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#2460
by
Jim
on 27 Dec, 2011 16:21
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The shuttle is famous for its four computers running the primary software simultaneously and a fifth running the backup flight software. Was this redundancy ever used? Did one of the four ever fail or disagree during a flight? Was the backup computer ever engaged as a backup?
BFS was never engaged. Look into STS-9 for failures.
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#2461
by
NavySpaceFan
on 27 Dec, 2011 18:12
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Question re: STS-67 Middeck Active Control Experiment (MACE), did MACE have any input into actual ISS hardware (e.g. the CMGs)? Thanks!
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#2462
by
alk3997
on 27 Dec, 2011 20:26
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The shuttle is famous for its four computers running the primary software simultaneously and a fifth running the backup flight software. Was this redundancy ever used? Did one of the four ever fail or disagree during a flight? Was the backup computer ever engaged as a backup?
And, STS-7 for more failures and STS-30. But those were on the older AP-101B computers not on the newer AP-101S. The differences in MTBF were huge. The AP-101B was measured in 1,000s of actual hours MTBF while the AP-101S computers were 10,000s of actual hours (close to 100,000 hours) MTBF. If you work out how many hours of use per flight (including pre-launch and post-landing) you can see why the AP-101S GPC hardware didn't give us much trouble once it replaced the AP-101B.
I worked the STS-30 GPC failure in the MER when it occured which was frantic but the actually replacement of the GPC was slow and methodical.
Remember BFS also had SM capabilities that were not available in the PASS during ascent and entry. So BFS was used every flight, but was never "engaged" - meaning it never took control from PASS.
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#2463
by
DaveS
on 07 Jan, 2012 02:28
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Anyone know what font is used for the MEDS displays like in the one attached?
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#2464
by
Malderi
on 07 Jan, 2012 02:51
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Well, for one thing, I think that's a regular old DEU, not a MEDS screen - but to answer your actual question... I don't know.
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#2465
by
Jorge
on 07 Jan, 2012 03:15
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Well, for one thing, I think that's a regular old DEU, not a MEDS screen - but to answer your actual question... I don't know.
It's a MEDS MDU, specifically AFD1, which replaced the aft ADI. The old DUs had rectangular screens, not square ones, and had no edgekeys. Also, the old DUs had monochrome displays. The MDU is multicolor (with the DPS text in green, edgekey graphics in cyan).
The "font" used on the shuttle screens doesn't really have a name. The old DUs were vector displays and the DEUs would draw the characters stroke-by-stroke. MEDS emulated this behavior, with the IDPs sending vector drawing commands that were interpreted by the MDUs onto their raster displays.
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#2466
by
alk3997
on 07 Jan, 2012 04:59
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Anyone know what font is used for the MEDS displays like in the one attached?
That's a MEDS aft display (MDU). The font was referred to as the "DEU Font". It basically emulated the original DEU's font. The font was originally created by IBM and was very similar to the Tektronics fonts (exactly in many cases) of the era.
BTW, we added 32 characters to the font in 2008. We added a bit that accessed an alternate character set that allowed us to add the Bearing Displays which required some additional characters. We also ended up using color on these final DPS displays (as well as adding an option for entry traj bugs to be in color for three landing sites). Despite adding some color to a few displays, the DPS displays were still referred to as "green screens".
Andy
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#2467
by
sivodave
on 12 Jan, 2012 06:18
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Hi all.
Question on the Orbital DAP, and in particular on the Manual TVC DAP mode. From what I've read till now, in this mode a deflection of the RHC up to the softstop causes to gimbal the OMS engine. If instead the RHC is deflected beyound the softstop, the RCS will be fired continuously.
What I don't understand is, if during this mode, while the RHC is before the softstop, the RCS jets are still fired for keeping the attitude or if instead the RHC deflections are only transformed in OMS engines gimbalining.
Said in other words: is this a mode in which OMS thrust vectoring is accomplished by manual inputs to the OMS engines only or also the RCS is used (I'm always speaking in the case in which the RHC is before the softstop).
Thanks
Davide
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#2468
by
Jorge
on 12 Jan, 2012 07:49
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Hi all.
Question on the Orbital DAP, and in particular on the Manual TVC DAP mode. From what I've read till now, in this mode a deflection of the RHC up to the softstop causes to gimbal the OMS engine. If instead the RHC is deflected beyound the softstop, the RCS will be fired continuously.
What I don't understand is, if during this mode, while the RHC is before the softstop, the RCS jets are still fired for keeping the attitude or if instead the RHC deflections are only transformed in OMS engines gimbalining.
Said in other words: is this a mode in which OMS thrust vectoring is accomplished by manual inputs to the OMS engines only or also the RCS is used (I'm always speaking in the case in which the RHC is before the softstop).
Thanks
Davide
Can't believe how quickly I forget this stuff... had to look up the answer for this.
For 2-engine burns, RHC deflection within the softstop will use OMS steering in all three axes. For single-engine burns, THC deflection within the softstop uses OMS steering in pitch and yaw, RCS in roll. In both cases, if the OMS gimbals lack the control authority to maintain the commanded rate, RCS thrusters will be used to augment the gimbals. This is called RCS wraparound.
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#2469
by
sivodave
on 12 Jan, 2012 08:28
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Can't believe how quickly I forget this stuff... had to look up the answer for this.
ah too bad Jorge! you can't forget this things ahah.
RHC deflection within the softstop will use OMS steering in all three axes
Ok so this means that basically the pilots could manually steer the OMS engines? Where did they get information about which direction they had to steer the OMS engines to? From the ADI?
Thanks
Davide
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#2470
by
Jorge
on 12 Jan, 2012 14:45
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Can't believe how quickly I forget this stuff... had to look up the answer for this.
ah too bad Jorge! you can't forget this things ahah.
RHC deflection within the softstop will use OMS steering in all three axes
Ok so this means that basically the pilots could manually steer the OMS engines? Where did they get information about which direction they had to steer the OMS engines to? From the ADI?
Thanks
Davide
Either the ADI, or the VGOs on the MNVR EXEC display.
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#2471
by
sivodave
on 13 Jan, 2012 16:27
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Hi all.
Did the state vector propagation and scheme change when the IMUs where upgraded to the laser ring system?
If yes what changed?
Thanks
Davide
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#2472
by
Jorge
on 13 Jan, 2012 16:35
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Hi all.
Did the state vector propagation and scheme change when the IMUs where upgraded to the laser ring system?
If yes what changed?
Thanks
Davide
The shuttle IMUs never used ring laser gyros.
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#2473
by
sivodave
on 14 Jan, 2012 07:25
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Sorry i misread what i was reading. The gyros were replaced with the ring laser type.
Another question: which is the difference between the AUTO and INRTL mode for the DAP? I mean, in AUTO the DAP kept the attitude automatically without manual input from the crew, but is not equvalent to say that it maintained an inertial attitude?
Thanks
Davide
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#2474
by
Jorge
on 14 Jan, 2012 07:43
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Sorry i misread what i was reading. The gyros were replaced with the ring laser type.
Either you're still misreading or you're miswriting. The shuttle has never used ring laser gyros in the IMUs, nor the RGAs, nor the SRB RGAs. What's your source for this?
Another question: which is the difference between the AUTO and INRTL mode for the DAP? I mean, in AUTO the DAP kept the attitude automatically without manual input from the crew, but is not equvalent to say that it maintained an inertial attitude?
AUTO puts the universal pointing software in control, which can either maneuver to a designated inertial attitude, track a designated target with a designated body vector, or rotate about a designated body vector. That's in major mode 201. In major mode 202, AUTO enables the automatic maneuver to burn attitude.
INRTL simply snaps and holds the current inertial attitude. Similarly, the LVLH mode simply snaps and holds the current LVLH attitude.
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#2475
by
sivodave
on 14 Jan, 2012 11:16
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Either you're still misreading or you're miswriting. The shuttle has never used ring laser gyros in the IMUs, nor the RGAs, nor the SRB RGAs. What's your source for this?
I was listening to the MIT Open Course Aircraft System lessons. This course is all about the Space Shuttle and every lesson tackle a different subject regarding the on board systems. I was listening the lesson about GNC and there I hear this thing that the IMUs were replaced with the ring laser system. But it's quite likely fault of mine, I must have understoond wrongly. All in all in the Astronaut Training Manual IMU available on L2, there is not mention at all of laser type IMUs.
Thanks very much for the explanations on the differences between AUTO and INRTL DAP modes. That's what I need to know.
Davide
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#2476
by
Robotbeat
on 17 Jan, 2012 22:24
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Sivodave:
You need to edit your quote formatting.
In that MIT OpenCourseware course, at the end, they mentioned different ways that a next-generation Shuttle could be improved compared to the existing Shuttles as part of what the students had to do as part of their grade. It's possible the ring laser gyros were mentioned in that context.
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#2477
by
Namechange User
on 17 Jan, 2012 23:30
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It didn't have to be a "next-generation" shuttle. There were ample ideas and studies performed on many system upgrades and modifications that were never implimented.
The reasons varied of course, from the cost would have been prohibitive to sometimes changing things just to supposedly improve them (when more or less it was working fine or was understood) was not something the always fit within the other confines of the Program.
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#2478
by
Jorge
on 18 Jan, 2012 00:31
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It didn't have to be a "next-generation" shuttle. There were ample ideas and studies performed on many system upgrades and modifications that were never implimented.
The reasons varied of course, from the cost would have been prohibitive to sometimes changing things just to supposedly improve them (when more or less it was working fine or was understood) was not something the always fit within the other confines of the Program.
I remember the proposed SIGI upgrade. Very slick... but the costs of modifying the FSW to work with SIGI caused a lot of people to freak out. The assumption of a stable-platform IMU was pretty deeply baked-into the software. Re-verifying it would have been a bear.
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#2479
by
alk3997
on 18 Jan, 2012 04:15
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It didn't have to be a "next-generation" shuttle. There were ample ideas and studies performed on many system upgrades and modifications that were never implimented.
The reasons varied of course, from the cost would have been prohibitive to sometimes changing things just to supposedly improve them (when more or less it was working fine or was understood) was not something the always fit within the other confines of the Program.
I remember the proposed SIGI upgrade. Very slick... but the costs of modifying the FSW to work with SIGI caused a lot of people to freak out. The assumption of a stable-platform IMU was pretty deeply baked-into the software. Re-verifying it would have been a bear.
Prototype software had been made and we were actually "looking forward" to the challenge. The SIGI was tested onboard using PGSCs to record the data (much as MAGR-S was tested).
SIGI was actually very important from the keep GPCs flying until 2025 plan. We would have off-loaded displays first (CAU) and then off-loaded Nav. This way there would have been enough memory available to keep upgrading GPC flight software through 2025 (if the plan to do that had materialized). Much much cheaper than new GPCs (and software).