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#440
by
mkirk
on 21 Jun, 2007 13:10
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Gary - 21/6/2007 7:27 AM
mkirk - 21/6/2007 1:22 PM
Typically the commander will take CSS (control stick steering - i.e. manual control) for Roll, Pitch, and Yaw after the orbiter goes subsonic at MACH .9 - this usually occurs at about 4 minutes to go before tocuhdown.
Mark Kirkman
ohhh, I always wondered what CSS meant when it flashed up on the HUD!
Yeah I should also point out that in some mission phases you can take CSS in just a single axis if you want. For example you can take manual control of the pitch axis and allow auto guidance to fly roll and yaw.
Mark Kirkman
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#441
by
Danny Dot
on 21 Jun, 2007 15:17
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whitewatcher - 21/6/2007 4:32 AM
rfoshaug - 21/6/2007 11:17 AM
Why do all shuttle landings from ISS inclination always approach the Cape from the south? I mean, it's probably a desire to avoid flying over land as much as possible (especially after STS-107), but for Edwards it shouldn't make much of a difference if they came in from southwest or northwest? And it would give them twice as many landing opportunities every day.
I guess that the TACAN (similar to VOR/DME) guidance system is only installed on one end of the runway.
It's not easy to land with the shuttle delta wings because you have no flaps and your angle of attack is pretty high, so you can't see to much of the runway. So you rely on a radio landing aids.
TACAN is wide area and not on any end of the runway. I think you are thinking about the Microwave Landing System, MLS. This is on the ends of the runway, but it is on both ends. The direction of approach has little to do with the direction of landing. The shuttle can, and does, approach from the north, but land to the north (from the south). Landing direction is based mainly on the surface winds.
Danny Deger
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#442
by
Kel
on 21 Jun, 2007 16:06
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rfoshaug - 21/6/2007 8:05 AM
Also, the pilot usually (always?) flies part of the HAC to get some experience piloting the shuttle. The commander then takes control again for landing.
I wondered why they passed control of the shuttle back and forth between PLT and CDR - seems like introducing more opportunity for error (as opposed to having one person in control the whole time).
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#443
by
elmarko
on 21 Jun, 2007 16:09
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Quick one, I can't find it in the STS-115 Reentry video thread (which was where it was first brought up)
What model are those egg timers used on the flight deck? My friend wanted to know and I said I'd check.
Edit: FOUND IT! Thanks anyway
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#444
by
mkirk
on 21 Jun, 2007 16:13
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Kel - 21/6/2007 11:06 AM
rfoshaug - 21/6/2007 8:05 AM
Also, the pilot usually (always?) flies part of the HAC to get some experience piloting the shuttle. The commander then takes control again for landing.
I wondered why they passed control of the shuttle back and forth between PLT and CDR - seems like introducing more opportunity for error (as opposed to having one person in control the whole time).
This has been covered somewhere in theses threads, but basically the idea is to give the PLT some stick time. Just a little bit of time to evaluate the handling qualities of the orbiter verses the shuttle mission simulator and the STA (shuttle training aircraft). Rember the PLT will eventually be flying the orbiter for the entire approach as a CDR so even a few seconds of stick time can be of value.
Mark Kirkman
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#445
by
Jorge
on 21 Jun, 2007 18:46
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psloss - 21/6/2007 4:49 AM
rfoshaug - 21/6/2007 5:17 AM
Why do all shuttle landings from ISS inclination always approach the Cape from the south? I mean, it's probably a desire to avoid flying over land as much as possible (especially after STS-107), but for Edwards it shouldn't make much of a difference if they came in from southwest or northwest? And it would give them twice as many landing opportunities every day.
Because they pretty much re-enter on ascending node orbits -- discussed a little bit in the current mission's FD8/9 thread:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=8406&posts=85&mid=151127&highlight=descending+node&highlightmode=2&action=search#M151127
(Earlier in the program, even some high-inclination missions re-entered on descending nodes.)
Update to that - noctilucent clouds aren't the only reason (only applicable during summer). The descending opportunities are generally several hours different from the ascending ones and would typically require sleep-shifting the crew drastically, which is to be avoided.
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#446
by
jackyg
on 21 Jun, 2007 21:24
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Question about the change of altitude, do I understand it correctly that they are flying higher now? And why do they do that.
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#447
by
DaveS
on 21 Jun, 2007 21:31
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jackyg - 21/6/2007 11:24 PM
Question about the change of altitude, do I understand it correctly that they are flying higher now? And why do they do that.
The earlier OA burn was to bring in the first Edwards AFB landing opportunity earlier so it overlaps the second KSC opportunity. This is to land earlier before the winds at Edwards are scheduled to pick-up and go out of limits.
And please, do read the update thread as the info you're looking for is in there.
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#448
by
Chris Bergin
on 21 Jun, 2007 21:32
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jackyg - 21/6/2007 10:24 PM
Question about the change of altitude, do I understand it correctly that they are flying higher now? And why do they do that.
That is correct. They've raised the orbit by a few miles and have increased velocity by 15 feet per second extra.
This is to gain earlier landing opportunities at Edwards Air Force base tomorrow.
See live STS-117 FD14 thread, as this info is there and explained.
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#449
by
jackyg
on 21 Jun, 2007 21:41
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I understand and did reed the threat of FD 14, I read all of the FD threats by the way, but my question is why do they have to fligh higher. So I know it's for an extra oppertunity to land on Edwards, but I don't know why they have to fligh higher.
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#450
by
Danny Dot
on 22 Jun, 2007 00:18
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jackyg - 21/6/2007 4:41 PM
I understand and did reed the threat of FD 14, I read all of the FD threats by the way, but my question is why do they have to fligh higher. So I know it's for an extra oppertunity to land on Edwards, but I don't know why they have to fligh higher.
Raising the orbit makes the time to go around the earth longer. This way Edwards is further east than it would have been, thus closer to the path of the orbiter.
Danny Deger
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#451
by
C5C6
on 22 Jun, 2007 00:39
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a friend asked me and didn't know what to answer: does the SRBs, RCSs and OMSs contaminate the air/atmosphere/water(SRB splashdown) in a significant way? and when the ET deintegrates in the atmosphere???
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#452
by
hyper_snyper
on 22 Jun, 2007 01:04
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#453
by
rfoshaug
on 22 Jun, 2007 08:03
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Sorry if this has been asked before.
Viewing the ground track for the first landing opportunity at Edwards for STS-117 today, it seems to come in a directly northernly heading towards Edwards.
Of course, being a lifting reentry, the Shuttle has quite a bit of crossrange capability. But my question is:
Can the shuttle do a reentry in, say, one long left turn, or does it have to do the roll reversals? For the orbiter itself and heat loads, it shouldn't be a problem (as far as I know it does not sideslip during those turns, so the airflow relative to the orbiter is the same during left and right turns)?
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#454
by
MKremer
on 22 Jun, 2007 08:30
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Roll reversals are almost required.
Let's put it this way - even with close to 100 flights and re-entries, and even before Columbia, don't you think they would have already have done something like that to get an orbiter landed more quickly if it were desired and possible?
And, if not by then, why would they even consider something like that now with the extra emphasis on re-entry safety and other optional emergency landing sites available?
Isn't all this common sense?
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#455
by
jackyg
on 22 Jun, 2007 08:34
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Danny Dot - 22/6/2007 2:18 AM
jackyg - 21/6/2007 4:41 PM
I understand and did reed the threat of FD 14, I read all of the FD threats by the way, but my question is why do they have to fligh higher. So I know it's for an extra oppertunity to land on Edwards, but I don't know why they have to fligh higher.
Raising the orbit makes the time to go around the earth longer. This way Edwards is further east than it would have been, thus closer to the path of the orbiter.
Danny Deger
Thank you Danny , this is the answer i was looking for.
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#456
by
Jim
on 22 Jun, 2007 11:14
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rfoshaug - 22/6/2007 4:03 AM
Can the shuttle do a reentry in, say, one long left turn, or does it have to do the roll reversals? For the orbiter itself and heat loads, it shouldn't be a problem (as far as I know it does not sideslip during those turns, so the airflow relative to the orbiter is the same during left and right turns)?
The air flow is different whether it is a left or right turn
roll reversals are part of the energy management
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#457
by
mkirk
on 22 Jun, 2007 15:33
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rfoshaug - 22/6/2007 3:03 AM
Sorry if this has been asked before.
Viewing the ground track for the first landing opportunity at Edwards for STS-117 today, it seems to come in a directly northernly heading towards Edwards.
Of course, being a lifting reentry, the Shuttle has quite a bit of crossrange capability. But my question is:
Can the shuttle do a reentry in, say, one long left turn, or does it have to do the roll reversals? For the orbiter itself and heat loads, it shouldn't be a problem (as far as I know it does not sideslip during those turns, so the airflow relative to the orbiter is the same during left and right turns)?
The shuttle does roll reversals in order to keep delta azimuth (DELAZ) small, not to bleed off energy as in s-turns.
So what do I mean by that?
First off the shuttle has a small alpha envelope of 3 degrees during entry which means that it can NOT use pitch to control descent rate and drag. Instead the orbiter has to use bank angle. By changing bank angle the descent rate can be increased (because the vertical component of lift is decreased) which means the orbiter falls faster into the denser atmosphere which in turn increases drag.
Since the orbiter is banked this means the nose will begin to track (steer) away from the intended landing site which means DELAZ will increase.
So what is DELAZ?
DELAZ or delta azimuth is the way cross range is displayed to the crew in the cockpit. It is the angle between the orbiters velocity vector (direction of flight) and the landing sight. DELAZ is displayed in the upper right corner of the Trajectory display and by the HSI bearing pointer.
In order to keep DELAZ from getting to big the orbiter reverses the direction of the bank angle – this is called a roll reversal. For example if the orbiter is banked left 45 degrees it will roll to the right until it gets to the new desired roll angle.
For entry the DELAZ is never allowed to become greater than 17.5 Since the nose never steers away from the landing site by very much this means there is no appreciable increase in range to the runway as there would be in an s-turn.
So to summarize the shuttle does roll reversals to keep the runway in front of the nose not to bleed off energy by increasing the range/distance to go to the runway.
Mark Kirkman
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#458
by
mkirk
on 22 Jun, 2007 15:44
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Keeping DELAZ small...
I just came across one of my training workbooks on this subject – which was coincidentally authored by one of the members of this forum “Dany Dot” – and I thought I would quote him verbatim here since his explanation is better than mine.
“In a conventional aircraft cross range (DELAZ) is controlled by turning until the landing site is on the nose then rolling wings level. Pitch is then used to control altitude.
You can’t do this at high Mach in the shuttle. You can’t use pitch to control altitude – remember the small (+/-3 degree) angle of attack envelope. You use bank to control altitude.
Since you always have a little bank (or maybe a lot of bank) to control altitude, the orbiter will always be turning. So, you let the nose of the orbiter fly past the site a little bit – then turn back toward the site. This is called a roll reversal. Cross range control is so easy!
The decision to do a roll reversal is based on DELAZ. Guidance always does the first roll reversal at 10.5 degrees. Guidance does subsequent reversals at 17.5 degrees until below Mach 4. From Mach 4 to 3 guidance ramps the value down from 17.5 to 10.
There is a common misconception that we use roll reversals to bleed off energy; i.e. S-turn. We use drag to bleed off energy. To bleed off energy by turning, we would need to delay turning until DELAZ became large; thus, the range flown would be increased. The small DELAZ that guidance uses does not increase the range flown any significant amount.”
“The concept of using turns to increase the range flown is called S-turns.”
These will be used by the shuttle below Mach 2.5 if the shuttle is high energy.
Mark Kirkman
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#459
by
mdmcgrory
on 22 Jun, 2007 16:12
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Someone asked this on another thread and I think it's an intersting question. What's the maximum duration a space shuttle could achieve in orbit, docked to the ISS or not, with a Spacehab or not. I know that every Shuttle has been retrofitted to draw power from the Station (except Atlantis.) Which allows for about an 18 day flight. But what about the shuttles that had an extended duration orbiter pallet installed? I always heard that could keep them up for 30 days. And I also noticed on an old ISS construction manifest, that an EDO was supposed to be shipped to the ISS. Anybody know what that's about?
