Author Topic: Shuttle Q&A Part 5  (Read 1542663 times)

Offline Jorge

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Re: Shuttle Q&A Part 5
« Reply #880 on: 01/02/2010 07:09 pm »
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.
JRF

Offline SiameseCat

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Re: Shuttle Q&A Part 5
« Reply #881 on: 01/02/2010 09:31 pm »
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?

Offline brahmanknight

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Re: Shuttle Q&A Part 5
« Reply #882 on: 01/06/2010 10:06 pm »
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? 

Offline Ronsmytheiii

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Re: Shuttle Q&A Part 5
« Reply #883 on: 01/07/2010 03:17 am »
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?

Offline Jorge

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Re: Shuttle Q&A Part 5
« Reply #884 on: 01/07/2010 03:37 am »
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).

Quote
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.

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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).
JRF

Offline Antares

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Re: Shuttle Q&A Part 5
« Reply #885 on: 01/07/2010 04:20 am »
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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Offline Ronsmytheiii

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Re: Shuttle Q&A Part 5
« Reply #886 on: 01/07/2010 01:36 pm »
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.

Quote
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.

Quote
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.

Quote
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.
« Last Edit: 01/07/2010 01:37 pm by Ronsmytheiii »

Offline Jorge

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Re: Shuttle Q&A Part 5
« Reply #887 on: 01/07/2010 03:16 pm »

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.

Quote
Quote
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.

Quote
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.
« Last Edit: 01/07/2010 03:16 pm by Jorge »
JRF

Offline Hobbs

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Re: Shuttle Q&A Part 5
« Reply #888 on: 01/26/2010 08:47 pm »
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?

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #889 on: 01/26/2010 09:17 pm »
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.

Offline nathan.moeller

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Re: Shuttle Q&A Part 5
« Reply #890 on: 01/27/2010 01:29 pm »
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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Online ugordan

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Re: Shuttle Q&A Part 5
« Reply #891 on: 01/27/2010 01:37 pm »
Did they simply underestimate how long it would take for the vehicle to return to vertical?

Wouldn't that have been caught prior to launch, during the FRF?

http://www.myvideo.de/watch/2431762/Columbia_Flight_Readiness_Firing_FRF
« Last Edit: 01/27/2010 01:42 pm by ugordan »

Offline nathan.moeller

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Re: Shuttle Q&A Part 5
« Reply #892 on: 01/27/2010 01:52 pm »
Did they simply underestimate how long it would take for the vehicle to return to vertical?

Wouldn't that have been caught prior to launch, during the FRF?

http://www.myvideo.de/watch/2431762/Columbia_Flight_Readiness_Firing_FRF

You would think so, but it still leaves the question unanswered ;)
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Offline Lee Jay

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Re: Shuttle Q&A Part 5
« Reply #893 on: 01/27/2010 02:06 pm »
You would think so, but it still leaves the question unanswered ;)

The question being, why didn't it launch at T-0?

Offline nathan.moeller

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Re: Shuttle Q&A Part 5
« Reply #894 on: 01/27/2010 02:35 pm »
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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Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #895 on: 01/27/2010 03:08 pm »
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.

Offline nathan.moeller

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Re: Shuttle Q&A Part 5
« Reply #896 on: 01/27/2010 03:19 pm »
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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Offline anik

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Re: Shuttle Q&A Part 5
« Reply #897 on: 01/27/2010 03:35 pm »
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.
« Last Edit: 01/27/2010 03:38 pm by anik »

Offline Antares

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Re: Shuttle Q&A Part 5
« Reply #898 on: 01/28/2010 03:23 am »
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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Offline AnalogMan

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Re: Shuttle Q&A Part 5
« Reply #899 on: 01/28/2010 03:25 pm »
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.

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