IN THE 1970s, when those behind America’s manned space programme were trying to keep it alive as people got bored of moon landings, one fantasy was that there were products which might be made easily in space that were hard to create on Earth—metal foams, for example. Such dreams came to nothing because, however fancy the product, the cost of manufacturing it in orbit was never lower than the price it would have commanded back on Earth.

Two Californian firms, however, think they have cracked this problem. Made in Space and FOMS (Fiber Optic Manufacturing in Space) are both proposing to manufacture optical fibre of the highest quality in the free-falling conditions of the International Space Station. At $1m a kilogram, this is a material that is well worth the trip to and from orbit.

Optical fibres are made by pulling glass into strands which have a diameter similar to that of human hair. Cables filled with these fibres have revolutionised telecommunications. When a telephone call, say, is encoded as laser pulses and sent through an optical fibre, it can travel a far greater distance, with a lower loss of signal quality, than if the message involved had been transmitted through a copper wire. As a consequence, except for the last few hundred metres of connection to the customer, copper cabling has almost disappeared.

Optical fibre could, though, be better than it is. The glass used contains impurities that both absorb and scatter part of the light passing through it. This can be ameliorated by adding germanium, which reduces absorption and scattering. But that is not a perfect answer.

The best solution known in principle was found in 1975, by researchers at the University of Rennes, in France. It is a glass, made from a mixture of the fluorides of zirconium, barium, lanthanum, aluminium and sodium, that is therefore known as ZBLAN (sodium has the chemical symbol Na). Fibre made from ZBLAN has extremely low losses from absorption and scattering, particularly in the part of the spectrum called the mid-infrared, where conventional optical fibre does not work well.

ZBLAN fibres are, though, fragile. That makes drawing one that is more than about a kilometre long a hard task which, in turn, makes them useless for long-distance work. They also tend to contain tiny crystals that form when the material is cooling. These negate the lack of absorption and scattering that otherwise give ZBLAN its advantages.

However, in the absence of stresses caused by gravity on the cooling material, much longer fibres could be drawn. Nor would the crystals form. And the one large place under human control where such stresses are absent is the space station.

Both firms say they have built apparatus to produce ZBLAN fibres that is small and light enough to send to, and operate in, the space station. Made in Space’s machine has some similarities to the sort of plastic-extrusion 3D printer used by hobbyists. It ingests a preformed pencil of ZBLAN. A furnace melts the tip of this pencil. Thin strands of fibre are then pulled from the molten area. But instead of being used to form an object while still soft, these strands are coated with a second sort of glass for protection and then spooled onto reels for storage.

Made in Space already has a plastic-extrusion printer on board the space station. This is used to make replacements for small items that have got damaged, obviating the delays involved in bringing them from Earth. The company’s managers are therefore reasonably confident that their ZBLAN extruder will also work in free-fall.

They will soon find out. A prototype arrived at the space station in July, and will be tested shortly. An equivalent device built by FOMS will be sent up later this year. Both firms are promising fibre with a performance 100 times better than anything made on Earth, in lengths of several tens of kilometres.

To say that this is truly an economic process is cheating slightly, since the ledger fails to account for the trivial matter of the $100bn or so spent to build the space station in the first place. But, given that this is now a sunk cost, it does seem possible that Made in Space and FOMS have actually found a way to fulfil the dreams of the 1970s, and make money by making things in space.