Chapter 2 of 5

Six Rangers before me

The Ranger 6 television failure and the changes made before Ranger 7

Told in Ranger 7’s imagined voice · the events are real · source

Guericke Crater as seen by Ranger 7
Ranger 7Before me, six Rangers had tried. None of them brought back the pictures scientists needed.
NASA/JPL
01Rangers 1 and 2 never left Earth orbit. Rangers 3 and 5 missed the Moon. Ranger 4 hit the far side but could not return data. Ranger 6 reached the Moon, but its television system failed.
Ranger 6's cameras were dead before it arrived.
02A short circuit disabled the television system during the flight. The spacecraft still hit the Moon on target, but it returned no pictures. The exact cause of the failure was never definitively established.
Engineers stand with Ranger 7 on Dec.
Ranger 7Engineers could not agree on one exact cause, so they made several safeguards.
NASA/JPL-Caltech
03During Ranger 6's ascent, its television system had switched on for 67 seconds in the thin upper atmosphere. Investigators found that high voltage could arc there. They locked out the TV turn-on until separation and protected the command wiring.
I would have to show that the changes worked.
04Ranger 7 carried the same kind of six-camera system, but with fixes meant to prevent an early turn-on. The team had one more chance to make the Ranger camera experiment succeed.

The big idea

When a failure has more than one possible cause, engineers may fix several weak points at once and then test the whole system in flight.

Think about it

Why might a team add several safeguards when it cannot prove which one caused a failure?

Fact file

Ranger 6 mission
Launched 30 January 1964 · impacted 2 February 1964
Ranger 6 reached the Moon on target. Its television system returned no pictures.
Source ↗
Television turn-on
67 seconds during ascent
Telemetry showed the TV system switching on about two minutes after launch, then switching off again. Investigators focused on that period.
Source ↗
Cause
Never definitively established
JPL's board found that arcing in the thin upper atmosphere damaged the high-voltage supplies, but could not agree on the precise trigger. It recommended several safeguards rather than one single fix.
Source ↗
Earlier Ranger outcomes
Block I: 2 Earth-orbit failures · Block II: 3 lunar failures · Ranger 6: no pictures
NASA describes Ranger 7 as the first success after 13 failed U.S. Moon attempts. The Ranger program itself had different blocks and different failure modes.
Source ↗

In this chapter: Television power supply, command circuitry and the Agena umbilical connector

Sources: Main record · NASA History · Lunar Impact (NASA SP-4210) · NSSDCA · Ranger 7 television experiment · NASA History · 60 Years Ago: Ranger 7 Photographs the Moon

Machine illustration: AI-made. Photos: NASA Image and Video Library, credited on each picture.

Chapter 2 of 5

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