The vast majority of Soviet strategic missiles until the 1980’s were liquid fueled. This includes the SS-18, the SS-19 as well as some SLBMs (!).
I know that liquid propellant has certain advantages, it is more efficient and gives more power per my understanding, but from what I know, logistics of it are very hard and challenging even with storable liquids.
The US as well as other powers who built missiles have all attempted to transition to solid fuled rockets, what kept the Soviets married to liquid propellants and how the hell were they safe to use…in a Submarine!
The Wikipedia article on liquid-propellant rockets lists several advantages, one of which may have been the critical factor keeping the Soviets “married” to storable liquids: LPEs can be tested. Solid-fuel engines require rigorous quality assurance procedures; they can’t be throttled, shut down, restarted, or re-used, so they need to trustworthy.
Solid rockets require an almost insane level of quality control in the production stage in order to deliver exactly the amount of thrust needed. An ICMB or SLBM has to travel thousands of kilometers and hit a target as accurately as possible; even a tiny variance of thrust could mean the missile’s warheads missing by tens of kilometers.
Solid rocket motors can be throttled by the use of variable geometry nozzle exit cones. No current “production” motors use this but it is possible. The solid rocket motors can be shut off - the term used is thrust termination. Linear shape charges rupture the motor casing at the same time as warhead or next stage separation and prior to full range of the missile. The propellant gases vent through the ruptures. I believe the Pershing II and one other missile had this feature.
Both solid propellants and liquid propellants are tested on a regular basis (I used to routinely gather samples for analysis. The liquids like IRFNA and UDMH from Lance missiles were evaluated for contamination products (eating the container/tank they were stored in) and any reactant products from a chemical breakdown. Both IFRNA and UDMH are some of the nastiest chemicals around - they don’t like each other or many materials either. Solid propellants with a nitrocellulose component are tested for loss of stabilizer. Perchlorate based propellants are sampled for binder deterioration and other characteristics. Small slice samples are taken or in the case of real reactant stuff :eek: just a surface swipe to keep from going face-to-face with 250,000 lb. of thrust (see Spartan 1st stage rocket motors.
I believe some first strike options were at least passed up to the JCS level in the 1960s era partially due to the US being “ahead” in getting missiles and bombers launched quickly. The plans were not seriously considered at the Presidential level if memory serves me.
This is correct-the rocket fuel would mix with seawater-and combine to form mitric acid-which would eat through the steel plates…and poison the air in the crew compartments.
I tend to think that many of the Sov’s land-based ICBMs had quality control problems as well-there were probably many accidents caused by the fueling process.
I recall a novel which had as it’s premise a Soviet defector claiming that the quality of the USSR’s missiles was so poor that the entire Soviet nuclear missile forces were essentially a collossal bluff.
Yeah, still no answer. The USSR did field solid fueled rockets and good ones such as the SS-20, SS-16 and SS-24. Why so much emphasis on liquid fueled when by the 1970’s the US was concentrating on solid fueled.
Are liquid-fueled rockets more portable? I know that the Soviets liked to mount IRBM launchers on flatbed trucks, a technology we never really bothered with. Were these liquid-fueled?
The Soviets didn’t discard military hardware as improvements came along. The older items were passed down through the hierarchy - front line forces to border guards to reserves to etc… While a transfer of nuke missiles wouldn’t happen in this manner, the mindset remainded the same.
Accuracy of US warheads also played a role. The liquid fueled missiles were not safely mobile. Solid fueled missiles of intercontinental size/range that were mobile were a more practical deterrent.
Warhead size also dramatically changed. The Soviets were well behind on miniaturization of warhead components and accuracy. They “liked” big nukes - for both pride and the ability to miss further away and still destroy a target. The technology (liquid fueled motors) existed to hoist the massive warheads into space so they stayed with it. When mobility, lift requirements, accuracy, and safety concerns dictated a change to solid fuel, they took that direction.
Minor pedantic nitpick to an otherwise accurate post: the parlance in industry is solid propellant motors, and liquid propellant engines, which reflects the relative mechanical complexity of solids versus liquids. You are correct to state that solids propellant requires both a lot of quality control and performance testing, not just in the physical configuration and integrity of the propellant grain but also in the formulation and processing of the constituents of the propellant. Even a minor processing change such as changing the grinding process of the aluminum particulate and iron oxide catalyst, or minor variations in blade-to-wall distance on the propellant mixer can make a difference in the performance of the as-cast solid even when subscale testing of propellant strands indicates nominal performance. This requires a high degree of consistency and quality control–something that the Soviet industry was never good at even though their rocket vehicle technology was often ahead of the United States, especially in the 'Fifties and 'Sixties–and an extensive test and aging surveillance program.
The United States took a lead in large solid rocket motor production primarily due to two factors; one was early serendipitous research on binders (the quasi-inert material that allows the propellant to be cast in a stable form), and the other was an early lead by the Navy on ballistic missile technology development. The navy recognized the hazards in liquid propellant engines in a ship-board environment where leakage or catastrophic launch failure not only threatened the launch facility but personnel and emphasized the need for solid propellant development. Although the Air Force deployed the first IRBM and ICBM delivery vehicles (the PGM-19 ‘Jupiter’ and PGM-17 ‘Thor’, and the SM-65 ‘Atlas’ and HGM-25A ‘Titan I’, respectively) using cryogenic liquid oxidizers, it was recognized that the time required for fueling (as the LOX can’t be stored in the missile vehicle indefinitely) was prohibitive in terms of response time. All of these vehicles did see later use as test launch and space launch vehicles, particularly Atlas which developed into the Atlas I and Atlas II family of launchers used in Project Mercury for orbital shots, and the Titan, which was used in Project Gemini and grew into the giant heavy lift Titan 23C and 34D configurations, the later of which used the Titan Solid Rocket Motor Units (SRMU) for initial thrust enhancement to increase payload capacity, and becoming the heaviest lift booster in the American inventory after retirement of the Saturn rocket family.
Although the air force did deploy three wings of the storable liquid LGM-25C ‘Titan II’ which delivered the massive 12 megaton MT) yield W53 warhead in the Mark 6 reentry vehicle (RV) as a “city buster”, developments in lighter and more compact nuclear devices and higher precision in guidance systems allowed for vehicles with much smaller throw weights, and then Secretary of Defense Robert S. McNamara directed the air force to focus on fielding solid propellant vehicles in accordance with the deterrence theory of Assured Destruction which required reliability, responsiveness, and high survivability as prerequisites for effective deterrence. The LGM-30A/B ‘Minuteman I’ carried a W-56 warhead with 1.2 MT yield , and the LGM-30F ‘Minuteman II’ started carrying the W62 in the Mark 12 RV along with post-boost guidance (for precision) and penetration aids (for survivability). The LGM-30G ‘Minuteman III’ with a larger SR73 third stage motor carried three Mark 12A RVs with either the W62 or W78 warheads with 150-350 kt yield in a three RV multiple independently-targeted reentry vehicle, and the giant LGM-118A ‘Peacekeeper’ carried up to ten W87 warheads with a >300 kt in MIRV configuration.
By comparison, the Soviet Union focused on storable liquids. The caustic nature of storable liquid propellants was less of an issue for the Soviets, who paid scant attention to environmental hazards and were, shall we say, somewhat less concerned about hazard to personnel posed by such liquids, although they had numerous problems with unintended catastrophic failure of vehicles, and in particular the massive SS-18 (R36M) ‘Satan’. The Soviets became expert at building high performance liquid engines that were robust and easily serviced, and so their development proceeded along those lines, even for submarine-based vehicles. The higher performance nature of liquids allowed for more total throw weight (the SS-18 could carry up to 30 RVs or equivalent mass decoys that were indistinguishable from real RV). Because flightpaths from the Soviet Union were also (slightly) retrograde, they needed somewhat higher performance than comparable trajectories from the United States.
A couple of other aspects that make solids somewhat more complex to handle are the fact the motors are transported “fully fueled” from the factory, so they are both heavy and a very large explosive hazard. Also, unlike a liquid engine which is mostly low pressure tankage and plumbing with just a small high pressure combustion chamber, the propellant grain and case form a giant high pressure vessel that has to resist internal pressures of 600-1500 psi in addition to resisting flight loads, so while solids are more simple in terms of mechanical complexity they have to resist higher loads with a lot more design constraints.
While varying the nozzle geometry can change the performance slightly, it can’t really be considered “throttling” the same way one can with a liquid. The burn rate is dominated by internal pressure, which depends mostly upon the initial propellant grain bulk temperature and the geometry of the chamber which changes as the grain burns. The change in exit cone geometry is most significant at high altitude where ambient pressure P[sub]a[/sub] < 0.1 psi and the gas-phase part of the plume can undergo something roughly approximating ideal gas thermodynamic expansion. (The solid particulate part of the plume doesn’t undergo any significant expansion.) At altitudes < 50 kft lengthening the exit cone makes <1% difference in performance. There are nozzles (mostly upper stage or orbital insertion motors) which do use extensible nozzle cones (which telescope out shortly after ignition) to reduce stack length while optimizing performance at altitude, but once deployed they don’t change geometry, and developing a practical cone that could dynamically change exit velocity on command would be very challenging.
Thrust termination can be used to relieve pressure in the case, but this obviously renders the motor unusable. Thrust termination is normally performed as a range safety function to prematurely terminate thrust for range destruct, although on a few vehicles (mostly ICBMs) thrust termination has been used to provide precise velocity control during stage separation or post-sep to prevent the aft stage from contacting the upper stage or payload. Thrust termination for these applications is done by linear or conical shape charges on the forward dome of the motor, which is reinforced to prevent structural failure of the rest of the case.
The use of a pure fuel grain and liquid oxidizer in a hybrid motor allows for throttling ability with a solid-like grain, but the hybrid suffers from bearing the negatives of both liquid engines (mechanical complexity, POGO and water hammer in plumbing, high inert mass fraction) and solid motors (lower performance, large pressure vessel, variability in performance with grain burnback) plus some difficulties peculiar to hybrids.
To answer the question posed by the o.p., the Soviets had a lot of problems overcoming the fundamental difficulties of solid motors, in particular those caused by poor quality control and flight control systems. The Soviets have long held an advantage in liquid engine development, to the point that the Atlas V now uses Russian-designed RD-170 and RD-180 engines. The Soviets have gotten better about developing solid vehicles and their most recent ICBMs and SLBMs have been solids, albeit not without problems. The United States, through a long-standing and cross-service development of large solid rocket motor technology (much of the technology developed in Polaris and Poseidon fed into Minuteman II and III, while a lot of Peacekeeper development fed into the Trident II D-5 SLBM, and the air force spent a lot of effort on even larger diameter segmented motors that ultimately supported the design of the Titan SRM/SRMU and the STS/Shuttle SRM/RSRMs).
The Clancy-inspired view that Soviet ICBMs were not reliable or accurate is largely a myth. While it is true that after the fall of the Soviet Union many missile wings and facilities fell into disrepair, and that Soviet IC technology has never been on part with that of the United States, in general Soviet military rockets were in general highly reliable and “accurate enough” for their mission, and posed a legitimate if numerically exaggerated threat. Several of these systems have gone on to be used as demil “surplus” hardware in commercial space launch applications with a credible degree of reliability, putting paid to the notion that they were not reliable or accurate.
What is true is that while Khrushchev bragged that Soviet factories were producing missiles “like sausages”, the Soviets were fielding diminutive wings of cryogenic propellant missiles that took hours to fuel and ready for launch just as the United States was at the brink of deploying the somewhat more responsive Titan I and was within only a few years of mass deployment of the storable Titan II and solid propellant Polaris and Minuteman systems. Again, it was the lack of Soviet industry and problems with quality control rather than a fundamental lack of technology which held back the Soviets.
While the US developed only a small handful of systems and was often restricted by public opinion on basing options and number, during the 'Sixties and 'Seventies the Soviets developed dozens of different systems–mostly liquid propellant based–to an operating concept level and fielded several of each class of missile, including the aforementioned SS-18 which had nothing comparable in the US arsenal and which could easily overwhelm any ABM system deployed (Safeguard, GMD) or feasibly conceived (CHECMATE, Brilliant Pebbles, ERIS). Although the Soviets ultimately achieved numerical superiority (albeit more than two decades of after Kennedy rode to the White House touting fears of a “missile gap”) by that point the responsiveness of missile and early warning systems, the redundancy and accuracy of the counterforce SLBM fleet, and the general level of overkill (ability to hit vital targets with multiple strikes) made the numerical superiority nearly irrelevant save for politics.
The Soviets developed mobile transporter-erector-launcher capability for many systems, including several classes of IRBM and two classes of ICBM (one road mobile, one rail). The United States also had mobile IRBMs–the MGM-31 Pershing family, which replaced the non-mobile PGM-11 Redstone–but in general didn’t have a lot of need for mobile missiles as the Minuteman was stored in hardened underground silos that had good survivability against near-miss ground impact or high altitude air burst, and were located far enough from Soviet threats (either land or sea based missiles) that a disarming first strike was an unlikely possibility.
The lack of mobility became a big problem in perception during Peacekeeper development as some parties–largely in an attempt to halt development and deployment of the system–argued that plans for ground basing, particularly the “dense pack” scheme originally proposed, would render the system vulnerable. An original concession had the first (50) Peacekeepers deployed to modified Minuteman II silos while the second half would be deployed from bunkers onto special purpose rail cars under the Rail Garrison program. Rail Garrison was eventually determined to be futile and was replaced by the LGM-134 Small ICBM ‘Midgetman’ program to build a road-mobile single warhead missile employing many of the same technologies and manufacturing processes successfully developed for Peacekeeper. Midgetman ran into some technical hurdles as well as the end of the Cold War, and was cancelled after only a couple of development flight tests.
I could be wrong, but that is not counted as part of the 134. There was nothing that said there were no failures in the beginning. They just said they had 134 work in a row.
Yes, that was the first operational test flight, when they found out that water hammer of the launch eject system of the D-5 was different than C-4. Still, the navy always talks in terms of “anomalies”, never “failures”. I find it unlikely that they’ve managed 134 launches without any significant anomalies/failures/problems of any kind, as that would make it about four or five times more reliable than any other rocket launch system in existence.
Why are problems/failures so common in rocket launches?
The military launches rockets all the time, be they anti-tank, anti-aircraft or artillery rockets. Is there something in that kind of rocket launch that makes it so unreliable?
As always Strangeranswers all the question I had asked as well as many I had not. Good show!
A follow up, the dangers of ship borne liquid fueled rockets, I am certain the Soviets did eventually solve the problem, indeed IIRC I read that in one of their Delta class subs they had special equipment to cater to just that.
