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The Ranger Space Probes, Crashing into the Moon

The launch of Atlas-Agena rocket booster

The launch of Atlas-Agena rocket booster

Purpose of the Ranger Spacecraft

On January 26th, 1962 the unmanned Ranger 3 spacecraft was launched. About two days later, it passed by the moon at a distance of 22,000 miles. This luner flyby was closer than the earlier Pioneer 4 flyby in 1959 but its mission was a failure. Two years later, on July 28 the Ranger 7 spacecraft left the earth and about three days later it impacted on the moon’s surface. This mission was a complete success. Yes, the Ranger spacecraft was unique, its purpose: crash into the moon.

However, there was more to it than simply hitting the moon. The purpose of the spacecraft was to provide the first detailed images of the lunar surface. They carried six cameras with different field of views and different exposure times and scan rates. The missions were broken up into three different design configurations called blocks.

The Launch Vehicle

The booster rocket used for the Ranger spacecraft was the Atlas-Agena system consisting of the Atlas missile (first US intercontinental ballistic missile) and the Agena upper second stage. Reliability problems with the Agena caused the initial failures in earlier Ranger spacecraft. Most of the problems stemed from poor quality control and was complicated by too many variants since the Agena upper stage was used by both NASA and the Department of Defense.

The Rangers used the Agena B version which had restart capability. The spacecraft was launched initially into earth orbit and then after the Agena restart, the spacecraft was put into a lunar trajectory.

Block 1 Ranger Spacecraft

Block 1 Ranger Spacecraft

Block 1 Missions

  • Ranger 1: Launched on August 23, 1961, earth orbit failure
  • Ranger 2: Launched on November 18, 1961, earth orbit failure

Both Rangers 1 and 2 were intended to test the spacecraft and the Atlas-Agena booster so their only purpose was earth orbit, no lunar attempt was planned. However, failure of the Agena second stage on both launches stranded both spacecraft in low orbit where they eventually reentered the atmosphere and burned up. Ranger 1 lasted four days (111 orbits) while Ranger 2 only lasted a day (19 orbits).

Block 2 Ranger Spacecraft

Block 2 Ranger Spacecraft

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Block 2 Missions

  • Ranger 3: Launched on January 26, 1962, lunar failure, missed the Moon by 22.000 miles (35,000 km)
  • Ranger 4: Launched on April 23, 1962, lunar failure, impacted on the moon but failure of the central computer shut the spacecraft down with absolutely no function (solar panels, cameras, instruments).
  • Ranger 5: Launched on October 18, 1962, lunar failure, missed the Moon by 450 miles (725 km)

In the case of the block 2 missions there was quite a bit of frustration. NASA had succeeded in correcting problems with the Atlas-Agena booster by improving quality and reducing the number of variants, but now this was overshadowed by complications with the Ranger spacecraft. All three probes failed. The block 2 spacecraft were designed with a small capsule that would separate from the main body and make a hard landing on the surface. Surprisingly, to insure a successful landing, the capsule was encased in balsa wood. Unfortunately, failure of these missions did not allow these capsules to make it to the surface with the exception of possibly the one on Ranger 4 but the impact was on the far side of the moon. The small capsule carried a battery and a seismometer.

Block 3 Ranger Spacecraft

Block 3 Ranger Spacecraft

Block 3 Missions

  • Ranger 6: Launched on January 30, 1964, impacted on the moon but failure of the TV camera produced no visual data.
  • Ranger 7: Launched on July 28, 1964, mission success, impacted at Mare Cognitum
  • Ranger 8: Launched on February 17, 1965, mission success, impacted at the Sea of Tranquility, 43 miles (70 km) from the Apollo 11 landing site
  • Ranger 9: Launched on March 21, 1965, mission success, impacted at Alphonsus crater

The success of the block 3 program was a result of a different approach to the design of the Ranger spacecraft. Gone was the over complicated instrument rich approach, replaced with a more simple design with redundancy built in. Many scientists did not agree that instruments were being removed, but this new design path assured the success of the remainder Ranger missions.

Ranger Spacecraft Video (Up to the Point of Impact)

Let's Eat Peanuts

It is interesting how a superstition can start among engineers and scientists who usually don’t believe in anything that they can’t see or touch, or in anything that doesn’t conform to the scientific method. However, after the success of Ranger 7, it was observed that somone in mission control was eating peanuts. From then on, for all unmanned spaceflights, the jar of peanuts became a permanent fixture as an interesting way to insure the success of the mission.

Paving the Way to the Future

The Ranger Space Program was the first infant step to the Moon. It would pave the way for two other unmanned spacecraft programs that would follow in just a few years: The Lunar Orbiters and the Surveyor Landers. Both of these programs would scout for landing sites and set the stage for the manned moon landings.


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