Shuttle Questions Q & A (Part 4)

• #640 by Jim on 20 Feb, 2008 11:32
• I believe those images are from the weather briefing
• #641 by ntschke on 20 Feb, 2008 13:37

• Does anyone have any pics or basic info on what's different in the ISS crewmember return seat?  Besides I believe being in a more horizonal postion and more heavily padded?

• #642 by mkirk on 20 Feb, 2008 14:11
• Quote

  ntschke - 20/2/2008  8:37 AM
  
  

  Does anyone have any pics or basic info on what's different in the ISS crewmember return seat?  Besides I believe being in a more horizonal postion and more heavily padded?

  
  
  I posted the first picture somewhere in the first Shuttle Q&A thread, but here it is again along with another image.
  
  Mark Kirkman
  
  
  

  ---

  

  
• #643 by ntschke on 20 Feb, 2008 14:29
• Great pics, thanks Mark.  I was wondering how they'd get them in a  horizontal position down there.  I like that their feet have a nice snug spot in the locker wall.  
  
  
• #644 by iamlucky13 on 20 Feb, 2008 18:45
• Sorry if any of these are answered in the last 600+ posts...
  
  1.) APU starts happen after the de-orbit burn. Are these things just rock-solid reliable or is there a contingency if they don't have sufficient APU power? I assume they can't abort post-burn.
  
  2.) What's the delta-V for a typical de-orbit burn? This uses the OMS engines so the shuttle faces backwards for this, correct?
  
  3.) Is there a graph anywhere showing accelleration vs either time or altitude during entry...or for that matter, speed vs. altitude?
  
  4.) It always surprises me to see the definite nose-down attitude of the shuttles prior to the flare. Does anyone know the approximate angle of attack (not attitude), say, at 300 knots?
  
  Thanks...looked like a great landing today.
• #645 by kimmern123 on 20 Feb, 2008 18:53
• Quote

  iamlucky13 - 20/2/2008  8:45 PM
  
  Sorry if any of these are answered in the last 600+ posts...
  
  1.) APU starts happen after the de-orbit burn. Are these things just rock-solid reliable or is there a contingency if they don't have sufficient APU power? I assume they can't abort post-burn.
  
  4.) It always surprises me to see the definite nose-down attitude of the shuttles prior to the flare. Does anyone know the approximate angle of attack (not attitude), say, at 300 knots?
  
  Thanks...looked like a great landing today.

  
  1. I think they start one of the APUs prior to the deorbit burn.
• #646 by Jim on 20 Feb, 2008 18:54
• Quote

  iamlucky13 - 20/2/2008  2:45 PM
  
  Sorry if any of these are answered in the last 600+ posts...
  

  
  why didn't you search them to make sure?
• #647 by iamlucky13 on 20 Feb, 2008 21:33
• I skimmed it a little bit and I actually did try a couple searches (after I posted my questions, I admit), but I haven't been able to find the answers yet, and the search function seems to be having trouble at the moment. Right now it's been trying to load a hit for several minutes.
  
  No worries if no one knows, but I was hoping someone does and would enjoy sharing.
• #648 by Jim on 20 Feb, 2008 21:46
• Quote

  iamlucky13 - 20/2/2008  2:45 PM
  
  Sorry if any of these are answered in the last 600+ posts...
  
  1.) APU starts happen after the de-orbit burn. Are these things just rock-solid reliable or is there a contingency if they don't have sufficient APU power? I assume they can't abort post-burn.
  
  2.) What's the delta-V for a typical de-orbit burn? This uses the OMS engines so the shuttle faces backwards for this, correct?
  
  3.) Is there a graph anywhere showing accelleration vs either time or altitude during entry...or for that matter, speed vs. altitude?
  
  4.) It always surprises me to see the definite nose-down attitude of the shuttles prior to the flare. Does anyone know the approximate angle of attack (not attitude), say, at 300 knots?
  
  Thanks...looked like a great landing today.

  
  1.  they can abort post burn (there is a post with more info)
  
  2.  OMS are primary.  They can use 1 OME or RCS as a backup
• #649 by joncz on 20 Feb, 2008 22:29
• Re: aborting deorbit
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=2030&mid=98971#M98971
• #650 by mkirk on 20 Feb, 2008 22:35
• Quote

  iamlucky13 - 20/2/2008  1:45 PM
  
  Sorry if any of these are answered in the last 600+ posts...
  
  1.) APU starts happen after the de-orbit burn. Are these things just rock-solid reliable or is there a contingency if they don't have sufficient APU power? I assume they can't abort post-burn.
  
  2.) What's the delta-V for a typical de-orbit burn? This uses the OMS engines so the shuttle faces backwards for this, correct?
  
  3.) Is there a graph anywhere showing accelleration vs either time or altitude during entry...or for that matter, speed vs. altitude?
  
  4.) It always surprises me to see the definite nose-down attitude of the shuttles prior to the flare. Does anyone know the approximate angle of attack (not attitude), say, at 300 knots?
  
  Thanks...looked like a great landing today.

  
  1.  One APU is started in LOW PRESSURE mode prior to committing to De-Orbit (i.e. prior to the De-Orbit Burn), this gives everyone a warm fuzzy that at least one hydraulic system is up and running prior to coming down.  I had many arguments (friendly of course) with a couple of the MMACS folks (the people in MCC responsible for the system) about the relative merits of that philosophy when the program was looking at switching to electric APUs.  With the electric APUs the plan would have been to start them all after the BURN.  I didn't like that plan much but it was apparently necessary to start them later because of the size of the Batteries that would have been used for the new APUs.
  
  The current APUs are started as late as possible becuase of the relatively small fuel load they carry.  The APU hydraulic system is critical and you need at least one system to safely return to the ground.
  
  Aborting after the START of the Burn is possible and is dependent on the altitude at the time of the systems problem or failure.  During the De-Orbit Burn, Safe HP (altitude of perigee) is the decision boudary and is defined as "the altitude that assures a safe orbit for the space shuttle for at least 24 hours" - typically this is set at 80 nautical miles.  If the orbiter is still above the Safe HP then the burn can be terminated and the problem evaluated.  If you are below this altitude then the Burn is continued.
  
  2.  Delta V for the Burn is of course altitude/velocity dependent but typically in the 200-300 feet per second range.  For today’s burn on STS-122 the Delta V was about 290 feet per second which is roughly 198 miles per hour.  Yes the burn is a tail first - retrograde - burn.
  
  3.  Give me a little time and I can probably dig one out.
  
  4.  For the Space Shuttle, allowable alpha (angle of attack) is a function of MACH Number/Airspeed.  For example in the terminal area (MACH 2.5 at 82,000 feet) it ranges from 6 to 18 degrees.  When the Shuttle is subsonic and on the HAC the MAX L/D (lift over drag) alpha would be about 10.5 degrees.  As you roll out on final alpha is relatively small – generally speaking the crew is focusing more on pitch and airspeed and the visual cues provided by the PAPIs and later by the ball bar.  At touch down the angle of attack is between 8 -14.
  
  Mark Kirkman
  
  P.S.
  Those numbers I provided above are from memory so if someone has better number please feel free to cough them up.
  
  
  
  
• #651 by iamlucky13 on 21 Feb, 2008 00:15

• 1.) That's what I was curious about...so they do prestart one. I guess I misunderstood the start sequence in commenting over in the Flight Day 14 thread to say that all three were started post-burn.
  
  2.) I just noticed the de-orbit burn was listed for Atlantis' landing today at about 2.5 minutes, and after looking up specs on the mass and OMS thrust, my rough math gave the same 290 fps.
  
  3.) I knew NASA had a reference page full of operational details, but I'd been unable to find it until just now. It mentions 33 ft/s^2 after peak heating, but seems to suggest higher rates. I'd still be interested in seeing a graph if you happen to have one handy.

  Here's the NASA shuttle reference in case anyone else hasn't seen it. It looks like there's a couple hundred printed-pages worth of material in there. I thought there were technical drawings last time I found it, but I don't see any now:

  http://www.spaceflight.nasa.gov/shuttle/reference/shutref/
  
  4.) Interesting...Atlantis looked like she was at about a 20 degree attitude in the screen shots in the flight day 14 thread. Add in that 10.5 degree alpha and the glide slope is 30 degrees! A subpage in the link above quoted a 20 degree typical glideslope.

  ---

  
• #652 by Jim on 21 Feb, 2008 00:56
• Quote

  iamlucky13 - 20/2/2008  8:15 PM
  Interesting...Atlantis looked like she was at about a 20 degree attitude in the screen shots in the flight day 14 thread. Add in that 10.5 degree alpha and the glide slope is 30 degrees! A subpage in the link above quoted a 20 degree typical glideslope.

  
  He said10.5  in the HAC and not on final.  He said on final, the  AOA is small
• #653 by Ford Mustang on 21 Feb, 2008 01:32
• What are the doors, and why are they closed preflight, open post-flight?  I'm just wondering, never seen it...?

  ---

  
• #654 by mkirk on 21 Feb, 2008 01:40
• Quote

  iamlucky13 - 20/2/2008 7:15 PM
  
  

  3.) I knew NASA had a reference page full of operational details, but I'd been unable to find it until just now. It mentions 33 ft/s^2 after peak heating, but seems to suggest higher rates. I'd still be interested in seeing a graph if you happen to have one handy.

  Here's the NASA shuttle reference in case anyone else hasn't seen it. It looks like there's a couple hundred printed-pages worth of material in there. I thought there were technical drawings last time I found it, but I don't see any now:

  http://www.spaceflight.nasa.gov/shuttle/reference/shutref/
  
  4.) Interesting...Atlantis looked like she was at about a 20 degree attitude in the screen shots in the flight day 14 thread. Add in that 10.5 degree alpha and the glide slope is 30 degrees! A subpage in the link above quoted a 20 degree typical glideslope.

  3.  You can find diagrams out the wazooo at this public link:
  

  http://www.shuttlepresskit.com/STS-105/scom.htm

   

  4.  Alpha (angle of attack) does not work that way.  I thought you asked specifically for angle of attack and not pitch.  Angle of attack - defined as the angle between the wing chord line and the relative wind - is what I was trying to provide.
  

  As for the glideslope, that is weight dependent in the Space Shuttle world.  For heavy weight orbiters (222,000 pounds and above) the glideslope is 20 degrees - in the HUD video you would see two red and two white PAPI lights, lightweight orbiters (less than 222,000) use 18 degrees which equates to three red lights and one white light.  Of course you can also use the pitch ladder symbols on the HUD to determine orbiter pitch.

  As I said the Alpha on final is relatively small for the shuttle.  You can watch the HUD videos from today and guesstimate the approximate angle of attack by taking the cross hair symbol (plus sign) which represents the vehicle's X (longitudinal) body axis and the velocity vector (the circle with two small horizontal lines and one vertical line on the top).  I have no idea how close the X body axis actually is to the shuttle's wing chord line but this will give you a rough idea of what would be happening to Angle of Attck as the orbiter is stabalized on the glideslope.
  

  Mark Kirkman

• #655 by mkirk on 21 Feb, 2008 01:44
• Quote

  Ford Mustang - 20/2/2008  8:32 PM
  
  What are the doors, and why are they closed preflight, open post-flight?  I'm just wondering, never seen it...?

  
  Those are some of the orbiter vent doors.
  
  Actually they are opened and closed thoughout the preflight process and the missions to facilitate purge opertions and manage compartment pressures.
  
  I have provided some more detailed answers about their operation somewhere in these threads but for a quick book answer you can click on the link I provided in the post above and open the pdf chapter labeled MECHANICAL SYSTEMS.
  
  Mark Kirkman
• #656 by Ford Mustang on 21 Feb, 2008 01:50
• Quote

  mkirk - 20/2/2008  9:44 PM
  
  

  Quote

  Ford Mustang - 20/2/2008  8:32 PM
  
  What are the doors, and why are they closed preflight, open post-flight?  I'm just wondering, never seen it...?

  
  Those are some of the orbiter vent doors.
  
  Actually they are opened and closed thoughout the preflight process and the missions to facilitate purge opertions and manage compartment pressures.
  
  I have provided some more detailed answers about their operation somewhere in these threads but for a quick book answer you can click on the link I provided in the post above and open the pdf chapter labeled MECHANICAL SYSTEMS.
  
  Mark Kirkman

  
  Thank you very much for the quick answer.  Never noticed them before, was a little.. eh.. freaked to see some "holes" in the orbiter, then looked at pre-flight images, saw them there.
• #657 by ntschke on 21 Feb, 2008 14:10

• Quote

  ChrisC - 7/2/2008 5:47 PM In today's live STS-122 thread, somebody said:

  Quote

  ... The concern is there are thunderstorms [that] may move into the 20 naut. mile circle of the RTLS SLF zone during the liftoff or at the RTLS time (about 30 - 45 minutes after launch)

  Is the RTLS landing REALLY 30-45 minutes after launch? I can't imagine that they'd be that far away and gliding that long. I am aware of the engine deceleration task that's part of an RTLS abort. Can someone point me to a timeline on that abort sequence? I did some googling/wikipediaing, which only resulted in some vague mentions of 25 minutes and 35 minutes ...

  "Thanks to whichever moderator cleaned the recent clutter of basic questions out of this thread. Affected User Who Will Remain Unnamed, please search this forum a little bit or even Just Google It before posting here. Thanks.
  
  Maybe I'll put links to the FAQ and/or General Q+A forums in my sig "

  Sound familiar? 

  If they're "in orbit" in 8 minutes, why is it surprising that it would take that long to glide back?
  

• #658 by Jim on 21 Feb, 2008 14:29
• Quote

  ntschke - 21/2/2008  10:10 AM
  Maybe I'll put links to the FAQ and/or General Q+A forums in my sig

  
  I used to
• #659 by ntschke on 21 Feb, 2008 14:39

• Not my words.  They're someone else's to an unkown user when said asked a question that wasn't up to par in someone's opinion.

  Jim, any recommendations for a meeting place near KSC next month?  Rusty's, Fishlips?  Would the sterling or other casino cruise go out sunday night for a possible shot of the complex?