Thread: Commercial Crew
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Old July 14th 19, 11:32 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Default 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