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Post by Cybermortis on Jun 27, 2013 15:57:28 GMT
Back in the late 1940's, when atomic energy was seen as the solution for all problems, the idea was banded around of using nuclear explosions to propel a spacecraft. Although the original project was shut down in 1965 (as people started to realise that setting off nukes had a few drawbacks) the principal has remained in several forms.
The basic idea that you set off an explosion in a controlled manner under the craft, the shock-wave hits an armoured plate at the base of the craft pushing it upwards. Repeat before gravity takes hold and you get continuous thrust.
I've seen this principle used with lasers being fired into a cone shaped 'craft', with the suddenly heated air providing the explosion, but can't recall if anyone has really tried this with explosives.
Is this something that MB could look at? It is complex in practice (the timing system certainly seems to be) but is there a 'simple' way to test this out?
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Post by watcher56 on Jun 28, 2013 3:29:02 GMT
Sounds like an external combustion pulse jet. Don't think it would be a very efficient use of the energy.
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Post by the light works on Jun 28, 2013 5:40:16 GMT
It would be an interesting project to try for. I'm thinking something like a miniature rocket sled, but using SMALL explosives as the fuel supply. at least for the small-scale tests...
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Post by mrfatso on Jun 28, 2013 10:26:55 GMT
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Post by Cybermortis on Jun 28, 2013 13:51:29 GMT
Orion was the original project which ran from 1947-1965, but there have been at least two more projects since then - although I don't think those ever went past the design stage. Thanks for the link to the video, I suspected that a project that ran for almost 20 years must have conducted some sort of test even in the era where any crazy idea could get military funding. |
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Post by the light works on Jun 28, 2013 14:15:34 GMT
Orion was the original project which ran from 1947-1965, but there have been at least two more projects since then - although I don't think those ever went past the design stage. Thanks for the link to the video, I suspected that a project that ran for almost 20 years must have conducted some sort of test even in the era where any crazy idea could get military funding. you mean there was an era when it couldn't? |
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Post by ironhold on Jun 28, 2013 15:03:58 GMT
Actually, yes - the 1920s (the post-WWI period) and the 1960s / 1970s saw reductions in funding for the military due to both public sentiment and government fiscal policy. In the 1920s, things were so bad that the military did not even have enough money to operate their tanks during training; instead, trucks had signs on the sides that read "tank", and soldiers were regarded to treat them as such. In the 60s / 70s, not every project was actually given funding, no matter how promising. For example, the XB-70 Valkyrie was axed in large part because ICBMs could do the job cheaper and more easily; the engine was deemed far too expensive for the day, and the budget didn't allow for the aircraft to be upgraded with counter-measures. |
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Post by Cybermortis on Jun 28, 2013 15:27:24 GMT
Actually, yes - the 1920s (the post-WWI period) and the 1960s / 1970s saw reductions in funding for the military due to both public sentiment and government fiscal policy. In the 1920s, things were so bad that the military did not even have enough money to operate their tanks during training; instead, trucks had signs on the sides that read "tank", and soldiers were regarded to treat them as such. In the 60s / 70s, not every project was actually given funding, no matter how promising. For example, the XB-70 Valkyrie was axed in large part because ICBMs could do the job cheaper and more easily; the engine was deemed far too expensive for the day, and the budget didn't allow for the aircraft to be upgraded with counter-measures. I'd suspect that by the 70's it was starting to dawn on even the most spend-happy government officials that spending billions on projects that gave you nothing in return (or which involved dosing your own intelligence agents with LSD) wasn't exactly the best defence plan. Projects like the Sargent York probably helped convince those members of the military brass who grumbled over cutbacks. That machine's targeting system was so dire that during trials it first considered a portable toilet to be the primary threat in the area. Then on another occasion that was being overseen by very senior officers from the US and UK military, it decided that the biggest threat was the military brass* and locked onto the stand where they were all sitting. (*A sentiment that would probably echo the feelings of most soldiers). |
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Post by ironhold on Jun 28, 2013 15:52:40 GMT
If you ever want to have a laugh, go on over to M2 Museum.com and look at some of the various civilian and military vehicles that became Micro Machines. For example, the Sgt. York made the cut... in 1998. |
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Post by silverdragon on Jul 1, 2013 6:25:16 GMT
Thinking out loud....
Isnt the SRB, Solid Rocket Booster, the answer to all of this?...
It is, after all, one BIG solid fuel controlled explosion, that kicks the shuttle into somewhere where the other main engines can achieve orbit?....
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Post by Cybermortis on Jul 1, 2013 7:52:51 GMT
Not sure what you mean by 'the answer to all this'? The Orion Project was intended to create a spacecraft that used nuclear bombs as the propulsion system. Although the original idea was dropped by 1965, not least because everyone had started to wake up to how bad an idea setting nukes off in the atmosphere was, NASA seems not to have fully ditched the idea. There are/were at least two related designs drawn up. The first was a pure space-craft, that would use nukes for propulsion well outside the atmosphere - unlike Orion that used Nukes to get into orbit. The second is to create a concave reflective base to a 'rocket' and aim a laser into it. This latter technique is only intended to get a craft into orbit, but has the advantage that the craft doesn't need to carry the huge fuel supply existing craft need just to get into orbit - which saves costs per launch, at least over the long run. So the theory seems sound, meaning that technically it isn't really a 'myth' in the purest sense*. But it is a design that most people would never have heard of, and would probably consider insane at best. But then we have the need for a careful design, the possibility not only of adding some 'hard science' into the show but also of having a build off between designs drawn up and built by the cast. Seems like a winning formula to me - Mythbusters, strange idea, explosions...LOTS of explosions.... (*Of course it could and has been argued that 'curving a bullet' amongst others is hardly a myth in the strictest sense, since two seconds thought** or a passing knowledge of physics would bust the idea outright.) (**OK, maybe a minute or two if you are American...  ) |
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Post by the light works on Jul 1, 2013 14:13:47 GMT
I think Silverdragon may have missed the key detail of the pulse propulsion system. - that being that rather than one long slow combustion as a rocket engine; the propulsion comes from a series of rapid explosions. it's like putting a firecracker under an empty can, and when it stops accelerating upwards, immediately setting off another to push it higher.
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Post by silverdragon on Jul 2, 2013 6:52:24 GMT
TLW I got that.... more than one explosion....
But back to what I suggested, the SRB.
Its one big controlled explosion,
[so how about a re-design that "Feeds through" that solid rocket fuel to make a series of smaller controlled explosions.?.. ]
But again, the SRB has been designed as a controlled explosion to deliver just the right amount of boost as is needed....
So instead of a series of "pulse" bangs, its delivering a long ba[aaaaaaaaaaa]ng....
If more boost was required, per unit, shorter fatter larger explosion surface area, if less boost longer thinner smaller explosion surface area....
I believe the thinking behind that was all down to stress.
Series of repeated explosions puts differing stresses on the part that gets the push....
One continuous explosion has one continuous stress, I believe less stress cracks would be created by one burn rather than a series of burn/cool/burn/cool... therefore less weight.....
You also get into the area of weight/mass, and how much propulsion can you get from [x] amount of potential fuel compared to how much thrust, and how much equipment needed to control that thrust...
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Post by Cybermortis on Jul 2, 2013 11:46:41 GMT
High explosives contain considerably more energy than conventional propellants to the point that using high explosives as a propellant runs into an eye watering number of problems. The main one is that HE's are more than capable of producing forces that will shatter any 'tube' we can produce - unless you make it so thick and heavy and the amount of HE so small you'd be better off using something with less energy.
Of course that energy is in a much more compact form, so you can carry more thrust per pound of propellant. Consider that almost 70% of the weight of a shuttle that was sitting on the launch pad was in the two solid rocket boosters, they still needed the help of the main engines (and its HUGE fuel tank) and they still were not capable of getting into orbit. Now if you could replace the existing propellant with a high explosive...well the SRB's contain just under 500 metric tons of fuel EACH for roughly 2 minutes of flight. You could get the same amount of flight time and lifting capacity from a considerably smaller amount of HE. Even accounting for the need for a blast plate at the base of the craft you'd end up with a lighter over all launch vehicle sitting on the pad.
The amount of thrust and stress placed on the craft would be controlled by the distance the explosives were detonated from the craft. In a modern craft this would probably be done by computer, back in the 1950's they probably worked out the distance on paper and wired the charges to go off at after a certain interval - much the same as basic duel-stage rockets. You would also be making sure that the force of the blast was equal over the face of the entire blast plate - if it isn't stress is the least of your worries as unequal thrust is going to push you off course and possibly cause you to tumble.
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Post by the light works on Jul 2, 2013 13:02:12 GMT
High explosives contain considerably more energy than conventional propellants to the point that using high explosives as a propellant runs into an eye watering number of problems. The main one is that HE's are more than capable of producing forces that will shatter any 'tube' we can produce - unless you make it so thick and heavy and the amount of HE so small you'd be better off using something with less energy. Of course that energy is in a much more compact form, so you can carry more thrust per pound of propellant. Consider that almost 70% of the weight of a shuttle that was sitting on the launch pad was in the two solid rocket boosters, they still needed the help of the main engines (and its HUGE fuel tank) and they still were not capable of getting into orbit. Now if you could replace the existing propellant with a high explosive...well the SRB's contain just under 500 metric tons of fuel EACH for roughly 2 minutes of flight. You could get the same amount of flight time and lifting capacity from a considerably smaller amount of HE. Even accounting for the need for a blast plate at the base of the craft you'd end up with a lighter over all launch vehicle sitting on the pad. The amount of thrust and stress placed on the craft would be controlled by the distance the explosives were detonated from the craft. In a modern craft this would probably be done by computer, back in the 1950's they probably worked out the distance on paper and wired the charges to go off at after a certain interval - much the same as basic duel-stage rockets. You would also be making sure that the force of the blast was equal over the face of the entire blast plate - if it isn't stress is the least of your worries as unequal thrust is going to push you off course and possibly cause you to tumble. and, of course, the original scheme of using nukes had exponentially more thrust per mass. |
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Post by Cybermortis on Jul 2, 2013 13:52:32 GMT
Quite, to put it in context the smallest nuke that you can build would similar to the Davy Crockett produced and deployed by the US Army. This had a weight of 71 lbs. This means that you could have almost 16,000 of these for the mass of the fuel of a single SRB. Half that would be enough to not just get you into orbit, but probably to Mars and back as well.
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Post by the light works on Jul 2, 2013 13:55:58 GMT
Quite, to put it in context the smallest nuke that you can build would similar to the Davy Crockett produced and deployed by the US Army. This had a weight of 71 lbs. This means that you could have almost 16,000 of these for the mass of the fuel of a single SRB. Half that would be enough to not just get you into orbit, but probably to Mars and back as well. and so what if they would have to disembark you from the capsule with a mop.  |
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Post by Cybermortis on Jul 2, 2013 14:54:45 GMT
Quite, to put it in context the smallest nuke that you can build would similar to the Davy Crockett produced and deployed by the US Army. This had a weight of 71 lbs. This means that you could have almost 16,000 of these for the mass of the fuel of a single SRB. Half that would be enough to not just get you into orbit, but probably to Mars and back as well. and so what if they would have to disembark you from the capsule with a mop. This is the thing, if you tell most people about the idea they think of the force of a blast and assume that the result will be human paste. What people forget is that the force of the shockwave and the energy it imparts goes into moving the entire mass of the craft, and so gets 'watered down'. They also forget or miss that you can vary the amount of force/thrust the craft is getting by the distance it is from the detonation. With conventional rockets you are limited as to the mass you can move based on the amount of thrust the engine can put out. With the 'Orion' design you've got far more energy available for thrust than you can safely use. Meaning that the only limit on the size and weight of the craft is how close you can set the blast off. |
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Post by the light works on Jul 3, 2013 0:05:23 GMT
and so what if they would have to disembark you from the capsule with a mop. This is the thing, if you tell most people about the idea they think of the force of a blast and assume that the result will be human paste. What people forget is that the force of the shockwave and the energy it imparts goes into moving the entire mass of the craft, and so gets 'watered down'. They also forget or miss that you can vary the amount of force/thrust the craft is getting by the distance it is from the detonation. With conventional rockets you are limited as to the mass you can move based on the amount of thrust the engine can put out. With the 'Orion' design you've got far more energy available for thrust than you can safely use. Meaning that the only limit on the size and weight of the craft is how close you can set the blast off. I was thinking of them miscalculating. |
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