N1: The Rise and Fall of the USSR's Moon Rocket
Updated: May 30, 2021
The N1, or Raketa-nositel "rocket-carrier", was a Soviet heavy-lift launch vehicle intended to send Soviet cosmonauts to the moon. The N1-L3 version was designed to be the counterpart to the United States' Saturn V.
The N1 rocket in all its glory (NASA)
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 inter-continental ballistic missile (ICBM); and the N3 would be the replacement for Korolev's R-7 rocket, which was the world's first ICBM. It was in competition with the Universal Rocket (UR) series and the R-36. The Design Bureau selected the UR-100 rocket as the new "light" ICBM and the R-36 as the new "heavy" rocket. In 1961, when American president John F. Kennedy announced the goal of landing a man on the moon by the end of the decade, Korolev was given funding to start N1 development by 1963 with testing by 1965. At the time, the Soyuz spacecraft was being developed as well and Korolev proposed a lunar mission using the new craft and an Earth Orbit Rendezvous (EOR) profile, as opposed to the Lunar Orbit Rendezvous profile the US would pick a few years later. In short, EOR would require several launches of spacecraft and equipment, attaching in Earth orbit, and flying to the moon all at once. However, just as it would be realized at NASA, this would take way more time and resources than having a single launch so Korolev proposed a larger rocket. It is important to note that Vladimir Chelomei was proposing a series of circumlunar missions to beat the US to the moon, as well as his UR family of rockets. Though we will be focusing on the N1 and its role in the Space Race, we should keep in mind how different things could have been if different decisions had been made.
Comparison of different Soviet launch vehicles (Wikipedia Commons)
The N1 stood at 344 feet (105 meters) tall, making it the second-tallest rocket ever built (the Saturn V was 363 feet, or around 110 meters tall). The N1-L3 consisted of five stages, the first three for low-Earth orbit and the second two (the L3 portion) for translunar injection and lunar orbit insertion. The base was 56 feet wide. Unlike the Saturn V, the lower stages were arranged in a conical shape due to the arrangement of the fuel tanks. There was a modified design called the N1F but it did not fly before the project's cancellation.
Its first stage, Block A, is still to this day the most powerful rocket stage ever built, though it failed on all four N1 launches due to lack of static test firing that are performed to find and eliminate problems with the machinery and equipment. This stage had a whopping total of thirty NK-15 engines, which proved the theory that more engines aren't always the best plan for getting such a large vehicle up off the ground. Despite their multitude of failures, the NK-15s were the first staged combustion cycle engines, which means propellant is combusted in stages rather than all at once. The Block A also had four fins like the first stage of Saturn rockets. It ultimately produced 10,200,000 pounds of thrust, which did exceed the 7.5 million pounds of the Saturn V. Therefore, it is the only flown Nova class first stage [1] and is still to this day the most powerful first-stage ever built.
The second stage, Block B, consisted of eight NK-15V engines in a single ring. The "V" engine only differed in tuning. The N1F Block B replaced these engines with NK-43 engines. The third stage, Block V (V is the third letter in the Cyrillic alphabet) consisted of four small NK-21 engines in a square. The N1F would have replaced them with NK-31 engines. Additionally, the stage could function with three out of four engines working. At the very top of the stack was the L3, or Block G. It contained one stage for trans-lunar injection; one different stage used for mid-course corrections, lunar orbit insertion, and some of the descent to the lunar surface; a single-pilot LK Lander; and a two-pilot Soyuz 7K-LOK spacecraft for the trip back to Earth.
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 all launched and failed shortly after, some resulting in pad destruction. We'll cover those four rockets in a bit. 4L's Block A liquid oxygen (LOX) tank developed cracks and never launched; 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.
Its first launch of a string of failures was on February 21, 1969 from Baikonur launch site 110/38 for a lunar flyby. Its mission designation was 3L. A few seconds after liftoff, a voltage caused the KORD, the N1's engine control system, to shut down engine #12 and engine #24 shut down immediately after. At T +6 seconds, pogo oscillation in engine #2 shook the engine and started a propellant leak. This caused the highly combustable fuel to spill into the aft section of the booster, which in turn caused a fire. At T +68 seconds, the KORD shut down the entire first stage and "locked" the second and third stage engines to require the manual input of commands for engine fire. The entire rocket wound up falling back to Earth and crashing into the desert at T +183 seconds about thirty-two miles (fifty-two meters) from the launch site.
3L on the launch pad (russianspaceweb.com)
The second N1 launch was on July 3, 1969 and was intended for photography of possible manned landing sites on the moon. At this point in time, the US was only two weeks away from launching Apollo 11. It included a live escape tower, which is used to shoot the capsule away from the booster if the booster exploded. In fact, that's exactly what happened to 5L. As soon as the 340+ foot rocket cleared the tower, there was a flash of light and reports of debris falling from the first stage. Every engine with the exception of #18 immediately shut down and the rocket leaned over at a 45-degree angle, crashing back down onto launch pad 110/38. The two-thousand tons of propellant triggered a shock wave that shattered windows across the launch complex and sent debris flying as far away as six miles. Launch crews who went to investigate the wreckage reported droplets of unburned propellant raining from the night sky. And the launch escape system indeed worked- it carried the capsule away from the rocket the moment of engine shutdown. A mere twenty-three seconds had passed from takeoff to total complete destruction of both the rocket and the launch pad.
The firing of the launch escape system during engine shutdown (russianspaceweb.com)
The next launch, 6L, occurred on June 26, 1971- almost two years after the previous one. It included a dummy Soyuz 7K-LOK spacecraft and dummy LK module. Soon after liftoff, the rocket experienced an uncontrolled roll that the control system could not correct. Although a roll program is instigated after the rocket has cleared the tower during every launch to place the spacecraft on a proper heading towards orbit, this particular incident produced too much of a roll for the control system to compensate. Even though the KORD sensed an anomaly and wanted to shut down the first stage, the guidance program had been modified to prevent engine shutdown until at least T +50 seconds. The roll began rapidly accelerating from 6 degrees per second to 40 degrees per second, resulting in gimbal lock. Gimbal lock is the destabilization of a spacecraft. At T +48 seconds, the stress caused the vehicle to disintegrate. The third stage separated from the stack two seconds later and the engines, as in the other two launches, were shut down once again. The upper stages hit the ground about four miles from the launch site and the first and second stages continued their trajectory for a few moments before finally crashing back down to Earth nine miles from the launch site. The impact created a fifty-foot crater in the desert landscape.
6L during liftoff (russianspaceweb.com)
The fourth and final launch occurred on November 23, 1972, with the flight of 7L almost a month before the end of the American Apollo program. Of all four rockets, this one had the longest flight. At T +90 seconds, the six center engines (the core propulsion system) shut down to reduce structural stress on the booster. This is when the rocket experiences a period of maximum dynamic pressure, known as max-q, and its engines are throttled down to reduce the stress being applied. However, the engines were shut down completely rather than simply throttled down, in return causing a hydraulic shock wave. A hydraulic shock wave is when fuel in motion experiences a rapid momentum change. This caused the lines for feeding fuel and oxidizer to the propulsion system to burst and a fire erupted. To make matters worse, engine #4 exploded. The first stage broke up at T +107 seconds and all telemetry data stopped three seconds later. This launch also had a regular Soyuz 7K-LOK module and a dummy LK that were pulled to safety by the launch escape system. The upper stages were ejected and crashed into the Kazakhstan steppe. A fifth launch of 8L was planned for August 1974 and would have included both flight-worthy Soyuz 7K-LOK and LK modules. However, the program was cancelled a few months before that mission could take place.
7L, the fourth and final launch of the mighty N1 rocket (russianspaceweb.com)
By 1974, the Soviet Union was well into its Salyut and Almaz programs, the world's first space station, and had most definitely lost the moon race five years earlier (see "Diamond in the Rough: The USSR's Military Space Station Almaz"). The N1’s creator had died years earlier, its budget had been cut time and time again, and every launch had been a failure. In May 1974, the N1 program was mothballed and the USSR would hide its story from the world until the 1980s.
The N1 is also responsible for the first American moonshot: In the summer of 1968, the CIA found evidence of an N1 on the launch pad planned to launch by the end of the year. If this rocket was manned, the Soviet Union would be the first to the moon (though we know now it was not). This prompted Apollo Program directors to move the launch of Apollo 8 from spring of 1969 to winter of 1968, ensuring that if the rocket is manned it will not reach the moon before the US. That afternoon, Apollo 8's mission profile was changed completely and on Christmas Eve, Frank Borman, Jim Lovell, and Bill Anders became the first people to orbit the moon.
Earthrise taken by Bill Anders during Apollo 8 (NASA)
N1 Specifications
Height: 105 meters
Diameter: 17 meters
Dry Mass: 281 tons
Liftoff Thrust: 4,500 tons
Payload Mass to LEO: 95 Tons
Launches: 4
Successes: 0
Failures: 4
Launch Site: Launch Pad 110
Author's Note: Thanks for reading and be sure to like and share this post!
[1] Nova was a family of rockets that was proposed in the early 1960s for the lunar program. They never made it past the conceptual stage but the name Nova is used to describe a booster with thrust between ten and twenty million pounds.
Bibliography
Wade, Mark. N1, www.astronautix.com/n/n1.html.
Zak, Anatoly. “Freedom Project.” US Roots of the ISS Project, www.russianspaceweb.com/iss_us_roots.html.