Ranger 3 was the first of the Block II Ranger designs.
The basic vehicle was 3.1 m high and consisted of a lunar capsule covered with a balsa wood impact-limiter, 650 mm in diameter, a mono-propellant mid-course motor, a retrorocket with a thrust of 5080 pounds force (22.6 kN), and a gold- and chrome-plated hexagonal base 1.5 m in diameter.
A large high-gain dish antenna was attached to the base.
Two wing-like solar panels (5.2 m across) were attached to the base and deployed early in the flight.
Power was generated by 8680 solar cells contained in the solar panels which charged an 11.5 kg 1 kW·h capacity AgZn launching and backup battery.
Spacecraft control was provided by a solid-state computer and sequencer and an earth-controlled command system.
Attitude control was provided by Sun and Earth sensors, gyroscopes, and pitch and roll jets.
The telemetry system aboard the spacecraft consisted of two 960 MHz transmitters, one at 3 W power output and the other at 50 mW power output, the high-gain antenna, and an omnidirectional antenna.
White paint, gold and chrome plating, and a silvered plastic sheet encasing the retrorocket furnished thermal control.

During prelaunch preparations for Ranger 1, the spacecraft's timer had accidentally been started which led to the deployment of the solar panels inside the payload shroud.
It was decided that ground testing of the onboard instruments would not be done on the Block II spacecraft because they had a functional midcourse correction engine and if a similar incident happened with them, the squibs and pyrotechnics used to deploy the solar panels could inadvertently ignite the propellants in the onboard engine, which could result in the explosion of the spacecraft on the pad and possibly take the entire launch vehicle with it.
JPL officials announced that factory testing of the Ranger's systems was sufficient to root out any problems and any hardware which failed to pass the tests was not fit to fly.

The experimental apparatus included: (1) a vidicon television camera, which employed a scan mechanism that yielded one complete frame in 10 s; (2) a gamma-ray spectrometer mounted on a 1.8 m boom; (3) a radar altimeter; and (4) a seismometer to be rough-landed on the lunar surface.
The seismometer (code-named "Tonto") was encased in the lunar capsule along with an amplifier, a 50 mW transmitter, voltage control, a turnstile antenna, and six silver-cadmium batteries capable of operating the lunar capsule transmitter for 30 days, all designed to land on the Moon at 130 to 160 km/h (80 to 100 mph).
The radar altimeter would be used for reflectivity studies, but was also designed to initiate capsule separation and ignite the retrorocket.
Ranger 3 was the first of the Block II Ranger designs. The basic vehicle was 3.1 m high and consisted of a lunar capsule covered with a balsa wood impact-limiter, 650 mm in diameter, a mono-propellant mid-course motor, a retrorocket with a thrust of 5080 pounds force (22.6 kN), and a gold- and chrome-plated hexagonal base 1.5 m in diameter. A large high-gain dish antenna was attached to the base. Two wing-like solar panels (5.2 m across) were attached to the base and deployed early in the flight. Power was generated by 8680 solar cells contained in the solar panels which charged an 11.5 kg 1 kW·h capacity AgZn launching and backup battery. Spacecraft control was provided by a solid-state computer and sequencer and an earth-controlled command system. Attitude control was provided by Sun and Earth sensors, gyroscopes, and pitch and roll jets. The telemetry system aboard the spacecraft consisted of two 960 MHz transmitters, one at 3 W power output and the other at 50 mW power output, the high-gain antenna, and an omnidirectional antenna. White paint, gold and chrome plating, and a silvered plastic sheet encasing the retrorocket furnished thermal control.
During prelaunch preparations for Ranger 1, the spacecraft's timer had accidentally been started which led to the deployment of the solar panels inside the payload shroud. It was decided that ground testing of the onboard instruments would not be done on the Block II spacecraft because they had a functional midcourse correction engine and if a similar incident happened with them, the squibs and pyrotechnics used to deploy the solar panels could inadvertently ignite the propellants in the onboard engine, which could result in the explosion of the spacecraft on the pad and possibly take the entire launch vehicle with it. JPL officials announced that factory testing of the Ranger's systems was sufficient to root out any problems and any hardware which failed to pass the tests was not fit to fly.
The experimental apparatus included: (1) a vidicon television camera, which employed a scan mechanism that yielded one complete frame in 10 s; (2) a gamma-ray spectrometer mounted on a 1.8 m boom; (3) a radar altimeter; and (4) a seismometer to be rough-landed on the lunar surface. The seismometer (code-named "Tonto") was encased in the lunar capsule along with an amplifier, a 50 mW transmitter, voltage control, a turnstile antenna, and six silver-cadmium batteries capable of operating the lunar capsule transmitter for 30 days, all designed to land on the Moon at 130 to 160 km/h (80 to 100 mph). The radar altimeter would be used for reflectivity studies, but was also designed to initiate capsule separation and ignite the retrorocket.
Ranger 3