Nixon didn't wanted to handle NASA by himself so he instead got both OMB and PSAC reviewing Shuttle designs. OMB worked on costs, PSAC - on engineering (PSAC: President Science Advisory Committee).
What happened was that PSAC and OMB had conflicting opinions about what shuttle was the best - or no shuttle at all. In my TL Explorers it didn't took much for PSAC to finally convince OMB that the large shuttle was too expensive and that more generally the space shuttle as a whole wasn't needed. My source was Tom Heppenheimer SP-4421 "the space shuttle decision". Since then John Logdson "After Apollo" shed a new light on the process and after reading it on Google Books it more or less confirmed my analyzis. That is, the space shuttle got an extremely close brush with death on late October 1971.
OTL the shuttle fate hanged to what I call the "fat DynaSoar" launched by a Titan III-L. The "fat DynaSoar" saved the shuttle because it had wings and a payload bay. Big Gemini had no such things.
A panick stricken NASA finally listened Mathematica and, frantically working from the "fat dynasoar" they managed to salvage a full scale orbiter (15*60 ft payload bay) out of it, and after three months Nixon screwed the OMB and funded it. Of course the full scale orbiter was saved at the expense of the booster and a large external tank.
In my TL I just had NASA (George Low) screw the "fat dynasoar" in September 1971. Hence when the shuttle got it close brush with death in October the "fat dynasoar" is nowhere to be seen and Big Gemini is picked by both OMB and PSAC, and then to Nixon.
Now I am confused.
It is hard for me to see exactly why the concept of a winged reusable manned vehicle with a payload bay depended on one USAF backed concept that was, OTL, still going on paper in October 1971 (if I read you right) and would be sunk if NASA (not DoD or the White House, who could "kill" an Air Force project) if someone cancelled it
just one month before a crucial decision in October of that year.
To begin with, I thought Robert McNamara killed Dynasoar Mark 1 long long before 1971.
And as DoD chief, I think he did right, given that the Air Force could not describe an acceptable military mission for it. What should have happened I think is for Dynasoar to be transferred to NASA, since it was not of particular military use (if the Air Force had defined even one distinctly military mission for it not better accomplished by other means, I believe McNamara would have signed off on continuing it in the Air Force, and of course it would then require Titan II to launch it.
As a research vehicle investigating "airplane like" low G (1-3 G versus 5-12) hence long duration atmospheric reentry from orbital speeds with high lift to drag ratio, I suppose even if Von Braun et al regarded it as a distraction from their crewed space projects, with a White House mandate and additional funding attached transferred from DoD budget to NASA, it would find a home somewhere in one of NASAs fiefdom centers, and with NASA "stuck" with it from Von Braun et al's views, they'd come around to launching it with Saturn 1 or Saturn 1B, whichever was required--thus justifying acquiring extra Saturn 1/1B orders and perhaps doubling or tripling the total number of Saturn 1 type rockets acquired and launched versus OTL.
Increasing Saturn 1B orders might in turn tip the balance toward NASA working with EELVs instead of taking on the ambition of developing something reusable--alternatively perhaps someone would look in to the idea of reusing the Chrysler made first stage.
Anyway OTL it was the Air Force's baby and when McNamara took it from them it just died. So--at what point did the Air Force reacquire a mandate to do any level of research, even just paper studies, on a new upgrade of the Dynasoar, such that there was something for Low to kill or let continue at
NASA? Was this a case of someone at NASA, one of those other centers not in line with VB and company, adopting Dynasoar as a cool idea they wish someone had done, and doing paper studies (presumably with Titan launchers, not Saturn, since all this is happening under the Huntsville mafia's radar I guess)?
Anyway, what difference does it make to the Shuttle Decision whether Fat Dynasoar existed at all?
I am assuming it was a paper project, an investigation into "what if" by a bunch of engineers more preoccupied with hypersonic aerodynamics than with NASA's main focus on craft designed mainly for vacuum operations with minimally simple ballistic capsules of increasingly known performance. Was it more than that OTL? If it were escalated to the level of authorizing building hardware, presumably scale model entry vehicles launched on off-the shelf available rockets, I would think it would have been a big big deal administratively. IIRC there were indeed tests in the later 60s of various non-capsule lifting bodies and/or winged forms for entry characteristics, done with rocket-launched scale models, from this series the eventual bi-national evolutionary course of the HL-20 lifting body form evolved. (The Soviets stole one of the American designs that was missile tested for their MiG "Sabot" spaceplane orbiter, then Americans observing Soviet tests used the photos and data we got from spying on the Soviet test for defining HL-20 in the late 80s). Was "fat Dynasoar" one of the forms tested in that series?
In any event, what is one more paper study, more or less, especially in the context of actual testing being done on various forms?
Everybody and their brother in the aerospace biz had their own Shuttle ideas before the OTL interagency showdown around NASA's high budget expectations versus Congress's "been there, done that, now shut down so we can say we saved the taxpayer some money in this economically stagnating, costly Vietnam war year" mood. As I understand it, Nixon himself had no great desire to slash NASA back--though I bet he did have a preference for NASA to shift over to doing something quite different from the Kennedy-Johnson Apollo/Saturn legacy. He saw himself as caught between any President's desire to have the public associate him with cool stuff versus Congress's budget hawk mood--with his own OMB tending to side with Congress on the matter to be sure, and NASA with its hyperbolic expectations of continuing peak Apollo funding forever forcing him to downgrade his esteem of their managerial responsibility. But had Congress been willing to fund NASA mad money with no questions asked, I suppose Nixon might have wanted to go with Von Braun's Mars scheme or some such; why not back a legacy that means quite different hardware than the Kennedy legacy Apollo, on an even grander scale? Not because Nixon didn't want it--because Congress was not going to fund it and he had higher priorities to get funded so he wasn't going to bat against Congress on this.
So--all the aerospace firms had plans for some sort of winged spaceplane with a cargo bay. (Except Chrysler, which made the launcher the focus of their reusable concept, seeking as I would to decouple the orbital payload into a generic package of given mass--but even they offered a winged spaceplane as one such possible package)! Archibald, you say that if one particular such plan--Fat Dynasoar--had not been an active program in October 1971, Low et al would be forced to fall back on Big Gemini. I just don't see that. Sure, the FG might have been the closest single design to the bare bones minimal spaceplane NASA dared to consider downgrading to. But the psychology at work here is the notion that some sort of spaceplane, specifically one in which both crew and cargo ride on, in analogy to cargo airplanes, must be made reusable and be reused, and if Fat Dynasoar was convenient to point to OTL, its absence would just prompt Low to have the appropriate center (or perhaps an inappropriate center!) brainstorm a quick sketch of something suitable--able to hold both a crew and a cargo of useful size, keep the crew on orbit for a week or two, aerodynamically reenter and land as a glider. Given that Fat Dynasoar or no Fat Dynasoar, in addition "real shuttle" designs I believe every aerospace firm anyone could name off the tops of their heads (and quite a few they couldn't) had at some point between 1960 and 1970 sketched out some suitable super-Dynasoar type thing, the NASA team mainly needs to ransack the dusty file drawers full of proposed projects to pull out five or ten of these sketches, and pick the one or two that look closest, and splice them together on the back of some envelopes to have something quite as good, once NASA artists are done with their part of the job, as Fat Dynasoar to put before OMB and Congressional delegates.
Now as it happens I think this is unfortunately silly; in retrospective hindsight, this is not what the USA needed done at all.
But let's remind ourselves of the context of conventional wisdom at the time about future generation cheaper access to space, the absolute ideal would be something that would look, from the outside anyway, either like Skylon or like Venture Star. That is, one single hull that contains within itself a) all fuel b) all engines needed to go from the ground to LEO; c) all cargo d) all crew desired to be put into space; upon reaching orbit, can then e)putter around on OMS (or ambitiously a subset of the main engine thrust) to orbital destinations or serve as a platform for launching deep space vehicles (to GTO or translunar or beyond to solar system destinations)--note it is doing so with all tankage and engine mass needed to reach orbit in the first place--then f) retrofire for g) aerobraking and some kind of precision controlled landing of the whole thing, including crew and downmass cargo, to a base suitable for minimal inspection, refurbishing (on the order of checking the oil and refueling and loading in the next batch of payload and passengers/crew to be launched again--and on the assumption that this ground servicing and general turnaround is comparable to an airplane's typical in service turn around time (h). With assumptions like that, it is quite OK if the total upmass and downmass is something in the range of 5-20 percent of the dry mass of the whole thing, thus 0.5-2 percent of the total fueled mass.
Now, today we recognize that doing this on chemical fuels (barring insane risks like using FOOF or other such foolishness) was not only insanely ambitious for 1970 state of the art tech but probably nothing we can accomplish even today, or in the foreseeable future. But in the 1960s designers like Philip Bono churned out a dozen or more systems meant to more or less meet this target, and with million pound payloads too. He may have been nuts but most everyone assumed doing it would be a matter of will; if they agreed it was too much for NASA to commit to in 1971 it was because it would cost too much at that time, given a parsimonious Congress.
OK, so the designers took one step back, and dropped criterion a&b and compromised with a two-stage design. Now engines and fuel would be split between two (sometimes more) hulls where all but the Orbiter would not carry any cargo and would not achieve orbital speeds, but would after boosting the Orbiter partway, separate and return to launch site, certainly by aerodynamic flight, landing like an airplane and jumping to h), being prepared in airplane like turnaround times to boost another Orbiter. Meanwhile the Orbiter would otherwise meet all the criteria, because dang it, affordable access to orbit would look like airplane operations and those specs above are designed around airplane operations.
And except for a few mavericks like Chrysler, this is what everyone meant going into 1971 by a "next generation Shuttle."
Then OTL, the still skeptical and tight fisted Congress and OMB balked at the estimated cost of such a two-piece TSTO Shuttle. No one doubted it could be done at all though in retrospect we now figure this too would have cost orders of magnitude more than estimated to accomplish and probably would have failed at that. But, in the desperate place NASA management was backed into, they had to postpone this ambition too, and look around for approaches with lower up front investment to get some approximation of what they wanted.
OTL, TAOS brought in two more compromises--1) eliminate the integral fly back single booster stage, replace it with SRBs that would allegedly be refurbishable with savings but turned out not to save much if anything over the cost of just making and expending new ones for every launch. 2) separate the reusable spaceplane Orbiter that otherwise stubbornly retained all aspects of the desired SSTO ideal super shuttle from its orbital boost fuel supply, which would go into an expendable tank.
Having thus sacrificed a) from the SSTO wish list completely, retaining only OMS fuel for the spaceplane, and with the b) compromise shifting the vast majority of surface launch thrust to the SRBs, and simplifying the "flyback" of the boosters to parachute braked splashdown in the ocean and recovery by boat downrange, NASA then dug in its heels and refused to sacrifice c)-h). Or rather, as you allude to, briefly it looked like they'd sacrifice the rest of b) separating the launch to orbit sustainer engines--in the Flax Shuttle, or your Fat Dynasoar, these would be disposable. But fortunately (from the point of view of their traumatized entitled mindset, focused on taking some if not all steps toward the SSTO dream, if not from the POV of a really economical and sustainable national launch system) they were able to recover that lost ground by insisting that the boost to orbit engines would be kept on the spaceplane. Thus, they convinced themselves that what they were doing with TAOS-Shuttle was developing an interim Shuttle that could meet most of the checklist, looking forward to the day in the future when they could step by step, building on experience in shaking down partial b and c-g to an economical turnaround, go back first to the TSTO (essentially replacing the SRBs with a reusable flyback booster set of some kind, and hopefully reincorporating the upper stage propellant tank back into the Orbiter) and perhaps someday even the SSTO.
Now even at this point, the two OTL pacing items delaying things in 1978, the SSMEs and the tile based TPS, might have been sidestepped, and in hindsight dispensing with the first would save a lot of time and money and avoid much schedule slip and uncertainty--at the cost to be sure of having to design around significantly lower Isp and accomplishing necessary thrust on the ground with more reliance on booster thrust, and putting a substantial number greater than 3 of developed, lower pressure than SSME 1970-mid-70s state of the art engines-I assume J-2S would be best. Note that since all off the shelf hydrogen engines were not much good at sea level, the boosters alone would have to be relied on until they burnt out--which saves some propellant mass from the prop tank, but this is offset by the lower storage density of 5.5:1 LOX/fuel ratio versus 6:1. J engines could surely be tweaked to use the denser combo I suppose.
Turning to TPS, I await
@RanulfC's clarification of just what alternatives were available; a certain sacrifice in mass might be a good tradeoff for a more robust, cheaply maintainable system. I suspect though that without some synergistic composite approach as I suggested in my previous post, the mass penalty would be considerable--but this might be overcome by sheer brute force in the SRBs and J engines, and designers would have considerably more certainty and confidence that a solution within realistic, attainable targets would emerge on schedule. But I am relying on RanulfC's word here; the impression I get from Wikipedia is that on one hand a heat sink TPS strategy would require both a heavy shield layer and a craft hot structure to deepen the heat sink further, meaning the main body could not be a straightforward aeronautical aluminum design, and on the other that while the knowledge base was more developed than the leap in the dark ceramics, no designer could actually say they had ever already designed a complete hot-structure metal TPS spaceplane to fly on any spaceplane. Missile warheads yes, spaceplanes, no. They had a lot of data from Dynasoar investigations, but Dynasoar never flew full scale full speed, crewed or otherwise. It is a shorter leap into murk instead of a long leap in the dark, but there is still some risk and cost develop, and the heavier the overall spaceplane the bigger the booster and engine set and tank must be.
Now you, Archibald, join with RanulfC in suggesting that, beaten back from a, most of b too, that NASA take another step back and compromise on the reusable engines b--either as with Flax Shuttle/Fat Dynasoar per Archibald, dispose of the orbital engines so that the entire thing is tantamount to an EELV, or develop a second recoverable unit in addition to the spaceplane still ambitiously doing c-h, to also be recovered from orbit, and reused.
In fact Archibald your goal is to regress from the ambition of SSTO like an airplane even further, having given up on reusing boost engines completely to also forget the spaceplane aspect of the Orbiter, and simplify it into Big Gemini, which violates most of g as well--it brings the crew back, but since you say it had "no cargo bay" (the versions I know of certainly did have upmass storage, so I presume you mean no downmass cargo capacity); it also, even if the optimistic Rogallo wing could be developed in reliable form for such a large capsule has less precise ability to target a landing site, and maneuvers in the upper atmospheres at higher G's than the goal for spaceplanes. It also uses an ablative, nonreusable heat shield--this might be designed to bolt on and be quickly replaced with a new one to be sure. IIRC, in throwing away the lower tier of the structure before reentry, where the cargo and extended habitat are discarded, it also discards the bulk of its OMS capacity as well, engines along with tanks. This raises the question of how much money if any is saved by reusing the core crew volume.
In being backed into this extreme regression from Shuttle development as the next Big Thing, NASA is giving up on having anything moving them toward the visualized El Dorado of a reusable space plane. In this case,
there had better be agreement to budget some operational program using a minimal cost Big Gemini on expendable launcher, almost certainly Titan III--which in 1971 is just barely becoming operational in non-man rated form! Or of course revival of Saturn 1B, but that ship alas has sailed already, and the Air Force hates it anyway.
Now all of us agree that in hindsight, the goal of the SSTO space shuttle, with airplane like turnarounds and costs higher than airplanes chiefly due to higher propellant costs (which are small compared to other real world rocket costs) was a pipe dream, and that what NASA might have done better to focus on, in the face of the refusal of Congress to fund Mars missions, ongoing Moon exploration, or any other gloriously ambitious deep space program, the choices boiled down to either taking a very clean sheet, critically thought out development of a hardheaded cheapening of space launch freed of irrelevant analogies, or else used the money saved from no dramatic cost to orbit reduction initiate as generous a LEO program as Congress would fund (Eyes Turned Skyward approach) and hope that the politicians would be more generous in the future, and that with gradual commercial development of incrementally cheaper launches, NASA would slowly, with building experience and perhaps orbital infrastructure, be able to do more with less someday. My own notions for the rational way to quickly and effectively develop cheaper tonnes to LEO as an investment that might pay off would be to develop a spaceplane that just does e to h, with downmass perhaps reserved for special high cost, high mass later developed models, and do this either concurrently with or (with a hiatus in American manned space ability, or a costly continuance of Apollo or revival of Gemini derivatives) focus on a launch system that first of all cuts costs drastically in the boost phase--I would say, by developing a single standard LRB design that like OTL SRB for Shuttle splashes down in the downrange, but thus recovers tankage and engine for many reuses. This standard booster would be strapped on to central LH/LOX tanks of various sizes, with variable numbers of J engines on the bottom, and the boosters used in variable numbers to raise these tanks of variable mass, each tank/engine set design being developed successively for increasingly ambitious mass to LEO targets, with payload on the nose. This is a far cry from the vision of the self-turnaround single stage Shuttle, but I believe the LRB could be developed very soon after deciding to do it in 1971, and the first tank/engine combo to design two of them to boost would be essentially carried over from the top stage of the Saturn program--about 100+ tonnes of LH/LOX propellant with a single J-2S; the combination should just about match Saturn 1B, but the boosters are recovered and reused, and using a single modified booster and a smaller hydrogen stage one has a competitive booster for the early 70s developed commercial market. The two booster design is sufficient to boost a reasonable sized crew only spaceplane, small enough to use an emergency escape system in case of launch mishap and perhaps its smallness favors the use of simple heat sink metal TPS design too--and it could be a capsule instead of spaceplane. Thus even with the foundation of the launch system postponing a new American crewed vehicle program, Apollo and Gemini derivatives both being scrapped, and the new crewed vehicle having to wait until say 1976 or '77, when its launcher in basic form is undergoing tests, American crewed launch capability should be back no later than OTL, but this assumes even lower NASA budgets in the 70's. With the money and commitment promised to STS by Nixon OTL, and the crewed vehicle program progressing on the back burner until the launcher is ready and then brought to full speed, American astronauts could return to space perhaps half a decade earlier than OTL, with a hiatus perhaps eliminated by ordering a few more Saturn 1B and Apollos to close the gap. After developing a man-rated two booster, 1 J-2S launcher/orbiter combo by '77 or so, the next thing in the lift rocket track is to develop a space station module lifter, with 3 or 4 boosters and maybe going over to 2 J engines, for payloads in the 30-60 tonne range, which might be as far as NASA needs to go for decades. Using the two-booster version, and maybe bigger ones if the space launch market really booms, this design could lift every commercial, scientific and military payload the USA generates as well as catering to foreign customers too, and cut the costs substantially below EELV OTL.
BUT--doing it that way involves contradicting everyone's conventional wisdom, in every age. It falls between the stools of the EELV advocates, who can afford existing expendables and see little purpose in spending NASA dollars on cheapening launch (in competition with their private partners!) and the Shuttle dream, which sneers at these unambitious seeming, pathetic half measures. The latter had the endorsement of every visionary in the aerospace world. My proposal is basically a moderate tweak on say Delta, the variations seeming too trivial to invest public money in, the private sector seeing no guaranteed and expanding market to justify a speculative venture to shareholders.
Going to Big Gemini violates the dream of the Shuttle and is a complete capitulation by NASA to the Air Force.
Developing the Flax shuttle is about as far back into the corner as NASA is likely to be pushed and still survive. And even the Flax shuttle does not conceive of the crucial decoupling I think would be part of any truly economical system--which is, to separate the payload from any recoverable stuff.
Would a Shuttle Orbiter stripped of the Main Engines, whatever engine that may be, really have much cheaper and faster turnaround than with them? The overall system, if we are reusing main engines, still requires that they be refurbished and reused eventually, so the system still waits on that process, wherever it happens. Meanwhile a crew capable Orbiter that also carries all the cargo can only deliver a fraction of its total mass as cargo. Instead, a modest mid-range launch system can alternate between putting up an HL-20 sized spaceplane with minimal to no cargo, and pure cargo payloads with no crew; if it is ever essential to do both in one launch, we can make a bigger launcher, and a still bigger one to enable downmass.