N1 (rocket)

History

The N1/L3 program received formal approval in 1964, requiring a launch vehicle comparable to the American Saturn V. On 25 November 1967, less than three weeks after the first Saturn V flight on Apollo 4, the Soviets rolled out an N1 mock-up (designated 1M1) to launch pad 110R at Baikonur Cosmodrome. This Facilities Systems Logistic Test and Training Vehicle was used to gain experience in rollout, pad integration, and rollback, similar to the Saturn V Facilities Integration Vehicle SA-500F testing at Kennedy Space Center in mid-1966.

Unlike the Saturn V, which was transported vertically by crawler, the N1 was moved horizontally and raised to vertical at the pad using a Transporter Erector named Grasshopper. On December 11, after tests, the mockup was lowered and rolled back. Although the test was secret, a US reconnaissance satellite photographed the N1 on the pad, leading NASA Administrator James Webb to see that the USSR was seriously planning crewed lunar missions. The imagery did not reveal the rocket was a mockup, though the CIA, NRO, and President Lyndon B. Johnson knew from a daily briefing of 27 December 1967. The Soviets hoped for a test flight in early 1968, but technical reasons delayed it over a year.

Description

The N1-L3 consisted of five stages: the first three for low Earth orbit insertion, and two more for trans-lunar injection and lunar orbit insertion. The lower three stages formed a frustum 17 m wide at the base, with a conical shape due to a smaller spherical kerosene tank atop a larger liquid oxygen tank. The L3 section was mostly cylindrical, inside a shroud about 3.5 m wide. The first stage, Block A, used 30 NK-15 engines in two rings: an outer ring of 24 and an inner core of 6.

Control came from differential throttling of the outer ring engines; the core was not used for control. Block A had four grid fins, later used on Soviet air-to-air missiles, and a planned burn time of 125 seconds. Its dry mass was 180.8 tons. The stage produced 45400 kN of thrust, exceeding the Saturn V's 33700 kN, a record that stood until the SpaceX Super Heavy in 2023. An improved version, the N1F, was designed but never flew.

Launch history

The first launch attempt occurred on 21 February 1969 with serial number 3L, carrying a Zond L1S-1 spacecraft for a Moon flyby. Seconds after liftoff, a transient voltage caused the KORD analog computer to shut down Engine #12, then Engine #24 to maintain symmetry. At T+6 seconds, pogo oscillation in Engine #2 tore components loose and started a propellant leak. At T+25 seconds, a ruptured fuel line spilled RP-1 into the aft section, igniting a fire that burned through wiring.

The KORD interpreted resulting electrical arcing as a turbopump pressurization problem and shut down the entire first stage at T+68 seconds, also locking the second and third stages. Telemetry showed power generators continued functioning until impact at T+183 seconds. The rocket's remains were found 52 km from the pad. Vasily Mishin initially blamed the generators, but telemetry and recovered generators—which worked fine in bench tests—disproved this.

The investigative team did not speculate whether the burning first stage could have continued without the KORD shutdown.

Confusion on L3 designation

Russian online sources sometimes show the designation as N1-L3 or N1-LZ, due to the similarity between the Cyrillic letter Ze (Z) and the numeral 3; both forms may appear on the same website or article. English sources use only N1-L3. The correct designation is L3, representing one of five branches of Soviet lunar exploration: L1 for crewed circumlunar flight (partially realized in Zond), L2 for an uncrewed lunar rover (Lunokhod), L3 for a crewed lunar landing (using LOK orbiter and LK lander), L4 for a crewed spacecraft in lunar orbit, and L5 for a heavy crewed lunar rover.