Ranger 4, the first U.S. spacecraft to reach another celestial body

The Atlas-Agena-4 boosted the Ranger IV spacecraft for the first U.S. lunar impact.
| Photo Credit: NASA

They say that when you reflect on the pain of failures, you make progress. It might just be a more polished way of saying “failures are the stepping stones of success,” but it does actually work in every walk of life. And that includes space missions too.

In the 1950s and 1960s, when the Space Age was still quite nascent, there were a number of failures. Each of these failures did provide considerable learning that eventually led to other successes.

While most failures, however, are often forgotten, it isn’t quite the case with Ranger 4. Despite the fact that it did not perform any of its planned operations, it is remembered now as the first U.S. spacecraft to reach another celestial body – the moon in this case.

Aim: To transmit photos

Part of the Ranger series of missions, Ranger 4 was designed with the objective of transmitting photos during the final stages of descent, in addition to rough-landing a capsule carrying a seismometer and other instruments. A Block II Ranger spacecraft almost identical to Ranger 3, the basic vehicle was 3.1 m high. Power was to be generated by solar cells contained in the two wing-like solar panels at the base of the spacecraft.

A solid-state computer and sequencers along with an Earth-controlled command system provided control over the spacecraft. It had many scientific instruments, including a vidicon television camera, a gamma-ray spectrometer, a radar altimeter, and a single-axis seismometer. While pictures of the lunar surface were to be transmitted to Earth stations during the last 10 minutes before impact, the lunar capsule transmitter had enough juice in it for 30 days.

Timer stops

Launched on April 23, 1962 from Cape Canaveral, NASA’s Ranger 4 was designed to be boosted towards the moon by an Atlas/Agena launch system and undergo one mid-course correction before impacting on the lunar surface. As it panned out, a power failure in the central computer and sequencer meant that the spacecraft’s master clock or timer stopped. As a result, the vehicle was prevented from doing any of its planned operations, including opening its solar panels, and the instrumentation ceased operations after about 10 hours of flight.

Without any course corrections, Ranger 4 drifted aimlessly. The spacecraft, however, could be tracked by the battery-powered transmitters in the lunar landing capsule. After 64 hours of flight, on April 26, Ranger 4 impacted the far side of the moon at a velocity of about 9.600 km/hour.

Even though Ranger 4 was a failure and did not fulfil its primary objective, the fact that it impacted the lunar surface meant that it became the first U.S. spacecraft to reach another celestial body. The fate of Ranger 4, in fact, was the same of the first six flights of the Ranger programme, all of which ended as failures.

The Ranger programme – a series of uncrewed space missions with the aim of getting close-up images of the moon – had nine missions in total. Ranger 7 was the first to taste success when it returned images of the moon in July 1964. It was followed by two more successful missions in the programme. Ranger 4, though, was able to achieve a first despite being a failure.