How large would a space civilization have to be to build computers from scratch?

Question

In my story, humanity has wiped itself off earth (salted nukes, to be precise) and survives as a large remnant civilization in the asteroid belt, with small bases on the moon and possible mars.

As the plot begins, my main character is a self employed ship owner who scavenges the remains of satellites around earth looking for microprocessors, which are one of the only things that her civilization still cannot produce. Because a processor is needed for every ship, several for a colony or for a factory, they are incredibly valuable. Ideally, one successful find can fund refuelling her ship, and supplies and rations that would last her months.

Is it plausible that a spacebound civilization, that produces rocket engines, life support equipment, tube radios, and large space stations, would be incapable of producing microprocessors, and so would pay the equivalent of millions of dollars for each scavenged unit? Would the radiation environment in space make producing computers more difficult than it is on earth?

Going off the answers to this question about recreating a computer in ancient times , building a computer is incredibly hard. My space civilization necessarily has pretty good material science and manufacturing capabilities to even survive, but I don't know if it could devote the thousands of people needed to set up a photo-lithography plant. In addition, the existence of expensive but very powerful scavenged cpus should discourage efforts to make new computers unless they can be mass produced, since a million dollar hand-made computer capable of ten megahertz can be replaced by buying access to one thouandth of the processor time of your settlement's i7 based mainframe.

Answer 1

As a bit of a tangent, if the technological base is too small or narrow to recreate computer chips and microprocessors from scratch, then some sort of alternative will be created to fill the gap.

If we consider that "computer" was a job description at one time, your space going civilization could quite literally go back to having rows of trained mathematicians sitting at desks to work out calculations. If you consider that "computers" worked for financial institutions, insurance companies, the military (creating ballistic tables, for example) and engineering firms, they you would not be surprised to discover that the United States had a huge pool of computers available to support the war effort and especially the Manhattan Project during the 1940's.

Using humans as computers is time consuming and resource intensive, so alternatives will be sought. Mechanical computers have been possible since the Babbage Machine in the 1800's, and indeed the Antikythera mechanism is considered to be a form of analogue mechanical computer.

We can carry on with vacuum tubes and other electromechanical devices, but you get the idea.

Answer 2

It seems unlikely that they’d be incapable of producing microprocessors at that scientific level, but if they were unable to replicate the precise interface and specifications of old Earth chips, there would still be a value and necessity to scavenging.

A nuclear apocalypse extensive enough to force humanity off of Earth sounds severe enough that knowledge loss could happen to the collective human species. If the surviving humans lacked the collective knowledge to replicate the super-advanced microprocessors that their remaining technology relied upon, scavenging would be critically important to continue operating old-Earth technology. Even with an old microprocessor in hand, reverse engineering a black box (and its internal black boxes) without documentation is a substantial challenge.

But beware: an industry to manufacture these chips will exist eventually. In addition to the potential profit due to their value, it’s clearly a matter of survival for the species. Not only are there a finite number of scavengable chips out there, but eventually age and the harsh environment of space is likely to render the entire lot useless for your needs. When that day comes, you better hope someone figured out an alternative.

Answer 3

Would the radiation environment in space make producing computers more difficult than it is on earth?

Yes. From the Wiki page on Radiation Hardening;

Due to the extensive development and testing required to produce a radiation-tolerant design of a microelectronic chip, radiation-hardened chips tend to lag behind the most recent developments.

So, take all the difficulties of creating microprocessors, crank it up to 11 with the necessity of making them radiation hardened, and try to accomplish that task in space with high levels of cosmic background radiation. Very, very difficult. I like Thucydides' point that a "computer" used to be "one who computes," and that this spacefaring civilization might have to largely rely on manual computing. And yes, the cost of providing for hundreds of mathematicians is incredibly high. With humanity living in places with little natural protection from cosmic background radiation, a radiation-hardened chip that could replace hundreds of skilled mathematicians would absolutely be a treasure.