Shuttle Questions Q & A (Part 4)

• #260 by pr1268 on 09 Dec, 2007 13:39

• Quote

  cantuezel - 9/12/2007  8:08 AM  At the vid "STS-88: Re-entry video with HUD and audio" between 17:10 min. and 17:30 min CAPCOM transmitts to Endev. that there might be a loss of comm for 7 min (TDRS) during roll-reversal.  Do someone know the reason for that? I thought TDRS nowadays guarantees that there wont be a loss of Comm at all?  Thanks for info!

  My understanding is that the Shuttle can maintain communication with MCC (both telemetry and voice), even during the ionization blackout period of re-entry, because (1) there is a "hole" in the ionization shield trailing above and behind the Shuttle due to its re-entry attitude and (2) the TDRS satellites have been strategically placed to enable such communication for either Edwards or KSC landings.

  But, a comm blackout will still occur if the path between all 4 S-band antennae on the Shuttle and TDRS is blocked.  The antennae are located near the crew cabin, two on the top and two on the bottom of the Orbiter.

  Whenever the Shuttle does a roll maneuver, each antenna's signal might be blocked by the Shuttle's tail fin. The antennae are directional.
  

• #261 by cantuezel on 09 Dec, 2007 14:19

• Thanks!
  

  Quote

  pr1268 - 9/12/2007  3:39 AM

  Whenever the Shuttle does a roll maneuver, each antenna's signal might be blocked by the Shuttle's tail fin. The antennae are directional.
  

  But the roll maneuver to get the shuttle upside down only takes some seconds (not min.) as far as I know. Or do you mean TDRS is not "reachable" during the whole period the shuttle being upside-down? 

   

• #262 by Jim on 09 Dec, 2007 14:31
• Quote

  cantuezel - 9/12/2007  10:19 AM
  
  

  Thanks!
  

  Quote

  pr1268 - 9/12/2007  3:39 AM

  Whenever the Shuttle does a roll maneuver, each antenna's signal might be blocked by the Shuttle's tail fin. The antennae are directional.
  

  But the roll maneuver to get the shuttle upside down only takes some seconds (not min.) as far as I know. Or do you mean TDRS is not "reachable" during the whole period the shuttle being upside-down?

  
  The orbiter does not invert during the roll maneuvers.  The roll reversals are like a skier doing "S" turns down a slope.
   During a roll reversal, the orbiter may hold an attitude for minutes in which the tail blocks the antennas.
• #263 by rocketguy101 on 09 Dec, 2007 14:42
• Quote

  Jim - 9/12/2007 9:31 AM

  Quote

  cantuezel - 9/12/2007 10:19 AM

  Thanks!
  

  Quote

  pr1268 - 9/12/2007 3:39 AM

  Whenever the Shuttle does a roll maneuver, each antenna's signal might be blocked by the Shuttle's tail fin. The antennae are directional.
  

  But the roll maneuver to get the shuttle upside down only takes some seconds (not min.) as far as I know. Or do you mean TDRS is not "reachable" during the whole period the shuttle being upside-down?

   

  The orbiter does not invert during the roll maneuvers. The roll reversals are like a skier doing "S" turns down a slope. During a roll reversal, the orbiter may hold an attitude for minutes in which the tail blocks the antennas.

  See "Roll Schedule" at http://spaceflight.nasa.gov/realdata/groundtracs/dol_pad_faq.html

• #264 by mkirk on 09 Dec, 2007 15:19
• Quote

  DaveS - 8/12/2007  4:59 PM
  
  

  Quote

  cantuezel - 8/12/2007  11:47 PM
  Do you know what this 2 designators at the horz. line are good for?

  Commanded and acrual speedbrake setting. Top is commanded speedbrake setting and bottom is actual speedbrake level.

  
  Actually you have that backwards, the top triangle is showing the actual position of the speddbrake and the bottom arrow is showing commanded position.  Commanded position is what the GPCs are asking for based either on input from the DAP (digital auto pilot) or Speedbrake Handle input from the commander /pilot.
  
  Generally on final approach you will see the speedbrake modulating to maintain an airspeed of 300 knots until 3000 feet at which time guidance will command the speedbrake to retract to a position that manages touchdown energy.  At 500 feet another automatic adjustment is made to further refine touchdown energy.
  
  Mark Kirkman
• #265 by kimmern123 on 09 Dec, 2007 18:12
• How high is the nose normally pitched up at touchdown? I assume this is dependent on the wind conditions?
• #266 by shuttlefan on 10 Dec, 2007 13:30
• Is the ECO sensor issue the biggest mystery in the history of the Shuttle Program?
• #267 by mkirk on 10 Dec, 2007 16:59
• Quote

  kimmern123 - 9/12/2007  1:12 PM
  
  How high is the nose normally pitched up at touchdown? I assume this is dependent on the wind conditions?

  
  Pitch attitude is a function of airspeed (among other variables) and is usually in the 5 to 10 degree range (closer to 10) at touchdown.  You definitely want to keep it below 15 degrees in order to keep from scraping the tail (body flap).
  
  Mark Kirkman
  
• #268 by pr1268 on 10 Dec, 2007 17:48
• Might someone please explain what flow separation is (with respect to rocket engines)?
• #269 by Jim on 10 Dec, 2007 17:52
• http://en.wikipedia.org/wiki/Flow_separation
  
  The flow separates from the nozzle wall because the pressure in the flow is lower than the outside pressure. It happens when the nozzle is too big and the flow is over expanded
• #270 by pr1268 on 10 Dec, 2007 18:21
• What causes the interior of the SSME to appear illuminated in a light blue color?  I thought that LH2/LO2 burned with in invisible flame.  Is the white "flame" visible at the bottom of this image caused by condensing water vapor?  Thanks!
  
  http://en.wikipedia.org/wiki/Image:Shuttle_Main_Engine_Test_Firing.jpg
• #271 by Jim on 10 Dec, 2007 18:40
• Quote

  pr1268 - 10/12/2007  2:21 PM
  
  What causes the interior of the SSME to appear illuminated in a light blue color?  I thought that LH2/LO2 burned with in invisible flame.  Is the white "flame" visible at the bottom of this image caused by condensing water vapor?  Thanks!
  
  

  
  Read the Q&A thread, it has been discussed before.
  
  Shock diamond and it is blue
• #272 by cantuezel on 10 Dec, 2007 21:50
• At the moment I try to deal with the different HUD displays which can be seen while landing the shuttle in the multiple landing videos here at L2. Therefore I read the appropriate parts of the SCOM (2.7. 24 - 2.7.27). Some issues and designators I still dont understand:
  
  On PDF-page  330 (2.7.26):
  
  1. There is a cross called "Boresight". What does that stand for? Is that the direction the vessel is pointing at the moment?
  
  2. On the very right side (at the Altitude bar) there is a "R" designator called "Alt Reference Monitor": WHat Alt target does that designator display, is that the optimal Alt. at the appropriate phase of the approach (TAEM) or the glide slope signal of the MLS?
  
  3. At the center there is the famous diamond, displaying the guidance signal: Is that the direction the GPC (DAP?) is directing the shuttle at the current moment of the flight?
  
  4. Which guidance modes beside of HDG are available?
  
  
  On PDF-page  330 (2.7.27):
  
  5. Concerning the Declutter (what does that stand for?) Level 1 display of the HUD:
  
  A bit difficult to describe but there is the shuttle symbol (with the diamond tail at the top) and on each side the both triangels. I learned that the both triangels display the horizon, is that correct? If so, what does the diamond at the tail stand for or how is the display interpreted correctly?
  
  6. What does the cross "+" at Declutter levels 2 & 3 stand exactly for?
  
  7. In which Declutter mode and at what altitude do the pre flare triangels which command the  preflare pullout appear?
  
  8. I assume that the different (Declutter) modes of the HUD - at least while final approach - will change automatically dependent of the current altitude, is that correct?
  
  Thanks in advance!
  
  Greetings
  
  Can
   
  
  
  
• #273 by thomasafb on 11 Dec, 2007 09:23
• In the Hale message on L2 he is refering to off nominl performance during the STS-78 ascent. Can anyone explain what happened there since i did not find anything about it in Jenkins' nor the IFA list on the JSC site?
  
  Thanks in advance!
• #274 by pr1268 on 11 Dec, 2007 15:47
• ET camera question:
  
  Is it just me or did the first use of the video camera mounted on the ET (STS-112 IIRC) have it mounted much further up the tank compared to recent missions?  Thanks.
  
• #275 by DaveS on 11 Dec, 2007 16:14
• Quote

  pr1268 - 11/12/2007  5:47 PM
  
  ET camera question:
  
  Is it just me or did the first use of the video camera mounted on the ET (STS-112 IIRC) have it mounted much further up the tank compared to recent missions?  Thanks.
  

  Yes. On STS-112 it was located in its own special housing on the LOX tank cable tray. For RTF and subsequent flights, the camera was relocated to inside the LOX feedline fairing on the intertank section.
  
  This to protect the camera from being smudged by the forward Booster Separation Motors on the right SRB.
• #276 by pr1268 on 11 Dec, 2007 16:34

• Quote

  DaveS - 11/12/2007  11:14 AM This to protect the camera from being smudged by the forward Booster Separation Motors on the right SRB.

  Makes perfect sense, now that I've watched the STS-112 ET cam video.  Got really smudgy afte a short while!
  

• #277 by pr1268 on 11 Dec, 2007 16:46

• Quote

  mkirk - 10/12/2007  11:59 AM You definitely want to keep it below 15 degrees in order to keep from scraping the tail (body flap).  Mark Kirkman

  Or to keep it from "poppin' a wheelie," as Jack Lousma did while landing STS-3
  

• #278 by Jim on 11 Dec, 2007 17:41
• Quote

  cantuezel - 10/12/2007  5:50 PM
  
  At the moment I try to deal with the different HUD displays which can be seen while landing the shuttle in the multiple landing videos here at L2. Therefore I read the appropriate parts of the SCOM (2.7. 24 - 2.7.27). Some issues and designators I still dont understand:
  
  On PDF-page  330 (2.7.26):
  
  1. There is a cross called "Boresight". What does that stand for? Is that the direction the vessel is pointing at the moment?
  
  2. On the very right side (at the Altitude bar) there is a "R" designator called "Alt Reference Monitor": WHat Alt target does that designator display, is that the optimal Alt. at the appropriate phase of the approach (TAEM) or the glide slope signal of the MLS?
  
  3. At the center there is the famous diamond, displaying the guidance signal: Is that the direction the GPC (DAP?) is directing the shuttle at the current moment of the flight?
  
  4. Which guidance modes beside of HDG are available?
  
  
  On PDF-page  330 (2.7.27):
  
  5. Concerning the Declutter (what does that stand for?) Level 1 display of the HUD:
  
  A bit difficult to describe but there is the shuttle symbol (with the diamond tail at the top) and on each side the both triangels. I learned that the both triangels display the horizon, is that correct? If so, what does the diamond at the tail stand for or how is the display interpreted correctly?
  
  6. What does the cross "+" at Declutter levels 2 & 3 stand exactly for?
  
  7. In which Declutter mode and at what altitude do the pre flare triangels which command the  preflare pullout appear?
  
  8. I assume that the different (Declutter) modes of the HUD - at least while final approach - will change automatically dependent of the current altitude, is that correct?
  
  Thanks in advance!
  
  Greetings
  
  Can
   
  

  
  Mark Kirkman, we await your correct  answers.  Here is my stab at some
  
  1.  Yes
  3.  yes,
• #279 by mkirk on 12 Dec, 2007 15:06
• cantuezel - 10/12/2007 4:50 PM
  
  At the moment I try to deal with the different HUD displays which can be seen while landing the shuttle in the multiple landing videos here at L2. Therefore I read the appropriate parts of the SCOM (2.7. 24 - 2.7.27). Some issues and designators I still dont understand:
  
  On PDF-page 330 (2.7.26):
  
  1. There is a cross called "Boresight". What does that stand for? Is that the direction the vessel is pointing at the moment?
  
  The boresight/crosshair symbol represents the orbiter's X axis (nose to tail) and is in a fixed position 5 degrees above the center of the HUD’s field of view.
  
  2. On the very right side (at the Altitude bar) there is a "R" designator called "Alt Reference Monitor": WHat Alt target does that designator display, is that the optimal Alt. at the appropriate phase of the approach (TAEM) or the glide slope signal of the MLS?
  
  The R located on the altitude scale indicates that the Radar Altimeter is being used as the data source. This occurrs around 5000 feet.
  
  3. At the center there is the famous diamond, displaying the guidance signal: Is that the direction the GPC (DAP?) is directing the shuttle at the current moment of the flight?
  
  Yes, this is referred to as the guidance symbol and represents where the GPCs (general purpose computers)/Guidance thinks the vehicle should be flown.
  
  4. Which guidance modes beside of HDG are available?
  
  The Guidance Modes available here are:
  S-TURN
  ACQ – Acquistion
  HDG – Heading
  PRFNL – Pre Final
  CAPT – Capture
  OGS – Outer Glide Slope
  FLARE – Flare
  FNLFLARE – Final Flare
  
  A brief summary of guidance modes can be found in the last few pages of the section 2/GNC Guidance, Navigation, and Control chapter of the SCOM and also in Section 7 Trajectory Management.
  
  For those without access to L2, section 2 of the SCOM is available publicly at this:
  
  http://www.shuttlepresskit.com/STS-105/scom.htm
  
  On PDF-page 330 (2.7.27):
  
  5. Concerning the Declutter (what does that stand for?) Level 1 display of the HUD:
  
  A bit difficult to describe but there is the shuttle symbol (with the diamond tail at the top) and on each side the both triangels. I learned that the both triangels display the horizon, is that correct? If so, what does the diamond at the tail stand for or how is the display interpreted correctly?
  
  Declutter is an option that the Commander or Pilot can select by toggling the declutter switch located at the bottom left of the HUD. The first click of the switch will remove the runway overlay symbol, the second will remove the airspeed and altitude scales and the glideslope. The third click will remove everything except the boresight and a fourth click will return the HUD to the full display mode.
  
  6. What does the cross "+" at Declutter levels 2 & 3 stand exactly for?
  
  Covered in the response to question 1.
  
  7. In which Declutter mode and at what altitude do the pre flare triangels which command the preflare pullout appear?
  
  These triangles are the glideslope reference. You will see one fixed set and another set that tracks up the HUD as the orbiter approaches the pre flare altitude of 2000 feet.  At 2000 feet the symbols will merge and command the "pull up".
  
  8. I assume that the different (Declutter) modes of the HUD - at least while final approach - will change automatically dependent of the current altitude, is that correct?
  
  No, as described in question 5 declutter is a crew preference and not an automatic function.
  
  Mark Kirkman