The toxicity of hypergol fuels is what it is. I personally would not advocate the use of hypergol fuels. However I wrote my proposal from the viewpoint of how things were in the Soviet Union. And history shown they had little problem with the use of hypergol fuel.
This is certainly true, if we mean to say that they went ahead and developed such engines for extensive purposes. Not only is the Proton to this very day a workhorse launch system, cited in some places anyway as the cheapest one in terms of cost to put a ton into orbit, but the entire arsenal of Soviet and post-Soviet Russian ICBMs and most smaller missiles are all hypergolic. The military has pretty much standardized on it, where the US military rockets from ICBMs on down have generally gone over to solids instead. Presumably if the Soviets and their successors felt that problems with hypergolic systems were not manageable, they too could have adopted solids, or some other conceivable alternatives. Well, they haven't. Even very large ICBMs tend to be a lot smaller than launch vehicles--less true of the Soviets who had more trouble making smaller warheads and achieving the precision targeting that makes smaller warheads effective, but generally speaking you can't put up a Soyuz spacecraft on an ICBM.
Except in the sense that the "Soyuz" rocket is in fact an old ICBM, the same old R-7 Semyorka that launched Sputnik 1. Somewhat stretched and upgraded, but OTL no cosmonaut has ever gone up into orbit on anything but this old kerosene/LOX design of Korolev's.
You'd think by now they'd consider Proton shaken down enough to switch over to using it for manned launches. It would enable larger spacecraft than Soyuz, or sending a Soyuz farther. But they don't seem to ever try it.
The simple fact is that the N-1 design was unworkable as of 1967.
That most certainly is a fact. Of course in 1967 the Saturn V was just being put through its very first launch tests.
The difference, a general difference between the two programs, is that long before putting a stage together on a pad, Americans would test new engines for many many years, in extensive firing tests. The Soviets were more in the habit of conducting few static tests, and then throwing it all onto the launch pad to see if it would fail in operation, or not. As a result they had a lot of failures on the pad, working out bugs that American practices would often find long before anyone put it all together into a stage.
In 1967, neither the N-1 nor the UR-700 was in sustained development.
Now you say...
While Chelomei was demonstrating that he could get large launchers to work with the UR-500/Proton. With a Venus race the Soviet is going to go with whoever they think can get a tran Venus Spacecraft by the 1972/1973 launch windows.
I think I need to point out this--a UR-700 is
not a Proton.
(pictures below hot-link to source article)
This is a Proton:
Or to be exact, this is what Chelomei had ready to hand, demonstrated, in 1967.
The source of the picture and others to follow is Mark Wade's Encyclopedia Astronautica. The picture caption states:
Proton 8K82 as flown in the first four Proton launches. This version had the shorter second stage of the GR-2 ICBM version, but lacked the cancelled UR-500 third stage. Payload with just two stages was hardly better than the much smaller Soyuz 11A511 launch vehicle.
Credit: © Mark Wade
Note that the picture, as a cutaway showing tankage, can be a bit confusing; the first stage has six of the flanking fuel tanks that bear the six engines--these were in fact the same engines Glushko offered for Korolev's N-1 early draft design in 1962. (As they were hypergolic engines Korolev rejected them). The six tanks look at a glance like boosters but the first stage is one unit composed of modules (the tank units being designed to be able to be carried on Soviet railways, so that the rocket, originally intended to be an ICBM, could be constructed at a central plant and then shipped to be assembled at diverse and distant missile bases). The central large tank contains hypergolic oxidant, the outer tanks hydrazine-type fuel.
In November 1968, the three-stage "Proton K," the thing we now think of as a basic Proton, was finally ready to launch. The picture below gives a better idea of what a definitive Proton looks like:
It is of a rocket launched in 1991.
Wade remarks, i
n the first article I got the first picture from:
Development of the Proton began in 1962 as a two-stage vehicle that could be used to launch large military payloads or act as a ballistic missile with a 100 megaton nuclear warhead. The ICBM was cancelled in 1965, but development of a three-stage version for the crash program to send a Soviet man around the moon began in 1964. The hurried development caused severe reliability problems in early production. But these were eventually solved, and from the 1970's the Proton was used to launch all Russian space stations, medium- and geosynchronous orbit satellites, and lunar and planetary probes.
But he also says,
in the next article the second pic is from:
Remarkably, due to continuing failures, the 8K82K did not satisfactorily complete its state trials until its 61st launch (Salyut 6 / serial number 29501 / 29 September 1977). Thereafter it reached a level of launch reliability comparable to that of other world launch vehicles.
Obviously the fact that 60 missions had flown by then, only a few of which were complete failures, suggests the authorities were being remarkably strict and perhaps some of the delay of official certification of the design was due to political spite. Still, it rather underscores another remark Wade makes about the rushed effort to put the capable K version of Proton together (and the lame compromise of the first version). And note that while the period '62-64 plagued both Chelomei and Korolev with vacillations of policy with the regime not settling on any choice in particular, it November 1964 when Chelomei got a definite green light to develop the UR-500 as a launcher to send men around the Moon. So, it took him four years of effort, backed up by at least two years of paper planning before that, to get a half-assed version of the definitive Proton-K, the first capable of that 1964 approved mission, onto a pad.
The overall launch record of the Proton-K Wade gives seems impressive enough:
Failures: 4. Success Rate: 87.10%. First Fail Date: 1972-07-29. Last Fail Date: 1986-11-29. Launch Price $: 50.000 million in 1994 dollars....
First Launch: 1968.11.16.
Last Launch: 2000.07.12.
Number: 31 .
So how bad could those four failures be?
Well, that brings me to the UR-700 you suggest was a nice easy incremental step up from the UR-500 design.
Here's a UR-700, designed for the Chelomei's proposed direct descent/ascent one-cosmonaut lunar landing mission (to be followed up by more ambitious missions using multiple launches to be sure):
Here's a picture of the RD-270 hypergolic engine, that Wade calls "the Soviet answer to the American F-1:"
Now note that the UR-700 launches on nine of these puppies. I believe though I might be mistaken that the outer tanks, in addition to feeing the six outer engines, also cross-fed to fuel the central three as well; then the outer six tanks and associated oxidant tanks would drop off, leaving the central tanks to feed the central three engines to constitute a functional second stage. The third stage, which does use the engines developed for Proton, is still clearly modified, with the fuel tanks and oxidant tanks modified to be the same heights; this would place the Lunar stack into parking orbit.
Even that third stage is clearly not simply a Proton but one could make a case it was substantially ready once the Proton original version was demonstrated.
One can hardly say the same for the lower dual-mode cluster!
Here's the full text of Wade's article:
Glushko N2O4/UDMH rocket engine. 6713 kN. UR-700, R-56 stage 1. Development ended 1968. Isp=322s. Developed 1962-1971, largest rocket engine ever built in the Soviet Union, answer to F-1. Tested but cancelled before combustion instability problems solved.
Authorized for development in the 1962-1971 period, the RD-270 was Glushko's answer to the US F-1 rocket engine and was the largest rocket engine ever built in the Soviet Union. It was to be used on Chelomei's UR-700 lunar vehicle or Yangel's R-56 monster rocket. The UR-700 would have used 6 RD-270 in the first stage. No design bureau would attempt anything like it today. It was the maximum possible power from the design: gas and gas mixture in the combustion chamber; two gas generators in the combustion chamber; one oxidiser rich and one fuel rich; closed cycle; staged burning; very high pressure in the combustion chamber (266 bar compared to about 80 bar in many today, except the SSME). Thrust was 640,000 kgf. Hot fire tests had started (with 40 done) and some units had been proved. Engine head testing had started. The peak of problems had almost been surmounted when all the N-1 lunar program was closed down and efforts had to stop. It never was used on a flight vehicle and funding ran out before combustion instability problems could be solved. Wet Mass: 5603 kg wet. Engine Cycle: closed staged. Feed Method: turbopump.
Application: UR-700, R-56 stage 1.
Characteristics
Thrust (sl): 6,272.000 kN (1,410,001 lbf). Thrust (sl): 639,573 kgf. Engine: 4,470 kg (9,850 lb). Chamber Pressure: 261.00 bar. Thrust to Weight Ratio: 153.24. Oxidizer to Fuel Ratio: 2.67.
AKA: 8D420.
Status: Development ended 1968.
Unfuelled mass: 4,470 kg (9,850 lb).
Height: 4.85 m (15.91 ft).
Diameter: 3.30 m (10.80 ft).
Thrust: 6,713.00 kN (1,509,142 lbf).
Specific impulse: 322 s.
Specific impulse sea level: 301 s.
First Launch: 1962-71.
So--a challenge, a big challenge, and hardly an article anyone could claim was ready to hand in 1967. Wade seems undecided on whether it could indeed have been make to work. With "only" combustion instabilities to solve, it might seem so, given a bit more follow-through. But these were the very things Glushko himself cited in this same late '60s time frame when he confessed he had no confidence he, or any Soviet engineer, could match the American F-1. At the time, indeed, we ourselves had not fully mastered the tendency of the huge combustion chamber to develop those instabilities which would destroy an otherwise working engine in very short order, and Glushko was sure to point out too that even American success was hardly guaranteed at that point. Yet he went ahead and tried tackling the same problem head on in a hypergol engine that ran at even higher pressure than the F-1!
The UR-700 absolutely needed these monsters to work. The alternatives--well, eventually, Soviet designers (possibly Glushko himself) did develop a very powerful kerosene engine that I believe did exceed the thrust of an F-1 or even the improved F-1A (which would make it, not the RD-270, the biggest Soviet engine). They sidestepped the combustion chamber instability issue by using four separate chambers (fed by a common turbopump system, but feeding IIRC into four separate nozzles, so there might be controversy about whether it is one engine or four clustered ones I suppose).
Or, adopt the same solution Korolev and Mishin favored--use lots and lots of good smaller engines, such as Chelomei had ready to hand for Proton. Well, with each of these RD-253 engines generating 1474 kiloNewtons of thrust at sea level, he'd have needed to use either 27 or 39 of them, depending on whether the UR-700 used only 6 RD-270's to launch or used all 9 on the pad. (In each case, I rounded up to the nearest number divisible by 3, since the design relies on three-fold radial symmetry. But in the higher thrust case the proportionate number is indeed just short of 39).
Now I think it is clear, the main argument against the N-1 being a practical design itself is the large number of ker-lox engines on the first stage. The original design called for 24 in a ring around the stage bottom diameter; then later when Mishin felt the pressure to try to provide enough launched massed for a Lunar orbit rendezvous lunar landing mission in just one launch, he added another cluster of six in the center to bring it to 30. We see plainly here that without the heroic solution of an RD-270 engine, Chelomei would be facing the same challenge of successfully ganging together even more engines.
Whether it really was impossible to lick the N-1 first stage problem of many engines or not will remain an open argument for AH. A consensus I've seen emerge and support is that the last six engines were a bridge too far; they had especially problematic plumbing, and what really gets me is that the dang things were only meant to burn for a small fraction of first stage burn anyway--just 30 seconds or so out of two minutes. If the Soviets can accept that they don't have single launch capability to the Moon but they might well have considerably more than half with one unmodified N-1, then two-launch missions capable of considerably more style and much safer margins than Mishin's OTL early Seventies attempt come into play, and successfully shaking down the simplified N-1 might happen sooner than the failures of the 30 engine version. Given a standing start in late 1967, they probably still can't beat the Americans to the Moon--but with Venus landings on the agenda, I submit that they won't skip the Moon even if it is years late, for the Moon might prove crucial for extended Venus operations, and anyway is good practice.
So--to make UR-700 work, we are looking at exactly the same sort of extended, delayed development process that might also have made a useful version of N-1 work just as well.
The choice is hardly the slam-dunk between a "working" rocket and a paper one you suggest. That's like saying the Saturn 1B is the same thing as a Saturn V!
And how likely are the Soviets to prefer a hypergolic rocket over a kerosene one, for this kind of purpose?
Well, Chelomei designed yet more versions of rockets he called UR-700s, but take a look at the one he offered up for multi-launch Mars missions ("Aelita"), designed over a 4 year period starting in 1969
This is the UR-700M. It doesn't look much like its predecessor, does it? And why is it not the -900 instead?
Well, he did propose another hypergolic evolution. And this is what happened, to quote Wade in the above linked article:
By January 1969, Chelomei was proposing the UR-900 for the Mars expedition. Chertok asked Chelomei what would happen if, God forbid, such a booster exploded on the launch pad. Wouldn't the entire launch complex be rendered a dead zone for 18 to 20 years? Chelomei's reply was that it wouldn't explode, since Glushko's engines were reliable and didn't fail. Aside from that, these propellants had been used in hundreds of military rockets, deployed in silos, aboard ships and submarines, with no problem. Fear of these propellants was irrational. Related propellants were used by the Americans on the Apollo manned spacecraft.
Less than three months later, on 2 April 1969, the unimaginable happened. A Proton rocket, one tenth the size of the planned UR-900, was launched in an attempt to send an unmanned probe to Mars. The leadership of the Soviet Rocket Forces and most of the Chief Designers were present for the event. The Proton rocket lifted off, but one engine failed. The vehicle flew at an altitude of 50 m horizontally, finally exploding only a few dozen meters from the launch pad, spraying the whole complex with poisonous propellants that were quickly spread by the wind. Everyone took off in their autos to escape, but which direction to go? Finally it was decided that the launch point was the safest, but this proved to be even more dangerous - the second stage was still intact and liable to explode. The contamination was so bad that there was no way to clean up - the only possibility was just had to wait for rain to wash it away. This didn't happen until the Mars 1969 launch window was closed, so the first such probe was not put into space until 1971.
This accident seems to have made a powerful impression on the military, and plans for a new generation of space launchers drawn up in the early 1970's specified use of non-toxic liquid oxygen and kerosene propellants. This also forced Chelomei to specify these propellants in the redesignated UR-700M for the Mars expedition.
It would seem then that even Soviet generals and apparatchiks, hardened and indifferent though they may be to public opinion, gung-ho to press on, and desirous of streamlining expensive technology into shared systems the military can use along with the space program, don't need to be shown more than twice. Or three or four times perhaps...the kopeck eventually drops.
By the 1970s, it was clear enough that the liabilities of cryogenic propellants were manageable enough, anyway when a launch is planned and requires a large rocket. It is one thing to manage a release of toxic (very, very, toxic, and otherwise obnoxious in many ways too) propellant for something the size of an ICBM. Quite another for something massing 4823 tons, most of it hypergol propellants, seven times the mass of a Proton-K. The energy release of a failed UR-700 alone would be literally in the kiloton range, as in small nuclear bombs!
If the hypergols had a significant edge in performance, they might have reconsidered yet again--but the fact is, Soviet designs from the later 60s of both hypergolic and kerosene-LOX engines were quite good, on the score of ISP anyway--both were clearly superior in that respect to comparable American designs for instance, both pushed the theoretical limits of each propellant type. But ker-lox is in fact theoretically superior, and the on-shelf and projected designs reflected that, with hypergol engines in the 320 range and ker-lox--exceeding 350! Compare that to an F-1 engine in vacuum, in the low 310 range.
Clearly for performance on planned, especially large, launches, Soviet ker-lox technology was the better bet. The liabilities of managing liquid oxygen were small, for a planned scheduled launch that did not require keeping a rocket ready to launch at any indefinite, random time the superpowers decided to push The Button. For the latter military mission, of course storability won the day, in one form or another, but for scheduled launches, why tempt fate for an inferior product?
The simple fact that OTL they did go on with using Proton-K and continue to use its successors even now does show that they are willing to risk it, especially with a very well known system. The Russians are frugal that way; why scrap something that works?
But I think the OTL conversion of Chelomei away from the hypergol fold shows that the apparatchiks could read the writing on the wall well enough to call a halt with the Proton. The Soviets did demonstrate the ability to launch something very big indeed with Energia, which IIRC was a project entrusted to Chelomei, and it did not use hypergols--it used ker-lox boosters designed to also serve as stand-alone small rockets, and a hydrogen-oxygen (disposable engine, and not as good ISP as Shuttle main engines or even J-2, but with a lot of thrust!) core.
Since the rules of the time-line state that unless specifically affected things play out as OTL. So that mean in ITL in the autumn of 1967 the N-1 2nd and 3rd stages will definitely get static fire tests. With the possibility of an inhabitable Venus it is likely ITL the first stage will get a static test.
What would you think the result of that test would be? In my opinion it would duplicate the failure of the first N-1 launch. And the analysis would result in the same conclusion that occurred in OTL.
I wonder why they were even doing the upper stage static firings. But I don't think it is a foregone conclusion that static firing a first stage would have revealed the problems that did take down the N-1 pad tests.
As I understand it, the belief is that the 30-engine array fell to versions of POGO--a disease that Saturn V designers were not fully aware of before American tests of that rocket--and even as late as Apollo 13, the Saturn V second stage with its five-engine array was still suffering from that. (Anti-POGO measures were taken with Apollo 14 and after, I'd guess taking advantage of the lull in launches that followed investigation of the Apollo 13 accident). Basically we are looking at resonance among the fuel lines leading to the engines, and again some people point to the extra cluster of six central engines being a culprit here. When those engines shut down as per the launch sequence, there was a hydrostatic shock through the entire propellant manifold system, believed to have done serious damage to other engines hitherto working just fine. How much of each crash was due to the onboard computer system designed to compensate for engine-out by shutting down the opposite engine was at fault is an open question too--in every case the KORD computer did wind up ordering full shutdown of all engines, but this may have been because more of them were in fact malfunctioning than was realized.
The OTL N-1 was in fact pushed to the red line in the desperate attempt to get a full 95 tons to orbit in many ways. All sorts of dubious measures to lighten the structure were taken--including omitting most of the telemetry installations!
So knowledge of exactly what happened has big holes in it, thanks to that.
Had they been willing to accept the limits of the 24 engine model, and not indulged the panicked urge to cut every corner in sight, holding out for incremental improvements as they gained experience, I suspect a static test of that 24 engine array might have gone well enough.
Or, if it failed, is that grounds to scrap the program? Maybe if they had something as good or better well in hand perhaps. But I think I've shown that the UR-700 was hardly a better realized alternative at that point, and unless it came from behind to show itself vastly superior for some reason we have no grounds to point to, a giant hypergol launcher's days were numbered in the late 60s and early 70's.
The purpose of a static test is to show up problems that one did not anticipate and the amazing thing is that the Soviets ran any significant number of any of them on an N-1 stage. It would make more sense if the N-11 program to use the upper three stages for a smaller launcher in the Proton class were revived, but I gather that was dead in 1967. (Concentration on N-1 would make it sensible to revive it though; the first stage of an N-11, a slight modification of an N-1's B Block, used only 8 of the same engines the N-1 A block would use, so testing it in that role would be useful both for a ker-lox three stage Proton class and suggestive for the big rocket too. And the whole upper three of N-1's 4 stages would be pre-tested as a unit before the first N-1 all up tests.)
So a failed static test is hardly a reason to shut down the program, if there are solutions to the failure at hand.
Then, getting to a launch pad test, probably no sooner than OTl even with the simpler engine array--but with perhaps a more robust stage--even a failure there would not imply giving up yet. OTL they went ahead with three tests, all failures, before throwing in the towel.
But here they need something to rival American heavy lift capability. Even if the Americans scrap the Saturn V (which seems less likely here) that will only be to follow up with something even more capable. Perhaps something like the Shuttle gets funded, but meanwhile we'd still want something capable of putting more than 15-20 tons up at a shot. (Indeed, Shuttle derived launchers could rival the Saturn V--in fact every STS shot that ever succeeded put up some 50 percent more into orbit than any Saturn V shot did! It's just that most of it was the Orbiter, not payload).
If the Soviets do give up on the N-1 design (which, with less of a unbroken record of failure, they would be less likely to do) they still have to buckle down and come up with something to take its place.
Now in OTL the N-1 failure occurred in 1969 well beyond the period of time the UR-700 project was shelved. ITL the catastrophic failure would in 1967 giving Cholemei a shot at reviving the UR-700 project.
The questions that Jared will have to answer are?
Is the N-1 first stage tested in a static fire in the autumn of 1967 along with the 2nd and 3rd stage static fire test.
If the first stage is tested what was the result?
If the first stage failed what would be the response of the Soviet Leadership.
These are the questions to answer. Bearing in mind that the UR-700 is not ready to go and won't be for at least as long as it might take to shake down the N-1, I don't think the answers veer in the former's favor.
You seem to be committed to the idea that there is no way any version of N-1 could ever work. Which is not unreasonable; I'm probably biased by some TLs in the past few years which assert it
could.
But if it can't work I think the best Soviet answer is to develop a more powerful ker-lox engine, something they have done OTL, along with even more ambitious things. It's right up their alley, anyway if they "cheat" with multiple combustion chambers. And why not?
Chelomei might get the nod for designing a rocket around that yet. He got Energia OTL, so why not? Mishin is probably just as OTL turning into a hopeless drunkard after all.
The key is getting Glushko onto the ker-lox, or meth-lox, or hydrogen, bandwagon.
...
Because of that the continued use of hypergolic based rockets like the Proton and the UR-700 is not set in stone. Even Hypergolics don't match the performance of H-Lox rockets.
That last sentence implies you actually think hypergols are inherently superior to ker-lox? Look again. Hypergols have certain advantages--that their fuels store well on Earth (in space there is some risk of them freezing!) and that they ignite spontaneously. These are useful things. They are a
close second to kerosene-oxygen in theoretical performance, not better--but pretty good, good enough to use when there are issues of long-term storage, or one wants a simpler, more robust engine that is therefore more reliable, as with the American Agena workhorse. I think it was easier, in the late 50s and early 60s, to push them closer to ideal performance than ker-lox in those days. And part of that was having a lot of designers hired to push them, for military applications that had ample funding of diverse firms/design bureaux.
But they aren't inherently superior in terms of performance. Kerosene and oxygen are cheaper (insofar as that matters; propellant costs are a small item in the total bill of building and launching a rocket) as Korolev argued back in Khrushchev's day.
Hydrogen-oxygen gives far better ISP than either--offset by the greater difficulty of handling the hydrogen and for that matter harnessing the inherently greater heat the superior fuel releases. Thus it is hard to get the sort of thrust one can more easily get from either hypergols or kerosene. Methane fuel would be somewhere in the middle.
I'm going to finish this now and pick up on the penultimate paragraph in a second post, because it is not haggling over technical and historic details like this post has been, but about the deeper philosophy of how a habitable Venus might change human priorities.
