Shuttle Q&A Part 5

[Jim]

In Kathy Sullivan podcast recently, during her first mission, STS 41-G (Challenger), after MECO, the commander, Bob Crippen made a routine radio call to MCC. But, it turned out it not MCC who reply, but an RAF pilot somewhere in GB (Challenger was over GB at the moment). So, they needed to change radio frequency on the Shuttle very often? or they had a fixed radio frequency for entire duration? 

Fixed.

And I doubt that happened.

[mkirk]

In Kathy Sullivan podcast recently, during her first mission, STS 41-G (Challenger), after MECO, the commander, Bob Crippen made a routine radio call to MCC. But, it turned out it not MCC who reply, but an RAF pilot somewhere in GB (Challenger was over GB at the moment). So, they needed to change radio frequency on the Shuttle very often? or they had a fixed radio frequency for entire duration? 

For UHF communications, there were a couple of switches above the Commander’s head that allowed the selection of 2 different Frequencies (296.8 & 259.7).  The selection of “Guard” (243.0) was also an option via the rotary switch.

This image is how the switch looked back then.

[e of pi]

Can anyone link me to any images or tours of Shuttle servicing _before_ the final flights? I found and some like this inside, but mostly after each orbiter's final flight: http://www.nycaviation.com/2012/01/photos-on-the-flight-deck-of-space-shuttle-atlantis/18911



I'm curious how much the "stripped" look was typical for flight-to-flight turnaround vs end-of-program.

[Jim]

The mid deck was stripped after every flight.
It looked like that most of time.

[e of pi]

The mid deck was stripped after every flight.
It looked like that most of time.

Thanks for the confirmation, I thought I'd read that but was having trouble finding specific documentation.

[Kyra's kosmos]

Where were the two-digit relay addresses assigned for the APC (Autonomous Payload Controller)*?

*Worked with GAS payloads, the IMAX and certain "secondary" PLB payloads (SSBUV).

On the APS's display the center two digits were the relay number the two digits to either side were alpha-numeric. ("A" "E" "L" Etc. What did these codes mean?

Were there other or backup off-nominal functions an APC could perform? There seemed to be a "generic" list of commands imprinted on the controllers that changed throughout the program.

[MDMoery]

I have a quick question that I have had no luck finding an answer to.

I know that in August 2000, STS-106 became the first Shuttle stack to ever roll into VAB High Bay 2.  Were there ever any subsequent Shuttle stacks that took refuge in High Bay 2?  As in SRB/ET/Orbiter stacks on an MLP, not Orbiters on the floor.  Or for that matter, were there ever any SRB and/or ET partial stacks in HB2?

So far as I can find, the only stacks that have ever been in HB2 in the 55 year history of the building are:
* Apollo 10 (full stacking)
* Apollo 13 (Launch vehicle stacking only, CSM/LM spacecraft stacked in HB1)
* Skylab 1 (full stacking of space station)
* STS-106 (Shuttle stacking not possible, refuge only)

Thanks.

[Jim]

Where were the two-digit relay addresses assigned for the APC (Autonomous Payload Controller)*?

*Worked with GAS payloads, the IMAX and certain "secondary" PLB payloads (SSBUV).

On the APS's display the center two digits were the relay number the two digits to either side were alpha-numeric. ("A" "E" "L" Etc. What did these codes mean?

Were there other or backup off-nominal functions an APC could perform? There seemed to be a "generic" list of commands imprinted on the controllers that changed throughout the program.

no off nominal functions.
Flight software and payload bay wiring is where the addresses were assigned

[Kyra's kosmos]

Thank you, Jim.

The APC was used on many missions and deserved a mention.

[Hog]

Good day, I have just been challenged as to my reasoning of exactly why the Shuttle's main engines ignition was staggered by 120 milliseconds

I've always understood that it was to reduce loads throughout the Main Propulsion System(MPS).
or
Was the 120 millisecond staggered ignition to reduce the shockwave leaving the aft section in an effort to reduce the wear/tear on the SSME exhaust tunnel(to keep the fire bricks from flying around)?

or some combination of both or neither?

[Jim]

Good day, I have just been challenged as to my reasoning of exactly why the Shuttle's main engines ignition was staggered by 120 milliseconds

I've always understood that it was to reduce loads throughout the Main Propulsion System(MPS).
or
Was the 120 millisecond staggered ignition to reduce the shockwave leaving the aft section in an effort to reduce the wear/tear on the SSME exhaust tunnel(to keep the fire bricks from flying around)?

or some combination of both or neither?

To keep the nozzles from banging into each other. 

SSME exhaust was nothing like the SRBs and there was no shockwave since the SSMEs took 3 seconds to come up to thrust.

[daschmid]

Obscure and very specific questions about the Flight Software:


I've been slowly reconstructing HAL/S source based on available FSW specifications.   The specifications only go so far.  Obviously I have no info on comment lines and CR history, but I'm also left with questions of style. I know it's a long shot, but if anyone in the world knows the answers to these questions there's a good chance they're hanging around this forum.


Here's a link to a couple of reconstructed functions for reference:


https://gist.github.com/ColanderCombo/3b28cc7c934c801ee5b37db8152a01a6


Questions:
- How close do these reconstructions look to the original code?  I already know that the original was extensively annotated, tying individual lines of code to the Change Request they are associated with.  Excluding this annotation, how verbose were comments?  In these files I have relatively few comments, but maybe text from the source specification should be included?
- HAL/S supports Fortran-style 'C' line comments and the surprisingly modern looking '/* */' inline comment.  Were inline comments common?
- HAL/S flow control statements like IF/THEN/ELSE take a single statement.  The equivalent to C's  '{}' block is a 'DO; END;' block.  I've omitted the DO;/END; in cases where the code looked cleaner without it. Is this reasonable, or were there stricter rules?
- COMPOOL variables: in general, I've been accessing shared COMPOOL variables directly throughout functions.  I've seen some implications in the specs that inputs are copied into local variables at the top of functions so the values will be consistent throughout.  Similarly, outputs might get set in a single batch at the end of the function.  Any insights?
- SM2_OPS makes use of the user interface grammar, which isn't part of the HAL/S language and is implemented using macros.  Does it look right?
- SSP_EXEC plays a little fast and loose with HAL's NAME() feature. (equivalent to a pointer/addressof in other languages). Does this seem legit?


If you're able to help out with these questions or if you have any other notes, thanks much!

[Hog]

Do any of our Shuttle-minded members have any memories of Flight Termination System(FTS) batteries being changed at the pad?

I remember a video showing a man/men pushing a cart with a battery or batteries loaded on it.  The very careful manner in which these people were pushing the cart led me to think that they were very important and/or delicate and had some weight to them..  The commentators were talking about battery temperatures and battery life.

I was watching the video online, so that precludes any of the missions Return To Flight#1 (RTF#1) STS-26 that I was watching live via NASA-Select(now NASA-TV) via C band satellite. Unless it was recorded and then I watched it later, online.

If this indeed was a FTS battery change event, was it common?

[DaveS]

Do any of our Shuttle-minded members have any memories of Flight Termination System(FTS) batteries being changed at the pad?

I remember a video showing a man/men pushing a cart with a battery or batteries loaded on it.  The very careful manner in which these people were pushing the cart led me to think that they were very important and/or delicate and had some weight to them..  The commentators were talking about battery temperatures and battery life.

I was watching the video online, so that precludes any of the missions Return To Flight#1 (RTF#1) STS-26 that I was watching live via NASA-Select(now NASA-TV) via C band satellite. Unless it was recorded and then I watched it later, online.

If this indeed was a FTS battery change event, was it common?

No, what you most likely saw was recorded KSC PAO footage of the HST battery removal and recharge and subsequent re-installation following the first scrub of STS-31. The HST batteries required a 120 hr recharging period following any launch scrubs and they had to it in the VAB Battery Lab which batteries like this are stored in a special refrigerator which chills the batteries which allows them to take on a stronger charge. This was all done in tandem with the APU R&R that caused the launch scrub.

Video can seen here:

[Hog]

Do any of our Shuttle-minded members have any memories of Flight Termination System(FTS) batteries being changed at the pad?

I remember a video showing a man/men pushing a cart with a battery or batteries loaded on it.  The very careful manner in which these people were pushing the cart led me to think that they were very important and/or delicate and had some weight to them..  The commentators were talking about battery temperatures and battery life.

I was watching the video online, so that precludes any of the missions Return To Flight#1 (RTF#1) STS-26 that I was watching live via NASA-Select(now NASA-TV) via C band satellite. Unless it was recorded and then I watched it later, online.

If this indeed was a FTS battery change event, was it common?

No, what you most likely saw was recorded KSC PAO footage of the HST battery removal and recharge and subsequent re-installation following the first scrub of STS-31. The HST batteries required a 120 hr recharging period following any launch scrubs and they had to it in the VAB Battery Lab which batteries like this are stored in a special refrigerator which chills the batteries which allows them to take on a stronger charge. This was all done in tandem with the APU R&R that caused the launch scrub.

Excellent and thank you, that was great to watch another shuttle video.  That was exactly the video I was asking about.
Interesting tidbit:  1:35 Each "set" consists of 6 batteries and each set weighs 400lbs. There were 2 sets of batteries on HST.

[John2375]

In the earlier days, of many Edwards AFB landings- why were some fights landed on the lakebed and others on the concrete runway??
For example: STS-36 landed on lakebed runway 23. Why?? The previous flight landed on concrete runway 22.. 
I understand in the very early days they wanted the extra margin the lakebed runways allowed for, but in the above example it was 1990..

[mkirk]

In the earlier days, of many Edwards AFB landings- why were some fights landed on the lakebed and others on the concrete runway??
For example: STS-36 landed on lakebed runway 23. Why?? The previous flight landed on concrete runway 22.. 
I understand in the very early days they wanted the extra margin the lakebed runways allowed for, but in the above example it was 1990..

The simple answer is the decision came down to which runway had the optimal “anticipated” and “observed” approach and landing conditions.

Which runway had the best winds (direction and magnitude)?
Would the orbiter experience turbulence or shear layers?
Were there cloud decks obscuring the approach path (i.e. maybe clouds to the north or east, but clear to the south or west)?
Is there rain/moisture or lightning from one direction versus another?

What about sun angle and glare:
Is the sun in the crew’s eyes? 
Is it creating shadows that obscure the runway marking or lighting, or making depth perception a challenge?

What about ground fog:
Is it obscuring the view of the approach lighting?

What about runway condition:
Is one end of the runway still covered by puddles from recent rains?
Expected braking action and rollout margins?



I hope that gives you insight into some of the thought process.  Keep in mind, the decision on landing sight had to be made a little over 90 minutes prior to the expected touchown in order to accommodate the deorbit burn.  After the burn, it was possible under certain conditions, but certainly not ideal, to change the runway for a particular landing sight.


Mark Kirkman
“NASA Space Shuttle Hugger”

[DaveS]

Question on the post-MECO ET Sep translation maneuver that was done by the CDR: On the early missions it seems like it wasn't a a +X maneuver but rather a -Y maneuver given the PAO's comments on STS-1 that the orbiter was "moving to north of the External Tank" and that Young should have been "able to see it out of his window". Is this correct and when wasn't it changed to the +X maneuver that was used through the rest of the program?

[mkirk]

Question on the post-MECO ET Sep translation maneuver that was done by the CDR: On the early missions it seems like it wasn't a a +X maneuver but rather a -Y maneuver given the PAO's comments on STS-1 that the orbiter was "moving to north of the External Tank" and that Young should have been "able to see it out of his window". Is this correct and when wasn't it changed to the +X maneuver that was used through the rest of the program?

For STS-1 it was indeed an “out of plane” maneuver.  In the case of STS-1 it was a +Y burn.  The exact direction was determined by the exact roll attitude of the orbiter at ET Sep (which was supposed to be 180 degrees).  As you can see in my attached image, if the roll attitude was less than 170, then they would perform a -Y burn.

The idea was this got the Orbiter safely away from the ET by being out of plane - keep in mind the orbiter did an automatic -Z translation right at ET Sep - this Y translation was in addition to that.  It was also hoped that, depending on burn direction and. exact orbiter roll attitude, either the CDR or PLT would be able to view the tank.

If my memory is correct, this procedure was changed to the standard +X maneuver for STS-2.  My copy of the STS-2 Checklist does not have the Y maneuver in it.  I was just a kid at the time, but if my memory isn’t failing me, I actually recall the news coverage making a big deal about this.  They talked about how the +X translation would allow the ET Umbilical Well Camera to obtain imagery of the condition of the tank from bottom to top as the orbiter moved along the length of the separating tank.


Mark Kirkman
“NASA Space Shuttle Hugger”

[DaveS]

Mark: thanks for the answer. It was something that had been on my mind on and off again for a few years. In my mind up until now was that the "north" that the MCC PAO stated was in relation to the orbiter coordinate system where "north" was +X.

Another DPS question: Did MM104 OMS-1 MNVR EXEC take in account the additional dV of the MPS propellant dump when calculating the dV targets?