Nuclear Pulse Propulsion: Absurd Unscientific Concept?

[Brotoro]

The pusher plate of an Orion is not a kilometer in diameter.

Also, the shock absorber problem is just one of engineering.

I once attended a talk at Los Alamos National Lab where the presenter discussed a variation of the Orion concept that used a large canopy (looked something like a large parachute) that would be on lines kilometers ahead of the main body of the ship. The propulsion nukes in this case were detonated far ahead of ship, but behind the "parachute" which acted to catch part of the expanding cloud from the bomb. This rapidly accelerated the "parachute", and line was played out from the main ship while it was accelerated forward. Once the impulse of the blast had been absorbed, the "parachute" was reeled back to its original distance from the main ship and the another nuclear propulsion charge could be sent forward for the next impulse.

The talk was titled "Bungie Jumping to Mars" or something like that.

Edited April 5, 2014 by Brotoro

[DJEN]

this isn't at all related to the subject matter, but seriously, the title... please don't do this

Subject Matter That I Don't Know A Lot About: Stupid and Impossible? find out more at 11!

this is the lowest form of invitation to discussion

I have to agree. It seems to me that there's no place for me in this forum.

[78stonewobble]

Unarmed bombs sill can break into pieces. There is a huge missing chunk of uranium somewhere in the state of eureka.

Didn't a few russian nuclear reactors from satelites reenter earths atmosphere?

As far as I remember, people weren't dying in droves, where the leftovers of those landed.

The B-52 crashes? Thats harder to say. Radiological cleanup certainly isn't the safest job in the world, but with adequate protection and without the secrecy and rush during ie. the cold war, it could be done relatively safely.

[KASASpace]

The pusher plate of an Orion is not a kilometer in diameter.

Also, the shock absorber problem is just one of engineering.

I once attended a talk at Los Alamos National Lab where the presenter discussed a variation of the Orion concept that used a large canopy (looked something like a large parachute) that would be on lines kilometers ahead of the main body of the ship. The propulsion nukes in this case were detonated far ahead of ship, but behind the "parachute" which acted to catch part of the expanding cloud from the bomb. This rapidly accelerated the "parachute", and line was played out from the main ship while it was accelerated forward. Once the impulse of the blast had been absorbed, the "parachute" was reeled back to its original distance from the main ship and the another nuclear propulsion charge could be sent forward for the next impulse.

The talk was titled "Bungie Jumping to Mars" or something like that.

The Medusa?

It is interesting, but would it be shaped charges as well?

And what about the "parachute"'s materials?

[Brotoro]

Hmmm… Yes, the diagrams and the timeframe are correct for it to have been this Medusa system (but I don't remember him using that name…nor do I remember if the guy giving the talk was Johndale Solem).

As I recall, the "parachute" material was some kind of high-tech plastic, quite thin. And I presume shaped charges would be used, yes. Better efficiency.

"Image: Medusa in operation. Here we see the design 1) At the moment of bomb explosion; 2) As the explosion pulse reaches the parachute canopy; 3) Effect on the canopy, accelerating it away from the explosion, with the spacecraft playing out the main tether with its winch, braking as it extends, and accelerating the vehicle; 4) The tether being winched back in. Imagine all this in action and the jellyfish reference becomes clear. Credit: George William Herbert/Wikimedia."

Edited April 6, 2014 by Brotoro

[magnemoe]

One would have to assume the bombs wouldn't be armed during launch. There have been crashes of planes carrying nuclear weapons before, though nowhere near as many as an Orion refueler would. Definitely an unpleasant thought.

Yes setting of an nuclear bomb by accident is extremely unlikely, they are very hard to get to explode, yes they might blow up as dirty bombs but no nuclear explosion.

[KASASpace]

Yes setting of an nuclear bomb by accident is extremely unlikely, they are very hard to get to explode, yes they might blow up as dirty bombs but no nuclear explosion.

However, it is more likely to happen when there are more bombs that that have that possibility.

[KASASpace]

Hmmm… Yes, the diagrams and the timeframe are correct for it to have been this Medusa system (but I don't remember him using that name…nor do I remember if the guy giving the talk was Johndale Solem).

As I recall, the "parachute" material was some kind of high-tech plastic, quite thin. And I presume shaped charges would be used, yes. Better efficiency.

http://i61.tinypic.com/5uq03l.png

"Image: Medusa in operation. Here we see the design 1) At the moment of bomb explosion; 2) As the explosion pulse reaches the parachute canopy; 3) Effect on the canopy, accelerating it away from the explosion, with the spacecraft playing out the main tether with its winch, braking as it extends, and accelerating the vehicle; 4) The tether being winched back in. Imagine all this in action and the jellyfish reference becomes clear. Credit: George William Herbert/Wikimedia."

Interesting system indeed.

It doesn't have all that un-needed structural stuff like the Orion.

What about the tether? Carbon-nanotubes? That would be my choice.

Reminds me a bit of the ISV Venture Star, as a trailer system.

[Person012345]

1. Material strength: can the craft's materials endure the nuclear blasts and the acceleration?

Yes

2. Ablation of plate/sail: can the plate/sail stay intact long enough?

Yes, probably

3. Square/Cube law: can the ship be durable enough?

Yes.

As Wikipedia did not provide much information regarding these reasons, I'm here to ask of more information.

Well it has an entire section on potential problems which specifically addresses one of your questions and I don't think you'd be the first person ever to question whether the structure could hold together so the fact that it's not mentioned is an answer by itself.

Nuclear bombs are not magical all-destroying bringers of doom. Although bear in mind, it's all theoretical because we've never actually built one.

[meve12]

However, it is more likely to happen when there are more bombs that that have that possibility.

Technically, yes.

However, nukes have to compress their 'fuel' into a very small, very dense ball in order to detonate, which they do with a sphere formation of charges around the 'fuel'. This requires very precise timing- all of the charges have to go at the exact same time, or the 'fuel' gets scattered instead of fissioning. External charges do the same thing. Furthermore, the charges themselves are usually plastic explosives, so they don't accidentally cook off and ruin the nuke.

The only way to detonate a nuke is to send the signal to detonate it. They don't cook off even if another nuke blows up nearby- they'll just get vaporized (Same applies to ICBMs arriving at the same target at more-or-less the same time-the first nuke vaporizes the late-comers. This is called nuclear fratricide.)

[LaydeeDem]

Unscientific?

Looks pretty real to me:

[78stonewobble]

Unscientific?

Looks pretty real to me:

It does look pretty crazy though. ... kinda like ... kicking upsidedown over a fireworks battery or something.

I seem to remember that the first ideas for fusion energy production consisted of a large cavern filled with water and bombs dropped into it, turning the water into steam.

As others say building something that can actually survive even nuclear bombs and then further turn that into useable energy is an engineering problem. Though offcourse, there is a difference between theoretically possible and practically feasible.

However, I think we could benefit somewhat more from this in the near term. If we ever discover something on course for earth our only option so far, is still to try to deflect it with nuclear weapons (everything else needs to be built from scratch first) and they simply carry an energy density far beyond anything else.

Politically? I think there needs to be an exception to the different treaties regarding nuclear weapons testing and weapons in space. Possibly a program mandated by the UN.

We need to test a few on different asteroids, comets and what not. To see if it's even possible, to use nuclear weapons that way.

Edited April 7, 2014 by 78stonewobble

[78stonewobble]

However, it is more likely to happen when there are more bombs that that have that possibility.

I think at one time the USA and the USSR combined had arsenals of upto 70.000 plus nuclear weapons. I don't think I've heard of one going off accidentally yet.

They've lied in burning airplane fuel and been shot out of missile silos by missiles exploding, so it does seem rather rare.

[Nibb31]

No, but mass producing them to use as a means of propulsion opens up a lot of security issues.

[Aghanim]

Agreed. If one of that nuke is missing a city will be destroyed. That is why I support the DT pellet detonator option, but TWR is less than one

[Rakaydos]

Agreed. If one of that nuke is missing a city will be destroyed. That is why I support the DT pellet detonator option, but TWR is less than one

Actally, the orion nukes are tiny. You're only looking at destrying an area a few city blocks across.

[CaptainBlue]

Usually, the nukes are detonated a bit of distance away from the plate. Sudden G-shocks? Why, the bombs have timers you can adjust as required, or shoot out the bombs faster or slower to adjust detonation distance. Wow, so hard to think this up, it took me almost ten seconds.

[Nuke]

Actally, the orion nukes are tiny. You're only looking at destrying an area a few city blocks across.

it pays off to have the smallest nukes possible, since it allows for more precise control of "burns" (booms?).

theoretically if you could produce island of stability elements, you can make your nukes really damn small. but dont hold your breath, thats really theoretical.

[Red Iron Crown]

Is there a lower limit to how powerful a nuclear bomb can be practically made?

[Rakaydos]

Usually, the nukes are detonated a bit of distance away from the plate. Sudden G-shocks? Why, the bombs have timers you can adjust as required, or shoot out the bombs faster or slower to adjust detonation distance. Wow, so hard to think this up, it took me almost ten seconds.

An adjustable timer doesnt work as well because the timing of the bombs is synchrinized to the shock absorber's motion. However, a variable speed launcher fills the same role, able to keep the bombs detonating at the same intervals but mdifying how far from the plate they detonate.

[Rakaydos]

Is there a lower limit to how powerful a nuclear bomb can be practically made?

Yes... below a certuian point the compression you need to cause supercriticality in a tiny mass is too hard to maintain, and the bomb only burns a fraction of it's (already small) mass scattering the rest of it's mass around.

Basically, the smaller you make a bomb, the less efficent and dirtier it is.

[-Velocity-]

Is there a lower limit to how powerful a nuclear bomb can be practically made?

Yes and no. Yes, if you're only willing to accept an efficient explosion. You wouldn't want an inefficient bomb if you're trying to propel a spacecraft.

And no, not if you're willing to accept a low efficiency. You can make a nuclear weapon "fizzle" more easily than you can make it explode efficiently with a high yield, just ask North Korea (this is especially true if you're using implosion-type weapons).

But at any specific efficiency, you do have a minimum practical yield you can achieve. This is caused by the fact that everything has to be kicked off by a supercritical mass of plutonium 239 or uranium 235. There are ways to reduce that critical mass (such as explosive compression, neutron reflectors, or a combination of the two), but those can only take you so far. At some point, if you desire a lower yield, you'll have to accept a lower efficiency.

Notice I ignore the hydrogen bomb in this discussion. That is because the hydrogen bomb has to be triggered by a fission weapon. Secondly, many (most?) nuclear weapons that incorporate nuclear fusion- thermonuclear weapons- get most of their energy from fission anyway, as they work by using the neutrons produced by fusion to boost the efficiency of the fission reactions.

[78stonewobble]

Is there a lower limit to how powerful a nuclear bomb can be practically made?

Two examples here:

http://en.wikipedia.org/wiki/Special_Atomic_Demolition_Munition

http://en.wikipedia.org/wiki/Davy_Crockett_(nuclear_device)

A little ps:

I wouldn't want an orion type spacecraft taking off from earth, but it could work if built in space.

However as another poster mentioned I only see this being used in an "we're all gonna die cause the sun is gonna go supernova" bad scifi scenario and unless that happens I'd rather wait for another type of propulsion.

Edited April 7, 2014 by 78stonewobble

[KASASpace]

Technically, yes.

However, nukes have to compress their 'fuel' into a very small, very dense ball in order to detonate, which they do with a sphere formation of charges around the 'fuel'. This requires very precise timing- all of the charges have to go at the exact same time, or the 'fuel' gets scattered instead of fissioning. External charges do the same thing. Furthermore, the charges themselves are usually plastic explosives, so they don't accidentally cook off and ruin the nuke.

The only way to detonate a nuke is to send the signal to detonate it. They don't cook off even if another nuke blows up nearby- they'll just get vaporized (Same applies to ICBMs arriving at the same target at more-or-less the same time-the first nuke vaporizes the late-comers. This is called nuclear fratricide.)

I know how nuclear weapons work, and I also know about plastic explosives being used.

However, if the conditions are right, an electrical current could arise and cause the nuke to explode.

[KASASpace]

I think at one time the USA and the USSR combined had arsenals of upto 70.000 plus nuclear weapons. I don't think I've heard of one going off accidentally yet.

They've lied in burning airplane fuel and been shot out of missile silos by missiles exploding, so it does seem rather rare.

They have many safety mechanisms of course.

However, they have most likely never been transported en mass, as would be necessary to refuel an Orion.