27 January 2019

Big Computers, No Problem

A long running joke about Traveller has been the size of computers for starships, usually measured in displacement tons as being unrealistic. I find it to be acceptable because of what the machines are doing, the actual size of shipboard and mainframe computers, and general requirements. Also, traditionally, space opera has had large computers. A bit of background, I was assigned to a Ohio-class submarine, in Travller terms, a TL7 design with extensive TL8 electronics, and specialized in working with the computer system for the strategic weapon system.

Close enough to a displacement ton. Original
A Model 1 computer takes up one displacement ton of the ship's volume. Considering a DTon is defined as exactly 13.5 Cubic Meters, that can be hard to visualized for those of us who don't deal with volumes every day. I found this from a moving company on how big their 15 cubic meter trucks are. Moving boxes are a good substitute here. Fan Lore in Traveller has been the Model 1 computer is roughly equivalent to a Cray-1 from the 1970's. Sized up, one of those units was 263 cm across the base, and 196 cm tall, taking up a volume of 10,647,740 cubic centimeters, or 10.64774 cubic meters. Throw in a bit of space for an operator, access and some ready spares, and 1 Dton is a nice round figure for design purposes.

Official US Navy Photo, Original
As a strategic weapons system tech, I worked in a space just like the one at left. The brown doors in the background house various FCS components, and are integrated into a large scale forced air cooling system. Most of the doors contain power supplies to Versa Module Eurobus racks. Others have older, bulkier systems that have not been phased out, or high frequency AC power rectified into DC. Each one of those islands is about a Dton and a half of space. The beveled edges on the overhead into the islands are fan plenums, for cooling, and the deck is raised for an air return. Not pictured are the flat-panel displays for system control. I have said there is a minimum size for control units based on sophont physiology and ergonomics, so I don't see those getting much smaller. Also, there are various other computers running sonar and fire control, navigation, and communications.

Now, let's talk about commercial servers. Rack Units support servers and other high-end computers, and can take up a fair bit of space. The standard one is 6'(180 cm) tall, 19" (48.26 cm) wide, and 36"  (91.44 cm) deep. That gives a volume of about 0.8 cubic meters. A bit small, but add a few together, the connecting cables, power equipment, and soon there's enough for a displacement ton. Looking at those specs, the computers used for other purposes on ship are about a standard enclosed Rack Unit in size. Computers in space are not small things.

A shipboard computer is doing a lot more than my current Windows 10 laptop, and when running normally procured software, is bulletproof in reliability. It's a computer that is running mission critical programs realtime programs with minimal failures under normal conditions. It's also operating in all sorts of unpleasant conditions for a computer, where it can get jolted around in bad weather during atmospheric operations, spaceframe lightning strikes, before it gets into weapons effects. While with the appropriate software and libraries, you could run it off a commercial personal machine, but a ship is best run on a toughened system. Also, there are requirements for heat removal and power distribution. Most personal computers are designed for operations in ambient temperatures, and users do not notice the heat unless it causes issues. The ThinkPads used on the ISS require extra heat removal. Mind you, when artificial gravity works, normal thermal currents will remove the heat from personal gear, but the big iron will always need forced cooling. The way I see it, a shipboard computer is going to consist of multiple, redundant CPU's running the same task and 'voting' on the most correct solution, and toughed against 'normal' abuse. Starting adding in cables, ventilation, and power supplies, the space adds up quickly. These systems are abstractions, not gospel.

Now, why are more advanced computers taking up more space? Well, as I see it, many of them are shipboard server farms at introductory tech levels. Also, it could be an exotic technology that requires extra space to maintain states needed. Some people have recommended requiring archaic technology in starship computers as they may not work in Jumpspace, or it makes it eaiser to repair on low tech worlds out on the fringes. I prefer a simpler approach. Higher model numbers are, more or less, server farms aboard the ship, with the ability to switch from 'role' to 'supercomputer' very quickly. A model 6 computer can run several intercept programs, run an active countermeasure program, and control the ship's M-Drive at the same time. This is non trivial work that a modern system requires a separate machine, plus control cabinets spread through out the vehicle in use. Again, we get into ergonomics of equipment, and at some point, padding the size just so components can be handled and not lost is going to occur. The nature of Jump Travel alone is going to require extensive computer work. I am not that keen on exotic physics, but I think of Navigation programming as reducing frightfully complex mathematics that make the most students wilt, to making it possible for almost anyone willing to learn to astrogate.

Generally, environmental requirements, history, and reliability, including maintenance, needs are going to drive computer size as much as anything related to hardware performance. The space for power supplies and cooling requirements is much under appreciated by fandom. As a relic of the fiction that set up the game, large computers make sense, as well. So, just let the large scale computers continue to exist. Perhaps the farm of quantum computer running a starship require constant gravity, specialized power, and a high degree of shielding to keep operating.


  1. Very informative article. Thanks.

  2. Hi Michael, remember, the commercial server racks, HOLD (ie are mount points for) units that are 19" or 23" in width (telecom goes by an older standard in many cases). So the rack itself, the cable management, power management and air flow control are outside that 19" space you are discussing.
    Plus, given that today's technology can not even begin to touch on deriving many physics issues from first principals (n+ hard equations) and that a lowly model 1 can perform projected quantum tunnelling math in under 24 hours, then we can assume that we are dealing with quantum computers with associated support classical systems. In today's terms, that means building sized computers, far beyond what traveller is asking for.
    I am not saying that your article is wrong, just that it has not gone far enough. If we where being realistic using what we know today, the volume consumed by fuel should be more realistically be consumed by computer space and heat dissipation arrays.

    1. You've gone a bit farther than I was aiming for. I'm not trying for gearheaded realism, but was going for a reasonable suspension of disbelief.

    2. Understood, but most of the people who make the arguments about computers and moores law etc., don't realize that we are hitting the wall of moores law, combined with a rise in complexity that will make the old building sized mainframes look small. They just don't understand that their home computer is for all intents a toy when it comes to what is needed for even simple physics modelling let alone what is expected of the simplest model 1....