Nuclear Pulse Propulsion – Orion and Beyond (2000) [pdf]

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000096503.pdf

86 99 10 years ago

ntrs.nasa.gov

Happy to see this getting some attention. It's seemed like one of the only viable propulsion methods for interstellar purposes, though nuclear is unfashionable at the moment.

I remember seeing a chart showing that it was possible to reach other stars using a technique like this. Unfortunately the problem is slowing down. You could get there, but you'd be going too fast to stop. And since the more fuel you carry, the harder it is to reach that speed, it ends up becoming completely impractical to carry enough fuel to both get there and slow down.

Maybe it'd be viable to stop by smashing into a planet, but it's hard for anything to survive that kind of impact force.

sien2• 10 years ago

This was considered by project Orion.

Basically you turn the vehicle around and use the propulsion to slow you down. It would use a heap of fuel to do this but it was possible.

Edit, also, great find of this by the poster.

api2• 10 years ago

But since you already used a bunch of your pulse propellant during acceleration, this is partly compensated for by the vehicle weighing less.

sillysaurus33• 10 years ago

In order to have fuel to do that, you'd need to accelerate it to begin with. It ends up being an exponential increase in the quantity of fuel required, far more than could be carried.

The chart from the paper was pretty convincing. I'll see if I can dig it up. Making the explosions more efficient can only get you so far. I'd prefer to be optimistic about it, but the math was showing that even with an ideal ability to convert mass into energy, it would require too much fuel, to put it mildly.

narag• 10 years ago

I remember seeing a chart showing that it was possible to reach other stars using a technique like this. Unfortunately the problem is slowing down.

So this is like being concerned how you will spend all that money, once you make it :-)

There's a lot of discussion on interestellar travel, but "we" have almost frozen solar system travel. Yes, there are very nice probes out there doing important work, but manned vehicles are limited to keep ISS's lights on.

The "impossible" tech needed to reach the stars will most probably be discovered or refined while conquering the solar system.

Big sailing ships were developed along four centuries of sailing. The analogy may not be perfect, but I think it's eye opening.

triplesec• 10 years ago

I agree with you in innovation terms, but there's a big economic difference: sailing used free energy and therefore could be developed over the long term by many actors. There are huge energy cost barriers to solar system travel which require bigger bets on economic return to be viable

andygates• 10 years ago

nuclear is unfashionable at the moment

It's more than that - this isn't just hippies, it's every major power on the planet. To fly Orion you have to put hundreds of nuclear explosives in orbit and pinky-swear that you're not going to use them to obliterate your enemies. Nobody is going to accept that.

Orion's a fun paper rocket but will never be more. Engineers and they "yay nukes!" crowd will drag it out every couple of months for a repost, though.

berntb5• 10 years ago

If you read the book (by Freeman Dyson's son) or even the wikipedia page, you'd know the bombs were quite specialized. And it would certainly be possible to allow some verification (the trigger would not need inspection, that would probably be the really sensitive part, from a technology secrets point of view).

[Edit: The bombs would be directed, throwing light weight molecules up against the pusher plate.]

Also, there is no direct lack of ways to distribute nuclear devices to capitals today, for the countries able to build an Orion. Compare that with the possibility to launch enough material to e.g. start on getting an industrial infrastructure going outside the atmosphere.

jessriedel• 10 years ago

To fly Orion you have to put hundreds of nuclear explosives in orbit and pinky-swear that you're not going to use them to obliterate your enemies.

To reiterate berntb's point: Every nation who has the ability to do this already has ICBMs that can deliver nukes anywhere on the planet in 20 minutes. So what difference does this make?

api2• 10 years ago

Even worse: the EMP from an Orion launch would fry a lot of satellites. It's not a practical design for use anywhere near... anything.

You could launch one from the far side of the Moon, but if you have that kind of space presence there are better engine designs. Some have been posted elsewhere in this thread.

maverick_iceman5• 10 years ago

Anything that can accelerate a starship to a velocity of ~0.1c can have devastating consequences if pointed to earth. Just like planes can be used to destroy skyscrapers. Chicken littles notwithstanding, having a much faster mode of transport is worth the risk.

tdy721• 10 years ago

I really love this stuff, this is a little more out there. (interstellar travel and all...) But I really believe that Nuclear power will be required to continue to explore our Solar System. Nuclear Thermal Rockets like Nerva[1] just seem like the only way to really colonize Mars in a sane way. I'm surprised that Elon Musk thinks it can happen with chemical rockets (and big tanks of LOX to keep cool and haul through the void).

[1] https://en.wikipedia.org/wiki/NERVA

jharohit8• 10 years ago

Well chemical rockets are at a stage where all it needs is scaling up to get more power. But I do agree with you, the complexity and sizes needed makes you wonder why waste so much effort on some technology which has inherent physical limits in terms of energy derived. Why not spend that money and effort on accelerating other forms of propulsion techniques (like nuclear) within the same timescales?

We need another Manhattan Project for space tech.

jharohit8• 10 years ago

What do you guys think of Laser sails & laser-based propulsion methods? The science exists now, seems like its only an engineering challenge.

Phil Lubin has a paper on it as well https://www.nasa.gov/sites/default/files/atoms/files/roadmap...

sprucely• 10 years ago

That's what Breakthrough Starshot[1] is about, although scaled down to very small probes. I like the probe concept. If we really don't want all our eggs in this one basket, it seems to make more sense to put effort towards tech that can spread our seeds (whatever that may be) rather than humans physically traveling.

[1] https://breakthroughinitiatives.org/

jharohit8• 10 years ago

Exactly - i think there should be more companies & organizations working towards pushing this. To become space-faring, we need to get from 1ev per bond of molecule level of energies obtained from chemical to 1GeV levels atleast!

jharohit8• 10 years ago

Plus, mass driver approach is not the only way to use lasers right? Light can remotely power systems, heat solid propellants to extremely high temperature thus getting better thrusts, etc. So the technology, if scaled up correctly, can be used for large scale transport systems too.

moseandre2• 10 years ago

Please read Freeman Dysons's "Disturbing The Universe".

This book is autobiographical and Dyson explains his arc of passion for nuclear propulsion and Orion.

His strongest statement in this book is some deep respect for a biological scientist who, after seeing declassified army training manuals on chemical and biological warfare, supposedly discouraged the entire western hemisphere from further develomepment.

This kind of nuclear research is, thankfully, over.

jharohit8• 10 years ago

I would rather classify that as "unfortunate". Yes there are obviously biological harms in radiation exposure but that is what science & engineering is for. We know the power of nuclear energy so in order to harvest it, the right thinking should have been like "How can we safely extract it so that it does harm people in the mix?" rather than "Oh its harmful to humans so obviously we should give up and not use it".

Current fission startups are working on versions of reactors which eliminate most of the harmful byproducts in the process.

moseandre2• 10 years ago

I'm not sure all of the opposition to nuclear research is about dangerous byproducts from the typical situation(s). It is about the improbable problematic situation which lead to exponential disaster that are scary, and, even if improbable, inevitable...

wyager• 10 years ago

This kind of nuclear research is, thankfully, over.

Nuclear pulse propulsion is the only currently viable technology that could be used to make humans an interstellar species. It would also allow us to practically ship up enough materials to build self-sustaining habitats in near space. It is extremely unfortunate that this kind of research is over.

Fun fact: the background radiation levels introduced by nuclear propulsion would actually have a very slight positive health effect on humans according to more accurate radiation hormesis models, rather than the very small negative effects suggested by more naive no threshold models.

adrianN2• 10 years ago

I agree that nuclear pulse propulsion would be awesome to have. However, as far as I know radiation hormesis is a hypothesis that is still disputed.

simonh4• 10 years ago

On the other hand if we'd gone all-in on nuclear pulse launchers, there would have been no incentive for companies like SpaceX and Blue Origin to develop reusable conventional rockets which will hopefully achieve the same result at lower environmental and perhaps also financial cost.

mikeash2• 10 years ago

Radiation hormesis models aren't "more accurate." The long-term effects of small amounts of radiation are simply not well understood. It could be good, it could be bad, it could be neutral.

The far bigger problem for launching Orion from Earth is the electromagnetic pulse frying every satellite above the horizon and a bunch of stuff on the ground.

fulafel• 10 years ago

There's also this great book about Orion: https://www.goodreads.com/book/show/21243.Project_Orion

jaunkst• 10 years ago

If only we could produce anti matter. A tiny amount would provide a fuel source viable for deep space exploration.

jharohit8• 10 years ago

Anti-matter is produced at CERN for study https://home.cern/topics/antimatter.

The problem is not production of it but the economy of producing it. It's still very costly to produce and then to build and engine around it which uses the energy efficiently is still at least 10-15 years. But do believe that the time to start actively looking into it is NOW.

flukus• 10 years ago

Is it stable enough to survive a space launch?

berntb5• 10 years ago

When discussing antimatter for propulsion, it might be worth checking out Robert L Forward. I saw the expression that he took the "giggle factor" out of the subject. :-)

I found this overview, discussing a bit about the antimatter research:

http://www.enthea.org/docs/Forward-Emerging-Technologies-Fut...

Symmetry4• 10 years ago

As a practical matter most of the byproducts of antimatter annihilation aren't amenable to being directed out the rear of a spacecraft by a nozzle, magnetic or otherwise. So the maximum theoretical efficiency is possibly better with advanced fusion drives than with antimatter.

ramgorur• 10 years ago

"orion's death" (page 6-7) says it all, we might be able to see something like orion by today if there were no ban on the nuclear tests, and there wouldn't be any "ban" if there were no "nuclear attack in 1945".

askvictor2• 10 years ago

Eli5: how does a nuclear explosion create a change in velocity for the spacecraft?

saulrh• 10 years ago

Sort of like a sailboat, except the wind is the vaporized material from the nuke. The nuke explodes, throwing a ton of mass and energy in every direction. The rocket uses a sail or pusher plate to catch part of that mass and energy, which carries it forward.

askvictor2• 10 years ago

The mass is pretty tiny ( smaller than the ejected fuel pellet); I presume it's the fact it has huge velocity, hence huge momentum? What about photons; do they have the same effect as other particles, or is there a different effect?

avmich• 10 years ago

The explosion throws the products of the explosion - mostly plasma - into all directions. The spaceship is nearby, so some of the plasma hits the ship, which is hiding behind a strong plate. Plasma transfers momentum to the ship.

DrNuke• 10 years ago

Think of this as a startup case for 2016: an exciting idea on paper with a very improbable, cumbersome and practically impossible execution = non-viable, fail fast, goodbye.

luckystarr• 10 years ago

Nuclear salt-water rockets! https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

Powerful, fast, intriguing and disgusting. :)

Tuna-Fish• 10 years ago

Project orion has the name recognition, but nuclear salt water rockets would just be a much better use of the same amount of fissiles. Maybe we should start reposting the wikipedia link every month until people remember mr. Zubrin's creations more than project Orion?

Pinckney6• 10 years ago

The big advantage of Orion is that we're reasonably confident it would work, and could probably build one within the decade with a serious effort. Zubrin's NSW rocket, on the other hand, falls into the "hasn't yet been conclusively proved impossible" category. We're not sure if we can control the reaction, and we're not sure how much heat would be transferred to the rocket if we can.

maverick_iceman5• 10 years ago

Orion would have exhaust velocity ~1000-10000km/s. Compare that to NSWR's 66km/s. NSWR seems fast compared to today's chemical rockets but it's nothing compared to Orion.

Symmetry4• 10 years ago

It's hard to say which is a more efficient use of fissiles. It's easier to burn up all your fuels in the context of an explosion as in Orion than in a saltwater rocket. On the other hand by bulking out the fuel with water to form a larger mass of propellant the saltwater uses it's energy more efficiently at the cost of lower ISP.

But really, if we're willing to leak radioactive byproducts I think an open cycle gas core might be the best bet in terms of not-yet-developed rockets.

http://www.projectrho.com/public_html/rocket/enginelist.php#...

JumpCrisscross• 10 years ago

An issue with NSWR systems is testing. If you test on the ground, you either eject fissile material into the atmosphere or have to build a very expensive containment and scrubbing system.

These systems may be post orbital assembly technologies.

Symmetry4• 10 years ago

I think I like the recent work on pulsed fission-fusion better. Basically you have a normal z-pinch fusion system but surround the fusing hydrogen with U238. It absorbs the fast neutrons from the fusion, fissions, and creates more heat driving the fusion. There's some radioactive waste flying out the nozzle but if you're already in space that's not a huge problem.

On the upside, people aren't going to get nervous about nuclear weapons in space since you can't trigger the fuel pellets outside the engine. And you don't need a massive pusher plate, you just direct the charged plasma with magnetic fields. And that means you can wait to turn this on until you're in orbit and avoid creating any fallout on Earth.

https://www.nasa.gov/content/pulsed-fission-fusion-puff-prop...

maverick_iceman5• 10 years ago

What's the Isp of this method?

Symmetry4• 10 years ago

The first paper mentions 19,400 seconds at one point; versus 450 for hydrolox and 3100 for Dawn's ion drive. I did a blog posts on the theoretical limit on this sort of drive a while ago, using propellant velocity instead of ISP.

http://hopefullyintersting.blogspot.com/2015/04/rockets-vi-v...

Nuclear Pulse Propulsion – Orion and Beyond (2000) [pdf]

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