Shuttle Questions Q & A (Part 4)

• #280 by cantuezel on 12 Dec, 2007 18:46
• Thanks very much for your detailed answers, Mark & Jim!
  
  Greetings
  
• #281 by madmardy on 12 Dec, 2007 19:12
• How are the seats on the flight deck and middeck stowed?
  do they fold up and into the floor? physically removed from the floor?
  and where do they go?
  
  they seem quite big and bulky
• #282 by Jim on 12 Dec, 2007 19:33
• Quote

  madmardy - 12/12/2007  3:12 PM
  
  How are the seats on the flight deck and middeck stowed?
  do they fold up and into the floor? physically removed from the floor?
  and where do they go?
  
  they seem quite big and bulky

  
  They can be removed from the floor and folded very compactly.   They stowed in corners, in the airlock, basically, anywhere out of the way.  
  
  They are similar to airline seats with thinner cushions.  
  
  The commander and pilot's seats are fixed.
• #283 by Susan27 on 15 Dec, 2007 12:48
• When watching approach and landing videos of the space shuttle I recognized that the CMD steering the vehicle cant be hard on the wheel-brakes. The shuttle is rolling out slowly very long and gently.
  
  1) Is there a special reason why the CMR does not bring the shuttle to a complete stop a bit faster? Is the deal of wear and tear of the wheel brakes (main gear) so extreme? I thought that the brakes are re-newed after the flight anywhere(?)
  
  2) Is there a general altitude where the CMR begins to preflare and is this Alt around 1800 ft or so?
  
  3) After the shuttle has come to a complete stop you often can hear a strange sound from the orbiter (hard to describe). Because there are no engines/jets running at all it has to be something different. Where could this sound come from (APUs, generators?)
  
  Many thanks in advance!
  
  Kind regards
  
  
• #284 by Ford Mustang on 15 Dec, 2007 12:57
• Quote

  Susan27 - 15/12/2007  8:48 AM
  
  When watching approach and landing videos of the space shuttle I recognized that the CMD steering the vehicle cant be hard on the wheel-brakes. The shuttle is rolling out slowly very long and gently.
  
  1) Is there a special reason why the CMR does not bring the shuttle to a complete stop a bit faster? Is the deal of wear and tear of the wheel brakes (main gear) so extreme? I thought that the brakes are re-newed after the flight anywhere(?)
  
  2) Is there a general altitude where the CMR begins to preflare and is this Alt around 1800 ft or so?
  
  3) After the shuttle has come to a complete stop you often can hear a strange sound from the orbiter (hard to describe). Because there are no engines/jets running at all it has to be something different. Where could this sound come from (APUs, generators?)
  
  Many thanks in advance!
  
  Kind regards
  
  

  
  3: That would be the APU's.  I think it sounds neat.  
  
  
  [small]This is the only answer that I know, and do not want to give out false information, so if anyone else has answers...[/small]
• #285 by kimmern123 on 15 Dec, 2007 22:54
• Quote

  Susan27 - 15/12/2007  2:48 PM
  
  When watching approach and landing videos of the space shuttle I recognized that the CMD steering the vehicle cant be hard on the wheel-brakes. The shuttle is rolling out slowly very long and gently.
  
  1) Is there a special reason why the CMR does not bring the shuttle to a complete stop a bit faster? Is the deal of wear and tear of the wheel brakes (main gear) so extreme? I thought that the brakes are re-newed after the flight anywhere(?)
  
  2) Is there a general altitude where the CMR begins to preflare and is this Alt around 1800 ft or so?
  
  3) After the shuttle has come to a complete stop you often can hear a strange sound from the orbiter (hard to describe). Because there are no engines/jets running at all it has to be something different. Where could this sound come from (APUs, generators?)
  
  Many thanks in advance!
  
  Kind regards
  
  

  
  2) What I've heard is that 1750 feet is the exact altitude that the guidance systems says the commander (CDR) should start pitching up. But I've also heard people say 2000 feet and 1500 feet so I actually have a follow-up question. Is the pre-flare altitude (if it differs from flight to flight) somehow connected to if the close or nominal aim point is used during A/L??
  
  I'd also like to add that I'm no expert but is merely basing this on what I've heard from others and read about.
• #286 by mkirk on 16 Dec, 2007 15:47
• Quote

  Susan27 - 15/12/2007  7:48 AM
  
  When watching approach and landing videos of the space shuttle I recognized that the CMD steering the vehicle cant be hard on the wheel-brakes. The shuttle is rolling out slowly very long and gently.
  
  1) Is there a special reason why the CMR does not bring the shuttle to a complete stop a bit faster? Is the deal of wear and tear of the wheel brakes (main gear) so extreme? I thought that the brakes are re-newed after the flight anywhere(?)
  
  2) Is there a general altitude where the CMR begins to preflare and is this Alt around 1800 ft or so?
  
  3) After the shuttle has come to a complete stop you often can hear a strange sound from the orbiter (hard to describe). Because there are no engines/jets running at all it has to be something different. Where could this sound come from (APUs, generators?)
  
  Many thanks in advance!
  
  Kind regards
  
  

  
  
  1)   Braking techniques and procedures are intended to minimize thermal stresses and prevent locked brakes – both of which can lead to blown tires.  Standard breaking begins when velocity has decreased below 140 knots and is a function of runway remaining.  If the orbiter is above 140 knots with less than 5000 feet remaining then the maximum breaking procedure is called for.
  
  On the HUD tapes you will usually here the PLT (seated in the right seat) calling out runway remaining and airspeed for the CDR.  Example:  “Seven board at 120” meaning there is 7000 feet of runway remaining and the orbiter is currently traveling at 120 knots.  "Board" refers to the runway markers located along the side of the runway in 1000 foot increments.
  
  The orbiter's currently uses modified (carbon) brakes which do behave better than the Beryllium breaks used earlier in the program which were always troublesome.
  
  I am not sure what the KSC processing folks do concerning the brakes during each flow.  I believe they are refurbished.  I have no idea how many flights a set of brakes are good for.
  
  2)   The Pre-Flare Guidance phase begins at 2000 feet; this is when guidance begins to issue the pitch commands that will take the orbiter from the steep glide slope to the shallow glide slope.
  
  If you are watching the HUD Tapes you will see the Pre-Flare Markers track up from the bottom of the HUD display and merge with the Outer Glide Slope Reference – this ideally occurs at about 2000-1700 feet at which time the CDR (commander) will begin to pull back on the control stick to position the orbiter on the shallow Inner Glide Slope.  Guidance pitch commands are attempting to track a constant 1.3 G pull-up.
  
  3)   I believe you are referring to the APUs.
  
  Mark Kirkman
  
• #287 by Lee Jay on 16 Dec, 2007 16:08
• Quote

  mkirk - 16/12/2007  9:47 AM
  

  Quote

  Susan27 - 15/12/2007  7:48 AM
  
  When watching approach and landing videos of the space shuttle I recognized that the CMD steering the vehicle cant be hard on the wheel-brakes. The shuttle is rolling out slowly very long and gently.
  
  1) Is there a special reason why the CMR does not bring the shuttle to a complete stop a bit faster? Is the deal of wear and tear of the wheel brakes (main gear) so extreme? I thought that the brakes are re-newed after the flight anywhere(?)
  

  
  
  1)   Braking techniques and procedures are intended to minimize thermal stresses and prevent locked brakes – both of which can lead to blown tires.  Standard breaking begins when velocity has decreased below 140 knots and is a function of runway remaining.  If the orbiter is above 140 knots with less than 5000 feet remaining then the maximum breaking procedure is called for.

  
  Also, don't forget that the Shuttle lands on the order of 80 knots faster than a typical airliner, so if you're comparing to watching those decelerate keep in mind that the Shuttle has a lot farther to go from touchdown ground-speed to wheel-stop.
  
  Lee Jay
• #288 by pr1268 on 18 Dec, 2007 05:28
• It's been discussed here time and again about the purpose of the throttle bucket - my question is, how come max Q actually occurs after the throttle up?
  
  For reference, I'm using William Harwood's STS-120 launch ascent data
  
  Thanks!
  
  Totally off-topic:  My 25th post at NSF - does this mean I get a star?  
  
• #289 by cantuezel on 18 Dec, 2007 13:55
• Hi,
  
  I watched the excellent (thanks!) dob to land video of STS-115. You can clearly listen to the transmissions/intercom:
  
  1.  At 01:08 :59 h of the vid (around 73k ft) CAPCOM commands the crew to...
  
  "leave air-data to NAV inhibited"...
  
  What does that mean?
  
  2. At 01:09:56 h  of the video (shortly before entering the HAC) you can see a "CSS" designator appear at the HUD and the crew says "CSS access": What does that stand for or mean?
  
  3. Shorty after entering the HAC (01:10:15 h) the pilot says...
  
  "...and I show you on and on..."
  
  What does that stand for?
  
  4. When VASI comes in sight the pilot confirms "Two and two" to be at the correct GS. What are the possible signals of this KSC "special" VASI in front of the RWY, I only know "all red -> too low" or "all white -> too high"...but are there more possible VASI-lights signals?
  
  5.  At 3000 ft the commander says "Speedbrakes!" and you can see the speedbrakes decreasing (designator going to the left). Does that mean that from this point on the speedbrakes arent in Auto-speedbrake mode any longer and are used manually until touching-down or what does that command mean exactly?
  
  6. At the same moment you can see designator "Flare" on the HUD-mode. What is this good for, I thought that the commander flies the whole final approach manually...?
  
  7.  At 01:14:11 h of the vid, after derotating, the pilot says something I dont understand...it sounds like...
  
  "brake eyes...valves above...are...open!" or so
  
  Could you translate this and describe what that means?
  
  8. While rolling out the pilot says...
  
  "stand by for any skid at 40".
  
  Is there a danger that the shuttle will skid at the special speed of 40 knots or why is this info given?
  
  Thanks very much for your help...
  
  Greetings
  
  
  
  
  
• #290 by Jorge on 18 Dec, 2007 14:42
• Quote

  cantuezel - 18/12/2007  8:55 AM
  
  Hi,
  
  I watched the excellent (thanks!) dob to land video of STS-115. You can clearly listen to the transmissions/intercom:
  
  1.  At 01:08 :59 h of the vid (around 73k ft) CAPCOM commands the crew to...
  
  "leave air-data to NAV inhibited"...
  
  What does that mean?

  
  The air data probes are deployed at M 5 and the crew starts evaluating the data at M 3.5. Air data can be incorporated separately to nav (baro altitude) and to G&C (alpha and M). In this case, the crew took data to G&C but left data inhibited to nav per MCC's instructions.
  
  

  Quote

  2. At 01:09:56 h  of the video (shortly before entering the HAC) you can see a "CSS" designator appear at the HUD and the crew says "CSS access": What does that stand for or mean?

  
  CSS=Control Stick Steering. It means the crew is flying manually.
  
  

  Quote

  3. Shorty after entering the HAC (01:10:15 h) the pilot says...
  
  "...and I show you on and on..."
  
  What does that stand for?

  
  "On glideslope" and "On energy".
  
  

  Quote

  4. When VASI comes in sight the pilot confirms "Two and two" to be at the correct GS. What are the possible signals of this KSC "special" VASI in front of the RWY, I only know "all red -> too low" or "all white -> too high"...but are there more possible VASI-lights signals?

  
  Not as far as I know. Last I heard, they were standard.
  
  

  Quote

  6. At the same moment you can see designator "Flare" on the HUD-mode. What is this good for, I thought that the commander flies the whole final approach manually...?

  
  It indicates what mode guidance is in, which is a good cue for the CDR even if he's flying manually because the flight director on the HUD is based on the current guidance mode.
  
• #291 by pr1268 on 18 Dec, 2007 14:43

• Lemme try to answer some of these...
  
  

  Quote

  cantuezel - 18/12/2007  8:55 AM
  2. At 01:09:56 h  of the video (shortly before entering the HAC) you can see a "CSS" designator appear at the HUD and the crew says "CSS access": What does that stand for or mean?
  

  
  CSS is the control stick steering mode, the "joystick" flight control.  I think this indicates that the shuttle's GPCs will permit manual flight via CSS controls at that point.  Bear in mind the shuttle is still a fly-by-wire flight control system.

  Quote

  6. At the same moment you can see designator "Flare" on the HUD-mode. What is this good for, I thought that the commander flies the whole final approach manually...?

  Many of the messages on the annunciators act as reminders or indicators for the crew.  It's possible that the CDR or PLT might not have a clear perception of the shuttle's altitude, distance from threshold, and/or attitude, so the console messages are part of the redundancy built in. (Maybe there's a more specific reason - I'm kind of going on intuition here.)
  

  Quote

  8. While rolling out the pilot says...
  
  "stand by for any skid at 40".
  
  Is there a danger that the shuttle will skid at the special speed of 40 knots or why is this info given?

  
  That's anti-skid - refers to the brakes not locking up in case the CDR or PLT wants to "slam on" the brakes (not that they'd need to).

  Of course, there are many others much more qualified than I to answer these questions.  I hereby request to be corrected in case I'm wrong...
   

• #292 by pr1268 on 18 Dec, 2007 14:57
• How noisy is it inside the Shuttle crew compartment at lift off?  Specifically, can the SSME ignition be heard?  How loud/discernible are the SRBs?
  
  BTW I've watched many of the L2 on-board videos, but those seem to have the capsule intercom patched into the audio (and not ambient noise), the exception being the STS-117 orbital maneuver video.
• #293 by bigdukey on 18 Dec, 2007 15:29
• Quesion - "It's been discussed here time and again about the purpose of the throttle bucket - my question is, how come max Q actually occurs after the throttle up?"
  
  I may be corrected on this! In simple terms Max Q is the maximum pressure caused from passing through the atmosphere. If you think of this as maximum air friction this will be proportional to the speed (squared) of the vehicle at the time and not the acceleration caused by the SRBs. Of course the throttle up will increase the speed and so max Q will come after throttle up, but as you know the velocity will keep on rising, therefore increasing the pressure even after throttle up.
  
  After Max Q the shuttle starts to clear the thickest bit of the astmosphere so that even the vehicle continues to go faster, there is less astmosphere to 'push' through hence less pressure.
  
  (You can think through bernoullis equation etc but you come to the same v squared concept.)
• #294 by kimmern123 on 18 Dec, 2007 15:35
• Quote

  cantuezel - 18/12/2007  3:55 PM
  
  
  4. When VASI comes in sight the pilot confirms "Two and two" to be at the correct GS. What are the possible signals of this KSC "special" VASI in front of the RWY, I only know "all red -> too low" or "all white -> too high"...but are there more possible VASI-lights signals?
  
  
  
  

  
  There are PAPIs at the SLF, which differs a little from a VASI-system. PAPI or Precision Aproach Path Indicator is a set of four lights that at the SLF is positioned ahead of the runway. There are two PAPIs at the SLF, one serves as the nominal aimpoint and one as the close aimpoint.
  
  Other than that it functions just like another PAPI-system. Two red and two white lights is on glideslope, three red and one white means slightly low, four red means significantly low. Likewise three white and one red means slightly high and four white means significantly high.
• #295 by Susan27 on 18 Dec, 2007 15:42
• Hi,
  
  regarding this cool interieur view of the flight deck:
  
  http://www.panoscan.com/Shuttle/FlightDeck/Full.mov
  
  
  1) Where can I find the switch to deploy the landing gear and the speedbrakes?
  
  2) To the CSS-steering: It looks like a common joystick (lol!), is it used way that pilot has to put CSS in the "middle", meaning left foot left of CSS and right one on its right side...or is it more like in the AIRBUS FBW family (CSS situated at the side-window, so the feet stay "free")?
  
  Thanks in advance!
  
  Kind regards
• #296 by pr1268 on 18 Dec, 2007 15:46
• Thank you, sir!
  
  Related question:  Someone asked on the Part 2 (or Part 3) Q & A how much faster the Shuttle would be going if it did not perform the max Q throttle bucket.  The short reply was that the Shuttle would reach orbit "...without wings."
  
  All obvious silliness aside, just how much Q is saved by throttling back?  I don't see that much difference in total thrust by lowering the three SSMEs to 67%.... Thanks in advance.
  
• #297 by Jim on 18 Dec, 2007 15:48
• Quote

  Susan27 - 18/12/2007  11:42 AM
  
  Hi,
  
  regarding this cool interieur view of the flight deck:
  
  http://www.panoscan.com/Shuttle/FlightDeck/Full.mov
  
  
  1) Where can I find the switch to deploy the landing gear and the speedbrakes?
  
  2) To the CSS-steering: It looks like a common joystick (lol!), is it used way that pilot has to put CSS in the "middle", meaning left foot left of CSS and right one on its right side...or is it more like in the AIRBUS FBW family (CSS situated at the side-window, so the feet stay "free")?
  
  Thanks in advance!
  
  Kind regards

  
  1.  The spacebrake control is the same as the SSME throttle control, which is to the left of each pilot.  The gear switch is on the forward panel, F6 and F8
  
  2.  The crew straddle the stick
• #298 by bigdukey on 18 Dec, 2007 16:20
• Quote

  pr1268 - 18/12/2007  10:46 AM
  
  Thank you, sir!
  
  Related question:  Someone asked on the Part 2 (or Part 3) Q & A how much faster the Shuttle would be going if it did not perform the max Q throttle bucket.  The short reply was that the Shuttle would reach orbit "...without wings."
  
  All obvious silliness aside, just how much Q is saved by throttling back?  I don't see that much difference in total thrust by lowering the three SSMEs to 67%.... Thanks in advance.
  

  
  Whilst the reduction of thrust for a few seconds only means a few percent loss in overall speed, remember that the pressure is related to the square of the velocity and that at the point of throttling, the atmosphere is far thicker. Therefore a small loss of velocity at this point makes a much bigger difference than throttling at any other point.
  Like anything, I guess its one of the many trade offs in the design process, strength(mass) of wings verses loosing a few miles and hour.
  
  If you look at the wonderfull Bill Harwoods data, during throttle back you only loose approx 80mph, but by the time you've gained a little bit back with a bit of fuel saving, and also using the saved fuel more efficiantly at a time where the atmospheric friction is less, it probabally doesnt make that much difference!
• #299 by SiameseCat on 18 Dec, 2007 16:42
• Some questions about launch guidance:
  1) First stage guidance uses relative velocity to determine the desired attitude. Is this inertial velocity or velocity relative to the ground?
  2) MECO occurs when a certain velocity is reached. Is this horizontal velocity or the shuttle's overall speed?