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