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What about its ISP?
Use what is abundant and build to last
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If you could make it work, it would be fairly high (1000s of seconds), but the thrust would be so low and the price so high for the accelerator system (and its power supply) would negate the advantage over, say, NTR.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Would NTR be more efficient or the same? If it was the same, D-D Fusion has a political advantage: No radioactive waste. All that would be produced would be 'clean' Helium.
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Not really... both of them would only be useful in space anyway, so I don't think the political benefit comes anywhere close to offsetting how much easier it is to build a simple NTR engine. Also, the fusion engine might even require a regular nuclear reactor to operate the accelerator system.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Current fusion reactor technology barely produces more energy than it consumes, and it only does that for a few seconds. It weighs several thousand tons and requires a small army of people to operate. It has a very long way to go before it's ready for commercial energy generation on the ground, and much much further before its compact and light enough for space propulsion. At the present rate of progress, fusion energy plants won't be ready for inspace applications before people are on Mars.
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So the best bet would be to use small Fusion exposives, then? Some radioactive waste, but not as much as an NTR, and it's Fusion.
Use what is abundant and build to last
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Trouble is, no pure-fusion explosive systems are available, and in fact might never be.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I think Orion would probably be feasible as interplanetary transportation but never landing. Constructed in orbit, used to ferry back and forth between, say, Earth and Titan, but at those ends it would just transfer its cargo to other ascent/descent mechanisms in orbit rather than landing. It can dock with a space elevator and send cargo down via it, or it can have smaller shuttlecraft in bay to take things up and down, but an Orion should never get into a planet's atmosphere, IMO.
I'd definitely like to see some research done into an Orion-based heavy cargo transport with the mission to bring a bar of nitrogen from Venus to Moon or Mars.
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Hence the small amount of Radioactivity.
Use what is abundant and build to last
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If you are going to build an Orion ship in orbit, which will undoubtedly weigh a great deal and be even more expensive to build since you must minimize launch mass (hence everything has to be as light as possible), you might as well switch to a high-energy fission system. For Titan, getting Hydrogen from the Hydrocarbons & Water would make great GCNR or VASIMR propellant, or you could go all out and use the water for an NSWR engine if you have a lot of nuclear fuel lying around.
Orion has one and only one claim to superiority, and thats its immense launch capacity. If you aren't going to use it for that, don't bother.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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No, its claim to superiority is its immense thrust, which works just as well in space as in atmosphere, except in space the pollution is much less dangerous. If you're going to use it where its negatives do the least damage, go ahead and bother.
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It does have huge thrust, but for all thermal rockets except VASIMR have enough thrust already. We're talking burn times measured in minutes or only hours to leave LEO anyway.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I'm not talking leaving LEO, I'm talking about bridging interplanetary distances, for which 0.1c velocity can help a LOT. Going to Mars in days instead of months is a whole different ball game and you're not gonna get that out of current conventional rockets.
It's like, if your workplace is 60 miles away, you either have the option of walking the entire way (conventional rockets) or you can walk to the train station to catch the Orion which whisks you maglev express to the city, where you disembark the Orion and go down to the workplace with conventional rockets again.
What kind of an idiot walks the entire 60 miles?
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Er... what Gs are we talking here? 0.1c would require a lot of padding.
Use what is abundant and build to last
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Again, I have to question the logic behind this discussion. We do not need pure fusion explosives.
If it is OK to use gasolene powered road transport, which causes untold numbers of lung cancers each year and similar numbers of heart attacks (not to mention the people killed in direct collisions) why is it so unacceptable to use a fission propulsion system which will provide similar levels of benefit at a much lower cost?
We wouldn't refuse to use our cars for the fact that the exhaust might expose someone to a 10(-9) chance of cancer. Nor would we be willing to invest in very expensive hydrogen powered vehicles for that reason alone. The reason is that we consider the risk to be tollerable and the cost of reducing it further is disproportionate. That is the mature way of looking at these things.
The thing to work on isn't really the technology (nuclear fission), which is already good enough for the job, but people's perception of risk. Lets say that using BDBs to lift 10,000 tonnes into orbit costs $5billion. Using Orion to do the same thing costs $1billion, but statistically will cause 1 fatal cancer world-wide. I'm sure we can spend a lot less than 4 billion saving 1 human life somewhere in the world? We could save many more with anti-malaria measures in places like Africa and those people would appreciate it.
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I'm not talking leaving LEO, I'm talking about bridging interplanetary distances, for which 0.1c velocity can help a LOT. Going to Mars in days instead of months is a whole different ball game and you're not gonna get that out of current conventional rockets.
It's like, if your workplace is 60 miles away, you either have the option of walking the entire way (conventional rockets) or you can walk to the train station to catch the Orion which whisks you maglev express to the city, where you disembark the Orion and go down to the workplace with conventional rockets again.
What kind of an idiot walks the entire 60 miles?
10% of C?!
I think there is a disconnect somewhere in this discussion between what is practical and what is possible from Orion. Orion is unusual in that the efficiency of the propulsion scheme is directly dependent on the diameter of the pusher plate (and to a lesser extent what its made of, but I digress) and the yield of the bombs.
First off, Orion becomes exponentially better with a bigger pusher plate, so small (<1000MT) Orion's are no better than other nuclear drives. Bigger Orion's (<100,000MT) do beat out the smaller ones by an order of magnitude, making manned travel to the outer planets available, but are too huge to really be practical. Only the really monstrous ocean liner sized maga-ships (1,000,000MT+) get the efficiency needed for C-fractional space travel.
Small Orion = Not so hot versus other nuke drives
Also a word about the bombs, that for atomic bombs the efficiency (bang per kg) increases with yield up to around the low megaton range. In order to get the mid-to-high efficiencies possible with Orion, you need to use higher yield bombs. Trouble is, again as above, the smaller the Orion the smaller the maximum yield you can safely use due to radiation and shock absorption concerns.
Oh, and I'd watch how you swing the "idiot" word around here, lest you get thrown into the same box as gaetano or ol' Rick.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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The explosions *do* take place inside a cylinder which directs them out the back, don't they? Anything else would be extremely inefficient.
ol'Rick? Who's he?
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Oh no, certainly not, the nuclear bomb is dropped behind the ship and detonates well clear of it. Containing a blast of that size is simply out of the question.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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If the pusher plate was curved round though...
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...Then the plate becomes much, much too heavy and you don't get anywhere, were it thick enough to withstand the blasts. The original plate even for a "small" Orion is a solid block of steel or copper.
Oh, there was a fellow named Rick (I forget his last name), who was mentally unstable who came around these parts now and then spouting crazy ideas, soliciting money for his space program (no, really) and accusing board members of being CIA operatives (yes, again no kidding) out to "stop" him. Among other things... he eventually got banned after threating physical harm on other people here.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Oh no, certainly not, the nuclear bomb is dropped behind the ship and detonates well clear of it. Containing a blast of that size is simply out of the question.
The bombs contain shaped lenses of propellant and a few milliseconds after detonation they squirt around 50% of the explosive energy of the blast into a narrow jet, that transfers its momentum onto the pusher plate. This is analogous to the shaped charges used in conventional explosives.
Another way of increasing the efficiency of the blast would be to fit a superconducting magnetic ring into the pusher plate. This would effectively contain the hot ions in much the same way as a rocket nozzle.
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What about mini mag orion? does it do ok?
On another, note, Orion is practical, but not allowable. I don't want that many radioisotopes in my solar system. And imagine what happens if a ship equipped for .1c goes supercritical- I'd say that it would outshine the sun.
-Josh
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What about mini mag orion? does it do ok?
On another, note, Orion is practical, but not allowable. I don't want that many radioisotopes in my solar system. And imagine what happens if a ship equipped for .1c goes supercritical- I'd say that it would outshine the sun.
Why is radioactivity a problem at all? Our own bodies are radioactive! So is everything that we touch and the very air that we breath.
Don't know about a mini-mag Orion. Even early versions of Orion depended upon focused nuclear charges, so the efficiency of the pusher plate will not increase linearly with increasing plate surface area. But as the ship increases in size, bigger bombs are used which are naturally more efficient with higher power to weight ratio which increases effective ISP. Very small designs need to rely upon very small pure fission bombs which are inefficient and dirty. Even if it were possible to magnetically extend the pusher plate, bigger bombs would produce unacceptable acceleration in a smaller Orion.
As for the possibility of all the bombs on the ship being triggered by a spontaneous detonation, that is simply not how A-bombs work. The frequency of a spontaneous detonation of even a single bomb is minute. If one goes off it will vaporise the others, but will not trigger fission.
Space is such a vast and radiation filled environment that the few tonnes of radioactivity produced by an Orion isn't going to be a problem to anyone.
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The bombs contain shaped lenses of propellant and a few milliseconds after detonation they squirt around 50% of the explosive energy of the blast into a narrow jet, that transfers its momentum onto the pusher plate. This is analogous to the shaped charges used in conventional explosives.
Another way of increasing the efficiency of the blast would be to fit a superconducting magnetic ring into the pusher plate. This would effectively contain the hot ions in much the same way as a rocket nozzle.
Thats already been factored in I believe.
And as Antius points out, a magnetic field to extend the pusher plate will only be a limited enhancement. The Isp is dependent on pusher plate diameter, but it is also dependent on warhead yield, and regardless the size of the pusher plate the maximum yield is also limited by the mass of the vehicle. If its too light, it can't absorb the shock and would be rattled to bits.
It should also be emphasized that a "small efficient bomb" is an oxymoron, because it is very hard to make small bombs explode versus bigger ones.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I'm rather surprised to see this topic dug up: IMO, it never gets the attention it deserves as a near-term interplanetary system that blows the lid off of the usual ways it's done.
samy:
I'm not talking leaving LEO, I'm talking about bridging interplanetary distances, for which 0.1c velocity can help a LOT. Going to Mars in days instead of months is a whole different ball game and you're not gonna get that out of current conventional rockets.
I'll go further and say that you're not likely to get that out of anything as close to coming off the drawing boards as Orion.
This is presumably for one of Dyson's daydream interstellar versions. I could see it used for interplanetary use, out to Oort cloud colonies. Up to 40 million tons, using megatonne yield bombs in propulsion charges of 1300 tons each. Several hundred thousand of them... (Note that this one was his own baby; no official work was done on it. The smaller, nearer-term ones were very heavily investigated by scientists & engineers in all applicable fields of specialization.)
Here, I'm not thinking of a magnetic field that "extends the pusher plate", but totally replacing it. For these future huge .1C ships, instead of improbably huge shock absorbers and plates, think of Mag-Orion, throwing huge clouds of plasma at the ship's magnetic sail field. Absolutely no consideration for plasma/matter interaction, no radiation other than what cosmic rays make it through the magnetic sail field. Ships big enough on trips long enough to extend dumbell arms for spin-G (if they don't go all-out for the mass of a torus).
I can't find much online about the Mag Orion, but from what there is about the Magnetic sail, it's not too big a stretch to make one to intercept a deliberate pulse of plasma from a big stand-off bomb.
Again, acceptable superconductors for the magnetic sail coils are far more readily foreseeable than breakthroughs that allow any other high performance ship.
samy:
No, its claim to superiority is its immense thrust, which works just as well in space as in atmosphere, except in space the pollution is much less dangerous...
Again I'll go further, and say if it's for space-use, then environmental concerns become nil. Completely negligible.
jumpboy11j:
Orion is practical, but not allowable. I don't want that many radioisotopes in my solar system.
I hope you don't mean floating around in space... That's a good analogy of what space is like! (radiation blasted waste) If you mean having that many nuclear explosives being built, transported, and detonated by every big ship out there, then that's another concern.
We've addressed international cooperation in building one of these. Diamond cutters/sellers don't let a tenth of a gram per year of material "go missing".
A lot of thought here about the potential cost of relying on nuclear explosives, a very tricky item. I'd bet that is an over-estimation. The original numbers they worked out still stand, and I doubt that anybody would know it better than Dr. T.Taylor. It was surprisingly inexpensive, by the numbers they were using. Maybe it's more expensive now, if only because of cleanup concerns at the factories where the metal is machined into the parts of the pit of the bomb. (I've read a lot of what they're going through with the Rocky Flats trigger factory)
Until we can speak of space manufacturing, the only reasonable use for Orion (where it still outperforms everything else which could be made as readily) is the 10 meter HLV-sectional lifted, space assembled ship. ~550 tons starting in HEO. Either slow trips with ~50%+ being cargo, or lightly loaded ones taking incredibly fast "leaps" across the solar system, totally ignoring synodic periods and typical interplanetary trajectories.
What other sort of nuclear propulsion that can be built today, offers this in ships under a thousand tons?
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