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#3560
by
Archibald
on 30 Oct, 2018 15:58
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Whew. 27 000 pounds ? Should be 13 metric tons. Thank you Jim.
Well, that make some sense. The orbiter was quite a big and heavy spacecraft, nearly thrice as heavy as an Apollo CSM. Takes a lot of storable propellants to move such a big object across the sky.
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#3561
by
Fequalsma
on 30 Oct, 2018 23:30
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You're welcome. It's a handy report. Did it answer all your questions?
F=ma
Archibald, check out the Orbiter weights starting on page D-81 of:
W. Heineman Jr..: “Design Mass Properties II: Mass Estimating and Forecasting for Aerospace Vehicles Based on Historical Data,” Report No. JSC-26098, NASA Johnson Space Center, Houston, TX, November 1994.
http://www.alternatewars.com/BBOW/Space/JSC-26098_Design_Mass_Properties_II.pdf
F=ma
thank you !!
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#3562
by
Archibald
on 31 Oct, 2018 04:31
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Yes it did. Never realized before how heavy were the RCS/OMS systems + their propellants. More or less 1/3 of an orbiter mass by themselves.
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#3563
by
PahTo
on 31 Oct, 2018 12:51
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Yes it did. Never realized before how heavy were the RCS/OMS systems + their propellants. More or less 1/3 of an orbiter mass by themselves.
Note this is why the program adopted burning the OMS engines for about a minute shortly after SRB sep--improve upmass, reduce on-orbit mass and improve down mass.
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#3564
by
Archibald
on 31 Oct, 2018 18:25
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Yes it did. Never realized before how heavy were the RCS/OMS systems + their propellants. More or less 1/3 of an orbiter mass by themselves.
Note this is why the program adopted burning the OMS engines for about a minute shortly after SRB sep--improve upmass, reduce on-orbit mass and improve down mass.
I'm left wondering, was the OMS/RCS oversized for some reason (safety, something else), or was it the absolute right / minimum size for such a big vehicle ?
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#3565
by
Jim
on 31 Oct, 2018 18:45
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I'm left wondering, was the OMS/RCS oversized for some reason (safety, something else), or was it the absolute right / minimum size for such a big vehicle ?
It was sized for flexibility and before direct insertion was developed.
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#3566
by
Archibald
on 01 Nov, 2018 08:57
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(browsed direct insertion) So they found that the SSMEs could do the final push into orbit better than the OMS pods. Interesting.
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#3567
by
Jim
on 01 Nov, 2018 13:15
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(browsed direct insertion) So they found that the SSMEs could do the final push into orbit better than the OMS pods. Interesting.
Due to ISP difference and acceptable ET disposal location.
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#3568
by
Archibald
on 01 Nov, 2018 14:37
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Yeah, sure, at 450 seconds the SSMEs bury the OMS pods - 315 seconds - any time of the week. And of course their propellant tank is jettisoned (the E.T) and not part of the orbiter. On top of that all this OMS propellant can now be used for orbital manoeuvering.
How much did they gained ? I red somewhere the orbiter had 300 m/s of delta-v to manoeuver in orbit. I wonder with what kind of insertion was this calculated.
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#3569
by
wolfpack
on 02 Nov, 2018 20:27
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(browsed direct insertion) So they found that the SSMEs could do the final push into orbit better than the OMS pods. Interesting.
I think they always knew that, but the SSMEs on the first flights were at 100% RPL. 104.5% wasn't certified yet. Hence the OMS-1 burn.
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#3570
by
Jim
on 02 Nov, 2018 22:36
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(browsed direct insertion) So they found that the SSMEs could do the final push into orbit better than the OMS pods. Interesting.
I think they always knew that, but the SSMEs on the first flights were at 100% RPL. 104.5% wasn't certified yet. Hence the OMS-1 burn.
Had nothing to do with thrust level. It was a redesign of the trajectory. Direct insertion could be done with 100% RPL. BTW, 104.5% didn't come around until the ISS era. 104% was the standard after STS-6 or so.
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#3571
by
Fequalsma
on 13 Nov, 2018 03:14
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DaveS, here are the Xo coordinates that I found. How do they compare with yours?
F=ma
602.3, 647.3, 692.3, 737.3
783.6, 828.3, 873.0, 917.7
966.4, 1011.1, 1055.8, 1100.5
1144.2, 1184.2, 1224.2, 1264.2
Does anyone know the Xo locations of the 16 PLBD C/L latches? I have the locations of latches 3 through 16 but I'm lacking the locations of the two forward-most latches.
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#3572
by
DaveS
on 13 Nov, 2018 15:10
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DaveS, here are the Xo coordinates that I found. How do they compare with yours?
F=ma
602.3, 647.3, 692.3, 737.3
783.6, 828.3, 873.0, 917.7
966.4, 1011.1, 1055.8, 1100.5
1144.2, 1184.2, 1224.2, 1264.2
Does anyone know the Xo locations of the 16 PLBD C/L latches? I have the locations of latches 3 through 16 but I'm lacking the locations of the two forward-most latches.
Thanks, your coordinates agrees with the one I have found for latches 3-16. You don't happen to have the Yo coordinates for the inboard edges of the door rib beams? I mean the ones that the latches and passive shear fittings are attached to.
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#3573
by
Fequalsma
on 13 Nov, 2018 23:57
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Yes but I need to go back in to the drawings.
Stand by... OK found them...
At the OML, the starboard (active) PLBD sill beam is Yo = +7.05 inches. The port (passive) PLBD is Yo = -3.94 inches.
F=ma
DaveS, here are the Xo coordinates that I found. How do they compare with yours?
F=ma
602.3, 647.3, 692.3, 737.3
783.6, 828.3, 873.0, 917.7
966.4, 1011.1, 1055.8, 1100.5
1144.2, 1184.2, 1224.2, 1264.2
Does anyone know the Xo locations of the 16 PLBD C/L latches? I have the locations of latches 3 through 16 but I'm lacking the locations of the two forward-most latches.
Thanks, your coordinates agrees with the one I have found for latches 3-16. You don't happen to have the Yo coordinates for the inboard edges of the door rib beams? I mean the ones that the latches and passive shear fittings are attached to.
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#3574
by
DaveS
on 09 Dec, 2018 04:05
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How was the velocity scale of MM103 ASCENT TRAJ 2 handled for HST missions? I'm asking because the scale only goes between 25K and 26K, with the MECO velocity for HST missions going slightly beyond the 26K maximum of the scale. Was it pegged OSH for the last few seconds on those missions or was the scale adjusted for those missions only?
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#3575
by
DMeader
on 11 Dec, 2018 00:08
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Yes it did. Never realized before how heavy were the RCS/OMS systems + their propellants. More or less 1/3 of an orbiter mass by themselves.
Note this is why the program adopted burning the OMS engines for about a minute shortly after SRB sep--improve upmass, reduce on-orbit mass and improve down mass.
If they planned on burning the OMS engines to save weight, why not simply load that much less propellant?
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#3576
by
PahTo
on 11 Dec, 2018 14:29
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If they planned on burning the OMS engines to save weight, why not simply load that much less propellant?
We don't know that they didn't, certainly for specific missions. And there is a difference between "saving weight" and performance.
As well, remember the prop tanks in the OMS pods also supported the aft RCS, so there is more to the equations than one might think. Being able to maneuver and do de-orbit burn(s) are crit1, and of course there are ISS reboosts too.
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#3577
by
mkirk
on 12 Dec, 2018 23:53
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How was the velocity scale of MM103 ASCENT TRAJ 2 handled for HST missions? I'm asking because the scale only goes between 25K and 26K, with the MECO velocity for HST missions going slightly beyond the 26K maximum of the scale. Was it pegged OSH for the last few seconds on those missions or was the scale adjusted for those missions only?
Although I’ve stared at that particular display a million times, after all these years I really don’t remember how that was dealt with. Since the MECO target for Hubble was so close to 26,000 (26,088 fps on STS-125) I believe the Cutoff Bug (CO) was placed right next to the 26. For most of the Space Shuttle Program, until around 2007, the nominal use of that portion of the Trajectory Display was only available in the BFS. In 2007 the OI-32 software update included modified Trajectory displays for the PASS. Up to that point in time, as contradictory as it sounds, a Nominal MECO was monitored by using the BFS displays. The original (pre 2007) PASS version of TRAJ 2 (the 2nd stage display) was really only used for monitoring RTLS Aborts and provided very little useful information for a Nominal Ascent.
The last few seconds prior to MECO that bug would start moving. This usually resulted in a standard call out within the cockpit of “Bug’s Alive”. Crew’s were trained to verify a Nominal MECO by observing that bug stopped at the CO (cutoff) position which approximated the Inertial Velocity target. Simultaneously, they would feel the nearly instantaneous reduction in G forces from 3 to zero. They would also see the Chamber Pressure Meters for all 3 engines drop to 0%, illumination of each of the 3 red Engine Status lights, and illumination of the DAP (digital auto pilot) panel lights.
Side note: I seem to remember that because of hardware/software limitations, the original version of the display overlay was fixed. And since it was too difficult to change it, we lived with the 25 to 26 on the display even when it wasn’t appropriate. For example, the display was rescaled for TAL MECO velocities during a TAL abort, but the 25 and 26 labels were still there. After the new OI-32 software in 2007, I believe they were able to get rid of that issue. However, as I said earlier I really don’t remember for sure, and I could be talking out of my Butt!
I’ve attempted to attach some screen shots of the original PASS and BFS Displays, followed by a screen shot of the 2 new PASS displays. The original PASS display was essentially the same for both first and second stage. The new versions included a separate first and second stage like the BFS always had.
Mark Kirkman
"Space Shuttle Hugger"
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#3578
by
DaveS
on 16 Dec, 2018 02:34
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Thanks Mark for the detailed answer. Now on to something different: Did Atlantis retain the additional cameras and TCS that was mounted to the External Airlock truss throughout the Shuttle-Mir program until Discovery and Endeavour flew out the program and Atlantis went to Palmdale to ready her for the ISS assembly missions?
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#3579
by
DaveS
on 04 Jan, 2019 11:33
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Does anyone know the MET of Ku band antenna deployment on STS-95?