Shuttle Questions Q & A (Part 4)

• #300 by Jorge on 18 Dec, 2007 17:07
• Quote

  SiameseCat - 18/12/2007  11:42 AM
  
  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?

  
  1) Magnitude of relative aero velocity (Earth-surface relative velocity minus I-loaded wind table components)
  2) Magnitude of inertial velocity
• #301 by mkirk on 18 Dec, 2007 18:21
• I am having a difficult time determining which questions got answered (correctly) and which ones have not but here is what I think got missed.
  
  
  

  Quote

  cantuezel - 18/12/2007  8:55 AM
  
  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?

  
  I attached a diagram at the bottom of this post showing the PAPI indications for the various glide slopes.  The specific glide slope chosen is a function of orbiter weight.
  
  

  Quote

  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?

  
  The call out is advisory in nature and serves as a crosscheck that the Speedbrake setting is changing as expected.  The call is usually made by the MS2 (mission specialist 2 designated as the flight engineer) in the middle seat and the indications are checked by the CDR and PLT.  The automatic changes initiated by guidance while the orbiter is on Final occur at 3000 feet, 500 feet, and at touchdown.  If the speedbrakes do not operate in auto as expected then the CDR will manually adjust them using the lever located by his left knee.
  
  

  Quote

  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?

  
  The callout is: "BRAKE ISOL VALVES OPEN".  The Brake Isol (Isolation) Valves are commanded open by the GPCs (general purpose computers) at touchdown (from the weight on wheels logic).  The PLT looks behind his right shoulder - using a small mirror located on the front eyebrow panel since it is hard to turn your head in the Helmet/Launch and Entry Suit - to verify that the valves did indeed open on Panel R4.  The opening of the valves ensures proper hydraulic pressure for application of the brakes.
  
  

  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?

  
  
  He is referring to the ANTI SKID CUTOUT.  Operation of the anti skid system degrades and becomes ineffective as speed decreases.  This is common for most aircraft.  The two airplanes I am most familiar with are the F-15 and C-5 and it was normal for the systems to be turned off at 30 knots (F-15) and 20 knots (C-5).  As is the case with both of those aircraft the Shuttle's Anti Skid system ceases to operate at about 15 - 14 knots.  This callout is intended to prepare the crew for this eventuallity.
  
  Mark Kirkman

  ---

  
• #302 by pr1268 on 18 Dec, 2007 18:31
• Quote

  mkirk - 18/12/2007  1:21 PM
  He is referring to the ANTI SKID CUTOUT.  Operation of the anti skid system degrades and becomes ineffective as speed decreases.  This is common for most aircraft.  The two airplanes I am most familiar with are the F-15 and C-5 and it was normal for the systems to be turned off at 30 knots (F-15) and 20 knots (C-5).  In the Shuttle Anti Skid ceases to operate at about 14 knots.  This callout is intended to prepare the crew for this.
  
  Mark Kirkman

  
  Thank you, sir.  Is "anti-skid" the same as "anti-lock"? (I'm thinking about passenger cars and light trucks built these days...)  Just curious, does the same generalization of anti-skid being less effective at lower speeds for aircraft also hold true for cars/trucks?  Thanks again.
• #303 by mkirk on 18 Dec, 2007 18:37
• Quote

  Jim - 18/12/2007  10:48 AM
  
  

  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
  

  
  Since it is the PLT who usually presses the gear buttons I attached a diagram of the Pilots' forward panel with the gear buttons, the two buttons are at the bottom left - similar buttons are located in front of the Commander.  It take both the ARM button and the DN (Down) button to deploy the gear.  At 2000 feet the Commander will call out "ARM the Gear" and the PLT will press the ARM button, at 300 feet (+/- 100) the Commander will call out "Gear" and the PLT will press the DN button to deploy the gear.
  
  Mark Kirkman

  ---

  
• #304 by mkirk on 18 Dec, 2007 18:56
• Quote

  pr1268 - 18/12/2007  1:31 PM
  
  

  Quote

  mkirk - 18/12/2007  1:21 PM
  He is referring to the ANTI SKID CUTOUT.  Operation of the anti skid system degrades and becomes ineffective as speed decreases.  This is common for most aircraft.  The two airplanes I am most familiar with are the F-15 and C-5 and it was normal for the systems to be turned off at 30 knots (F-15) and 20 knots (C-5).  In the Shuttle Anti Skid ceases to operate at about 14 knots.  This callout is intended to prepare the crew for this.
  
  Mark Kirkman

  
  Thank you, sir.  Is "anti-skid" the same as "anti-lock"? (I'm thinking about passenger cars and light trucks built these days...)  Just curious, does the same generalization of anti-skid being less effective at lower speeds for aircraft also hold true for cars/trucks?  Thanks again.

  
  Yes, “anti-skid” and “anti-lock” are analogous.
  
  I would assume on a smaller scale the low speed issues apply to cars as well, however, I am pretty ignorant when it comes to cars.  
  
  Since my car doesn’t have wings or SRBs I don’t know anything about it other than how to put the key in the little ignition thingy located near the steering wheel doodad and how to drive excessively fast when my radar/threat warning system is clean (that is pilot talk for - no police along the highway with radar detectors).
  
  Mark Kirkman
  
• #305 by Susan27 on 18 Dec, 2007 21:34
• Thanks very much for *all* your good answers!
  
  1) Concerning the switch/lever for the speedbrakes: Jim said that the speedbrake control is the same as the SSME throttle control. I looked at the drawing I metioned above but was unable to locate the correct position of this SSME throttle/speedbrake lever.
  
  Could someone give a hint where to look closer (panel or so)? And why the constructor didnt use a separate switch for the speedbrakesb (like on common airplanes) but to use the same lever which is used for manual-power of the Main-engines (SSME) during launch?
  
  And. Is there a logic that says the instrument that it shall act as a speedbrake lever after MECO, I really have problems following that issue of the speedbrake-lever...?
   
  
  2) To the Anti-skid thing during roll-out: Why is anti-skid function getting worse when loosing speed, is there a special reason for that?
  
  
  And most improtant: OK, lets say that Anti-skid gets worse at lower speeds, but its better to have it "on" until the shuttle comes to a complete stop instead of switching the system "off" at 20 knots or so. Where is my "fault"?
  
  3) Another topic I always wanted to know is that (please dont laugh!):
  
  a) Concerning the safety belts: What kind of "safety belts"/ or other hold-back-systems are used on the shuttle that the crew stays exactly at the fixed position? Specially during launch (up to 3 G, head-down, head-up pos. change etc.) there are extreme forces working on the orbiter...
  
  Do the flight-crew use 4 or even 5-point belts like the ones used in F1/Indy car serie or what does NASA use for that purpose...?
  
  b) Concerning the head-set communication system of the flight crew:
  
  When watching multiple cockpit vids you can see on the one side that the crew-member speaking to CAPCOM takes the micro, presses a know and speaks...
  
  But how does the system work during launch and deorbit/final approach when the crew wears those heavy helmets with closed visors etc.? They certainly dont have time to grap for mics, pressing knobs etc. At first I thought that they use voice-detecting head-set systems, so that the mic goes into mode "transmission" as soon as it detects voice.
  
  But this cant be: Most of the different flight-phases it is "only" crew-chatter (intercom) and not meant for transmission to CAPCOM. So voice-detected ones would transmit simply every word spoken in the cockpit...(!)
  
  So, do you know how NASA solved that problem?
  
  c) Finally to the sun-glare-protection the crew-helmets contain while launch/ascend: I learned that the flight crew wears this helmet with that special UV-sun glass-system, so that extreme sun-light wont glare the CMD or pilot during ascend. Additionally the crew wears those dark(?) visors for part of the trip.
  
  How is the flight crew still capable to see all instruments with those extreme "sun-protection" things wearing...?
  
  
  Many thanks in advance!
  
  Kind regards
• #306 by pr1268 on 18 Dec, 2007 22:58
• Quote

  Susan27 - 18/12/2007  4:34 PM
  a) Concerning the safety belts: What kind of "safety belts"/ or other hold-back-systems are used on the shuttle that the crew stays exactly at the fixed position? Specially during launch (up to 3 G, head-down, head-up pos. change etc.) there are extreme forces working on the orbiter...
  
  Do the flight-crew use 4 or even 5-point belts like the ones used in F1/Indy car serie or what does NASA use for that purpose...?
  

  
  Each crew member is restrained by a 5-point seat belt system.
  
  Strange how I just learned that myself; not 90 minutes ago I was reading about a 5-point safety buckle recovered from the STS-107 debris (CAIB, Appendix G.12, p. 365).
• #307 by mkirk on 18 Dec, 2007 23:53
• Quote

  Susan27
  
  1) Concerning the switch/lever for the speedbrakes: Jim said that the speedbrake control is the same as the SSME throttle control. I looked at the drawing I metioned above but was unable to locate the correct position of this SSME throttle/speedbrake lever.
  
  Could someone give a hint where to look closer (panel or so)? And why the constructor didnt use a separate switch for the speedbrakesb (like on common airplanes) but to use the same lever which is used for manual-power of the Main-engines (SSME) during launch?
  
  And. Is there a logic that says the instrument that it shall act as a speedbrake lever after MECO, I really have problems following that issue of the speedbrake-lever...?
   

  
  Okay, look at this picture from the NASA Public Gallery.  
  
  http://spaceflight.nasa.gov/gallery/images/shuttle/sts-101/html/jsc2000e10522.html
  
  On the left side console you will see a black lever with a red button on it.  This is the Commander's Speedbrake Lever - the Commander can not throttle the engines, his/her lever only operates the speedbrake.  On the right side of the center console you will see a similar lever, this is the Pilot's Speedbrake/Throttle Lever - it operates the same as the Commander's for Speedbrake functions, and during Ascent it can throttle the main engines.
  
  

  Quote

  2) To the Anti-skid thing during roll-out: Why is anti-skid function getting worse when loosing speed, is there a special reason for that?
  
  And most improtant: OK, lets say that Anti-skid gets worse at lower speeds, but its better to have it "on" until the shuttle comes to a complete stop instead of switching the system "off" at 20 knots or so. Where is my "fault"?

  
  The tendency is for the wheels to lock (i.e. stop spinning) which is far less effective when it comes to stopping the vehicle.  So after the cutout it is up to the CDR/PLT to apply proper breaking techniques.  At this point the orbiter is moving relatively slowly and it is not much of an issue.
  
  
  

  Quote

  b) Concerning the head-set communication system of the flight crew:
  
  When watching multiple cockpit vids you can see on the one side that the crew-member speaking to CAPCOM takes the micro, presses a know and speaks...
  
  But how does the system work during launch and deorbit/final approach when the crew wears those heavy helmets with closed visors etc.? They certainly dont have time to grap for mics, pressing knobs etc. At first I thought that they use voice-detecting head-set systems, so that the mic goes into mode "transmission" as soon as it detects voice.
  
  But this cant be: Most of the different flight-phases it is "only" crew-chatter (intercom) and not meant for transmission to CAPCOM. So voice-detected ones would transmit simply every word spoken in the cockpit...(!)
  
  So, do you know how NASA solved that problem?

  
  This is a good INCO question so if Charlie is out there he should be able to expand on this.
  
  There are multiple settings and headset units.  Keeping it simple, the crew can select VOX - which is voice activated communication or PTT - which is push to talk.  With VOX you will here whoever is talking in the cockpit if their voice breaks a preset volume level (vox level).  With push to talk the crew member has to push a button on the comm unit itself or the transimit button on the control stick.  Generally the control stick button is primary for Air to Ground during Ascent and Entry.
  
  
  

  Quote

  c) Finally to the sun-glare-protection the crew-helmets contain while launch/ascend: I learned that the flight crew wears this helmet with that special UV-sun glass-system, so that extreme sun-light wont glare the CMD or pilot during ascend. Additionally the crew wears those dark(?) visors for part of the trip.
  
  How is the flight crew still capable to see all instruments with those extreme "sun-protection" things wearing..

  
  I'm not sure what I can say to this question other than it is not much different than looking through sunglasses.  The dark visor is a crew preference thing and more often than not they will rotate the dark visor up and just use the clear one.  As for reading the instruments the crew can adjust the brightness of the dsiplays and panel back lighting as required.
  
  Mark Kirkman
• #308 by Jim on 19 Dec, 2007 00:01
• Quote

  Susan27 - 18/12/2007  5:34 PM
  
  1) Concerning the switch/lever for the speedbrakes: Jim said that the speedbrake control is the same as the SSME throttle control. I looked at the drawing I metioned above but was unable to locate the correct position of this SSME throttle/speedbrake lever.
  
  Could someone give a hint where to look closer (panel or so)? And why the constructor didnt use a separate switch for the speedbrakesb (like on common airplanes) but to use the same lever which is used for manual-power of the Main-engines (SSME) during launch?
  
  And. Is there a logic that says the instrument that it shall act as a speedbrake lever after MECO, I really have problems following that issue of the speedbrake-lever...?
   
  
  2) To the Anti-skid thing during roll-out: Why is anti-skid function getting worse when loosing speed, is there a special reason for that?
  
  
  And most improtant: OK, lets say that Anti-skid gets worse at lower speeds, but its better to have it "on" until the shuttle comes to a complete stop instead of switching the system "off" at 20 knots or so. Where is my "fault"?
  
  3) Another topic I always wanted to know is that (please dont laugh!):
  
  a) Concerning the safety belts: What kind of "safety belts"/ or other hold-back-systems are used on the shuttle that the crew stays exactly at the fixed position? Specially during launch (up to 3 G, head-down, head-up pos. change etc.) there are extreme forces working on the orbiter...
  
  Do the flight-crew use 4 or even 5-point belts like the ones used in F1/Indy car serie or what does NASA use for that purpose...?
  
  b) Concerning the head-set communication system of the flight crew:
  
  When watching multiple cockpit vids you can see on the one side that the crew-member speaking to CAPCOM takes the micro, presses a know and speaks...
  
  But how does the system work during launch and deorbit/final approach when the crew wears those heavy helmets with closed visors etc.? They certainly dont have time to grap for mics, pressing knobs etc. At first I thought that they use voice-detecting head-set systems, so that the mic goes into mode "transmission" as soon as it detects voice.
  
  But this cant be: Most of the different flight-phases it is "only" crew-chatter (intercom) and not meant for transmission to CAPCOM. So voice-detected ones would transmit simply every word spoken in the cockpit...(!)
  
  So, do you know how NASA solved that problem?
  
  c) Finally to the sun-glare-protection the crew-helmets contain while launch/ascend: I learned that the flight crew wears this helmet with that special UV-sun glass-system, so that extreme sun-light wont glare the CMD or pilot during ascend. Additionally the crew wears those dark(?) visors for part of the trip.
  
  How is the flight crew still capable to see all instruments with those extreme "sun-protection" things wearing...?
  
  

  
  1.  Panel L2 and C3.  The speedbrake is only used on entry and not ascent.  The speedbrake controls energy, which also a throttle does.  The speedbrake is variable from 0-100%.
  
  Ascent and entry use different software, so there never will be a confusion.
  
  3 B.  They wear "snoopy" hats (like Apollo) with integral headphones and mikes,  The control sticks have push to talk buttons
  
  3C.  Just like in a car, turn up the instrument lights
  
  
  
• #309 by SiameseCat on 19 Dec, 2007 01:30
• What is the pitch angle of the shuttle at SRB Sep?
• #310 by pr1268 on 19 Dec, 2007 01:48
• Quote

  SiameseCat - 18/12/2007  8:30 PM
  
  What is the pitch angle of the shuttle at SRB Sep?

  
  Going on William Harwood's launch data for STS-120, I calculated the pitch angle at SRB sep to be 152.6 degrees, i.e. 27.4 degrees from a purely inverted ("upside down") pitch attitude.
  
  I'd be happy to show my work should you desire, but my calculations may still be off somewhere.  The formula I used is somewhat hairy.
  
• #311 by Susan27 on 19 Dec, 2007 08:14
• Quote

  mkirk - 18/12/2007  6:53 PM
  
  On the left side console you will see a black lever with a red button on it.  This is the Commander's Speedbrake Lever - the Commander can not throttle the engines, his/her lever only operates the speedbrake.  On the right side of the center console you will see a similar lever, this is the Pilot's Speedbrake/Throttle Lever - it operates the same as the Commander's for Speedbrake functions, and during Ascent it can throttle the main engines.

  
  OK, I got it!
  
  a) While looking at the link you gave me and the (quicktime) drawing of the cockpit I am wondering where the OMS & RCS levers are:
  
  At the left-bottom of CMR1-display (F5-console?) there is a small black stick, is this the OMS-lever? If so, where can I find the RCS-control lever then...?
  
  b) Concerning the push-to-talk transmit button on the CSS: Do you mean the small black knob directly located at the very top of the CSS or the bigger one at the left of this knob?
  
  Thanks very much in advance!
  
  Kind regards
• #312 by DaveS on 19 Dec, 2007 08:24
• a)There's no lever for the OMS. It's on(1000% thrust) or off(0% thrust). The RCS is controlled by the joysticks on the Commander(correct acronym: CDR)'s side. They're called Translational Hand Controller(THC) and Rotational Hand Controller(RHC).
  
  (b)Yes. The red button engages the Back-up Flight System(BFS).
• #313 by mkirk on 19 Dec, 2007 13:27
• Quote

  Susan27 - 19/12/2007  3:14 AM
  
  b) Concerning the push-to-talk transmit button on the CSS: Do you mean the small black knob directly located at the very top of the CSS or the bigger one at the left of this knob?
  
  Thanks very much in advance!
  
  Kind regards

  
  No, please refer to the diagram I attached for specific switch functions.
  
  Something I have always found amusing is what continuously using the trigger as a communications switch might mean to someone who leaves the Astronaut Corps to go back to flying fighters for the military.  I’m not sure how powerful the muscle memory would be after several years in the shuttle world (discounting T-38 time), but it would sure suck if you were simply trying to make a routine call to air traffic control from a plane like the F-15 or F-18 and you end up shooting some 20 millimeter rounds up your wingman’s tail pipe because you used the trigger instead of the throttle mounted transmit button.
  
  Of course it takes some additional switch throws (i.e. master arm on, etc) for something like that to happen in a fighter jet, but I always felt a strange twinge in my hand when it came to making Air to Ground transmitions in the Shuttle Mission Simulator with the RHC trigger.
  
  Mark Kirkman
  

  ---

  
• #314 by mkirk on 19 Dec, 2007 13:44
• Quote

  SiameseCat - 18/12/2007  8:30 PM
  
  What is the pitch angle of the shuttle at SRB Sep?

  
  Generally the nose is pitched about 20+ degrees above the horizon.
  
  Mark Kirkman
• #315 by pr1268 on 20 Dec, 2007 00:17
• Regarding the CSS, it seems that the BFS engage switch is "dangerously" convenient.  My understanding is that engaging the BFS should only occur if the GPCs fail to provide proper guidance and navigation for whatever reason.
  
  Is the BFS switch there to give the CDR (or PLT) such capability if needed?  I'm reminded of the spin event during Gemini 8 (thruster stuck "on").  Thanks!
• #316 by Jorge on 20 Dec, 2007 00:21
• Quote

  pr1268 - 19/12/2007  7:17 PM
  
  Regarding the CSS, it seems that the BFS engage switch is "dangerously" convenient.  My understanding is that engaging the BFS should only occur if the GPCs fail to provide proper guidance and navigation for whatever reason.
  
  Is the BFS switch there to give the CDR (or PLT) such capability if needed?  I'm reminded of the spin event during Gemini 8 (thruster stuck "on").  Thanks!

  
  It is there so it can be engaged quickly. The button has a very strong spring and is difficult to depress by accident.
• #317 by joema on 20 Dec, 2007 20:25
• Quote

  pr1268 - 18/12/2007  10:46 AM...I don't see that much difference in total thrust by lowering the three SSMEs to 67%...

  SRB thrust also decreases according to a fixed schedule during the high Q phase, which constitutes a greater decrease than the SSME throttle bucket.
  
  Peak total thrust at about T+20 sec is roughly 393,400 lbf per SSME plus 3.15 million lbf per SRB, for a total of 7.48 million lbf.
  
  By contrast at about T+50 sec, SSME thrust has decreased to about 251,000 lbf per SSME, whereas SRB thrust has decreased to 2.25 million lbf per SRB, for a total of about 5.25 million lbf. Afterwards the SRB thrust increases to 2.55 million lbf per SRB.
  
  So the total thrust decrease during the high Q phase is 7.48 million - 5.25 million = 2.23 million lbf, IOW total thrust drops by about 30%.
  
  Of this decrease total SSME thrust decreases by 427,000 lbf, whereas total SRB thrust decreases by 1.8 million lbf. So roughly 19% of the total thrust decrease is from the SSME throttle bucket, roughly 81% is from the SRB thrust decrease.
• #318 by SiameseCat on 21 Dec, 2007 01:35
• During the initial roll, what is the roll rate of the shuttle?
• #319 by Susan27 on 21 Dec, 2007 09:57
• Hi,
  
  When watching (RWY 24?) final approaches at EDW AFB I recognized a strange black "object" (looking a bit like a triangle on the desert-ground) located directly between the PAPI lights (on the extended centerline) in front of the RWY. You can see the same object I think at White Sands...
  
  Do you know what this object exatcly is? I assume it must have something to do with the PAPI approach system or even with the MLS-antennas(?)...but I am very unsure...
  
  Do you know what that is...?
  
  Thanks in advance!
  
  Kind regards