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#880
by
Jorge
on 02 Jan, 2010 19:09
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What do the two triangles on the shuttle's HUD (see picture) represent? In the landing videos I've seen, they appear to be fixed at about 20 degrees glideslope; do the triangles indicate the ideal approach glideslope, or are they used for something else?
You're referring to the two horizontal triangles on the sides of the flight director bug? Those are also used as cues for preflare and final flare.
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#881
by
SiameseCat
on 02 Jan, 2010 21:31
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What do the two triangles on the shuttle's HUD (see picture) represent? In the landing videos I've seen, they appear to be fixed at about 20 degrees glideslope; do the triangles indicate the ideal approach glideslope, or are they used for something else?
You're referring to the two horizontal triangles on the sides of the flight director bug? Those are also used as cues for preflare and final flare.
Yes, I was referring to those two triangles. I know they're used for the flare, but what are they used for before the preflare?
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#882
by
brahmanknight
on 06 Jan, 2010 22:06
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I've seen a few posters on this site say something to the effect of "If a human were within 2 miles of the shuttle, the acustics would stop the human heart."
Are there any animals that are killed near the launch site from acustics, not heat?
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#883
by
Ronsmytheiii
on 07 Jan, 2010 03:17
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When the US signed an agreement with Russia on the ISS/Shuttle-Mir campaigns Russia offered to sell the US the Buran docking module for use on the STS, yet the US declined and instead developed their own derived from the existing US internal airlock. The Buran docking system was capable of autonomous dockings yet the US airlock has to utilize a crew of at least five. If the US used the Buran docking system, could it have performed an autonomous docking (or at least lighten the crew work load) and if so why was it not chosen?
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#884
by
Jorge
on 07 Jan, 2010 03:37
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When the US signed an agreement with Russia on the ISS/Shuttle-Mir campaigns Russia offered to sell the US the Buran docking module for use on the STS, yet the US declined and instead developed their own derived from the existing US internal airlock.
That is not quite correct. The US did purchase (and continues to purchase) the APAS docking mechanism developed for Buran, and simply adapted it to the existing US airlock and a new US-developed truss structure to form the Orbiter Docking System (ODS).
The Buran docking system was capable of autonomous dockings yet the US airlock has to utilize a crew of at least five. If the US used the Buran docking system, could it have performed an autonomous docking (or at least lighten the crew work load)
No. The Kurs system included with the Buran docking system was not compatible with the GNC systems on the shuttle and it would have taken a lot of time and money to make them compatible. The top-level program goal was a Shuttle-Mir docking in 1995 and it simply would not have been possible in the constrained budget environment.
and if so why was it not chosen?
The above plus:
The truss on the Buran docking system was not suitable for the shuttle orbiter's payload bay. Buran's trunnion system was designed to take loads in both the longeron and keel trunnions so their truss had only one longeron trunnion pin on each side, with pitch torque being absorbed through the keel. The orbiter's trunnion system is designed to take loads only through the longeron trunnions so it requires two longeron trunnion pins on each side.
The Buran docking system had a telescoping mount to extend the APAS mechanism above the payload bay moldline to improve clearance during docking. This was necessary for Buran since Kurs is not capable of as much precision during docking as a hand-flown docking, so a failed capture can results in much more dispersed bounce-off states. But the mount must retract before the payload bay doors can be closed, or the mechanism jettisoned via pyros. This was deemed unsafe.
The systems in the Buran airlock were not compatible with existing orbiter systems and would have required extensive adaptation. (The systems needed to interface the orbiter power system with the APAS were extensive enough by themselves).
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#885
by
Antares
on 07 Jan, 2010 04:20
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I've seen a few posters on this site say something to the effect of "If a human were within 2 miles of the shuttle, the acustics would stop the human heart."
Tangential question: does anyone have the lethal acoustic levels for a human?
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#886
by
Ronsmytheiii
on 07 Jan, 2010 13:36
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That is not quite correct. The US did purchase (and continues to purchase) the APAS docking mechanism developed for Buran, and simply adapted it to the existing US airlock and a new US-developed truss structure to form the Orbiter Docking System (ODS).
Sorry Jorge, I did know about the APAS I was simply over simplifying, was talking more about the module itself than the docking mechanism.
No. The Kurs system included with the Buran docking system was not compatible with the GNC systems on the shuttle and it would have taken a lot of time and money to make them compatible. The top-level program goal was a Shuttle-Mir docking in 1995 and it simply would not have been possible in the constrained budget environment.
Was there ever any consideration for installing Kurs in between the Mir and ISS programs? I know that there was time in between the two to allow so, however perhaps the US built system could not accommodate it.
The truss on the Buran docking system was not suitable for the shuttle orbiter's payload bay. Buran's trunnion system was designed to take loads in both the longeron and keel trunnions so their truss had only one longeron trunnion pin on each side, with pitch torque being absorbed through the keel. The orbiter's trunnion system is designed to take loads only through the longeron trunnions so it requires two longeron trunnion pins on each side.
Hmm, this was not mentioned in the Energiya-Buran book that I am reading right now that mentioned the offer to sell the Buran Docking system to the US.
The Buran docking system had a telescoping mount to extend the APAS mechanism above the payload bay moldline to improve clearance during docking. This was necessary for Buran since Kurs is not capable of as much precision during docking as a hand-flown docking, so a failed capture can results in much more dispersed bounce-off states. But the mount must retract before the payload bay doors can be closed, or the mechanism jettisoned via pyros. This was deemed unsafe.
The systems in the Buran airlock were not compatible with existing orbiter systems and would have required extensive adaptation. (The systems needed to interface the orbiter power system with the APAS were extensive enough by themselves).
I would have assumed with the US shuttle that the crew would have taken over for the last part of docking, I suppose though that autonomous docking really is not needed on the STS since a crew is required anyhow.
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#887
by
Jorge
on 07 Jan, 2010 15:16
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No. The Kurs system included with the Buran docking system was not compatible with the GNC systems on the shuttle and it would have taken a lot of time and money to make them compatible. The top-level program goal was a Shuttle-Mir docking in 1995 and it simply would not have been possible in the constrained budget environment.
Was there ever any consideration for installing Kurs in between the Mir and ISS programs? I know that there was time in between the two to allow so, however perhaps the US built system could not accommodate it.
No. The budgetary environment never improved.
The truss on the Buran docking system was not suitable for the shuttle orbiter's payload bay. Buran's trunnion system was designed to take loads in both the longeron and keel trunnions so their truss had only one longeron trunnion pin on each side, with pitch torque being absorbed through the keel. The orbiter's trunnion system is designed to take loads only through the longeron trunnions so it requires two longeron trunnion pins on each side.
Hmm, this was not mentioned in the Energiya-Buran book that I am reading right now that mentioned the offer to sell the Buran Docking system to the US.
It probably wasn't a major player in the decision; had the other issues not prevailed, the US probably would have bought the whole thing and then replaced the truss.
I would have assumed with the US shuttle that the crew would have taken over for the last part of docking, I suppose though that autonomous docking really is not needed on the STS since a crew is required anyhow.
That was the thinking, yes, that even if Kurs had been kept it would have been purely as a situational awareness sensor for the crew to use during manual piloting, with all the other Kurs automation features simply not wired into the orbiter GNC. But the US already had options for situational awareness sensors (TCS) that were already developed and cheaper.
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#888
by
Hobbs
on 26 Jan, 2010 20:47
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A few small questions that I just thought about:
1) If the ROFI sparklers failed to ignite at T-10, would this automatically cause an RSLS/GLS abort?
2) how did they find out about the "twang" and impliment it into the launch sequence before STS-1?
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#889
by
Jim
on 26 Jan, 2010 21:17
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A few small questions that I just thought about:
1) If the ROFI sparklers failed to ignite at T-10, would this automatically cause an RSLS/GLS abort?
2) how did they find out about the "twang" and impliment it into the launch sequence before STS-1?
1. yes
2. General engineering sense. Push on a cantilevered object and it is going to move.
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#890
by
nathan.moeller
on 27 Jan, 2010 13:29
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1. yes
2. General engineering sense. Push on a cantilevered object and it is going to move.
I know STS-1 was the only shuttle mission to ever launch after the T0 mark. Did they simply underestimate how long it would take for the vehicle to return to vertical?
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#891
by
ugordan
on 27 Jan, 2010 13:37
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#892
by
nathan.moeller
on 27 Jan, 2010 13:52
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#893
by
Lee Jay
on 27 Jan, 2010 14:06
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You would think so, but it still leaves the question unanswered 
The question being, why didn't it launch at T-0?
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#894
by
nathan.moeller
on 27 Jan, 2010 14:35
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You would think so, but it still leaves the question unanswered
The question being, why didn't it launch at T-0?
Here's what I've always read (someone feel free to correct it if it isn't true) -
The SSMEs lit around T-4 seconds instead of T-6.6 seconds like they do today because it was thought that the vehicle would be vertical after those four seconds. When it wasn't vertical at the intended T0, the guidance didn't allow the SRBs to fire because they wouldn't be flying straight up as intended (I know it's not perfectly straight anyway but you get the idea). When it finally returned to vertical a second or two after the T0 mark, the SRBs lit and off she went.
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#895
by
Jim
on 27 Jan, 2010 15:08
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The countdown was set up for SSME start at T-4. When the timing of the twang was determined (6 seconds), the countdown development was too far along to change, so SRB ignition was set at T+2 sec (the guidance has nothing to do with it) . The countdown was updated for later launches.
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#896
by
nathan.moeller
on 27 Jan, 2010 15:19
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The countdown was set up for SSME start at T-4. When the timing of the twang was determined (6 seconds), the countdown development was too far along to change, so SRB ignition was set at T+2 sec (the guidance has nothing to do with it) . The countdown was updated for later launches.
Thanks for the clarification, Jim. That makes a lot more sense.
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#897
by
anik
on 27 Jan, 2010 15:35
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Quote from STS-2 press kit related to STS-1 two T-0s: "STS-1 had two T-0s, one at the estimated main engine 90 percent thrust time and the second at planned SRB ignition. The STS-2 countdown has been adjusted so that there is only one T-0"
Image from STS-1 press kit.
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#898
by
Antares
on 28 Jan, 2010 03:23
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Regarding twang, does anyone have a graph of the displacement from one of the FRFs? Just curious what the cycles look like and how quickly it dissipates. Maybe a request for L2 Historical....
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#899
by
AnalogMan
on 28 Jan, 2010 15:25
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Regarding twang, does anyone have a graph of the displacement from one of the FRFs? Just curious what the cycles look like and how quickly it dissipates. Maybe a request for L2 Historical....
The graph below shows twang displacement of the STS-26 shuttle stack at the RH SRM igniter position.
This was a heavily instrumented flight for the redesigned SRBs (as you might imagine) with the displacement derived from the strain gauge and accelerometer sensor data.
I have marked the approximate times that the SSMEs start and the SRB bolts are released. At rest the tips of the SRBs are displaced from the vertical by just under 3 inches due to the off-center CoG caused by the orbiter mass. You can see the sway and partial recovery due to SSME thrust before the stack is released - it is less than one cycle for this launch.
