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#3120
by
iskyfly
on 23 May, 2014 14:29
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What is a "long form bus tie" and how does it differ from a regular bus tie?
Thank you
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#3121
by
mkirk
on 23 May, 2014 16:10
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What is a "long form bus tie" and how does it differ from a regular bus tie?
Thank you
Wow, it’s probably been 15 years since I’ve answered this relatively common training question. If I recall correctly…and in very over simplified terms;
If we lost equipment powered by one of the orbiter’s main electrical power buses (maybe because of a failed fuel cell for example), that bus and its related equipment could still remain powered by performing a "bus tie". Tying main buses is achieved by connecting the buses to the orbiter’s tie bus circuit. Power was then transferred between the buses across the common “tie bus”. When performing a bus tie, the "bad bus" (the one with a fuel cell problem in this case) was tied to a good bus. Standard tying convention was Main A to Main B, Main B to Main C and Main C to Main A with the bad bus being the first in the naming convention, and the good bus being the second.
So, if fuel cell 2 had a problem, MN B, which is normally powered by fuel cell 2, is the "bad bus”, MN B would be tied to MN C by taking the MN B Bus Tie switch located on the Pilot's right console to ON followed by the MN C Bus Tie switch to ON.
Although you could tie buses with two simple switch throws, there was a cue card procedure (located on the PLT’s right console) that had about a dozen steps. Generally during first stage, and when related voltages were at an acceptable level (about 20 volts), you would just do the short form (time critical) action of throwing those couple of switches. However, the rest of the time you would follow the 12 steps or so of the “long form” procedure which entailed protecting related equipment on the buses from unacceptable voltage transients during the tie process.
Mark Kirkman
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#3122
by
iskyfly
on 23 May, 2014 17:00
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Thanks Mark!
Last one for now;
"4 minutes to spreading" "clear it" "can't be cleared".
?
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#3123
by
alk3997
on 23 May, 2014 22:15
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Thanks Mark!
Last one for now;
"4 minutes to spreading" "clear it" "can't be cleared".
?
Spreading is short for "Spread Spectrum" which is a mode of communications with the TDRS. I'll need to listen to the conversation to understand the context for "clear it" and "can't be cleared".
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#3124
by
iskyfly
on 24 May, 2014 00:43
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#3125
by
iskyfly
on 24 May, 2014 01:42
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#3126
by
mkirk
on 24 May, 2014 12:20
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During the sim run posted here;
http://forum.nasaspaceflight.com/index.php?topic=17437.msg1202400#msg1202400
at 56 seconds;
I familiar with the engine performance calls (single engine ops 3, two engine TAL, etc etc). But I have never heard of (because it was never needed) it expressed in thirds, ie - "One and two thirds negative return."
What does "One and two thirds" mean?
"1 & 2/3" are abort boundary calls for "stuck" scenarios. These are based on having a shuttle main engine "stuck" at a reduced power setting - for example this could happen when an engine fails to throttle all the way back up after being throttled down during 1st stage ascent.
In this video (which unfortunately doesn't cover the first part of the sim run) it appears they experienced a left engine hydraulic lockup during the timeframe of the throttle bucket, so this would mean the engine valves are effectively locked in their current position and the engine can not be throttled. This lockup also played into why the engine is being intentionally shut down early at a velocity of 23K (23,000 feet per second).
Mark Kirkman
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#3127
by
mkirk
on 24 May, 2014 12:28
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Thanks Mark!
Last one for now;
"4 minutes to spreading" "clear it" "can't be cleared".
?
Spreading is short for "Spread Spectrum" which is a mode of communications with the TDRS. I'll need to listen to the conversation to understand the context for "clear it" and "can't be cleared".
This is just a swag since my comm system knowledge was always a little week (and shame on me for that since it really is an absolutely critical system for a space flight system);
I think INCO is saying he can not manage the comm system for spreading because they are stuck with the SPCs (stored program commands) they had pre liftoff. SPCs allow for antenna and comm system management during ascent.
Mark Kirkman
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#3128
by
iskyfly
on 24 May, 2014 16:38
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Oh thank you so much Mark, Andy and Dave, and Phillip.
Juicy stuff!
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#3129
by
psloss
on 25 May, 2014 13:04
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Oh thank you so much Mark, Andy and Dave, and Phillip.
Juicy stuff!
If you are a L2 member, the audio from first part of that ascent sim run is covered in there.
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#3130
by
alk3997
on 26 May, 2014 05:21
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Thanks Mark!
Last one for now;
"4 minutes to spreading" "clear it" "can't be cleared".
?
Spreading is short for "Spread Spectrum" which is a mode of communications with the TDRS. I'll need to listen to the conversation to understand the context for "clear it" and "can't be cleared".
This is just a swag since my comm system knowledge was always a little week (and shame on me for that since it really is an absolutely critical system for a space flight system);
I think INCO is saying he can not manage the comm system for spreading because they are stuck with the SPCs (stored program commands) they had pre liftoff. SPCs allow for antenna and comm system management during ascent.
Mark Kirkman
Filling in a bit more, BFS was in control of the antenna pointing during ascent / entry, including selecting which s-band antenna to use. PASS didn't control the antennas until OPS 2 when the Systems Management computer was brought up.
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#3131
by
mgfitter
on 28 May, 2014 21:18
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Whatever happened to the "Tin Whiskers" problem from back in 2006?
Clearly they were able to fly the remainder of the flights without problems, but I never heard what the solution was?
-MG.
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#3132
by
jeff122670
on 28 May, 2014 23:01
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Wayne Hale mentions the "Beester Balls" in a talk once at GWU... Aside from me mis-spelling it, what was that again?
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#3133
by
DMeader
on 28 May, 2014 23:07
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Whatever happened to the "Tin Whiskers" problem from back in 2006?
Clearly they were able to fly the remainder of the flights without problems, but I never heard what the solution was?
-MG.
Probably in the end, stop using solder with a high tin content, along with various coatings, plating with different metals, etc.
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#3134
by
mkirk
on 29 May, 2014 02:33
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Wayne Hale mentions the "Beester Balls" in a talk once at GWU... Aside from me mis-spelling it, what was that again?
Ha....you said "balls"
As in Ball-Strut Tie Rod Assembly (BSTRA)
Mark Kirkman
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#3135
by
iskyfly
on 29 May, 2014 04:03
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What does the following call from FDO to FD mean?
"we took a thrust update of plus 6"
Thank you.
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#3136
by
iskyfly
on 30 May, 2014 19:32
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I promise I searched for hours before asking this.
I know there is the "The all-eventful STS-93 launch" and I have searched the Shuttle Q & A's and read a few posts (seem to remember one saying- oh now I know why the forums went crazy). Could somebody please point me to the threads that discuss the investigation and results of the short?
It was stated that this was a transient on AC1 and that AC1 looked ok in the later stages of launch. Why didn't the engine controllers that were knocked offline come back on after the "transient" ?
Thanks!
-Giles
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#3137
by
DaveS
on 30 May, 2014 19:53
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I'm 100% certain if this but the only way to recover a lost DCU is to power cycle the MEC itself. That would mean shutting down the engine.
They never lost the entire MECs for the center and right engines, only the DCUs which are components of the MECs.
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#3138
by
GLS
on 31 May, 2014 18:48
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(Let's see if I know as much as I think
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When the voltage got outside of the limits of the controller channel, it did a "self disqualification", and from then on it does nothing, regardless of what happens to the voltage. When you're in flight that's it, you can't do nothing else, and you become fully dependent on the other channel.
On the ground, you have more options (I could be wrong in some of this):
> if the controller went completely dead (no power) during the "transient", I think it goes into PROM standby when the power comes back on, and then the LCC would have to send several commands the controller, so it gets to the appropriate phase and mode.
> if it did not power off completely, the LCC can send a channel reset ou a controller reset command (not sure which) to "re-qualify" that controller channel.
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#3139
by
iskyfly
on 02 Jun, 2014 14:52
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Is the audio on this a real RTLS / ditching sim? If so, does anyone know when this sim was conducted?
What does "2 engine out blue" and "push buttons" mean?
also;
"He needs to get the nose down.... he's at alpha 7"
Thank you!
Giles
)