THE N1 HISTORY

Text and pictures from Rockets of the World.

In 1960, Sergei Korolev proposed a giant booster capable of launching, 40 to 50 metric tons (88,00 to 110,000 lb) into low Earth orbit. This projected rocket, with ten times the payload capacity of the existing Vostok booster, was called the N1. V. P. Glushko, the Soviet Union's premier rocket propulsion expert, felt that it would be prohibitively expensive to build immense oxygen-hydrogen engines like the F-1's that would power the American Saturn V. Instead, he proposed large engines burning unsymmetrical dimethyl hydrazine (UMDH) and nitrogen tetroxide (N₂0₄). These propellants. used in the American Titan, are storable and ignite on contact. But they are less efficient than liquid oxygen and kerosene, and are highly toxic. Korolev instead chose to power the lower stages of his super booster with liquid oxygen and kerosene. Glushko took his technology to the Chelomei design bureau, which selected his engines to power the UR500 Proton booster. Korolev turned to the design bureau of Nikolai Kuznctsov (NK) for the Ni's engines.

In its original form, the first stage of the N1 was to be propelled by a ring of 24 engines. Air would be vented into the space inside the ring, where external combustion of exhaust gasses was supposed to augment the rocket thrust.

Like the American Saturn, this super-rocket had no specific mission at first. Development of the N1 began in 1961, the year of US President Kennedy's commitment to place an American on the Moon by the end of the decade. But the N1 was not chosen to carry a Soviet citizen to the moon.

That job was assigned to the Proton, which would only make a circumlunar flight.

It was not until 1964 that the Soviet Union made a secret decision to use the N1 to land a man on the Moon before the Americans. Through the mid-60's, as the lunar landing mission evolved, the N1 grew through a series of re-designs, eventually doubling its low Earth orbit capacity to 98 metric tons (109 US tons). The central air vents were replaced by six additional engines. By the beginning of 1967, the N1 booster's design was nearly done, as was the design of the L3 lunar spacecraft. By November, a mock-up was on the pad.

The N1 stood 105 meters (344 ft) tall and weighed 2788 metric tons (6.1 million lb) fully fueled. This compares with 110.7 meters (363 it) and 2913 metric tons (6.4 million lb) for the American Saturn V. The first three stages of the N1, blocks A. B, and V. each took the form of a truncated cone containing a spherical kerosene tank above a larger liquid oxygen (LOX) tank. The first stage, Block A, was powered by 30 NK-33 engines, together producing 4620 metric tons (10 million lb) of thrust. This far exceeded the 3469 metric ton (7.65 million lb) thrust of the American Saturn V Moon rocket. The N1's "KORD" (Russian acronym for control of the work of the engines) system steered the rocket in pitch and yaw by throttling the 24 fixed outer engines. Roll control was maintained by routing engine turbine exhaust through six swivelled nozzles. Arrayed around the base of the N1's first stage were four grating stabilizers, each consisting of a cross hatched array of metal strips (acting as fins) held in a horizontal frame After a first stage burn of 110 seconds. the second stage was to ignite its eight NK-43 engines for a 130-second burn. Finally, the third stage would insert the L-3 complex into orbit with a 400-second burn of its Four NK-31 engines.

The L3 spacecraft complex was concealed in a shroud topped by emergency escape rockets. During the second stage burn, the shroud would be jettisoned. revealing the four principal units of the L3 system. The kerosene-LOX Block G rocket served as the fourth stage of the N1, and was to send the craft on its translunar trajectory. The Block D fifth stage, also burning kerosene and LOX, served multiple functions. First, it would provide course corrections on the way to the moon, It would slow the L3 spacecraft to enter lunar orbit. Finally, it was to slow the lunar module (Block E) to drop it from lunar orbit down to an altitude of about a kilometer (0.6 mi). The lunar lander itself' was a small spherical craft with four landing legs and a single rocket engine burning N₂O₄ and UMDH. The final section of' the 1.3 spacecraft was the Block I lunar orbiter, a Soyuz spacecraft with an enlarged service module powered by an engine burning N₂0₄ and UMDH to return the cosmonauts to earth.

According to the L3 flight plan, once the Block D stage slowed the craft into lunar orbit, one cosmonaut would transfer to the lander by space walk. No pressurized tunnel was provided between craft. The lunar lander and attached block D stage would separate from the Soyuz for the descent to the Moon. About a kilometer (0.6 on) above the surface the block D was to separate from the lunar lander, which would descend the final distance under its own power.

The single cosmonaut on the lunar surface would carry out a program similar to that of Apollo 11, planting a Soviet flag, leaving a number of experiments, and picking up rock and soil samples. The spacecraft could support the cosmonaut on the moon for a couple days, although a Moon walk could last no more than an hour and a half. Once the lunar exploration was complete, the cosmonaut was to ride to lunar orbit under the power of the lander's single engine. The Block E module would leave only its landing legs behind.

The lunar lander and extended Soyuz would dock in orbit, and the landing cosmonaut would transfer himself and his samples by space walk. After discarding the lander, the Block I lunar Soyuz would fire its engine for a return to Earth.

The Moon landing project was an expensive and time-consuming venture. To hasten the completion of the project, and to keep costs down, the complete first stage of the N1 was never static tested on the ground. As a result, the Soviets managed to load the first N1 booster onto its pad at Baykonur on May 7, 1968, only four years after approval of the Moon landing program. But the Soviets were failing behind the Americans, who had already launched two unmanned Saturn V boosters. The Soviets would not catch up quickly, as cracks were found in the first stage structure. The booster was rolled back to the hangar for repairs. The N1 would not fly until the next year.

It was a clear day at the Baykonur Cosmodrome when the thirty engines at the base of the first N1, unmanned flight 3L, came to life at 12:18 PM on February 21, 1969. Even before liftoff, there was a minor malfunction. A safety feature of KORD steering system was the ability to maintain thrust symmetry by shutting off an engine directly opposite any that malfunctioned. But KORD itself malfunctioned, shutting off a pair of healthy engines. In spite of the malfunction, a ring of explosive bolts detonated at the base of the rocket, allowing it to lift off. Powered by 28 of 30 engines, the N1 still rose faster than the American Saturn that had sent the three Apollo 8 astronauts around the Moon two months before. N1-L3 could still fly by the Moon with two engines out, as a longer burn by the remaining engines would compensate for the loss of thrust.

But the erroneous KORD cutoff triggered a fire in one of the shut down engines. Within a minute, the fire spread to the cabling and propellant lines for other engines. The KORD system shut down the entire first stage, and triggered the firing of emergency escape rockets that carried the L3S (unmanned L3) payload away from the booster as if it had been manned. The booster followed its suborbital trajectory to a point 45 km (30 mi) from the pad and crashed into the ground.

At 11:18 PM Moscow time on July 3, 1969, less than a month before the flight of Apollo 11, the second N1, flight 5L, lit up Baykonur with the flames of its 30 engines. But less than a quarter second before liftoff, a bit of metal from a pressure fluctuation sensor made its way into a pump, triggering an explosion in one engine. In the half-second after launch, KORD shut down four engines. The remaining 26 engines struggled 200 meters (600 ft) above the pad as the tail section blew to pieces. Within ten seconds of launch, all engines were commanded to stop, yet one continued to burn. The remaining engine merely spun the rocket about its axis as it collapsed back onto the pad. The explosive impact destroyed the N1 the pad, and ground support equipment, as well as damaging a neighboring pad and a second N1 booster. Only the unmanned L3S spacecraft survived, carried to safety by its escape rocket. The N1 would not fly again for 2 years.

On June 27, 1971, a third N1 flight 6L, lifted off from Baykonur. This vehicle reached an altitude of 250 meters (800 ft) before a control failure set the rocket rolling about its axis. The spin caused the rocket to twist apart between the second and third stages. The upper stages toppled and exploded while the first two stages shot past, out of control. The lower stages crashed 30 km (20 mi) away, blasting a crater 30 meters (100 ft) wide and 15 meters (50 ft) deep.

N1 flight 7L featured an improved first stage. The tail skirt was trimmed down and the fuel line fairings streamlined to reduce air resistance. On November 23, 1972, N1-7L lifted off, bearing the final L3S craft. This time, the N1 performed flawlessly-for 107 seconds. Then unexpected vibrations began, and before staging, the mighty booster fell to pieces and exploded.

Two more N1's were assembled for flights in 1974 and 1976. But in 1974, propulsion expert V. P. Glushko took over the Korolev design bureau from V. P. Mishin (who had taken over upon Korolev's death in 1966). Glushko had not liked the N1 program since Korolev had rejected his innovative choice of propellants. Glushko canceled the N1, renamed the organization Energiya, and set out to build a large rocket using high-energy propellants.

The remaining N1's were dismantled, their engines put into storage, and their airframes scrapped or adapted into storage sheds. The L3 hardware that wasn't scrapped was placed in closed museums for aerospace engineers only. And for 15 years, the Soviets continued to pretend the project never existed. Only in 1989 did the Soviet Union acknowledge the existence of the Moon program.

The story of the N1 is not over. In the post-Soviet era, several western aerospace companies have considered using N1 engines in various internationally-developed space boosters. In the United States, Aerojet has purchased two examples of the NK-33 engine for static tests. Aerojet is considering manufacturing these engines under license to power new versions of the American Atlas and Titan.

The first N1 booster, 3L, moments before ignition.

If you don't have a copy of Peter Alway's wonderful Rockets of the World, you definitely need one. Material like this, and even more, exists for most rockets built and provides a treasure trove of information for modelers and those interested in space. They can be purchased directly through the publisher, Saturn Press, or at larger bookstores.