mercredi 10 octobre 2012

The Soviet N1-L3 Lunar Mission, LK in depth (Project aborted)

Soviet Lunar Program poster.

Oct. 10, 2012

On 3 August 1964, Command number 655-268 issued by Central Committee of Communist Party gave Soviet Chief Designer Korolev the objective of putting one man on the moon and returning him safely to earth - ahead of the Americans.

Prior to this, Korolev had concentrated on the earth orbit rendezvous method. His September 1963 L3 design was a 200 metric ton direct-lander requiring three launches of his giant N1 rocket and assembled in low earth orbit. This L3 spacecraft would make a precision 'blind' landing, homing in on a beacon aboard an L2 robotic lunar rover which had already been parked at a suitably flat touch-down point. The 138 metric ton trans-lunar injection stage would propel the L3 spacecraft towards the moon. The 40 metric ton lunar braking stage would ignite 200 to 300 km above the surface. After burnout, it would separate above the surface, allowing the 21 metric ton lunar soft landing/ascent stage, with variable-thrust engines to make a soft landing on the surface. The landing leg structure and soft landing engines would be left behind on the moon. The ascent stage would propel the 5 metric ton Soyuz L1 manned spacecraft back to earth. This capable but expensive spacecraft would have accommodated a crew of three for ten days of lunar surface exploration.

Two giant N1 rocket at the launch-pad

In order to beat the Americans, the redesigned N1-L3 exploited a variant of the Apollo program's lunar-orbit rendezvous method to reach the moon's surface. In this way the mission could be accomplished in just one launch of an improved N1 rocket. The L3 complex designed for the mission, with a total mass of 95 metric tons, would consist of the Block G translunar injection rocket stage; the LOK lunar orbiter; the LK lunar lander; and the Block D deceleration stage.

N-1 Soviet Manned Moon Rocket

The N1-L3 lunar flight plan evolved during the course of the program. By the end of LK development it was as follows:

The L3 complex would be injected into a 220 km, 51.8 degree inclination parking orbit of the earth. Up to one day could be spent in earth orbit before trans-lunar injection.

L3 complex separation (Orbiter SFS)

The Block G stage was ignited, putting the complex into a translunar trajectory. The Block G then separated.

During a 3.5 day translunar coast the Block D stage would perform two mid-course corrections. It then would brake the LOK/LK/Block D stack into an equatorial elliptical lunar orbit. The Block D would be restarted twice to adjust the orbit, first to a circular 110 km orbit, then to bring the pericynthion down to 14 km. The Block D could restarted for up to 4 days in lunar orbit.

The LK pilot would spacewalk from the LOK to the LK and check out the lander and Block D systems.

Russian manned lunar lander. 3 launches, 1970.11.24 (Cosmos 379) to 1971.08.12 (Cosmos 434). The LK ('Lunniy korabl' - lunar craft) was the Soviet lunar lander - the Russian counterpart of the American LM Lunar Module.

LK at Korolev

The LK was to have landed a single Soviet citizen on the moon before the Americans, winning the moon race. It completed development and test flown very successfully in earth orbit, but never reached the moon because the N1 booster required to take it to the moon never had a successful flight.

Because the translunar payload of the Russian N1 rocket was only 70% that of the American Saturn V, the LK differed in many ways from the LM. It had a different landing profile; it was only 1/3 the weight of the LM; it was limited to a crew of one; it had no docking tunnel (the cosmonaut had to space walk from the LK to the LOK lunar orbiter). Unlike the LM, the LK did not use a separate descent stage to go from lunar orbit to landing on the surface. A braking stage, the Block D, took the LK out of lunar orbit and slowed it to 100 m/s at an altitude of 4 km above the lunar surface. From there the LK used the engines of its Block E stage to soft land on the moon. The Block E also served as the ascent stage to return the LK to lunar orbit.

LK Landing Profile - Landing and abort profile of the LK lander. Credit: Mark Wade

The LK consisted of four primary modules:

    - The LPU landing gear, which allowed landing on the lunar surface. The LPU remained behind on the lunar surface, acting as a launch pad for the rest of the LK
    - The Block E rocket stage, which soft landed the LK on the moon and returned it to lunar orbit
    - The Lunar Cabin, the pressurized semi-spherical cabin where the cosmonaut was located
    - The Integrated Orientation System, a pod of small thrusters to orient the spacecraft. Atop the pod was the large hexagonal grid of the Kontakt docking system

Consider now the LK in depth. This article is organized into the following main sections:

    - The N1-L3 Lunar Mission Profile
    - Development of the LK
    - LK Flight Tests
    - Technical Description of the LK

The LK decent

The LK/Block D then separated from the LOK. The LK was capable of 72 hours of autonomous operation, 48 hours of which would normally be on the lunar surface. As it approached the landing site, the Block D began its main burn and braked the LK from to 100 m/s at four kilometers above the lunar surface. (Later in development this was reduced to 1.5 to 2.0 km above the surface). The Block D then separated and crashed on the moon about 4 km from the separation point.

LK landing on the Moon

The landing radar acquired the surface at an altitude of 3000 m. The LK's Block E stage then ignited its engines at full 2,050 kg thrust until vertical velocity reached zero. The engine was then throttled back to 850 kgf hover thrust and maneuvered to a soft landing on the surface. Propellant allowance for the whole maneuver was 280 kg, which allowed about 50 seconds hover time to divert to an alternate landing point up to 100 m away from that originally selected by the automated system. Later in development there was less than a minute total for the landing maneuver, including only 15 to 20 seconds of hover time.

LK Egress Tests

Image above: Another view of LK egress tests. This view makes clear the large size of the backpack of the Kretchet suit and the tight squeeze getting into and out of the LK lander. Credit: Filin

Four hours would be sent in surface operations on the first landing. The cosmonaut would exit the LK to the lunar surface. The space suit was limited to 1.5 hours on the surface at a time. The first Soviet space walk was to consist of: planting the flag; deployment of a very limited array of scientific instruments; taking soil samples; photography of the landscape; and cosmonaut commentary on the lunar surface. The LK could spend a total of from six to 48 hours on the lunar surface on later flights.

After returning to the LK's Lunar Cabin, the cosmonaut would seal the lunar samples in a hermetic container and then repressurise the cabin. The LK Lunar Cabin and Block E ascent stage would then take-off from the LK landing gear (LPU) and fly back into lunar orbit. The LOK orbiter would rendezvous and dock with the LOK using the 'Kontakt' system. The LK cosmonaut then space-walked from the LK back to the LOK with the lunar samples. The LK was then cast off.

LK landed on the Moon, EVA. Image : Screen capture from Celestia

After up to one additional day in lunar orbit, the LOK's Block I engine would put the LOK into trans-earth trajectory. 3.5 days was to be spent on the coast back to earth with two midcourse corrections en route. Before re-entry, the descent module separated from the LOK with the two cosmonauts aboard. It re-entered the earth's atmosphere over the South Pole at 11 km/sec, skipped back out to space after slowing down to 7.5 km/s, then soared 5,000 km before making final re-entry and landing on the territory of the USSR.

Krechet Lunar Spacesuit

Krechet lunar space suit as displayed at NPO Zvezda. As in the Orlan suit still used on Mir, the cosmonaut entered the suit by swinging open a hatch at the rear. The backpack containing the life support system was housed in the backpack which made up the hatch door. As in Apollo, the gold-coated outer visor of the helmet reflected ultra-violet radiation. The integrated Kretchet design meant that no external hoses were required as in the American Apollo suit. Credit: Andy Salmon

Development of the LK

The N1-L3 project was too big for one enterprise. Korolev's OKB-1 was assigned general management of the project. V M Filin was named manager for the LK within OKB-1. However detailed design, qualification, and construction of the LK Block E engine system was subcontracted to Yangel's OKB-586 in Dnepropetrovsk, Ukraine.

The advance design project for the N1-L3 was completed on 30 December 1964. The decree for production of 16 shipsets of spacecraft and boosters was issued on 26 January 1965. The N1-L3 was to manufactured to the following schedule: 4 in 1966; 6 in 1967; and 6 in 1968. The plan was for the first launch of the N1 to be in the first quarter of 1966, with the first lunar landings in 1967 to 1968, ahead of the American goal of 1969.

But as soon as detailed design of the LK began it was realized that the mass of the spacecraft in the draft project was completely unrealistic. The young engineers that had done the preliminary LK design had made numerous absurd assumptions. They had assumed a soft landing delta v of only 30 to 40 m/s (200 to 300 m/s was a more realistic estimate). A thirty degree braking angle was assumed after separation, but at this angle the radio altimeter couldn't detect the surface. Such optimistic assumptions resulted in the draft project putting the mass of the LK at 2 metric tons, with a crew of two. (The final LK would have a mass of 5.5 metric tons and be able to accommodate only one cosmonaut!).

Still, Yangel wanted to be sure to leave room for a crew of two in the cabin. But it was quickly discovered that this simply could not be done within the 40 to 50 metric ton low earth payload allotment for the LK/Block D. Given the original mis-estimate, throughout the project weight reduction was a constant concern. A separate descent stage would have had greater economy, but this presented numerous other problems not well understood when the project started. The Chief Designers offered prizes of 50 to 60 rubles per kilogram of weight reduction identified by project engineers. 500 kg was saved just by optimizing the rendezvous orbit.

LK First Mockup

The capability and accuracy of the landing radar system was the crucial first problem in development. The prompt and precise determination of the velocity and altitude of the LK after separation from the Block D was the key to minimizing propellant usage for the landing and determined the sizing of the whole LK vehicle (due to the propellant reserves required for touchdown and hover maneuvers).

The landing radar system was designated Planeta. Planeta consisted of four antennae, with their beams arranged in an asymmetric pyramid. Three determined the velocity vector using Doppler, while the fourth beam, in the central position, determined altitude above the surface. The system was simple and reliable. It was later proven on the Luna Ye-8 automated lunar sample return probes.

Numerous problems had to be solved regarding the reflection of the radar beam from the surface - problems analogous to those tackled a decade later in America in the design of stealth aircraft. Tests of the Planeta system aboard MiG-17 aircraft indicated that the initial radar reflectivity assumptions were wrong by several orders of magnitude.

Ignition of the Block E stage was commanded automatically by the Planeta system when the LK was 3 km from the touchdown point. After eliminating the vertical velocity, the final landing maneuver was commanded by the cosmonaut. Landing was made in the deep throttle range of the Block E. Engine shutoff was commanded automatically by the Planeta system.

OKB-1 Chief Designer Mishin allowed only a 280 kg propellant reserve for the entire landing maneuver. This constraint prolonged development of the Planeta system. In 1967 Yangel finally went to the Chief Designer's committee and informed them that he could not meet the requirement for two complete lunar landers until 1971.

Soviet LK lunar lander compared to US Lunar Module (LEM)

In 1968 the L3 scheme was overhauled. The original scheme had assumed a landing on the lunar equator. This meant that the LOK orbiter would pass over the landing site once per orbit, every hour. For the ascent of the LK to the rendezvous orbit in this case, a simple gyroscopic platform could accomplish the launch, as was used on the V-2 and R-7 missiles.

At landing sites away from the equator, within two to three orbits the LOK orbital plane would move too far away from the landing site to make such a pre-programmed ascent into the rendezvous orbit. Therefore a new type of guidance system was required. There were three possible choices:

    - Install a full-capability inertial navigation unit. This would allow the LK to perform a complex dog-leg maneuver during ascent to reach the plane of the LOK orbit (this was the American LM solution)
    - Use a strap-down gyroscopic platform to steer the LK in a pre-programmed deviation from its vertical axis until the LOK orbital plane position was reached.
    - Use the existing platform but develop a pre-set program of yaw angles, set before launch.

The second alternative was chosen. The LK would use the gyro platform to begin a bank maneuver at 25 to 30 km altitude. The program calculated the angle of tangency and the function of the cut-off of the LK engine. Soviet computer technology was not good enough at that time to equip the LK with an on-board re-programmable digital system. So instead an analogue parametric calculator was developed that took into account all conceivable problems and emergencies and the times at which they could occur. The resulting system was very effective and represented the major avionics system development for the LK.

LK drawing

A major difficulty during development was getting the cabin centre of mass on the thrust axis. It could not deviate more than 30 mm from the thrust axis or stable flight of the LK would not be possible. This requirement dictated the design of the propellant tanks of the Block E stage and Integrated Orientation System; required the development of special restraints for the cosmonaut in the cabin; and dictated the placement of equipment on the exterior of the LK. In particular the location of the heavy batteries was continually shifted during development.

LPU Development

The LPU - lunniy posadocnie ustroistviy - was the landing leg assembly of the LK. It would remain behind on the surface, acting as a launch pad for the Block E rocket stage. .Therefore the LPU not only to had to absorb the shock of landing, but provide a level base for the ascent stage as well. All systems not necessary for ascent were attached to it. A A Sarkisyan was in charge of LPU design.

The overall LK mass problem meant that there was only sufficient reserve propellant to move no more than 100 m from the original landing point selected by the automated system. Studies of Ranger photographs of the lunar surface indicated that the 100 m requirement meant that it was most likely the LK would land in a crater of 7 m diameter. This translated into the specification that the LPU be able to handle slopes of 30 degrees with the LK centre of gravity being 2.5 m above the surface. The requirement for high confidence unmanned landings also played a role in the stiff requirement.

The minimum design, as used on the US Surveyor, was three legs. But a three legged craft would require double the span of a four legged design for the same stability, and could not meet the thirty degree slope requirement. The design of the LPU was such an 'interesting' engineering problem that engineers from many sections of OKB-1 and Yangel's bureau proposed solutions. In the end over twenty variants of LPU landing gear layouts were studied, including toroidal rings, within which the LPU equipment would be housed, and some bizarre water-stabilized designs.

 LK LPU-Draft & Final

Image above: Detailed design of the LPU landing gear. At the top: design at the stage of LK draft project. At the bottom: the final production design.

Many of these ingenious approaches were too complex and mechanically risky. Finally V H Shaurov conceived the idea of 'nesting' engines - engines that would fire DOWNWARD at the instant of touchdown to remove all tipping moments from the spacecraft. This 'active' method of touchdown would reduce the complexity of the gear themselves while meeting the 30 degree requirement. In the end two gear schemes - passive (Feoktistov) and active (Shaurov) - were studied using scale models. Volcanic tuff believed to resemble the lunar regolith was imported from Armenia to simulate the lunar surface. A 300 x 400 mm sand pit was modeled with the tuff, including craters. The tests proved the active system, which was used on the LK.

A full scale mock-up of the final LPU design was built and tested. The shock absorbing techniques developed for the LK gear were later used in the androgynous APAS docking systems developed for Apollo-Soyuz and Mir. Kiselev proposed additional development of an altimeter-triggered soft landing rocket to cancel all vertical velocity, as was done for earth landings of the Soyuz system. But there was no time to develop the system.

Mounted on the LPU were those systems not required after the landing on the moon: the landing altimeter, parabolic antennae, chemical batteries, and three water tanks for the evaporative cooling system (a fourth was added late in development to trim the centre of gravity).

Lunar Cabin

A cabin environment using pure oxygen at 0.40 atmospheres was considered, but the need to develop special armatures, fire-proof materials, and the safety of the cosmonaut resulted in this being rejected. So the cabin environment selected was air at 0.74 atmospheres. This meant the cabin pressure vessel had to be twice as heavy, but this was considered worth it from a crew safety point of view.

LK interior

Soviet experience in manual control of spacecraft was limited at the time of LK development. The development team had to return to first principles in determining the control layout and the position of the cosmonaut. The challenging requirements included the need to operate the controls in a pressurized space suit in the event of cabin depressurization. Therefore foot pedals couldn't be used as in a fixed wing aircraft or helicopter. The design team consulted with helicopter and VTOL specialists at aviation design bureaus to solve these problems.

LK interior right

Development of the correct arrangement and placement of cabin control panels and windows was a long trial-and-error process. It was determined that the optimum viewing angle downwards for landing was 7 degrees. This lower view port was equipped with a collimator for predicting the landing point.

LK interior left

The Kretchet spacesuit developed, the ancestor of those still used on Mir today, could be entered through a hatch in the back. There was an elaborate system of braces and tie-down strips to fix the cosmonaut in a standing position during spacecraft maneuvers. This was because it was necessary to keep the centre of mass of the cosmonaut on the thrust axis of the engine.

Ingress/egress development was conducted again by trial-and-error, using full-size LK and suit mock-ups. It was found that the standard hatch developed for the Soyuz orbital module was too narrow for the cosmonaut in the lunar suit. So a special oval hatch had to be developed. This was a controversial solution but was finally approved. The asymmetric mass of the cosmonaut's ladder had to be balanced by placement of equipment on the other side.

LK panel

Due to weight considerations, no automatic docking system could be considered, as was used on the Soyuz spacecraft. The system objectives were minimum weight, manual operation, and tolerance to low accuracy docking. Since the cosmonaut would spacewalk from the LOK to the LK and back, no hard dock system, with system connections and a hermetic seal between the spacecraft, was required. The Kontakt system that was developed used a snare-like probe on the active LOK spacecraft. The LK was the passive vehicle, and was equipped with a 1.8 meter diameter, lightweight hexagonal alloy grid. Each of the 108 hexagons was a potential receptacle for the LOK's docking probe.

LK interior back

The Kontakt system was to have been tested on a series of earth orbit test flights using Soyuz spacecraft. These were postponed as continued N1 launch failures pushed the date of any possible lunar mission further and further back. In April 1969, two separate docking missions were planned for late 1969/early 1970. After Apollo 11's successful lunar landing, the development and launch of the Salyut space station (to beat the American Skylab) took priority. By December 1970, Kontakt missions were scheduled only after Salyut was successfully flown. Kontakt development was finally terminated in October 1971.

Block E Development

Originally development of the Block E landing/ascent stage was considered the pacing item in LK development. Drawings for the Block E were already issued in parallel with the draft project. The original specification of 510 kg empty mass for the stage could not be met. There were constant mass allocation fights between the rocket block design team and the cabin design team.

The LK variable-thrust, restartable engines represented a huge engineering development task. Unusually, Yangel decided to develop the system within his own OKB rather than entrust it to one of the traditional engine design bureau. New materials and new mechanical solutions were required to obtain a reliable, safe, redundant, durable engine that could be used over a wide variation of payload mass. In charge of Block E engine development was Ivan Ivanovich Ivanov, known to all as I-Cubed.

Close-up view of the engines of the LK exhibited at Korolev School

A key problem in design of both the Block E and the LPU was the flow of gases reflected from the surface during touchdown. In Apollo, the descent stage and its engine were left behind on the lunar surface; therefore it did not matter if the descent engine was damaged on landing (as actually occurred several times). But the LK used the same engine for landing and ascent from the surface. A hydrodynamic design had to be found that would prevent any damage to the engines during the landing maneuver. The final approach was streamlined propellant tanks for the Block E, which allowed the gases to flow up and away from the LPU during landing. The Block E engines were also equipped with clamshell doors, which closed at engine shut-off and prevented damage from foreign particles while the LK was on the lunar surface.

The propellant tanks were of unusual form. There were not only external gas flow considerations, but their geometry had to be specifically designed to keep the centre of mass within limits during the landing and ascent to orbit. Since the oxidizer was consumed at twice the rate as the fuel, the geometry had to accommodate this fact. Numerous tank layouts were studied before the optimum compromise between geometry and minimum mass was achieved. The self-igniting storable N2O4/UDMH propellants were stored in nested tanks of identical 1.2 cubic meter volumes.

Integrated Orientation System

The Integrated Orientation System was mounted above the Lunar Cabin. Yangel had no experience in microthrusters, so development of this system was subcontracted to Isayev. The same N2O4/UDMH propellant combination was used as in the Block E. The forward mounting of the package meant that the installation was 'unclean' - i.e. it introduced not only motion around the centre of gravity of the LK, but translation motions as well. The thrusters were arranged in two independent, redundant systems. In each system 2 x 40 kgf thrusters provided pitch; 2 x 40 kgf yaw; and 4 x 10 kgf for roll. Propellant totaling 100 kg was stored in two tanks. The problem arose how to preserve the centre of mass of the module on the main thrust line of the LK. The solution was to enclose the oxidizer tank within the propellant tank in a double-walled barrel construction.

 LK cutaway description (in Russian)

The thrusters were pressure-fed using internal diaphragms. This was the first use of such a technique in Soviet spacecraft, and a new steel alloy was developed by Stepanov for the purpose. The tanks were pressurized to 10 atmospheres by helium gas. Operation of the thrusters for continuous periods of up to ten seconds required development of new materials for the nozzles - niobium and graphite. Minimum thrust impulse was as lows as 9 milliseconds. The nozzles were canted 20 degrees from the horizontal when studies revealed that 95 out of 100 times a straight-through design would lose propellant after engine shutoff. This resulted in a mass savings to the LK of 12.5 kg.

LK Development

When the final drawings were reviewed, there was a major fight between the Yangel and Korolev bureaus over a 12 kg 'deficit' in the computed total mass out of the five metric ton total. Korolev's bureau used this to put the entire design into question. After frantic study, the difference was traced to calculation involving the inert gas used for propellant tank membrane pressurization.

Vibration and environmental tests were conducted on equipment at selected stages of fabrication and assembly. Flight tests were conducted of some components.

Military engineering experts from the Baikonur Cosmodrome had to review the design in order for it to be cleared for use at the launch site. They were experienced in missiles and could not understand the unpressurised operation of some of the equipment in a vacuum, the lack of aerodynamic fairings for cable runs, missing shrouds around the cables, etc.

LK lunar lander in assembly hall

Mock-ups and test stands used in LK development included:

    - Egress procedures mock-up. This was the first LK mock-up
    - Electrical test stand ('iron bird') to confirm logic and algorithms for control systems.
    - Electrical mock-up
    - Environmental test mock-up of Block E. This was tested in special vacuum / insolation environmental chambers. It was also used in heat balance studies.
    - Mock-up for antenna tests
    - Three Block E's for firing tests
    - Design of the landing system and cosmonaut training were accomplished on a specially-equipped Mi-4 helicopter, special test stands, and various partial task simulators.

LK Flight Tests

The T1K and T2K versions of the LOK and LK, respectively, were designed for independent earth orbital flight tests of the spacecraft. The T1K was to be launched by Proton and the T2K (also designated LK6/T2K ) by the Soyuz launch vehicle. This special 11A511L version of the Soyuz booster was equipped with a strengthened upper stage and bulbous fairing to accommodate the LK. An entire separate development team under Yu M Labutin was required to develop the special systems necessary for unmanned earth orbit test operations. 20 such systems were used on the T2K, including modifications of those developed for the Soyuz spacecraft. The Labutin team also had to decide what systems could logically be tested in earth orbit and which could not.

Three T2K's were built, in what was envisioned as a three flight program:

Flight 1 - Follow the standard engine profile Flight 2 - Induce or simulate various abort profiles Flight 3 - Reserve in case of failures on Flights 1 and 2

The flight programs were carefully constructed to allow time after each maneuver before the next one would be conducted. This allowed careful measurement of the resulting orbit after each maneuver in order to verify telemetered performance data, as well as time for playback of all telemetry, radio, and television of the events. It was difficult to arrange the schedule within the available LK battery amp-hours.

Inputs that would normally be done by the crew in the landing phase would have to be simulated and commanded from the ground. In order to accommodate the extra diagnostic and telemetry equipment, a second equipment section was installed on the T2K. Unique earth orbit sensors (solar/stellar, ion flow) were installed as well. These were required to orient the LK along the axis of the orbit.

The T2K crews worked day and night preparing the spacecraft, and finally the first T2K was shipped to Baikonur for launch. Each T2K was tested before flight in a vacuum insolation chamber. During vacuum chamber tests at Baikonur, one of the equipment sections decompressed. It was found to have had ten microscopic holes punched into it during transport. These were repaired. Finally fuelled and cleared for launch, the first T2K was launched on a sunny morning in November 1970. The three tests of the T2K went of without a hitch:

1970-11-24 - Cosmos 379 - T2K s/n 1: In demonstration of lunar landing and ascent maneuvers, first went from 192 km x 233 km orbit to 196 km x 1206 km orbit, with a delta V of 263 m/s representing the hover and landing maneuver after separation from the Block D. It them simulated the ascent maneuver to lunar orbit, going from a 188 km X 1198 km orbit to a 177 km X 14,041 km orbit with a delta V of 1,518 m/s.

1971-02-26 - Cosmos 398 - T2K s/n 2 - Second LK moon lander test using T2K version. Maneuver Summary: 189 km x 252 km to 186 km x 1189 km orbit, delta V 251 m/s; 186 km x 1189 km orbit to 200 km x 10,905 km orbit, delta V 1320 m/s.

1971-08-12 - Cosmos 434 - T2K s/n 3 - Final LK moon lander test using T2K version. Maneuver Summary: 188 km x 267 km orbit to 190 km X 1261 km orbit, delta V 266 m/s; 188 km x 1262 km orbit to 180 km X 11,384 km orbit, delta V 1333 m/s.

N1-L3 Moon Rocket Launch

End of the LK

A two-crew version of the LK was studied for support of the Zvezda DLB lunar base planned after the initial landings. Space was so limited that special recesses would have to made in the cabin wall to accommodate the helmets of the two suited cosmonauts. However this was a moot point, since the increased payload required major modifications of the engines and propellant tanks, which were specifically designed for the single-crew, 5,500 kg LK. In the end it was decided that this was not practical. Larger lunar landers were instead designed by Korolev's bureau using Soyuz return capsules and descent stages copied from the American lunar module layout.

Yangel died soon after completion of the successful T2K flights, content that he had done his part for the program.

LK landers are preserved at the MAI museum in Moscow (this was a flight model that was displayed at Eurodisneyland in 1997), the MAI museum at Orevo (an engineering article), St Petersburg, the Energia plant at Korolev, north of Moscow, and at KB Yuzhnoye in the Ukraine.

Soviet N1 moon rocket exploding & ending lunar program

Description of the LK

At the end of development the LK as designed had a mass of 5,560 kg, with the Block E stage weighing 2,950 kg. Takeoff mass from the lunar surface was 3,800 kg. The total height was 5.2 m. As with most aerospacecraft, the LK must be looked at from both a systems and a module viewpoint.

- LK Modules


The LPU - lunniy posadocnie ustroistviy - was the landing leg assembly of the LK. The LPU was able to handle slopes of 30 degrees with the LK centre of gravity being 2.5 m above the surface. Solid propellant 'nesting' engines fired downward at the instant of touchdown to remove all tipping moments from the spacecraft. Mounted on the LPU were those systems not required after the landing on the moon: the landing altimeter, parabolic antennae, chemical batteries, and three water tanks for the evaporative cooling system (a fourth was added late in development to trim the centre of gravity). A video camera was externally mounted to give the ground a view of surface operations. It may be calculated from data given that the LPU, with its associated equipment, had a total mass of about 1,440 kg (5,560 kg LK mass - 280 kg descent propellant - 40 kg orientation system propellant used during descent - 3800 kg given as LK mass at start of ascent).

Image above: Numerous tests were conducted to determine the best hatch and ladder configuration for the cosmonaut in the bulky Kretchet spacesuit.

Block E Rocket Stage

The streamlined shape of the Block E allowed engine exhaust gases reflected from the lunar surface to flow up and away from the LK during landing. The Block E engines were equipped with clamshell doors, which closed at engine shut-off and prevented damage from lunar soil while the LK was on the lunar surface.

Total Block E mass has been given as 2,950 kg. It was stated that the original specification of 510 kg empty mass for the stage could not be met; assuming a 10% weight growth during development, the empty mass was probably around 550 kg. This would give a propellant load of 2,400 kg (volumetric capacity of the 2 x 1.2 cubic meter tanks was 2,600 kg). Propellant consumption in the landing maneuver was 280 kg, leaving about 2,100 kg for the ascent into orbit. The engines were rated to burn up to 2,900


Crew Size: 1. Orbital Storage: 30 days. Habitable Volume: 5.00 m3. RCS Coarse No x Thrust: 4 x 390 N. RCS Fine No x Thrust: 4 x 98 N. RCS total impulse: 245 kgf-sec. Spacecraft delta v: 2,700 m/s (8,800 ft/sec). Electric System: 30.00 kWh. Electric System: 0.50 average Kw.

AKA: T2K; LK; 11F94.
Gross mass: 5,560 kg (12,250 lb).
Unfuelled mass: 3,160 kg (6,960 lb).
Height: 5.20 m (17.00 ft).
Diameter: 2.25 m (7.38 ft).
Thrust: 20.10 kN (4,519 lbf).
Specific impulse: 315 s.
First Launch: 1970.11.24.
Last Launch: 1971.08.12.
Number: 3 .

Images, Videos, Text, Credits: Roscosmos / Mark Wade / Andy Salmon / Filin / Dan Roam / Korolev Space Center / RKK Energia /