Question General Spaceflight Q&A

DaveS

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This being the case, what functions are GPS-critical and which can be completed by the crew? I'm sure the lists are extensive, I'm just curious about the major items.
It's GPC which is short for General Purpose Computer. THe orbiter have five identical GPCs, 4 running an redundant software called the Primary Avionics Software System(PASS) while the 5th is running a software called the Back-up Flight Software(BFS).

On a regular basis the GPCs vote among themselves and then run it by the BFS when the BFS GPC is running. If any GPC shows discrepancies during the voting, it is automatically declared faulty and a light on the GPC Matrix on panel O1 is illuminated to indicate which GPC has been declared faulty.

This gives MCC and the crew a chance to review the GPC problem and take the appropriate action such as shutting it down.

Edit: To add, the GPCs control everything on the orbiter. If you lose them all, including the final resort, the BFS, that's it, you're not coming home, especially if they die on-orbit as the only way to fire the OMS engines is by the PASS/BFS. There's no other way. Complete GPC-loss means loss of crew, especially during dynamic phases such as ascent and entry. Even bail-out is not an option as bail-out require the orbiter to be in controlled gliding flight which can only be done if the GPCs are working,
 
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Urwumpe

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This being the case, what functions are GPS-critical and which can be completed by the crew? I'm sure the lists are extensive, I'm just curious about the major items.

Simple: almost none can be done without the GPCs. The GPCs poll nearly all switch positions and hand controllers in the flight deck, you can only control the power distribution over the circuit breakers directly.

What you can still control without GPCs are the communication gear, only the "Downlist" of GPC parameters would be missing.
 
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Izack

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I have to say...there are too many freaking acronyms. :lol:
This thread is still very helpful, though. I always end up looking those acronyms up, and learning a lot more about the Shuttle systems than I would have otherwise.
 

Lunar_Lander

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In the S3 Simulator I was supposed to switch on a "Microwave Beam Landing System" or something similar to that, but I gurantee that it contained the word Microwave. Is that some kind of ground based transmitter that guides the Shuttle in?

In S3, the Orbiter was heading away from the Runway until I switched on that Microwave system, after which it rotated around towards the runway.
 

Urwumpe

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In the S3 Simulator I was supposed to switch on a "Microwave Beam Landing System" or something similar to that, but I gurantee that it contained the word Microwave. Is that some kind of ground based transmitter that guides the Shuttle in?

Yes, it is a modernized version of the ILS. Not more, not less. More accurate and transmit more extra data.

But the Shuttle doesn't automatically fly to the runway with it.

The navigation aids are explained good here: http://www.nasa.gov/centers/johnson/pdf/383450main_navigation_aids_workbook 21002.pdf

In S3, the Orbiter was heading away from the Runway until I switched on that Microwave system, after which it rotated around towards the runway.

That is because S3 and its successor are only switch simulations, not Shuttle simulations. until you throw the right switches, nothing happens.
 
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ar81

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1.How should shuttle attitude system figures be understood? What do they mean?
2.What is the proper attitude for what purpose while in orbit?
3.Is OMS-2 an orbit circularization burn, or merely a course correction burn?
4.For how long do they take pictures of ET before doing something else?
5.How do they bump ISS orbit up?
6.How much air is lost when using airlock for EVA.
7.Where are the NASA manuals to operate and understand space shuttle operation in detail?
 

garyw

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I'll leave the attitude questions to DaveS :lol:

3.Is OMS-2 an orbit circularization burn, or merely a course correction burn?

It's a circulisation burn. Remember that at MECO the shuttle is sub-orbital so the OMS-2 raises the orbit so that the shuttle can avoid the same fate as the ET.

4.For how long do they take pictures of ET before doing something else?

Depends on the lighting conditions. A launch into night means they don't take any - The umbilical well camera has a flash so takes photos but the crew doesn't. On a launch like 131 the lightning conditions meant that they could follow the tank for longer.

5.How do they bump ISS orbit up?

Depends on propellant margins and goals. For example, some times the orbit is raised to provide better launch opportunities for shuttle as changing the orbit also changes the plane alignment times.
This is interesting but doesn't give you the whole story.

6.How much air is lost when using airlock for EVA.

Next to none. If there was any air there would be pressure, if there was pressure releasing the airlock handle would cause the airlock to open with some force potentially causing damage. This happened on an EVA from Mir once.

7.Where are the NASA manuals to operate and understand space shuttle operation in detail?

http://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html
 

Urwumpe

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1.How should shuttle attitude system figures be understood? What do they mean?

Simply the parameters for the Universal pointing algorithm. Essentially, you describe your attitude as rotation in reference of a reference axis. eg, you point your vessel Y axis at the ISS and rotate 40° around it.

So, when you read for example in the flight plan: -ZLV -XVV, it means that the Z axis (up, in body coordinates of the STS) points in opposite direction of the local vertical (LV), while the X axis points against the direction of the velocity vector (VV), which means you are flying retrograde.

"-ZLV -XVV" thus means "Fly heads down, retrograde"

2.What is the proper attitude for what purpose while in orbit?

There are many purposes and attitudes for these...be more specific.

3.Is OMS-2 an orbit circularization burn, or merely a course correction burn?

Only Circularization. OMS-1 is a course correction burn, if executed.

4.For how long do they take pictures of ET before doing something else?

Not very long, the Mission Specialists who do this task also have nothing better to do before the Post-Insertion checklist starts 50 minutes after launch. The astronauts don't leave their seats for it, and the attitude is only kept at the ET until the major mode change to GNC OPS 105, about 8 minutes after the beginning of the photo ops.

5.How do they bump ISS orbit up?

By using the downward pointing PRCS thrusters in pulses, while the ISS controls the attitude. There is a special software mode that controls the minute long maneuver.

6.How much air is lost when using airlock for EVA.

Almost none. Until reaching about 0.1 bar, the air is pumped into tanks, and the final atmosphere is vented overboard through non-propulsive vent valves.
 

STS

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Hello, guys, I have a question related to the Landing:

What do the astronauts and mission control say in this video (and in every landing):

[nomedia="http://www.youtube.com/watch?v=7rfmb3uuLE8&feature=player_embedded"]YouTube- STS-129 HD Landing[/nomedia]

at minute 3:58 and 4:39 ?

Thanks
 
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garyw

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3:58 - Slightly low at the 180 - that means that Atlantis was slightly lower than the ideal glide path at the 180 degree marker on the HAC. This was expected for that approach.

4:39 - slightly low at the 90 - Same as above but at the 90 degree marker.

When the shuttle comes in for landing it flies a partial circle called the HAC.

You can see it pictorially here:

407231main_sts129_ksc172_close.gif
 

Donamy

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The 180 would be like the downwind leg, in airport terms and the 90 would be like the base leg, except it is flown in a circle instead of a standard runway pattern.
 

clickypens

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Not exactly a question for the space shuttle in and of itself, but why didn't NASA ever use Donatello? I've read that it was more advanced than the other MPLMs (more racks, better shielding, etc). I've also seen that they took components from Donatello to put them on PMM Leonardo. Wouldn't it have been easier to just use Donatello as the PMM?
 

Orbinaut Pete

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Not exactly a question for the space shuttle in and of itself, but why didn't NASA ever use Donatello? I've read that it was more advanced than the other MPLMs (more racks, better shielding, etc). I've also seen that they took components from Donatello to put them on PMM Leonardo. Wouldn't it have been easier to just use Donatello as the PMM?

Basically, they never used it because it was never needed. They won’t use it for the PMM, because it would cost too much money & take too much time to bring it up to flight readiness level.
 

ar81

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1.Do you think Nintendo's Space Shuttle was educational?
[nomedia="http://www.youtube.com/watch?v=-DciaWNsLTg"]YouTube- 1991 Space Shuttle Project - Nintendo[/nomedia]

2.Do you think Atari 2600 Space Shutle was educational?
[nomedia="http://www.youtube.com/watch?v=M92fmU7n3cU"]YouTube- Atari XL/XE - Space Shuttle : A Journey Into Space [Activision] 1983[/nomedia]

3.How does s-turn/Atmospheric Entry trajectory looks on the world map?
 

garyw

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How much time off does a shuttle crew get at the end of a mission? I assume they get a couple of days to relax and spend time with family but how long until they are back "in the office"?

what about long duration ISS crews?
 

ar81

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1.Before ET SEP, you see some plasma "flames" surrounding the vessel. What causes it?
2.Is "re-entry" a term used by NASA manuals? The strange thing is that you can se it in some NASA videos like this one.
3.During entry you see plasma flames. Is it caused by compressed air that heats, friction or any other? How much contribution each factor has in the heating?
4.What event defines the beginning and end of EI and TAEM?
 

clickypens

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number one I'm pretty sure is caused by RCS thrusters. I'll let more experienced people get the others.

Going back to my question, is there anywhere I could find more detail about the MPLMs? I don't seem to understand why they couldn't flight-ready it if the other two were made ready and flown. It just seems a little weird to me that Leonardo was flown three times in a row and Donatello never.
 

garyw

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Donatello wil not be flown due to the cost of making it flight worthy. With three shuttle missions left and even IF an extension is granted there is no logical rationale behind spending the money to make the Donatello MPLM a flight article.
 
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