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Running it on a timer actually works quite well. I don't know how this particular system actually works, but for example the Saturn V launch vehicle handled the
by lokedhs 7y ago
Running it on a timer actually works quite well. I don't know how this particular system actually works, but for example the Saturn V launch vehicle handled the initial navigation for several minutes from takeoff by executing previously calculated commands based on launch time, weather conditions etc.
Also, if I have understood things correctly, the lunar lander used a timer based approach to keep the rotation of the vehicle aligned with the surface of the moon as it orbited.
Since the orbital dynamics are very well understood and there really isn't anything that can affect the motion of the spacecraft other than engine burns, there doesn't seem to be any good reason to make it more complicated.
- BurningFrog 7y agoWhen in stable orbit, I buy that argument. But many things can go slightly wrong when firing all engines fighting your way up the atmosphere.
- lokedhs 7y agoThat is true. In the Saturn V case, the guidance computer checked the actual location of the spacecraft and issued corrections that had accumulated due to precisely that.
- rory096 7y agoAtlas V burn was nominal, this error didn't happen until the capsule was out of the atmosphere.
- willis936 7y agoAnd even more things can go very wrong with more complicated control systems.
- Ididntdothis 7y agoI thought the space shuttle was the same. They took wind measurements before launch and the ascent was hard coded based on that data.
- unreal37 7y agoThe Space Shuttle was always hand flown, not automated.
- Ididntdothis 7y agoLaunch was automated. Landing was manual but not for technical reasons.
- lokedhs 7y agoDidn't they do one automated landing? I seem to remember reading that.
- Ididntdothis 7y agoThey could do it but the pilots wanted something to do so they got to fly manually. The Russians did unmanned launch and landing with their space shuttle Buran.
- jczhang 7y agoWind?!
- johannes1234321 7y agoOnnplanet earth, where those things are launched their is an atmosphere with wind. That wind impacts where exactly the rocket leaves the atmosphere and deploys the space ship.
- TheOtherHobbes 7y agoA man-rated launch vehicle failing to reach orbit seems like very good reason.
- AWildC182 7y agoThe complexity of adding a remote man it the loop creates way more room for error than running a timer. They just fucked up plain and simple. This is like saying that because the airplane crashed because the wing was incorrectly designed and popped off, everyone should fly biplanes...
- dotancohen 7y ago> This is like saying that because the airplane crashed because the wing > was incorrectly designed and popped off, everyone should fly biplanes... We do that. Not with the wings, but with the engines. When jetliner engines were less reliable, we required 3 or more engines on flights that included long sections without passing near an airport (mostly transoceanic flights). Now that some engines are more reliable, we have ETOPS certifications for jetliners using two high-reliablility engines. And yes, there still are two, because no matter how reliable the engines may be, one _may_ fail. What is backing up that CST-100 timer? https://en.wikipedia.org/wiki/ETOPS https://en.wikipedia.org/wiki/ETOPS
- unreal37 7y agoIt did reach orbit. They're just not at the orbit they want to be at.
- Jkosmonaut 7y agoThe man-related launch vehicle worked flawlessly. This was a capsule failure. They’re built by different entities.
- natch 7y ago>Running it on a timer actually works quite well. It would seem we have an existence proof now saying that the above statement is incorrect.
- melq 7y agoBecause one specific implementation seems to have failed a test run?
- pc86 7y agoLet's compare the number of instances a timer has caused an issue and the number of instances it hasn't to determine the actual rate before we make a broad assumption about a field we have no experience in due to a single test case, yes?
- natch 7y agoYeah I’m a programmer like most of us here and I’ve seen timers abused quite a lot. They sometimes are appropriate, but more often, they are good examples of an antipattern. The wording “it would seem” should have tipped you off that no assumptions are being made, but I guess it didn’t work. And even if we were to make a comparison as you suggest and derive some ratio, that’s not super useful without comparing it to the ratio for some alternative approach that does not use timers.
- bufferoverflow 7y ago> Since the orbital dynamics are very well understood and there really isn't anything that can affect the motion of the spacecraft other than engine burns This is wrong. 1) Atmospheric drag (unless you're in really high orbits) 2) Wind 3) Uneven gravitational field. Our planet is not a perfect sphere. The moon is even less so. 4) Solar pressure (though very minor and kinda evens out in orbit).
- beering 7y agoWhich of these can't you calculate ahead of the launch? Numbers 1, 3, and 4 seem like you could calculate it ahead of time. And maybe number 2 as well, if you do it relatively close to launch time.
- nategri 7y agoThey use models. No model is perfect, they all have uncertainties.
- entropicdrifter 7y agoWhich is why they use pilots too
- sheinsheish 7y agoI wonder how come none of you geniuses don’t already work for NASA
- magduf 7y agoI'll name two things: 1) Government pay 2) Government shutdowns But regardless, this was a Boeing spacecraft; it wasn't built by NASA (NASA generally does systems engineering; contractors build things like this).
- dgoodell 7y agoA government shutdown is a basically surprise paid vacation, as long as you have enough cash to skip a couple paychecks.