A 1970s plan about how to reach Barnard’s Star

21.53, Tuesday 15 Feb 2022

Project Daedalus is a study from 1978 about how to send an interstellar probe 5.9 light years to Bernard’s Star.

The craft is massive: twice the height of a Saturn V and with a diameter almost the same. It was imagined to be constructed in Earth orbit and accelerated to 7% light speed, in two stages. The first stage a standard rocket burn, though for almost two years. The second, for another two years, a nuclear pulse rocket:

Pellets comprised of deuterium and helium-3 would be bombarded by high-powered electron beams, thus triggering fusion and detonating the mass like a tiny nuclear bomb. These explosions would be repeated at a rate of two hundred and fifty per second, using a powerful magnetic field as the rocket’s nozzle.

Tiny atom bombs, hundreds of times a second! The blast captured in the deflector dish, propulsion from a magnetically-shaped plasma jet.

And 46 years later…

Daedalus would sail right by Barnard’s Star (it wasn’t intended to carry fuel to decelerate).

Daedalus would carry 18 autonomous probes, equipped with artificial intelligence, to investigate the star and its environs. The 40m diameter engine of the second stage would double as a communications dish. On top of the second stage would be a payload bay containing the probes, two 5m optical telescopes, and two 20m radio telescopes. Robot wardens would be able to make in-flight repairs. A 50-ton disk of beryllium, 7 mm thick, would protect the payload bay from collisions with dust and meteoroids on the interstellar phase during the flight, while an artificially-generated cloud of particles some 200 km ahead of the vehicle would help disperse larger particles as the probe plunged into the planetary system of the target star.

(Check out the pictures at that link – mockups and diagrams.)

So it was all planned out, in enormous detail. I haven’t read the original papers but I’ve seen talks that cite them, and they mention even the repairability assumptions made by the mission designers – what the mean time between failure is of the number of parts required, and the mass required for the spare parts required en route. And so on.

Project Daedalus (named after Daedalus, the Greek mythological designer who crafted wings for human flight) was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible uncrewed interstellar probe.

Background from Wikipedia.

(I am a member of the British Interplanetary Society, as previously discussed.)

The group in the 1970s comprised a dozen scientists and engineers, meeting mostly in the pub: Daedalus was the first serious and thorough design for a starship.

AND SO (I understand) it is the baseline for researching interstellar travel, by Nasa etc, even today.

The project rules are key:

The spacecraft must use current or near-future technology.

The spacecraft must reach its destination within a human lifetime.

The spacecraft must be designed to allow for a variety of target stars.

(The second rule is why Daedalus’ journey takes 50 years.)

The first is the one that matters: no new physics.

By “no new physics” we mean: no faster than light travel suddenly discovered; no unanticipated breakthrough in human hibernation; no breakthrough in mechanical engineering reliability or energy storage density; no ansibles, no aliens, no RF resonant cavity thruster.

Daedalus is an interstellar probe and a also probe into science and the imagination.

Is it how such a project would be performed today? No. But it was important. Why?

By studying and specifying how to send the probe (and how to fuel it, and how to shield it, and how to repair it in flight, and how to perform the scientific research, and how to communicate back…) you get two things:

  • A plan that can be built on: parts of the plan can be swapped out and iterated and improved. An engineering study becomes a kind of Wikipedia, a collaboration in the scientific discourse over decades.
  • A lens to focus effort. Now there’s a plan, it’s possible to see what the biggest challenges are. Out of all the new engineering possible, what would have highest impact?

It problematises. It turns one big problem that can’t be tackled into lots of small ones that can.


There are lots of ways to invent new things, and here I’m thinking about new products and startups and all of that.

Like: design fictions are a method of exploring futures that create fully-rendered plausible worlds and so “adjacent possible” artefacts (products and services) drop out.

Like: MVP (Minimum Viable Product) which is the typical product-engineering approach by which a startup attempts to meet a need, as quickly and simply as possible, and discover whether there is demand for it in the market.

A “no new physics” study is a different kind of probe, an engineering fiction that simultaneously

  • follows a path of minimum effort: everything in the plan (which might be written, or might be wireframes/drawings) either exists already or there is clear line of sight to building it
  • yet has its own ambitious North Star: maybe it has to achieve a particular goal in terms of user growth, or allow for a particular interaction or feeling, or meet a particular business need.

It’s going to be cumbersome. Like Daedalus it’s going to be 2 x the height of a Saturn V and just the same across.

But it problematises! It focuses! It demonstrates the possibility of a bridge across the canyon and now you can figure out a good one.

If we had to do this today then how would we do it – a challenge that teaches you a lot. It strips away so much from whatever prototype you currently have, and forces you to think about what you actually need to build next.

Anyway. I’m spending a lot of time making drawings this week and staring into space, imagining how these plans/possibilities/probes might come to life. Not spaceships but work.

HEY, so many years ago I went to some talks and that was when I first learnt about Project Daedalus, and it was in the context of the drive: assuming no new physics, the best way we can imagine to get between stars is this system of exploding tiny atom bombs at the back of the ship, hundreds of times a second (250Hz is the Daedalus frequency).

A bigger starship (the series of talks was on the topic of generation ships, which take many human lifetimes for interstellar travel) will take longer to accelerate – a couple of decades instead of two years. Then when the ship is up to speed, the drive stops its acceleration (accelerating more would mean carrying more fuel, which would mean more mass which is harder to accelerate. There’s an ideal).

Midway through the talk, the speaker made a throwaway comment and I remember it today:

Pulsars are a certain type of star that we’ve seen, and they flash - pulse with light, hence the name - hundreds of times a second.

And some scientists say that, when you study pulsars, you notice that they appear to have high proper motion. That is, compared to other stars, they’re moving.

So… are pulsars actually interstellar ships? Are we seeing travel between the stars, the nuclear pulse rocket in action?

Who knows how plausible any of this is. How throwaway was that comment? How seriously should it have been taken? I don’t know.

But what an image – the sky above our heads, a map, the ships visible! Van Gogh: should the shining dots of the sky not be as accessible as the black dots on the map of France?

Well - said the speaker, and specifically this has stuck in my head all these years - here’s how we would know: we can calculate the optimum firing frequency for these nuclear pulse rockets, a few hundred hertz we know that, and we can calculate the optimum many-year burn time, that’s all Newton’s laws.

Which means that what we need to do is continue monitoring pulsars with our space telescopes and look out for one that, after a few decades, disappears. Then we’ll know that what we were looking at wasn’t a pulsar, a star, it was a starship, sailing between distant alien worlds.

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