#61
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Commercial Crew
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#62
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Commercial Crew
JF Mezei wrote on Sun, 14 Jul 2019
13:52:32 -0400: On 2019-07-13 18:36, Fred J. McCall wrote: You say that like it means something. What you've argued is that because your lungs work your brain isn't important. You have argued that stage II has the brains. I have argued they each have brains. And stage 1 needs brains to laund by itself while stge II is busy doing orbit insertion. No, that is not what you have argued at all. YOU have argued that all the pieces parts (first stage, second stage, capsule) must have the SAME brains and all get the SAME data. What you have argued is bull****. Again you seem to think you have a point when you do not. The main engine control computers are at the top of the second stage. If they stop talking, it's pretty simple logic for the first stage to know to shut down. If the brains are in stage II, then how does Stage 1 have the brains to know to stop its engines? And how does Stage I know how to land by itself? If your brains are in your head, how do your heart and lungs know to keep working? The range safety stuff is all in the second stage. Again, simple logic for the first stage to fire it when the second stage stops talking. The text of user guide menbtions C band radios in each stage. Consider that while landing, range safety might be needed to blow up stage I. Consider that you are an idiot and might need to blow yourself up. Nobody (but you) has said there is ZERO logic and NO computers in stage one. You then pretend WE said that and argue against your own illiterate interpretations. Crew Dragon doesn't get telemetry from the first stage whether Stage 2 is there or not. So the crews can't tell if all engines are running normally? Can't tell if gimbaling working properly? can't look at pressures and fuel levels? Why would they need to and what could they do with the data? Redundancy and disaster tolerance in logic. WHICH YOU DO NOT WANT IN A SYSTEM LIKE THIS! This is no missile. Ub fact, "man rating" a rocket is all about making it different from single use missile. You're a ****ing idiot. The LAST thing you want in an automatic escape system is redundancy that leads you to NOT abort. "Falcon vehicles are capable of detecting 6 separation events through breakwire pairs, and a separation indication signal for each will be included in launch vehicle telemetry. "separation indication signal" = detection of breakwire is made by sensors and it is those sensors that create the telemetry event. This isn't some wire that goes all the way to the CPU. Thank you, Captain Obvious. Practically NO data wires run "straight to the CPU". Do you know nothing about computers? Also, a breakwire loop does not imply complex connector between stages. Simply implies a sensor on one side with a wire looping thorugh the separation. When wire breaks, the sensor on one side detects the breek and sends signal. Again, thank you, Captain Obvious. This means that Dragon2 would not know of a separation event because some line dropped to 0 volts since the breakwire loop between stage 1 and 2 is only a short loop across the divide and doesn't travel the lentght of stack. The only way Dragon2 would know of a separation even is if telemetry is sent to it and would include the event detected by the sensor on one side of such a loop. Absolute ignorant bull****. PULL YOUR HEAD OUT OF YOUR ASS! You just asserted that Dragon 9 cannot work, since the payload can never know if it has separated from the booster. Same logic (or lack thereof) applies. If you were THINKING rather than ARGUING you would realize that the simplest way to implement this sort of thing is to have a sensor on each 'side'. When the wire breaks or is commanded to zero both sides know. No telemetry required. But not in things like escape systems, where what you want is a single "we're ****ed" vote sending you on your way rather than having the capsule destroyed because it's hanging around waiting for election results. All the more import5ant for Dragon2 to get a copy of telemetry so it can see events just priorr to looss of telemetry and make a decision by itself should telemetry and/or commands from the computers below be lost. Absolute horse****! Why do you think "loss of telemetry" is sufficient to know but keep ignoring that loss of a single discrete is also sufficient to know and a much more robust system? The capsule doesn't need to know anything other than that it has been told to get the **** out of there. You're comparing apples and aardvarks again. The Shuttle had big pieces of its flight envelope where there was little chance of survival if something went wrong. Most 'abort' scenarios were pretty much all manual. NEITHER of those things is true of the Falcon 9/Crew Dragon. I was p]roviding an example where crew compartment having telemetry and thus being able to advise crew things were slowly startuing to streay from normal was a good thing instead of just some instant "ABORT" without warning. Ask yourself what they can do with the data if they have it. The answer is 'nothing'. describe above is there for EXTERNAL range safety termination of the believe that an internally commanded activation of the FTS works that way? Why should it be any different? Because it's stupidly more complex than it needs to be. Range safety implies some computer sending commands in the right sequence to turn off engines and then fire pyrotechnics in a variety of places. Whether that computer receives commands via radio or from another on-board computer who had decided the rocket was misbehaving should make no difference. But when the command to activate rage safety is made by computers, once would assume some vote is taken to ensure it isn't 1 rogue computer that lost telemetry feed that issues a "kaboom" command while the other 2 computers are getting telemetry confirming rocket is functionaing perfectly normally. Your preceding remarks are totally on their ass. Why would you want a 'vote'? Suppose one computer says to fire the FTS and the other says not to. Further suppose that the one that says not to 'wins the election'. Now suppose that that computer is the one that is wrong. Congratulations, you just fragged Miami. That's why there is no 'vote'. Because you want ANY decision to fire the FTS to be executed immediately. And we have, in fact, had rockets activate their FTS when nothing was wrong due to a computer/sensor error on board the vehicle. This simple fact shows that your whole scenario above is bull****. How do you think signals get around? Magic? You seem to imply that each type of signal is a physical copper wire with 0 or 1 voltage in it. I'm not responsible for what you infer because you're a ****ing illiterate idiot. I am arguing thsi ios not the case in modern systems because it would be a redundant data link transmitting formatted data between stages in order to limit how many physical connectors are needed. For an abort you need one wire (in the simplest case). What you probably actually have on Falcon 9 is two independent loopback command wirss and the abort is triggered if EITHER of them signals abort. The connectors and wires already exist. How many strangs of copper need to be connected is what matters and was a problem in Shuttle because they had built it the way you say with many many separate connectors and that caused issues. See below. Try actually reading and understanding the answers that people give you instead of just searching for grist for your little argument machine. "Up to 96 additional (48 redundant) commands can be accommodated as a nonstandard service; please contact SpaceX for details." Commands implies a data connection, so you own post negates your insulting of my contention they hacve data connections going both ways. And what is 'data', you yammerhead? It's a voltage. DUH! You argued wrong. No 'software' change is required. It's all manual steps. In a "fuel before boarding" scenario which was before SpaceX convinced NASA to allow fuel after boarding, code would need to inhibit triggering or arming of abort (consider case where mistake happened and abort was armed). Then it armed early and you've ****ed up. So for sure there is code in there to hadnle such cases. If I can think of a failure mode, than SpaceX engineers thought of it. Utter bull****! Do you seriously believe there are zillions of lines of 'software interlock' code on the vehicle? You're delusional! Again, assume the implementers are NOT cretins. Which is why I argue that the system is far more robust that you think it is. This is no single use missile whose sole purpose is to destroy itself. Except you argue that they ARE cretins, or at least share your level of ignorance about engineering. Ah, you finally mention what you're talking about by name. Would you be surprised to learn that 1553 is not slow and is used almost everywhere in everything that flies? It's used where military is present. Not used commercially. And yes, it is slow by today's standards. At much higher speeds, latency is lower. Bull****. Virtually every satellite launched in the Western World uses it, both military and commercial. The French (of course) have their own virtually identical system (DIGIBUS) and obviously the Chinese (GJV289A) and the Russians (GOST R 52070-2003) have their own similar systems. If something faster is needed Firewire will often be used. Wasn't aware Firewire was even used for such purposes. It isn't used for normal comp]uting anymore, hasn't for a long time. You're not aware of a lot of things. You typically don't see it listed as 'Firewire', but rather as IEEE 1394. Then the situation won't be recognized by people, either. This assumes every possible scenario has been considered by the engineers who programmed the computers and thought in advance of installing sensors for every possible scenario. If the scenario wasn't considered, nobody will recognize it when it happens and you'll only find it with a post mortem. Say a bird hits the widshield at speed and there is a big crack in it. Cabin pressure would still be OK, but crew might decide to abort because they know the window won't survive. Do they wait for window to break and cabin pressure sensors to detect bad event and trigger abort, or do they manually trigger abort before window breaks? Neither, since the crew can't "know the window won't survive". Engineers spend a lot of time planning on handling as many failure modes as they can possibly think of. But that doesn't mean that they can handle 100% of them. Which means humans won't know about them to recognize them when they happen. 2b2) It wasn't a data anomaly and you really are ****ed and everyone dies. If two computers have valid telemetry that show nominal flight profile, and 3rd computer has lost telemeytrry eother fully or partially, or getting wrong data, then the 2 computers win. This points to the 3rd computer being the fault instead of the rocket's engines, tanks etc. And that, my children, is how you build systems that 'fail deadly'. That is the whole point of redundancy and voting between computers. Which you don't do on safety critical actions like crew aborts and Flight Termination. If majority of computers get data that shows rocke is not nominal, then the decision to abort is straightforward. And if they don't and the capsule hangs around waiting for all the hanging chads to be analyzed everyone dies. And this is where telemetry to Dragon 2 capsule is important: if they see that there is disagreement wih computers and that one is recommending abort, they can then make judgement call on how to handle situation and have hand on the big red abort button just in case. Utter bull**** and SpaceX engineers obviously disagree with you. -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#63
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Commercial Crew
JF Mezei wrote on Sun, 14 Jul 2019
14:09:30 -0400: On 2019-07-14 09:05, Jeff Findley wrote: It's going to know right away because its going to lose the link to the second stage and its engines will shutdown. Exploding tank in stage 2 might not sever the "voltage or not" line. So the Flight Computer detects the event (or the run up to it) and pulls the 'voltage or not' line to 'not' and everyone gets the **** out of there. Consider Apollo 13. They lost one side of the command module but much of it remained functional. What alternate universe do you live in? They didn't lose "one side of the command module". They had a fuel cell external to the pressure hull explode. This cost them electrical power in the Command Module, We've gone over this what feels like 100 times. The "abort now" wire going to the capsule that should have a positive voltage during launch I really doubt "man rating" a rocket would accept a single wire as the one commanding the catrastophic abort. That's because you're an ignorant git. If you insist on an old analogue voltage or no voltage wire, ... Uh, what do you think a binary 'one' looks like on a typical computer data line? It's a voltage, you ignorant git. A binary 'zero' is typically 'no voltage'. ... they at the very least put 3 such wires each 120° apart around the rocket and have computers at least requite loss of voltage on 2 wires for more than x milliseconds. And there's the system that would NOT be man rated. But I really doubt that Musk would have gone for 1950s analogue stuff on a modern rocket, Especually since Falcon9 would not have had such a wire running in cargo missions that don't have abort. Go read the FUS again. Consider also that there must be some delay betwene initiation of Dragon2 abort, and initiation of the self destruct charges. So it can't be the same wire. First, why does there need to be a delay? Second, why can't the signal be the same wire even if you want a delay? That is because the initiation of an abort really only needs one signal wire (and a ground as a voltage reference). We've both been telling you this from the beginning, but you simply won't listen. Because the use of analogue unreliable connections is not credible in a man rated system built in 21st century. And when the user Guide mentions "command" which implies a data packet sent. What we've described is MORE reliable than any of the Rube Gloldberg systems you've proposed. Again, tell me what a binary 'one' looks like on a wire? Just because old missiles designed in the 1950s used such an alague system doesn't mean Falcon9 added this old mechanism to support Dragon2. You seem to not understand how the hardware in a digital system works. Sure you could let the capsule monitor telemetry from the launch vehicle during the flight. But that is *separate* from the abort system. So you admit Dragon2 might get telemetry? The other guy doesn't admit to it. You're one of those idiots that thinks not using President Trump's name is some sort of 'resistance', too, aren't you? I don't "admit to it" for the same reason I don't "admit to" the first stage getting all the telemetry from the second stage; because there's no reason for it and it would require special data lines that simply aren't normally there on a Falcon 9. I find it hilarious (in a sad way) that you insist that simple 'breakwire' signaling is too complicated despite there being almost 100 command lines (note, COMMAND LINES) between the second stage and the payload (regardless of whether that payload is a Crew Dragon or not) but somehow believe sending all the vehicle telemetry up to the capsule can be handwaved away. -- "Ordinarily he is insane. But he has lucid moments when he is only stupid." -- Heinrich Heine |
#64
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Commercial Crew
I don't normally try to top-post,but there's not a specific comment I want
to respond to but the general idea. JF: Here's the thing (and Jeff and Fred will correct me if I'm wrong) but believe it or not, redundancy is NOT always better. I'll give you two examples" What's safer for a small aircraft, one engine or two? Most people will immediately leap to "two". But, the answer is not that simple. Sure, if one engine fails, you still have another, but... You double your chances of failure. That's a con. AND... in the hands of someone w/o enough experience, you now have an aircraft that immediately wants to flip into the direction of the remaining engine. This can be bad, especially during take-off. So, a 2nd engine does NOT automatically make things safer. The redundancy can in fact make things LESS safe. (but keep in mind it's not purely a binary decision when designing an aircraft). I'll give you another more personal case. I do vertical caving. I teach vertical caving. We use something called "Single Rope Technique" (SRT). Basically we rappel and climb on a single rope. There is NO belay rope. This is often SAFER than having a belay rope. There's a multitude of reasons, but a big one is in many pits, the air will swirl up the pit. This and the motion of the climber (or rappeler) can cause the rope you're on to twist. If you have a single-rope this can lead to a bit of dizziness, but that's about it. With a 2nd rope, they will start to braid each other. This can stop the person completely so they can't move. They are now stuck on the rope. Again " redundancy" is a bad choice here. With the case of Falcon 9, you're confusing the logic to decide if there's an abort with the order to carry it out. There is almost certainly redundancy in sensors (such as the SSME's had) because you don't want a flakey sensor triggering an abort. BUT, once the decision is made, you want it as simple as possible a single wire with voltage is that simple. Yes, is it possible that magically the voltage on that wire drops to zero when it shouldn't and triggers an abort? Sure, I suppose. And in that case the astronauts get a wild ride and a story to tell. But what would be worse is if you have 2 or more wires and one doesn't drop to zero and you do NOT abort when you need to. In that case the astronauts get an obituary and their families are left to tell stories. This is why Jeff at one point uses the term fail-safe. An abort is a "bad day" event" but should be a survivable, even if it's a mistake. A failure to abort when you should have, is potentially a company ending event. So if you're going to fail, fail in a way that's safe for the crew. "JF Mezei" wrote in message ... On 2019-07-14 09:05, Jeff Findley wrote: monitor itself to insure it's on the right trajectory. If its not, it initiates the FTS (flight termination system) in order to make sure that it doesn't go completely off course which might endanger people who are outside of the exclusion zone underneath the intended flight path. My understanding is that FTS is triggered only when the rocket strays from a cone of acceptable trajectory. So it isn't triggered as soon as it strays off nominal trajectory since there could still be hope it recovers. So there is logic involved in this. Of course it does. But that does not negate the fact that the second stage needs to know its trajectory all the way to orbit. So it would make sense that the second stage computers are the ones to insure mission success. Second stage computers only need situational awareness, aka a copy of telemetry feed and comms with first stage computers. First stage computers needs the logic in order to land, swo it can't be a slave to second stage. Landing happens *after* first stage separation. It's a secondary objective not directly tied to mission success. But still critical one because first stage could go nuts and require termination instead of crashing in downtown Cocoa Beach. Why would the first stage ever give a damn about the second stage? It needs to know if second stage is healthy or has exploded or whatever. It should be part of the logic to decide whether to self destruct or not. It's going to know right away because its going to lose the link to the second stage and its engines will shutdown. Exploding tank in stage 2 might not sever the "voltage or not" line. Consider Apollo 13. They lost one side of the command module but much of it remained functional. We've gone over this what feels like 100 times. The "abort now" wire going to the capsule that should have a positive voltage during launch I really doubt "man rating" a rocket would accept a single wire as the one commanding the catrastophic abort. If you insist on an old analogue voltage or no voltage wire, they at the very least put 3 such wires each 120° apart around the rocket and have computers at least requite loss of voltage on 2 wires for more than x milliseconds. But I really doubt that Musk would have gone for 1950s analogue stuff on a modern rocket, Especually since Falcon9 would not have had such a wire running in cargo missions that don't have abort. Consider also that there must be some delay betwene initiation of Dragon2 abort, and initiation of the self destruct charges. So it can't be the same wire. That is because the initiation of an abort really only needs one signal wire (and a ground as a voltage reference). We've both been telling you this from the beginning, but you simply won't listen. Because the use of analogue unreliable connections is not credible in a man rated system built in 21st century. And when the user Guide mentions "command" which implies a data packet sent. Just because old missiles designed in the 1950s used such an alague system doesn't mean Falcon9 added this old mechanism to support Dragon2. Sure you could let the capsule monitor telemetry from the launch vehicle during the flight. But that is *separate* from the abort system. So you admit Dragon2 might get telemetry? The other guy doesn't admit to it. |
#65
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Commercial Crew
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