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Overall walk-around of the observation window.

Picture 1 of 13.

The Project Mercury Familiarization Manual notes that the observation window was located above the main instrument panel and consisted of an inner and an outer assembly. The inner window assembly was made up of three glass panes sealed in a titanium frame and attached to the cabin wall. The panes were independently sealed to provide a pressure seal between the panes. The outer window assembly consisted of a glass pane sealed in a titanium frame, attached to the capsule outer skin. The outer window assembly was sealed separately from the inner window assembly, to provide a complete seal. The outer window conformed to the curvature of the capsule conical section.

Both windows were trapezoidal. The outer window was 21.000" long, with the forward end measuring 7.511" and the aft end measuring 11.254" (they were really serious about measuring the size of the windows!). The inner window was 12.950" long, with the forward end measuring 7.300" and the aft end measuring 9.490".

The glare on the outer window makes it difficult to see the inner window.

Depending upon the angle from which I photographed the windows, it could look especially long or especially squat.

The initial versions of the spacecraft (the unmanned missions and Freedom 7, the first manned mission) had only a round porthole window at this location.