Shuttle Questions Q & A (Part 4)

#200 by jscott227 on 05 Dec, 2007 02:48
Thanks guys, for the response.

John
#201 by Lee Jay on 05 Dec, 2007 03:07
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Jorge - 4/12/2007 7:38 PM

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psloss - 4/12/2007 7:19 PM

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Lee Jay - 4/12/2007 8:02 PM

One time I saw a Shuttle landing on TV it was intermittently leaving a contrail (on the order of a second at a time). The PAO said they were burning off excess fuel. This was probably within a minute or two of landing. Were they firing aft RCS or something?
I believe the RCS are used to help with yaw control until around Mach 1. (More than a minute before landing...usually still approaching the HAC.)

That's correct.

Thanks to both of you. As usual, PAO didn't explain it correctly.

The reason I thought it was only a minute or two before touchdown is because of the good-quality closeup images I was seeing (like those posted). I keep forgetting just how long the lenses are those guys have available!
#202 by pr1268 on 05 Dec, 2007 06:37
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Jorge - 28/11/2007 1:44 PM
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Susan27 - 28/11/2007 1:27 PM Hi, I just saw some launch vids of the shuttle where you can listen to CAPCOM transmission. Shortly before MECO their comes a command from CAPCOM saying... "...Go for the "posess" (rem.: sorry, but I cant identify this word), go for the pitch..." What does that command mean exactly? Thanks very much!
"Go for the plus X" - after ET SEP, the orbiter performs an automatic -Z ("up") maneuver to separate from the tank. Shortly after that, the crew performs a manual +X ("forward") maneuver to sweep the ET umbilical well camera along the ET at close range to get good photos of the condition of the ET. The manual +X is not performed in the event of certain malfunctions, so a "Go" from MCC is required to perform it. "Go for the pitch" - after the +X maneuver the crew photographs the ET using handheld cameras through the overhead windows. To point the windows at the ET, the crew performs a manual pitch maneuver. This is also not performed under certain conditions so it also requires a "go".
I've a related question about axis notation in 3D Cartesian coordinates with regards to the Shuttle. Is my understanding below correct?
Positive X-axis points outwards along the long axis of the Shuttle body through its nose
Positive Y-axis points outwards from the starboard wing of the Shuttle
Positive Z-axis points upwards from the cargo bay perpendicular to the X-Y plane
Also, might someone clarify what is a positive pitch-, roll-, and yaw- rotation with respect to the axes? (E.g., is it the "right hand rule"?) I get confused sometimes. Thanks in advance for any discussions on this!
#203 by psloss on 05 Dec, 2007 10:07
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Jorge - 4/12/2007 9:41 PM

You sure you're not confusing the umbilical camera with the LOX feedline camera?

(The feedline camera is made by Ecliptic, but I'm not sure about the umbilical camera... NASA had a still camera in the umbilical well since STS-1, but made a lot of changes after 107.)
You're right, I completely confused the question. (That's what I get for answering quickly.)
#204 by Jim on 05 Dec, 2007 13:08
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pr1268 - 5/12/2007 2:37 AM

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Jorge - 28/11/2007 1:44 PM
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Susan27 - 28/11/2007 1:27 PM Hi, I just saw some launch vids of the shuttle where you can listen to CAPCOM transmission. Shortly before MECO their comes a command from CAPCOM saying... "...Go for the "posess" (rem.: sorry, but I cant identify this word), go for the pitch..." What does that command mean exactly? Thanks very much!
"Go for the plus X" - after ET SEP, the orbiter performs an automatic -Z ("up") maneuver to separate from the tank. Shortly after that, the crew performs a manual +X ("forward") maneuver to sweep the ET umbilical well camera along the ET at close range to get good photos of the condition of the ET. The manual +X is not performed in the event of certain malfunctions, so a "Go" from MCC is required to perform it. "Go for the pitch" - after the +X maneuver the crew photographs the ET using handheld cameras through the overhead windows. To point the windows at the ET, the crew performs a manual pitch maneuver. This is also not performed under certain conditions so it also requires a "go".
I've a related question about axis notation in 3D Cartesian coordinates with regards to the Shuttle. Is my understanding below correct?
Positive X-axis points outwards along the long axis of the Shuttle body through its nose
Positive Y-axis points outwards from the starboard wing of the Shuttle
Positive Z-axis points upwards from the cargo bay perpendicular to the X-Y plane
Also, might someone clarify what is a positive pitch-, roll-, and yaw- rotation with respect to the axes? (E.g., is it the "right hand rule"?) I get confused sometimes. Thanks in advance for any discussions on this!

Picture of all axises are pictured.
http://spaceflight1.nasa.gov/shuttle/reference/

Right hand Rules!
#205 by MKremer on 05 Dec, 2007 18:05
Kodak and Nikon appear to have technology/hardware sharing agreements (Kodak and Nikon cameras share digital imaging technologies).
#206 by TJL on 06 Dec, 2007 00:07
Astronauts that have returned from long duration tours aboard ISS are usually not able to participate in any post landing activities with the other crew members.
Since Dan Tani will have been aloft only about 60 days, do you think he will be able to join his crew mates when they leave the shuttle?
Thanks.
#207 by Patriot1776 on 06 Dec, 2007 21:27
Where can I find on here detailed info on the ET ECO sensors?
#208 by Rob in KC on 06 Dec, 2007 21:32
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Patriot1776 - 6/12/2007 4:27 PM

Where can I find on here detailed info on the ET ECO sensors?

http://www.interspacenews.com/interspace%20News%20Web%202/sections/In%20focus/ECO%20Sensors.htm
#209 by Susan27 on 07 Dec, 2007 10:12
I am wondering at the moment - concerning the actual scrub of STS-122 launch - how the ET is constructed in general. I saw the drawing mentioned above (ECO-sensors) and questioned myself why the Lo2-tank (1/3 of the ET-volume) is located at the top and the Lh2-tank (2/3) at the bottom.

1) What is the reason that Lo2 is at the top then?

2) I understand that the LO2 is the oxydizer for the LH2, is that correct so far? Is that the reason that the Lo2-tank (volume) is only 1/3?

3) I understand (please correct me) that both elements run from ET through ET/shuttle umbilical connector towards SSMEs. How (pipes etc.?) and specially at which location of the aft. shuttle`s SSMEs are the 2 elements combined leading to this massive explosion then...?

Thanks very much in advance!
(Hope for launch at Sat.)
#210 by Susan27 on 07 Dec, 2007 10:36
Hi,

I have a question concerning the arming status of the ET`s ECOs:

In the text linked above it is said...that at a nominal ascent velocity is the only shutdown cue. In fact the GPCs will not even accept a shutdown command from the ECO sensors unless they have been armed.

The command to arm the ECO sensors is issued only if one of the following conditions applies:

- Two engines have failed, or

- A flight specific arming mass has been reached. This mass is usually the total mass of propellant remaining in the external tank that provides the shuttle the ability to perform a Transoceanic Abort Landing (TAL) should the sensors issue a cutoff command immediately upon arming...

I dont understand the meaning of this last sentence. Does that mean that ECOs are armed as long as a TAL-abort is availabe during ascent?

Thanks in advance

Kind regards
#211 by Jim on 07 Dec, 2007 11:00
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Susan27 - 7/12/2007 6:12 AM

I am wondering at the moment - concerning the actual scrub of STS-122 launch - how the ET is constructed in general. I saw the drawing mentioned above (ECO-sensors) and questioned myself why the Lo2-tank (1/3 of the ET-volume) is located at the top and the Lh2-tank (2/3) at the bottom.

1) What is the reason that Lo2 is at the top then?

2) I understand that the LO2 is the oxydizer for the LH2, is that correct so far? Is that the reason that the Lo2-tank (volume) is only 1/3?

3) I understand (please correct me) that both elements run from ET through ET/shuttle umbilical connector towards SSMEs. How (pipes etc.?) and specially at which location of the aft. shuttle`s SSMEs are the 2 elements combined leading to this massive explosion then...?

Thanks very much in advance!
(Hope for launch at Sat.)

1. For CG considerations. Also it puts the intertank in the right spot for SRB attachment.

2. Correct. The volume ration is related to the density of the propellants and the mixturre ratio needed for the engines.

3. Umbilicals are also pipes (not just electrical). There are two ducts leading into the orbiter, one at each aft Orbiter/ET attach point
#212 by pippin on 07 Dec, 2007 12:28
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Susan27 - 7/12/2007 12:36 PM

I dont understand the meaning of this last sentence. Does that mean that ECOs are armed as long as a TAL-abort is availabe during ascent?

It means that the ECOs are only armed when it is made sure they can reach the TAL site in case they immediately engage after being armed. You don't need them in the first phase of the flight since your tank is full and it takes a while to use up propellant. If the tank runs dry before you can reach the TAL sites you don't have to care about anything anymore.
But if the ECOs accidentally shut off all engines before you got enough speed to reach a TAL site you are in trouble.

Greetings from Berlin to Berlin ;-)
#213 by SiameseCat on 07 Dec, 2007 13:03
If the launch has to be flown manually, will ET Sep and the -Z translation occur automatically, or will those also have to be manually commanded?
#214 by Jim on 07 Dec, 2007 14:50
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SiameseCat - 7/12/2007 9:03 AM

If the launch has to be flown manually, will ET Sep and the -Z translation occur automatically, or will those also have to be manually commanded?

Define "manually" flown
#215 by SiameseCat on 07 Dec, 2007 15:44
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Jim - 7/12/2007 10:50 AM

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SiameseCat - 7/12/2007 9:03 AM

If the launch has to be flown manually, will ET Sep and the -Z translation occur automatically, or will those also have to be manually commanded?

Define "manually" flown

CSS Steering is used during second stage.
#216 by psloss on 07 Dec, 2007 16:03
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SiameseCat - 7/12/2007 11:44 AM

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Jim - 7/12/2007 10:50 AM

Define "manually" flown

CSS Steering is used during second stage.
CSS could be used in a severe failure case, but it's definitely not normal -- for powered flight.
#217 by mkirk on 07 Dec, 2007 16:27
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SiameseCat - 7/12/2007 8:03 AM

If the launch has to be flown manually, will ET Sep and the -Z translation occur automatically, or will those also have to be manually commanded?

If you happen to be flying CSS (control stick steering) on Ascent then you also have to take manual throttles which means you also have to manually command MECO.

ET Sep and the Minus Z Translation are automatic as long as the “MECO CONFIRMED” flag has been set in the software. In other words the GPCs (General Purpose Computers) must recognize the fact that all of the main engines have been shut down.

In the case of a manual MECO the pressing of the three main engine pushbuttons located on the center console should be enough for this. If the buttons aren’t working correctly (i.e. comm faulted) there are other options to “mode guidance” and set “MECO Confirmed” such as manually transitioning the flight software to OPS 104 by typing that in on the keyboards.

To answer your question they SHOULD occur automatically depending on the nature of the failure that caused you to take over manual flying in the first place.

Mark Kirkman
#218 by pr1268 on 07 Dec, 2007 16:37
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mkirk - 7/12/2007 11:27 AM
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SiameseCat - 7/12/2007 8:03 AM If the launch has to be flown manually, will ET Sep and the -Z translation occur automatically, or will those also have to be manually commanded?
If you happen to be flying CSS (control stick steering) on Ascent then you also have to take manual throttles which means you also have to manually command MECO. ET Sep and the Minus Z Translation are automatic as long as the “MECO CONFIRMED” flag has been set in the software. In other words the GPCs (General Purpose Computers) must recognize the fact that all of the main engines have been shut down. In the case of a manual MECO the pressing of the three main engine pushbuttons located on the center console should be enough for this. If the buttons aren’t working correctly (i.e. comm faulted) there are other options to “mode guidance” and set “MECO Confirmed” such as manually transitioning the flight software to OPS 104 by typing that in on the keyboards. To answer your question they SHOULD occur automatically depending on the nature of the failure that caused you to take over manual flying in the first place. Mark Kirkman
I gather that controlling the Shuttle manually during ascent is very difficult, given the sheer speed of which events occur. Can this be done? Or has it been done on any previous mission?
A scene from the Ron Howard movie Apollo 13 where the astronauts perform a course correction maneuver without the computer's assistance seems to resonate in my mind right now... Any comments from the more-enlightened STS folks??
#219 by pr1268 on 07 Dec, 2007 16:43
Rob in KC:

Thank you for the link. What an incredibly straightforward (and enlightening) discussion of the ECO sensors and their role in performance and risk management!