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#460 by Danny Dot on 22 Jun, 2007 16:27
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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 could do an entry without a roll reversal, but the flight rules do not allow for it. If the cross range is so high a roll reversal is not performed by Mach 6 (I think it is Mach 6), in the prelanding simulation, the profile is No Go. Not allowing a no reversal entry is a way to make sure there is margin in cross range control. It is equivalent to an airplane to have a reserve in the fuel needed to make an airfield.
Danny Deger -
#461 by Danny Dot on 22 Jun, 2007 16:37
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mkirk - 22/6/2007 10:44 AM
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.
snip
I think your way of saying it is just as good as mine. I am glad to see NASA has not reverted back to the phrase: "The shuttle does roll reversals to bleed off energy". Most shuttle pilots were at one time a fighter pilot. In fighter combat, turning was done to increase range flown and not over shoot a adversary going slower than you. Roll reversals in the shuttle were "assumed" to be the same, but they are not. Keep up the good work!!!
Danny Deger -
#462 by Danny Dot on 22 Jun, 2007 16:43
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mdmcgrory - 22/6/2007 11:12 AM
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?
Are you talking normal operations or an emergency powerdown for something like waiting for a rescue mission to come up and save a crew in a crippled orbiter. I think I read that if the leading edge damage on Columbia had been found early, they could have stayed up for a month. The limiting factor was the CO2 removal canisters. Take this with a grain of salt, I am going from memory here.
Danny Deger -
#463 by Danny Dot on 22 Jun, 2007 16:45
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Does anyone know how short STS-37 landed? I thought it was 1,600 feet, but have been told on sci.space.shuttle it was 600 feet. The difference is enough to say if the landing had been at KSC the crew would have lived or not.
Danny Deger -
#464 by mdmcgrory on 22 Jun, 2007 16:53
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QUOTE] Are you talking normal operations or an emergency powerdown for something like waiting for a rescue mission to come up and save a crew in a crippled orbiter. I think I read that if the leading edge damage on Columbia had been found early, they could have stayed up for a month. The limiting factor was the CO2 removal canisters. Take this with a grain of salt, I am going from memory here. Danny Deger[/QUOTE]
I was thinking of a long duration science mission. The shuttle was supposed to be everythng to everybody, and I guess the EDO kit filled the limited time on orbit space station role. I know STS-50 flew with one. I don't know off-hand how long they stayed up.
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#465 by mdmcgrory on 22 Jun, 2007 16:55
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And I read where Columbia still had her's installed on 107.
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#466 by mdmcgrory on 22 Jun, 2007 17:01
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Ok, Endeavour & Columbia had the EDO kits installed. I don't know if Endeavour's was yanked during it's OMP. But it looks like they were gunning for 16-day Spacelab missions. Not quite 30 days like I thought.
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#467 by mkirk on 22 Jun, 2007 17:08
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Danny Dot - 22/6/2007 11:45 AM
Does anyone know how short STS-37 landed? I thought it was 1,600 feet, but have been told on sci.space.shuttle it was 600 feet. The difference is enough to say if the landing had been at KSC the crew would have lived or not.
Danny Deger
I just looked it up in the SODB and the number in there is 623 feet.
The public link is here;
http://www.spaceflight.nasa.gov/shuttle/reference/green/
Select "landing deceleration" to get the touchdown distance from the threshold. There should be a big fat negative sign in front of that number...
In all my time at JSC I don't recall ever hearing about the landing short of the runway story. After reading your post on that I asked around and looked it up for myself.
Even if it was 623 feet instead of 1623 feet that is still unacceptable as hell and I can't believe that the program let themselves get cornered like that.
Also as you know we target 2500 feet down the runway as the touchdown point...that means the error was over 3100 feet...
Not cool!
Mark Kirkman -
#468 by hawkeye9797 on 22 Jun, 2007 17:17
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I was just wondering if one oms engine were to fail for some reason would one engine be enough for deorbit? Could it just be burned longer?
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#469 by psloss on 22 Jun, 2007 17:37
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mdmcgrory - 22/6/2007 1:01 PM
FYI, some more data:
Ok, Endeavour & Columbia had the EDO kits installed. I don't know if Endeavour's was yanked during it's OMP. But it looks like they were gunning for 16-day Spacelab missions. Not quite 30 days like I thought.
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=1892&posts=6#M25964
http://www.nasa.gov/mission_pages/shuttle/launch/extend_duration.html
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#470 by mkirk on 22 Jun, 2007 17:39
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hawkeye9797 - 22/6/2007 12:17 PM
I was just wondering if one oms engine were to fail for some reason would one engine be enough for deorbit? Could it just be burned longer?
Yes they can "downmode" to a single engine burn and if both OMS engines were not available then they can downmode to RCS jets.
Mark Kirkman -
#471 by dawei on 22 Jun, 2007 19:01
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Pre-entry forward RCS prop dump = fire the thrusters to burn the fuel or simply open valves to allow prop to vent overboard?
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#472 by Jim on 22 Jun, 2007 19:10
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dump is a non propulsive burn
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#473 by Antares on 22 Jun, 2007 19:25
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I've heard it said that the STS-37 landing miss was due to the CDR "taking it wide around the HAC." Can anyone confirm?
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#474 by psloss on 22 Jun, 2007 19:31
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Danny Dot - 22/6/2007 12:37 PM
PAO didn't get the memo in time for this entry...
I think your way of saying it is just as good as mine. I am glad to see NASA has not reverted back to the phrase: "The shuttle does roll reversals to bleed off energy". Most shuttle pilots were at one time a fighter pilot. In fighter combat, turning was done to increase range flown and not over shoot a adversary going slower than you. Roll reversals in the shuttle were "assumed" to be the same, but they are not. Keep up the good work!!!
Danny Deger
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#475 by triddirt on 22 Jun, 2007 19:33
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mkirk - 22/6/2007 11:44 AM
Well PAO for STS-117 just said that roll-reversal were used to slow down the shuttle... So we certainly can understand how the misconceptions come around... So It seems like the problem is S-turn does not equal Roll Reversal... To the layman they sound similar but aren't really.
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.
...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 -
#476 by Danny Dot on 22 Jun, 2007 20:16
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psloss - 22/6/2007 2:31 PM
QuoteDanny Dot - 22/6/2007 12:37 PM
PAO didn't get the memo in time for this entry...
I think your way of saying it is just as good as mine. I am glad to see NASA has not reverted back to the phrase: "The shuttle does roll reversals to bleed off energy". Most shuttle pilots were at one time a fighter pilot. In fighter combat, turning was done to increase range flown and not over shoot a adversary going slower than you. Roll reversals in the shuttle were "assumed" to be the same, but they are not. Keep up the good work!!!
Danny Deger
When I was the Entry Training Flow Supervisor from 1993 to 1995, I didn't make any effort to "fix" the PAO. It was hard enough to fix the astronauts and the flight controllers
About the time I was changing the Entry class to remove the words, "The shuttle S-turns to bleed off energy", I saw Hoot Gibson on the Discovery channel saying, "The shuttle S-turns to bleed off energy".
Speaking of PAO, NASA PAO should spend more time explaining what we are seeing in the landing video on NASA TV. I don't work there any more, but maybe the entry PAO people should take the Entry Guidance class and the TAEM class. These two classes would really help PAO explain what is happening to the shuttle on the video. My guess is the PAO people would LOVE to take the class. Flying entry, TAEM, and landing is not that hard. Most people over flare the first couple of times, but make a landing on the second or third try. You really don't need high level flying skills to do it. More details from PAO during TAEM and landing would add a lot to NASA TV.
Danny Deger -
#477 by dawei on 22 Jun, 2007 20:18
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You got that right!
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#478 by Danny Dot on 22 Jun, 2007 20:19
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mkirk - 22/6/2007 12:08 PM
QuoteDanny Dot - 22/6/2007 11:45 AM
Does anyone know how short STS-37 landed? I thought it was 1,600 feet, but have been told on sci.space.shuttle it was 600 feet. The difference is enough to say if the landing had been at KSC the crew would have lived or not.
Danny Deger
I just looked it up in the SODB and the number in there is 623 feet.
The public link is here;
http://www.spaceflight.nasa.gov/shuttle/reference/green/
Select "landing deceleration" to get the touchdown distance from the threshold. There should be a big fat negative sign in front of that number...
In all my time at JSC I don't recall ever hearing about the landing short of the runway story. After reading your post on that I asked around and looked it up for myself.
Even if it was 623 feet instead of 1623 feet that is still unacceptable as hell and I can't believe that the program let themselves get cornered like that.
Also as you know we target 2500 feet down the runway as the touchdown point...that means the error was over 3100 feet...
Not cool!
Mark Kirkman
The error was more than 3100 feet. The touchdown at 630 feet short was at 165 knots. If he had touched down on air speed, he would have been even shorter than 630 feet.
Danny Deger -
#479 by Danny Dot on 22 Jun, 2007 20:24
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triddirt - 22/6/2007 2:33 PM
Quotemkirk - 22/6/2007 11:44 AM
Well PAO for STS-117 just said that roll-reversal were used to slow down the shuttle... So we certainly can understand how the misconceptions come around... So It seems like the problem is S-turn does not equal Roll Reversal... To the layman they sound similar but aren't really.
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.
...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
Well put. The shuttle does roll reversals, but does not (normally) do S-turns.
Danny Deger
