I think this is an important piece of context that really bears highlighting. Projects LUNEX and Horizon were both, to varying degrees, service-based flag-planting vehicles which were never really serious about what they were wanting to do. They also both had not real military idea what to do with the Moon other than that their service's flag fly over it. I think LUNEX was the more honest of the two -- in that the USAF wanted to do it, but had no earthly idea what it'd practically entail -- while Horizon was straight-up cynical Pentagon politics. (I mean, there's more of the Collier's "Man Will Conquer Space!" article in Apollo than there is Horizon, which is telling.)
Actually I'd argue that Horizon by it's nature had more "Collier's" than LUNEX which was strictly more closer to Apollo than the former given it was essentially a "flag-n-footprints" design whereas Horizon was "built" (unrealistically to be sure) around a "military base on the Moon" as a basic goal. (Providing enough fodder for US Army Weapons Command "Future Weapons" Division to jump on the band-wagon in 1965 Horizon looked to a permanent presence of both humanity and the military in space and on the Moon. (Unsurprising given who was involved in both Colliers and Horizon) LUNEX, like Apollo, only looked to a single immediate goal and how to resolve it. Any long term "planning" (beyond ensuring Air Force supremacy and requirements) were left to some "later" date.
What I've labored on is creating a different context entirely. The Navy's people are tackling this as a serious military question, attempting to identify what will be done in space, what the Navy should be doing, and how to go about doing it. It's why MAVEN and PRISM look so different from LUNEX and Horizon, as they're not being treated as PR exercises or make-work. Which also changes the logic of cost-estimation, as if you lowball things to the extent LUNEX did and it doesn't stand-up to independent audit, you've just destroyed your credibility in representing this is a serious product of military thought. And also because no program survives cost-inflation on the scale of going from LUNEX to Apollo would, at least in normal budgetary times. (Which, even if they don't know what Peak Apollo Money is, they know going to the Moon is going to take more than $1,750MM the USAF estimated in LUNEX.) So better to at least try to keep your costs where you think they'll actually be and just deal with sticker-shocked Congresscritters.
Whether that's actually enough, though, is another question. At least not without an outside intervention or two. ...beyond Sputnik, at that.
To be honest ALL the 'studies' at least tried to find justification for a military presence in space the main issue was there was little actual justification to be had. Oh there were plenty of USES for space with things like satellites but when it came to the assumption of needing personnel (as in people) up there everything suddenly became hugely more expensive and complicated with almost all 'justification' ending up being "humans are better than machines" at a time when machines were proving better than people.
Arguably the Air Force came into the 'race' both from an outdated premise, (space can be used to bomb people from manned space bombers!) and kept continually trying to work in ways to keep both the "manned" and "bomber" aspects long after the expiration date had gone by. (Dyna-Soar/X-20 being a prime example as it was always meant to be an operational rather than experimental vehicle and as such very little 'cross-support' was sought from anyone outside the Air Force leaving it vulnerable to cancelation as the Air Force literally never had a viable mission for the vehicle)
The Army at least kept some sense of space being the ultimate "high ground" (Horizon after all was 'supposed' to entail ending up with military missiles on the Moon aimed at Earth) while the Navy (OTL) focused more on the utility of space as it related to Naval surface and sub-surface operations. Both lost out to the superior Air Force PR and Congressional lobbying machine which saw most of the "space" missions handed over to the Air Force and many of which were 'shelved' simply because the Air Force was too focused on chasing the unclear 'shadows' of capability for missions it would never clearly define.
The trouble is that OTL the Air Force quite effectively used the fact that they didn't have a clear 'plan' to allow them to avoid defining either budgets or clear proposals (thereby avoiding 'discrediting' themselves) while at the same time claiming any and all 'success' as part of those ill-defined "plans" thereby gaining 'credit' for being forward looking and the obvious 'choice' to lead US military space efforts. (One of my 'hoped for' time-line concepts is what if the Army had retained the long range missile folks/mission )
Here the Navy is taking a huge leap (and I applaud it btw ) by sticking their necks out to actually define and plan for a viable militarization of space to the extent of not only seeking practical concepts (the Air Force mess that was SAMOS is a good story to read to get how trying to 'side-ways' a manned space capsule program disguised as a reconnaissance satellite can go wrong) but accurately addressing how to get from point A to point B rather than just assuming the "and then a miracle occurs" thing in-between just happens when needed.
Well, the purpose of bringing up that 1955 study was -- more than anything else -- to get Team Heinlein's eyes on the prize nice and early. Whether their funding situation lets them do anything with it for the foreseeable future is something else, at least in the absence of Taylor and Dyson shopping it for General Atomics, which won't be for a few years yet. But yeah, Stan Ulam was thinking about since the Manhattan Project was still underway, and operating principles go back even further as you illustrate.
Well it makes sense in the context it was just that Dyson/Taylor-et-al were needed to figure out HOW to make it work as Ulam's concept was really just a though experiment. Having said that...
Re: control of nuclear weapons, what I'll say is this: That might actually be a feature and not a bug. Sort of. As, if you do fly Orion, the service that controls will require a complete nuclear weapons assembly line to service their atomic rockets. That production line does not, necessarily, have to be the same one which furnishes the American strategic and tactical nuclear weapons pipeline. An entirely separate assembly line for pulse-units opens up possibilities to mitigate the concerns of a runaway arms race by subjecting that assembly line to a different arms control regime -- one whose requirements would not otherwise be tolerable for strategic weaponry -- and perhaps provide grounds for actual agreement between the Americans and Soviets on that front. (You still have the problem of building that assembly line out of loose bits that don't implicate your strategic bomb-building methods, but that's essentially an engineering problem. And a financial one, as "we want to build an entirely separate nuclear production line from fuel enrichment/creation to bomb-assembly" is not something that's going to be cheap.)
It's actually a lot deeper than that and as is pointed out in the "Orion" book by one of the pulse-unit designers the implications of JUST even how you design the pulse units and the path that leads down (Casba-Howitzer for example) means an awful lot of your ability to even consider a viable 'arms-control' environment goes right out the window if Orion drives are around. The ability to produce thousands of 'bombs' (and while pulse-units are lousy bombs they are still bombs) a month skews your capability to produce 'regular' weapons even if you keep the "lines" totally separate on paper.
Couple that with the fact that as noted above the design process and requirement to increase the efficiency of the "pulse-units" tends to lead towards certain lines of research both in miniaturization and energy direction (CB above) and your deterrence environment suddenly evaporates as now the 'need' to actually land a bomb near a target is replaced by the ability to literally vaporize any 'target' on Earth from hundreds if not thousands of miles out into space...
Meaning an attack can literally come with almost no notice... Ya, there were a number of sound political reasons for avoiding deploying Orion despite how much of an awesome concept it is. You end up with having to develop things like the "Mini-Mag Orion" to get it t be politically viable and frankly that negates a lot of it's advantages. (Like being able to deploy to stop a short-notice impactor for example)
So, Sirius is a Rocket of Unusual Size, is it?
Or, on second thought, you probably were suggesting it worked for the competition.
I mean, given who's heading-up rocketry for the Army, it's entirely possible it's working for the competition. Von Braun's going to bat for anybody that gives him a decent budget and the hope of shooting for the Moon.
If you have to explain the joke... :::sigh::: guess I was to circumspect on this one:
To whit: Military nomenclature being what it is and how the container marking system works a container delivering a "Sirius" rocket would be marked:
"R. U.; Sirius"
Why yes, yes I am. Quite Sirius in fact