As NASA makes plans for the lunar Gateway, it should design for longevity. (credit: NASA)
by Taylor Dinerman
The proposed lunar Gateway, a space station in lunar orbit designed to host crews for months at a time, is, under current circumstances, a bad idea. It will, if it is done in the traditional NASA way, lead to it becoming useless just at the moment when it would be needed to support a crewed Mars mission in the 2040–2050 time frame. If, however, NASA were to rethink the project and build it to last, something good might come of the effort.
The future of the International Space Station currently being debated shows what kind of problems the Gateway project will face if it is designed to fit into a limited budget. NASA’s current plan is to cease US funding for ISS operations in 2024 and hand over responsibility for financing the station, or develop commercial successors to it, to commercial interests. In any case, the ISS will likely have to be abandoned in 2028 or at latest 2030. Essential parts of the station, including the seals between the modules and the joints that operate the solar arrays, will be in danger of wearing out.
Unless solutions can be developed to fix these problems, the whole $100-billion complex will have to be abandoned. One hopes that, in this case, it will be pushed into a so-called “thousand-year orbit,” where it can fly around awaiting the day when it can be recovered and perhaps converted into a space based museum of early astronautics.
Based on what we now know about the plan for the Gateway, a similar fate could be in store for this new human outpost. But it does not necessarily have to be this way. As long as this station is designed to have all its elements repaired and replaced on a regular basis, there is not theoretical reason why it should not operate for even a century or more.
This means that NASA and its partners will have to make major investments now. Getting the design right means ensuring that the whole system will be robust enough to not only survive the harsh environment of cislunar space but also flexible enough to support future spacecraft and modules, which may include technologies that are as yet undeveloped or even unimagined.
NASA’s plan to build the Gateway’s Power and Propulsion Element (PPE) based on a pre-existing commercial satellite design is probably a good one (see “Powering the first element of the Gateway”, The Space Review, July 23, 2018). The design will be refuelable, which should be a clear requirement. However, if the plan lacks an option to completely replace the PPE at some point in the future, perhaps in the late 2030s, then it’s a sign that NASA is repeating the same mistakes it made with the ISS design. Improved solar arrays and more efficient forms of electrical propulsion will certainly be available and, without the ability to easily install such systems on the station, the project’s prospects are not all that promising.
A commercial logistics module is also being planned. This is another sign that NASA is serious about maximizing the commercial side of its mission. The fact that NASA will allow the logistics module to be launched on something other than the SLS is a sign that the Gateway will be designed to handle a wide variety of spacecraft.
If the Gateway is equipped with seals between the modules that use more advanced technology than those on the ISS, including the ability to last for many decades and which can be replaced or repaired either by robots or by simple astronaut spacewalks, then NASA could have a station that could last for many decades.
Another critical future problem could involve the docking mechanisms. Currently the only crewed spacecraft that is planned to use the Gateway is the Orion, flown on the large Space Launch System (SLS). The SLS is both behind schedule and over budget, but it is politically secure, at least for now. There is also the possibility, though, of SpaceX’s very large, reusable BFR connecting to the Gateway. The requirement that the logistics module be equipped with a universal docking mechanism shows that NASA is taking this into consideration, but the Gateway designers should consider the possibility that current docking standards may change over the course of the next few decades.
At the moment, neither NASA nor anyone else has any idea what kind of crewed deep space vehicles will be available decades from now. If the Gateway is to be a true long-term asset, then its design should be adaptable enough to be used by future spacecraft. This may mean that the whole docking system should be replaceable or that it should be flexible enough to mate with any as-yet-unimagined vehicle.
In the near term, the concept proposed by Lockheed Martin of a lander that would serve as sort of lunar taxi to shuttle between the Gateway and the lunar surface seems worthwhile. However, other ideas, particularly from SpaceX or Blue Origin, should be expected. If NASA were to follow a full-on commercial pathway, then perhaps the Gateway might have to deal with two or more types of these spacecraft.
Let’s have no illusions: the Gateway is a huge building project. In his incarnation as a real estate developer, Donald Trump did not build his projects to last for two or three decades before being torn down, so it would be unfortunate if his administration were to start work on a space station that would be as ephemeral as structures they put up in Bryant Park for New York’s Fashion Week.
The fate of the US human spaceflight program is, as always, in the hands of Congress. Neither party has particularly distinguished itself, but last year’s increase in the NASA budget may have been due to the desire of both the President and his party, as well as the Democrats, to find a sort of compromise. The GOP wanted a big increase in defense spending while the Democrats demanded that any increase for defense be matched by an increase in civilian spending. One of the places in the civilian side of the budget where both sides could agree to spend more was on NASA. While officially civilian, NASA is also an important element in US national power of both the hard and soft varieties.
If Trump and the Democrats reach a similar compromise next year, then it should not be too difficult to find the extra cash needed to build a “hundred-year” Gateway. If not, then NASA and Congress would be well advised to reconsider the whole project.