Interstellar nuclear-powered transport (1968) [pdf] | Hacker News Reader

Interstellar nuclear-powered transport (1968) [pdf]

people.eecs.berkeley.edu

57 pointsantondd34 comments

One interesting tidbit toward the end is that the author thinks building this ship is feasible within 200 years of the writing, with a cost estimate of $10^11 in 1968 dollars, assuming a 4% GNP growth rate. I haven't calculated what $10^11 would become in 2021 dollars, but growth hasn't been that high since the 90s, and it wasn't sustained growth, even then.

He gives a comparison estimate that each Saturn V cost about 10^8 each. Per quick Google search actual cost in 1970s dollars was $185m which is $1.15b today: https://en.wikipedia.org/wiki/Saturn_V#Cost (important, but unrelated to rest of computation fact is that this cost was amortized over 35 flights)

10^11 is 1000 * 10^8, applying same inflation to 10^11 we get $1.15t. To put this number in a context, Iraq war is estimated to have long term cost of $1.1tn to $1.92tn: https://en.wikipedia.org/wiki/Financial_cost_of_the_Iraq_War

If SpaceX Starship can get going as planned (eq. fully & rapidly reusable orbital transport) it should be possible to slash the costs of launch for big proposals like this quite significantly.

The proposal is a 5 million ton, 10 km shell of copper fueled by 30 million hydrogen bombs. Cost to orbit isn't particularly relevant (it would easily be optimized as part of the decades long project).

I’ve heard of nuclear bomb propulsion before but I had no idea that 30 million hydrogen bombs we’re proposed. That’s insane!

And do you know what's more insane (and even more cool!) - Nuclear Salt Water Rocket!

https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

Riding a continuous nuclear explosion for fun and profit! :D

exactly, all these old estimates need to be revised in SpaceX era. We are living in unprecedented times when a private company does something that was previously only possible with global superpower resources.

The way the GDP and the GDP growth are calculated is a bit funny. In that if you start with one year and compound the official GDP growth for a number of years, you end up with a number that is much lower than the actual GDP at the end of that period.

In this particular case, Dyson mentions a GNP of about $600 BN. Since I don't know exactly the difference between the GDP and the GNP, I'll use the official GDP as recorded by the Fed [1]. It was $968 BN in 1968 and $21.5 TN in 2020. That's a (compounded) growth rate of more than 6% per year.

[1] https://fred.stlouisfed.org/series/GDP

The data series you are looking at is nominal, not real, GDP [0], so the annual growth multiplier (1 + growth rate) is the real GDP growth multiplier times the inflation multiplier.

In current dollars, 1968’s real GDP is something over $4 trillion.

[0] The St. Louis Fed has both series, see https://fred.stlouisfed.org/series/GDPC1

For a government project I would at least double the numbers.

Reminds me of a project I heard about yesterday. Decades ago, a bridge for a private railway company was built in such a way that it could also carry an interurban rail and be an automobile highway. After decades, only the railroad portion had ever been used.

I suspect that was the intended outcome, and I suspect that the project was, in part at least, taxpayer-funded. From history, I also suspect that many such projects serve as a way to get public dollars into -the right- private pockets. Sometimes they're sold as 'job creation' programs. Uh-huh.

There is a very interesting book about Freeman Dyson and his son George Dyson.

While Freeman was building starships to escape civilization into the stars, George was building massive spaceframe canoes to escape civilization into the wilderness.

Both are very interesting men in their own right, and George is still building canoes and kayaks out of his shop in Bellingham, WA

Here's a BBC documentary — "To Mars by A-Bomb" with interviews by both father and son, as well as Arthur C. Clarke:

https://youtu.be/xYoLcJuBtOw

The postmortem was a great read too: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.69...

More details and sketches of potential designs: https://newatlas.com/orion-project-atom-bomb-spaceship/49454...

One thing I'm sure I don't understand: from a material science perspective, how would you produce shock absorbers capable of repeated and sustained shockwaves at 100 second intervals from h-bombs? It seems like any material you select, as exotic as it may be, will degrade pretty quickly. Doesn't seem like 200 years will solve this problem.

Liquids aren't degraded by shockwaves, but the pusher plates were always intended to be ablative. If they start developing cracks I guess you can melt them down and recast them.

It was discovered at some point that a thin film of oil would protect the explosion-facing side of the plate. There was something about the skin oils of a fingerprint leading to that discovery, but I don’t remember details.

Probably from ablation, though, not from shock or radiation damage?

Maybe this is outside the scope, but one thing I’m really curious about —- what about the radiation!?

I’m guessing the payload could be sufficiently shielded and/or would just outrun it. But would there be any eventual issues with blasting out tons of radiation all over space wherever it went? In particular, this seems like a big problem during take-off from Earth…

Calculations at the time (late 1950s-early 1960s) were that the radiation released by Orion in the earth’s atmosphere would lead to a single additional death from cancer each year. And isn’t there already a great deal of radiation in space?

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

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.

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.

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.

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.

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.

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.

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

Launch loops:

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

Heck, there is a dedicated article for these in the Wikipedia!

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.

The book written by Freeman's son George Dyson is also very good:

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

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.

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#Medus... and 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 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-or...

Seems like there might be but wondering if theres any overlap here with the frozen brain solar sail nuclear bomb space detonation acceleration idea from Liu Cixins Dark Forest romance novel?

Wasn't that called outright an Orion drive ? Even if it wasn't it pretty much the very same concept.

Weirdly I asked hn about this yesterday not sure what happened to the thread but I’m super glad someone else picked up from there it’s been a great read thanks !

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