
NASA Proposal to Revive Nuclear Thermal Space Propulsion Development - Anon84
http://nextbigfuture.com/2012/08/nasa-proposal-to-revive-nuclear-thermal.html
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Wingman4l7
The 1950s/60s NERVA program that the blog post mentions in passing:
<http://en.wikipedia.org/wiki/NERVA>

Project Rover: <http://en.wikipedia.org/wiki/Project_Rover>

For hard scifi buffs, check out Stephen Baxter's space-program-alt-hist novel
_Voyage_ , where (among other things) NERVA is revived for a manned Mars shot.

I'm kinda surprised to see this; I thought that public acceptance of nuclear-
related programs would be at a low, after Fukushima. Heck, I remember when
people were kicking up a fuss over Cassini's RTG back in 1997.

Are we going to revive Project Orion next?
[http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propul...](http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29)

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DeepDuh
All I ever heard before was Project Orion, but after reading about Project
Rover, I don't understand why you would want Orion's design. Isn't Rover
superior in every way? It appears to me that Orion uses a much smaller
fraction of the released nuclear energy, leading to a bigger waste of
resources and smaller payload to total weight ratio. Furthermore it's harder
to use Rover as a weapon, but maybe this would be a minus for some of the
potential investors.

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comicjk
Orion-type designs are less efficient than nuclear thermal, but have orders of
magnitude more energy to work with. Nuclear bombs are pretty unbeatable for
raw power.

There is a safer and cheaper way to harness nuclear bombs for heavy lifting,
though, as long as you don't mind a very bumpy ride for the cargo: the Verne
Gun ([http://nextbigfuture.com/2010/03/150-kiloton-nuclear-
verne-g...](http://nextbigfuture.com/2010/03/150-kiloton-nuclear-verne-
gun.html)).

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DeepDuh
Thanks for the infos, it makes a bit more sense to me now. I'm still trying to
understand as a layman with engineering background, so I'm pulling a few
numbers out of my ass now..

Let's say we have a unit power output of P_therm and P_bomb (in case of the
bomb its time plot should look close to dirac pulses while P_thermal should
look like a flat line), we have efficiencies eps_therm, eps_bomb and we have
the mass of the propellant systems m_ohterm, m_ohbomb.

I'm assuming P_thermal to be 1e+7W (1/100 of a powerplant), P_bomb = 0.15
kiloton per second ~= 6e+11W => lets make that 1e+12. Efficiency: eps_therm =
1'000 * eps_bomb Mass: m_therm = 10 * m_bomb

so if these numbers work out the bombs give you about 10^5 times the power
output of the furnace, deliver 10x the power to the ship (efficiency
differences) and yield about 100x the effect per unit of mass.

hmmmm... I think I'm starting to get it ;). However here's the thing: I'm
imagining that the furnaces can be scaled up much easier than the orion
design. You can just make them bigger up to a certain point and when that
doesn't help anymore you can strap them together. You can't really strap
together the orion propellers because it would become incredibly susceptible
to timing (one bomb goes off 1ms earlier and you end up spiraling everyone to
death with 20G acceleration or so :D ).

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dalke
As I recall, Orion-style craft scales up well. Ahh, the Wikipedia article says
"physicist Ted Taylor showed that with the right designs for explosives, the
amount of fissionables used on launch was close to constant for every size of
Orion from 2,000 tons to 8,000,000 tons." The original design team worked on
4,000 and 10,000 ton vehicles and the "Super" was an 8 million ton
interstellar vehicle.

The timing isn't so critical. It could handle a 10ms timing variation, and a
misfire.

George Dyson's book, Project Orion, is well written. That being the son of
Freeman Dyson, who worked on the project.

~~~
DeepDuh
It sure is a fascinating wiki. Judging by it it wasn't that far from being
implemented, which is mind boggling.

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pjscott
The part of this that surprised me is that the amount of radioactive fission
products in the reactor is fairly insignificant for the first part of a
mission -- a nuclear thermal rocket can be well out of Earth's orbit before
it's as radioactive as the RTG that powers the Curiosity rover.

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DeepDuh
Can someone ELI5 how that works?

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InclinedPlane
Uranium or Plutonium isn't that dangerous, it's fission byproducts that are
super dangerous, and they only build up over time.

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arethuza
I'm not sure I'd call plutonium metal "not that dangerous" - it is pretty
toxic, can catch fire spontaneously and once if does catch fire you have to be
_really_ careful trying to put the fire out. There is an excellent book on the
history of the Rocky Flats nuclear weapons plant near Denver that describes
some of the problems with handling plutonium on an industrial scale:

[http://www.amazon.com/Making-Real-Killing-Rocky-
Nuclear/dp/0...](http://www.amazon.com/Making-Real-Killing-Rocky-
Nuclear/dp/0826327982)

Edit: Of course these things are relative. I guess compared to chemicals like
chlorine trifluoride or FOOF it is pretty tame from a _chemical_ perspective:

[http://pipeline.corante.com/archives/2008/02/26/sand_wont_sa...](http://pipeline.corante.com/archives/2008/02/26/sand_wont_save_you_this_time.php)

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InclinedPlane
Well yes. What I meant to say was that in trace amounts in the atmosphere
Plutonium isn't terribly dangerous. When you're working with bulk metal there
are heavy metal toxicity and radioactivity concerns, of course, and if you're
working with powder or fines then that can be particularly dangerous in terms
of radioactivity exposure (because Plutonium in your lungs is pretty much
where it can do the most damage).

But compared to fission byproducts like I-131 or Sr-90 which are both crazy
radioactive and eagerly taken up by your body and placed into your bones and
your thyroid, Plutonium barely registers.

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nextbigfuture
The presentation was made at the NASA Future on space operations workshops

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comicjk
Very smart to link nuclear thermal technology to manned Mars missions. It
would be wonderful if public enthusiasm after Curiosity makes further
development in this area possible.

I want my spaceship!

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rbanffy
I'll start considering links to nextbigfuture as blogspam unless they contain
links to the presentations (and referring material) from NASA servers.

edit: Sorry. I mistook the first link for a cluster of tags.

I'd like to offer help making the layout clearer. I made a couple observations
on the Disqus discussion on the page.

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nextbigfuture
The first link is to the 24 page presentation from the NASA FISO (future in
space operations archive). What is your problem ?

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rbanffy
I'm very sorry. I mistook the first link for a cluster of tags.

Can I help you with the site layout? We could make it much clearer. I think I
just proved it's not idiot proof. :-(

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wazoox
It's not clear that this proposal is actually coming from NASA. That would be
great news nonetheless.

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misterfusion
Nuclear propulsion will open vast horizons to the future of mankind. I think
the best option will be fusion-powered plasma turbines.
<http://youtu.be/ro5-QYqqxzM>

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rektide
I was going to say it looks like a Bussard IEC (Inertial Electrostatic
Containment) with a VASIMR (Variable Specific Impulse Magnetoplasma Rocket)
tacked on the back, but there's a dozen things about the IEC that they're
talking that seem different, and they spent little enough time detailing the
thruster that comparisons v.s. VASIMR are a little tricky.

Lol, wikipedia: <http://en.wikipedia.org/wiki/Polywell>
<http://en.wikipedia.org/wiki/VASIMR>

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misterfusion
There are a lot of key differences. Bussard IEC can be characterized by
recirculation of electrons, virtual cathode, "wiffleball" magnetic
compression. VASIMR can be characterized by helicon antenna, single phase
instead of multiphase.

