Shuttle Questions Q and A (2)

• #580 by Jim on 19 Dec, 2006 17:36
• There use to be TAL  (trans Atlantic landing) and TPL  (trans Pacific landing) sites , which was changed to the generic TAL (trans oceanic abort landings).  Easter Island was a TPL site and  Hao was looked at.
• #581 by psloss on 19 Dec, 2006 17:37
• Quote

  elmarko - 19/12/2006  12:40 PM
  
  What were the potential abort options for a Polar launch? RTLS and AoA would have been ok, but what options would have existed further along the launch site for any kind of intact sub-orbital abort? I'm not familiar with the geography of the area. Is Easter Island viable or was that a bit of artistic license used by the author?

  It was viable; already been discussed in the forums at least once:
  http://www.nasaspaceflight.com/forum/forums/thread-view.asp?tid=1050
  
• #582 by Jim on 19 Dec, 2006 17:49
• The perigee is negative after the deorbit burn
• #583 by STS-500Cmdr on 19 Dec, 2006 21:04
• About White Sands, i remember during STS-99 the SRTM mission--as it was winding down there was talk of landing at White Sands-as well as talk about Edwards at a briefing i think Dittemore and Rob Navias said NASA doesnt have live TV coverage capability at White Sands anymore--that was as of STS-99 i assume thats still the case??  And the 1 time they landed there--STS-3 Columbia--when they brought the shuttle back it was full of gypsum.  Is that still a problem if we land at White Sands??  Hey wait a minute, they landed the shuttle at White Sands in "SpaceCamp"-:)
• #584 by psloss on 19 Dec, 2006 21:34
• Based on what Bill Harwood wrote today, White Sands would be programmatic problem:
  
  from "SR-93 (12/19/06): Early weather forecast 'iffy' for Friday"
  http://www.cbsnews.com/network/news/space/current.html
  
  Excerpt:
  

  Quote

  NASA wants to avoid a landing in New Mexico if at all possible because it would take an estimated 45 days to bring in cranes and other equipment needed for mounting the shuttle atop a transport jet for return to Florida.
• #585 by mkirk on 19 Dec, 2006 21:34
• Quote

  elmarko - 19/12/2006  11:40 AM
  
  Also, still looking for an answer to my deorbit burn perigee question, please?

  
  

  Quote

  Jim - 19/12/2006  12:32 PM
  
  The perigee is negative after the deorbit burn

  
  Not necessarily;
  
  The De-orbit Burn is designed to target a resulting orbit that intersects Entry Interface at a specific flight path angle.  The orbital path from apogee (where the burn starts) to perigee will pass thru Entry Interface.
  
  Using the preliminary Burn Target Data for the first attempt to KSC this Friday, the burn ignition will occur at an altitude of 186.6 nautical miles and will last for 3 minutes 17 seconds and provide a retrograde Delta V of 326 feet per second (i.e. slow the orbiter’s velocity by 326 fps).  This will result in an Entry Interface at 399,100 feet at a range to the runway of 4433 nautical miles…I don’t know what that equates to in HP (altitude for perigee) but it should be a small positive number.
  
  My recollections from the many de-orbit burns I practiced in the SMS (shuttle mission simulator) and SSTs (single systems trainer) was that HP usually ranged from 5 to 18 nautical miles.  When the burn starts you look at HP to make sure it is decreasing, but I must confess that I really don’t remember looking at that variable after a burn was completed unless I was practicing emergency procedures and then I would look at it to see how screwed I was – Bad Instrument Scanning Technique I Guess – but there were other things you are focused on such as residual velocities in all of the X, Y and Z axis that need to be nulled out and time/range to Entry Interface.
  
  Mark Kirkman
  
• #586 by elmarko on 19 Dec, 2006 22:19
• Awesome, thanks Jim/Mark. I'll experiment more with my perigees. The general consensus from the Orbitersim crowd is to burn further away than normal and leave the perigee somewhat higher, at about 20/30 miles or so. But this leaves you in the atmosphere longer, heating period is longer, etc etc. I imagine it's kind of like an AoA Shallow.
  
  I have no idea WHY they do it this way. Before that, the generally accepted method was to burn to 0km altitude for perigee. Which was technically more correct than people seem to do now
  
  I'll go play some more. Thanks.
• #587 by mkirk on 19 Dec, 2006 22:22
• Quote

  shuttlepilot5 - 18/12/2006  11:55 PM
  
  i just got 1 question about the landing. how do they do it?
  I mean, im used to how a commercial airliner lands by using the ILS system. Im sure you guys are familiar with the common civil aviation ILS system.
  
  but do the space shuttle use a similar system like the ILS? Or do they just track the runway visualy?
  I think the pilot of the shuttle must have some sort of "navigation/landing system". But i dont know much about the space shuttle....so it would be great if you guys could just explain the basics of the landing(ILS)
  
  

  
  The shuttle uses several different sources of data for Navigation Processing by the General Purpose Computers, normally referred to as NAV.
  
  NAV generates 3 separate state vectors.  A state vector is the calculation of the orbiter’s position and velocity at a specific time.  NAV continuously propagates the state vector using the equations of motion (thank you Mr. Newton).  A KALMAN filter is used to blend all of the various sensors into those calculations.  The sensors I am referring to are DRAG H (or drag altitude, which in simple terms is an aerodynamic model of the atmosphere's effect on the orbiter), TACAN (same as a VORTAC), Air Data Probes (similar to the PITOT STATIC system on conventional airplanes), MLS (which is the shuttle’s version of the ILS – it is a very precise system), GPS, and Radar Altimeters.
  
  I have attached a pdf chart of how when the various sensors are used at the very bottom of this post.  For instance the MLS is not really affective until around 18,000-15,000 feet which is when the orbiter is rolling out on final.
  
  The Radar Altimeters are not processed by NAV, they are only used for crew displays and become effective as the orbiter descends thru 5000 feet.
  
  So far GPS is not fully processed by the shuttle computers either.  Currently the shuttle program is flying a “ramp up” test of the system.  On the last mission, STS-115, the GPS was used for the first time in the primary (PASS) general purpose computers.  The plan was to let the PASS GPCs use the GPS in the processing scheme for a little while and then inhibit them from the NAV scheme and land using the standard navigation scheme (i.e. air data probe derived data).  However, GPS worked so well and accurately that Mission Control told the crew to keep it instead of the “Air Data”.  In other word the GPS prediction of the orbiter’s Stated Vector was more accurate than the standard Air Data prediction.  
  
  If you saw the post landing press conference then you heard a 10 minute dissertation on how this worked from an obviously pleased Leroy Cain.  Cain used to be a GNC (guidance, navigation, and control) Flight Controller in Mission Control…so he is very familiar with the system.
  
  Anyway the plan is to use the GPS again on this flight (116) as part of the ramp up program before flying a full GPS flight on STS-117.
  
  Mark Kirkman
  
  P.S.
  
  I wrote a little blurb on how the very last part of the final approach is flown in the shuttle on the first Shuttle Q&A thread here:
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=625&start=271
  
  

  ---

  Landing Sensors Chart.pdf
• #588 by EW-3 on 20 Dec, 2006 00:13
• was wondering about EVAs....
  When Beamer was performing his magic, to get around he had to feed instructions constantly to the arm drivers..
  Is there a capability to go to fixed points without all the dialog?  
  For example in yesterdays excercise, he frequently had to go back to the same safe position.  It would seem handy to
  designate the safe position as a set of coordinates and then just to recall them.  
  Make sense?  
  
• #589 by dbhyslop on 20 Dec, 2006 00:55
• Quote

  mkirk - 19/12/2006  6:05 PM
  
  So far GPS is not fully processed by the shuttle computers either.  Currently the shuttle program is flying a “ramp up” test of the system.  On the last mission, STS-115, the GPS was used for the first time in the primary (PASS) general purpose computers.  The plan was to let the PASS GPCs use the GPS in the processing scheme for a little while and then inhibit them from the NAV scheme and land using the standard navigation scheme (i.e. air data probe derived data).  However, GPS worked so well and accurately that Mission Control told the crew to keep it instead of the “Air Data”.  In other word the GPS prediction of the orbiter’s Stated Vector was more accurate than the standard Air Data prediction.  
  

  
  This is fascinating.
  
  My father is a soon-to-be-retired airline pilot.  He has a story about flying with a guy who brought a GPS along, back when they were the new thing and only, well, airline captains could afford them.  The idea was they would see how accurate it was based against the airplane's inertial navigation system.
  
  Now, of course, they know that they were actually seeing how accurate the INS was against the GPS!
  
  Dan
• #590 by Jim on 20 Dec, 2006 01:11
• Quote

  EW-3 - 19/12/2006  7:56 PM
  
  was wondering about EVAs....
  When Beamer was performing his magic, to get around he had to feed instructions constantly to the arm drivers..
  Is there a capability to go to fixed points without all the dialog?  
  For example in yesterdays excercise, he frequently had to go back to the same safe position.  It would seem handy to
  designate the safe position as a set of coordinates and then just to recall them.  
  Make sense?  
  

  
  safe position is relative to where the arm is mounted and/or if it is on the MT.  Also what would the EV astronaut use for reference. He has no display or measurement system.  A jumble of numbered coordinates would have little meaning to him
• #591 by Jim on 20 Dec, 2006 01:11
• Quote

  mkirk - 19/12/2006  6:05 PM
  
  

  Quote

  shuttlepilot5 - 18/12/2006  11:55 PM
  
  i just got 1 question about the landing. how do they do it?
  I mean, im used to how a commercial airliner lands by using the ILS system. Im sure you guys are familiar with the common civil aviation ILS system.
  
  but do the space shuttle use a similar system like the ILS? Or do they just track the runway visualy?
  I think the pilot of the shuttle must have some sort of "navigation/landing system". But i dont know much about the space shuttle....so it would be great if you guys could just explain the basics of the landing(ILS)
  
  

  
  The shuttle uses several different sources of data for Navigation Processing by the General Purpose Computers, normally referred to as NAV.
  
  NAV generates 3 separate state vectors.  A state vector is the calculation of the orbiter’s position and velocity at a specific time.  NAV continuously propagates the state vector using the equations of motion (thank you Mr. Newton).  A KALMAN filter is used to blend all of the various sensors into those calculations.  The sensors I am referring to are DRAG H (or drag altitude, which in simple terms is an aerodynamic model of the atmosphere's effect on the orbiter), TACAN (same as a VORTAC), Air Data Probes (similar to the PITOT STATIC system on conventional airplanes), MLS (which is the shuttle’s version of the ILS – it is a very precise system), GPS, and Radar Altimeters.
  
  I have attached a pdf chart of how when the various sensors are used at the very bottom of this post.  For instance the MLS is not really affective until around 18,000-15,000 feet which is when the orbiter is rolling out on final.
  
  The Radar Altimeters are not processed by NAV, they are only used for crew displays and become effective as the orbiter descends thru 5000 feet.
  
  So far GPS is not fully processed by the shuttle computers either.  Currently the shuttle program is flying a “ramp up” test of the system.  On the last mission, STS-115, the GPS was used for the first time in the primary (PASS) general purpose computers.  The plan was to let the PASS GPCs use the GPS in the processing scheme for a little while and then inhibit them from the NAV scheme and land using the standard navigation scheme (i.e. air data probe derived data).  However, GPS worked so well and accurately that Mission Control told the crew to keep it instead of the “Air Data”.  In other word the GPS prediction of the orbiter’s Stated Vector was more accurate than the standard Air Data prediction.  
  
  If you saw the post landing press conference then you heard a 10 minute dissertation on how this worked from an obviously pleased Leroy Cain.  Cain used to be a GNC (guidance, navigation, and control) Flight Controller in Mission Control…so he is very familiar with the system.
  
  Anyway the plan is to use the GPS again on this flight (116) as part of the ramp up program before flying a full GPS flight on STS-117.
  
  Mark Kirkman
  
  P.S.
  
  I wrote a little blurb on how the very last part of the final approach is flown in the shuttle on the first Shuttle Q&A thread here:
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=625&start=271
  
  

  
  You the man, Mark
• #592 by rosbif73 on 20 Dec, 2006 13:28
• Quote

  psloss - 19/12/2006  11:17 PM
  
  Based on what Bill Harwood wrote today, White Sands would be programmatic problem:
  
  from "SR-93 (12/19/06): Early weather forecast 'iffy' for Friday"
  http://www.cbsnews.com/network/news/space/current.html
  
  Excerpt:
  

  Quote

  NASA wants to avoid a landing in New Mexico if at all possible because it would take an estimated 45 days to bring in cranes and other equipment needed for mounting the shuttle atop a transport jet for return to Florida.

  
  Wasn't there also a problem with sand from the landing strip resulting in major TPS work being required after STS-3 (the only White Sands landing)?
  
  Given that there is apparently little equipment stationed at WSSH, what real advantage does it offer over other CONUS emergency landing sites?
• #593 by DaveS on 20 Dec, 2006 13:41
• Quote

  rosbif73 - 20/12/2006  3:11 PM
  Wasn't there also a problem with sand from the landing strip resulting in major TPS work being required after STS-3 (the only White Sands landing)?
  

  That was from a dust storm, not during touchdown and rollout.
• #594 by psloss on 20 Dec, 2006 13:49
• Quote

  rosbif73 - 20/12/2006  9:11 AM
  
  Given that there is apparently little equipment stationed at WSSH, what real advantage does it offer over other CONUS emergency landing sites?

  Generally favorable weather and long runways.  (Perhaps vice versa.)
  
• #595 by joebacsi on 20 Dec, 2006 21:04
• I'd really like to ask that on exactly what supplies does the number of days that a shuttle can spend in space depends?  Because I remember like Columbia having a mission when it was up there for like more then 17 days... So what would it take to prepare ISS missions for a possibility of longer trips so they wouldn't face the concerns they have now, and like they could extend missions easier? I remember reading that the shuttle has the nominal capability of a 28 day mission... Sorry if this had already been asked...
• #596 by DaveS on 20 Dec, 2006 21:31
• Quote

  joebacsi - 20/12/2006  10:47 PM
  
  I'd really like to ask that on exactly what supplies does the number of days that a shuttle can spend in space depends?  Because I remember like Columbia having a mission when it was up there for like more then 17 days... So what would it take to prepare ISS missions for a possibility of longer trips so they wouldn't face the concerns they have now, and like they could extend missions easier? I remember reading that the shuttle has the nominal capability of a 28 day mission... Sorry if this had already been asked...

  Columbia had been modified to accept an so called Extended Duration Orbiter(EDO) cryogenic kit.
  The EDO cryo kit had additional LH2 and LOX tanks for the Power Reactant Storage and Distribution(PRSD) system.
  
  This enabled Columbia to have longer duration missions than the other orbiters as the EDO cryo kit provided alot more cryogenic reactants for the three Fuel Cells.
  
  Endeavour was delivered with a capability to accept TWO EDO cryo kits enabling her to go on 28-day missions.
  But this capability was removed to save weight when ISS moved to it's current high inclination orbit-
• #597 by Jim on 20 Dec, 2006 23:42
• Quote

  joebacsi - 20/12/2006  4:47 PM
  
  I'd really like to ask that on exactly what supplies does the number of days that a shuttle can spend in space depends?  Because I remember like Columbia having a mission when it was up there for like more then 17 days... So what would it take to prepare ISS missions for a possibility of longer trips so they wouldn't face the concerns they have now, and like they could extend missions easier? I remember reading that the shuttle has the nominal capability of a 28 day mission... Sorry if this had already been asked...

  
  This was covered in the Shuttle Q&A thread in more detail.  Nominal capability is 11.  Extended is 17 and 28 was a dream.  The SSPT(sp) mods will make it longer. This is all in the other thread
• #598 by hutchel on 20 Dec, 2006 23:45
• OK Landing track question -
  I've noticed that all of the landing tracks come in from the west - this seems to limit the landing opportunities.  Does the shuttle not have sufficient energy from the 2 orbits prior to the ones use to make it safely to the runway?
  
  I know in the early stages of the entry, the shuttle is not powered (all the way to the ground) and is basically flying a "ballastic" trajectory, but at some point the control surfaces become effective and the shuttle starts to behave more and more like an airplane, at which point a turn more to the north and eventually west would be conceivable - this would seem to give them a couple of more landing opportunities.  
  
  
• #599 by Jim on 21 Dec, 2006 00:05
• Cross range is the distance on either side of orbit track the orbiter can reach. The Shuttles cross range was to be 1000nmi and is 800nmi (mkirk can correct this).   The distance between orbit tracks is much greater than this.  The orbiter doesn't become an "real" actual aircraft until less than 100,000 feet (mkirk, help).  the shutttle is still using the RCS sometimes in view of the landing sites.  
  
  Not even a regular aircraft dead sticking would have that capability.  glideslope would need to be almost flat.