N1: The Rise and Fall of the USSR's Moon Rocket
- Aeryn Avilla
- Feb 21, 2020
- 13 min read
Updated: Mar 20
Author's note: The original 2020 post was heavily edited in 2023.
The N1, or Raketa-nositel "rocket-carrier", was a Soviet heavy-lift launch vehicle intended to send Soviet cosmonauts to the moon in the late 1960s and early 70s. The L3 complex was the four-component system designed to fly and land cosmonauts on the moon. This post will not discuss the L3 in detail and is meant to be an introduction to the N1 program, despite its read time being longer than most other posts on this blog.
The first studies on what would be the N-series of rockets began near the end of 1959 by Chief Designer Sergei Korolev and consisted of three rockets: The N1 was the largest and would be used for military space stations and crewed deep space missions; the N2 was a smaller intercontinental ballistic missile (ICBM); and the N3 would be the replacement for Korolev's R-7 rocket, the world's first ICBM and the baseplate for the Vostok, Voskhod, and Soyuz launch vehicles. It was the competitor to the Chelomei Design Bureau's Universal Rocket series and the Yuzhnoye (then Yangel) Design Bureau's R-36. The UR-100 was selected as the new "light" ICBM and the R-36 as the new "heavy" rocket, negating the need for the development of the N2 and N3.
In 1961, when word reached Moscow that US President John F. Kennedy announced the goal of landing a man on the moon (and returning him safely to the Earth) by the end of the decade, Korolev was given funding to start N1 development by the end of 1963 with testing by 1965. At the time, the Soyuz spacecraft was being developed as well, and Korolev proposed using it to send crews to the moon using the Earth Orbit Rendezvous (EOR) profile. In short, EOR uses several individual launches of spacecraft and equipment assembling in Earth orbit before flying to the moon. However, this profile requires more time and resources than Lunar Orbit Rendezvous. so Korolev suggested using the much larger N1 rocket to launch the future lunar Soyuz [1]. It is important to note that the Chelomei Design Bureau was also proposing a series of circumlunar missions to beat the US to the moon, and although this post does not focus on the competition between it and the Korolev Design Bureau, we should keep in mind history might have been very different if Chelomei's rockets had been approved and successful.
The N1 stood 344 feet (105 m) tall, making it the second-tallest rocket built to date (the Saturn V was 363 feet, or 110.6 m, tall) [2]. The N1-L3 consisted of five stages, the first three for use in low Earth orbit and the second two (which made up the L3 portion) for translunar injection and lunar orbit insertion. The lower stages formed a conical shape due to the size and arrangement of the fuel tanks, and the base of the vehicle was 56 feet wide (17 m). It would have had a payload capacity of about 210,000 pounds (95 metric tons) to low Earth orbit. The Saturn V, by comparison, had a payload capacity of 310,000 pounds (140,000 kg or 140.6 metric tons) to LEO.
The N1's first stage, Block A, was the most powerful rocket stage ever fired at the time, though it failed during all four launches of the vehicle due to lack of prior static test firing. It produced over 10 millions pounds of thrust (4620 metric tons), exceeding the Saturn V S-IC's 7.5 million pounds of thrust (3402 metric tons). It is one of only two flown Nova class first stages, the other being SpaceX's Super Heavy rocket, which produces 16.7 million pounds of thrust (7575 metric tons) [3]. The Block A had a total of thirty NK-15 engines, and despite their multitude of failures, were the first staged combustion cycle engines, in which the propellant is combusted in stages rather than all at once.
The second stage, Block B, consisted of eight NK-15V engines in a single ring. The "V" engine only differed in tuning. The third stage, Block V, consisted of four small NK-21 engines arranged in a square. It could function with three of the four engines working. The first three stages used liquid oxygen and kerosene. At the very top of the stack was the L3, which consisted of the Block G upper stage, Block D upper stage, LK (lunar lander), and LOK (lunar orbital spacecraft).
There were a total of ten N1's built, though not all flew nor were complete. 1L and 2L were used for testing. 3L, 5L, 6L, and 7L launched and failed shortly after, some resulting in launch pad destruction. 4L's Block A liquid oxygen tank developed cracks and never launched, so parts were used for other launches or scrapped. 8L and 9L were flight ready but were scrapped when the program was cancelled, and 10L was never completed at all. They each launched from Site 110's right pad at the Baikonur Cosmodrome in Kazakhstan [4].
When the first flight-worthy N1, the 3L, was transported from the assembly building to the launch pad in May of 1968, a bottle of champagne was smashed over its transporter erector in accordance with ship-building tradition. American reconnaissance satellites took photos of this vehicle on the pad on August 11, and a certain three-letter agency determined it might be crewed. This would convince NASA move up the launch of its first manned lunar mission, but more on that later.
The first in a string of failures, the launch of 3L took place on February 21, 1969. Its objective was to insert a prototype of the L3 carrying cameras for surface photography into lunar orbit. However, most in the N1 program had little faith in vehicle. TsNIIMash (or Central Research Institute for Machine Building), the brain of the Soviet space industry, used a detailed failure record of thirty missiles and space launch vehicles to predict the reliability of the N1 L3. The probability of mission success was an astounding 16%. Providing this figure to the Kremlin would be political suicide, so Yuri Mozzhorin, the head of TsNIIMash, revised the method used to come to this conclusion. It now had a 67% chance of being successful. Nikolai Pilyugin, the head of the flight control system development, suggested not relying on historical record to determine the probability of success for the mission, and his associates agreed.
On the morning of February 21, everyone at the assembly area at Site 112 and the residential area just south of the launch pad evacuated (this was the standard for each N1 launch). It took 12 seconds for the Block A's 30 engines to generate the thrust necessary to lift the massive rocket off the ground. A few seconds after liftoff, a voltage caused the KORD, (Russian acronym for the English "Control (of) Rocket Engines"), the N1's engine control system, to shut down engine 12 and engine 24. At T+6 seconds, pogo oscillation in engine 2 triggered a propellant leak, causing the highly combustable fuel to spill into the aft section of the booster, which in turn caused a fire. At T+69 seconds, the KORD shut down the entire first stage and "locked" the Block B and Block V engines to require manual input of commands for engine fire. The vehicle reached an altitude of 8.7 miles (14 km) before falling back to Earth and crashing into the ground at T+138 seconds. The cause of this failure was later determined to be a rupture in the propellant feed line. However, even if this mission was a complete success, a manned lunar flight was still multiple years away.
The second N1 launch, 5L, included a dummy 7K-L1A spacecraft with a fully operational Block G, Block D, and emergency escape system. It was intended for a circumlunar flight and photography of possible manned landing sites. The vehicle was transported to its launch pad in May or June, where a full-scale mockup called 1M1 ("m" for "maket", meaning "dummy") was fully erected on the left pad for integrated testing.
The midnight July 3, 1969 launch had a massive local audience. Ignition and liftoff were nominal, but at T+10.5 seconds, at an altitude of around 330 feet (around 100 m), pieces of the Block A's tail section began to fall off. Every NK-15 engine except engine 18 immediately shut down and according to eyewitness reports, the rocket appeared to freeze in mid-air before tilting to the side at a 45° angle and falling out of the sky. Almost instantaneously, the emergency escape system's rockets fired and carried the L3 payload into the night sky. The 344-foot tall (105 m) vehicle collapsed back onto its launch pad, most of its propellant still in its fuel tanks. These two-thousand tons of propellant triggered a shock wave that shattered windows as far as 25 miles away (40 km) and sent debris flying across Bainokur. Some pieces of the vehicle were found as far away as 6 miles (10 km) from the pad, including an 880-pound (400 kg) gas reservoir that landed on the roof of an assembly building. Miraculously, there were no human casualties but dead birds and small animals littered the plains as droplets of unburned kerosene drizzled from the heavens. A mere 23 seconds had passed from takeoff to total destruction of both the rocket and the launch pad. It was later determined the KORD caused engine shutdown and the thrust of the single engine 18 on one side of the vehicle caused it to tilt before losing altitude.
As a huge mushroom cloud turned night into day, Lt. Colonel Semen Komarovsky recalled, "Today...I saw without exaggeration the end of the world, and not in a nightmare but while fully awake standing right next to it."a Two weeks later, American astronauts Neil Armstrong and Buzz Aldrin became the first human beings to land on lunar surface. The moon race was over.
Or was it? In September of 1970, NASA terminated the Apollo program, though it would not officially end until the conclusion of Apollo 17 in December of 1972. This announcement could have given the Soviet Union motivation to pursue a more advanced and more sustained exploration of the moon.
The next launch, N1 6L, occurred almost two years after the previous. Soon after liftoff around 2:00 AM Moscow time on June 26, 1971, the rocket experienced an uncontrolled roll its control system could not correct. Although a roll program is necessary for placing the vehicle on a proper heading towards orbit, this produced too much of a roll for the control system to compensate. The KORD detected this anomaly and attempted to shut down the Block A, but the guidance program had been modified to prevent engine shutdown until at least T+50 seconds. The roll began rapidly accelerating from 6° per second to 40° per second, resulting in gimbal lock. At T+48 seconds, stress caused the vehicle to disintegrate. Block V separated from the stack two seconds later and the thirty Block A engines shut down once again. The upper stages and L3 hit the ground about 4 miles (6.5 km) from the launch site. The lower stages continued to soar through the night sky before finally crashing 9 miles (14.5 km) downrange. The impact created a 50-foot (15 m) crater in the surrounding grasslands, but nobody was injured and the launch pad remained intact.
Once again, modifications were made to the next rocket in line to launch, N1 7L. Four hastily developed movable thrusters replaced the steering nozzles on the Block A to improve stability of the vehicle during flight, hopefully correcting the previous mission's roll program. Most noticeably, the iconic conical-shaped aft section of first stage was replaced with a new cylindrical skirt. This launch included a full L3 assembly consisting of operational Block D and Block G upper stages, a somewhat-operational LOK spacecraft, and a dummy LK. The mission's flight program required the insertion of the L3 into a near-equatorial lunar orbit before the LOK returning to Earth and splashing down in the Indian Ocean [5]. Chief Designer Vasily Mishin, who had replaced Sergei Korolev following his death in 1966, and his deputy Sergei Okhapkin were both hospitalized due to exhaustion in the days before launch.
On November 23, 1972, the fourth launch of the N1 program occurred around 9:00 AM Moscow time. 7L flew higher and longer than the previous three missions, though not enough to be declared a success. At T+90 seconds, when the vehicle was passing through max-q, the Block A's central engine cluster did not throttle down, but rather shut down, to reduce structural stress on the booster. This caused a hydraulic shock wave, in turn causing the fuel and oxidizer lines to burst. Engine 4 exploded as a fire erupted in the first stage. Block A broke apart at T+107 seconds, just seven seconds before scheduled main engine cutoff and booster separation. The upper stages were ejected and crashed into the Kazakh steppe while the emergency escape system pulled the LOK and LK to safety.
A fifth launch, N1 8L, was planned for August of 1974 and would have included flight-worthy Soyuz 7K-LOK and LK spacecraft. By this time, however, the Soviet Union was well into its Salyut and Almaz space station programs, and the Kremlin's patience had finally run out. The space industry shifted away from lunar missions and towards long-duration spaceflight, continuing to break human duration records as the US developed and flew the Space Shuttle.
But was the N1 doomed to fail as extraordinarily as it did? To start, development was underfunded and did not begin until late 1965, four years after development of the Saturn V began. When Sergei Korolev died unexpectedly in 1966, the project was badly derailed and Vasily Mishin, lacking Korolev's charisma and connections according to those who worked under him, inherited a program plagued with technical problems and delays. A number of factors contributed to the N1's failure, including
Engine reliability: The staged combustion cycle used by the thirty NK-15 engines was a new and unproven design and had a high failure rate during testing.
Development schedules and financial problems: To compete with Apollo on the other side of the world, the N1 faced tight deadlines and was rushed into development and testing. Funding constraints affected the quality of testing and manufacturing, and the lack of testing was due to the lack of infrastructure to perform such tests.
Lack of system integration: There were many issues with coordination among the numerous design bureaus, factories, and organizations.
Geopolitical factors: Immense pressure was put on the N1 program as Apollo progressed. Leadership changes during the program's lifespan (Nikita Khrushchev to Leonid Brezhnev as Premier, and Sergei Korolev to Vasily Mishin as Chief Designer as examples) caused priorities within the Soviet space program to shift, and internal competitions among design bureaus stalled development.
Mishin was dismissed from his position as Chief Designer in 1974. The Soviet Union officially terminated further attempts at sending cosmonauts to the moon in 1976. While in retrospect it may be easy to blame the failure of the N1 program on Mishin, a quote I came across while researching written by Mishin himself sums up the fiery, legendary defeat of the Soviet Union in the moon race: "We, the successors to Korolev, did everything we could, but it was not enough" b. The N1 is remembered more than half a century later by people across the world as a tragic, yet magnificent monster of a rocket whose legacy has been seared into the pages of history.
This post would not be complete without discussing the impact the N1 unintentionally had on the US. As mentioned earlier, in the spring of 1968, the CIA concluded through photos of a massive rocket on a launch pad taken by the NRO's CORONA reconnaissance satellite that the Soviet Union was preparing for a lunar mission during the latter half of the year. Speculation the vehicle was manned prompted Apollo program directors to ultimately move the launch of Apollo 8 from the spring of 1969 to the winter of 1968, ensuring American astronauts beat Soviet cosmonauts to the moon [6]. One hot August afternoon, the first crewed American moonshot was approved and on Christmas Eve, Frank Borman, Jim Lovell, and Bill Anders became the first humans in history to visit Earth's closest neighbor, the moon.
Revisions for this post were completed on April 20, 2023, the 51st anniversary of the Apollo 16 moon landing and the first launch of SpaceX's Starship. Hundreds of thousands, if not millions of people from all corners of the world watched this historic event via livestream or in person in Texas. The site of a colossal rocket sitting in the middle of a barren landscape was reminiscent of the mighty N1, whose final flight had turned fifty years old a few months ago. The most obvious resemblance was the Super Heavy's collection of thirty-three Raptor engines whose output of 16 million pounds of thrust put the N1's 10 million pounds to shame. As I sat in my apartment this morning and watched the enormous rocket slowly lift itself off its launch pad and soar into the cloudless sky before erupting into a spectacular cloud of fire and gas, I couldn't help but think of the N1 and how different the story of humanity's exploration of space could have been had it succeeded. But while spectators of the N1 explosions looked upon them with horror, those who bore witness to today's "rapid unscheduled disassembly" watched it with awe, some even with a sense of reverence. It was perhaps the closest my generation will ever get to experiencing an N1 launch and subsequent failure. History is bound to repeat itself, but only fools do not learn from it.
The N1's thirty NK-15 engines vs Super Heavy's thirty-three Raptors (RKK Energia and SpaceX)
Author's note: I know this post is longer than most of my others but I had a really fun time rewriting it. Let me know your thoughts on the N1 below and be sure to like and share!
[1] The US would come to this same conclusion in early 1962.
[2] The Saturn V's title as the tallest rocket ever built was recently broken by SpaceX's Starship, which stands a whopping 394 feet (120 m)!
[3] A Nova class first stage produces a thrust between 10 and 20 million pounds.
[4] Site 110 had two launch pads, "left" and "right".
[5] I was unable to find why the LOK descent stage would have splashed down in the Indian Ocean rather than the Pacific Ocean like the Apollo capsules.
[6] It was a little more complicated than this, but that's a story for another time.
Bibliography
David, Leonard. "New Secrets of Huge Soviet Moon Rocket Revealed." space.com, 7 Feb. 2011, https://www.space.com/10764-soviet-moon-rocket-secrets-revealed.html
Garcia, Mark. "50 Years Ago: Soviet's Moon Rocket's Rollout to Pad Affects Apollo Plans." NASA, 16 Nov 2017. https://www.nasa.gov/feature/50-years-ago-soviet-s-moon-rocket-s-rollout-to-pad-affects-apollo-plans
Wade, Mark. N1, www.astronautix.com/n/n1.html.
Zak, Anatoly. Russian Space Web, https://www.russianspaceweb.com/n1.html
[a] Zak, Anatoly. "Largest Explosion in Space History Rocks Tyuratam." Russian Space Web, https://www.russianspaceweb.com/n1_5l.html
[b] Mishin, Vasily. "Why we did not fly to the moon." 1990. via Zak, Anatoly. "People: Mishin." Russian Space Web, https://www.russianspaceweb.com/mishin.html
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