Chapter 3 of 8

Another way to steer

First-EVA front steering fault and rear-steering operation on 31 July 1971

Told in Apollo 15 Rover’s imagined voice · the events are real · source

CAPE CANAVERAL, Fla.
Apollo 15 RoverMy front wheels would not steer. My rear wheels still could.
NASA
01The vehicle had separate front and rear steering systems. After troubleshooting, the crew and Mission Control chose to make the first excursion with rear-wheel steering. One failed function did not remove every way to manoeuvre.
Scott's hand controller still commanded the drive, turns and brakes.
02A T-shaped controller between the seats operated the vehicle. The astronauts drove it themselves. This was not a robotic rover taking commands one metre at a time from Earth.
S71-39867 (June 1971) --- Astronauts David R.
Apollo 15 RoverMoving farther away also meant keeping track of the way back.
NASA/JSC
03A directional gyro and wheel-distance measurements fed the navigation computer. A Sun-shadow device supplied a manual heading check. This system tracked the direction and distance back to Falcon; it was not GPS.
We set off toward Elbow Crater with a working way to turn—and a way home.
04Scott and Irwin described the geology during the first traverse. At stops, they aimed the high-gain antenna toward Earth so scientists and controllers could follow the television pictures. The wheels and the radio link were helping the same investigation.

The big idea

Redundant functions and navigation can preserve useful exploration after a fault. Getting there and returning safely are parts of the same plan.

Think about it

Why is a working backup steering system useful only if the crew also knows how to get back?

Fact file

Steering response
Rear steering for EVA 1
The front system was unavailable; a cause is not invented.
Source ↗

In this chapter: Separate front/rear steering motors, hand controller, gyro and odometer

Sources: Main record · The Apollo Lunar Roving Vehicle · NSSDCA

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

Chapter 3 of 8

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