Ranger 6 was a lunar probe in the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

Ranger program, a series of robotic spacecraft of the early and mid-1960s to obtain the first close-up images of the Moon's surface. It was launched on January 30, 1964 and was designed to transmit high-resolution photographs of the lunar terrain during the final minutes of flight until impacting the surface. The spacecraft carried six television vidicon cameras - two wide-angle (channel F, cameras A and B) and four narrow-angle (channel P) - to accomplish these objectives. The cameras were arranged in two separate chains, or channels, each self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality

television Television, sometimes shortened to TV, is a telecommunication Media (communication), medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television tra ...

pictures. No other experiments were carried on the spacecraft. Due to a failure of the camera system, no images were returned.

Spacecraft design

Rangers 6, 7, 8, and 9 were called Block 3 versions of the Ranger spacecraft. The spacecraft consisted of a hexagonal aluminum frame base 1.5m across on which was mounted the propulsion and power units, topped by a truncated conical tower that held the TV cameras. Two

solar panel A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a pho ...

wings, each 739mm wide by 1537mm long, extended from opposite edges of the base with a full span of 4.6m, and a pointable high-gain dish antenna was hinge mounted at one of the corners of the base away from the solar panels. A cylindrical quasi omnidirectional antenna was seated on top of the conical tower. The overall height of the spacecraft was 3.6m. Propulsion for the mid-course trajectory correction was provided by a 224N thrust monopropellant

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazin ...

engine with four jet-vane vector control. Orientation and attitude control about three axes were enabled by twelve

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seve ...

gas jets coupled to a system of three gyros, four primary Sun sensors, two secondary Sun sensors, and an Earth sensor. Power was supplied by 9,792 silicon

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. Communications were through the quasi omnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60W TV channel F at 959.52MHz, a 60W TV channel P at 960.05MHz, and a 3W transponder channel 8 at 960.58MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into an RF signal for subsequent transmission through the spacecraft high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.

Mission profile

The

Cuban Missile Crisis The Cuban Missile Crisis, also known as the October Crisis (of 1962) ( es, Crisis de Octubre) in Cuba, the Caribbean Crisis () in Russia, or the Missile Scare, was a 35-day (16 October – 20 November 1962) confrontation between the Unite ...

had momentarily diverted attention from the failure of Ranger 5, but that mission forced a wholesale review of the entire Ranger program. Numerous theories were put forward about the cause of the failures, including poor management at JPL, overly-ambitious spacecraft designs that were unworkable and unreliable with contemporary technology, and some lesser reasons such as heat sterilization of the probes. NASA established a Ranger Board of Inquiry on October 29, 1962, headed by

Albert J. Kelley Albert Joseph Kelley Jr. (27 July 1924 – 8 December 2004) was a United States Navy officer and guidance systems engineer who worked at NASA from 1960 to 1967, supervising electronics research for the Apollo program. He later served as the D ...

, with the mission of establishing by November 30 the reasons for the continued program failures. The board's findings included the verdict that the Ranger design was "more complicated than necessary" for a lunar mission and also required a very high degree of engineering and workmanship, neither of which were being delivered. They also concluded that heat sterilization was damaging to the delicate spacecraft systems and should be abandoned at once. They also found that JPL's handling of the program was poor, the spacecraft lacked redundant systems in the event of a malfunction, NASA's deep-space tracking network crews were not trained adequately and had deficiencies in their equipment, and finally, the Atlas-Agena booster's reliability was poor, having malfunctioned on eight Air Force and NASA launches as November 1962 ended. If the Thor-Agena was also counted in, there had been a total of nine times that an Agena B stage had malfunctioned in flight. The board's recommendations included improving the management of projects, abandoning heat sterilization and testing of components designed for future planetary missions on Ranger, outsourcing assembly of the probes to a subcontractor, and excluding JPL from involvement in procurement and launching of the Atlas-Agena. Moreover, it suggested that NASA needed to improve their prelaunch testing and preparation of launch vehicles. The Block III spacecraft would be stripped down to a minimum of instrumentation with the eight scientific instruments on Rangers 3-5 removed so that more space could be devoted to redundant systems hardware. This caused some protests from the

scientific community The scientific community is a diverse network of interacting scientists. It includes many " sub-communities" working on particular scientific fields, and within particular institutions; interdisciplinary and cross-institutional activities are als ...

that the gamma-ray and other measurements were far more valuable than simply returning photography of the Moon. Jet Propulsion Laboratory began more thorough testing of Ranger components and the second review board was put to work evaluating the reliability of the

Atlas-Agena The Atlas-Agena was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was launched 109 times between 1960 and 1978. It was used to launch the first five Mariner uncrewe ...

. The booster problems would prove a particularly vexing one to solve because the U.S. Air Force, not

, was in charge of Atlas-Agena. Although NASA had hoped to launch planetary probes on

Centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as bein ...

, which was entirely under their control, that program was delayed by serious technical issues and would not be flight-ready for a long time. Having to share the booster with the U.S. Air Force and its Department of Defense missions on the West Coast created repeated mixups, delays, and technical problems. Therefore, it was recommended that NASA be given complete oversight in the procurement and launch of Atlas-Agena without the Air Force's involvement. Ranger 6 lift off KSC-64PC-0002

One of the important parts of the Ranger program was monitoring all Atlas and Thor-Agena launches to check for failures that could directly affect it. This job had been assigned to the

Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama ( Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's first ...

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, but was instead moved to the Lewis Research Center (LRC) in Cleveland, Ohio.

LRC LRC may refer to: Organizations Academic * La Roche College, a Catholic college in Pennsylvania * Lenoir–Rhyne College, now Lenoir–Rhyne University in North Carolina * Learning resource center, a term for a school library * Learning Resource ...

sent additional personnel to the Convair assembly plant in

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States ...

to monitor the construction of Atlas vehicles. The review board focused on the malfunctions plaguing Atlas-Agena, in particular, the General Electric guidance system, both the Mod III-G variant used on East Coast Atlas Agenas and the Mod II-A used on West Coast vehicles, which had malfunctioned repeatedly. They recommended putting forward more detailed and stringent requirements for testing Atlas vehicles and making sure the guidance package could withstand in-flight vibration levels along with improved fabrication of wiring harnesses. Also, it was recommended that Convair establish one standardized booster configuration for all U.S. Air Force and NASA launches instead of custom modifications for each mission, replacing hardware with known design flaws with better substitutes, and improved testing of everything. Since the Air Force was in charge of Atlas-Agena, it followed that all these changes required their approval. Finally, NASA for the first time would be given complete oversight of all its space launches. Air Force involvement in procuring, preparing, and flying launch vehicles, as well as drafting postflight mission reports for NASA missions, was to end, a step that would greatly streamline and improve the efficiency of things. Problems continued, this time with getting the TV cameras for Ranger 6 in working order. The camera tubes, supplied by

Radio Corporation of America The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westin ...

, were of variable quality and it took some time to find one that matched JPL's standards. During testing of Atlas guidance systems at

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...

, it was found that gold coating on diodes was flaking off and causing electrical shorts. Even worse, Ranger 6 had hundreds of the same diodes. This problem had easily eluded testing; moreover, ground tests could not simulate a "

zero gravity Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...

" environment in space where the

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

flakes would float around and form a short between the legs of the diode. In the end, there was no choice except to replace every last one of the several hundred diodes inside Ranger 6's circuitry. In April 1963, the

United States Congress The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washi ...

also decided to cut funding to the Ranger program by nearly 50% on the grounds that "no success had been achieved with any of the missions to date". This meant that plans for Ranger probes up to 13 were cancelled. Only Rangers 6-9 would be flown and they would carry little more than a TV camera. NASA FACTS Volume 2 number 6 PROJECT RANGER image 11

NASA FACTS Volume 2 number 6 PROJECT RANGER image 11

One of Program Ranger's goals was looking for potential landing sites for manned lunar missions. At this point, it was not clear exactly what the Moon's surface was like and widespread fears existed of there being bottomless quicksand that would swallow up spacecraft and astronauts. Since the basic design of the

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

lunar module had already been finalized by 1963, landing on the Moon would only "confirm or deny that design". JPL decided to go for an impact point near the Moon's equator, in the Sea of Tranquility, partially because it was considered a prime Apollo landing spot, and also because the target had to match lighting conditions during the time of launch in January–February. Ranger 6 and its launch vehicle (Atlas 199D and Agena 6008) arrived at Cape Canaveral in mid-December and, with the

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still mourning

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Kennedy's assassination the previous month, began preflight tests. Liftoff took place at 10:49 AM EST on January 30, 1964. The Atlas lifted smoothly into an overcast sky and disappeared from view. All went well during the boost phase and the launch vehicle's performance was excellent, indicating the hard-fought effort to improve booster reliability. Shortly after Atlas BECO and staging, an ominous development occurred when telemetry indicated that the

telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", and ' ...

for the TV camera on Ranger 6 had turned itself on and then back off again 67 seconds later. Telemetry data showed everything else appears to function normally and tensions at JPL eased. The Agena placed the probe into a parking orbit and then fired for translunar injection 25 minutes after launch. After separation of Ranger 6, the solar panels and high-gain antenna were extended and all appeared normal. The launch vehicle had placed the probe on an accurate enough flight path that only a short midcourse correction burn would be required. However, the activation of the TV camera telemetry during launch remained a cause for concern. JPL technicians wanted to turn the camera on to verify its operability, however, they were running the risk of not being able to turn it off again if an electrical short had indeed occurred somewhere. Since the camera had its own batteries and did not use the probe's main power bus, they would be depleted before it could get to the Moon and eliminate any chance of returning pictures. They decided that it was not worth compromising the mission and the camera would not be touched until descent to the Moon began. Early on the morning of January 31, the command was sent to fire the midcourse correction engine, which performed flawlessly and set the probe on an impact course with the Sea of Tranquility. On February 2, JPL technicians prepared for the final phase of the mission. Ranger 6 began its descent and trajectory calculations determined that impact would occur close to the intended area. With the probe's angle suitable for taking images, the order was given to turn on the camera with 13 minutes and 10 seconds until impact. After an initial warm-up phase, the command to power them on was sent. However, no imagery or any sign of camera operation appeared. Two more commands were sent to turn on the camera, but still, nothing happened even though all other systems continued to operate normally. At 01:24 AM, impact with the Moon occurred and telemetry transmission from Ranger 6 ceased. The mission was over and for the 12th time in a row, a U.S. attempt to send a probe to the Moon had malfunctioned. Even worse, it had occurred one week before NASA officials were planning to announce to Congress their projected US$5.3 billion budget for FY 1965, a good deal of it related to manned and unmanned lunar missions.

attempted to put a positive spin on the mission by noting that, aside from the cameras, Ranger 6 and its Atlas-Agena booster had both functioned "extremely well". Ranger 6 was launched into an Earth

parking orbit A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory. The alternative to a parking orbit is ''di ...

and injected on a lunar trajectory by a second Agena burn. The midcourse trajectory correction was accomplished early in the flight by ground control. On February 2, 1964, 65.5 hours after launch, Ranger 6 impacted the Moon on the eastern edge of ''Mare Tranquillitatis'' ( Sea of Tranquility in English). The orientation of the spacecraft to the surface during descent was correct, but no video signal was received and no camera data obtained. A review board determined the most likely cause of failure was due to an arc-over in the TV power system when it inadvertently turned on for 67 seconds approximately 2 minutes after launch during the period of booster-engine separation. This fourth American attempt at lunar impact was the closest success. The spacecraft, the first Block III type vehicle with a suite of six TV cameras, was sterilized to avoid contaminating the lunar surface. The series would also serve as a test bed for future interplanetary spacecraft by deploying systems (such as solar panels) that could be used for more ambitious missions. The Block III spacecraft carried a 173-kilogram TV unit (replacing the impact capsule carried on the Block II Ranger spacecraft). The six cameras included two full-scan and four partial-scan cameras. Ranger 6 flew to

the Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

successfully and impacted precisely on schedule at 09:24:32 GMT on February 2. Unfortunately, the power supply for the TV camera package had short-circuited three days previously during Atlas booster separation and left the system inoperable. The cameras were to have transmitted high-resolution photos of the lunar approach from 1448 kilometers to 6.4 kilometers range in support of Project Apollo. Impact coordinates were 9°24' north latitude and 21°30' east longitude.

Footnotes

References

External links

Lunar impact: A history of Project Ranger (PDF) 1977
{{Use American English, date=January 2014 6 Spacecraft launched in 1964 Spacecraft that impacted the Moon Impactor spacecraft 1964 on the Moon

Spacecraft design

Mission profile

Footnotes

See also

References

External links