Reusing, refueling, partnering – and going nuclear

Advocacy for innovation is always challenging, with much written about difficulties like the valley of death. There is one barrier that does not get much attention, though. We forget the future is always outnumbered in the here and now.

Artist concept of Demonstration for Rocket to Agile Cislunar Operations (DRACO) spacecraft, which will demonstrate a nuclear thermal rocket engine. Nuclear thermal propulsion technology could be used for future NASA crewed missions to Mars. Credits: DARPA

This seems obvious but does not get the press it deserves. Advocates for what’s new are, at best, stand-ins for a future organization, vast but vague. These other people may (or may not) exist one day, manufacturing and operating the new product. The initial effort, data, and its advocates are the ghosts of Christmas future, showing what might be to an incredulous Scrooge. Except here, the spirits reveal a bright future and ask you to help make it so.

Franklin C. Spinney was among the first to dare say the obvious implications of a fact of life – an existing, well-funded project is at an advantage, using its funding to get more funding and to ensure it sticks around. Then, as if that’s not enough, they insert themselves into the meetings about what’s next. This becomes your audience for that incredible but new technology. An already established project buys a seat at the table to decide the future. Worse, and too often, they own the table.

This week NASA and DARPA announced they would work together on a new nuclear thermal engine to be tested in orbit. Why nuclear? Well, a more powerful engine will reduce trip times to Mars, or anywhere for that matter. Faster trips mean less time for the crew in zero gravity with its well-known adverse health effects.

Faster, shorter trips also mean less accumulated radiation exposure for the crew. Radiation adds to health risks as if the effects from the lack of gravity were not harmful enough. On the International Space Station, the Earth’s magnetic field provides protection from radiation (though not altogether.) So, as a rule, if you leave Earth’s orbit and its magnetic field, make it quick.

None of this is new, as speedier nuclear propulsion was NASA’s plan as recently as 2009. We will see if the NASA/DARPA announcement takes on substance this time or remains aspirational.

From NASA “Ares V Utilization in Support of a Human Mission to Mars” (Ares V, aka what became the SLS/Space Launch System.)

Yet a lot has changed since 2009. Nuclear propulsion will now compete with other means to the same ends (and none of these other paths has the words “nuclear” or “uranium” drawing regulatory attention.) At its simplest, a lower price for NASA (or anyone) to get more mass to orbit could reduce crew health hazards in ways other than nuclear engines and their faster trip times. More (cheaper) mass to orbit could mean more propellant, which could also mean faster trips. This is especially so with in-space refueling for your spaceships. This is in development by many companies, most notably for SpaceX Starships, one of which will serve as a NASA lunar lander. More, cheaper mass could also mean adding more radiation shielding. Lastly, a holy grail, the ease of putting mass into orbit opens up the possibility for rotating structures creating artificial gravity.

But let’s go for broke. More propellant, more shielding, and maybe even gravity, and all of it going faster with (fission) nuclear engines – what’s not to like? (Did someone say fusion? Even better.)


And yet, as the NASA and DARPA “nuclear” announcement trended, I could not help but see a similarity to other well-justified paths that still faced enormous difficulties. Just because it all sounds so good does not mean everyone comes running to help. Consider reusability and launch. If ever there was a conflict of interest, it was a room filled with people debating more affordable, reusable launch systems, launching much more often, with most of the people invested in expensive, expendable hardware. It should surprise no one that the decades-long decision-making around what would come after the semi-reusable Space Shuttle went as it went.

First, we saw (airbreathing) spaceplanes ahead, then single large reusable rockets, then two (even three) smaller reusable stages, and finally only a tiny reusable spacecraft – the Orbital Space Plane, atop an expendable rocket. The last death throe modified the length to diameter, or L/D, and turned the OSP into an expendable capsule, which became Orion. Reusability was crushed in every cycle, literally.

But as stakeholders go, we learned in 2010 why they are called “stake” holders.

A casual observer would say that reusable Space Shuttles, the orbiters, and the workforces at Johnson and Kennedy were well invested in reusability. These were no small armies in the field of battle. That was the unstated assumption ending the talk about balance among groups advocating one direction or another. Missed until it was too late was realizing no one made new Shuttle orbiters. Lacking manufacturing, operators were quickly seen operating anything if the thought was keeping Johnson or Kennedy busy. Full reuse in a new system would eliminate most parts of the older Shuttle program, but a system throwing everything away (but based on Shuttle) would not. So why not keep everyone around – with a new, expendable rocket.

Similarly, refueling ships in space was an idea whose time had come. (Refueling is a close cousin to reusable launchers, opening the way to reusing hardware already in space.) Curiously, refueling appears in the same report as the nuclear propulsion option for Mars. But as stakeholders go, we learned in 2010 why they are called “stake” holders. Chartered by NASA, our team accepted the mission knowing if we failed, the secretary would disavow any knowledge of our actions. Fail we did. And disavowed we were. Again, selling a great new technology to decision makers that are also stakeholders seeing themselves losing out from the change gives new meaning to “a tough sell.”


Yet time has a way of proving that physics is what it is, and dollars must add up too. By the oddest turn of events, NASA invested in a small company called SpaceX. They turned an initially expendable first stage into a reusable booster via landing legs and figured out how to reuse payload shrouds too. With their Starship, they hope to make a fully reusable launcher, booster, orbital spaceship, and all.

The moment NASA signed its first partnerships to get cargo to the ISS should have been noted, like the launch of a new rocket or fresh pictures from the Webb telescope.

As you can’t keep a good idea down, refueling has also made a comeback. SpaceX and other companies like Eta Space, Lockheed, and United Launch Alliance are working with NASA to develop in-space refueling technology. This is the technology the mere mention of which became verboten in NASA over a decade ago. Limits on the size of any one launch mean the amount of propellant and spacecraft that might leave Earth orbit is also limited. To get around this, assembly in space follows, inevitably, as does topping off your tanks. Eventually, reuse again follows, refilling the same tanks on the same ships in orbit, over and over.

Yet the most remarkable breakthrough in NASA (or even SpaceX) in recent years may not be a technology as much as a relationship. The moment NASA signed its first partnerships to get cargo to the ISS should have been noted, like the launch of a new rocket or fresh pictures from the Webb telescope. Going commercial should be up there with going nuclear. Physics helps keep great ideas alive, but incentives make them grow. The right audience, decision-makers, and stakeholders are like rich soil for planting seeds. Eliminate the conflicts of interest, align incentives properly, assure a growing space sector is everyone’s goal, and the garden will prosper.

The writer Upton Sinclair said – “it is difficult to get a man to understand something, when his salary depends on his not understanding it.” For going nuclear when going to Mars, the path ahead may be just as convoluted as it has been for reusability, in-space refueling, or NASA going commercial. And the story on these is still being written. What I can share is never to be surprised by how things work out, if the stars align, and incentives.

2 thoughts on “Reusing, refueling, partnering – and going nuclear

  1. I’m surprised you didn’t mention why DARPA (and by proxy the US military) is interested in nuclear rockets: to enable fast reaction military spacecraft, especially within Lunar orbit. As such I doubt funding will go away, or design goals shrink as the MIC is infamous for getting all the money it wants. In fact, as other nations start matching US abilities in space this (or projects for similar end goals) will get significant amounts of funding.

    The biggest question would be how much of these new technologies will be available for commercial companies or NASA to use. Though I feel that once the first reactor in space is safely launched and used most hurdles to using them will at the very least be lessened.


    1. Time will tell how much funding DARPA puts into this, as they will lead the project. Curiously, the news said “NASA’s Space Technology Mission Directorate (STMD) will lead technical development of the nuclear thermal engine” while then saying right along “DARPA is acting as the contracting authority for the development of the entire stage and the engine.” In either case, from a time I worked with DARPA (as NASA), it’s possible the public will never know the funding amounts at all. So the news bits will be telling. More news as time passes, about flight hardware, and ground tests, will be the best sign of real progress. Lack of news, not so good.


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