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#3200
by
Hog
on 29 Jun, 2014 00:40
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.
Thanks for the input Andy&Wayne, and corrections of applications of 109% and 111%.
Is it incorrect to refer to the SSME's and their various upgrades as:
RS-25-A
RS-25-B
RS-25-C
RS-25-D, either inside NASA or outside?
The SSME's original development and it's subsequent upgrades are examples of the great things that determined people can accomplish when the will (and money) is there. What a great service record.
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#3201
by
AnalogMan
on 29 Jun, 2014 11:13
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#3202
by
aero
on 29 Jun, 2014 19:42
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So regarding my question of identifying a consistent set of engine parameters for the SSME in order to validate my engine model, it seems clear that using the engine at 109% thrust is not a good choice. It also seems clear that there is no specific designation for a particular engine model so how does one correctly ask the question?
Let me ask this. With all of the modifications to the SSME over its lifetime, did the nozzle diameter ever change or was it fixed for all time?
I know the engine throat diameter changed and that the nozzle expansion ratio changed and the combustion chamber pressure changed and of course the thrust and Isp changed. Did the fuel mix ratio change?
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#3203
by
Hog
on 29 Jun, 2014 21:45
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So regarding my question of identifying a consistent set of engine parameters for the SSME in order to validate my engine model, it seems clear that using the engine at 109% thrust is not a good choice. It also seems clear that there is no specific designation for a particular engine model so how does one correctly ask the question?
Let me ask this. With all of the modifications to the SSME over its lifetime, did the nozzle diameter ever change or was it fixed for all time?
I know the engine throat diameter changed and that the nozzle expansion ratio changed and the combustion chamber pressure changed and of course the thrust and Isp changed. Did the fuel mix ratio change?
There should be clear engine parameters for each engine model: (if these are correct)
FMOF=(engines 2005, 2006 and 2007-STS 1-5)
Phase 1
Phase II
Block 1
Block 1-A
Block II-A
Block II
from Analogmans above post.
Here is Part#1 of a 10 part series, seems detailed.
http://www.enginehistory.org/SSME/SSME1.pdf
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#3204
by
alk3997
on 29 Jun, 2014 22:07
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So regarding my question of identifying a consistent set of engine parameters for the SSME in order to validate my engine model, it seems clear that using the engine at 109% thrust is not a good choice. It also seems clear that there is no specific designation for a particular engine model so how does one correctly ask the question?
Let me ask this. With all of the modifications to the SSME over its lifetime, did the nozzle diameter ever change or was it fixed for all time?
I know the engine throat diameter changed and that the nozzle expansion ratio changed and the combustion chamber pressure changed and of course the thrust and Isp changed. Did the fuel mix ratio change?
There should be clear engine parameters for each engine model: (if these are correct)
FMOF=(engines 2005, 2006 and 2007-STS 1-5)
Phase 1
Phase II
Block 1
Block 1-A
Block II-A
Block II
from Analogmans above post.
Here is Part#1 of a 10 part series, seems detailed.
http://www.enginehistory.org/SSME/SSME1.pdf
The paper pre-dates the Block I upgrade by a few years. So I don't think that holds much water from a designation standpoint.
I'm not an engine guy so we just referred to them as SSMEs and then phase II, Block I, IIA and II when discussing the type of SSME.
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#3205
by
aero
on 29 Jun, 2014 22:46
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Here is Part#1 of a 10 part series, seems detailed.
http://www.enginehistory.org/SSME/SSME1.pdf
A very interesting read. I did find that external tank pressurization takes 0.7 lb/s H2 and 1.2 lbs/s O2. This may (?) reduce the chamber mass flow by 1.8 lb/s or 0.8165 kg/s. A small but real amount. ~0.16%
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#3206
by
Specifically-Impulsive
on 30 Jun, 2014 03:37
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I know the engine throat diameter changed and that the nozzle expansion ratio changed and the combustion chamber pressure changed and of course the thrust and Isp changed. Did the fuel mix ratio change?
Yes the controller (i.e. commanded) mixture ratio changed over time. I know it changed from 6.0262 to 6.011 in the mid 80s because I had to change a simulation model to match the real world change. I am not as sure of this next bit but I think it was changed during the second return to flight as well. Maybe other times too.
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#3207
by
Specifically-Impulsive
on 30 Jun, 2014 03:57
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A very interesting read. I did find that external tank pressurization takes 0.7 lb/s H2 and 1.2 lbs/s O2. This may (?) reduce the chamber mass flow by 1.8 lb/s or 0.8165 kg/s. A small but real amount. ~0.16%
Pressurization flows varied with power level and the O2 flow also varied with the position of the GO2 repress valves....and yes, these flows didn't go overboard, which is one of the reasons that the overboard mixture ratio was different than the controller mixture ratio.
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#3208
by
sivodave
on 02 Jul, 2014 18:57
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Hello all.
I was interesting to know if the dog-leg maneuver Atlantis underwent during ascent on STS-36 to reach 62 deg of inclination had any effect on the abort modes? Would it have been possible to perform a TAL, for example? What about a RTLS?
Also, how much payload performance Atlantis lost in doing the dog-leg?
Thanks very much
Davide
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#3209
by
wolfpack
on 02 Jul, 2014 21:02
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Hello all.
I was interesting to know if the dog-leg maneuver Atlantis underwent during ascent on STS-36 to reach 62 deg of inclination had any effect on the abort modes? Would it have been possible to perform a TAL, for example? What about a RTLS?
Also, how much payload performance Atlantis lost in doing the dog-leg?
Thanks very much
Davide
You can figure an RTLS due to a failure prior to SRB sep would be the same as any other flight at the maximum northern azimuth from KSC, since the dogleg is performed after staging. Beyond that, it would depend on the flight dynamics, which we don't know.
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#3210
by
Jim
on 02 Jul, 2014 21:15
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The nominal performance loss per degree of inclination was around 625 lb per degree. TAL was still viable because the vehicle was still going over Europe.
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#3211
by
Malderi
on 02 Jul, 2014 23:22
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How much payload mass to ISS was lost on Shuttle launches due to that inclination? My understanding was that the majority of those payloads were limited by CG constraints rather than overall mass. I don't know how many missions were actually up against mass limits, though.
Another question - for Shuttle ascent control/performance, the weight and mass distribution was required, but how precise was this figure? Presumably they didn't weigh every astronaut's breakfast the morning before - but maybe they did and I didn't recall reading about it.
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#3212
by
Jim
on 03 Jul, 2014 01:22
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How much payload mass to ISS was lost on Shuttle launches due to that inclination? My understanding was that the majority of those payloads were limited by CG constraints rather than overall mass. I don't know how many missions were actually up against mass limits, though.
Another question - for Shuttle ascent control/performance, the weight and mass distribution was required, but how precise was this figure? Presumably they didn't weigh every astronaut's breakfast the morning before - but maybe they did and I didn't recall reading about it.
No, it was mass limited and not CG constraints. The payloads were set aft in the payload bay for CG considerations.
(51.6-285)x625 lb is ? I thought my post above self explanatory.
450lb was allocated for each crew member which includes the person, food, clothing ,suit and personal items. I don't remember if the seat is included.
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#3213
by
sivodave
on 03 Jul, 2014 07:51
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What was the reason for STS-39 and STS-44 being unclassified DoD missions?
Thanks very much
Davide
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#3214
by
Jim
on 03 Jul, 2014 13:19
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What was the reason for STS-39 and STS-44 being unclassified DoD missions?
DSP (STS-44) was an unclassified program. All DOD missions were classified so that NRO missions could be hidden among them. Since there were suppose to be no more (or one more) DOD missions on the shuttle, there was no sense in spending the money on security to keep up the shell game.
STS-39 was a science mission, it did not have any operational spacecraft and it was towards the end of the DOD missions. There was no need to classify for its own sake.
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#3215
by
thomasafb
on 04 Jul, 2014 21:34
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Hi all,
i am looking for the title of a presentation that must be somewhere in L2 but I have been unable to locate it. It is either refering to STS-125 or -400 and includes the attached chart comparing orbiter orientation to LOCV risk (aptly named: "Micrometeoroid/Orbital Debris (MMOD) Loss of Crew & Vehicle (LOVC) Risk vs. Space Shuttle Orientation"). I would greatly appreciate it if someone could point me in the right direction.
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#3216
by
AnalogMan
on 04 Jul, 2014 22:46
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Hi all,
i am looking for the title of a presentation that must be somewhere in L2 but I have been unable to locate it. It is either refering to STS-125 or -400 and includes the attached chart comparing orbiter orientation to LOCV risk (aptly named: "Micrometeoroid/Orbital Debris (MMOD) Loss of Crew & Vehicle (LOVC) Risk vs. Space Shuttle Orientation"). I would greatly appreciate it if someone could point me in the right direction.
This is from an MMT/OPO (Mission Management Team/Orbiter Project Office) presentation from flight day 6 of the STS-125 mission
"Potential MMOD Damage on Panel 11R".
See page 16 of either of the presentations linked in the first two posts of this L2 thread:
http://forum.nasaspaceflight.com/index.php?topic=17081.0
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#3217
by
thomasafb
on 05 Jul, 2014 07:26
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This is from an MMT/OPO (Mission Management Team/Orbiter Project Office) presentation from flight day 6 of the STS-125 mission "Potential MMOD Damage on Panel 11R".
See page 16 of either of the presentations linked in the first two posts of this L2 thread:
http://forum.nasaspaceflight.com/index.php?topic=17081.0
thanks a lot. looks like my searching skills need some serious training.
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#3218
by
HelixSpiral
on 05 Jul, 2014 21:07
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Watching video of some pre-Challenger launches I noticed the test director using the callsign "LTD" instead of "NTD". Was this designation used for all pre-Challenger launches? Or was it changed away from NTD in anticipation of SLC-6 launches where the test director wouldn't actually be a "NASA Test Director" and instead be an Air Force officer?
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#3219
by
psloss
on 05 Jul, 2014 22:22
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Watching video of some pre-Challenger launches I noticed the test director using the callsign "LTD" instead of "NTD". Was this designation used for all pre-Challenger launches?
Not sure about when it began to be used, but 'L' as in Lockheed (Lockheed Space Operations Company):
http://spaceflight.nasa.gov/shuttle/reference/shutref/sts/background.htmlRockwell's Launch Operations, part of the Space Transportation Systems Division, was under contract to NASA's Kennedy Space Center for turnaround, processing, prelaunch testing, and launch and recovery operations from STS-1 through the STS-11 mission.
On Oct. 1, 1983, the Lockheed Space Operations Co. was awarded the Space Shuttle processing contract at KSC for turnaround processing, prelaunch testing, and launch and recovery operations.
(My emphasis.) This was prior to the post Cold War wave of mergers when Lockheed merged with Martin Marietta. There are some online references to "Lockheed Test Director" (within the context of Shuttle).
Also:
http://forum.nasaspaceflight.com/index.php?topic=5410.msg86281#msg86281