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Trade. It enables, disseminates, and helps pay for new technologies and skills. It encourages sciences, the arts, and communications across oceans and cultures. It is a requirement for the evolution and supply of settlements and cities. Like technology and physical expansion, trade is a defining characteristic of humanity. It is impossible to overstate its importance in human history and development.

So, how do we get trade, and all of its ancillary benefits, started on the new frontier of space? After finding things to trade – like lunar or Martian scientific knowledge or lunar water – trade is most likely encouraged by making both the upfront and ongoing costs of space transportation and operations as low as possible. That requires the most efficient possible use of whatever transportation is available. One way to increase efficiency is to employ a concept the trucking industry calls‚“backhaul.”

The administration of Donald Trump challenged NASA to aggressively return astronauts to Earth’s moon, and to prepare for going on to Mars. President Joe Biden’s administration appears to support continuation of that vision. A young administration confronted with a Congress precisely balanced between bitterly fighting political parties is unlikely to want to spend its limited political capital squabbling over space policy. That encourages continuity.

There also seems to be a new sense of reality at NASA. While senators appear to have headed off any attempt to cancel NASA’s vastly late and over-budget Saturn 5-class Space Launch System and freeing the resources it consumes for more useful purposes, NASA is doing what it can to minimize the SLS’s lost opportunity costs. Payloads that Congress baselined for the SLS have been moved to cheaper commercial rockets. NASA picked SpaceX’s largely self-funded, Starship-based lander for the Human Landing System. Boeing has been strongly urged to improve their dismal performance managing SLS — though there is little sign of that actually happening. Nonetheless, it is becoming possible to believe that a “lunar gateway” station, and maybe even early visits to the lunar surface, could actually occur – if not by 2024, at least within the decade of the 2020s.

In an early, lunar transportation architecture dependent on the expendable SLS, the astronaut capsule alone will return to Earth — usually with a small amount of spare volume and mass. Later when reusable spacecraft ply between Earth and her moon, and supplies are transported in one direction, empty or partially filled vehicles will return to be used again. Since the empty vehicles produce no value beyond returning for reuse, anything that allows space on them to be used or sold is a net gain for the transportation provider. In the trucking industry, goods “backhauled” in this way often pay extraordinarily low rates, subsidized by the primary purpose of moving the outbound goods. Crucially, the outbound cargo can be totally unrelated to the inbound backhaul.

Early first-generation vehicles will be severely constrained in both volume and mass, but even then backhaul may be relevant. Returning crew capsules could carry small items stored “under the seats.” These might include lunar samples desired by companies or scientists, or even wealthy individuals, in addition to those wanted by NASA. Low-mass ornaments or jewelry, like glass beads from ancient lunar volcanic “fire fountains” and other collectible mineral grains, whose value comes solely from their being obtained on Earth’s moon, are possible high-value items. Possible rare, high-value heavy elements or rare-earth elements collected from asteroid impact sites could be used in orbit or on Earth.

Tiny but abrasive and chemically reactive lunar dust particles can damage equipment and human lungs, so all samples need to be properly stored in sealed containers. After arrival on Earth, they must be cleaned before distribution to nonscientists.

Later, if second-generation lunar crew transportation vehicles were reusable, backhaul opportunities become much more attractive. After dropping crew and supplies off at a lunar base, cislunar supply vehicles would return empty, or with smaller return cargoes, to low Earth orbit or elsewhere in cislunar space. At that time, backhaul might become a real market.

The International Space Station and future semi-commercial stations, Lunar Gateway, applications satellites, and other activities in cislunar space need water and oxygen for propulsion, drinking, and breathing – both of which are readily available on Earth’s moon without having to lift them from Earth’s surface. Oxygen can be derived from oxidized surface rocks available in many locations, not only from polar water deposits. Water, because it is useful or necessary for so many things in so many places, has been called the “oil” of the solar system.

If NASA were to establish a science base on Earth’s moon, lunar water or oxygen might be backhauled for use at the cislunar facilities. If the market grows large enough, a dedicated lunar-to-LEO tanker industry could evolve – which might never happen if the infrastructure for supplying space facilities with lunar water had to be paid for up front and from scratch, before any water was delivered.

Backhaul allows trade to start small, possibly very small, early on while transportation infrastructure is still rudimentary. That could increase early income from lunar activities, amortizing some of the costs and encouraging growth, leading to earlier development of largescale commercial or semi-commercial industrial stations or orbital tourist facilities. Costs could be spread over multiple activities, in this case both science and commerce.

Similar ideas for incremental development are not new. Companies developing a new technology often take an incremental approach, earning money on partial solutions while developing their better mouse traps. SpaceX was able to parlay testing retro-propulsion deceleration technologies needed for their Falcon 9 reusable first stage —using rocket engine plumes to protect the vehicle during reentry — by trading test data useful for potential Mars missions with NASA.

The space agency flew aircraft with advanced thermal imaging sensors to observe reentering test vehicles paid for by SpaceX, and shared the results. NASA got data it could not otherwise afford while SpaceX got the data they needed to perfect firststage reentry without having to fly their own sensors.

Later, SpaceX went a step further. The company tested reusing Falcon 9 first stages while launching operational satellites for paying customers. The test could take place after the first stage had completed its operational mission of delivering the second stage and payload to the needed trajectory. The customer paid for the launch — presumably at a somewhat reduced price to accept the risk of flying with experimental hardware on board — while SpaceX got their test data without having to pay for a dedicated test launch.

The advent of a new partially commercialized lunar strategy is exciting, but it remains true that no lunar base is likely in the immediate future. That means no returning vehicles with excess capacity to sell cheap.

So, let’s look closer to home. There are already operational flights that could offer backhaul opportunities. Right now, there are three vehicles delivering crew or cargo to the ISS and returning to Earth: the Russian Soyuz, the SpaceX Crew Dragon, and the SpaceX Cargo Dragon. Soon the Boeing CST-100 Starliner and Sierra Nevada’s Dream Chaser will join the mix. Returning Soyuz and other returning crew vehicles have little excess capacity. Dragon Cargo is another story.

Dragon Cargo can return 3,000 kg in 10 cubic meters from the ISS. Because of various constraints like available volume and operational needs, Dragons usually do not return with their full theoretical capacity in cargo. On most return missions, small amounts of space could probably be found for backhaul. Soon, Dream Chaser will also return with substantial cargo capacity.

So, what might we backhaul from the International Space Station?

A company called Made In Space is deploying a series of ever-improving 3D printers to the station. Currently, these are used experimentally to make tools and parts needed on the station.

It is not hard to imagine using excess capacity or a second machine to print small novelty items for export to Earth on returning crew or cargo capsules. Such items might be quite valuable to those interested in space exploration, or in owning something truly unique. If backhaul costs were low enough, and especially if the prospective objects incorporated some property that could only be made in space, the market could be significant. If one entrepreneur makes a profit, others will follow, each with their own take. Some might even invent something useful that cannot be made on Earth.

While NASA has traditionally been resistant to using publicly owned infrastructure for profit-making businesses seen as frivolous, attitudes are changing. The Russians have fewer qualms, and one module already is privately owned and rented by NASA. Further private modules are planned for the very near future. If someone wanted to start a small business that used backhaul to get its products to Earth, they could probably find a way to do it, especially if production could be automated and not use valuable astronaut time.

If a few small businesses succeed, they could grow. At some point, volume might grow high enough for a consortium to purchase full-priced transportation to Earth. At that point, a mature industry will have arrived, and a trading economy will be firmly established.

Trade will have achieved yet another breakthrough for humanity — helping to pay for our expansion into the final frontier.

Donald F. Robertson is a freelance space industry journalist based in San Francisco. Follow him at @DonaldFR.

This article originally appeared in the September 2021 issue of SpaceNews magazine.

Donald F. Robertson is a retired space industry journalist and technical writer based in San Francisco.