Second Generation Lunars

By Charles S. Sheldon II[1917-1981], was Chief of the Science Policy Research Division of the Library of Congress, Congressional Research Service

1971-1975

THE SECOND GENERATION LUNAR PROGRAM

 1. Change of Technology

Luna 1, 2, and 3 had made direct ascents from Tyuratam to fly toward the Moon with net payload and total weights on the escape trajectories as follows: 361.3 and 1,472 kilograms; 390.2 and 1,511 kilograms; 278.5 (in A.I.S.) and 156.5 (in carrier rocket) for a combined weight of 435 and 1,533 kilograms respectively. All three flights had used the A-l vehicle; that is, the standard original ICBM, plus an upper stage which tripled the lift capacity over that of the A vehicle alone as used for the first Sputniks.

But the planetary program starting in 1960 had introduced an entirely new and more powerful upper stage, which replaced the original lunar upper stage. This planetary upper stage made it possible to raise the demonstrated weight in Earth orbit from about 4,700 kilo grams to about 6,500 kilograms, and later even to 7,500 kilograms. This also afforded an opportunity to mount a more ambitious lunar exploration program, by placing a Tyazheliy Sputnik orbital launch platform in orbit, as well as the separated third stage rocket casing. From the platform, generally over Africa , while completing the first revolution around the Earth, a probe rocket fourth stage could be fired to send a Zond away from Earth, carrying an A.I.S. On this basis, the weight of the gross payload could rise to 1,400 kilograms and better, not counting the added weight of the separated probe rocket which might be another 440 or even 1,000 or more kilograms.

2. 1963 Moon Attempt

The first improved lunar rocket was launched on January 4, 1963 . It failed to leave Earth orbit. Because it came during the period the Russians were uncertain as to how to describe such failures when failures were not acknowledged, this flight went unannounced until the United States disclosed it later in the spring in connection with the five Soviet planetary failures also stranded in Earth orbit in 1962.(8)

Luna 4 was launched successfully on April 2, 1963 and because it followed its planned trajectory, it was acknowledged and named by the Russians. It weighed 1,422 kilograms. Unfortunately, as it approached the Moon, it became evident the path was not quite correct, and it missed the Moon by 8,500 kilometers, entering a barycentric orbit around the Earth. Because its radios fell silent and these orbits are especially difficult to calculate through many completions, it is not certain whether it is still in this orbit or whether on some pass as it re approached the Moon it was accelerated to be flung off into heliocentric orbit.

3. 1965 Lunar Attempts

A lunar attempt occurred on March 12, 1965 , and failed to leave Earth orbit. With Russian public information rules settled on calling such failures Kosmos, this was named Kosmos 60 and passed off as routine.

Luna 5 was launched on May 12, and when its retrorocket system failed, it impacted in the lunar Sea of Clouds .

Luna 6 was launched on June 8. Because a midcourse correction failed, it missed the Moon by 160,000 kilometers. Although it may have gone into barycentric orbit, it is thought more likely to have gone to heliocentric orbit.

Luna 7 was launched on October 4, and the flight went well until the last minutes. Too early a retrofire and cutoff permitted it to impact in the lunar Sea of Storms too harshly to survive.

Luna 8 was launched on December 3, and again the flight went well until the closing minutes. Retrofire was late, and velocity was too high for survival when it impacted the lunar Sea of Storms .

Through all of these flights the exact mission had not been described, but it seems fairly evident that after the early strike missions and photo-fly-by, the missions from 1963 through 1965 were all aimed at a survivable landing for instruments on the lunar surface. This obvious supposition was later officially confirmed by the Russians after they attained successes. (9)

It is rather interesting to compare the problems experienced by the Soviet Union and the United States in their respective unmanned lunar landing programs. The time target for both was to achieve such missions in 1963. In the United States , its Surveyor craft actually was not ready for launch until 1966, when it became an outstanding success. The Soviet Union began making actual landing attempts in 1963, but did not meet success until 1966. This mission was more limited in its accomplishments than the Surveyor mission, but it did come first by a narrow margin, and answered the most basic questions about the problems of landing and what the surface was like.

4. The 1966 Lunar Attempts

Luna 9 was launched on January 31, 1966 , and a day later was announced as a soft landing attempt. Launched at Tyuratam by an A-2-e vehicle, it used the orbital platform technique to send its Zond probe toward the Moon. The payload at this stage weighed 1,583 kilograms. and consisted of three basic parts: The automatic lunar station itself which was to make the survivable landing on the Moon; motor units for making midcourse corrections in trajectory and for braking on approach to the Moon; and compartments containing apparatus to control the flight. That control equipment not needed during the braking maneuver or thereafter was contained in two underslung containers which were to be detached independently when the braking rocket was turned on.

The automatic station was a hermetically sealed container with radio equipment, a program timing device, heat control systems, scientific apparatus, sources of power, and a television system. The device had a shock absorbing system to soften the blow of landing, and then opened four petals outward which had protected the television system. Extended, they tended to stabilize the craft on the surface. With the petals open, spring controlled antennas also flipped out into operating position and the TV camera rotatable mirror system could begin a panoramic survey of the surroundings, both by revolving and by tilting.

The propulsion unit consisted of a rocket chamber with pumping system for the propellants, flight stabilization controls, and fuel tanks.

The control compartments contained a complex of gyroscopic and control instruments, electronic-optical devices for orientation of the station in flight, a system for radio control in orbit, a program timing device, a radio system for the soft landing, power sources, and micro-motors for orientation purposes.

The spacecraft made its landing in the Ocean of Storms , with Pulkovo Observatory at Leningrad catching this on film at 21:40:30 hours, Moscow time, February 3, 1966 , to become the world's first survivable landing on that body. This location is at 7°8' N. and 64°22' W. The approach to the Moon had been preceded by midcourse corrections, and data were supplied to the craft as to the amount of braking impulse required to achieve the landing. Telemetry return to Earth confirmed the conditions of the craft and that the right commands had been received. Final orientation occurred one hour before touchdown. At an altitude of about 8,300 kilometers, the craft assumed a strictly vertical position in relation to the Moon, and was held in this position by its sensors. At 75 kilometers, 45 seconds before touchdown, the retro rocket was switched on. Just before this the two compartments no longer needed in the operation were jettisoned to save weight. At the moment of touchdown, the station with its shock absorber was separated from the motor unit to land nearby. It took 4 minutes 10 seconds to employ the equipment and begin radio transmissions. It was about seven hours before television transmission began.

The Russians did not immediately release the pictures from the Moon, but Jodrell Bank in England was following events, and by hooking up a press wire facsimile machine the British were able to make public the first views from Luna 9. The British picture, lacking calibration data, distorted the scale in one dimension, and the combination of this distortion plus the unauthorized release annoyed the Russians according to TASS. But the British release created a credibility for the project which might otherwise have been harder to established in some quarters where Soviet reports tend to be discounted.

Batteries ran down in the craft on February 6 after seven radio sessions of 8 hours 5 minutes total duration, and the three series of television pictures when assembled provided a panoramic view as planned. The total weight of the landed small station was 100 kilograms. The camera itself weighed only 1.5 kilograms. A non-directional antenna was used to return the signals to Earth. The pictures showed rocks close at hand and the horizon at a distance of 1.5 'kilometers away. Pictures were taken twice on February 4, and once on the 5th, so that with changes in shadow length, different objects were highlighted. Also, there was some shift in the payload between the second and third picture series giving a slightly different perspective. As near as can be judged from the Soviet accounts each picture series involved in the panoramas included nine positions of the mirror.

Kosmos 111 was launched on March 1, 1966 , but failed to leave its low Earth orbit from which it decayed in two days. It is generally assumed that it was intended to be a lunar orbiter mission, but it could have been another Lander.

On March 31, 1966 , Luna 10 was launched toward the Moon from an orbital launch platform. The weight of payload sent toward the Moon was 1,600 kilograms. Apparently, the vehicle was structured like Luna 9 in terms of its propulsion, guidance, orientation, and communications elements, except that the landing station was replaced by an orbital station of a different nature. Luna 10 was braked to enter lunar orbit, the first man-made object to achieve this. The main propulsion unit was separated from the payload after lunar orbit was attained, and the remaining payload weighed 245 kilograms. The initial orbit was about 1,017 by 350 kilometers with an inclination of 71degrees 54 minutes to the lunar equator and had a period of 178.25 minutes. Although the prime purpose of the flight was science, at the 23rd Congress of the CPSU (Communist Party, Soviet Union ) the delegates were brought to their feet when the payload circling the Moon played back to Earth the strains of the Internationale.

Luna 10 was not equipped with a television camera, but it had a variety of instruments to return data. One task was the reporting of meteoritic impacts on the payload. Another was to determine the thermal characteristics of the Moon without interference of the Earth's atmosphere. Another had to do with study of the Moon's magnetism, if any. Also, there was a need to establish some notion of the irregularities of the Moon's gravitational field. One midcourse correction had been required on April 1, and then when it was 8,000 kilometers from the Moon, the braking engine was fired to drop the speed from 2.1 kilometers per second to 1.25 kilometers per second so that it could go into orbit. The payload was separated 20 minutes after the end of retrofire.

The listed instruments were: A meteorite particles recorder; a gamma spectrometer; a magnetometer; instruments for studying solar plasma; a recorder for infrared emissions from the Moon; and devices to measure radiation conditions in the Moon's environment. The gravitational studies were pursued as a byproduct of the tracking. The device was battery-powered, but by careful husbanding of this electrical supply, it was possible to continue to receive radio signals from the payload until May 30, 1966 . By this time there had been 460 orbits of the Moon, and 219 active transmissions of data.

By placing the payload in an orbit inclined at 72 degrees to the lunar equator, it was able to take readings over much of the surface over a period of time. The stunt of sending back music was achieved by programming some semiconductors to emit a definite sequence of electrical oscillations.

The payload found a magnetic field around the Moon about 0.001 the strength of that around Earth. Cosmic ray background levels were slightly high, as expected. The natural radiation of lunar rocks was determined to resemble most closely that of basalt on Earth. The intensity of meteoritic impacts was higher than in interplanetary space. Some of the observed radiation from the lunar surface was believed to come from interactions with cosmic rays rather than from natural radioactivity within the rocks. Particles of the Moon's radiation belts were estimated to be present to only one-one hundred thousandths that of Earth in the corresponding zone. The gamma ray spectrometer was that of the multiscintillation type, to cover energies between 0.3 and 3 million electron volts. The magnetometer had three channels at reciprocally right angles. The ion trap was modulated to register positive ions down to an energy level below 10 electron volts, while the four electron traps would measure a full stream of ions if exceeding 50 electron volts.

Luna 11 was launched on August 24, 1966 with a weight sent toward the Moon of 1,640 kilograms. It was launched from an orbital launch platform, and later a midcourse correction was performed. It approached the Moon on August 28, when retrorockets were fired to place it in lunar orbit. Less was said about this flight than about Luna 10. Most of the early bulletins merely reported that communications were stable, and how many orbits had been accomplished. A month after launch, the mission was described as studying gamma and X-ray emissions of the Moon to determine more exactly the chemical composition of the Moon, and studying gravitational anomalies in the Moon. Additionally, this satellite was studying the concentration of meteoritic streams, and intensity of hard corpuscular radiation near the Moon. This payload was put into an orbit between 1,200 and 160 kilometers, at an inclination of 27 degrees with a period of 178 minutes. Not much more was said until the announcement that the batteries had been used up by October 1, 1966 , after 137 radio sessions, and 277 orbits of the Moon.

No picture has ever been released of this payload, and very little has been published about the findings. An early Soviet announcement suggested in a vague way that this was improved over Luna 10. Jodrell Bank intercepted signals that suggested that Luna 11 was intended to return television pictures from lunar orbit. (10) This combination of facts suggested that Luna 11 resembled Luna 12, the next in the series, but that it fell well short of its planned functions.

Luna 12 was launched on October 22, 1966 toward the Moon, also employing the usual orbital platform technique. A midcourse correction was carried out, and the ship was placed in lunar orbit on October 25. The orbit was first given as 1,740 by 100 kilometers with an "equatorial" inclination and a period of 205 minutes. Later it was announced as 1,200 by 133 kilometers, at an inclination of 10 degrees. On October 29, it returned pictures of the lunar surface by radio facsimile. The system used was to take pictures with a camera, develop these photographic films on board, and then scan the pictures for radio transmission to Earth. No weight was announced for this payload, but it was probably close to that announced for Luna 11.

The appearance of Luna 12 differed from Luna 10 mostly because of the large radiator covering much of the instrument compartment. Those parts of the scientific apparatus which did not need to be air tight—the antennas, and the gas reserve spheres for the micro-steering engines were also external to the body of the station. The propulsion unit of the liquid fuel rocket, its pumping system, control devices, and fuel tanks were little changed from earlier Luna or Zond payloads. Again, there were separate attached compartments to contain the astro-orientation devices consisting of gyroscopes, electro-optical instruments, and program timers to be cast loose just before retrofire. These were both to orient the total craft for midcourse and braking maneuvers, and those that went with the payload to align the spacecraft during picture-taking sequences while circling the Moon. The main instrument compartment of the orbiter contained the major experiments, radio receivers and transmitters, and the automated photographic and facsimile picture processing equipment. Pictures apparently were first transmitted to Earth at a fast data rate for a quick scan at the deep space tracking facility, and then retransmitted at a slower rate to maximize the detail for more thorough study later. The pictures contained 1,100 lines of scan, to give a maximum resolution of 15 to 20 meters. When the last had been transmitted, the facsimile/television unit was switched off to conserve power. It is not known how many pictures were taken, compared with Zond 3 which had taken 25. Only two or three seem to have been made public from the Luna 12 flight. "Radio transmissions from this craft ended on January 19, 1967 , after 602 orbits of the Moon, and 302 radio sessions with Earth.

Luna 13 was launched on December 21, 1966 . It repeated the operational steps of its predecessors, and landed on the Moon on December 24 in the Sea of Storms at 18° 52' X. and 62° 0.3' "W. Four minutes; after landing it began to transmit to Earth, having opened its petals, sprung out antennas, and warmed up radios. A day after landing, it began to send back photographs of the surface in the same manner as Luna 9. The first successful Lander had gone into mountainous terrain (lurain), and this one was on a lunar seabed, but the general appearance of the surroundings were much the same. Luna 13 differed from Luna 9 in that it carried two telescoping arms which were gunpowder-controlled, once extended, to swing outward and down from the craft to thump the lunar surface so that sensors could judge something of the density and firmness. The 16 degree tilt of the station away from horizontal meant that the panoramic swing of the mirror on the camera permitted views at a distance of less than one meter to show objects of millimeter size, graduating out to other views of the lunar horizon.

Some days after the landing, the lunar soil properties were described as having to a depth of 20 to 30 centimeters the mechanical properties of average density terrestrial ground, but general density at the landing site was believed to be less than typical Earth ground density. Little radioactivity in the soil was detected. The impact device could develop a pressure of 23.3 kilograms to force a rod into the soil. These data from the impact device were compared with accelerometer data from the actual deceleration in landing, leading to reasonably consistent findings on the mechanical properties of the soil. The actual density was estimated by direct measurements of the volumetric weight by means of gamma quanta. Density was estimated as not exceeding one gram per cubic centimeter, much less than both terrestrial ground or average density of the Moon.

It was also determined that the lunar surface reflects about 25 percent of particles of space radiation which fall upon it, consistent with the Luna 9 data. Observed stones looked like local debris, not meteorites.

It was also revealed that the camera and television system required about 100 minutes to transmit an entire panoramic view of the surroundings. From the absence of further reports, it is likely the batteries ran down before the end of December 1966.

5. 1968 Lunar Attempt

Sixteen months were to pass before the concluding flight of the second generation Luna series came about. Luna 14 was launched on April 7, 1968 . After the usual midcourse correction, the braking system slowed it on April 10 to place the payload in a lunar orbit, ranging from 870 to 160 kilometers, at an inclination of 42 degrees, and with a period of 160 minutes. No weight figures and no pictures were released on the craft. But the listed experiments most closely resembled those of Luna 10, the first orbiter. These were aimed at studies of interactions between the mass of the Earth and the Moon, studies of the Moon's gravitational field, the propagation and stability of radio communications between Earth and spacecraft, measures of the stream of charged particles from the Sun, and formulation of a precise theory for the Moon's movement. Not announced until two years later, this vehicle and Luna 12 earlier had carried out tests of the type of electric motor used to provide locomotion on Lunokhod 1 in 1970.

The President of the Soviet Academy of Sciences, Keldysh, stated that the flight would have enormous significance for future, more ambitious flights to the Moon. No published data have been discovered to indicate the termination of this experiment, although it was still operating normally at the end of April 1968.

References

1. SOVIET SPACE PROGRAMS, 1971-75, OVERVIEW, FACILITIES AND HARDWARE MANNED AND UNMANNED FLIGHT PROGRAMS, BIOASTRONAUTICS CIVIL AND MILITARY APPLICATIONS PROJECTIONS OF FUTURE PLANS, STAFF REPORT , THE COMMITTEE ON AERONAUTICAL AND SPACE .SCIENCES, UNITED STATES SENATE, BY THE SCIENCE POLICY RESEARCH DIVISION CONGRESSIONAL RESEARCH SERVICE, THE LIBRARY OF CONGRESS, VOLUME – I, AUGUST 30, 1976, GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976,

8. Letter of June 6, 1963 from Ambassador Adlai E. Stevenson to the Secretary General of the United Nations

9. TASS. April 4, 1966 , 0756 GMT.

10. Reuters, Moscow , August 30, 1966 , carried In the New York Times of August 31, 1966 .