
NASA Wants to Send Nuclear Rockets to the Moon and Mars - n0pe_p0pe
https://www.wired.com/story/nasa-wants-to-send-nuclear-rockets-to-the-moon-and-mars/
======
DoctorOetker
what happens at the end of such a trip, when the propellant is exhausted, and
can no longer evaporatively cool the core?

it has to contain enough propellant to come back to Earth orbit to refuel the
propellant coolant?

even if the core is throttled to its lowest levels, it will still produce heat
in the vacuum of space? or will radiative cooling balance the remaining
production of heat?

~~~
simonh
You do what you would on a terrestrial reactor, and shut down the reactor e.g.
by using control rods, or pulling out fuel rods to shut down the chain
reaction. These wouldn't be simple radiothermal devices, but proper actively
managed reactor cores.

Having said that you absolutely would need active cooling even in a 'shut
down' state, probably by circulating a cooling fluid to radiator fins. You
might use the same fluid as the propellant or might not. In the former case
sure, you wouldn't be able to use all of it as propellant.

~~~
NohatCoder
Absolutely not, in space you have the option of jettisoning the core, carrying
coolant for a controlled shut down is a waste of weight. You might even go as
far as having 4 disposable cores, one for each acceleration stage.

~~~
dogma1138
Not sure why this is being downvoted jettison the core would likely be the go-
to solution you can put into a stable orbit or even set on course with the sun
and let it burn off...

There is no much need for a complex control mechanism in fact keeping those
core as orbital modules on mars would likely allow you to skip many of the
complications of having a complex control system to prevent a run away effect
and modulate power output no one really cares if the core would go critical
even at low orbit on Mars as there is so much radiation there from natural
sources anyhow.

If the core goes critical mid way then either have a fallback core or just
jettison it and wait for a rescue mission.

The vessels would likely have enough supplies for such occasions and as far as
risk to the crew goes nuclear propulsion in space is much less dangerous than
chemical propellants that can actually explode.

With a nuclear core you can safely vent hydrogen and xenon to space not
worrying that much about radiation or long term contamination the cores can be
more or less exposed with large fin stacks for radiative cooling.

~~~
kwoff
"set on course with the sun and let it burn off" \-
[https://laughingsquid.com/why-it-is-more-difficult-to-
crash-...](https://laughingsquid.com/why-it-is-more-difficult-to-crash-into-
the-sun-than-leave-the-solar-system/)

------
sq_
> which will almost certainly be used on any crewed mission to Mars.

This is interesting. I hadn't seen anything about NASA plans to get humans to
Mars requiring nuclear-thermal propulsion. Does NASA even currently have a
serious plan for Mars missions with the whole Artemis thing going on?

~~~
ceejayoz
They branded Artemis as part of a larger "Moon to Mars" plan, with logo and
all. [https://www.nasa.gov/moontomars/](https://www.nasa.gov/moontomars/)

~~~
sq_
Interesting. I'm kinda down on Artemis overall, as it seems like the whole
thing is getting bogged down in political maneuvering, as usual.

NASA keeps saying it's more than boots on the ground, but all the plans they
announce seem to be boots on the ground or overly complicated paths to the
surface meant to please contractors.

This gem of a line from this week's Orbital Index kinda sums up why I'm
preparing for disappointment:

>"Meanwhile, contractors ( _cough_ Boeing? _cough_ ) are pushing for the
Gateway plan to be nixed in favor of… The Exploration Upper Stage, a large
interplanetary upper stage (launched on SLS Block 1B) in development by (wait
for it) Boeing."

Boeing and the SLS have taken _forever_ already, and the version that _may_
launch soonish isn't even the "real" SLS.

~~~
ceejayoz
I'm skeptical of any human exploration plans NASA has beyond 2-4 years or so.
Anything more and the next President winds up nixing it to put their own stamp
on things.

My money's on a commercial program like they one they've been doing for ISS
resupply.

~~~
sq_
> My money's on a commercial program like they one they've been doing for ISS
> resupply.

Fully agree. If I had to bet right now, I would guess that SpaceX will get
humans to the moon before NASA does. They’re moving so quickly on Starship and
seem extremely determined to prove their new rocket.

------
Arrezz
How big is the added risk of toxic waste? I'm not sure how much waste is
produced in relation to propulsion energy given but it must be quite small?
And I imagine that during travel in space you could just dump that waste out
into space considering the vastness of it all.

~~~
Symmetry
Whenever you're splitting Uranium atoms the results will tend to be
radioactive. The results will build up in the fuel over time and eventually
make the reactor stop working. Conventional reactors breed a bit of plutonium
too as U238 captures neutrons but most aerospace reactors want to be as light
as possible and so use highly enriched Uranium. So after your trip the engine
will be quite radioactive but, as you point out, there's a lot of space and
outside Earth's atmosphere and Van Allen belts it's moderately radioactive
anyways.

Thankfully nuclear reactors aren't particularly radioactive until you turn
them on, which is a big improvement on the radiothermal generators, RTGs, that
we sometimes use in probes headed for the outer solar system where solar
panels don't work. It's during launch, before this part gets turned on, that
you have a risk of crashing and losing the reactor somewhere on Earth.

~~~
ianai
I’m increasingly of the opinion that nuclear for space should be mined and
built in space. Just launch the infrastructure needed to bootstrap the
process.

~~~
Bud
Um, uh, um, uh...where to start?

"Mined" from where? How?

~~~
ianai
The moon? Asteroids? Or even just ship up unrefined ore such that a
catastrophic failure can’t threaten the population.

~~~
mitchty
Neither of the first two are options... at all realistically, nither uranium
nor thorium exist in anything below a large planetary size body in any
quantity: [https://www.quora.com/Do-uranium-and-thorium-exist-in-
signif...](https://www.quora.com/Do-uranium-and-thorium-exist-in-significant-
quantities-in-our-solar-systems-asteroid-belt)

And shipping up unrefined ore is also a bit of a ludicrous idea for mass
reasons and the rocket equation alone. You do realize you can isolate a
nuclear reactor core from explosions on rockets right? What catastrophic
failures are you attempting to design your solution of avoiding a nuclear
reactor around?

------
t0mbstone
How does one convert nuclear heat energy into directional energy for
propulsion purposes?

~~~
rmckayfleming
Take a look at this:
[https://en.wikipedia.org/wiki/Nuclear_lightbulb](https://en.wikipedia.org/wiki/Nuclear_lightbulb)

------
new_guy
Links dead.

Edit: available through outline
[https://outline.com/nbpE5n](https://outline.com/nbpE5n)

------
anon234345566
so things got really serious and we need to get out there as fast as we can

------
stickfigure
Anyone else just get a JSON 404 page from this link?

    
    
        {
            statusCode: 404,
            error: "Not Found",
            message: "Not Found"
        }

~~~
u801e
I tried it just now and was able to see the article. On another note, why do
they include the HTTP status code in the JSON body? Isn't it already present
in the status line of the HTTP response?

~~~
greglindahl
People using funky software stacks don't always have access to the status line
information, so some APIs include the status in json.

------
wfbarks
For the first time, period. Doesn’t look like we had one 60 years ago...

~~~
ceejayoz
We did:
[https://en.wikipedia.org/wiki/NERVA](https://en.wikipedia.org/wiki/NERVA)

Tested successfully (on the ground) in the 60s.

Real pity about its cancellation, too. It was considered for the "Grand Tour"
that the Voyager probes wound up doing; they could've sent nearly 30x the
spacecraft mass with NERVA rockets.

------
bra-ket
this is great! check out project Orion
[https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...](https://en.wikipedia.org/wiki/Project_Orion_\(nuclear_propulsion\))

~~~
inamberclad
It's much more likely to look like NERVA than Orion.

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

These types of engines have already been run:
[https://www.youtube.com/watch?v=eDNX65d-FBY](https://www.youtube.com/watch?v=eDNX65d-FBY)

------
BAReF00t
I’m disappointed.

I expected a project-Orion-type interstellar solution. Not a measly ”twice as
fast as conventional“ water kettle.

Also, no word about what they will acually use. Because classic uranium is a
quite limited resource actually. It has been said to run out even before
fossil fuels.

Also, why not a _fusion_ rocket? Given that we know how to make fusion bombs.
Because until we find a massive amount of anti-matter, this will be the next
best thing for a loong time. The only limiting factor would be a human body's
ability to withstand G forces.

~~~
cr0sh
> Because until we find a massive amount of anti-matter

I honestly hope this never occurs, or we never are able to contain/store such
a mass for any real length of time.

Because if we can do it, it will be used for a weapon.

Seriously - I can't even imagine what - for instance - one kilogram of anti-
matter coming in contact with regular matter - the amount of energy that would
be released...it staggers the imagination. Today's fusion weapons release only
a fraction of their potential energy; anti-matter conversion would be 100%
(roughly):

[https://en.wikipedia.org/wiki/Antimatter_weapon](https://en.wikipedia.org/wiki/Antimatter_weapon)

"Using the convention that 1 kiloton TNT equivalent = 4.184×1012 joules (or
one trillion calories of energy), one gram of antimatter reacting with one
gram of ordinary matter results in 42.96 kilotons-equivalent of energy (though
there is considerable "loss" by production of neutrinos)."

So...one kilo of anti-matter would be equivalent to 42 megatons - which is
close to yield of the Tsar Bomba:

[https://en.wikipedia.org/wiki/Tsar_Bomba](https://en.wikipedia.org/wiki/Tsar_Bomba)

...but in a much more compact package. 50 kg of antimatter - which would be
feasible for current launch systems, and comparable in size to current
warheads:

[https://en.wikipedia.org/wiki/W80_(nuclear_warhead)](https://en.wikipedia.org/wiki/W80_\(nuclear_warhead\))

Well - that's a 2 GT weapon...while I'm sure such a thing has been considered
as to it's effects...I honestly don't know what that would be. Best guess
might be that one such warhead could easily take out a good portion of say,
the west coast (of the United States)?

Ultimately - we are not ready in any manner - socially, morally, politically -
as a species to wield that kind of power responsibly. Honestly, even nuclear
weapons fall into that assessment, despite recent history - I'm honestly not
sure how we have gotten this far without a major nuclear war occurring.

Sadly, though, I know that my conjecture (in which I am not alone, I hope)
will not do anything to stop the research - right now, though, the cost to
produce anti-matter (let alone contain it) is so high as to make even a small
mass cost an exorbitant amount of money. I sincerely hope there isn't any
breakthrough on that front.

I honestly think we, as a species, are not ready for it (that isn't to say
none of us are - but those who would be responsible with such "stuff" are
likely very few - I know I am not one of them).

~~~
BAReF00t
Well, if we found it, it would already be contained unless accessed by
definition.

Also, magnetic fields could definitely contain it, as is already done.

We can already make anti-matter, as it't essentially the process of making
matter bounce off, using a photon, in such a way that it reverts its time
direction. Or, in classical view: Turn a photon into a particle/antiparticle
pair. The problem is, of course, that it first takes those shitloads of
energy, that it would release later.

And to actually _find_ anti-matter in nature, you would most likely have to
turn into anti-matter yourself, travel back in time, and somehow survive the
big bang without touching anything, to come out the hypothetized other side
where time is reversed and anti-matter expanded to. Or try to get inside a
black hole, and revert your direction of motion (as time and space are
reversed in there). Both not yet technically available, to say the least. ;)

