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Comment by theanirudh | Hacker News Reader

They have physical buttons Incase the touch functionality misbehaves.

But there’s only a handful of buttons, no? Unless I’m missing something. Might be a dumb question but the Apollo control panels had hundreds. How would you manually fly the Dragon in the event of a screen failure? I’m assuming this question was answered somewhere, since the thing was certified to fly, but I must’ve missed it.

Edit: Is the answer simply "it doesn't, it gets flown remotely from Mission Control"?

You don't manually fly it? The physical buttons correspond to pre-programmed procedures/abort modes.

They use a touchscreen so they don't need to have hundreds of buttons for things that aren't necessary to have around all the time.

Im not sure, even I would like to know the answer to this.

Well, Apollo did a lot of complicated stuff in space and on the moon, while the spacex capsule just goes up and then down.

Only questionable bit is how they do the docking without the screens.

with a rusty script that succeed 99% of the time.

The docking is automated as well.

The docking is automated.

There is a manual option if there is a crew onboard. I can’t really think of any reason outside of a dire emergency to use it though.

You probably don't fly manually, just use predefined abort procedure or receive configuration from ground control. It looks humans now are just another cargo and screens are only for non-critical flight information purpose (in other case I cannot see how they would get away with touchscreen only and software running on Chromium).

It's interesting to wonder whether if Apollo 13 style fault happened, modern ships would be easier to reconfigure and rescue or harder?

They have 3 screens. If one screen fails, they can probably continue using the others.

Give their docking simulator[1] a go on a phone or tablet - I was dubious at first, but even on an iPhone I managed to complete manual docking on the first attempt. It turns out flying a spaceship is very different to flying a plane, and rapid inputs just aren't massively important. Generally your edit is probably true as well - in standard flight everything is meant to be on autopilot using predefined routines for the mission, computers are just significantly better at performing a 16 second burn at 82% thrust at precisely T+12:48:16.

That makes sense. Flying a plane is all about responding to perturbations to keep on an even course. A spaceship has literally zero perturbations. It goes exactly as you direct it to go, within the precision of your burns. So its all about carefully issuing bang-bang control signals (burn for 2 seconds) then measuring the response against expectations.

It's close to zero over short distances (ignoring solar wind and LEO atmosphere), although you're still trying to dock with a moving target.

If you've played KSP or read about Gemini 4, the relative motion can be unintuitive due to orbital mechanics. The SpaceX docking simulator puts you right next to the ISS with low relative velocity -- as it would be in real life if everything went as planned -- but it would be much more challenging if you needed to do it manually from a greater distance and relative velocity.

You managed to dock in a simulation in which it's guaranteed that nothing goes wrong. Most of the switches and buttons are there for when something does go wrong.

I think the main reason there are so few buttons on Dragon is that it evolved from an uncrewed vehicle that was designed to be flown from the ground, so everything is much more connected and software controlled than was even practical in the shuttle era.

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