Ranger 5
Ranger 5 lost power and missed the Moon.
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Ranger 5 was a spacecraft of the Ranger program intended to transmit lunar surface images during the final minutes before impact, deploy a seismometer capsule, and gather gamma-ray and radar data. It lost power due to an unknown malfunction and passed within 725 km of the Moon.
Spacecraft design
Ranger 5 was a Block II Ranger spacecraft, similar to Ranger 3 and Ranger 4. The vehicle stood 3.1 m high and comprised a lunar capsule enclosed in a balsawood impact-limiter 65 cm in diameter, a mono-propellant mid-course motor, a retrorocket producing 5080 lbf of thrust, and a gold- and chrome-plated hexagonal base 1.5 m across. A large high-gain dish antenna was attached to the base, and two wing-like solar panels spanning 5.2 m deployed early in flight.
Power came from 8680 solar cells that charged an 11.5 kg, 1 kWh capacity silver-zinc launching and backup battery. Attitude control used six Sun sensors, one Earth sensor, gyroscopes, and pitch and roll cold nitrogen gas jets. The telemetry system included two 960 MHz transmitters (one at 3 W, the other at 50 mW), the high-gain antenna, and an omnidirectional antenna. Thermal control was provided by white paint, gold and chrome plating, and a silvered plastic sheet around the retrorocket.
The experimental payload comprised a vidicon television camera (one frame in 10 seconds), a gamma-ray spectrometer on a 1.8 m boom, a radar altimeter, and a seismometer to be rough-landed on the Moon. The seismometer, amplifier, 50 mW transmitter, voltage control, turnstile antenna, and six silver-cadmium batteries (capable of 30 days of operation) were encased in the lunar capsule, designed to impact at 130 to 160 km/h. The instrument package floated in a layer of freon inside the balsawood sphere.
Mission
Ranger 5 was originally scheduled for launch in June 1962, but NASA decided to fly the Mariner Venus probes first, derived from Block I Ranger, to allow more time to resolve spacecraft problems. After Mariner 1 ended its mission in the Atlantic Ocean, the agency faced increased scrutiny from Congress over its inability to achieve success with planetary probes. Republican Congressman James Fulton confronted NASA Director of the Office of Programs J.J. Wyatt, noting that Mariner 1 had cost $14 million and that there was no excuse for continued failures.
By the end of July 1962, there had been 12 planetary probe attempts since 1958, and only Pioneer 4 and Pioneer 5 had accomplished all mission goals. The successful launch of Mariner 2 on August 27 temporarily blunted criticism of NASA and the Jet Propulsion Laboratory and appeared to verify the soundness of the Ranger design. JPL engineers were still investigating the computer failure on Ranger 4, which had occurred while the probe was out of tracking range.
Telemetry records suggested the failure happened during separation from the Agena, when the electrical interface was disconnected and Ranger 4 switched to internal power, likely due to a short circuit from loose metal coatings contacting pins on the power umbilical. Modifications to Ranger 5 included a backup timer to maintain telemetry if the main computer failed, an additional nitrogen bottle for the attitude control system, an extra pyrotechnic igniter for the midcourse correction engine, and additional diodes and fuses on electrical lines to prevent shorts.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Ranger 5 (CC BY-SA 4.0).
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