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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

#91

Post by Retric »

avar wrote: post #47
somenameforme wrote: post #7

Earlier quoted context omitted.

I think the obvious concern would be failure scenarios. There will always be failures in space technology. As space expands exponentially (as it is likely to do so in the future), failures will become relatively regular. So the obvious question would be what would happen if a nuclear rocket, with reaction in process, crashed to Earth. Or even if it broke up in the atmosphere.

> Or even if it broke up > in the atmosphere. The atmosphere we've already detonated over 500 nuclear weapons in?

Nuclear testing got to carefully select locations to minimize harm, uncontrolled reentry of nuclear rockets has significantly less control.

It’s not the 99 rockets falling into the ocean shortly after launch that are problematic, it’s the 1 that almost works but then lands in the city we should be concerned with.

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

#92

Post by FirmwareBurner »

ben_w wrote: post #89
asu_thomas wrote: post #35

Earlier quoted context omitted.

[flagged]

The people making these aren't any good at building houses. The lack of housing is, IMO, a failure of government — material costs for homes are surprisingly low compared to everything else — but even then, housing policy is a different department to the space stuff.

>The lack of housing is, IMO, a failure of government

Lack of housing is a "feature", not a bug, as it enriches the housing owning class and makes it more difficult for "undesirable" people to move in with NIMBYs.

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

#93

Post by philistine »

PartiallyTyped wrote: post #30
23B1 wrote: post #25

Earlier quoted context omitted.

Not sure about camera film, but there's certainly a need for 'low-background steel' for several applications: https://en.wikipedia.org/wiki/Low-background_steel

Speaking of, one way we verify old wine is through background radiation!

Sounds like the way Columbo would have caught one of the killers on the show.

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

#94

Post by speff »

asu_thomas wrote: post #49
sircastor wrote: post #41

Earlier quoted context omitted.

"Meh" is a casual response that means "this does not matter much". I don't know that it's proper English by any means, but it is certainly a common colloquialism. A cursory search suggests that it's imported from yiddish. [1] https://en.wikipedia.org/wiki/Meh

I have never seen it used outside of Hacker News.

It's not an uncommon expression. I searched the term in a chat room my friends (of varying professional backgrounds) have used over the past 5 years. There were about 200 instances of us using the word.

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

#96

Post by gibolt »

ben_w wrote: post #87
gibolt wrote: post #20

Earlier quoted context omitted.

The nuclear payload could be treated similar to humans, with eject systems and soft landing built in. The fuel will only be needed for a lighter craft in deep space. Getting it up with a high reliability rocket (like Falcon 9) significantly decreases risk.

> The nuclear payload could be treated similar to humans, with eject systems and soft landing built in. In principle yes — even just on the grounds that enriched fuel is expensive — but it's a hard thing to prove in advance, hence all the times humans died in a space mission one way or another.

There have only been 5 instances resulting in 19 fatalities. None were when exiting the atmosphere. 2 were the flawed Space Shuttle on return. Only one other was a flight system, on an experimental craft.

https://en.m.wikipedia.org/wiki/List_of_spaceflight-related_....

Today's rockets are far more reliable, and anything holding nuclear fuel should be the best of the best.

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

#97

Post by WalterBright »

pixl97 wrote: post #82
version_five wrote: post #53

Earlier quoted context omitted.

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.

Post WWII understood how terrible war was. Post 90s those that experienced it in mass were going extinct. We forgot what fascism did to the past and too many are embracing it again.

Or the definition of fascism has expanded to cover all one's political enemies.

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

#98

Post by numpad0 »

rbanffy wrote: post #70
echelon wrote: post #27

Earlier quoted context omitted.

Peace time = smart phone incrementalism, social media, ad tech, Bitcoin, NFTs, WeWork, low interest rate malinvestment, Twitter/Tumblr pessimism Cold war = rocket science, new fuels, materials science, major computing advancements, supply chain changes, innovation, science hype, broad optimism I know most of this is happenstance and that peace time doesn't itself cause lackluster development, but it is interesting an…

> Cold war = rocket science, new fuels, materials science, major computing advancements, supply chain changes, innovation, science hype, broad optimism Next time the cold war cools down, we need to invent something to replace it.

Hot war in outer spaces is should do. War is fine so long 1.(selfishly) it won't kill me, 2. it has no chance of ending the humanity, and 3. the sites devastated can recover.

Colonial wars in the asteroid belt and beyond. Interstellar wars. Maybe the first FTL drive could be on an autonomous space torpedo, and that could be lore explanation for the shape of warp nacelles in this timeline.

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

#99

Post by WalterBright »

ridgeguy wrote: post #64
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…

It's the high temperature and the lower exhaust molecular weight. Specific impulse (Isp) is how much force you get from each mass unit of propellant you exhaust. So an engine with Isp = 300 gives 300lbs force for every pound of exhaust gas mass. IIRC, Isp scales as the inverse square root of exhaust molecular weight. So a pure (molecular) hydrogen exhaust would have a molecular weight of 2. A pure H2/O2 engine would…

You'd also not have to worry about the propellant exploding.

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

#100

Post by WalterBright »

gibolt wrote: post #96
ben_w wrote: post #87

Earlier quoted context omitted.

> The nuclear payload could be treated similar to humans, with eject systems and soft landing built in. In principle yes — even just on the grounds that enriched fuel is expensive — but it's a hard thing to prove in advance, hence all the times humans died in a space mission one way or another.

There have only been 5 instances resulting in 19 fatalities. None were when exiting the atmosphere. 2 were the flawed Space Shuttle on return. Only one other was a flight system, on an experimental craft. https://en.m.wikipedia.org/wiki/List_of_spaceflight-related_... . Today's rockets are far more reliable, and anything holding nuclear fuel should be the best of the best.

> None were when exiting the atmosphere

Er, Challenger?

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