The sign accompanying the Gemini mockup. It reads
Gemini Engineering Development Fixture
In preparation for and during the flights of the Gemini spacecraft, the
physical characteristics of engineering designs were reproduced in full scale
to create this mock-up, enabling the Gemini designers to see, in full
dimension, equipment relationships and system integration and to develop check
out, launch, and operational procedures.
Mission advances required each succeeding spacecraft to be modified for new
mission objectives. The new designs and equipment were first installed in this
mock-up to ensure that the new systems, circuits, and instrumentation did not
interfere with those existing.
This crew station was used by the Gemini astronauts to practice stowing all
crew items, such as food, cameras, etc., as well as planning the location of
new switches and instruments for their missions.
Full scale engineering mock-ups, often called "iron birds", are built for every
major aircraft, spacecraft, or missile and are an essential engineering tool
for the designers of McDonnell Douglas air and space products.