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#1520
by
Susan27
on 05 Dec, 2008 13:35
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Thanks again, Mark!
While the orbiter is supersonic the speedbrake is acting as a trim device and is positioned based on Mach number...
Well, I thought the use of the speed-brake aerosurfaces is strictly prohibited above Mach 10...otherwise it could be that they may be damaged due to high loads...Isnt that correct...?
How does that correspond with your answer Mark...or did you mean "acting like a trim device..." only(!)
below Mach 10...?
...From 9000 feet down to about 3000, feet while the shuttle orbiter is on the outer glideslope, the speedbrake will control airspeed (~300 KEAS). Below 3000 it works to control the orbiter’s touchdown point...
I thought that it is the CMD
only(!) who "manually" controls the touchdown point (by giving manual pitch commands that are processed further through the DAP to the elevons-aerosurfaces) by using the CSS at this phase of the final appr...and that the Speed-Brakes in "auto" are controling the appr speed (and
not the touchdown point) during pre-flare/flare-phase, too?
Thanks very much!
KR
Susan
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#1521
by
JayP
on 06 Dec, 2008 14:50
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It landed at the skid strip when the other SCA and an orbiter were in the MDD
Mark Kirkman
Hmm, I never figured they would have had both of them there at the same time.
They could have been doing proficincy / familization training for an SCA crew.
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#1522
by
JayP
on 06 Dec, 2008 14:55
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Arming of the landing gear deploy function occurs as the space shuttle orbiter descends thru 2000 feet. My best guess as to why this doesn’t happen any earlier is waiting protects against inadvertent deployment too early in the approach. The gear essentially act as high drag devices and early deployment could really ruin your day – especially if you were already in a low energy condition. Although unlikely, the gear could be intentionally deployed early in a high energy situation in an effort to increase drag and thus decrease energy.
Deployment is a two pushbutton process (referred to as “Arm, Fire”). The ARM pushbutton, usually actuated by the pilot in the right seat on the commander’s call after passing 2000 feet, will energize the latching relays for the Landing Gear Extend Valves and arm the pyrotechnic initiator controllers for both the nose and main gear.
The DN (Down) pushbutton, usually depressed by the pilot on a call from the commander at 300 feet (+/- 100 feet), will energize the extend valves open allowing hydraulic pressure (from system 1) to the landing gear uplock and strut actuators and also to the nose wheel steering switching valve thus initiating deployment. If the uplock sensors do not detect release of the landing gear within 1 second then the pyrotechnic initiator controllers will fire the pyros to initiate release of the uplock hooks. Although it may not sound like it, this is an oversimplification of the deployment sequence but I think it answers your question.
Mark Kirkman
I know you said you were simplifing things, but this reminded me of something else. I read someware that there is a pyro booster on the nose gear that is fired every time. What is that?
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#1523
by
christra1
on 06 Dec, 2008 18:15
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Thanks again, Mark!
While the orbiter is supersonic the speedbrake is acting as a trim device and is positioned based on Mach number...
Well, I thought the use of the speed-brake aerosurfaces is strictly prohibited above Mach 10...otherwise it could be that they may be damaged due to high loads...Isnt that correct...?
How does that correspond with your answer Mark...or did you mean "acting like a trim device..." only(!) below Mach 10...?
...From 9000 feet down to about 3000, feet while the shuttle orbiter is on the outer glideslope, the speedbrake will control airspeed (~300 KEAS). Below 3000 it works to control the orbiter’s touchdown point...
I thought that it is the CMD only(!) who "manually" controls the touchdown point (by giving manual pitch commands that are processed further through the DAP to the elevons-aerosurfaces) by using the CSS at this phase of the final appr...and that the Speed-Brakes in "auto" are controling the appr speed (and not the touchdown point) during pre-flare/flare-phase, too?
The speedbrake is used below Mach 10 and that is still supersonic.
At 3000ft the speed brake is set (automatically) to a calculated position (around 25 degrees) to allow touchdown at a point 2500ft down the runway. From there on the SB will remain in this position to allow the CDR a stable handling during the flare. At 1750 ft altitude the CDR pre-flares the shuttle, changing its glide slope from the steep 17 to 19 degrees dive to a shallow 1.5 degrees glide slope all the way to touchdown. This shallower approach bleeds off the excess speed used during the initial approach. With weight on wheels the SB opens fully.
Rainer
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#1524
by
mkirk
on 06 Dec, 2008 19:05
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Thanks again, Mark!
While the orbiter is supersonic the speedbrake is acting as a trim device and is positioned based on Mach number...
Well, I thought the use of the speed-brake aerosurfaces is strictly prohibited above Mach 10...otherwise it could be that they may be damaged due to high loads...Isnt that correct...?
How does that correspond with your answer Mark...or did you mean "acting like a trim device..." only(!) below Mach 10...?
...From 9000 feet down to about 3000, feet while the shuttle orbiter is on the outer glideslope, the speedbrake will control airspeed (~300 KEAS). Below 3000 it works to control the orbiter’s touchdown point...
I thought that it is the CMD only(!) who "manually" controls the touchdown point (by giving manual pitch commands that are processed further through the DAP to the elevons-aerosurfaces) by using the CSS at this phase of the final appr...and that the Speed-Brakes in "auto" are controling the appr speed (and not the touchdown point) during pre-flare/flare-phase, too?
Thanks very much!
KR
Susan
My response was based on your initial question that asked about the flight regime below FL800 which is the TAEM (Terminal Area Energy Management ) guidance portion of the shuttle entry – which for nominal end of mission is 82,000 feet and Mach 2.5 (Mach 3.2 for RTLS).
Yes until MACH 10 the speedbrake is closed – in fact the closed command is actually a negative number to ensure a good tight thermal seal – after MACH 10 the speedbrake position is on a fixed schedule that is based on relative velocity and works as a trim device. It provides a slight nose up trim which aids with elevon deflection for adverse yaw, directional stability and rudder effectiveness. Currently 81% is used until MACH 3.2 when it begins to move to 65%. Once the Shuttle is below .95 MACH the Speedbrake will modulate to control energy until on final (around 9 or 10,000) when it begins controlling airspeed.
Beginning at 3000 feet it is working to control the touchdown point as the previous poster (Christra1) just described. However I would like to make a minor correction; guidance will command an initial closed position at 3000 feet and then make another adjustment at 500 feet. These calculations are bases on things such as density altitude, wind speed, weight, aim point, and speedbrake logic setting.
The crew can change the speedbrake logic setting with an ITEM ENTRY to the Horizontal Situation Display on the General Purpose Computers. Options are Nominal, Short Field, and ELS (emergency landing site).
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#1525
by
mkirk
on 06 Dec, 2008 19:07
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It landed at the skid strip when the other SCA and an orbiter were in the MDD
Mark Kirkman
Hmm, I never figured they would have had both of them there at the same time.
They could have been doing proficincy / familization training for an SCA crew.
Actually the time I am thinking of involved Columbia and Atlantis, one was returning to KSC after a west coast landing and the other was coming back from Depot at Palmdale. I was there (at the skid strip and SLF), I just don't remember exactly when it was.
Mark Kirkman
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#1526
by
mkirk
on 06 Dec, 2008 19:12
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I know you said you were simplifing things, but this reminded me of something else. I read someware that there is a pyro booster on the nose gear that is fired every time. What is that?
Yes, this is to ensure proper deployment of the nose gear door and gear in case of high aerodynamic forces.
Mark Kirkman
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#1527
by
psloss
on 06 Dec, 2008 19:24
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Actually the time I am thinking of involved Columbia and Atlantis, one was returning to KSC after a west coast landing and the other was coming back from Depot at Palmdale. I was there (at the skid strip and SLF), I just don't remember exactly when it was.
5 March 2001; I think this was during the STS-102 countdown or thereabouts. Atlantis probably got priority to get it ready for STS-104.
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#1528
by
robertross
on 06 Dec, 2008 21:08
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{snip}
If the uplock sensors do not detect release of the landing gear within 1 second then the pyrotechnic initiator controllers will fire the pyros to initiate release of the uplock hooks. Although it may not sound like it, this is an oversimplification of the deployment sequence but I think it answers your question.
Mark Kirkman
Has there ever been a case when the pyros were required to release the uplock hooks?
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#1529
by
mkirk
on 06 Dec, 2008 21:37
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Actually the time I am thinking of involved Columbia and Atlantis, one was returning to KSC after a west coast landing and the other was coming back from Depot at Palmdale. I was there (at the skid strip and SLF), I just don't remember exactly when it was.
5 March 2001; I think this was during the STS-102 countdown or thereabouts. Atlantis probably got priority to get it ready for STS-104.
Yep! Here are a couple of images from the KSC gallery. The first picture is Columbia at the Skid Strip - I'm the guy in the green shirt but apparently in all the excitement I lost my head ...
The second picture is one SCA and Columbia departing the Skid Strip after the other SCA was removed from the SLF and Atlantis had been taken to the OPF.
Mark Kirkman
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#1530
by
mkirk
on 06 Dec, 2008 21:40
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{snip}
If the uplock sensors do not detect release of the landing gear within 1 second then the pyrotechnic initiator controllers will fire the pyros to initiate release of the uplock hooks. Although it may not sound like it, this is an oversimplification of the deployment sequence but I think it answers your question.
Mark Kirkman
Has there ever been a case when the pyros were required to release the uplock hooks?
Did it all the time in the sim as a result of various failures (particularly hydraulic system 1) but I really don't recall anyone needing to do it for real in flight. I'll have to double check.
Mark Kirkman
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#1531
by
psloss
on 06 Dec, 2008 22:34
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Has there ever been a case when the pyros were required to release the uplock hooks?
Did it all the time in the sim as a result of various failures (particularly hydraulic system 1) but I really don't recall anyone needing to do it for real in flight. I'll have to double check.
Mark Kirkman
Not an answer, but this was discussed during STS-121 when there was talk of "safing" APU-1 (here's a nice post from Mark at the time):
http://forum.nasaspaceflight.com/index.php?topic=3344.msg49522#msg49522Going back a little ways, the only mission I recall re-entering and landing on two APUs was STS-79; however, the APU that was declared failed was APU-2.
Edit: there have been other cases like STS-90, where an APU was started "late" -- a few minutes before touchdown. (In that case, APU-3 was having problems with cooling, so that would have been another case that didn't affect deploying the landing gear.)
Would be interested to hear if there are any cases of this...
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#1532
by
tva
on 08 Dec, 2008 07:59
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Chris mentioned "ascent performance margin" in his lates article "STS-130: Endeavour’s Early 2010 Mission to Deliver Node-3".
Why is there any "seasonal" variation ie. "winter vs. summer ?
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#1533
by
The-Hammer
on 08 Dec, 2008 08:28
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For one thing: It's colder in the Winter than in the Summer. Cold air is denser than hot air, thus requiring more effort to accelerate through it.
I'm certain there's more to it than that, though.
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#1534
by
Jim
on 08 Dec, 2008 10:44
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Chris mentioned "ascent performance margin" in his lates article "STS-130: Endeavour’s Early 2010 Mission to Deliver Node-3".
Why is there any "seasonal" variation ie. "winter vs. summer ?
Bulk temperature of the SRB's
Upper level winds have seasonal patterns
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#1535
by
Eerie
on 11 Dec, 2008 19:06
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What will be the fate of Shuttle Carrier Aircraft after Shuttle retirement?
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#1536
by
Jorge
on 11 Dec, 2008 19:16
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What will be the fate of Shuttle Carrier Aircraft after Shuttle retirement?
Most likely, they will be surplused and wind up back in commercial service. They have a relatively low number of flight hours and many third-world airlines continue to fly even older Boeing jets, like the 707.
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#1537
by
gordo
on 12 Dec, 2008 20:02
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What will be the fate of Shuttle Carrier Aircraft after Shuttle retirement?
One is likely to end up at the museum of flight in Seattle. No idea yet if it will have an orbiter with it!
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#1538
by
robertross
on 12 Dec, 2008 23:58
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What will be the fate of Shuttle Carrier Aircraft after Shuttle retirement?
One is likely to end up at the museum of flight in Seattle. No idea yet if it will have an orbiter with it!
You know, to me that would be a waste of a perfectly good aircraft, especially with the low flight hours as Jorge pointed out. You'd get good money for it. Heck, you could turn it into another AirForce1...there's a better way to preserve it's heritage!
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#1539
by
Aviator
on 13 Dec, 2008 12:33
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Somewhere else on the forum someone made mention that their were no umbilical connections between the Orbiter and the SCA for ferry flights. Is that true? aren't there concerns with thruster temps and other things that can freeze? and what about purge air?
I realize that the orbiter is powered down, but is there an electrical connection (perhaps through the ET plates??) for survival heaters and enough monitoring to make sure its working??
Larry
