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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

#111

Post by api »

tiffanyg wrote: post #90

Aw man, forget all that noise. Bring back "Project Orion"*, baby! If we're not gettin' out our (NASA-approved) Huarache sandals, "waxing down" our pusher plate, and surfing "the pocket" of those sweet nuclear detonations in the near future, then, I'm afraid our species is utterly consigned to the category of "posers"!! See, Kilgore knew how to put this kind of (heavier) ordnance to good use: https://youtu.be/8XJYnKhI…

I loved hearing this called “the Devil’s pogo stick” once.

There were some paper studies showing that a thermonuclear version could theoretically work and reach speeds up to 10% the speed of light, which would be the Centauri system in a bit over 45 years. Of course you would have to slow down too which probably adds another few years.

If this can be theoretically done with technology contemporary with the Summer of Love, it really does make the Fermi paradox seem like something real.

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

#112

Post by joelwilliamson »

gibolt wrote: post #19
dzhiurgis wrote: post #17

Earlier quoted context omitted.

Falcon9 hadn’t had a failure for nearly a decade

Falcon 9 has had more than 200 consecutive successful flights in a row. That is more than double the next most successful, Delta II with 100 in a row. It also has well over 100 successful landings in a row, while the next closest rocket has 0. (Rocket, not capsule or shuttle, which are all still far lower)

There is another rocket that has had a few successful landings: Falcon Heavy.

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

#113

Post by JumpCrisscross »

flangola7 wrote: post #109
philipkglass wrote: post #26

Earlier quoted context omitted.

There won't be any fission products in the fuel if the chemical launcher fails to take the nuclear payload to orbit. The reactor activates for the first time after the initial orbital launch. The virgin fission fuel is less radiotoxic than RTG fuel.

>The reactor activates for the first time after the initial orbital launch. So they're going to launch an untested reactor into orbit without even turning it on first? Getting a reactor up and running is hard enough on the ground. I would expect any reactor to have had thousands of hours of testing and tweaking before being placed on the launch pad; that is the process for military boats and we have 60 years of exper…

> that is the process for military boats and we have 60 years of experience in that environment

Totally different reactor designs.

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

#114

Post by entriesfull »

Can they take a step forward and fix their drug crises, homelessness, and corruption first?

Oh wait, helping the poor doesn't make those holding stocks in these companies any money.

Maybe they can propulse their rockets with their politicians hot air.

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

#115

Post by TheSpiceIsLife »

Retric wrote: post #91
avar wrote: post #47

Earlier quoted context omitted.

> 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.

How often do failed rockets, or any space debris, fall on cities?

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

#116

Post by asu_thomas »

speff wrote: post #94
asu_thomas wrote: post #49

Earlier quoted context omitted.

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.

[flagged]

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

#117

Post by fallingknife »

credit_guy wrote: post #108

For anyone who wants a refresher on the UNS nuclear thermal rocket propulsion program from the '60s, here's the final report. It's a very good read: https://ntrs.nasa.gov/api/citations/19920005899/downloads/19... For this new initiative, I can see 2 big differences. On one hand they will use medium enriched uranium (up to 20%), while the original program used highly enriched one (85%), so it's going to be more challe…

Why are they nerfing the uranium like that?

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

#118

Post by maxbond »

asu_thomas wrote: post #116
speff wrote: post #94

Earlier quoted context omitted.

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.

[flagged]

Please refrain from being nasty to people going out of their way to answer your question. Any longtime English speaker is qualified to make observations about what is happening in their linguistic community. They went the extra mile to quantify it for you (in a community other than HN, in direct response to your question). You are free to choose how much weight you assign to their observation, and it's fine if it differs from your experience, but it's uncalled for to ask "what they're smoking."

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

#119

Post by marcosdumay »

WalterBright wrote: post #99
ridgeguy wrote: post #64

Earlier quoted context omitted.

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.

Well, much less than with a traditional rocket.
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