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I noticed that the majority of the toggle switches in the Mercury capsules move in a left-to-right manner.

This seems unusual to me, since Gemini, Apollo and the Shuttle all predominantly use up-down switches, and even a quick google of civilian and some military aircraft control panels show very few side-to-side switches.

Does anyone know the reasoning behind this design decision in the Mercury capsules?

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    $\begingroup$ The mercury capsule was extremely cramped, it may be a side to side motion made more sense with the orientation of the astronaut's arms. $\endgroup$ – GdD May 22 '19 at 12:56
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    $\begingroup$ @DrSheldon I believe the term Gusmobile was used on Gemini. Astronauts have been involved in the design of all the spacecraft. They generally tended to prefer aviation norms, even insisted on it in some cases, since they were test pilots before astronauts, so the side-to-side switch placement on just Mercury seems highly unusual to me. Even the X-15 had vertical switches $\endgroup$ – Innovine May 22 '19 at 12:56
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    $\begingroup$ In this picture of Shepard's control panel, the switches on the left are vertical, and the switches on the center (except for one) and right are horizontal. ???? Now I'm more puzzled. Good question. airandspace.si.edu/sites/default/files/styles/slideshow_xlg/… $\endgroup$ – Organic Marble May 22 '19 at 13:13
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    $\begingroup$ BTW, to the best of my knowledge, there was one (1) horizontal switch in the shuttle. It selected between the port and starboard robot arms (the starboard one was never flown). So if you flipped it to STBD, all it did was confuse the flight controllers. Its layout made sense because you switched it to the side where the arm you wanted to work with was mounted. Here's a picture of the switch from a simulator: imgur.com/a/m6jpbin $\endgroup$ – Organic Marble May 23 '19 at 22:18
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    $\begingroup$ Yes, they were looking out the aft windows flying the robot arm over the payload bay. $\endgroup$ – Organic Marble Aug 31 '19 at 12:18
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It MAY have been a space saving solution for that part of the panel.

There are 8 switches on MA-6 Friendship 7 vertically aligned in one column on the right of the main panel.

Switches orientated sideways will allow more switches in a vertical arrangement, as you can see in the recreation below (which is still missing many switches of other types...)

enter image description here

As the astronauts joked about the tightness of space in the capsules, “you don't get in it, you put it on.”

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This makes it pretty clear that they ended up where they were because John Glenn and Wally Schirra, went to the factory, suited up and experimented with things until they were happy.

While John Glenn and Walter Schirra studied the interrelations of the pressurized suit and the cockpit layout,McDonnell design engineers rearranged the Mercury control panel to place all controls in a U-shaped pattern around either side and below the instruments. When an astronaut's suit was inflated, he could reach the right side and bottom of the panel with his right hand, and his left hand could reach the left side and bottom, but the center and top of the panel were inaccessible. Since Mercury gloves were thicker and heavier than those on flying suits, all controls had to be positive in operation, including guards for pushbuttons and with key handles and pull rings designed for a good grip and the application of considerable force, up to 50 pounds in some cases.

This New Ocean, ch. 8-4

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    $\begingroup$ I think the above text (interesting, thanks!) is only referring to location and placement. I doubt that operating a switch with gloved hand is easier or harder in different orientations, and sadly the text isn't entirely definitive there. If operating switches was easier in a horizontal orientation, they'd likely have continued the practice on Gemini? $\endgroup$ – Innovine Jun 17 '20 at 8:49
  • $\begingroup$ Yea, it’s interesting. Never read a John Glenn biography, time to put one in the cue. Could be more to discover there. $\endgroup$ – Anthony Stevens Jun 17 '20 at 10:46

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