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#560
by
Jim
on 25 Mar, 2006 16:29
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mong' - 25/3/2006 10:35 AMyes it's a big difference but I am not sure how it could have affected the cost of the system.Granted it would have been lighter (hence less propellant) but the problems would have been the same,i.e: Thermal protection and high turnaround times.
The higher crossrange changed it from a straight wing to a delta. It also caused higher heat loads. Also a heavier return mass (both in vehicle and payload) meant higher heating rates. The TPS may have been easier to develop
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#561
by
mong'
on 25 Mar, 2006 16:41
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okay so it would have made the development and operation of the heatshield easier, hence increased safety.
So if they had developed that smaller orbiter, what would it have been launched with ? a scale down version of the actual stack or more like an inline concept ? (or maybe the flyback booster ?)
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#562
by
Jim
on 25 Mar, 2006 17:18
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mong' - 25/3/2006 11:41 AMokay so it would have made the development and operation of the heatshield easier, hence increased safety.So if they had developed that smaller orbiter, what would it have been launched with ? a scale down version of the actual stack or more like an inline concept ? (or maybe the flyback booster ?)
Flyback was the original intent. It went thru many iterations for many reasons, number 1 being to reduced development costs. There are many books on the development of the shuttle. You can't pin down one thing that caused it to be the way it is.
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#563
by
psloss
on 25 Mar, 2006 20:17
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psloss - 21/3/2006 7:22 AM
...I don't know if they retracted the arm early for the FRF or not, but that's where I remember the issue with the dock seal being mentioned...I've since seen some video of the FRF, but also have to dig it up.
Home for a visit and dug up some video I acquired of the STS-1 FRF and the beanie cap and GOX vent arm was retracted well before T-9 minutes. Looking at some rebroadcast "Today show" video, it looks the arm was retracted by at least dawn, so perhaps it was left off the tank during tanking. Gotta see if I can find the Aviation Week reference now...
Philip Sloss
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#564
by
mkirk
on 26 Mar, 2006 00:27
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psloss - 25/3/2006 3:17 PM
psloss - 21/3/2006 7:22 AM
...I don't know if they retracted the arm early for the FRF or not, but that's where I remember the issue with the dock seal being mentioned...I've since seen some video of the FRF, but also have to dig it up.
Home for a visit and dug up some video I acquired of the STS-1 FRF and the beanie cap and GOX vent arm was retracted well before T-9 minutes. Looking at some rebroadcast "Today show" video, it looks the arm was retracted by at least dawn, so perhaps it was left off the tank during tanking. Gotta see if I can find the Aviation Week reference now...
Philip Sloss
I really dont know what the procedure was for the FRF and the only people I know on the Launch Team from that period are no longer alive. My guess is that given there wasn't really any experience with fueling shuttles yet, they may have felt the vent arm wasn't necessary that late in the count or they may have taken it off early on purpose in order to quantify the formation of ice around the valve.
As for the STS-1 launch itself...although I was just a little kid I still remeber it quite clearly...and I have the tapes of the count now. The arm was retracted just prior to coming out of the T-9 minute hold. This turned out in hind sight not to be a good idea since ice did form and damage the orbiter during launch.
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#565
by
mkirk
on 26 Mar, 2006 00:32
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James (Lockheed) - 23/3/2006 3:17 PM
DaveS - 23/3/2006 2:41 PM
How long does the crew usually image the ET after jettisoning it? Just wondering.
Not sure of how long, but it's restricted from the point of having the flight deck top windows facing the falling tank to when they are out of range for filming, which is by a hand held camera I believe.
There are a couple of photographic events taking palace during external tank separation. At MECO (main engine cutoff) the orbiter/ET stack is in a wings level, heads up position. About 20 seconds after MECO structural separation occurs and the orbiter automatically fires the downward thrusters in order to translate in the –Z direction (in the heads up direction) from the tank. The jets will stop firing once a separation rate of about 4 feet per second is reached. At that point the Commander flying from the left seat will push in and hold the translational controller for about 11 seconds. This is call the +X maneuver and moves the orbiter forward away from the tank by firing the reward firing thrusters. As the +X burn takes place the cameras in the orbiters ET umbilical wells will automatically photograph the tank.
The next photo event is the ET PHOTO MANEUVER. Prior to STS-114 this was more or less an optional event and was performed after the MPS DUMP (main propulsion system dump) via inputs to the control stick by the Commander. It was basically a pitch up (around) maneuver that would put the field of view of the fuel tank in the orbiter’s overhead windows. The MS1 (mission specialist 1) was usually the person with the camera and would call out to the Commander when he/she had the tank in sight. This usually involved a pitch around of 110 degrees, give or take.
After STS-107 when it was decided that ET imagery would be more critical the ET PHOTO MANEUVER was modified so that the orbiter would be closer to the tank during photography. Instead of waiting until after the MPS DUMP, the pitch around is actually a function of the dump itself. The commander places the DAP (digital auto pilot) in a mode that allows the orbiter to freely drift in pitch. As the propellants dump out the engine bells a slight propulsive (about 8 fps of Delta V) pitching moment occurs and the orbiter starts to drift around. The MS calls out to the Commander when he/she visually acquires the tank out the overhead windows and the Commander will stop the pitch movement caused by the dump thru inputs to the control system. Total pitch around is now about 125 degrees.
The crew will take pictures as long as it is useful to do so since the tank is tumbling and moving away from the orbiter. It takes just a few minutes for the entire process.
About the dump:
The MPS DUMP takes place about 2 minutes and 3 seconds after MECO. This is an automatic dump of the residual propellants trapped in the MPS feed lines after MECO. There is on average 4200 lbs of propellant that needs to be dumped overboard to prevent an AFT CG (reward center of gravity) during entry, to prevent spurious venting that could cause navigation errors or contaminate the payloads. There is also a concern that the propellant in the lines could warm and over pressurize the lines causing a rupture. The dump also prevents the trapped LH2 from combining with atmosphere during entry and creating a possibly explosive mixture.
The oxygen is forced out the engine nozzle bells by pressurized helium. The hydrogen is dumped out the LH2 Fill/Drain line on the left side of the orbiter under its own pressure (no helium). Dumping this way helps keep the propellants seperate
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#566
by
psloss
on 26 Mar, 2006 00:55
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mkirk - 25/3/2006 8:27 PM
As for the STS-1 launch itself...although I was just a little kid I still remeber it quite clearly...and I have the tapes of the count now. The arm was retracted just prior to coming out of the T-9 minute hold. This turned out in hind sight not to be a good idea since ice did form and damage the orbiter during launch.
I can't find the reference, but my recollection was of a report of an issue with the dock seal. I don't have the launch day video in front of me, though I can probably find some while I'm here from both launch attempts, but I believe that the tank vented out the cap while the cap was on the tank -- rather than venting out the lines that ran away from the cap -- because the dock seal wasn't working.
Just a historical footnote -- assuming I'm not thinking of something else...on all the subsequent FRFs, the arm was retracted as with a standard count. (And perhaps even the handful of non-FRF wet countdown tests conducted.)
At any rate, I'm becoming more and more envious of some of the video and audio material you have!
Philip Sloss
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#567
by
TheMadCap
on 26 Mar, 2006 16:53
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Jim - 25/3/2006 12:18 PM
mong' - 25/3/2006 11:41 AMokay so it would have made the development and operation of the heatshield easier, hence increased safety.So if they had developed that smaller orbiter, what would it have been launched with ? a scale down version of the actual stack or more like an inline concept ? (or maybe the flyback booster ?)
Flyback was the original intent. It went thru many iterations for many reasons, number 1 being to reduced development costs. There are many books on the development of the shuttle. You can't pin down one thing that caused it to be the way it is.
Remind me, was it the larger payload bay that required the shuttle be loaded on the side of the stack, or was it always planned to have it so? I thought there were early discussions about having it top loaded, a la Apollo CM, which would have eliminated the foam issue?
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#568
by
Jim
on 26 Mar, 2006 18:50
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TheMadCap - 26/3/2006 10:53 AM
Remind me, was it the larger payload bay that required the shuttle be loaded on the side of the stack, or was it always planned to have it so? I thought there were early discussions about having it top loaded, a la Apollo CM, which would have eliminated the foam issue?
It depended on the booster they were looking at time. But payload bay size had nothing to booster mounting.
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#569
by
STS Tony
on 27 Mar, 2006 21:42
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How did they solve the problem with the O-Ring seals after Challenger, did they simply not launch at such low temps?
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#570
by
Chris Bergin
on 27 Mar, 2006 21:46
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STS Tony - 27/3/2006 9:42 PM
How did they solve the problem with the O-Ring seals after Challenger, did they simply not launch at such low temps?
The joints now have a heated layer and a third O-Ring was added, I believe (from memory).
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#571
by
Jim
on 27 Mar, 2006 21:57
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STS Tony - 27/3/2006 3:42 PMHow did they solve the problem with the O-Ring seals after Challenger, did they simply not launch at such low temps?
Also they added a "capture" tang on the segment and a "J" flap in the insulation
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#572
by
DaveS
on 28 Mar, 2006 12:35
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Does anyone know the mass penalty for the orbiter carrying the OBSS? Am I right in assuming it has an mass of around 900-1200 kg?
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#573
by
TheMadCap
on 29 Mar, 2006 02:53
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After Challenger, didn't Max Faget propose a shuttle re-design to something resembling an Energyia? I remember the proposal may have included moving the SSMEs to the ET and replacing the SRMs with liquid boosters. Is this what started the Shuttle C and Z investigations? Anyone have any specifics or further information?
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#574
by
Ender0319
on 29 Mar, 2006 03:14
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It's between 900-1000 lbs including the weight of the MPMs (manipulator positioning mechanisms). That's from my memory on OBSS presentations. I may be off a bit but that's in the ballpark.
DaveS - 28/3/2006 6:35 AM
Does anyone know the mass penalty for the orbiter carrying the OBSS? Am I right in assuming it has an mass of around 900-1200 kg?
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#575
by
Jim
on 29 Mar, 2006 12:41
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TheMadCap - 28/3/2006 8:53 PMAfter Challenger, didn't Max Faget propose a shuttle re-design to something resembling an Energyia? I remember the proposal may have included moving the SSMEs to the ET and replacing the SRMs with liquid boosters. Is this what started the Shuttle C and Z investigations? Anyone have any specifics or further information?
The Shuttle-C configuration (like many SDLV's) go back to before the shuttle even flew. (1970's)
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#576
by
George CA
on 29 Mar, 2006 17:19
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Is it right to say that the RLV design stage goes as far back as just after the start of the Saturn/Apollo era?
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#577
by
TheMadCap
on 29 Mar, 2006 17:39
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Jim - 27/3/2006 3:57 PM
STS Tony - 27/3/2006 3:42 PMHow did they solve the problem with the O-Ring seals after Challenger, did they simply not launch at such low temps?
Also they added a "capture" tang on the segment and a "J" flap in the insulation
Anyone have a diagram or photo of the two types of seal systems they can post?
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#578
by
Jim
on 29 Mar, 2006 17:41
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George CA - 29/3/2006 11:19 AMIs it right to say that the RLV design stage goes as far back as just after the start of the Saturn/Apollo era?
Yes, the early 60's
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#579
by
UK Shuttle Clan
on 30 Mar, 2006 13:30
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Something I've not seen a good image of is where astronauts leave the middeck into the airlock for EVA work. Is there an image of this 'hatch'?