I'm writing a sci-fi book where the main method of travel involves collapsing a star into a black hole by putting a satellite equipped with some sort of handwaving mechanism into orbit around the star. The satellite can then direct a beam of energy with a cross-sectional area the size of the black hole itself (ex. our Sun's Schwarzchild radius is just shy of three kilometers, so that would be the radius of the beam created out of a black hole from the Sun).

Once the spacecraft enters the beam, it enters a "free-fall" accelerating at about 51 G, to a maximum speed of about 10 000 c. The satellite can send messages to the spacecraft instantaneously at any point along the beam, but the spacecraft can't communicate back - only receive. A property of this beam that I'm bringing into the story is that the process of traversing the boundary in or out triggers a massive EMP that fries anything electronic on-board. The satellite observes the EMP from its orbit and calculates the time at which the spacecraft must exit the beam to reach the next system, and communicates this to them. Because of this, the engineers on-board the ship have to repair the communications array after every entry and exit of the beam. For the same reason, physical mechanisms for basic things like life support, lighting, etc. are highly preferred. Transit time in the beam (and therefore maximum time to fix the communications array) varies, but would typically be a month or so at most.

My question is whether, after leaving the beam in the new star system probably up to as far as a few AU away from the star, what would be the bare minimum of electronic components related to the calculations needed to plan the burn length, timing, thrust, etc. and control for these mechanisms that would need to be repaired/replaced to be able to accurately deploy the satellite into a near-zero-eccentricity orbit within 0.1 AU? Bear in mind that these missions are decades long with dozens if not hundreds of jumps, and new resources would need to be acquired from each successive system (ex. chemical rocket fuel extracted from a gas giant or from the star itself prior to collapsing it, minerals from asteroids or rocky planets, etc.).

EDIT: Have accepted an answer from @Starfish Prime, but received lots of good suggestions in comments as well. I am now aware of the issue with EMPs injuring humans as well, so will be modifying the mechanism accordingly.

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    $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Nov 13, 2023 at 19:05
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    $\begingroup$ Let me play devil's advocate for a moment. (a) The satellite beams energy in a diameter equal to the black hole itself. Why bother with the satellite if there's no need for compression? If there's need for energy compression, where's the satellite getting it? (b) Do you mean 10,000X the speed of light? ("10 000 c") Free acceleration cannot exceed the speed of light in any way we know of. $\endgroup$
    – JBH
    Nov 13, 2023 at 19:38
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    $\begingroup$ Having said that, I don't believe your question can be rationally answered. EMP is nothing more than the same use of magnetism to generate electricity using a generator. Apply a moving magnetic field to a long enough length of wire and you create current. Do it fast enough and you create a spike that burns things out (I've experienced that). In other words, you can rationalize there being no reason to fix anything at all by simply minimizing the wire lengths and using well designed ESD (electrostatic discharge) circuitry. Note that digital has nothing to do with it. $\endgroup$
    – JBH
    Nov 13, 2023 at 19:40
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    $\begingroup$ Note that humans are electrical conductors. Any kind of EMP sufficiently strong to fry hardened electronic circuits will most definitely be strong enough to fry the crew. If you have a means to shield the crew so that they don't get fried you can use the same means to shield the computers during the transition. $\endgroup$
    – AlexP
    Nov 13, 2023 at 20:18
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    $\begingroup$ @JBH Thanks for the additional context. It's best to just consider the beams to be magic for now. I'm trying to stick to hard science where I can, but when that can't be the case I at least want to be internally consistent. Appreciate the feedback, and I've addressed the EMP hurting humans point now too. Will see what I can rework it into. $\endgroup$ Nov 13, 2023 at 22:20

4 Answers 4


Electronics isn't the only way to do digital computation, you know. Fluidics is a particularly robust alternative, though not necessarily very fast or compact... clock speeds might only be in kHz at best, so it would be outperformed in terms of raw speed by something like the Apollo guidance computer. Have a read of A brief history of liquid computers. Fluidic amplifiers allow a small, low-pressure fluidic logic system to control much larger, higher pressure systems, so your control logic can interface with big stuff to make your spaceship work. The systems can be pressurized using a pump driven using a something like a sterling engine warmed by a nuclear heat source... perhaps an RTG, but a whole fission reactor isn't out of the question, the operation of which a fluidic computer would be ideally suited, being quite resistant to radiation (System Shock 2 has a fluidic system that handles radioactive stuff, though I don't think it went into detail of what it was, or what it did). You don't have to have power-generating equipment attached to a reactor, so it could be quite EMP-proof. This seems like a sensible basis for running life support, too.

For something a bit faster though, how about "phononics"? Phononic computers might be run on waste heat, perhaps from the same nuclear heat source that drives the fluidic minimal support systems. The Orion's Arm setting had "ultimate chips" using phononic computation, though I don't recall coming across it in other scifi works. I don't see why a phononic system couldn't interface with a fluidic system, using the latter to do the actual heavy lifting whilst the phononics does the important thinking.

(Photonics also exists of course, but I think it has too many points of contact with electric systems to be guaranteed to work under the circumstances, but stuff like plasmonics and polaritonics not only sound awesome but present the possibilty of very fast, if not necessarily very compact, digital computation. Interfacing with external systems in the absense of electrics might be difficult, but it might work using fluidics again and chemical lasers might bootstrap your optical systems until you've got electrics up and running...)

And it can only get weirder. Belousov–Zhabotinsky computers anyone? Running on chemical reactions? No?

Your EMP effect apparently doesn't frazzle the meatbags on the ship, so neural computation clearly isn't out of the question... lab grown neural tissue and musculature to operate valves and control rods to fly the ship. Organic bioreactors to brew up fresh replacements to deal with attrition. Maybe not even artificial, but cunningly adapted and modified living organisms, with a big of clever genetic engineering and surgery. Finally a justification for living, at least partially organic (cybernetic!) spacecraft. Peter Watts called his take on neural computers "smart gels" (or informally, "brain cheeses") in his Rifters books (free to read on the author's website), and whilst he had electronic interfaces for his creations, you can now see that there's no reason to be limited by that.

The big question I guess is the nature of the EMP... remember that a severe enough electrical disruption can work on meatbags, too. Careful construction of the ship could minimize the number of long metal conductors which link to any electronics, and if the electronics themselves are disconnected and sealed in Faraday cages prior to the "jump" they should be safe. I get the impression though that you don't just want a system where you unbox a perfectly working set of electronics after each jump and carry on business as usual, and that means your EMP is going to be kinda magic, and as such giving any more useful insight is basically impossible because that's the nature of magic.

  • $\begingroup$ Thanks for all the different suggestions and considerations! And yeah, the EMPs having an impact on people as well is for some reason something I thought wasn't an issue? No idea how I got that in my head. For now I'll say it's something akin to an EMP that does specifically damage circuitry, not people. Big fan of the fluidics option, particularly as that's a very reasonable way to point out that AI, even if it has been developed in my universe at this point, can't conduct trips of its own as anything with the necessary computational power would be reset every "jump". Thanks again! $\endgroup$ Nov 13, 2023 at 21:21
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    $\begingroup$ don't forget mechanical computers! (which are, supposedly, surprisingly viable for computation) $\endgroup$
    – somebody
    Nov 14, 2023 at 9:01
  • $\begingroup$ @somebody Zuse's mechanical computers were apparently pretty good as a general computation machine $\endgroup$
    – Seggan
    Nov 14, 2023 at 15:17

If physical space on board is not at a premium - then this could be done with an Analogue computer:

Iowa Class Fire Control Computer

Now - granted, this is for a firing solution, but your basic functions of Pi, Reciprocals, Addition and subtraction, multipliers etc. are all there. If it's sole purpose is to calculate orbits, then with a sufficiently precision machined components - perfectly doable.

Of course, the accuracy of the output will be largely determined by the accuracy of your inputs such as:

  • Mass of the body you are orbiting (or the gravity of the body you are orbiting)
  • Mass of the object.
  • Initial velocity.
  • Desired orbital height.


Some of those could be manually input (e.g. desired height) the rest could be fed from an analogue source continually (if you really want to go old-school)

  • $\begingroup$ If it weren't for the rather massive metal hull of an Iowa-class battleship being in contact with all that electrically conductive salt water, the analog fire control computers would be as sensitive to EMP as any digital computer today. Probably more so due to all the wiring. $\endgroup$
    – JBH
    Nov 13, 2023 at 19:42
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    $\begingroup$ @JBH Eh? It's all shafts and gears and wonderful mechanical things? Unless I've missed something key - (the electric motors perhaps?) Things like ships speed (in the real one) I think were mechanical inputs and although they did eventually use radar for target course/speed for input, these could be input manually $\endgroup$ Nov 13, 2023 at 19:48
  • $\begingroup$ I apologize, I wasn't clear. The hull of an Iowa battleship is (from the perspective of what the OP is talking about) a giant faraday cage. When you and I say "analog," we're talking about the same thing. The difference is that the analog "computing" circuits of the Iwoa battleships used really long wires that would be very susceptible to EMP if it weren't for all that grounding capacity. From a practical perspective, if the OP wanted to avoid repair altogether, he/she should use a mechanical Babbage difference engine. $\endgroup$
    – JBH
    Nov 13, 2023 at 21:01
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    $\begingroup$ @jbh - Oh I see, I probably should have been clearer in my answer then - I was thinking that all those long cables would be replaced by long shafts (ooo er vicar!) and it be completely mechanical - more akin to the babbage engine - but perhaps with an electrical drive motor. $\endgroup$ Nov 13, 2023 at 21:05
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    $\begingroup$ Additionally, mechanical devices aren't immune to electrical disruption. A common design of reaction wheel was found to have a high failure rate due to a small current through the bearings caused by the space environment. Especially in high-precision, compact and lightweight mechanisms, an EMP could spot-weld sliding or rolling components or cause cumulative surface damage that increases wear and friction. $\endgroup$ Nov 13, 2023 at 23:38

There is no need to have digital computers on board of the rockets and spacecraft, and the first pre-1960 year rockets likely did not. Here is quite detailed description of R-7 that started as a ballistic nuclear missile but later made basis for first Sputnik I launcher and many later flights. If any computer would be present, I assume should have been mentioned. Here is even more detailed explanation about this rocket (in Russian), no computer mentioned.

All that digital computers could provide can be achieved with the help of calculations that have been carefully prepared on the ground and pre-set timers (when to fire the engines and for how long). If alterations are needed, the pilot can receive instructions from the ground over the radio that also does not need to be digital.

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    $\begingroup$ Or the pilot can make calculations themselves during the flight, like ship captains used to long before any computer was invented, using logarithm tables to make the calculations simpler. $\endgroup$
    – Stef
    Nov 15, 2023 at 9:31
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    $\begingroup$ Also true. Simple devices like log ruler or mechanical arithmometer can help a lot with this. Tables can be prepared for some pre-computed data. $\endgroup$
    – Nightrider
    Nov 15, 2023 at 9:53

You can use conventional electronics, but you would probably have to out it into some shielded mode before the EMP. If you don't know exactly when it might happen, you may have several computers, some running and some not.

The crudest from of 'shielded mode' might be sticking everything in a Faraday cage. A better version might be to separate the memory and processing chips from their motherboard, so there are no long lengths of wire next to the sensitive components. The smaller the components are, the less EMP they should pick up. However, it talks less EMP to destroy a small component.

One of the places I used to work had an EMP testing rig outside my widow. They put armoured vehicles into it and tried to toast the electronics. I imagine the EMP you are thinking about may be considerably larger than the sort of thing they were testing, but if people survive, then a computer probably can with the right precautions.

  • $\begingroup$ In addition to a shielded mode, just make everything massively redundant and design for a certain amount of failure. $\endgroup$ Nov 14, 2023 at 20:54

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