Shuttle Questions Q & A (Part 3)

• #700 by Selmuir on 04 Aug, 2007 18:25
• Quote

  Selmuir - 4/8/2007  1:03 PM
  
  Hi ,
  
  
  Sorry for all these questions but i serched for a topic like this and i couldent find any so anyway heres my question,
                   
  If i wanted to become a Astronaut where would i start because i live in Scotland ?
  
  Thanks
  
  

  
  Anyone ?
• #701 by TFGQ on 04 Aug, 2007 19:05
• i have a question at T-3hrs i noticed water comming out of the side of the water tower what is the reason for that
• #702 by MKremer on 04 Aug, 2007 19:40
• Quote

  Selmuir - 4/8/2007  1:03 PM
  If i wanted to become a Astronaut where would i start because i live in Scotland ?
  
  Thanks
  

  "Astronaut" isn't a career (and won't be for a long, long time). If you read through all the bio's for both NASA and ESA astronauts, all those people already had established, successful careers in lots of different fields (most with advanced college degrees) for many years until they applied and were finally accepted for astronaut training. Even the Shuttle pilots are mostly career military (with test pilot training) and have years and years of flying experience (and also have advanced degrees).
  
  The other option would be new.space - private spaceflight companies - but even then they'll likely only be hiring highly experienced test pilots for a while.
• #703 by MKremer on 04 Aug, 2007 19:41
• Quote

  TFGQ - 4/8/2007  2:05 PM
  
  i have a question at T-3hrs i noticed water comming out of the side of the water tower what is the reason for that

  
  Overflow from pumping water to top off the water tank.
  
• #704 by brahmanknight on 04 Aug, 2007 20:51
• How is power supplied to the orbiter on the ground?
• #705 by Jim on 04 Aug, 2007 22:02
• Quote

  brahmanknight - 4/8/2007  4:51 PM
  
  How is power supplied to the orbiter on the ground?

  
  Through the T-0 umbilicals
• #706 by SpaceNutz SA on 05 Aug, 2007 06:31

• Quote

  Danny Dot - 4/8/2007 8:21 PM

  Quote

  SpaceNutz SA - 4/8/2007 1:07 PM What determines the launch window on an ISS bound flight? Is it the position of the ISS relative to KSC? If so why then does it take about 2 days to play catch-up once in orbit?

  Let me try to answer this using simple English instead of NASA jargon. The launch window is defined by the left and right -- crosstrack -- part of getting into the right orbit. When the ground track of station is over Florida, the shuttle launches. The station can be right over Florida, or it can be on the other side of the Earth. It doesn't matter. The shuttle launches anyway. Catching up over time is the fore and aft part of getting to station. It is possible, if the fore and aft is just right, to rendezvous sooner -- Gemini used to rendezvous a couple of hours after launch. Some of the reasons for the delay in rendezvous is to give the crew time to transition the shuttle to orbit ops, day 2 is now dedicated to looking over the shuttle's thermal protection system, and sometimes crew members have motion sickness the first couple of days. Even if the orbital mechanics line up for a rendezvous on day 1 or day 2, the rendezvous is slowed down for other scheduling reasons. The rate of catch up is based on how much lower the shuttle is than the station. If at the same altitude, there is no catchup. If you need to catch up a lot, the shuttle is kept at a lower orbit. Danny Deger

  Thanks Danny - nice explanation which is partly understood   

  So if I understand:  the ground track over the launch site is important to put the shuttle in the same orbit as the station although with some displacement in distance.  The launch trajectory of the shuttle is designed to put the shuttle in the same 51.6deg inclination as the ISS - it's just a case of waiting for the ISS to be on the correct ground track so that the 2 orbits co-incide.  Am I understanding this correctly?   One part I don't understand is why the launch window is so short.  The ISS ground track will be 'over' the launch site for an entire orbit which is 92 minutes. Why then is the launch window only in the order of 10 min's long?   The part about delayed rendezvoux for mission activities is understood.

  Is there a good online tutorial on orbital mechanics?

  Thanks

• #707 by MKremer on 05 Aug, 2007 07:00
• It may be easier to think of the ISS orbit track as a solid line (a circle around the Earth, angled at 51.6 degrees) - as the Earth rotates, that solid line keeps moving further West every second (the orbit is fixed - the Earth rotates underneath it).
  
  If you think about it that way, you can see the Shuttle has a limited period of time to launch, so that by the time it reaches orbit it's own orbital line (which by then is now also moving West every second) closely matches the ISS orbit line. If it launches too early, or too late, it will require too much extra propellent for additional burns to align both orbits.
  
  That limited time is the launch window. If they manage to get the launch off exactly right, the orbiter will only need tiny alignment corrections and preserve propellent for the rendezvous burns themselves.
  
  Try this link for orbital mechanics:  http://www.braeunig.us/space/orbmech.htm
  
  
• #708 by SpaceNutz SA on 05 Aug, 2007 08:52

• Quote

  MKremer - 5/8/2007 9:00 AM It may be easier to think of the ISS orbit track as a solid line (a circle around the Earth, angled at 51.6 degrees) - as the Earth rotates, that solid line keeps moving further West every second (the orbit is fixed - the Earth rotates underneath it). If you think about it that way, you can see the Shuttle has a limited period of time to launch, so that by the time it reaches orbit it's own orbital line (which by then is now also moving West every second) closely matches the ISS orbit line. If it launches too early, or too late, it will require too much extra propellent for additional burns to align both orbits. That limited time is the launch window. If they manage to get the launch off exactly right, the orbiter will only need tiny alignment corrections and preserve propellent for the rendezvous burns themselves. Try this link for orbital mechanics: http://www.braeunig.us/space/orbmech.htm

  Many thanks for that - much clearer now.

• #709 by HarryM on 05 Aug, 2007 14:10
• The documentation included in Orbiter http://orbit.medphys.ucl.ac.uk/orbit.html explains a great deal about orbital mechanics. Also lets you play with them (fun!)
• #710 by Danny Dot on 05 Aug, 2007 14:33
• Quote

  SpaceNutz SA - 5/8/2007  3:52 AM
  
  

  Quote

  MKremer - 5/8/2007 9:00 AM It may be easier to think of the ISS orbit track as a solid line (a circle around the Earth, angled at 51.6 degrees) - as the Earth rotates, that solid line keeps moving further West every second (the orbit is fixed - the Earth rotates underneath it). If you think about it that way, you can see the Shuttle has a limited period of time to launch, so that by the time it reaches orbit it's own orbital line (which by then is now also moving West every second) closely matches the ISS orbit line. If it launches too early, or too late, it will require too much extra propellent for additional burns to align both orbits. That limited time is the launch window. If they manage to get the launch off exactly right, the orbiter will only need tiny alignment corrections and preserve propellent for the rendezvous burns themselves. Try this link for orbital mechanics: http://www.braeunig.us/space/orbmech.htm

  Many thanks for that - much clearer now.

  
  Even I understand it now :-)
  
  Danny Deger
• #711 by brahmanknight on 05 Aug, 2007 19:06
• What moves the RSS?  A modified locamotive?
• #712 by Lee Jay on 05 Aug, 2007 19:10
• Quote

  brahmanknight - 5/8/2007  1:06 PM
  
  What moves the RSS?  A modified locamotive?

  
  Small electric motors.
  
  http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=29136
• #713 by el_nino on 06 Aug, 2007 00:02
• With the talk of launch windows earlier on this page, I have a question about them.  I understand how and why we have a window for the missions that rendevous with the ISS.  However, my question is what about the earlier shuttle missions?  What determined a launch window for one of the missions that were going to deploy a communications satellite?  There was nothing in orbit they were already trying to catch up to.  Now, I understand there are things such as the amount of daylight at the TAL sites, etc. but was there more to it than that?  For instance, I witnessed the launch of STS-29 and if I recall they were launching one of the TDRS satellites on that mission.  Lift off happened shortly before 10am that day after a long delay because of fog.  They had a 2.5 hour launch window that day.  What determined the length of that window?  It certainly wasn't dark at the TAL sites by then yet.
• #714 by Danny Dot on 06 Aug, 2007 00:17
• Quote

  el_nino - 5/8/2007  7:02 PM
  
  With the talk of launch windows earlier on this page, I have a question about them.  I understand how and why we have a window for the missions that rendevous with the ISS.  However, my question is what about the earlier shuttle missions?  What determined a launch window for one of the missions that were going to deploy a communications satellite?  There was nothing in orbit they were already trying to catch up to.  Now, I understand there are things such as the amount of daylight at the TAL sites, etc. but was there more to it than that?  For instance, I witnessed the launch of STS-29 and if I recall they were launching one of the TDRS satellites on that mission.  Lift off happened shortly before 10am that day after a long delay because of fog.  They had a 2.5 hour launch window that day.  What determined the length of that window?  It certainly wasn't dark at the TAL sites by then yet.

  
  The time the crew can stay in the cockpit is often the limit for these flights.
  
  Danny Deger
• #715 by Jim on 06 Aug, 2007 00:27
• crew on back times was a 2.5 to 3 hour limit
• #716 by mkirk on 06 Aug, 2007 03:59
• Quote

  Jim - 5/8/2007  7:27 PM
  
  crew on back times was a 2.5 to 3 hour limit

  
  More precisely the LCC (launch commit criteria) is 5 hours 15 minutes in the Launch Seat Posture, so subtract Ingress time and that gives you the availabel hold time based on being in the seat.
  
  Of course as most of you all know the current launch windows never come up against this constraint.
  
  Mark Kirkman
• #717 by STS-500Cmdr on 06 Aug, 2007 05:57
• The 5 plus hours rule would apply to missions such as a Spacelab mission
• #718 by psloss on 06 Aug, 2007 09:56
• Quote

  STS-500Cmdr - 6/8/2007  1:57 AM
  
  The 5 plus hours rule would apply to missions such as a Spacelab mission

  Prior to the station rendezvous/docking missions that began in 1995, there were others besides the Spacelab missions...IIRC, the last long hold at T-9 minutes was probably for STS-64 (approx. 2 hours on a mid/late afternoon in Sept. 1994).
  
  After STS-63, it was pretty much station, Spacelab, and HST servicing missions (the latter usually having approx. 60 minute launch windows), with a few exceptions like STS-95 or STS-99.
  
• #719 by henrycheck on 06 Aug, 2007 10:22
• Quote

  el_nino - 5/8/2007  8:02 PM
  
  With the talk of launch windows earlier on this page, I have a question about them.  I understand how and why we have a window for the missions that rendevous with the ISS.  However, my question is what about the earlier shuttle missions?  What determined a launch window for one of the missions that were going to deploy a communications satellite?  There was nothing in orbit they were already trying to catch up to.  Now, I understand there are things such as the amount of daylight at the TAL sites, etc. but was there more to it than that?  For instance, I witnessed the launch of STS-29 and if I recall they were launching one of the TDRS satellites on that mission.  Lift off happened shortly before 10am that day after a long delay because of fog.  They had a 2.5 hour launch window that day.  What determined the length of that window?  It certainly wasn't dark at the TAL sites by then yet.

  
  
  I think the question here might be more general like “Why is there a launch window at all?” On such missions as TDRS launches “Why not just always launch at 10:30 AM, say?”
  
  Possible considerations would be the allowable time between launch and the two IUS firings (thermal and power issues), the need to have the IUS burns occur within the tracking view of the IUS control center at White Sands, and a maximum amount of drift from the initial geostationary longitude to the final orbital location.