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The Case For A Non-nuclear Project Orion


Spacescifi
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Fuel/air bombs are said to exceed even some kinds of fission and nuclear bombs (likely not the maxed out ones).

That said, in theory, spacecraft could be launched and use fuel/air bombs where air is still thick enough to help the explosion of the bombs.

 

Where air thins out... perhas there are non-nuke shaped charge bombs that could still propel it at better than normal chemicsal rocket efficiencies?

 

 

Granted it won't lift as much as the original Project Orion, but perhaps it could compete with chemical rockets at least?

 

What do you think?

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5 hours ago, JoeSchmuckatelli said:

Weight and volume compared to oomph. 

Math just doan werk out

If you think about it - traditional rocket is a fuel air bomb just with a controlled burn.  

 

 

1 hour ago, Gargamel said:

Yup, non nuclear Orion would just be a traditional rocket with really bad nozzle design. 
 

 

 

So in plainly you are saying that thermobaric bombs have a TWR on par with chemical rockets? Which means rockets SHOULD outperform them due to actually having nozzles?

But... I was thinking what if the thermobaric bomb was one nuke level blast? Surely there are thermobaric bombs that generate more energy per second than the chem rockets and weigh less than the combined weight of all that propellant and tankage, and turbopumps/pipes?

Maybe the pusher plate can be lighter since it no longer has to confront nukes?

If so...

I was thinking just blast a bunch of those and you could scream through the air plasma along a curve and just coast into orbit.... maybe with more bomb fuel left than if you used chemicals?

Yeah the nose would ablate some, but that should not be a showstopper. Just use tungsten tip or something else heat resistant.

 

This idea is basically like an air augmented rocket on steroids... since it is getting a good deal of it's power from the air blast anyway.

 

Only difference is exploding bombs and pusher plates.

Edited by Spacescifi
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44 minutes ago, Spacescifi said:

I was thinking what if the thermobaric bomb was one nuke level blast?

A baby nuke. An embryonuke.

46 minutes ago, Spacescifi said:

Maybe the pusher plate can be lighter since it no longer has to confront nukes?

I was thinking just blast a bunch of those

As it was told not once, the Orion design is based on the directed hit of a plasma jet, not on just a blast.

The fuel-air bombs are to uniformly raise the pressure inside the dedicated volume. Their mechanical abilitiy is secondary and poor, they are to squish the soft.

Also, all needed air should be taken to space, as it lacks it.

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Nuclear bonds are simply vastly more energy-dense than chemical bonds. Project Orion was not proposed because exploding bombs behind your ship is a great way to provide thrust. It was proposed because nuclear power is necessary to get anywhere beyond maybe Mars or Venus. A "non-nuclear Orion" misses the ENTIRE point.

Besides, fuel/air bombs work because the bomb only supplies the fuel. The oxygen is already there. That is not the situation in space.

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How big was the Lebanon explosion again?  2kt?   Something like that.    And that was an entire dockside warehouse.    Getting non nuclear munitions up to the scale of nuclear explosions requires including the logistics of bulk freighters.     

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Orion was an "elegant in it's simplicity" workaround to the problems of making a nuclear engine. "Open cycle" engines, using your depleted power source as reaction mass, are vastly more effective than "closed cycle" ones, like NERV (a reactor heats propellant intead of burning it), the electric-pump rutherford (which only uses the batteries as a "preburner", and still has to dump batteries on the way up), and Ion engines (which use electricity to propell ions at frankly absurd velocities to get efficency, but not much actual thrust)

Chemical rockets are almost all open cycle, burning the propellant in a chamber and letting a jet of the combustion product escape to produce thrust. You cant detonate a nuclear bomb inside a combustion chamber, but Orion showed that you can afford to waste a lot of the potential nuclear blast, if you can run open cycle, even without the chamber to direct the blast into a single jet. (and there was some optimization, that basically turned the bomb into two jets, so they managed to get almost 50% efficency out of it)

But the better open-cycle nuclear engine design is the NSWR, which achieves criticallity in the propellant, AT the throat, so the blast happens in the nozzle where it can be directed.

Both NSWR and Orion have the problem of spewing radioactive waste over your launchpad and the entire launch track, of course. That's the core problem with open cycle nuclear engines. Noone cares when a hydrogen/oxygen rocket spews H2O gas over the launch track, although some more exotic propellants also have concerns. But none of those concerns match that of nuclear waste.

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7 hours ago, Spacescifi said:

 

Only difference is exploding bombs and pusher plates

I think you are not leaning into this enough.  

Take a pinch of gunpowder.  Touch a match to it you get a flash of light and smoke.  Package that pinch up tight and you get a bang... Put the tightly packed pinch in a tube with one open side and you get a rocket.

The bang seems big with a nuke - but the energy is being released in all directions... But you want to put a pusher plate on one side to capture some of that energy and get it to do work?  Why? ... Because back in the day someone came up with it as an idea for getting work out of super tightly packaged combustion they couldn't control. 

So lean into this - have your sci-fi guys figure out how to not just have a nuclear bomb, but instead a nuclear candle.  Get a burn - not a bang. 

 

Zoom. 

Edited by JoeSchmuckatelli
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Or, you know, lean into scifi even harder, and have some kind of unobtanium that is even more powerful, and cant be released in smaller amounts. Hyperspacial core tap to a higher energy dimension, which can only be opened for a few fractions of a second but releases enough energy to require a shock absorption plate.

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Here; use this...

(Although, first off - are you familiar with 'corning' of gunpowder?) 

You have a nice big sci-fi ship with safe storage for corned, granular fissionables. When it's time to go zoom, you rapidly convey the solid fuel to the engine where through lasers and really strong magnets it all gets so hot and dense that the reaction kicks off and you get the super fast burn of fission, albeit controlled and the magnets can also define the nozzle so instead of the bang you get a whoosh.

When you want to go faster, feed more fissionables, when you want to stop... Cut the feed. 

So easy 

 

Edited by JoeSchmuckatelli
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I think this solution may be useful if you want to put your vessel on a suborbital trajectory, maybe with an apoapsis of 10-20 meters, and don't care too much about making a soft landing. The utility of such a flight may be limited, but it'd be wicked cool to watch from a safe distance.

Edited by Codraroll
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2 minutes ago, Codraroll said:

I think this solution may be useful if you want to put your vessel on a suborbital trajectory, maybe with an apoapsis of 10-20 meters, and don't care too much about making a soft landing. The utility of such a flight may be limited, but it'd be wicked cool to watch from a safe distance.

I can't find it... but I'm pretty sure Mythbusters did an episode where an explosion slowed a skydiver or something to make a "survivable" landing.  

But in a sci-fi series... this would make for an interesting landing method for a troop carrying drop ship.   Big boom clears out the immediate area around the ship, giving the troops an instant clear perimeter. 

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1 hour ago, Codraroll said:

I think this solution may be useful if you want to put your vessel on a suborbital trajectory, maybe with an apoapsis of 10-20 meters, and don't care too much about making a soft landing. The utility of such a flight may be limited, but it'd be wicked cool to watch from a safe distance.

 

I was thinking that if someone designed a non-nuclear Orion IRL, at the very least it would give raw test data for working out the kinks of a nuclear Orion.

 

Or you could send a non-nuke orion up to orbit, boost nukes up to load it with via rockets after, and go across the solar system from there.

 

Ironically I actually think a non-nuclear orion could even work as an SSTO in real life or scifi. You just crater your launch site, but with landings you could slow farther away for safer landings. Since there is no radiation, nonnuclear Orions have more flexibility and utility for how you use them in maneuvering in atmosphere.

It will just suffer nose ablation due to screaming through the thicker part of the atmosphere to gain speed to coast to orbit.

Edited by Spacescifi
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12 minutes ago, Spacescifi said:

Ironically I actually think a non-nuclear orion could even work as an SSTO in real life or scifi.

No, it will not work.

The maximum detonation wave speed in an ideal thermobaric explosive is around 1.8 km/s. This means that once you are moving at 1.8 km/s, blowing up more fuel-air bombs behind you won’t do anything, because you’re moving away faster than the shockwave can reach you.

A thermobaric Orion will not get you anywhere.

12 minutes ago, Spacescifi said:

You just crater your launch site, but with landings you could slow farther away for safer landings. Since there is no radiation, nonnuclear Orions have more flexibility and utility for how you use them in maneuvering in atmosphere.

There will NEVER be an occasion or situation where a "non-nuclear Orion" makes ANY sense. Never.

Thermobaric explosives are effective because they are able to use atmospheric oxygen to support detonation, rather than depending on an oxidizer chemical premixed with the reducer chemical to create the explosive. Since oxidizer makes up over half the weight of an explosive, you can get more kaboom per kilogram (pow per pound in freedom units) if you can use atmospheric oxygen instead.

But if you're trying to propel a vehicle and you want to use atmospheric oxygen, you use a jet engine.

A pusher-plate system is WILDLY inefficient. The ONLY reason for a pusher-plate is if you cannot control the release of energy from your engine, which is ONLY applicable when using nukes.

12 minutes ago, Spacescifi said:

It will just suffer nose ablation due to screaming through the thicker part of the atmosphere to gain speed to coast to orbit.

If you want to use atmospheric oxygen to help you get to orbit, try Skylon.

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The *only* value of an Orion style drive is allowing the use of a super-dense energy medium(nuclear bonds) using the most primitive technology possible.

The *only* reason to use a pusher-plate is if the minimum energy release of your fuel is too high to be able to contain it in a combustion chamber(like the need for a fission fuel to go super-critical).

While nuclear would indeed provide much better isp than modern rocket engines, that is not the only option.

For something currently under development that may provide a much higher ISP, take a look at https://en.wikipedia.org/wiki/Rotating_detonation_engine

Right now, we are heating up the exhaust and then letting it expand through a rocket nozzle to get thrust.  Detonations allow expelling exhaust at super-sonic speeds which is not possible with normal expansion engines, and thus allow a higher theoretical maximum ISP per fuel(which may or may not even be a thing with detonations instead of conflagrations)

 

 

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1 hour ago, Terwin said:

The *only* value of an Orion style drive is allowing the use of a super-dense energy medium(nuclear bonds) using the most primitive technology possible.

The *only* reason to use a pusher-plate is if the minimum energy release of your fuel is too high to be able to contain it in a combustion chamber(like the need for a fission fuel to go super-critical).

While nuclear would indeed provide much better isp than modern rocket engines, that is not the only option.

For something currently under development that may provide a much higher ISP, take a look at https://en.wikipedia.org/wiki/Rotating_detonation_engine

Right now, we are heating up the exhaust and then letting it expand through a rocket nozzle to get thrust.  Detonations allow expelling exhaust at super-sonic speeds which is not possible with normal expansion engines, and thus allow a higher theoretical maximum ISP per fuel(which may or may not even be a thing with detonations instead of conflagrations)

This underestimates a few advantages of the Orion.  Currently planed nuclear rockets use the energy from a reactor, but have to supply the mass/momentum from elsewhere.  An Orion gets the momentum from the blast (plasma?  photons?  neutrons?) itself, compressing the pusher plate and delivering the momentum to the Orion.  Other systems either accelerate light (hydrogen) reaction mass by heating it and propelling it out (with a maximum Isp ~1000s-ish) or using electromagnetism to accelerate heavier atoms (ideally the unbelievably expensive xenon, possibly the less expensive krypton, or even the extremely common (moreso than CO2), but lighter argon).  While these ionic methods have extreme Isp (to the point there's little point in making it higher, unless concentrating on cheaper atoms), the thrust is miserable.  The KSP models have extra-high thrust (no, really) as you can only increase time by a factor of 4 while your thrusters are firing.

And as usual, this whole thread could be avoided if Spacescifi could learn the foundation of rocket science, the rocket equation.  There's this nifty little game that's the ideal teaching tool for it...

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31 minutes ago, JoeSchmuckatelli said:

Which is why I specified FRICKIN LAZERS in my solution, above!

I was thinking about a cord, but laser is nice, too.

Btw if the pancake is protected from the aft side with a metal plate, it's both anti-detonation protection and shockwave reflector.

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