As an aerospace materials engineer, it's taken me a surprisingly long time to realize that the most useful property of space is not microgravity; it's the vacuum.
There are a number of modern testing processes that rely on vacuum or near vacuum.
Testing materials, I've frequently seen vacuum chambers used in electron microscopes (SEM and TEM) and for various high precision spectroscopy methods (where air can get in the way). Also, x-ray generating tubes are in vacuum. These devices are all notably expensive and are very limited in chamber size (a few inches in diameter).
At the bottom of Earth's N2/O2 atmosphere where humanity currently resides, creating a vacuum requires a pressure chamber with a door, and (usually at least two stage) pump system. If this sounds like an air lock, that's because it very much is. Guess where the best place for a materials lab is on your spaceship/station?
It also means that a lot of test equipment that, currently on Earth, is quite large due to pumps and cryogenics, can be made into handheld portable devices for specific use in a vacuum environment (whether by a suited human or by robot). Such materials testing devices are key to
- prospecting (finding desired materials)
- beneficiation (separating raw materials)
- manufacturing (quality checking)
- engineering (failure analysis)
- basic science (material characterization)
In aerospace, we routinely use large vacuum chambers to vet space hardware prior to launch. Of course when you are doing the manufacturing in space, this step becomes trivial.
Speaking of manufacturing, perhaps the most lucrative use of vacuum lies in the various chemical vapor deposition (CVD) techniques that grow thin uniform layers. This is predominantly how silicon wafers are doped for use in microchips and how transparent conductive films are applied ubiquitously to touchscreens and photovoltaics. Many nanotech fab methods currently rely on CVD, including carbon in its various rare forms (bulk graphene, diamond, nanotubes). In space electronics, parylene film is routinely applied to printed circuit assemblies via CVD as a hard thin insulation layer to prevent tin whiskers from shorting circuits. Metal (Fe, Mo, W, Ni) carbonyl methods have previously been proposed for space manufacturing, as they logically follow from a particularly efficient extraction and storage method.
So imagine, if you will, the ability to manufacture space tethers of continuous strands of nanotubes grown uninhibited by vacuum chamber walls. Imagine a giant x-ray gun big enough to scan an asteroid, and imagine a swarm of spectrocopic sensors to identify and map the fluorescing elements within. Imagine graphene-steel composites for making ultralightweight solar sails and pressure chambers impervious to hydrogen permeation.
But wait! There's more... . Remember astronaut ice cream? Lyophilization, otherwise known as freeze drying, is a niche market on Earth due to the expense of vacuum chambers required to sublimate frozen water out of food. At the New Worlds conference a few years ago, someone asked my panel what the kitchens on Mars would look like. My response was that I thought pressure cookers would be used a lot due their efficiency, compactness, and safety. However I think now, especially that water is known to be quite abundant on Mars, there is an argument to be made for putting food out the airlock for preservation and storage. While standard freeze drying by itself is generally considered insufficient to kill microorganisms, I suspect that irradiation would do the job. Imagine the cuisine to arise from this method: perhaps lapin (rabbit) tartare, kale-tilapia pemmican, and various flavor infusion reconstitutions.
While the vacuum industry will certainly help to open up space development technologically, the products will also enhance life on Earth, and provide the capital incentives to get this new vacuum industry off the ground. Literally.