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#240
by
Jim
on 19 Apr, 2007 12:19
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Both but autoland has never been used
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#241
by
spaceshuttle
on 19 Apr, 2007 16:02
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Any specific reason why the tanks for the first ISS/SLWT missions (STS-91, 95, 88, 93, 101, etc.) had dashes on the nose, or why some tanks have rings going around the nose (STS-111, -31, etc.)?
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#242
by
Jorge
on 19 Apr, 2007 16:45
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ANDY_WALLACEGROVE - 19/4/2007 7:16 AM
Can someone enlighten me as to whether the microwave landing system noted in the presskit of STS1 (see below) is used for guidance (radar) or control (autopilot).
Strictly speaking, neither. MLS data is processed solely by the navigation software, not guidance or control. NAV uses MLS inputs to a Kalman filter to estimate the Orbiter’s position and velocity state vector relative to the runway. However, the guidance and control software do use the NAV state vector as input, so it could be said that they use MLS data indirectly.
The distinction matters only because there are some sensors that do provide direct inputs to guidance and/or control. For example, the air data probes provide data to all three: corrected pressure altitude to NAV, equivalent airspeed to Guidance, and alpha, Mach, dynamic pressure, and true airspeed to both Guidance and Control (G&C). (Strictly speaking, the probes themselves only provide pressures and temperatures, and the air data Subsystem Operating Program (SOP) derives the above parameters from that and provides them to GNC).
--
JRF
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#243
by
j2_
on 19 Apr, 2007 18:02
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I read in Mike Mullane's book that John Young was vehemently opposed to using the OMS Assist maneuver for safety reasons.
Does anyone know what Young's rationale was for being opposed to what seems so routine today?
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#244
by
edkyle99
on 19 Apr, 2007 18:41
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j2_ - 19/4/2007 1:02 PM
I read in Mike Mullane's book that John Young was vehemently opposed to using the OMS Assist maneuver for safety reasons.
Does anyone know what Young's rationale was for being opposed to what seems so routine today?
Anytime an engine start/stop event takes place, the slight odds of a failure are present. Starting the OMS engines in the midst of the SSME burn complicates the equation, adding a little more risk and creating new abort issues, etc.. My guess is that Mr. Young was simply opposed to the addition of risk during ascent, however small, for the small benefit provided by the burn.
- Ed Kyle
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#245
by
psloss
on 29 Apr, 2007 20:46
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mkirk - 15/1/2007 11:26 AM
P.S.
Last year Craig Covault of Aviation Week and Space Technology sat in on a suited Ascent/Abort sim with the STS-115 crew. He wrote an aritcle about it last fall which gives a good overview of the RTLS profile and a narative of a typical TAL Abort. If you have access to the magazine this will give you some good insight into what a training session is like. He is much better at translating the technical stuff than I am.
Finally got time to find this; the two pieces were in the 21 August 2006 issue and I agree they are very good. Being greedy, I wish Mr. Covault had gotten the print space to do narratives for all four sim cases he sat in on; however, the L2 documentation is a fine substitute.
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#246
by
ANDY_WALLACEGROVE
on 04 May, 2007 15:50
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Question 1: In their seminal (as far a IT geeks are concerned) publication "Transaction Processing Concepts and Techniques", Jim Grey and Andreas Reuter quote "a rule of thumb is that business software costs $10 to $100 per line of code, against $5000 per line of code for the shuttle, the cost differential coming from much more careful design and testing". My question therefore is can anyone direct me to other such statements which highligh the casm between NASA and commercial systems develop is stated. Whilst I am responsible for a "mission critical" system, in my world a major system loss could cost £600billion, whereas in this world it's flesh and bone.
Question 2: My second question (may be worth a differenth thread, ed?), relates to the incident/crisis management practices and procedures used by NASA. Whilst we have based our response on a mode used by the UK Civil Contigencies Secretariat, it would be interesting to know how crisis are managed in other spheres.
Thanks
A
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#247
by
Jim
on 04 May, 2007 15:59
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Shouldn't use the shuttle as an example. The ISS would be better. The shuttle uses unique computers with a unique language (HAL/S). ISS uses COTS hardware and code
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#248
by
ANDY_WALLACEGROVE
on 04 May, 2007 16:12
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Understood, but whilst the hardware is standard the rest ain't. I'm trying to find examples to drive up the level of focus on quality, accuracy and attention to fault tolerant code. There is a cutlure of complacency, and to a degree arrogance, and I want our coders to be mindful that 3 9's (availability) is not real mission critical.
If you suggest ISS, then i'd be glad to take those examples.
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#249
by
ANDY_WALLACEGROVE
on 09 May, 2007 22:12
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With us going full circle back to expendable systems, does any one have a view on whether/how long it will take us to come back to the elegance of winged space flight? I for one (like all of you?) have an affinity for STS, it's something I have had since childhood (I was 7 when I saw the STS-01), and have even booked a pass with Mrs A to travel from the UK see STS125 (rain, hail or shine i'll be there). Which draws me to my conclusion, in light of technological developments on the horizon, be it composites, quantum computing or scramjet, how long will it be before we're back with a beautiful bird?
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#250
by
Marsman
on 09 May, 2007 22:23
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It is much easier and simpler to design a capsule based system. Be it the Apollo cone shape, or biconic whuch provides more cross range capability than the Apollo design. There is essentally no need for wings in space, and the short few minutes that they are used can more easily be subsituded for parachutes or other recovery systems.
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#251
by
Jim
on 09 May, 2007 23:12
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ANDY_WALLACEGROVE - 9/5/2007 6:12 PM
Which draws me to my conclusion, in light of technological developments on the horizon, be it composites, quantum computing or scramjet, how long will it be before we're back with a beautiful bird?
When there is a requirement for it. Maybe never
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#252
by
MKremer
on 09 May, 2007 23:43
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ANDY_WALLACEGROVE - 9/5/2007 6:12 PM
Which draws me to my conclusion, in light of technological developments on the horizon, be it composites, quantum computing or scramjet, how long will it be before we're back with a beautiful bird?
From NASA? Probably not for a long, long time, if ever.
Sometime in the future from the private sector (or some other national space program) would be your only hope. (But again, quite a long time until that may happen.)
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#253
by
spaceshuttle
on 17 May, 2007 17:23
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Lord, could someone PLEASE tell me which external tank was sent through the windtunnel, and which mission it was originally set to fly on?
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#254
by
DaveS
on 17 May, 2007 17:30
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spaceshuttle - 17/5/2007 7:23 PM
Lord, could someone PLEASE tell me which external tank was sent through the windtunnel, and which mission it was originally set to fly on?
What wind tunnel test are referring to? The pre-STS-121 PAL ramp tests? in that case, no ET was used for the tests. All of the tests were with subscale models.
Attached to this post a screen cap from a NASA TV videofile showing the wind tunnel model they used at Ames Research Center in California.
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#255
by
spaceshuttle
on 17 May, 2007 18:39
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DaveS - 17/5/2007 12:30 PM
spaceshuttle - 17/5/2007 7:23 PM
Lord, could someone PLEASE tell me which external tank was sent through the windtunnel, and which mission it was originally set to fly on?
What wind tunnel test are referring to? The pre-STS-121 PAL ramp tests? in that case, no ET was used for the tests. All of the tests were with subscale models.
Attached to this post a screen cap from a NASA TV videofile showing the wind tunnel model they used at Ames Research Center in California.
Oh. Whoops! I thought that STS-114's original tank (I believe that one ended up being ATLANTIS sts-121's tank) was sent somewhere for those test. Clumsy nistake...
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#256
by
programmer78
on 17 May, 2007 19:52
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Question 1: In their seminal (as far a IT geeks are concerned) publication "Transaction Processing Concepts and Techniques", Jim Grey and Andreas Reuter quote "a rule of thumb is that business software costs $10 to $100 per line of code, against $5000 per line of code for the shuttle, the cost differential coming from much more careful design and testing". My question therefore is can anyone direct me to other such statements which highligh the casm between NASA and commercial systems develop is stated. Whilst I am responsible for a "mission critical" system, in my world a major system loss could cost £600billion, whereas in this world it's flesh and bone.
Nasa's system is unlike any commercial software process. Have a read of "They Write the Right Stuff."
http://www.fastcompany.com/online/06/writestuff.htmlDave
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#257
by
joema
on 18 May, 2007 03:45
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programmer78 - 17/5/2007 2:52 PM
...Nasa's system is unlike any commercial software process. Have a read of "They Write the Right Stuff."
http://www.fastcompany.com/online/06/writestuff.html...
That's exactly right -- the shuttle Primary Avionics Software System (PASS) is an example of a Real Time Control System. It's very different from commerical software such as PC operating systems, databases, etc. It's more akin to the flight control software on fly-by-wire airliners and fighter planes.
Real time control systems have a limited number of code lines and global states to deal with. E.g, the PASS system is about 420,000 lines of code, produced by about 260 developers. By contrast, Windows XP (for example) has 40 million lines of code.
The Fastcompany.com article is interesting, but it perpetuates the myth that developers of real time control systems have discovered a secret which allows them to write code with few errors. In reality there is no secret. Real time control systems have few lines of code (relative to much commerical software), and typically 10x or 100x the ratio of developers to lines of code.
The shuttle PASS system is impressive, but so is the software running the fly-by-wire flight controls on the Airbus A380. Both have no manual reversion, and simply must work perfectly.
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#258
by
brahmanknight
on 18 May, 2007 20:30
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I remember reading somewhere that on a future shuttle flight the OBSS will be left at the station. It had something to do with clearance issues with future payloads. When will this happen? How will it be stored on the ISS?
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#259
by
anik
on 18 May, 2007 22:26
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brahmanknight - 19/5/2007 12:30 AM
When will this happen?
OBSS will be left on ISS during STS-123 (1J/A) and returned to Earth aboard STS-124 (1J)...
brahmanknight - 19/5/2007 12:30 AM
How will it be stored on the ISS?
OBSS will be stored on the Orbital Support Equipment (OSE), which will be installed onto S1 truss during STS-118 (13A.1)...