest yields achievable were sought after, in order to increase their frequency.

Quote:
The smaller the bomb, the smaller each impulse will be, so the higher the rate of impulses and more than will be needed to achieve orbit. Smaller impulses also mean less g shock on the pusher plate and less need for damping to smooth out the acceleration.

The optimal Orion drive bomblet yield (for the human crewed 4,000 ton reference design) was calculated to be in the region of 0.15 KT, with approx 800 bombs needed to orbit and a bomb rate of approx 1 per second.

[...]

In late 1958 / early 1959, it was realized that the smallest practical vehicle would be determined by the smallest achievable bomb yield. The use of 0.03 kT (sea-level yield) bombs would give vehicle mass of 880 tons. However, this was regarded as too small for anything other than an orbital test vehicle and the team soon focused on a 4,000 ton "base design".
Moreso, technical solutions were proposed to minimize fallout:

Quote:
Most of the three thousand tonnes of each of the "super" Orion's propulsion units would be inert material such as polyethylene, or boron salts, used to transmit the force of the propulsion units detonation to the Orion's pusher plate, and absorb neutrons to minimize fallout. One design proposed by Freeman Dyson for the "Super Orion" called for the pusher plate to be composed primarily of uranium or a transuranic element so that upon reaching a nearby star system the plate could be converted to nuclear fuel.
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Old 2011-09-29, 08:12   Link #166
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Originally Posted by Jinto View Post
Okay, point taken... you can actually shape charge the nuclear fuel prior to vaporizing wich affects its shape when it is vaporizing/reacting.
There was a lot of research at Los Alamos in the 80s about shaped nuclear weapons for use as "super bunker busters" to take out hardened missiles bunkers, etc. Some of it was unclassified and made its way into journals like Scientific American and some industry journals. At the time, I took it as more "Dr. Strangelove" style lunacy common at the time... but I never thought about the idea being used in relation to the ORION project. I'm still not sure the mechanical engineers wouldn't laugh their heads off at the technical requirements for a "firing plate" where the bombs would be ignited.

But there was a "request for proposal" sent out in the 80s for "a spherical device with sensors that could contain explosive pressures of <insert values for something equaling nuclear blast here>" --- reading the RFP, it was easy to see they were wanting something that would let them circumvent the air and underground testing bans.
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Old 2011-09-29, 09:53   Link #167
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Originally Posted by Vexx View Post
There was a lot of research at Los Alamos in the 80s about shaped nuclear weapons for use as "super bunker busters" to take out hardened missiles bunkers, etc. Some of it was unclassified and made its way into journals like Scientific American and some industry journals. At the time, I took it as more "Dr. Strangelove" style lunacy common at the time... but I never thought about the idea being used in relation to the ORION project. I'm still not sure the mechanical engineers wouldn't laugh their heads off at the technical requirements for a "firing plate" where the bombs would be ignited.

But there was a "request for proposal" sent out in the 80s for "a spherical device with sensors that could contain explosive pressures of <insert values for something equaling nuclear blast here>" --- reading the RFP, it was easy to see they were wanting something that would let them circumvent the air and underground testing bans.
I am sure the sensors would be fried before the blast even happens.

That is one hell of a ludicrous proposal.
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Old 2011-09-29, 12:19   Link #168
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Originally Posted by JMvS View Post
Ahh I think I understand where your concern is. But the whole point of the design is not that all the output of the bomb will be used for propulsion, but that the output is anyway so massive, compared to alternative, that it is much much more efficient compared to conventional rockets or ion propulsion, as long as high thrust and high specific impulse are seeked.

The point of the orion design is that of a pulsed reaction propulsion: the bombs would be launched at very short intervals, exploding at very short range behind the pusher plate.

And actually, the smallest yields achievable were sought after, in order to increase their frequency.
As far as I know the practical minimum yield for boosted devices is euqivalent to 20t of TNT. Now, such little devices produce less overall fallout then their much bigger brothers... but their fallout/yield ratio is worse, because the percentage of nuclear fuel that is not ideally utilized is higher (to some extent because of the volume/surface ratio becoming worse for smaller devices).

Quote:
Originally Posted by JMvS View Post
Moreso, technical solutions were proposed to minimize fallout:
Hm, I see that work in theory, but I wouldn't bet my life on it.

Quote:
Originally Posted by Vexx View Post
There was a lot of research at Los Alamos in the 80s about shaped nuclear weapons for use as "super bunker busters" to take out hardened missiles bunkers, etc. Some of it was unclassified and made its way into journals like Scientific American and some industry journals. At the time, I took it as more "Dr. Strangelove" style lunacy common at the time... but I never thought about the idea being used in relation to the ORION project. I'm still not sure the mechanical engineers wouldn't laugh their heads off at the technical requirements for a "firing plate" where the bombs would be ignited.

But there was a "request for proposal" sent out in the 80s for "a spherical device with sensors that could contain explosive pressures of <insert values for something equaling nuclear blast here>" --- reading the RFP, it was easy to see they were wanting something that would let them circumvent the air and underground testing bans.
I also read a lot of stuff too in east german magazines called "Jugend und Technik". Most of it I'ld consider propaganda. What really worked and did not work... and what was just theory and what not, was never well publizised on either side of the iron curtain.

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Originally Posted by SaintessHeart View Post
I am sure the sensors would be fried before the blast even happens.

That is one hell of a ludicrous proposal.
Actually, in theory you could have the sensors looking from very far away at what is happening. Imagine a long pipe or rather a long conrete wall with a long but very thin bore hole, place a sensor device at its end... sometimes it is enough to know the situation in one tiny part of the whole system... to estimate what is going on in the entire thing.

Last edited by Jinto; 2011-09-29 at 16:13. Reason: beim Namen der Zeitschrift hab ich mich wohl getäuscht... lang, lang ists her ^^'
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Old 2011-09-29, 13:17   Link #169
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More weeping for the pathetic excuse in the US we call the "telco/wireless" infrastructure

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Softbank, Japan's third-largest mobile carrier and exclusive purveyor of the Apple iPhone in the country, said Thursday it would launch in November a new wireless data network allowing downloads of up to 110 Mbps (megabits per second), faster than many wired connections provide today.
http://www.pcworld.com/article/24081...e_iphones.html

(looks at my 2GB/month cap at $30USD added to total bill and just rolls his eyes... and then multiplies it by the 5 lines we have and gets grumpy since there's no "shared data option" in the "family plans"
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Old 2011-09-29, 13:54   Link #170
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A technical questionm someone posed to me today. What about all the reactants exhaust from our rockets and spacecraft? Could those cause us problems in the future? Not so much about those used in the atmosphere, but those used in space. Everything stays up there, like the explelled fuel used my the moon shots or course corrections,m or pushes to get out of Earth orbit by our probes.

Is there any danger to the stuff? Running into it? Reentry? That sort of thing.
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Old 2011-09-29, 14:10   Link #171
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http://www.slate.com/articles/techno...our_job_5.html

Katz is working on something he calls "quantitative legal prediction." Thousands of patent cases are filed every year in the United States. There's a good chance, then, that MicroWidget's case against you shares some similarities with a bunch of those other cases. What if you could analyze the key features of MicroWidget's claim, and then see how thousands of comparable cases fared? "Lawyers will be able to say to their clients, 'Here's what we think your chances are—and based on 10,000 cases that are just like yours, here's what the computer thinks your chances are,' " Katz explains.

There is no machine that does this today, but it's coming. In the last piece, I examined the technology that's encroaching on journalism—computers are getting so skillful with language that they can now write stories all by themselves. But journalists are small fry; if you want to go after a profession that relies heavily on language, the deep-pocketed legal world is a fatter target.

In the last few years, the law has seen a rush of technological innovation, all stemming from computers' increasing capacity to decipher and understand written documents. Many law firms now use "e-discovery" tools that can scan large caches of evidence in search of interesting facts and figures. Firms also have software to draft legal documents in a fraction of the time a human would take. And a few services on the horizon might do even more—negotiate the terms of a contract, for instance, or determine whether or not you should sue.

Automation will bring legal services to the masses. Many people who ought to hire an attorney to handle business or personal disputes can't afford to do so. Software could potentially step in when you want to fight your mortgage lender, draw up contracts to start a small business, or sue for child-support payments.

While legal automation will be a boon for those who can't afford representation, it's bad news for lawyers. The industry is already in a slump, and law school is no longer seen as a sure path to riches. Because software will allow fewer lawyers to do a lot more work, it's sure to drive down both price and demand.
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Old 2011-09-29, 21:48   Link #172
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Originally Posted by Ithekro View Post
A technical questionm someone posed to me today. What about all the reactants exhaust from our rockets and spacecraft? Could those cause us problems in the future? Not so much about those used in the atmosphere, but those used in space. Everything stays up there, like the explelled fuel used my the moon shots or course corrections,m or pushes to get out of Earth orbit by our probes.

Is there any danger to the stuff? Running into it? Reentry? That sort of thing.
expelled gas isn't a *collision* problem as much as a *corrosion* problem. Run through enough clouds of it and it will corrode the exterior a bit... so far not a problem but yes - another reason to stop using matter-based propellant in the long run. Stuff in LEO eventually comes down... stuff at GEO will be there for the foreseeable future.
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Old 2011-09-30, 00:44   Link #173
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expelled gas isn't a *collision* problem as much as a *corrosion* problem. Run through enough clouds of it and it will corrode the exterior a bit... so far not a problem but yes - another reason to stop using matter-based propellant in the long run. Stuff in LEO eventually comes down... stuff at GEO will be there for the foreseeable future.
What do you mean by matter based propellant? You mean there is a way to convert ambient energy into mass for propulsion?
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Old 2011-09-30, 01:01   Link #174
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Propelant that leaves matter behind because it does not all convert into energy or the energy of expelling the matter at high speed leaves the matter behind.
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Old 2011-09-30, 01:42   Link #175
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Propelant that leaves matter behind because it does not all convert into energy or the energy of expelling the matter at high speed leaves the matter behind.
Propellant or fuel?

Propellant is supposed to leave matter behind due to Newton's First and Third Laws, the force generated by the spewing of propellant moves the object in its desired direction.

Fuel is a different thing, it powers something that generates a force to move something forward.

So in the context of rockets using oxygen-hydrogen boosters, the fuels of oxygen and hydrogen are mixed and ignited to generate the propellant steam/water, which has the sufficient mass to generate a force, which is then used to drive an object in its direction desired.

I am confused. "Matter-based propellants" sounds funny.
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Old 2011-09-30, 01:54   Link #176
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Originally Posted by Ithekro View Post
Propelant that leaves matter behind because it does not all convert into energy or the energy of expelling the matter at high speed leaves the matter behind.
The propelant is not the problem, but larger debris that may have been released together with the propelant. But typically space agencies try to reduce that risk, by using especially dirty devices like solid booster stages in the low earth atmosphere only (debris that are released in the early ascend of a rocket fall back on earth).

Btw. in todays applied technology the inertia of matter is utilized to get an impulse for propulsion in space. If it were converted to pure energy the propulsion would be very inefficient (simple example - what produces more recoil [propulsion]: a) shooting a bullet with Ekin = 4 kJ or b) shooting a laser beam that releases energy in the form of light at E = 4kJ).

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Old 2011-09-30, 01:55   Link #177
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I think he means anything that's neither giant gun nor elevator.
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Old 2011-09-30, 02:47   Link #178
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Think of most rockets as unregulated diesel engined 18-wheeler heavy transport spewing crud, ash, soot, bits of metal, etc. Now think of total mass-energy conversion with hardly any residue... or solar sails... or laser sails... or rail guns... or space elevators... or back to closer reality, at least a much more efficient burn with lowered residue.
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Old 2011-09-30, 07:28   Link #179
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Originally Posted by Vexx View Post
Think of most rockets as unregulated diesel engined 18-wheeler heavy transport spewing crud, ash, soot, bits of metal, etc. Now think of total mass-energy conversion with hardly any residue... or solar sails... or laser sails... or rail guns... or space elevators... or back to closer reality, at least a much more efficient burn with lowered residue.
It is a good idea, but tell that to Big Oil - they fear deconsolidation of their oligopoly.
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Old 2011-10-01, 18:43   Link #180
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Quote:
Originally Posted by Vexx View Post
There was a lot of research at Los Alamos in the 80s about shaped nuclear weapons for use as "super bunker busters" to take out hardened missiles bunkers, etc. Some of it was unclassified and made its way into journals like Scientific American and some industry journals. At the time, I took it as more "Dr. Strangelove" style lunacy common at the time... but I never thought about the idea being used in relation to the ORION project. I'm still not sure the mechanical engineers wouldn't laugh their heads off at the technical requirements for a "firing plate" where the bombs would be ignited.

But there was a "request for proposal" sent out in the 80s for "a spherical device with sensors that could contain explosive pressures of <insert values for something equaling nuclear blast here>" --- reading the RFP, it was easy to see they were wanting something that would let them circumvent the air and underground testing bans.
Yeah, but what material can withstand the heat generated by a nuclear blast? This whole thing seems very farfetched.
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