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#120
by
butters
on 03 Jul, 2009 01:42
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With all the focus on the ET/GUCP these days, I was wondering about the power reactant storage and distribution system (PRSD), which stores LH2 and LOX in tanks underneath the payload bay floor for delivery to the fuel cells and cabin atmosphere (and indirectly to the potable water system).
Have there been issues in the past with power reactant loading?
Does the orbiter have a dedicated GH2 vent umbilical for PRSD?
Is the same pad storage/pumping infrastructure used for ET and PRSD?
Why does power reactant loading take place 48 hours before launch?
Are there separate teams of "pad rats" for ET and PRSD cryo ops?
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#121
by
blazotron
on 03 Jul, 2009 02:10
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During NASA TV broadcasts of shuttle launches there is a periodic hissing sound that can be heard before liftoff. These sounds seem to pulse in a regular rhythmic pattern. Can someone explain what the cause of these sounds are?
Because the vehicle has to pass by you to hear the boom. When the shuttle was going to launch from VAFB, it would have passed over the Channel Islands and a boom would have heard. Since the islands were the home of many pinnipeds (seals), there was concern that during the breeding season, a boom would have made the mothers rush for the water causing the pups to be crushed.
Jim, I think you mistakenly copied over the text from the other thread you merged. I believe he is referring to the APU system exhaust.
<edit> Jim answered on the previous page separately
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#122
by
Jim
on 03 Jul, 2009 06:20
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1. Have there been issues in the past with power reactant loading?
2. Does the orbiter have a dedicated GH2 vent umbilical for PRSD?
3. Is the same pad storage/pumping infrastructure used for ET and PRSD?
4. Why does power reactant loading take place 48 hours before launch?
5. Are there separate teams of "pad rats" for ET and PRSD cryo ops?
2. no, the amount of GH2 is very small. The PRSD tanks are super insulated. (there is a vent but no umbilical)
3. No, different tankers are brought in with the LH2 and LO2 for the PDRS. It is a higher quality than the ET prop
4. It is done via an umbilical (OMBUU) in the RSS
5, there are no pad rats for ET loading, it is done from the LCC
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#123
by
elmarko
on 04 Jul, 2009 10:27
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You can get just about anywhere from OPS 0, but OPS 000 PRO is not a legal transition from 304.
However, you can force a GPC to OPS 0 by taking the GPC MODE switch to STBY and back to RUN.
So... you take GPCs 1-4 to STBY, then back to RUN, one at a time. Once you have done this, you will have a GPC common set in OPS 0. The vehicle will not be controllable at this point! Check memory config 3 (ITEM 1+3), should be fine since you used it earlier to transition to OPS 3 the first time around, then invoke the NBAT with OPS 301 PRO. Now the vehicle is under control again.
May need to clean up the BFS afterward. I never certified DPS so not my specialty.
Tried this in the NGSMS this morning... worked. In the middle, I did get paranoid about losing PASS CRT interface and worked around it by taking the CRT1 major function switch to PL, then using one of the remaining PASS GPCs to hard-assign GPC1 to CRT1. (Then of course I had to remember to take CRT1 back to GNC before doing the OPS 301 PRO). As expected, the BFS went standalone when the PASS set went away. Probably broke every one of the "good DPS habits" in the process, but I did get back to 301.
Thanks for trying this, I hope you didn't spend too much time off the back of someone's forum query.
Why would you lose the interface? And what would taking the major function switch to PL do to resolve that? After reading the workbook I saw that taking the switch to PL keeps it in the current major function, but switches to SPEC 0 (I think?) - was that just so you could work on GPC MEMORY?
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#124
by
wizard
on 04 Jul, 2009 16:02
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On Bill Harwood's ascent timeline, what does the 23K line mean?
7:47:20 PM...T+07:47...LAST 1E PRE-MECO TAL ZARAGOZA ([email protected]%)......15,342
7:47:25 PM...T+07:52...23K...........................................15,683
7:47:25 PM...T+07:52...LAST 3E PRE-MECO TAL ZARAGOZA (67%)...........15,683
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#125
by
GLS
on 04 Jul, 2009 17:13
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On Bill Harwood's ascent timeline, what does the 23K line mean?
7:47:20 PM...T+07:47...LAST 1E PRE-MECO TAL ZARAGOZA ([email protected]%)......15,342
7:47:25 PM...T+07:52...23K...........................................15,683
7:47:25 PM...T+07:52...LAST 3E PRE-MECO TAL ZARAGOZA (67%)...........15,683
That's 23000 feet per second. It's about 30 seconds before MECO with 3 SSMEs.
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#126
by
Jorge
on 04 Jul, 2009 18:01
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You can get just about anywhere from OPS 0, but OPS 000 PRO is not a legal transition from 304.
However, you can force a GPC to OPS 0 by taking the GPC MODE switch to STBY and back to RUN.
So... you take GPCs 1-4 to STBY, then back to RUN, one at a time. Once you have done this, you will have a GPC common set in OPS 0. The vehicle will not be controllable at this point! Check memory config 3 (ITEM 1+3), should be fine since you used it earlier to transition to OPS 3 the first time around, then invoke the NBAT with OPS 301 PRO. Now the vehicle is under control again.
May need to clean up the BFS afterward. I never certified DPS so not my specialty.
Tried this in the NGSMS this morning... worked. In the middle, I did get paranoid about losing PASS CRT interface and worked around it by taking the CRT1 major function switch to PL, then using one of the remaining PASS GPCs to hard-assign GPC1 to CRT1. (Then of course I had to remember to take CRT1 back to GNC before doing the OPS 301 PRO). As expected, the BFS went standalone when the PASS set went away. Probably broke every one of the "good DPS habits" in the process, but I did get back to 301.
Thanks for trying this, I hope you didn't spend too much time off the back of someone's forum query.
Nah. Had a student no-show for a class (and brain fart, it was in the NGSST, not the NGSMS, but the software is the same...) so I had the time and the facility was set up... took about five minutes.
Why would you lose the interface?
When you take a GPC driving a CRT to STBY, you get the Big X/Poll fail on that CRT and you can no longer type to it. After I'd done that to GPCs 1 and 2, I started getting paranoid about what would happen after I took GPCs 3 and 4 down.
And what would taking the major function switch to PL do to resolve that? After reading the workbook I saw that taking the switch to PL keeps it in the current major function, but switches to SPEC 0 (I think?) - was that just so you could work on GPC MEMORY?
Because I vaguely recalled (again, not a DPS specialist) that PL is how you signal that you want to type to an OPS 0 GPC. That didn't get rid of the Big X/Poll fail, but the hard-assign did.
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#127
by
mmeijeri
on 04 Jul, 2009 18:09
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From what I've seen you guys say and from what I've seen in online documentation, the Shuttle flight software UI is very, very primitive. This is perfectly understandable given its age, but I was wondering: is it considered to be difficult to upgrade the flight software or is it just something you wouldn't want to do given the amount of work needed for validation and verification and given that it would mean throwing away the flight record? Have you ever had the opportunity to look at the source code? What does it look like?
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#128
by
vertical
on 04 Jul, 2009 18:49
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From what I've seen you guys say and from what I've seen in online documentation, the Shuttle flight software UI is very, very primitive. This is perfectly understandable given its age, but I was wondering: is it considered to be difficult to upgrade the flight software or is it just something you wouldn't want to do given the amount of work needed for validation and verification and given that it would mean throwing away the flight record?
I think it's a matter of if it ain't broke... Reliability and the least amount of question marks has always been the priority in software used in human spaceflight. Besides, even if there was a will to upgrade already working software, probably wasn't much of a budget for it.
I believe for docking, the crew heavily relies on laptops. Do any of these actually interface directly with on board shuttle systems? Or is the crew just acting as the end of the guidance loop and manually maneuvering the orbiter in response to what they see on the laptops?
I wonder what the software on Orion will look like. Will it be a purpose built language or an "off the shelf" commercial language? Significant parts of the Mars Rover use C++ IIRC.
vertical
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#129
by
Jorge
on 04 Jul, 2009 18:59
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From what I've seen you guys say and from what I've seen in online documentation, the Shuttle flight software UI is very, very primitive. This is perfectly understandable given its age, but I was wondering: is it considered to be difficult to upgrade the flight software or is it just something you wouldn't want to do given the amount of work needed for validation and verification and given that it would mean throwing away the flight record?
I think it's a matter of if it ain't broke... Reliability and the least amount of question marks has always been the priority in software used in human spaceflight. Besides, even if there was a will to upgrade already working software, probably wasn't much of a budget for it.
I believe for docking, the crew heavily relies on laptops. Do any of these actually interface directly with on board shuttle systems?
They receive data from shuttle systems via the PCMMU. They cannot send commands to the orbiter.
Or is the crew just acting as the end of the guidance loop and manually maneuvering the orbiter in response to what they see on the laptops?
Yes.
I wonder what the software on Orion will look like. Will it be a purpose built language or an "off the shelf" commercial language? Significant parts of the Mars Rover use C++ IIRC.
Largely Matlab, machine-translated into C.
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#130
by
Jorge
on 04 Jul, 2009 19:13
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From what I've seen you guys say and from what I've seen in online documentation, the Shuttle flight software UI is very, very primitive. This is perfectly understandable given its age, but I was wondering: is it considered to be difficult to upgrade the flight software or is it just something you wouldn't want to do given the amount of work needed for validation and verification and given that it would mean throwing away the flight record? Have you ever had the opportunity to look at the source code? What does it look like?
There is a large part of "if it ain't broke, don't fix it" involved, as Vertical stated. The software testing process is extensive (and expensive); you don't go through that pain unless you need to.
There are also the limitations of the platform. The AP-101S has the equivalent of 1MB memory (actually 256K 32-bit words). The development platform is an IBM System/360 (AP-101S is binary-compatible with it). The development tools are primitive; the skills required to use it, very specialized. Not a whole lot of room to add more code, either. Upgrading shuttle software requires an attention to code size and speed that is no longer a factor in commercial development. Not exactly IT skills that can be hired off the street.
The user interface could be improved by moving development off the GPCs. That was the idea behind the Cockpit Avionics Upgrade (CAU), in which the MEDS "glass cockpit" IDPs would be replaced with CDPs containing more computing capability and a more modern development platform. The GPCs would send data to the CDPs that would be used to draw more modern displays. However, CAU was cancelled after the retirement of the shuttle was announced.
The shuttle flight software is coded in HAL/S, which is somewhat similar in syntax to Fortran. Google around and you'll see some code samples.
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#131
by
DaveS
on 05 Jul, 2009 09:06
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#132
by
elmarko
on 05 Jul, 2009 16:13
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Why would you lose the interface?
When you take a GPC driving a CRT to STBY, you get the Big X/Poll fail on that CRT and you can no longer type to it. After I'd done that to GPCs 1 and 2, I started getting paranoid about what would happen after I took GPCs 3 and 4 down.
And what would taking the major function switch to PL do to resolve that? After reading the workbook I saw that taking the switch to PL keeps it in the current major function, but switches to SPEC 0 (I think?) - was that just so you could work on GPC MEMORY?
Because I vaguely recalled (again, not a DPS specialist) that PL is how you signal that you want to type to an OPS 0 GPC. That didn't get rid of the Big X/Poll fail, but the hard-assign did.
I presume you did this on CRT3 by switching one of the keypads over to it?
This is really fascinating, I wish I had a nice big simulator to try things on.
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#133
by
robertross
on 05 Jul, 2009 16:38
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Question: all the costs incurred with GUCP, FCV & other similar issues. Are these part of the shuttle funding budget, or does these result in a budget shortfall which means deleted something, deffering until later, or requesting additional funds in a future budget to make up the losses?
I know they can't run a deficit, so the 'losses' have to be made up from somewhere.
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#134
by
Jorge
on 05 Jul, 2009 19:04
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Why would you lose the interface?
When you take a GPC driving a CRT to STBY, you get the Big X/Poll fail on that CRT and you can no longer type to it. After I'd done that to GPCs 1 and 2, I started getting paranoid about what would happen after I took GPCs 3 and 4 down.
And what would taking the major function switch to PL do to resolve that? After reading the workbook I saw that taking the switch to PL keeps it in the current major function, but switches to SPEC 0 (I think?) - was that just so you could work on GPC MEMORY?
Because I vaguely recalled (again, not a DPS specialist) that PL is how you signal that you want to type to an OPS 0 GPC. That didn't get rid of the Big X/Poll fail, but the hard-assign did.
I presume you did this on CRT3 by switching one of the keypads over to it?
Yes, then switching CRT3 to PASS (it had previously been displaying BFS).
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#135
by
Danny Dot
on 11 Jul, 2009 14:09
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This may have been asked before, but how long can they leave the external tank full?
After the SSMEs light, about 8.5 minutes
Time on the pad is limited by crew time on their backs. But this is an ISS mission, so the launch window will close first.
Danny Deger
Please accept my apologies in advance for the dripping sarcasm.
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#136
by
oxford750
on 11 Jul, 2009 15:05
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Hi folks,
Are there any photos of the OMBUU as I would like to know what it is, and what it does?
thanks
Carl
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#137
by
Jim
on 11 Jul, 2009 16:12
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#138
by
oxford750
on 11 Jul, 2009 18:13
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Thanks for the quick response Jim, but it seems to be in L2 which I am not a member of.
Thanks
Oxford750
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#139
by
Jim
on 11 Jul, 2009 18:18
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Thanks for the quick response Jim, but it seems to be in L2 which I am not a member of.
Thanks
Oxford750
It is uses to fill the reactants (LH2 and LO2) for the fuel cells, days before launch. The name describes the rest
