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Found 10 results

  1. RD-0410

    Also posted here. RD-0410 The history of American efforts to develop nuclear thermal rockets is relatively well known. Similar Soviet efforts have remained far more obscure. However, during the Cold War, the Soviet Union developed and tested an advanced nuclear thermal rocket engine, designated the RD-0410. Unfortunately, relatively little English-language information about the RD-0410 can be found (at least in easily available sources). Similar to the American NERVA program, development of Soviet nuclear rocketry began in the mid-1950s. Serious research began in 1955, with development of a rocket beginning in 1956 (the people working on this project included such notable people as Kurchatov, Keldysh, and Korolev). Initially, the Soviets planned to use the nuclear rocket to power an intercontinental ballistic missile, or possible a cruise missile. However, it was quickly realized that chemical rockets were good enough for suborbital flights. As a result, by the 1960s, it was decided to develop the engine for usage in space. The engine was developed by the KBKHA bureau, which had also developed engines such as the RD-0105 (used on some derivatives of the R-7). The goal was to develop an engine with a specific impulse of roughly 800-900 seconds, double what can be achieved with normal chemical rockets. Doing this would require creating a nuclear reactor that was both very light, and capable of withstanding very high temperatures around 3000 Kelvin. I have seen a few references to a program to develop a 2,000 isp engine, but this would require temperatures (over 15,000K) well in excess of what was possible in the 1950s (or even today) for a solid core design. The test site selected for the Soviet nuclear engine was Semipalatinsk in Kazakhstan, a remote location similar to Jackass Flats in Nevada. The Soviets had already tested numerous atomic weapons (including their first in 1949 there), so the place was no stranger to nuclear activity. It appears that tests of the engine were conducted in a mine shaft approximately 150 meters deep, unlike the American NERVA, which was tested aboveground. Most likely, this was due to concerns over radiation should the engine malfunction. At some point, the engine acquired the designation RD-0410, it is less commonly known by its GRAU designation 11B91. That the engine received a GRAU designation means that it was almost certainly considered for military applications. The American NERVA had a thrust of approximately 330 kilonewtons. This was much more than the RD-0410, which had about 35 kilonewtons. This was both by design, and due to political/monetary considerations. The Soviet government had somewhat lost interest in the project once it had become apparent that the nuclear engine was not usable as an ICBM upper stage. More importantly, by developing a lower power engine, the reactor assembly as a whole would be smaller. The RD-0410, including propellant, was planned to mass roughly 15 tons when completed; putting it well within the payload capabilities of Soviet launchers like Proton. The actual engine itself weighed only about two tons. In contrast, the American NERVA was much heavier, and could only be launched by a Saturn V or similar vehicle. There were other important differences between NERVA and RD-0410. The NERVA’s fuel elements were hexagonal in cross section, with several holes drilled in them for hydrogen to pass through. Hundreds of these elements (each about an inch wide) made up the NERVA’s reactor. NERVA Fuel Elements It has been difficult to find exact information about the geometry of the RD-0410’s fuel rods, however, it appears that they had a complex shape. The fuel rods were twisted, and had a complex cross section, shaped like the petals of a flower. This was intended to lock the fuel rods together, and prevent fuel from falling out of the reactor if a few rods cracked or became dislodged. The fuel elements were made of uranium carbide, in order to better withstand the high temperatures of the core. Development and testing of the RD-0410 proceeded slowly. By 1973, America’s NERVA had already been test fired, then cancelled before actually flying. However, large scale tests of the RD-0410’s components did not begin until 1978. The test reactor was first started on March 27, 1978, and ran for 70 seconds. Gradually, the reactor was run for longer, and at higher temperatures. By 1981, the RD-0410 was running for an hour, its design duration. A specific impulse of 910 seconds was achieved; this was superior to that which was obtained with NERVA. The American Timberwind/SNTP project from the late 1980s planned to achieve similar efficiency with much higher thrust to weight, but it encountered numerous technical problems and did not reach the test stage. All accounts of the RD-0410 state that it’s testing at Semipalatinsk went very well. Originally, it was planned that the engine would fly in 1985 (likely replacing the Block D 4th stage on Proton). However, as the Soviet Union imploded during the 1980s, development slowed, then halted. Other Soviet nuclear rockets were planned, such as the RD-0411; a high thrust (~400 kN) engine that would have been used on a Mars mission, and an engine designated 11B97, which would have had the capability of either nuclear thermal or electric propulsion. However, like all other nuclear rocket programs, none of them came to be. via Astronautix, a concept for a Soviet Mars spacecraft, that likely would have used RD-0411 Important Stats: Unfueled Mass: ~2,000 kg Total Stage Mass ~14,000 kg Thrust: 35 kN ISP: 910 sec Maximum Run Time: 3600s Height: 3.50m Diameter: 1.6m Bibliography: http://www.astronautix.com/engines/rd0410.htm http://www.popmech.ru/made-in-russia/5983-k-marsu-na-reaktore-vzryvnaya-sila/ http://www.cosmoworld.ru/spaceencyclopedia/programs/index.shtml?yard.html
  2. This thread will be about Soviet cars, racing vehicles and SRS BSNS cars. More photos, less text! Moskvich 404, 1954. Moskvich 407 Coupe Moskvich-G1, 1955 Moskvich-G2, 1956 Another Moskvich-G2 Moskvich-G3, 1961 Moskvich-G4, 1963 Moskvich-G4A, 1965 Moskvich-G5, 1968 Moskvich-G5M, 1974
  3. Basic History State of PVO before MiG-25 During the middle part of the 1950s, the PVO (Soviet air defense forces) were poorly equipped to deal with future threats. The majority of its interceptors consisted of aircraft such as the MiG-15, MiG-17, MiG-19, and Yak-25. These aircraft possessed sufficient performance to take on American bombers such as the B-29 and B-50, and were at least marginally capable of intercepting jets like the B-47 or B-52. However, they were horribly inadequate against coming bombers, such as the B-58 Hustler (which first flew in 1956). The arrival of Mach 2 capable interceptors such as the Su-9, and later the MiG-21 in the latter portion of the 1950s evened the playing field somewhat. However, these interceptors suffered from severe deficiencies. The Su-9 (and to a lesser extent the MiG-21) had a cripplingly short range, a major shortcoming when defending a country as large as the Soviet Union. The Yak-27, a development of the Yak-25, had better range than either of the deltas, but was inferior in terms of speed and altitude. In addition to various performance issues, the PVO’s interceptors were also handicapped by poor armaments. The Kaliningrad K-5 (NATO AA-1) radar guided missile was equipped by most PVO interceptors following its introduction in 1955. Though decent for its time, it was limited by its beam riding guidance and short range. The infrared guided K-13 (AA-2) was introduced in 1960 after being hurried copied from a captured AIM-9B. Like the K-5, the K-13 suffered from poor range, and was also limited to being fired at the rear of a target. These systems would clearly not be sufficient to reliably destroy the B-58, let alone the Mach 3 capable XB-70 (which began development in the late 1950s). The introduction of surface to air missiles such as the S-25 and S-75 had some promise (as demonstrated by the destruction of a U-2 reconnaissance aircraft by an S-75 on May 1 1960 at over 18,000 meters). However, these missiles required large fixed launch sites, leaving them incapable of covering large swaths of territory. In an environment where a single bomber was capable of destroying a whole city, the situation was clearly unacceptable. It was clear that a new interceptor was needed to equip the PVO. Numerous solutions were tried. A modified variant of the MiG-19, the MiG-19SU was tested. This aircraft was fitted with liquid rocket engines in addition to the two RD-9s, giving (briefly) improved speed and altitude capability. This allowed flights to over 20,000 meters , however, the aircraft suffered severe controllability issues. In any case, it was clearly a temporarily solution. Another program was the development of various ‘heavy interceptors’, capable of engaging NATO bombers at extreme range, well away from populated areas or strategic targets. These included the abortive La-250, and more successful Tu-128 (developed from the Tu-98 bomber prototype). Though the Tu-128 entered service (indeed, it continued on into the early 1990s), it did not arrive until the middle of the 1960s. Even then, it was a large and ponderous aircraft, capable only of transonic speeds and completely lacking maneuverability. It could not serve as the PVO’s primary interceptor. An effort with more potential was the Sukhoi T-37. This aircraft was broadly similar in planform to the Su-9 (being a tailed delta) but was much larger. Powered by an R-15-300 engine, it was planned to reach speeds near 3,000 km/h at altitudes approaching 25,000 meters. Interestingly, it was also to have been fitted with equipment enabling it to be flown automatically under ground control (the US had the SemiAutomatic Ground Environment, a similar system capable of directing F-106s). However, it was plagued by numerous issues, and was scrapped in 1960 before it ever flew. Requirements The requirements for the MiG-25 were greatly determined by its potential adversaries. The main threat was the B-58 Hustler, capable of Mach 2 at altitudes approaching 18,000 meters. In 1960, the Soviets became aware of yet another threat; a Mach 3 successor to the U-2 was under development (this was the A-12/SR-71, though the Soviets did not know this initially). As a result, it was decided that the new interceptor should be capable of flight at up to Mach 3, and at altitudes in excess of 20,000 meters. Coincidentally, the VVS (Soviet Air Force, separate from air defense forces) was looking for a new high speed reconnaissance aircraft during the late 1950s. At the time, most of the VVS reconnaissance force consisted of variants of the Il-28 or Yak-25. The survivability of these aircraft against new NATO fighters such as the F-104 or Lightning was marginal at best. The Yak-25RV was in development, and promised comparable performance to the U-2 (it did not fully deliver), but this was an incremental step at best. A wholly new aircraft with exceptional performance was needed. By 1960, it was realized that the new recon aircraft had broadly similar requirements to the new PVO interceptor program (by then in development for over a year), so the programs were merged. The ability to carry photorecon equipment was added as a requirement to the interceptor program. Development The Ye-150/152 can be considered the direct ancestor of the MiG-25. Developed in the late 1950s and first flying in 1960, the Ye-150 was broadly similar in appearance to the MiG-21, but was significantly larger and was capable of reaching much higher speeds. The Ye-152 was a further development; it was fitted with R-15-300 engines, the same R-15s which would be fitted to the MiG-25. Like the Ye-150, it represented a massive performance leap over the MiG-21, but it was very much a testbed. The R-15s were supremely unreliable (early models had an average engine lifetime of roughly 20 hours), and the weapons system was tempermental. There was also the Ye-152A, which was fitted with two R-11 turbojets (the same engine as the MiG-21) instead of a single R-15. Though these aircraft did not enter production, they provided the Mikoyan-Gurevich design bureau with valuable data on high speed flight and the R-15 engine. There is some uncertainty about the initial genesis of the MiG-25 program. There are rumors that Mikoyan instructed chief designed Seletisky to develop an interceptor similar to the North American A-5 Vigilante (which had first flow in late 1958) powered by two R-15-300s. Other sources state that work began before the first flight of the A-5. While there are obvious similarities in layout between the A-5 and MiG-25, there are also massive differences. At most, the MiG-25 was somewhat inspired by the A-5, and is very much not a ‘clone’ or reverse engineered copy. (Later proposed Vigilante derivatives such as the NR-349 or rumored J58 powered version would have been much more analogous to the MiG-25). The new aircraft was assigned the designation Ye-155 by Mikoyan (the prefix Ye for yedinitsa denoting a prototype or testbed aircraft). It was decided very early to use the R-15-300 engine. However, there remained uncertainty as to the layout of the engines. Though a conventional side by side layout was ultimately chosen, a vertically stacked layout (such as on the English Electric Lightning) was also considered, as was a staggered engine arrangement (as on the I-320 prototype). Unlike previous Mikoyan-Gurevich designs, it was decided not to utilize a nose mounted intake, but instead place the intakes under the wings. This allowed for a smaller fuselage (in both length and cross section). The underwing intake placement worked well with the shoulder mounted wing placement, which was needed to allow for the carriage of very large AAMs. This wing layout also allowed the wings to be constructed in one piece, simplifying constructing and improving structural rigidity. Numerous planforms were proposed for the wing before the design of the prototype was finalized. At one point variable geometry designs were considered (this would have significantly predated the introduction of the Su-17, though variable sweep designs had been studied at least since 1945). The variable sweep design was seriously considered enough that a model of a recon MiG-25 with variable geometry was made, it somewhat resembles an F-14. One of the benefits of the variable geometry design would have been improved takeoff and landing performance, however, it was decided that this was not worth the added complexity and weight associated with such a design. Following numerous wind tunnel tests, a trapezoidal wing of low aspect ratio was chosen. As with many Soviet designs in the 1950s and 1960s, lift jets were considered for use to improve takeoff and landing distance. The proposed STOL design would have used two small RD36-35 lift engines, mounted in a slightly staggered arrangement in the fuselage, with intakes along the back of the aircraft. While the lift jets would likely have improved takeoff and landing distances greatly, they also decreased the internal volume available for fuel. This was a serious drawback, especially for the reconnaissance version. As a result, the lift jets were discarded, with the STOL design not progressing beyond the model stage. As the MiG-25’s design grew closer to being finalized, materials selection became a serious issue. The leading edges of the wings, inlets, and nose of the aircraft would experience extremely high temperatures at Mach 3, well above the melting point of conventional aluminum alloys commonly used in aircraft construction. Alternative materials had to be found, and many were considered. At first, titanium seemed a logical choice. It has excellent thermal properties, is quite strong for its weight, and the Soviet Union possessed large reserves of the material. However, the Soviet aircraft industry had little experience working with titanium, which was notoriously temperamental (for instance, when manufacturing the SR-71, Lockheed engineers were forced to use special tools, as normal tools contained cadmium, which made the titanium brittle). In particular, the automated welding methods commonly used in Soviet aircraft manufacturing plants would not be suitable for titanium. As a result, it was decided to use steel alloys for the majority of the MiG-25s structure (titanium was used in some areas, but at much lower quantities). Initially, there were some doubts as to whether certain components (such as the integrated fuel tanks) could be made strong enough without seriously increasing weight, or absorbing the cyclical flight loads. Tests showed that this was not the case, and the MiG-25 ended up being built using large quantities. In addition to the issues with materials selection for the aircraft structure, the thermal loads associated with high speed flight caused trouble in other areas. Normal lubricants and hydraulic fluid would break down at the temperatures the MiG-25 would experience, and normal canopy glass would melt. In many ways, this mirrors the problems faced by the Skunk Works team designing the A-12 at around the same time. Throughout 1962 and 1963, the design of the MiG-25 was further refined. In 1963, construction began on the first prototype, Ye-155R1. Its completion took most of the year, and it was not rolled out from the Zenit Machinery Works (the common name for the MiG bureau’s experimental aircraft factory) until December. Despite this, Ye-155R-1, a prototype of the reconnaissance variant, was missing much of its operational equipment. Still, it had more than enough to validate the basic flight characteristics of the airframe. In addition to lacking various pieces of equipment, Ye-155R-1 differed from production MiG-25s in several ways. For one, the aircraft had a pair of 600 liter fuel tanks mounted at the wingtips. These both increased fuel capacity, and prevented flutter. Ventral fins were attached to the fuel tanks, to improve lateral stability at high speeds. Both of these features would be absent from production MiG-25s. Ye-155R-1 also had provisions for the fitment of canards to the sides of the forward portion of the air intakes; these would have been used for pitch control at high Mach numbers, but they were never installed. The first prototype suffered from numerous issues. Among the most serious of these was roll control issues in the transonic regime, in some cases severe enough to render the aircraft uncontrollable. The wingtip fuel tanks caused vibration as fuel was depleted and sloshed about. The intakes were inefficient at high Mach numbers, and the aircraft’s static margin decreased as well. Finally, Ye-155R-1 was overweight, causing its range to fall short of the target. The second prototype, Ye-155R-2, was also a prototype of the recon MiG-25. This aircraft was broadly similar to the previous prototype, though it did incorporate some refinements. There was one immediately obvious difference; the wingtip fuel tanks were deleted. This would be the last prototype built at the Zenit plant; the factory was tasked with producing the first MiG-23 prototypes, and had no more room for further Ye-155s. As a result, it was decided to build prototypes from Ye-155R-3 onward at Mikoyan’s Gorkii plant, the same as would produce the production aircraft. This resulted in a delay in producing Ye-155R-3 as the factory was retooled, but it would ultimately allow production to commence quicker. Ye-155R-3 was a milestone in and of itself; it was fitted with a full suite of photorecon equipment, and would be used for testing various camera arrangements (among other things). Belenko Defection Later Variants Post-Soviet service Variants Prototypes Ye-155 models Operational MiG-25P/PD/PDS Export MiG-25P MiG-25RB MiG-25R MiG-25BM MiG-25PU Other Ye-266M Ye-155MP Buran testbeds / training aircraft Various other concepts and variants Production In Red Air Force Service Other Operators Combat Performance Egypt vs. Israel Iraq MiG-25 vs. SR-71 Structure Materials Engines Electronics Radar Early versions vs. Later Recon variants - cameras Armaments Air to Air MiG-25P MiG-25PD Ground MiG-25RB MiG-25BM Other Systems of Note Citations http://www.kamov.net/russian-aircraft/mig-19su/ http://www.kamov.net/russian-aircraft/sukhoi-t-37/ MiG-25 'Foxbat', MiG-31 'Foxhound': Russia's defensive front line By: Gordon, Yefim. Aerofax 1997 Skunk Works: a personal memoir of my years at Lockheed By: Rich, Ben R., and Leo Janos. Little, Brown 1994
  4. Information Wanted: Project 701

    While doing research on the MiG-25, I came across a couple mentions of something called Project 701. Supposedly, it was a planned replacement for the MiG-31, and was being developed during the late 80s (but never was built). I've seen a couple different conceptual designs posted, of which this one seems the most plausible; Although the planform is more than a bit odd for a design that was supposedly to have had low observability features (also, dorsal intakes on a fighter is wrong to me on a visceral level). If anybody has any more information on this, please post it here.
  5. The Yakovlev VTOL Family

    During the latter part of the Cold War, the Yakovlev design bureau came up with quite a few designs for VTOL combat aircraft. While they weren't the most successful designs, they are pretty interesting, from both a historical and technical standpoint. The first of these is the Yak-36 (Freehand); While the Soviets had come up with numerous other VTOL designs in the 1960s, most of them used dedicated vertically mounted engines to take off vertically. However, the Yak-36 had a more modern arrangement, with two engines that used vectored thrust for both vertical and horizontal flight. The Yak-36 was powered by a pair of R27-300 jet engines (the same engines that powered the MiG-23 'Faithless' VTOL concept). In addition to providing vertical and horizontal thurst, the engines also provided airflow for 'puffers' at the wingtips, nose, and tail, which provided control in hover and low speeds (where aerodynamic controls would not be effective). The Yak-36 suffered from various difficulties during its development, among them the engines reingesting exhaust gases. At least two of the prototypes crashed at somepoint. Though the Yak-36 was at various points displayed with underwing armaments (such as rocket pods), it was never deployed to operational units; it was solely used as a testbed. Following the Yak-36 was the more widely known Yak-38 (Forger). It entered service in the early 1980s. Unlike the Yak-36, the Yak-38 was fitted with lift jets (two RD-36V engines). Though these engines did an adequate job of providing vertical lift, they had the drawback of being dead weight in horizontal flight. Horizontal thrust was provided by a single R27-300. Though the Yak-38 was capable of VTOL, it had highly limited performance; it was strictly subsonic, and had marginal payload capability. (pictured: unrestrained optimism) The Yak-38 was designed from the outset as a combat aircraft, intended to be deployed from the Soviets' Kiev class carriers. In this role, it was shit (much like your favorite anime). The first issue was reliability; many of the Forger's components proved to be horrendously unreliable, especially the lift jets. I've seen figures stating that the lift jets had an average lifetime of less than 25 hours, which leads me to suspect they were actually rebranded Jumo 004s. Engine failures were especially bad in the Yak-38 - a failure of a lift jet on one side would lead to the jet entering a fast, unrecoverable roll. The lift jets also had poor thrust in hot conditions; in many cases, the Yak-38 had to fly with only two pylons filled, rather than all four. Considering that the Yak-38 had no internal armament, this was not optimal. Interestingly, in addition to using it as a carrier aircraft, the Soviets also trialed the Yak-38 as a close air support in Afghanistan. This was less than successful; the Yak-38 was only capable of carrying a pair of 100kg bombs, markedly inferior to dedicated CAS aircraft such as the Su-25. Rumors of the Yak-38 being deployed to Colorado are false; Numerous variants of the Yak-38 were developed, most notably the Yak-38M, which despite having improved engines and other components, was still a dog. There was also the Yak-38U, a serious contender for the title of 'Ugliest Airplane'. In the late 1970s, development of a successor to the Yak-38 began. This aircraft was the Yak-41 (Freestyle). The general configuration of the Yak-41 was similar to the Yak-38, with a pair of lift jets in the fuselage and a single main engine for thrust. However, its capabilities were massively improved. While the Yak-38 was a strictly subsonic aircraft, the Yak-41 was capable of supersonic flight, setting many records for VTOL aircraft (under the fictional designation Yak-141). Additionally, it incorporated far more advanced materials in its structure (including large scale use of composites), as well as improved avionics (such as a radar set which was actually useful). Its payload capacity, in terms of weight, was roughly the same as what the Yak-38 could (theoretically) carry. However, given that the Yak-41 was a dedicated air superiority craft, this was less of a concern than the Yak-38s payload deficiency in the strike role. Unfortunately for the Yak-41, it began testing in the late 1980s, just as the Soviet Union was falling apart. Though some testing continued through the early 90s, the Yak-41 never entered operational service. The second nail in the Yak-41s coffin was the Soviet Union / Russian Federation's acquisition of larger aircraft carrier(s), capable of operating aircraft such as the Su-27K and MiG-29K. Interestingly, for a few years in the early 1990s, Yakovlev collaborated with Lockheed Martin on the development of the Yak-41. This has given rise to many conspiracies about the F-35B being a clone of the Yak-41. While this is obviously false, it wouldn't be outside the realm of possibility that a few bits on the JSF might have drawn inspiration from Yak's design in some way. There was one final successor to the Yak-41; the Yak-43. An even more advanced evolution, the Yak-43 could have been quite capable (had it been built). From what I can find, it dispensed with the extraneous lift jets. Power would have been provided by a modified NK-32 turbofan, the same engine that powers the Tu-160. This would have given the Yak-43 significantly improved performance and payload capacity compared to its predecessors. Additionally, the Yak-43 would have incorporated low observability features into its design, bringing it closer to being a true competitor to aircraft such as the F-35B. In any case, the aircraft remained unbuilt, and I have not heard of any efforts to revive the design.
  6. Yakovlev MFI submission

    I found this interesting picture of the Yakovlev MFI design: Obviously, it was never built. The MiG submission was the 1.44 and the Sukhoi submission was the SU-47.
  7. On another website, i was recently provided with a link to this paper on Soviet mountain tactics and doctrine. I have not yet finished reading it, but it appears that it could be of interest to some here.
  8. Requires knowledge of Russian language and/or google translate. http://scilib.narod.ru/fleet.html
  9. Project 705

    The USSR's Project 705 class submarines incorporated many technological advances for their time. For instance, operation of the submarine was intended to be highly automated, reducing the total crew by a large amount. Additionally, it used large amounts of titanium in the hull, and a liquid metal cooled reactor, meaning that it could dive to much deeper depths and travel at higher speeds. In theory, the 705s should have been superior to any US Navy submarine design. However, they suffered from maintainence issues, were expensive to operate, and were exceptionally noisy, even compared to contemporary Soviet submarines. (via wikiped) I'm not very knowledgeable about naval matters, so I'm curious as to whether the 705's failings were the result of an inherently flawed concept behind their design, or because the Soviets at the time did not have the knowledge/technology to implement it properly.
  10. UR-700: Father of Proton

    During the 1960s, there were many competiting designs for the rocket that would be used in the Soviet Lunar Program. Ultimately, the N1 was chosen, and proceeded to detonate and/or deflagrate vigorously on all four of its launches. One of the hypothetical competitors to the N1 was the UR-700. A development of Chelomei's 'Universal Rocket System' (which also included the UR-100, UR-200, and UR-500 (Proton)), there were several important differences between the UR-700 and N1. For one, while the N1 was to have used kerosene/LOX fuels, the UR-700 would have used hypergolics, namely UDMH/N2O4. This fuel combination has reduced specific impulse compared to cryogenic fuels. However, considering that Chelomei's other rockets in the series were developed as ICBMs fueled by hypergolics, it is easy to see why they would have been chosen for the UR-700. Additionally, while the N1 had no less than 30 first stage engines, the UR-700 first stage was to have been powered by only nine RD-270 engines. To be fair, the RD-270 was much larger than the NK-15 used on the N1. The UR-700 was planned to put 130-170 tons into LEO, which the Soviets judged to be the required amount for a direct ascent lunar mission. The choice of direct ascent, as compared to the lunar orbit rendezvous approach used by the Apollo missions (as well as Korolev's N1 based mission profile) results in a less efficient architecture. Most likely, Chelomei chose a direct ascent approach due to fears over the Soviet's lack of docking. Since the Americans had worked these issues out during the Gemini program, by the late 1960s, they were confident in the decision to use LOR. Given the numerous issues in the Soviet Lunar Program, it is unlikely that choosing the UR-700 over the N1 would have got a cosmonaut on the moon before Armstrong. However, it's an interesting what-if? Could the UR-700 have been modified for use in an LOR mission? I believe it could have, given the UR-series' modular nature. Of course, it is likely that the UR-700 would have run into many other unforeseen issues, which could have resulted in failure. I'm curious to see y'all's opinions on it.