Hello, and welcome back to Beyond NERVA! I wanted to give my readers an update on what’s going to be happening here this year, since there’s major changes coming soon to the blog and website!
So why are things changing, and how? Well, the last few blog posts have been an immense amount of work, and ended up turning out… not as well as I would have liked to say the least. They were great learning experiences, and I gained a much deeper appreciation for both the designs themselves and the context in which they were designed in. However, this doesn’t mean that I want to be reading hundreds to thousands of pages of technical information every week to write a post a couple times a month, and the depth of the posts was also getting a bit out of hand.
This has led me to move to a shorter post format. Rather than the 10-20 pages of single-spaced plain text that my rough drafts tend to work out to, I’m going to be going for 2-5 pages (depending on the subject matter), and try to cover at least the majority of a system in that overview. The in-depth information will continue to fill out over time on the web pages for each reactor concept that I cover in the blog, including the more technical details that I know a lot of my readers like. Sometimes I’ll have that information ready to go at the time that I publish the post, but often it’ll continue to come in over time, as I find sources and time to write.
The other big change is the focus: up until now, the blog has been following a fairly well-set path, and one that kinda-sorta is inherent to astronuclear reactor designs. However, at the rate I’m covering the subjects over the last few months, it’ll be at least five years before I’ve gotten the basics written up. While I plan on doing this for far longer than just 5 years, it’s still longer than I’d like to take getting the in-depth basics of astronuclear engineering off the ground.
Because of this, I’m splitting the blog into several columns. One of them will be the “primer” series on nuclear electric propulsion that we’ve been covering recently, but in a much shorter format (there’s a couple deep dives still to come in the series, though). This will allow us to progress through the huge array of reactors, power conversion systems, thermal management systems, and the rest of the components that go into a nuclear electric power plant much more quickly, and hopefully also in a more digestible length as well. I’ll also start going back to nuclear thermal rocket designs as well, and possibly even start rotating in some columns on the basics of nuclear pulse propulsion as well.
The next will be either Forgotten Reactors or Reactor Snapshots, looking at historical designs that either aren’t as well known, have a novel design concept, or led to a later design that we either have or will cover.
We’ll also have a column on the spacecraft, stations, or surface bases that these nuclear reactors were meant to power, as well as any interesting or novel designs, architectures, systems, or pitfalls that those designs have.
Finally, we’ll have some interspersed blog posts on… basically whatever interesting random astronuclear tidbit caught my attention that week and I felt like writing about. This post falls into that category, I suppose. This category will also include “Reader Questions” or “Q&A” posts as well, so if you have a question, either ask in the Facebook group (the best thing to do, TBH, a lot of people in there are far smarter than I am on various subjects), e-mail me (firstname.lastname@example.org) or ask in the comments section, and I will write up a blog post about some of them – but try to answer all of them, at least for the person asking. Sometimes, people’s comments get shunted into the “Spam” folder on my comments thanks to the spam-blocking software I use (it seems to be that if you’re blocking your IP address, using a VPN, etc is the likely culprit), but I review it at least once a week or so.
Hopefully, by both continuing to cover the information that I have simply not been able to find outside technical papers and textbooks as well as spreading out to more topical categories will allow me to cover more of the history of astronuclear engineering, the wide array of possible designs, and the future it offers us in exploring and settling the solar system and beyond.
The New Website
In order to get the blog to a more reasonable level, I’m going to be moving a lot of the details from the blog to the website. Up until now, most of the things that I’ve covered on the website have also been covered in depth on the blog, the big difference was that the website was more topical, with some things that just didn’t fit into the blog.
That’s about to change, in a number of ways. First, in-depth information is going to mostly be the preserve of the website, especially the more technical information. For the nuclear reactor designers, grad students, and some other technical readers, the website will be the better place to check for in-depth information on a particular reactor architecture, coolant, etc. The information will be in a far less narrative style, and for those not familiar with the technical details of nuclear reactor design, it may appear daunting on occasion.
The other part of the website that will be expanding greatly is the tutorial section, which currently doesn’t really exist. One of the consistent challenges that many people seem to run into when it comes to nuclear power in general, and astronuclear in particular, is that it’s very difficult to go from the point of “I know that this isn’t black magic, but sure looks like it from where I’m standing” to “OK, now I understand how a nuclear rocket works, and what the advantages and limitations of various concepts are.” As someone who’s self-taught in this field, I’m all to familiar with both the immense number of technical resources available and the difficulty of getting to the point that reading a technical paper and gaining useful insight from more than the introduction and the conclusions of the paper.
So, over time I’m going to be adding an “Introduction to Astronuclear” section on the website. I’m not entirely sure exactly how this is going to be done, but it’ll be a combination of a “course” (for lack of a better term) and a glossary that links to useful, astronuclear-specific (when available and appropriate) resources to learn more about unfamiliar concepts or provide an easy, quick reminder on the definition of a term to those more experienced. The course part of this is going to take a fair bit of time to completely flesh out, but it’s a desperately needed resource which is largely unavailable at the moment. The fact that there isn’t a simple “glossary of nuclear engineering” that I’ve been able to find is a major irritation, and leads me to the conclusion that I’m going to have to build one. Again, this is likely to be a long process, but hopefully the end result will be accessible and useful to both newcomers and professionals alike.
Another change that has already been happening (although not as regularly as will happen in the future) is the addition of reactor-specific pages to the website. This is going to be an ongoing project, but is beginning now. These more topical pages will be more in depth than the blog posts, including more engineering details, development history, and component information.
The Reactors Left in the Cold
Up until the 1970s, every single national laboratory, as well as a half dozen companies (Atomics International, Rocketdyne, General Atomic, Pratt and Whitney, General Electric, Westinghouse, and others), and several NASA centers (including Lewis, now Glenn) all had their own designs for in-space nuclear power and propulsion. Many astronuclear reactors are not well-known, or well-developed. We’ve looked at many of the high-profile programs from the 1950s-1970s, but few of the less-politically-favored designs. Several were designs built around a particular concept, with not as much care taken in the design as it moved away from the “interesting bits.” Several others were developed only to the point that the company involved could take out a patent. Others still were design projects that were mostly done by graduate students, a la the Stanford study that led to the original design of the Stanford Torus space habitat.
Then, the cuts to funding for space research and development, the cancellation of the post-lunar Apollo missions, cuts to the AEC – and later reorganization into the DOE, and a host of other problems chipped away at the funding until fewer and fewer organizations conducted experiments into space nuclear reactors, and only a handful continued to design reactors that they knew would never be tested, much less flown. To make matters worse, very little of the raw data, or notes on construction, behavior, etc, were kept, and so it’s difficult to reconstruct the knowledge that was gained while these experiments were going on.
This isn’t to say that astronuclear engineering is dead by any stretch of the imagination. There’s a new breath of enthusiasm and innovation in the nuclear field in general, and the variety of Generation IV reactors lends itself to a wide variety of concepts. The increased interest in space, likewise, lends itself to a resurgence in astronuclear design and innovation. The first novel nuclear reactor design to undergo criticality testing since the founding of the US Department of Energy was a reactor for space (the KRUSTY experiment, part o the Kilopower program), and already the implications of that test for small modular reactor design have spilled across a wide swath of the industry.
While there was a fairly quiet time from the mid-to-late 1970s to early 1980s (depending on what program in particular, what reporting was required after concluding experimentation, etc), with only a few major programs being pursued to a small degree, and another lull from the end of Reagan’s and Bush’s Strategic Defense Initiative and Constellation programs – again, there were a few programs, but only a few, and none with enough funding to complete flight qualifications.
Even in the golden days of ROVER and SNAP, when critical experiments, test reactors, and the like were reasonably easy to get approved, and funding was plentiful, few of the designs that were proposed ever moved off the drawing board. Despite having minimal regulatory barriers, the technical barriers were so high that every test was still a major expense. Additionally, especially early in the program, getting enough fissile material together for a test, much less the novel manufacturing, instrumentation, and test stand requirements formed a substantial set of barriers.
The list of astronuclear reactors that underwent minimal to no testing is long, depressing, and not something that I feel like trying to type out right now, and the list of tested reactors is contrastingly short, and flight-ready reactors even shorter – in fact, we’ve already covered all but one of them. This doesn’t mean that those untested reactors are without worth, in fact many of them offered potential superior qualities.
For the vast majority of problems in astronuclear engineering, it doesn’t come down to reactor physics, or to propellant/coolant flow behavior, or thermohydrodynamics, it comes down to materials science. Many of the reactors that were set aside had that happen specifically because there were materials or components that were outside the technological capabilities of the time. Examples of this litter the landscape of astronuclear history, especially when it comes to things like clad materials or fuel elements. These areas have had revolutions in manufacturing capability that have been completely independent of the nuclear industry in general, and many other capabilities that were unheard of at the time of these reactor proposals. While an in-depth coverage of these issues and their implications is going to be a years-long process, we can begin by covering the reactor proposals over the years.
Spacecraft of Futures Past and Present
Modular construction is the reality of the future. Within certain limits, spacecraft are designed around what the available engines offer, but those limits are relatively few. Similarly, reactor design can be tweaked to a certain extent to account for spacecraft requirements. This can be seen in a more mature form in aerospace: everything from the mission duration of a satellite to which airliner is going to be designed and built next is influenced by propulsion, either from the point of view of specific impulse and propellant mass and volume budget for a geosynchronous communication satellite or looking at the operational cost per pound and operational range on a next generation airliner, with everything in between.
The same is true in the design of interstellar spacecraft. Winchell Chung’s incredible Realistic Designs library on the Atomic Rockets page has an incredible assortment of information on various designs, and is an incredible resource, but each person looks at what is important slightly differently, so while I’ll extensively reference his page I hope to bring a different angle to the coverage of the spacecraft.
I hope to cover, in shorter posts, the individual bits of these spacecraft, not just the engines but the cargoes needed, lander designs, habitat structures, en-route scientific instruments, etc. While occasionally there’ll be a deep dive into a particular spacecraft, my hope is to cover particular types of systems and how they’ve evolved over time – like we briefly did with the use of hydrogen propellant for NTRs. However, design philosophies and materials advances offer the promise of better structural support for less mass, for instance, or different crew quarters concepts over the years, and the interplay between isp, mission duration, crew size, and engine capability all play a significant role in evaluating potential spacecraft concepts, and what kind of spacecraft would offer the greatest benefits for future use in various mission applications.
However, this won’t just cover spacecraft. As some of you know, I help out on a YouTube channel, Science and Futurism with Isaac Arthur [insert link], which has sometimes been called a “High Temple to Rotating Habitats.” There are many design possibilities out there, but they aren’t well-covered in many cases. From time to time I hope to either cover specific designs or aspects of the concept as a whole. For instance, at some point later this winter I will publish a longer post on the possibilities of beginning to look at creating ecosystems within large rotating habitats, the challenges that still remain, and some potential lines of exploration for those interested in looking more at the subject (as I will in the future). Other concepts, such as potential opportunities and challenges for migration in joined cylinders with artificial magnetospheres, are things that I hope to touch on in the future as well. Other, more mechanical aspects, such as bearings and seals, transportation concepts, and size optimization will probably be added over time. We’ll also look at concepts for bases on the Moon, Mars, and other planets, moons, and other astronomical bodies, and how they’ve changed over time as our technology and our knowledge of the destination have improved. Finally, we’ll look into in situ resource utilization, automatic manufacturing, and the ways that these technologies could impact astronuclear engineering (spoiler: a LOT).
More Coming Soon!
Many changes are coming to the blog and website! Keep an eye out for notifications on these exciting updates! The next blog post, and the first of our Forgotten Reactors series, is coming soon! Other developments, which are still in deep development, are continuing apace as well, and as more details get fleshed out and planning is completed, I’ll post more about these exciting opportunities and collaborations!
Our next post will be the first of the Forgotten Reactors, this time looking back at one of the earliest nuclear thermal rocket designs during project Rover: Dumbo!