5 ms·

also see https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

hermitcrab 5y ago
I spoke to Freeman Dyson at a book signing he did after a talk about Project Orion (at the wonderfully named 'festival of inappropriate technology'). I asked him about the environmental impact. He said (from memory) that most big engineering projects (dams, bridges etc) kill people, but nuclear pulse probably shouldn't be used in the atmosphere. And wasn't worth using if you weren't going to use it in the atmosphere.
- deleted 5y ago
  [deleted]
- m4rtink 5y ago
  I remember reading that the atmosphere helps significantly with performance, but indeed, locals would likely complain in many cases. But on a gas giant like Jupiter it might not be an issue.
  - murderfs 5y ago
    The big problem is that they need to be fucking huge, because nuclear warheads only scale down so far. If you're not going to be using it in atmosphere, that raises the question of how you're going to get the thing into orbit in the first place.
    - andyxor 5y ago
      assemble it in space, on low earth orbit (LEO) with many trips of e.g. SpaceX Starship, kind of like the international space station was assembled piece by piece over time.
      - hermitcrab 5y ago
        Freeman Dyson made the point (from memory) that the main advantage was that it was powerful enough to lift a really big payload into orbit. If you were going to lift the parts into orbit using chemical rockets, then that was defeating a lot of the point of using the technology in the first place.
        murderfs 5y ago
        Right. Pretty much every other technology has to choose between high thrust and high specific impulse (i.e. efficiency). Chemical rockets have tons of thrust, but bad efficiency. Electric propulsion (ion drives, etc.) is really efficient, but most implementations have thrusts that are on the order of being able to lift a sheet of paper.
        m4rtink 5y ago
        Well, there are quite a few ways of moving lots of stuff out of the gravity well without turning the Planet below into the Fallout franchise. The already mentioned reusable chemical rockets will loft quite a bit as long as they are really reusable and durable. Space elevators (there are still material challenges for Earht, but IIRC existing materials would be enough for Mars): https://en.wikipedia.org/wiki/Space_elevator https://en.wikipedia.org/wiki/Space_elevator Launch loops: https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop Space fountains and active structures in general (are crazy but have high useful potential): https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Space_fountain Heck, there is a dedicated article for these in the Wikipedia! https://en.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.wikipedia.org/wiki/Non-rocket_spacelaunch Still, I would say ideally you would want to move most of the heavy manufacturing to space & from space resources anyway. Then reusable chemical rockets might be good enough to move people and other compact high value cargo between Earth surface & space infrastructure.
sien 5y ago
The book written by Freeman's son George Dyson is also very good: https://www.amazon.com/Project-Orion-Story-Atomic-Spaceship/dp/0805072845/ref=sr_1_2?dchild=1&keywords=project+orion&qid=1628638417&sr=8-2 https://www.amazon.com/Project-Orion-Story-Atomic-Spaceship/... Alas there is no ebook and the print book is quite expensive. There is a documentary on Youtube from the BBC about it all: https://www.youtube.com/watch?v=uMcwVj0S6Ws https://www.youtube.com/watch?v=uMcwVj0S6Ws
- AlbertCory 5y ago
  I have the print book! Or at least I did once. This was a big project with lots of top-shelf nuclear physicists. It's quite interesting, and they spent a lot of time considering the ablation problem, i.e. how do you make a "pusher plate" to absorb the force of the nuclear blasts and not fall apart? They got as far as testing a small version of it with conventional explosives, but the nuclear test ban treaty under President Kennedy put a permanent end to the project.
  - techdragon 5y ago
    Usually it boils down to ablatives. Either your pusher is designed to ablate at a known rate and factored into the propulsion calculations as fuel mass, or you are protecting the pusher plate by doing something like injecting synthetic oil that wont spontaneously boil in the vacuum of space through pores in the pusher plate so that the oil becomes a protective layer that boils off instead of eroding the surface of the pusher plate. The other method I've seen is to "go big" and scale things up to the point where the pusher plate is collecting enough force, but spread over a sufficient area that while the pusher can effectively and "safely" capture the plasma debris from the pulses while keeping the flux of high energy photons low enough that it doesn't erode the pusher plate from the radiation flux. The "Medusa" design scales this up to the extreme, putting the explosion ahead of the spacecraft and using a giant spherical "sail" to capture the energy from each explosion, if you simplify Project Orion as "explosion under pogo stick while you stand on it", then the Medusa design is "explosion above your head while you wear a hard hat, holding onto an umbrella with a pole made from elastic bands". Detail https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medus... and http://www.projectrho.com/public_html/rocket/enginelist3.php#medusa http://www.projectrho.com/public_html/rocket/enginelist3.php... Since you mention the tests with conventional explosives, I love bringing up the actual tests that were done when people talk dismiss Orion as an impractical idea that wouldn't have worked, seeing the "Hot Rod" fly powered by RDX explosions is usually enough to convince someone the physics of the idea is completely sound. Theres a nice set of videos from the test program here https://www.youtube.com/watch?v=Q8Sv5y6iHUM https://www.youtube.com/watch?v=Q8Sv5y6iHUM which also includes the "Hot Rod" test, which is also the largest remaining object/artefact of the entire Project Orion program of work. The "Hot Rod" test vehicle is housed in a crate (not on display) at the Smithsonian, its part of the National Air and Space Museum Collection https://www.si.edu/object/propulsion-test-vehicle-project-orion:nasm_A19721008000 https://www.si.edu/object/propulsion-test-vehicle-project-or...

hermitcrab 5y ago

I spoke to Freeman Dyson at a book signing he did after a talk about Project Orion (at the wonderfully named 'festival of inappropriate technology'). I asked him about the environmental impact. He said (from memory) that most big engineering projects (dams, bridges etc) kill people, but nuclear pulse probably shouldn't be used in the atmosphere. And wasn't worth using if you weren't going to use it in the atmosphere.

deleted 5y ago
[deleted]
m4rtink 5y ago
I remember reading that the atmosphere helps significantly with performance, but indeed, locals would likely complain in many cases. But on a gas giant like Jupiter it might not be an issue.
- murderfs 5y ago
  The big problem is that they need to be fucking huge, because nuclear warheads only scale down so far. If you're not going to be using it in atmosphere, that raises the question of how you're going to get the thing into orbit in the first place.
  - andyxor 5y ago
    assemble it in space, on low earth orbit (LEO) with many trips of e.g. SpaceX Starship, kind of like the international space station was assembled piece by piece over time.
    - hermitcrab 5y ago
      Freeman Dyson made the point (from memory) that the main advantage was that it was powerful enough to lift a really big payload into orbit. If you were going to lift the parts into orbit using chemical rockets, then that was defeating a lot of the point of using the technology in the first place.
      - murderfs 5y ago
        Right. Pretty much every other technology has to choose between high thrust and high specific impulse (i.e. efficiency). Chemical rockets have tons of thrust, but bad efficiency. Electric propulsion (ion drives, etc.) is really efficient, but most implementations have thrusts that are on the order of being able to lift a sheet of paper.
        m4rtink 5y ago
        Well, there are quite a few ways of moving lots of stuff out of the gravity well without turning the Planet below into the Fallout franchise. The already mentioned reusable chemical rockets will loft quite a bit as long as they are really reusable and durable. Space elevators (there are still material challenges for Earht, but IIRC existing materials would be enough for Mars): https://en.wikipedia.org/wiki/Space_elevator https://en.wikipedia.org/wiki/Space_elevator Launch loops: https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop Space fountains and active structures in general (are crazy but have high useful potential): https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Space_fountain Heck, there is a dedicated article for these in the Wikipedia! https://en.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.wikipedia.org/wiki/Non-rocket_spacelaunch Still, I would say ideally you would want to move most of the heavy manufacturing to space & from space resources anyway. Then reusable chemical rockets might be good enough to move people and other compact high value cargo between Earth surface & space infrastructure.

sien 5y ago

The book written by Freeman's son George Dyson is also very good: https://www.amazon.com/Project-Orion-Story-Atomic-Spaceship/dp/0805072845/ref=sr_1_2?dchild=1&keywords=project+orion&qid=1628638417&sr=8-2 https://www.amazon.com/Project-Orion-Story-Atomic-Spaceship/... Alas there is no ebook and the print book is quite expensive. There is a documentary on Youtube from the BBC about it all: https://www.youtube.com/watch?v=uMcwVj0S6Ws https://www.youtube.com/watch?v=uMcwVj0S6Ws

AlbertCory 5y ago
I have the print book! Or at least I did once. This was a big project with lots of top-shelf nuclear physicists. It's quite interesting, and they spent a lot of time considering the ablation problem, i.e. how do you make a "pusher plate" to absorb the force of the nuclear blasts and not fall apart? They got as far as testing a small version of it with conventional explosives, but the nuclear test ban treaty under President Kennedy put a permanent end to the project.
- techdragon 5y ago
  Usually it boils down to ablatives. Either your pusher is designed to ablate at a known rate and factored into the propulsion calculations as fuel mass, or you are protecting the pusher plate by doing something like injecting synthetic oil that wont spontaneously boil in the vacuum of space through pores in the pusher plate so that the oil becomes a protective layer that boils off instead of eroding the surface of the pusher plate. The other method I've seen is to "go big" and scale things up to the point where the pusher plate is collecting enough force, but spread over a sufficient area that while the pusher can effectively and "safely" capture the plasma debris from the pulses while keeping the flux of high energy photons low enough that it doesn't erode the pusher plate from the radiation flux. The "Medusa" design scales this up to the extreme, putting the explosion ahead of the spacecraft and using a giant spherical "sail" to capture the energy from each explosion, if you simplify Project Orion as "explosion under pogo stick while you stand on it", then the Medusa design is "explosion above your head while you wear a hard hat, holding onto an umbrella with a pole made from elastic bands". Detail https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medus... and http://www.projectrho.com/public_html/rocket/enginelist3.php#medusa http://www.projectrho.com/public_html/rocket/enginelist3.php... Since you mention the tests with conventional explosives, I love bringing up the actual tests that were done when people talk dismiss Orion as an impractical idea that wouldn't have worked, seeing the "Hot Rod" fly powered by RDX explosions is usually enough to convince someone the physics of the idea is completely sound. Theres a nice set of videos from the test program here https://www.youtube.com/watch?v=Q8Sv5y6iHUM https://www.youtube.com/watch?v=Q8Sv5y6iHUM which also includes the "Hot Rod" test, which is also the largest remaining object/artefact of the entire Project Orion program of work. The "Hot Rod" test vehicle is housed in a crate (not on display) at the Smithsonian, its part of the National Air and Space Museum Collection https://www.si.edu/object/propulsion-test-vehicle-project-orion:nasm_A19721008000 https://www.si.edu/object/propulsion-test-vehicle-project-or...