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The Project Orion design (shoot hundreds of fission bombs out the back and ride the shock wave on a reaction plate) is surprisingly practical, and probably our

The Project Orion design (shoot hundreds of fission bombs out the back and ride the shock wave on a reaction plate) is surprisingly practical, and probably our only way to get humans past Mars. It's just kind of terrifying.

lostlogin 3y ago
Yup, it’s scary. “A moderate-sized nuclear device was estimated, at the time, to produce about 5 or 10 billion horsepower.” https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propu...
- idlewords 3y ago
  George Dyson (Freeman's brother) wrote a book on it that is fantastic reading.
  - whycome 3y ago
    > Freeman's brother Son. https://en.wikipedia.org/wiki/George_Dyson_(science_historian) https://en.wikipedia.org/wiki/George_Dyson_(science_historia... Relatives Sir George Dyson (grandfather) Freeman Dyson (father) Verena Huber-Dyson (mother)[1] Esther Dyson (sister)
    - idlewords 3y ago
      My bad; I should have checked. Thank you for the correction!
- moffkalast 3y ago
  Finally, the gigahorse.
throwaway4aday 3y ago
The energy required to accelerate a useful amount of mass to a high enough velocity to travel interplanetary (or interstellar) distances in a timely manner is always going to be terrifying. Even if it runs on rainbows and hugs the kinetic energy imparted to the payload would turn it into a planet killer if you ever rammed it into one. Managing that risk so you get the payoff without any accidents along the way is the only sensible thing to do.
- woopsn 3y ago
  Not building the ship of thousands of little nukelets IS managing risk.
xwdv 3y ago
Not really any more terrifying than driving around in vehicles powered by thousands of tiny explosions per minute.
- idlewords 3y ago
  If someone siphons your gas tank, they're not going to be able to nuke Paris. But a nuclear pulse rocket needs thousands of bomblets the size of coke cans. That's the scary part.
  - marcinzm 3y ago
    > size of coke cans. Not really, each one would be 6 inches in diameter and weight over 300lbs.
    - p1mrx 3y ago
      Sounds impossible. A 6 inch diameter uranium sphere is only 80 lbs, and there are no materials significantly denser than that.
      - postalrat 3y ago
        They sell coke cans in the shape of a sphere?
        p1mrx 3y ago
        https://www.google.com/search?q=spherical+coke+bottle&tbm=isch https://www.google.com/search?q=spherical+coke+bottle&tbm=is...
    - idlewords 3y ago
      Dyson's book hints that they ended up far smaller, but the details of that are classified to the gills.
api 3y ago
Ahh the old "devil's pogo stick."
tomatotomato37 3y ago
Should also note that the Orion design most people are familiar with is from the 60s, when the latest in engineering used vacuum tubes. Modern innovations in material science, computer assisted design, and just technology that just simply didn't exist yet such as laser ignition would permit ditching the ridiculous pogo stick pusher plate arrangement with something that's more efficient, runs smoother, and looks a lot more traditional too. I wouldn't be surprised if a modern variant looks like that one Sea Dragon concept with beefier nozzle suspension
SECProto 3y ago
> The Project Orion design [...] is surprisingly practical, and probably our only way to get humans past Mars. I don't think this is the general consensus. It is seen as one of the only ways to get humans out of the solar system, but other nuclear rockets[1], and even chemical options[2], could get humans to eg the Jovian moons[3] with TRL's much higher than Project Orion. [1] https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA [2] https://en.wikipedia.org/wiki/Interplanetary_spaceflight#Cyclers https://en.wikipedia.org/wiki/Interplanetary_spaceflight#Cyc... [3] https://en.wikipedia.org/wiki/Exploration_of_Jupiter#Human_exploration https://en.wikipedia.org/wiki/Exploration_of_Jupiter#Human_e...
- idlewords 3y ago
  It's not just about propulsion, but radiation. The radiation environment in space is awful and you need thousands of tons of shielding to effectively screen a crew from cosmic rays. Moreover, because of secondary radiation, partial shielding from energetic cosmic rays is worse than none. A unique property of nuclear pulse propulsion is that the engineering gets easier the more massive the spacecraft. That leaves lots of room for radiation shielding and consumables, and makes it the only halfway practical choice for multi-year missions into the outer solar system.
  - SECProto 3y ago
    > That leaves lots of room for radiation shielding and consumables, and makes it the only halfway practical choice for multi-year missions into the outer solar system. I disagree, one of the types I referenced is cyclers, which are specifically good for the same kind of reason. NERVA is another alternative that becomes similarly easier as you scale it up. All three types would need in-space assembly, so no big issues with any of them that way. Don't get me wrong, Orion is cool (and the only way to conceivably run an interstellar mission with known technology/physics), but it isn't necessary (or even desirable imo) for interplanetary missions, at least as far as saturn anyway.
    - idlewords 3y ago

lostlogin 3y ago

Yup, it’s scary. “A moderate-sized nuclear device was estimated, at the time, to produce about 5 or 10 billion horsepower.” https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propu...

idlewords 3y ago
George Dyson (Freeman's brother) wrote a book on it that is fantastic reading.
- whycome 3y ago
  > Freeman's brother Son. https://en.wikipedia.org/wiki/George_Dyson_(science_historian) https://en.wikipedia.org/wiki/George_Dyson_(science_historia... Relatives Sir George Dyson (grandfather) Freeman Dyson (father) Verena Huber-Dyson (mother)[1] Esther Dyson (sister)
  - idlewords 3y ago
    My bad; I should have checked. Thank you for the correction!
moffkalast 3y ago
Finally, the gigahorse.

throwaway4aday 3y ago

The energy required to accelerate a useful amount of mass to a high enough velocity to travel interplanetary (or interstellar) distances in a timely manner is always going to be terrifying. Even if it runs on rainbows and hugs the kinetic energy imparted to the payload would turn it into a planet killer if you ever rammed it into one. Managing that risk so you get the payoff without any accidents along the way is the only sensible thing to do.

woopsn 3y ago
Not building the ship of thousands of little nukelets IS managing risk.

xwdv 3y ago

Not really any more terrifying than driving around in vehicles powered by thousands of tiny explosions per minute.

idlewords 3y ago
If someone siphons your gas tank, they're not going to be able to nuke Paris. But a nuclear pulse rocket needs thousands of bomblets the size of coke cans. That's the scary part.
- marcinzm 3y ago
  > size of coke cans. Not really, each one would be 6 inches in diameter and weight over 300lbs.
  - p1mrx 3y ago
    Sounds impossible. A 6 inch diameter uranium sphere is only 80 lbs, and there are no materials significantly denser than that.
    - postalrat 3y ago
      They sell coke cans in the shape of a sphere?
      - p1mrx 3y ago
        https://www.google.com/search?q=spherical+coke+bottle&tbm=isch https://www.google.com/search?q=spherical+coke+bottle&tbm=is...
  - idlewords 3y ago
    Dyson's book hints that they ended up far smaller, but the details of that are classified to the gills.

api 3y ago

Ahh the old "devil's pogo stick."

tomatotomato37 3y ago

Should also note that the Orion design most people are familiar with is from the 60s, when the latest in engineering used vacuum tubes. Modern innovations in material science, computer assisted design, and just technology that just simply didn't exist yet such as laser ignition would permit ditching the ridiculous pogo stick pusher plate arrangement with something that's more efficient, runs smoother, and looks a lot more traditional too. I wouldn't be surprised if a modern variant looks like that one Sea Dragon concept with beefier nozzle suspension

SECProto 3y ago

> The Project Orion design [...] is surprisingly practical, and probably our only way to get humans past Mars. I don't think this is the general consensus. It is seen as one of the only ways to get humans out of the solar system, but other nuclear rockets[1], and even chemical options[2], could get humans to eg the Jovian moons[3] with TRL's much higher than Project Orion. [1] https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA [2] https://en.wikipedia.org/wiki/Interplanetary_spaceflight#Cyclers https://en.wikipedia.org/wiki/Interplanetary_spaceflight#Cyc... [3] https://en.wikipedia.org/wiki/Exploration_of_Jupiter#Human_exploration https://en.wikipedia.org/wiki/Exploration_of_Jupiter#Human_e...

idlewords 3y ago
It's not just about propulsion, but radiation. The radiation environment in space is awful and you need thousands of tons of shielding to effectively screen a crew from cosmic rays. Moreover, because of secondary radiation, partial shielding from energetic cosmic rays is worse than none. A unique property of nuclear pulse propulsion is that the engineering gets easier the more massive the spacecraft. That leaves lots of room for radiation shielding and consumables, and makes it the only halfway practical choice for multi-year missions into the outer solar system.
- SECProto 3y ago
  > That leaves lots of room for radiation shielding and consumables, and makes it the only halfway practical choice for multi-year missions into the outer solar system. I disagree, one of the types I referenced is cyclers, which are specifically good for the same kind of reason. NERVA is another alternative that becomes similarly easier as you scale it up. All three types would need in-space assembly, so no big issues with any of them that way. Don't get me wrong, Orion is cool (and the only way to conceivably run an interstellar mission with known technology/physics), but it isn't necessary (or even desirable imo) for interplanetary missions, at least as far as saturn anyway.
  - idlewords 3y ago