NASA’s Ranger 3: The First Attempt to Land on the Moon

NASA in general, and the Jet Propulsion Laboratory (JPL) in particular, are well known for their string of highly successful robotic missions over the last few decades to explore the Moon and the planets beyond. However, these successes came at the expense of many frustrating failures during the early years of the Space Age as these institutions grappled with developing the cutting-edge technology as well as engineering and management practices required for mission success. One of the more painful series of failures involved the trio of Block II Ranger missions which made the first attempts to hard land a scientific package on the Moon during 1962.

 

The Ranger Program

During the opening years of the Space Age, NASA struggled to get probes to the Moon, initially with programs it had inherited from the Department of Defense (see “NASA’s Forgotten Lunar Program”). Out of all of its attempts, only the diminutive Pioneer 4 built by JPL and launched on March 3, 1959, by a team at the Army Ballistic Missile Agency (ABMA) headed by Wernher von Braun (which would become the basis of NASA’s Marshall Space Flight Center) managed to break free of the Earth and make a distant flyby of the Moon (see “Vintage Micro: The Pioneer 4 Lunar Probe”).

By the end of January 1960, NASA’s first totally new lunar project, Ranger, had taken form. It was managed by JPL and would attempt to hard land a small package on the lunar surface while returning close up images during its descent. The first five flights of the new series would use two spacecraft types designated Block I and Block II that would be launched using the new Atlas-Agena B rocket.

Development of the Agena upper stage began in July of 1956 under a USAF contract with the Lockheed Missiles and Space Company (a corporate antecedent to today’s aerospace giant, Lockheed Martin). This stage was specifically designed for use with a modified Douglas Thor IRBM or General Dynamics Atlas D ICBM as the booster. The Agena B was an upgraded version of the original Agena A. While the B-model kept the original 1.5-meter diameter of the stage, it was lengthened by two meters to 6.30 meters to support a larger propellant load. The original A-model’s Bell Aerospace Hustler 8048 engine was replaced with an upgraded 8081 which generated 71 kilonewtons of thrust and possessed an in-orbit restart capability. This capability allowed the Agena ignite at exactly the right moment during its coast in an Earth parking orbit to ensure an accurate injection into its desired trajectory. The first flight of an Agena B took place on November 12, 1960 when a Thor-Agena B launched Discoverer 17 into orbit. The stage’s all-important restart capability was tested for the first time in flight with a one-second burn by Agena 1102 during Discoverer 21 mission launched on February 18, 1961.

The Atlas-Agena was originally designed to place large payloads, such as the MIDAS experimental early warning satellite and the SAMOS reconnaissance satellite, into medium altitude Earth orbits. The Atlas-Agena A flew only four times between February of 1960 and January of 1961 with limited success. The first flight of the improved Atlas-Agena B took place on July 12, 1961, with the successful launch of MIDAS 3. The three-meter in diameter Atlas D was modified for this task by stiffening its forward bulkheads to handle the heavier payload and eventually Atlas’ original MA-2 propulsion systems was replaced with the uprated MA-3 system being used on the improved Atlas E/F silo-based ICBM then under development. This boosted the liftoff thrust of the 30-meter-tall Atlas-Agena B to 1,820 kilonewtons. The Atlas-Agena B was capable of launching payloads of 2,300 kilograms into a 480-kilometer orbit or up to about 330 kilograms towards the Moon.

The first two flights of the Ranger program would make use of the Block I spacecraft. They were meant to be engineering test flights that would place Ranger into an extended Earth orbit. These 307-kilogram, three-axis stabilized spacecraft would be the forerunner of not only the Ranger Moon probes but also the Mariner spacecraft then being designed to explore the planets Venus and Mars (see “The Prototype That Conquered the Solar System”).

The main bus of the Block II Ranger was similar to the one used by the Block I test craft. It consisted of a hexagon-shaped magnesium frame bus 1.52 meters across. The various compartments of this bus contained the spacecraft’s central computer and sequencer which controlled the spacecraft, a battery to provide backup power, a radio transmitter, and the attitude control system. Attitude reference was provided by six Sun sensors, two Earth sensors, and three gyros. Extending from the sides of the bus were two solar panels holding 8,680 solar cells to provide up to 210 watts of electrical power for the spacecraft. Also extending from the base was a hinged dish-shaped high-gain communications antenna 1.22 meters across, which would be pointed at Earth with the aid of a light sensor. The spacecraft could communicate with the Earth either through this high gain antenna or a cone-shaped omnidirectional antenna at the top using a 3-watt transponder. The spacecraft maintained its attitude using a set of ten gas jets supplied by 1.1 kilograms of compressed nitrogen gas held in three tanks.

Unlike the Block I Ranger, which was topped by an instrument-laden truss structure, the Block II bus carried a 149-kilogram package consisting of a small hard lander with a 97-kilogram retrorocket that provided 22.6 kilonewtons of thrust. The hard lander, built by the Aeronutronic Division of the Ford Motor Company in Newport Beach, California, was a 64-centimeter diameter sphere with a mass of 43 kilograms. The exterior was composed of balsa wood designed to absorb the force of impact. Inside this impact limiter was a smaller 31-centimeter, 26-kilogram sphere that housed the lander’s systems. The primary instrument carried by the lander was a seismometer sensitive enough to detect the impact of a 2.3-kilogram meteorite on the opposite side of the Moon. The sensitive components of the seismometer were protected from the impact forces by a cushion of liquid heptane. Also included in the capsule was a 50-milliwatt L-band transmitter, six silver-cadmium batteries, and a temperature-sensitive voltage oscillator. The lander was designed to survive an impact of 67 meters per second.

The hard lander’s interior temperature was controlled by a capsule containing 1.7 kilograms of water. During the hot lunar day, the interior would heat up to 30° C, at which point the water would start to boil under the ambient conditions. The temperature would rise no further until all the water had boiled away. During the cold lunar night, the warmed water, along with the heat generated by the lander’s internal electronics, would keep the interior temperature above freezing. The battery-powered lander package had an expected 20 to 30-day lifetime on the lunar surface.

The 330-kilogram, 3.1-meter-tall Block II Ranger had additional modifications from its Block I predecessor. First, the battery was reduced in size to 11 kilograms, which provided one kilowatt-hour of reserve power. Another modification included the use of a 16-kilogram hydrazine-fueled course correction engine which generated 222 newtons of thrust to fine-tune Ranger’s aim as it approached the Moon. This engine could be fired for a maximum of 68 seconds, giving a total velocity change of 44 meters per second. Since any torques imparted during this engine’s operation could not be negated using the small attitude control jets, this engine was fitted with steering vanes at the exit nozzle.

The bus of the Block II Ranger also carried its own set of instruments. A radar altimeter provided ranging information for lander deployment as well as data on the lunar surface’s radar characteristics. A gamma ray spectrometer sensitive to the 0.1 to 2.6 MeV energy range was mounted on an extendable 1.8-meter boom. This would allow the characterization of gamma rays being emitted by the surface of the Moon allowing the concentration of key radioactive elements to be determined. The science package was rounded out by a slow-scan television camera which would return images during the final 40 minutes before impact with the lunar surface. The camera was fitted with a JPL-designed 1020-millimeter focal length lens which provided a 0.65° field of view in combination with the vidicon tube and supporting electronics manufactured by RCA. The image would be broken up into 200 scan lines (just 40% of the NTSC video standard of the day) and transmitted in analog form back to Earth in ten seconds. Following a three-second interval to erase the latent image from the camera’s vidicon plate (when other data could be transmitted), the camera would snap another image and begin transmission. Over 150 images were expected to be transmitted before the lander would ignite its retrorocket. For the Block II Ranger missions, the highest priority was given to the gamma ray spectrometer followed by the TV camera and the hard lander.

In order to minimize the chances of Earth organisms reaching the Moon (which was still a concern in some circles during these early days), the spacecraft components were sterilized first by baking them for 24 hours at 125° C and then all its parts were cleaned with alcohol before they were assembled. Finally, the entire spacecraft was saturated with ethylene oxide gas for 24 hours while in its launch faring.

 

The Mission Plan

There were many variables involved in choosing a proper launch window for Ranger. First, the length of the trip to the Moon was set to about 66 hours to maximize the payload while ensuring that Ranger would be in clear view of the Goldstone tracking antenna in California’s Mojave Desert— the most sensitive in NASA’s network of tracking stations — when it reached the Moon. Ranger also had to approach the Moon almost vertically at a precise speed because of the fixed velocity increment of the lander’s retrorocket. Because of the imaging requirements and the position of celestial references, the landing could only take place on the Moon’s visible face during a four- or five-day period centered on the Moon’s last quarter phase. Finally, the requirement that the hard lander’s antenna have Earth in view meant that it could not be placed more than 45° from the center of the Moon’s visible side. All of these constraints limited impact sites to near the lunar equator in the eastern part of the mare known as Oceanus Procellarum.

A typical mission sequence for the Block II Ranger started with the modified Atlas D rocket placing the Agena B upper stage and Ranger spacecraft into a parking orbit after a short burn from the Agena B. After a preprogrammed time delay, the Agena B would reignite to place the spacecraft on a path to the Moon. Once its job was completed, the Agena B would separate from the probe and fire small retrorockets to distance itself from the Ranger. About five minutes after separation and around 48 minutes after launch, Ranger would then unfold its solar panels and high-gain antenna to begin its search for its first attitude reference, the Sun. Once acquired, Ranger would switch from its battery to its solar panels for power. It would then begin a slow roll until its antenna locked on to Earth, its final reference point, about four hours after launch.

If its trajectory needed refining, Ranger would be commanded to make a single mid-course correction about 15 hours after launch at a distance of around 146,000 kilometers to ensure a lunar impact at the proper location and terminal velocity. During this time, the internal gyroscopes were used as an attitude reference as the spacecraft was pointed in the required direction. After the burn and cruise attitude had been reestablished, the relatively fragile gamma ray spectrometer boom would be deployed.

As Ranger approached the Moon, it would begin its terminal descent maneuver. The spacecraft would switch to its internal battery and turn so that its bottom was aligned with the Moon. After the high-gain antenna was once again pointed at Earth, the probe would begin to acquire television images starting about 32 minutes before impact at an altitude of 3,900 kilometers. Images would be taken every 13 seconds down to an altitude of 59 kilometers. Transmission of this last image, which was expected to reveal features as small as 3 meters across, would have been completed as the probe reached an altitude of only 24 kilometers.

Only 8.1 seconds before the bus crashed into the lunar surface at a speed of 2,900 meters per second, the radar altimeter would generate a fusing signal at an altitude of 21.4 kilometers. At that moment, bolt cutters would free the hard lander and retrorocket from the bus. A three-nozzle spin motor would fire, lifting the package 0.8 meters above the bus and imparting a spin of 300 RPM. The retrorocket would then fire, slowing the capsule to a virtual stop at a height of only 335 meters above the lunar surface. Explosive bolts would cut the clamp holding the lander to its retrorocket and the two would be separated by springs. The hard lander would then free fall to the surface with an impact speed of 45 meters per second, give or take 9 meters per second.

Protected from the force of impact by its balsa wood shell, the lander would roll to a stop. The capsule floating freely inside the shell on a layer of liquid Freon was made to be bottom heavy so that it would settle into a horizontal position. After twenty minutes, plugs are blown out, allowing the 225 milliliters of heptane protecting the seismometer and the Freon to evaporate into the lunar vacuum, thus fixing the capsule in place and allowing the seismometer to operate correctly. The package would then transmit its findings on lunar seismic activity for the next month. If it worked, the United States would have the first high-resolution pictures of the Moon as well as the first hard landing on its surface.

 

Preparing for the First Flight

Assembly of the first Block II Ranger spacecraft, designated P-34 by NASA, started in July 1961 at JPL. As testing of the spacecraft continued, NASA launched the first Block I prototype on August 23. Unfortunately, Ranger 1 was stranded in a low Earth orbit when its Agena 6001 upper stage (the first of the Agena B 6000-series stages built to support NASA launches) burned only briefly because of an overheated pressure switch circuit. Despite being stranded in a low Earth orbit with its 90-minute day-night cycle, Ranger 1 was able to provide vital engineering data before its attitude control system ran out of gas the day after launch vindicating the three-axis stabilized spacecraft design (see “The Prototype That Conquered the Solar System”).

On November 15, 1961, NASA accepted the P-34 spacecraft which was shipped cross country in a specially prepared, air-conditioned van. In the meantime, the second Block I spacecraft, Ranger 2, was launched from Cape Canaveral on November 18. The Agena 6002 upper stage once again failed in its parking orbit because of a malfunction in its roll gyro. Stranded in a quickly decaying orbit, no engineering tests of Ranger 2 were performed before it reentered Earth’s atmosphere six hours after launch. Obviously, much work remained to be done to improve the reliability of the 6000-series Agena B stage.

With the P-34 spacecraft arriving at the Cape on November 20, 1961, its launch date was set for January 1962. With the arrival fixed to take place during the few days around the Moon’s third-quarter phase, launch dates between January 22 and 27 would meet the mission’s requirements. Because of the need to support the upcoming launch of Mercury-Atlas 6 destined to send the first American into orbit, the launch date for P-34 was limited to January 22 to 26 with daily launch windows extending from 3:30 to 4:45 PM EST. By varying the launch azimuth and the time the Agena B coasted in its nominal 193-kilometer parking orbit, P-34 would have the opportunity to land just south of the lunar equator near the eastern rim of Oceanus Procellarum. But in order to reach its target, the Agena B would need to reach a velocity of 10,960 meters per second after its second burn with a tolerance of just ±7 meters per second. Unknown to the Ranger program participants who were wary of the Soviet Union reaching the Moon first, development of the much larger and more capable E-6 lunar lander by the Soviet OKB-1 design bureau was proceeding slowly and would not make its first launch attempt for another year giving the American team the first shot at landing on the Moon (see “The Mission of Luna 5”).

The Atlas 121D booster which would launch the mission arrived at Cape Canaveral on December 19, 1961 and was erected on the pad at Launch Complex 12 (LC-12) two days later. This was followed by the stacking of Agena 6003 which had arrived earlier in the month. After a series of tests and inspections, the encapsulated P-34 spacecraft was added to the stack on January 2, 1962. Following the completion of the Joint Flight Acceptance Test on January 5, the spacecraft was removed and moved to Hanger AE for its final preparations for launch.

In the meantime, checkout of equipment at the Deep Space Network to communicate with and receive data from P-34 was started on January 10 with operational readiness test completed nine days later. The P-34 spacecraft, with its pyrotechnics and flight battery now installed, was restacked with its launch vehicle on January 18 after finishing a preflight tear down, reassembly and testing. All was proceeding as planned for a January 22 launch until January 19 when the fuel tank on Atlas 121D was being filled with RP-1 grade kerosene. A leak was discovered in the aluminum membrane protecting the plastic foam insulation covering the fuel tank bulkhead which separated it from the LOX tank.

With the RP-1 pumped out of the fuel tank, project officials hurriedly met to determine the next steps. Normally, the rocket would be destacked and the Atlas returned to its hanger for repairs but, this action would push the launch date out four weeks into late February. Instead, USAF and Atlas contractors proposed a more daring approach to repair the bulkhead on the pad that would provide a chance to launch on January 26 – the last day of this month’s launch opportunity. When it was approved, engineers removed Atlas’ center, Rocketdyne LR105 sustainer engine while still on the pad to provide access to the fuel tank. A pair of wooden platforms and a ladder were assembled inside the propellant tank allowing technicians wearing oxygen packs and masks to remove the kerosene-soaked insulation from the bulkhead. This insulation layer was already excluded from the newer Atlas E/F ICBM design and did not need to be replaced for this flight. Working around the clock, the General Dynamics engineers were able to complete their repairs and get Atlas 121D into flight-ready condition in time for launch. Meanwhile, other preparations for the launch continued in parallel including saturating the payload inside its launch shroud with ethylene oxide gas for 11 hours during the night of January 23/24 to sterilize it.

 

The Ranger 3 Mission

The countdown, which started at 10:45 AM EST on January 26, 1962, proceeded without incident. Launch of Ranger 3 from LC-12 took place at 3:30 PM EST (20:30 GMT) at the beginning of the day’s launch window. As the Atlas-Agena B ascended, trouble was encountered after 49 seconds of flight when the pulse beacon in the Atlas’ radio command guidance system failed. Without a means of receiving and acknowledging guidance commands sent from ground computers, the Atlas had to rely on its much less precise autopilot to issue backup commands for the rest of the ascent. The first discrete command the radio guidance system was to supposed to give was to shut down and jettison the pair of LR89 booster engines at an altitude of about 58 kilometers some 101 kilometers downrange. When that command failed to be issued, the autopilot initiated the booster shutdown instead. As a result of the delay, the booster engines burned 1.5 seconds longer than planned. Because of the extra propellant consumed, the LR105 sustainer shutdown 7 seconds earlier than planned about 263 seconds after launch with the launch vehicle at an altitude of 145 kilometers about 628 kilometers downrange.

Despite the abbreviated burn of the Atlas, the launch vehicle was already traveling faster than desired. At this point, the airborne section of the guidance system was supposed to send commands to the Agena B to update the settings on its timers which controlled the burns of its Bell 8081 engine. The autopilot initiated separation of the Agena 6003 stage without the required updates. The Agena B jettisoned its launch shroud and coasted for 30 seconds before a timer commanded the ignition of its engine. Following this 2.5-minute first burn, Agena 6003 with Ranger 3 attached was traveling faster and higher than expected. The tracking station in Johannesburg, South Africa unexpectedly detected the Agena rising above the horizon five minutes early at 20:55 GMT. They had failed to receive a trajectory update because of a malfunction in communications equipment at the Cape. By this point, Agena 6003 had already completed its second burn after coasting for 7 to 8 minutes in its parking orbit. It was soon discovered that the Agena B had imparted excess velocity to Ranger 3 because of a programming error in the stage’s velocity meter which controls the length of the engine burn. Within an hour after launch, the tracking station in Woomera, Australia confirmed that Ranger 3 was placed into an incorrect trajectory.

Tracking revealed that the excess escape velocity would result in Ranger 3 reaching the orbit of the Moon 14 hours earlier than intended. Ranger 3 would pass about 39,000 kilometers from the Moon at 22:53 GMT on January 28 about 50 hours after launch. This miss distance far exceeded the 10,000-kilometer midcourse correction capability of Ranger’s propulsion system. While the lunar landing attempt was now impossible, Ranger 3 could still use its gamma ray spectrometer to study celestial sources while its TV camera took pictures of the Moon’s western hemisphere including portions of the far side which were not photographed by the Soviet Luna 3 mission in October 1959 (see “Luna 3: Shedding Light on the ‘Dark Side’ of the Moon”). In order to maximize the quality of the images returned by Ranger 3 and better time the flyby so that it could be observed by the 26-meter antenna at Goldstone, a course correction would need to be performed before the one nominally scheduled for 16 hours after launch.

Unfortunately, the tracking stations in South Africa and Australia did not have the equipment needed to uplink commands to Ranger 3 – that gear would not be installed until April to support the Ranger 4 mission. At 08:30 GMT on January 27, Goldstone finally acquired the signal from Ranger 3 and commanded its high gain antenna to deploy. The spacecraft dutifully responded and the telemetry returned showed that Ranger 3 had successfully locked onto its celestial references and had assumed the proper cruise attitude with its solar panels fully open and pointing at the Sun. At 10:00 GMT, three commands were sent to Ranger 3 in preparation for its planned 36.6 meters per second midcourse correction designed to move the spacecraft closer to the Moon and reach its target earlier. Ranger 3 changed its attitude as commanded and performed its midcourse correction at 10:27 GMT when the probe was 161,540 kilometers from the Earth traveling at 2,422 meters per second. After assuming its cruise attitude once again, the 1.8-meter boom carrying the gamma ray spectrometer was fully extended and started sending back data.

Post-correction tracking, however, showed that the maneuver did not have the intended effect. While the magnitude of the 36.8 meter per second change in velocity was close to the targeted value, an investigation quickly revealed that an undetected sign inversion in the commands sent to Ranger 3 caused the spacecraft to point its engine in the wrong direction. The spacecraft’s trajectory was pushed about 5,000 kilometers closer to the lunar surface but the closest approach would happen about a half an hour later than the pre-correction trajectory instead of earlier as had been planned. The error was added to the ever-growing list of the hard lessons being learned during this mission. Plans for flyby photography were revised to ensure reception at Goldstone. Despite the more distant flyby, the TV camera could secure images with a scale as good as about 3 kilometers per line.

At 16:52 GMT on January 28, Ranger 3 passed about 50,000 kilometers from the leading edge of the Moon. At 17:22 GMT, commands were sent to Ranger to begin its “terminal maneuver”. The spacecraft’s TV camera was turned on to warm up while the spacecraft made a pair of pitch and a single yaw maneuver to point its base towards the Moon. At 17:45 GMT, the lid covering the camera optics was opened and the omnidirectional antenna was swung out by 45° as preprogramed (while needed to deploy the lander, this action was not required for a flyby). The television camera started transmitting images through the high gain antenna at 17:52 GMT. Although the high gain antenna was required to turn 2° to lock onto the Earth to compensate for a small pitch maneuver that was performed, it did not stop and continued to slew. Commands from ground controllers went unanswered. With the high gain antenna 16° out of alignment and Earth visible in one of its side lobes, all that was received on the ground were noise-filled TV images showing the vidicon reticle marks illuminated by sunlight reflecting off of the spacecraft structure. The Moon was nowhere to be seen. It would be 3½ years before this region of the Moon finally would be imaged for the first time by the Soviet Zond 3 mission (see “The Soviet Zond Missions of 1963-65: Planetary Probe Test Flights“).

Subsequent commands sent to Ranger 3 went unacknowledged, apparently because of a failure in the probe’s central computer and sequencer which controlled its activities. With the spacecraft left slowly turning, it moved below the horizon as viewed from the Goldstone station at 18:41 GMT ending the disappointing encounter with the Moon. The unresponsive spacecraft made its closest pass of the lunar surface at 23:24:53 GMT on January 28 at an altitude of 35,134 kilometers and a velocity of 1,872 meters per second. With its sun sensors shut off as part of the terminal maneuver sequence, Ranger 3 could not properly reorient itself to point its solar panels at the Sun or receive any commands from the Earth. Ranger’s supply of attitude control gas was eventually exhausted at 16:00 GMT on January 31 at a range of 637,800 kilometers officially ending this problem-filled mission.

Ranger 3 subsequently entered a 0.984 by 1.163 AU solar orbit with an inclination of 0.40° to the ecliptic and a period of 406.4 days. While the project team acquired much important engineering data from the mission, the only scientific data returned by the wayward lunar probe were about 30 hours of background radiation readings from the gamma ray spectrometer. With yet another disappointing failure to investigate as well as corrective actions to be taken, more changes would have to be made to the Block II Ranger and its Atlas-Agena B launch vehicle to improve the chances of success for Ranger 4 scheduled for launch in April 1962 (see “Ranger 4: NASA’s First (Unintentional) Impact on the Moon“).

 

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Related Video

Here is some silent newsreel footage from 1962 showing the preparation of Ranger 3 for launch.

 

 

Here is a brief newsreel of the launch of Ranger 3.

 

 

Related Reading

For more articles, see the Ranger Program page.

 

General References

Evert Clark, “Ranger 3 Flight Stirs Reliability Question”, Aviation Week and Space Technology, Vol. 76, No. 6, pp. 30-32, February 5, 1962

Sarah A. Grassly, “Agena Flight History as of 31 December 1967 Volume 1”, SMEH-100, Air Force Systems Command Office of Information, June 1969

R. Cargill Hall, Lunar Impact: The NASA History of Project Ranger, Dover Publishing, 2010

W. L. Sjogren, “Ranger III Flight Path and Its Determination from Tracking Data”, JPL Technical Report no. 32-563, September 15, 1965

Paolo Ulivi with David M. Harland, Lunar Exploration: Human Pioneers and Robotic Surveyors, Springer-Praxis, 2004

“Lunar Surface Data is the Goal of Ranger 3”, Aviation Week and Space Technology, Vol. 76, No. 4, pp. 37-38, January 22, 1962