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Problems with Problems With The Orion Spacecraft #9: Stress
Myth:
The ship's structure itself ... has to be able to take the stress of sitting next to a bunch of exploding nuclear bombs. Even with shock absorbers, it would be under repeated stress of a type not experienced by any vehicle we have ever built. The ability of a battleship to survive the strain of firing its own guns was the subject of a considerable amount of development efforts in the early 20th century, and that strain would be dramatically less than the strain experienced by an Orion. -POS ---- Fact: "Both the pulse frequency and the acceleration profile are reasonably well simulated by a child's backyard swing operating through an arc 65deg each way from vertical". GA-5009 Volume 1 page 14 Quoted in Project Orion Page 179 http://spacebombardment.blogspot.com...-orion_21.html http://ntrs.nasa.gov/archive/nasa/ca...1965058729.pdf |
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Problems with Problems With The Orion Spacecraft #9: Stress
bombardmentforce wrote:
Myth: The ship's structure itself ... has to be able to take the stress of sitting next to a bunch of exploding nuclear bombs. Even with shock absorbers, it would be under repeated stress of a type not experienced by any vehicle we have ever built. The ability of a battleship to survive the strain of firing its own guns was the subject of a considerable amount of development efforts in the early 20th century, and that strain would be dramatically less than the strain experienced by an Orion. -POS ---- Fact: "Both the pulse frequency and the acceleration profile are reasonably well simulated by a child's backyard swing operating through an arc 65deg each way from vertical". GA-5009 Volume 1 page 14 Quoted in Project Orion Page 179 http://spacebombardment.blogspot.com...-orion_21.html http://ntrs.nasa.gov/archive/nasa/ca...1965058729.pdf Fact: Based on my recall of Footfall and my knowledge of thermonuclear tests in the Pacific and elsewhe Taking off in Orion would be one hell of an experience. Quite literally. It would start out as a pseudo-underground explosion, with the bomb being only metres away from the spacecraft's "bumper". Think vitrification. Think sublimation of metal. Think superhot gaseous vitrified rock and metal gases spewing out all sides. And you need to fire another within the next few seconds to maintain your momentum so you won't fall back down to the ground again. Designing a hatchway that can be blocked against subliming metal and yet pass a functioning thermonuclear device through, is beyond _my_ capabilities. I presume the Cavalry in those circumstances get Superman - Jor-El - to throw them in, albeit from a safe distance? I missed seeing Jor-El in Footfall - perhaps Niven and Pournelle couldn't pay him enough for a cameo deus ex machina appearance? Wesley Parish (And note: that factoid about the child's swing, fails to make the link between the child's swing and the thermonuclear explosion. The energy released in a thermonuclear explosion is orders of magnitude vaster than that expended in a child's swing. And that's the crux of the matter. If that vast instantaneous pulse of energy is to be absorbed to pass it on to the spacecraft, then it will be like being inside a battleship while firing a broadside. Except that battleship will have it helluva lot easier. And if it isn't passed on to the spacecraft, then it has been wasted. No ifs, no buts.) -- "Good, late in to more rewarding well."Â*Â*"Well,Â*youÂ*tonight.Â*Â*AndÂ*IÂ*was lookintelligent woman of Ming home.Â*Â*IÂ*trustÂ*youÂ*withÂ*aÂ*tenderÂ*silence." Â*Â*I get a word into my hands, a different and unbelike, probably - 'she fortunate fat woman', wrong word.Â*Â*IÂ*thinkÂ*toÂ*me,Â*IÂ*justupid. Let not emacs meta-X dissociate-press write your romantic dialogs...!!! |
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Problems with Problems With The Orion Spacecraft #9: Stress
In article ,
Tux Wonder-Dog wrote: It would start out as a pseudo-underground explosion, with the bomb being only metres away from the spacecraft's "bumper". Think vitrification. Think sublimation of metal. Think superhot gaseous vitrified rock and metal gases spewing out all sides. The ship would be up on towers, not flat on the ground, for launch. The initial bomb would be a small one, with bomb size ramping up thereafter. These would not be bare bombs, but packages with ablative propellant incorporated, so what would strike the pusher plate would be a jet of vaporized propellant, chosen by design to be within the limits of what the plate could take. (For a technical overview, see the paper on Orion and nuclear-pulse propulsion in the May/June 2002 issue of the AIAA's Journal of Propulsion and Power.) The plate surface would be sprayed with, roughly speaking, grease before each explosion; the plate itself would not ablate. This was tested, and it was effective enough to eliminate any need to make the plate itself out of anything exotic. And you need to fire another within the next few seconds to maintain your momentum so you won't fall back down to the ground again. Correct. It's a bad day for any vertical-takeoff vehicle if the engine cuts out just after takeoff. Designing a hatchway that can be blocked against subliming metal and yet pass a functioning thermonuclear device through, is beyond _my_ capabilities. See above -- no exotic materials required. And they would be fission devices, not fusion, barring the hypothetical pure-fusion bombs that some of the Orion designers were hoping for. Fast-acting mechanical devices are not magic. The best of the supersonic interceptors of the late 1950s could open weapons-bay doors, toss out a long-range air-to-air missile, and close the doors again, in something like 300 milliseconds, despite a supersonic slipstream. ...I missed seeing Jor-El in Footfall ... Note that Footfall is fiction, and should not be used as a textbook on Orion design. George Dyson's book "Project Orion" is a better source. (And note: that factoid about the child's swing, fails to make the link between the child's swing and the thermonuclear explosion. The energy released in a thermonuclear explosion is orders of magnitude vaster than that expended in a child's swing. The principles, however, remain the same. The shock-absorber system is resonant at a particular frequency, like the swing. You toss out bombs at that frequency. A charge for a battleship gun has orders of magnitude more energy than that of a .22 rifle, but the same physics applies to both, although the engineering is a bit harder for the big one. And that's the crux of the matter. If that vast instantaneous pulse of energy is to be absorbed to pass it on to the spacecraft, then it will be like being inside a battleship while firing a broadside. Except that battleship will have it helluva lot easier. No, the battleship has it a lot worse -- it has nowhere near the shock-absorber stroke that an Orion would. The recoil stroke for a battleship gun is severely limited by the requirement that the whole motion fit within a cramped turret even when the guns are elevated at a high angle. (You can't just make the turrets bigger because their walls and roof are thick armor, and they're already enormously heavy -- one of the problems cited with schemes to do major revisions to the Iowa-class battleships was that the USN apparently no longer has a shipyard crane that can lift one of those turrets.) -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
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Problems with Problems With The Orion Spacecraft #9: Stress
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Problems with Problems With The Orion Spacecraft #9: Stress
In article ,
Derek Lyons wrote: ... (There are a couple of unanswered questions about design principles and details IIRC. No showstoppers, but contrary to the handwaving of bombardmentfarce, we can't build one from a standing start - a non trivial amount of development must be done first.) No question about that. Outside reviewers consistently thought the Orion enthusiasts were being seriously optimistic about schedule and budget, with a lot of optimism about incompletely-solved problems. one of the problems cited with schemes to do major revisions to the Iowa-class battleships was that the USN apparently no longer has a shipyard crane that can lift one of those turrets.) That's a bit of a red herring - as the turrets were not lifted on in one piece in the first place... (In the second place, at least one of the cranes used for such jobs is still operational... Note that I said it had been cited -- I didn't say I believed it. :-) (I *thought* at the time that it had a smell of technical rationalization for a decision made on political grounds...) -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
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Problems with Problems With The Orion Spacecraft #9: Stress
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Problems with Problems With The Orion Spacecraft #9: Stress
On Sun, 23 Oct 2005 21:12:58 GMT, (Henry Spencer)
wrote: Note that I said it had been cited -- I didn't say I believed it. :-) ....You forgot something, Henry: [/weasel] :-) :-) ;-) OM -- "Try Andre Dead Duck Canadian Champagne! | http://www.io.com/~o_m Rated the lamest of the cheapest deported | Sergeant-At-Arms brands by the Condemned in Killfile Hell!" | Human O-Ring Society |
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Problems with Problems With The Orion Spacecraft #9: Stress
Henry Spencer wrote: In article , Derek Lyons wrote: ... (There are a couple of unanswered questions about design principles and details IIRC. No showstoppers, but contrary to the handwaving of bombardmentfarce, we can't build one from a standing start - a non trivial amount of development must be done first.) No question about that. Outside reviewers consistently thought the Orion enthusiasts were being seriously optimistic about schedule and budget, with a lot of optimism about incompletely-solved problems. Here's something _very_ interesting from that Orion .pdf that Rusty found: http://ntrs.nasa.gov/archive/nasa/ca...1977085619.pdf If you go over to page 134 of the report (pdf page 146) you will run into LENS (Low Energy Nuclear Source); a very low yield nuclear device that will is to be detonated near the pusher plate to check out how it behaves...nothing unusual in that...except that LENS is a....ready for this? "the LENS system, which is a very-low-yield "gun-type" plutonium assembly (see Fig. 7. 10)." You heard it here first- a gun assembly nuclear device employing plutonium, not uranium, as its fissile material. That was supposed to be impossible due to a unstable isotope of plutonium (Pu-240) that would cause it to pre-react if gun assembly was used, and which was supposed to not be separable from the Pu-239. Well, either the Orion team made a major slip in their report, or by 1964 we knew how to separate Pu-239 and Pu-240. Pat |
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Problems with Problems With The Orion Spacecraft #9: Stress
Henry Spencer wrote: In article , Tux Wonder-Dog wrote: It would start out as a pseudo-underground explosion, with the bomb being only metres away from the spacecraft's "bumper". Think vitrification. Think sublimation of metal. Think superhot gaseous vitrified rock and metal gases spewing out all sides. The ship would be up on towers, not flat on the ground, for launch. The initial bomb would be a small one, with bomb size ramping up thereafter. These would not be bare bombs, but packages with ablative propellant incorporated, so what would strike the pusher plate would be a jet of vaporized propellant, chosen by design to be within the limits of what the plate could take. (For a technical overview, see the paper on Orion and nuclear-pulse propulsion in the May/June 2002 issue of the AIAA's Journal of Propulsion and Power.) The plate surface would be sprayed with, roughly speaking, grease before each explosion; the plate itself would not ablate. This was tested, and it was effective enough to eliminate any need to make the plate itself out of anything exotic. And you need to fire another within the next few seconds to maintain your momentum so you won't fall back down to the ground again. Correct. It's a bad day for any vertical-takeoff vehicle if the engine cuts out just after takeoff. Designing a hatchway that can be blocked against subliming metal and yet pass a functioning thermonuclear device through, is beyond _my_ capabilities. See above -- no exotic materials required. And they would be fission devices, not fusion, barring the hypothetical pure-fusion bombs that some of the Orion designers were hoping for. Fast-acting mechanical devices are not magic. The best of the supersonic interceptors of the late 1950s could open weapons-bay doors, toss out a long-range air-to-air missile, and close the doors again, in something like 300 milliseconds, despite a supersonic slipstream. ...I missed seeing Jor-El in Footfall ... Note that Footfall is fiction, and should not be used as a textbook on Orion design. George Dyson's book "Project Orion" is a better source. (And note: that factoid about the child's swing, fails to make the link between the child's swing and the thermonuclear explosion. The energy released in a thermonuclear explosion is orders of magnitude vaster than that expended in a child's swing. The principles, however, remain the same. The shock-absorber system is resonant at a particular frequency, like the swing. You toss out bombs at that frequency. A charge for a battleship gun has orders of magnitude more energy than that of a .22 rifle, but the same physics applies to both, although the engineering is a bit harder for the big one. And that's the crux of the matter. If that vast instantaneous pulse of energy is to be absorbed to pass it on to the spacecraft, then it will be like being inside a battleship while firing a broadside. Except that battleship will have it helluva lot easier. No, the battleship has it a lot worse -- it has nowhere near the shock-absorber stroke that an Orion would. The recoil stroke for a battleship gun is severely limited by the requirement that the whole motion fit within a cramped turret even when the guns are elevated at a high angle. (You can't just make the turrets bigger because their walls and roof are thick armor, and they're already enormously heavy -- one of the problems cited with schemes to do major revisions to the Iowa-class battleships was that the USN apparently no longer has a shipyard crane that can lift one of those turrets.) -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | You are aware that the original launch point for Orion was either at Torrey Pines or Point Loma in the San Diego area. They had to leave TP when their test shots, with C4, distrubed the neighbors. Think what the real deal, even in a 'shallow silo', would have done for property values? |
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Problems with Problems With The Orion Spacecraft #9: Stress
Pat Flannery wrote:
You heard it here first- a gun assembly nuclear device employing plutonium, not uranium, as its fissile material. That was supposed to be impossible due to a unstable isotope of plutonium (Pu-240) that would cause it to pre-react if gun assembly was used, and which was supposed to not be separable from the Pu-239. Well, either the Orion team made a major slip in their report, or by 1964 we knew how to separate Pu-239 and Pu-240. .... or maybe that pre-reacting is perfectly acceptable in the low yield situation here? Paul |
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