
Nuclear Pulse Propulsion – Orion and Beyond (2000) [pdf] - maverick_iceman
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000096503.pdf
======
Symmetry
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...](https://www.nasa.gov/content/pulsed-fission-fusion-puff-propulsion-
system)

~~~
maverick_iceman
What's the Isp of this method?

~~~
Symmetry
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...](http://hopefullyintersting.blogspot.com/2015/04/rockets-vi-very-
nuclear-rockets.html)

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sillysaurus3
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.

~~~
andygates
> 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.

~~~
berntb
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.

~~~
arethuza
The "directed" bomb designs used tungsten - in "The Curve of Binding Energy" I
seem to remember there is a comment that they were spectacularly good at
digging tunnels but I don't know if that was a theoretical prediction or an
empirical result.

~~~
madaxe_again
If you consider that it was contemporaneous with plowshare, that makes sense -
likely a degree of shared research.

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luckystarr
Nuclear salt-water rockets! [https://en.wikipedia.org/wiki/Nuclear_salt-
water_rocket](https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket)

Powerful, fast, intriguing and disgusting. :)

~~~
Tuna-Fish
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?

~~~
Symmetry
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#...](http://www.projectrho.com/public_html/rocket/enginelist.php#id
--Nuclear_Thermal--Gas_Core--Open_Cycle)

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jharohit
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...](https://www.nasa.gov/sites/default/files/atoms/files/roadmap_to_interstellar_flight_tagged.pdf)

~~~
sprucely
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/](https://breakthroughinitiatives.org/)

~~~
jharohit
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!

~~~
IndianAstronaut
We are a long ways from becoming space faring. For the cost of sending one
human to Mars, we could send ten rovers to Mars.

~~~
XorNot
Not if Elon Musk gets his way. If the cost profile works out, sending a human
will be cheaper then sending a robot.

~~~
grkvlt
Even then, we can still send rovers more cost effectively than people! You can
throw away the life support mechanisms, and so on, and get 550 tons of pure
mars rover in your interplanetary transport. At ~800kg for a curiosity-level
rover that gives about 600 rovers, instead of 100 people.

What to do with your 600 curiosity rovers on Mars is left as an exercise...

~~~
elsonrodriguez
The Curiosity rover has driven 9 miles in a little over four years on Mars.

The Lunar Rover that came with Apollo 17 drove 22 miles in a little over 4
HOURS.

As it turns out, humans are the best robots.

~~~
grkvlt
Yes, but with my super-rover-transporter system, we can cover 5,400 miles in
the same time, with the 600 rovers. I'm envisaging a sort of airbag deployment
system (like pathfinder) coupled with a dispenser system that fires a rover
out every few minutes as the ship orbits the planet, for optimal coverage.

~~~
elsonrodriguez
But to what end? Bigger and better probes? Finer and finer data points?

We can send probes forever, but when do WE go?

My underlying point is that we have enough data to start making attempts at
settling Mars, and once we're there, we'll do more science and exploration
than any existing robot can. If you doubt that, then show me a robot that can
perform an archeological dig on a fossil site without destroying half of the
fossils.

------
moseandre
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.

~~~
wyager
>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.

~~~
simonh
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.

~~~
snrplfth
Even if you had effective nuclear pulse propulsion, you'd still need reusable
chemical launchers to get them off the surface of Earth. Nuclear pulse engines
are generally not something that you start up inside an atmosphere, for both
safety and efficiency reasons.

~~~
simonh
The post I was responding to strongly implied using these for launches.

> ..It would also allow us to practically ship up enough materials to build
> self-sustaining habitats in near space..

------
fulafel
There's also this great book about Orion:
[https://www.goodreads.com/book/show/21243.Project_Orion](https://www.goodreads.com/book/show/21243.Project_Orion)

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tdy721
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](https://en.wikipedia.org/wiki/NERVA)

~~~
jharohit
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.

------
ramgorur
"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".

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DrNuke
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.

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

~~~
saulrh
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.

~~~
askvictor
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?

~~~
Pinckney
You add a significant amount of mass to the bombs to act as propellant. I
don't know offhand what fraction is typical for Orion designs.

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

~~~
jharohit
Anti-matter is produced at CERN for study
[https://home.cern/topics/antimatter](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
Is it stable enough to survive a space launch?

~~~
jharohit
don't think so. I am guessing you would need really strong magnetic fields to
contain the anti-matter.

~~~
dogma1138
Magnetic fields aren't the only issue here.

You won't be able to store large amounts of it since quantum tunneling will
become a statistical problem.

~~~
witty_username
Could you explain? How would quantum tunneling of antimatter be a problem?

The probability of quantum tunneling is exponential so adding a little more
separation or reducing the energy can change the probability from 10^-1 to
10^-100.

