Shuttle Questions Q and A (2)

• #140 by Rocket Guy on 13 Jun, 2006 00:02
• No, there is nothing visible left by the time we go out there. NO2 is deadly in concentrated amounts, and has a brownish color (that may add to give the SRB exhaust its somewhat darker color). It smells but I don't think it's concentrated anymore. I've never had any side effects (that I recall!).
  
  The HCl and A2O3 residue that covers things sometimes feels as though it burns a little, but that may be placebo :-) I sometimes bring gloves if I remember. Of course, for the Shuttle there isn't much of it. But on ELVs where we can put our cameras under the SRB if we wanted to it's a different story.
  
  I wish I had some photos but apparently not.
• #141 by zinfab on 14 Jun, 2006 21:27
• I have finally read all 50 pages of this (and the first) Q&A thread. Wow. Thanks so much to all of you. I've been a NASA junkie for years and this is the first in-depth source of information I've ever found. Glad you're all here! It's like drinking from a fire hose! This is, by far, the most intelligent forum of discussion I've ever visited.
  
  Q- What is the maximum duration a space shuttle SHOULD be able to remain in LEO (attached or not attached to the ISS) with enough fuel/power to return to earth? A range will be fine--I know different configs/aborts/etc. affect this.
  
  
• #142 by astrobrian on 15 Jun, 2006 01:40

• Quote

  zinfab - 14/6/2006  4:14 PM  I have finally read all 50 pages of this (and the first) Q&A thread. Wow. Thanks so much to all of you. I've been a NASA junkie for years and this is the first in-depth source of information I've ever found. Glad you're all here! It's like drinking from a fire hose! This is, by far, the most intelligent forum of discussion I've ever visited.   

   

  That was my assesment when I stumbled into this lair   welcome to the site

  As for your question on shuttle duration. I know there have been missions of 14 days in length. Someone here will be able to get more specific than that though. 

   

• #143 by Jim on 15 Jun, 2006 01:45
• Shuttle mission duration depends on which orbiter, the number of PDRS tanks installed, whether the EDO tanks are installed (these were destroyed with Columbia) and for the some of the future ISS missions, whether the SSPTS will be used.
  
  Std 10 +2 contingency
  EDO 18 + 2
  SSPTS 21 +2
  
  
• #144 by zinfab on 15 Jun, 2006 01:59
• ok, hypothetical. plan for a nominal maximum duration mission, push the safety margin on orbit, and bring her home safely. how long?
• #145 by zinfab on 15 Jun, 2006 13:47
• that helps, jim. Thanks!
• #146 by GLS on 23 Jun, 2006 13:29
• Interesting question: Where does the Tail Cone attach to the orbiter? SSME gimbal berings?
• #147 by Jim on 23 Jun, 2006 13:49
• The SSMEs  stay on and are covery by the tail cone.  It attaches to the perimeter of the aft end
• #148 by shuttlefan on 24 Jun, 2006 00:57
• Is there any danger whatsoever with two stacked SRBs in the VAB? For example, could a cigarette spark get too close and ignite one of them--try not to laugh at me!!
• #149 by astrobrian on 24 Jun, 2006 01:00
• I wouldn't think anything would happen from a distance as it is a solid so no fumes are there to ignite, as for a spark setting one off I am not sure
• #150 by shuttlefan on 24 Jun, 2006 01:04
• I read that in the pre-Challenger days, the astronauts didn't bother learning too much about the SRBs because they couldn't control them anyway and did that change after Challenger?
• #151 by mkirk on 25 Jun, 2006 17:03
• Quote

  shuttlefan - 23/6/2006  7:51 PM
  
  I read that in the pre-Challenger days, the astronauts didn't bother learning too much about the SRBs because they couldn't control them anyway and did that change after Challenger?

  
  That is still more or less the case.  Astronauts get some basic system overview briefings for the SRBs and a rundown of how they are prepared/loaded with propellant at ATK and then shipped to and processed at the Kennedy Space Center.
  
  Astronauts are also given briefings on the sensitive subject of the Range Safety System.  The external tanks no longer fly with such a system because it really isn’t necessary but the SRBs still have it for obvious reasons.
  
  During flight training sessions in the SMS (shuttle mission simulator) there is very little exposure to SRB related problems.  Some problems such as a stuck nozzle actuator or burn performance issues (i.e. the SRBs can burn slightly hotter or cooler than expected) are really the only cases presented during training but that is really all the crew can deal with.
  
  The SRBs simply have to work every time!
  
  Mark Kirkman
  
  
  
• #152 by rfoshaug on 28 Jun, 2006 10:56
• I've got a couple of questions about the ascent and descent phases of space shuttle missions. I've been trying to fly some shuttle missions in Orbiter (www.orbitersim.com - excellent sim BTW) and want to do it as realistically as possible.
  
  1. For a mission to ISS, the ascent phase must of course be timed so that the orbital plane of ISS passes over the launch site at the time of launch (or probably a few seconds/minutes before launch to give the shuttle some time to accelerate - but how much?). But once the shuttle is in orbit, there's bound to be some deviation between shuttle orbit and ISS orbit. This deviation must be compensated for by orbital plane adjustments using the OMS engines. I'm quite satisfied if I get below 1 degree difference between my orbit and that of the ISS. How large a deviation is normal in real shuttle operations?
  
  2. When, or more specifically, where does the de-orbit burn start? How many miles/kilometers from the landing site? For example for a return to KSC from the orbital plane of ISS - where does the burn start?
  
  
  3. What is the altitude at the point of the de-orbit burn? I usually place the orbiter in a 200-to-250-kilometer circular orbit before the de-orbit burn instead of de-orbiting directly from ISS altitude. Is this how it's done on the real orbiters?
  
  
  4. How long is the burn? I read somewhere 2.5 minutes, but what determines the length of the burn and the delta-v? Is it to place the calculated impact point (assuming no atmosphere and assuming that the perigee of the orbit is placed below the surface) at a specific place, or is it to place the perigee at a specific altitude?
  
  
  5. How much (percentage) OMS fuel is usually in the tanks at various flight stages such as ISS docking, start of de-orbit burn and after landing?
  
  
  If anyone knows this stuff, any answers would be highly appreciated.  
• #153 by Jim on 28 Jun, 2006 12:48
• Look up simcosmos on the web, they do orbitersims and can help you.  Also search this site for orbitersim.  Also seach the web on shuttle entry
• #154 by Jamie Young on 29 Jun, 2006 02:26
• What was it that determined the size of the payload bay back at the design phase? We hear of lot about how ISS elements are built for the cargo bay, but back in the 70s, what was the cargo bay parameters designed for?
  
  Was it based on the biggest satellite it was hoped it would launch?
• #155 by Jim on 29 Jun, 2006 02:47
• the USAF required the 60' x 15' dia payload bay.  Before the USAF came onboard, it was 40 x 10 or 12, have to go look it up at home.  There wasn't any specific payload at the time, it was based on future requirement.  Existing USAF spacecraft were around 30-40 by 10 and flew on Titan-III's.  
  
  It was build it and they will come wrt 60 x 15.
• #156 by GLS on 29 Jun, 2006 09:02
• Quote

  rfoshaug - 28/6/2006  11:43 AM
  
  I've got a couple of questions about the ascent and descent phases of space shuttle missions. I've been trying to fly some shuttle missions in Orbiter (www.orbitersim.com - excellent sim BTW) and want to do it as realistically as possible.
  
  1. For a mission to ISS, the ascent phase must of course be timed so that the orbital plane of ISS passes over the launch site at the time of launch (or probably a few seconds/minutes before launch to give the shuttle some time to accelerate - but how much?). But once the shuttle is in orbit, there's bound to be some deviation between shuttle orbit and ISS orbit. This deviation must be compensated for by orbital plane adjustments using the OMS engines. I'm quite satisfied if I get below 1 degree difference between my orbit and that of the ISS. How large a deviation is normal in real shuttle operations?
  
  2. When, or more specifically, where does the de-orbit burn start? How many miles/kilometers from the landing site? For example for a return to KSC from the orbital plane of ISS - where does the burn start?
  
  
  3. What is the altitude at the point of the de-orbit burn? I usually place the orbiter in a 200-to-250-kilometer circular orbit before the de-orbit burn instead of de-orbiting directly from ISS altitude. Is this how it's done on the real orbiters?
  
  
  4. How long is the burn? I read somewhere 2.5 minutes, but what determines the length of the burn and the delta-v? Is it to place the calculated impact point (assuming no atmosphere and assuming that the perigee of the orbit is placed below the surface) at a specific place, or is it to place the perigee at a specific altitude?
  
  
  5. How much (percentage) OMS fuel is usually in the tanks at various flight stages such as ISS docking, start of de-orbit burn and after landing?
  
  
  If anyone knows this stuff, any answers would be highly appreciated.  

  
  Yes, Orbiter rocks!
  This are generic anwsers. In the end, it all depends on vehicle mass, propelants, ISS alt., etc........
  1) It's probaly better than 0.01º
  
  2) More or less on the other side of the world...
  
  3) From the ISS, you deorbit from an altitude around 200nm (370Km).
  
  4) On deorbit burn you want do dip your perigee into the atmosphere. How much depends on your altitude and the range/crossrange to the landing site. After the deorbit burn your perigee would be around 15-30nm (27-54Km). How long you burn depends on you mass. 150 seconds is tipical, but some missions burned for 120 seconds and others for 300 seconds.
  
  5) It depends on the mission, but I think you cannot have more than 22% (or is it 26%???) on landing.
• #157 by Jim on 29 Jun, 2006 11:53
• for #4, for the real shuttle, the perigee intersects with the earth's surface after deorbit burn.
• #158 by GLS on 30 Jun, 2006 08:21
• Quote

  Jim - 29/6/2006  12:40 PM
  
  for #4, for the real shuttle, the perigee intersects with the earth's surface after deorbit burn.

  
  That was for the real shuttle! Does that happen on all the flights??? I only have info on very few flights... I could be *incomplete*...
• #159 by Jim on 30 Jun, 2006 11:51
• Quote

  GLS - 30/6/2006  4:08 AM
  
  

  Quote

  Jim - 29/6/2006  12:40 PM
  
  for #4, for the real shuttle, the perigee intersects with the earth's surface after deorbit burn.

  
  That was for the real shuttle! Does that happen on all the flights??? I only have info on very few flights... I could be *incomplete*...

  
  Yes.
  
  I couldn't find deorbit burn files but the files massprop, shows the diffence in weight between deorbit burn and entry interface.  Most of the delta is the OMS burn, but there is wieght loss due to RCS firings and the APU's running.
  
  The other file has OMS-1 and -2 burn data

  ---

  massprop.pdf

  ascorb.pdf