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When you think about it from a first principals perspective, having multiple touchscreens is better than only having physical switches. When a switch is damaged

When you think about it from a first principals perspective, having multiple touchscreens is better than only having physical switches. When a switch is damaged/fails, you are out of luck. When a touchscreen is damaged/fails, you use the one next to it. On a rocket you do not have the mass or room to have more than 1 of all but the most critical of switches. There have been quite a few missions that nearly caused death or mission failure directly due to a switch getting broken (Apollo 11, lander return engine-arm switch) or going faulty (Apollo 14 abort switch). What really matters is that they have no single point of failure (touch screens can do everything switches can, an individual touch screen is not important, and switches can cover abort/return scenarios to protect the crew). For the software, it only matters that its been fully tested, including random bit flips and hardware failure. From a cost savings perspective, its vastly cheaper to verify that 3 touchscreens are working correctly than the 600 switches they replace.

colllectorof 6y ago
>When a switch is damaged/fails, you are out of luck. When a touchscreen is damaged/fails, you use the one next to it. This is a trivial problem to solve on a physical interface. One solution could be what is commonly used on hardware synthesizers. A shift button or switch. You engage it and all controls begin to perform their secondary functions. You get redundancy for the price of one extra control and a secondary set of labels in a different color. Also, use of displays to virtually label buttonss is common. In such case you can reassign a control if one fails. In any case Dragon capsule had physical buttons for important functions as a backup.
- extrapickles 6y ago
  The touchscreen frees you from the complexity that comes with giving switches alternative modes, and gives you the mass to have multiple copies of critical switches. Also multimode switches greatly increase the complexity and failure modes, so they need to be done so that if a switch is triggered in the wrong mode its recoverable (eg: the switch for aux radio power isn’t also the undock switch). When you get to the point of having displays for the switches why not go full touchscreen and eliminate all of that cost and complexity of a bunch of tiny displays?
fomine3 6y ago
This is good point. What's important for spaceship is different from car.

colllectorof 6y ago

>When a switch is damaged/fails, you are out of luck. When a touchscreen is damaged/fails, you use the one next to it. This is a trivial problem to solve on a physical interface. One solution could be what is commonly used on hardware synthesizers. A shift button or switch. You engage it and all controls begin to perform their secondary functions. You get redundancy for the price of one extra control and a secondary set of labels in a different color. Also, use of displays to virtually label buttonss is common. In such case you can reassign a control if one fails. In any case Dragon capsule had physical buttons for important functions as a backup.

extrapickles 6y ago
The touchscreen frees you from the complexity that comes with giving switches alternative modes, and gives you the mass to have multiple copies of critical switches. Also multimode switches greatly increase the complexity and failure modes, so they need to be done so that if a switch is triggered in the wrong mode its recoverable (eg: the switch for aux radio power isn’t also the undock switch). When you get to the point of having displays for the switches why not go full touchscreen and eliminate all of that cost and complexity of a bunch of tiny displays?

fomine3 6y ago

This is good point. What's important for spaceship is different from car.