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The US government is taking a step toward space-based nuclear propulsion

arstechnica.com

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Re: The US government is taking a step toward space-based nuclear propulsion

#51

Post by Loquebantur »

db48x wrote: post #39
aio2 wrote: post #18

Earlier quoted context omitted.

I remember learning that when they started testing atomic bombs (I think?) the nuclear debris in the air spread basically throughout the whole united states and the government tried to keep quiet about it. Something similar will probably happen here if they mess up with the launch. Btw, the video I saw was on Veritasium.

The thing to remember about that is that we can measure tiny amounts of radiation very cheaply, and tiny amounts are harmless. In fact we are bathed in a constant, but tiny, background level of radiation all the time. Thousands of nuclear weapons were tested all across the world, in the United States, in the Soviet Union, on Pacific Islands, etc, etc. The radiation from that certainly caused a small uptick in the bac…

Background radiation is categorically different than ingesting/inhaling radioactive substances with the latter many orders of magnitude more dangerous.

The claim, nuclear testing related increases in radiation exposure not being relevant for public health is probably false. There are only very few studies with dubious reliability. The lifetime increase due to that nuclear testing is estimated to be 4.4 Millisieverts. It would have risen continuously with more surface tests, which got abolished accordingly.

The idea, beaches were a sanctum against radiation is wrong again. Sand is ground down mountains in case you wondered. Some are highly radioactive. But of course, UV light is harmful radiation as well.

Re: The US government is taking a step toward space-based nuclear propulsion

#52

Post by whycome »

> Wernher von Braun, the German engineer who defected to the United States after World War II, recognized the potential of nuclear thermal propulsion even before his Saturn V rocket landed humans on the Moon with chemical propulsion

> German engineer

Why does von Braun get such a pass from his Nazi past? Because he was useful?

Re: The US government is taking a step toward space-based nuclear propulsion

#53

Post by version_five »

asu_thomas wrote: post #35
mdorazio wrote: post #2

Finally! This is one of the few fission uses I'm genuinely excited about. Nuclear-thermal just makes so much sense for in-space propulsion of large vessels compared to chemical rockets.

[flagged]

It's funny because it's this, turning inward and waging war on ourselves after there wasn't an obvious enemy anymore that's responsible for the decline the upstream comment was talking about. Post WWII through the 90s saw massive increases in global standard of living, 2020's the west has gone back to religious squabbles over absurd ideological things. Watchmen had a similar idea.

Re: The US government is taking a step toward space-based nuclear propulsion

#54

Post by themodelplumber »

whycome wrote: post #52

> Wernher von Braun, the German engineer who defected to the United States after World War II, recognized the potential of nuclear thermal propulsion even before his Saturn V rocket landed humans on the Moon with chemical propulsion > German engineer Why does von Braun get such a pass from his Nazi past? Because he was useful?

Yeah, I think a lot of people would say that one's actions post-war are worth some weight in the equation, and culturally this person was positioned so as to not only make a big positive contribution in that quite separate context as far as values go, but a contribution which was also part of "our side" of a pitched cultural battle which is still raging. So like, how Nazi could you still be, in that actions-speaking sense.

Plus, people-controversy is a topic that's actively avoided in writing for a lot of audiences, especially if it invites fault-spreading, like if it's going to end up as a big whataboutism-fest.

Difficult topic in its way. Including of course the WW2-and-prior way involving terrible aspects like forced labor working under him, etc. So, less of a defense of a person here and more of a guess about rationale in authorship.

Re: The US government is taking a step toward space-based nuclear propulsion

#55

Post by version_five » 

  The basic idea is straightforward: A nuclear reactor rapidly heats up a propellant, probably liquid hydrogen, and then this gas expands and is passed out a nozzle, creating thrust. But engineering all of this for in-space propulsion is challenging, and then there is the regulatory difficulty of building a nuclear reactor and safely launching it into space.
Can anyone give a eli5 explanation of what makes this better than a conventional rocket? There still needs to b some mass ejected obviously. Is it that nuclear heat is able to make it go faster and provide more reactive force than burning it? What does the analysis look like?

Re: The US government is taking a step toward space-based nuclear propulsion

#56

Post by Arkhaine_kupo »

whycome wrote: post #52

> Wernher von Braun, the German engineer who defected to the United States after World War II, recognized the potential of nuclear thermal propulsion even before his Saturn V rocket landed humans on the Moon with chemical propulsion > German engineer Why does von Braun get such a pass from his Nazi past? Because he was useful?

"If Hannibal Lecter ran a 4.3, the NFL would call it an eating disorder".

People who are extremely succesful in certain fields get an impressive amount of leeway to break every conventional rule, law or protocol.

Allowing nazis to clean up their past and work for NASA is not the only horrible things the US did during the war or immidietly after either...

Re: The US government is taking a step toward space-based nuclear propulsion

#57

Post by arrosenberg »

asu_thomas wrote: post #37
ben_w wrote: post #16

Earlier quoted context omitted.

Depending on the design, failure during launch can be anywhere from "meh" to "basically high-altitude Chernobyl" — random actinide decay products (and plutonium fuel) are bad, unreacted uranium fuel is mostly a heavy metal hazard rather than a radiation hazard. (Could be worse, but the Orion drive is currently illegal by treaty and hopefully nobody is dumb enough to use that in Earth's ionosphere anyway).

What does "meh" mean? Is that english?

Its Yiddish, but came into popular use because of an episode of the Simpsons.

Re: The US government is taking a step toward space-based nuclear propulsion

#59

Post by rich_sasha »

version_five wrote: post #55

The basic idea is straightforward: A nuclear reactor rapidly heats up a propellant, probably liquid hydrogen, and then this gas expands and is passed out a nozzle, creating thrust. But engineering all of this for in-space propulsion is challenging, and then there is the regulatory difficulty of building a nuclear reactor and safely launching it into space. Can anyone give a eli5 explanation of what makes this better…

The propellant is important for its bulk (some mass to shoot out the back) and it's energy.

In a chemical rocket, the propellant provides both the bulk and the energy. As it happens, there isn't that much energy in chemical propellants per kg, but the rest of the engine is light enough that these things can fly to orbit.

In a nuclear rocket, the energy comes from a nuclear reaction and the gaseous fuel only provides the bulk. This is way more efficient. But such rockets likely cannot achieve orbit on their own because the whole set up is too heavy.

Re: The US government is taking a step toward space-based nuclear propulsion

#60

Post by hutzlibu »

version_five wrote: post #55

The basic idea is straightforward: A nuclear reactor rapidly heats up a propellant, probably liquid hydrogen, and then this gas expands and is passed out a nozzle, creating thrust. But engineering all of this for in-space propulsion is challenging, and then there is the regulatory difficulty of building a nuclear reactor and safely launching it into space. Can anyone give a eli5 explanation of what makes this better…

"Is it that nuclear heat is able to make it go faster and provide more reactive force than burning it?"

Yes, that is mostly it. Just compare the explosion from some hydrogen with a nuclear bomb. It is all about energy for mass in space, because all the fuel you have, you have to bring up into space, which needs more fuel, so need more fuel to bring that fuel up ... nuclear could help with that mass ratio a lot. And I like the concept in theory - as long as none of them explodes halfway up to space.

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