Author Topic: Shuttle Questions Q and A (2)  (Read 195284 times)

Online DaveS

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RE: Shuttle Questions Q and A (2)
« Reply #80 on: 05/05/2006 08:35 pm »
No. The orbiter uses cryogenic propellants(LH2 and LOX) to power to the three fuel cells and once those die the loses it capability to power it's systems like critical heaters for the OMS and RCS.

The shuttle was never intended as a long duration spacecraft like the Soyuz and Progress spacecrafts.
"For Sardines, space is no problem!"
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"We're rolling in the wrong direction but for the right reasons"
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Offline PlanetStorm

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RE: Shuttle Questions Q and A (2)
« Reply #81 on: 05/05/2006 08:49 pm »
Quote
Flightstar - 5/5/2006  3:31 PM
Orbiters can't survive in space for too long. Even if you took away the power requirements, they'd get very ill very fast with the whole enviorment of space.

Sick orbiter? Would that be the structure/electronics degrading in a radiation environment, or something else?

Offline PlanetStorm

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RE: Shuttle Questions Q and A (2)
« Reply #82 on: 05/05/2006 08:50 pm »
Quote
DaveS - 5/5/2006  3:35 PM

No. The orbiter uses cryogenic propellants(LH2 and LOX) to power to the three fuel cells and once those die the loses it capability to power it's systems like critical heaters for the OMS and RCS.

The shuttle was never intended as a long duration spacecraft like the Soyuz and Progress spacecrafts.

Not possible to redirect ISS power to the orbiter?

Online DaveS

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RE: Shuttle Questions Q and A (2)
« Reply #83 on: 05/05/2006 09:02 pm »
The orbiter would dead when you undocked it!

Edit:
Cryogenic fluids boils off so the supplies of LH2 and LOX will decrease even if you power everything off. The orbiter's were simply not designed with a long on-orbit lifetime in mind.
"For Sardines, space is no problem!"
-1996 Astronaut class slogan

"We're rolling in the wrong direction but for the right reasons"
-USA engineer about the rollback of Discovery prior to the STS-114 Return To Flight mission

Offline shuttlefan

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RE: Shuttle Questions Q and A (2)
« Reply #84 on: 05/08/2006 01:53 pm »
What were the black paint schemes on the nose cones of the solid Rocket Boosters that I could plainly see on TV and in pictures--seems as though they were there from about 1984-1993, now the nose cones are totally white except for the black ring around the left booster just below the nose cone. ;)

Offline norm103

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RE: Shuttle Questions Q and A (2)
« Reply #85 on: 05/08/2006 01:58 pm »
they were for tarcking camras

Offline Jamie Young

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RE: Shuttle Questions Q and A (2)
« Reply #86 on: 05/10/2006 11:08 pm »
Quote
DaveS - 5/5/2006  4:02 PM

The orbiter would dead when you undocked it!

Edit:
Cryogenic fluids boils off so the supplies of LH2 and LOX will decrease even if you power everything off. The orbiter's were simply not designed with a long on-orbit lifetime in mind.

Could they replace them with electrical power units?

Offline Jim

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RE: Shuttle Questions Q and A (2)
« Reply #87 on: 05/11/2006 12:52 am »

Quote
Jamie Young - 10/5/2006 7:08 PM
Quote
DaveS - 5/5/2006 4:02 PM The orbiter would dead when you undocked it! Edit: Cryogenic fluids boils off so the supplies of LH2 and LOX will decrease even if you power everything off. The orbiter's were simply not designed with a long on-orbit lifetime in mind.
Could they replace them with electrical power units?

 

What are electrical power units?

 

also who would fly it home?  who would be trained to fly it.  Who on the ground would maintain proficency in shuttle systems?  How long does it take to power it up.  how would the atmosphere be maintained while dormant. 


Offline dmc6960

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Re: Shuttle Questions Q and A (2)
« Reply #88 on: 05/11/2006 07:17 pm »
Are the hypergolic propellents loaded in OPF, or at the pad?
-Jim

Online DaveS

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Re: Shuttle Questions Q and A (2)
« Reply #89 on: 05/11/2006 07:18 pm »
They're loaded at the pad.
"For Sardines, space is no problem!"
-1996 Astronaut class slogan

"We're rolling in the wrong direction but for the right reasons"
-USA engineer about the rollback of Discovery prior to the STS-114 Return To Flight mission

Offline psloss

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RE: Shuttle Questions Q and A (2)
« Reply #90 on: 05/12/2006 10:33 pm »
Quote
psloss - 12/5/2006  2:00 PM

Quote
Avron - 5/11/2005  5:31 PM

Thanks... so what they basically took the remaining engines out of Auto shutdown mode, that in itself sounds a little dangerous..."position inhibits all automatic shutdowns". That brings up another question, what then would shut down the engines, time... cannot be velocity, lack of gass, but that would be very bad?
This would be a good question for the Q & A thread -- particularly that switch...
This question -- about the main engine limits switch -- comes out of the 51-F thread in the video section; here's the shuttle reference again, as a reference:
http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/prop/maldet.html

Quote
Although a shutdown as a result of violating operating limits is normally automatic, the flight crew can, if necessary, inhibit an automatic shutdown through the use of the main engine limit shut dn switch on panel C3. The switch has three positions: enable, auto and inhibit. The enable position allows only the first engine that violates operating limits to be shut down automatically. If either of the two remaining engines subsequently violates operating limits, it would be inhibited from automatically shutting down. The inhibit position inhibits all automatic shutdowns.
My question is regarding the first call on this after the center engine shutdown, although any explanation of this ascent from the experts would be greatly appreciated.  After the center engine shutdown, the crew was told to take the switch to Enable -- this was just after the single engine TAL call.  Later on, when one of the two "fuel turbine temp" sensors on the right engine failed (reported in a similar pattern to that of the center engine), the crew was called to take the switch to Inhibit.

Given the description from the reference manual and the situation where you already have one engine out, can someone clarify the difference between Enable and Inhibit?  (Or perhaps this logic has changed since 51-F?)

Also, was the call to take the switch to Enable a function of the failure?

Thanks,

Philip Sloss

Offline mainengine

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RE: Shuttle Questions Q and A (2)
« Reply #91 on: 05/12/2006 11:33 pm »
Sometimes NASA reports mention the different versions of the engines especially when they were Block I or Block II engines or the former Block IIa. For future and most of the latest flights Block II engines were flown. Therefore this is no longer mentioned in those reports since only Block II engines are used since STS-110 of Atlantis in 2002.
If you like to read a summary of all former and actual flight engines look at http://www.mainengine.gratis-webspace.de/ssme_engines.html

Offline mkirk

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RE: Shuttle Questions Q and A (2)
« Reply #92 on: 05/12/2006 11:51 pm »
Quote
psloss - 12/5/2006  5:20 PM

My question is regarding the first call on this after the center engine shutdown, although any explanation of this ascent from the experts would be greatly appreciated.  After the center engine shutdown, the crew was told to take the switch to Enable -- this was just after the single engine TAL call.  Later on, when one of the two "fuel turbine temp" sensors on the right engine failed (reported in a similar pattern to that of the center engine), the crew was called to take the switch to Inhibit.

Given the description from the reference manual and the situation where you already have one engine out, can someone clarify the difference between Enable and Inhibit?  (Or perhaps this logic has changed since 51-F?)

Also, was the call to take the switch to Enable a function of the failure?

Thanks,

Philip Sloss


The Main Engine Limit Shutdown Switch and its operation is relatively complex so I will just hit some of the main points without getting into the nuances of various failure engine failure modes.

There are 5 space shuttle main engine parameters (used to be 6 prior to the block II engines) that are designated as “critical” to engine operation.  These “redline limits” are all monitored by the main engine controller mounted directly on the engine.  Exceeding one of these limits COULD result in uncontained or catastrophic failure.

If one of the limits is exceeded that engine’s controller will want to shut the engine down.  Depending on where in the trajectory the shuttle is, and depending on what abort boundary has been reached at the time of the problem, shutting down the engine may not be a good idea.  Dealing with this dilemma is the function of the Main Engine Limit Shutdown Switch.

The switch has three positions:

Enable   –   Enables the controller to shutdown the SSMEs
Inhibit   –   Inhibits the controller from shutting down any SSMEs
Auto   –   Enables the controllers to shutdown one SSME that exceed a redline limit.  Limits are then inhibited on the remaining SSMEs. The Auto position can be reset to allow another shutdown by moving the switch to Enable, then back to Auto.  This action is called “limits enable / auto” or “re-enabling limits”.

The philosophy of when to re-enable the limit shutdown software attempts to balance the risk of an engine failing catastrophically while the limits are inhibited against the risk associated with a two engine out contingency abort.

In most cases management of the switch will be coordinated by mission control since they have more insight into the health of the engines.

For 51-F when the first engine exceeded it’s redline parameter and based on the limit switch being in Auto (always in Auto at launch), the engine controller shut the engine down and the orbiter’s general purpose computers automatically inhibited the limit software for the remaining to engines.  Once an engine fails the crew is trained to expect to re-enable the limit software as soon as possible (i.e. abort capability).  This is usually called up to the crew by mission control.  Since the first engine failure was actually do to a sensor problem and not a real engine problem, and since the other engines were also in danger of being erroneously shutdown by faulty sensors, and since the shuttle was at an appropriate abort boundary; mission control called up to the crew “Main Engine Limits Inhibit”.  This was done to prevent any additional engine shutdowns for bad sensors...if MCC or the crew had noticed a real problem with the engine a manual shutdown still could have been performed.  

Mark Kirkman
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Offline psloss

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RE: Shuttle Questions Q and A (2)
« Reply #93 on: 05/13/2006 12:10 am »
Quote
mkirk - 12/5/2006  7:38 PM

For 51-F when the first engine exceeded it’s redline parameter and based on the limit switch being in Auto (always in Auto at launch), the engine controller shut the engine down and the orbiter’s general purpose computers automatically inhibited the limit software for the remaining to engines.  Once an engine fails the crew is trained to expect to re-enable the limit software as soon as possible (i.e. abort capability).  This is usually called up to the crew by mission control.
Thanks as always, Mark.

So, just to be clear, the call that CapCom Dick Richards made just after the single engine TAL boundary call "...and main engine limits to enable, Gordo" was the call to re-enable the limits, right?

Philip Sloss

Offline mkirk

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RE: Shuttle Questions Q and A (2)
« Reply #94 on: 05/13/2006 12:28 am »
Quote
psloss - 12/5/2006  6:57 PM

Quote
mkirk - 12/5/2006  7:38 PM

For 51-F when the first engine exceeded it’s redline parameter and based on the limit switch being in Auto (always in Auto at launch), the engine controller shut the engine down and the orbiter’s general purpose computers automatically inhibited the limit software for the remaining to engines.  Once an engine fails the crew is trained to expect to re-enable the limit software as soon as possible (i.e. abort capability).  This is usually called up to the crew by mission control.
Thanks as always, Mark.

So, just to be clear, the call that CapCom Dick Richards made just after the single engine TAL boundary call "...and main engine limits to enable, Gordo" was the call to re-enable the limits, right?

Philip Sloss

I am on a wireless net so I really can't download the 51-F file until I have a better coverage area early tomorrow.  When I anwered your question I went by what you said about the later call to inhibit.  So let me double check what was said and when.

What should have happend after the first failure was a call to re-enable...The crew would have cycled the switch to Enable then back to Auto to regain shutdown protection for the remaining engines.  As the Booster Console in the MCC (mission control center) evaluated the engine failure they would have tried to protect the remaining engines from an erroneous shutdown.  To do this they would have made a call to "Inhibit" once the orbiter achieved an appropriate abort capability.

Mark Kirkman
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Offline mkirk

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RE: Shuttle Questions Q and A (2)
« Reply #95 on: 05/13/2006 05:46 pm »
Quote
psloss - 12/5/2006  6:57 PM

So, just to be clear, the call that CapCom Dick Richards made just after the single engine TAL boundary call "...and main engine limits to enable, Gordo" was the call to re-enable the limits, right?

Philip Sloss

I finally downloaded and listened to the audio…I have never bothered to listen to it before.  When I get I chance I will have to get a copy of the whole flight loop and booster loops.

Let me answer your question about the switch.

When the center engine shut down the limits on the remaining two engines were automatically inhibited by the GPCs.  You want that to happen because the Orbiter has not yet achieved Single Engine Abort capability and shutting down another engine would have been bad.  After passing the “Single Engine TAL” boundary Houston called the crew to “Main Engine Limits to Enable Gordo (Gordon Fulerton)”.  This meant if another engine exceeded it redlines it would automatically shutdown leaving the orbiter with one engine to perform a TAL abort.  

As “Booster” continued to evaluate the center engine shutdown, she determined it occurred do to a bad sensor for the “Fuel Turbine Temperature”.  She also saw that one of the two remaining engines had a similar sensor problem.  Because of this she advised Flight to “Inhibit” the limits so the remaining engines would not be shut down by the bad sensors and she would keep an eye on the actual “temperatures”.  If at this point either of the other two engines truly exceeded a “Redline Limit”, then she would have advised “Flight” to have the crew manually shut the engine down.

Mark Kirkman
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Offline mkirk

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RE: Shuttle Questions Q and A (2)
« Reply #96 on: 05/13/2006 05:47 pm »
What is an ATO?

An ATO (abort to orbit) is initiated when ascent performance is not sufficient to achieve orbital velocity without performing an OMS DUMP.  This was the case on 51-F when the center engine shut down do to faulty temperature sensor readings.

The crew was told to “Abort ATO”; at that time Gordon Fullerton turned the abort knob on the front instrument panel to ATO and pushed the abort button.  When the abort is initiated, the OMS (orbital maneuvering system) engines immediately fired to “Dump” propellant.  This is done to reduce the orbiters weight which helps the performance of the remaining main engines and it also provides a small amount of thrust which also helps performance.

The objective of the ATO is to dump just enough of the OMS propellant to ensure MECO (main engine cutoff) for the two remaining engines occurs at “Design Underspeed”.

“Design Underspeed” is defined as the minimal orbit capability (in terms of altitude and velocity) which ensures the orbiter is safe and the External Tank will not land on critical land masses when it re-enters the atmosphere.


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Offline psloss

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RE: Shuttle Questions Q and A (2)
« Reply #97 on: 05/13/2006 06:02 pm »
Thanks, Mark.

Also going to pass along some time references for the thread; this is an excerpt from the mission report:
http://members.aol.com/WSNTWOYOU/STS19MR.HTM

Quote
At 5 minutes 43 seconds after lift-off, both temperature readings for the SSME (Space Shuttle Main Engine) 1 high pressure turbopump indicated above the redline, resulting in a premature shutdown of SSME 1 and the declaration of an ATO (abort-to-orbit) condition. This is the first such abort condition encountered during the Shuttle Program. An OMS (orbital maneuvering system) burn was initiated at 210:21:06:06.0 G.m.t., for 106 seconds and used approximately 4134 lb of propellant. At 8 minutes 13 seconds into the flight, one of two temperature sensors on SSME 3 indicated a high temperature reading and auto shutdown for the remaining two engines was inhibited to assure achieving an acceptable orbit. The OMS (orbital maneuvering system)-2 burn placed the Shuttle in a 143.1- by 108.0-nmi. orbit with an inclination of 49.57 degrees.
One thing I didn't see in the mission report was when the first sensor reading went over its redline on the center engine, which was earlier in the ascent (if I recall correctly, somewhere around plus 3 and 1/2 minutes)...

Whoops, the other thing that I was looking for was how much of an underspeed they ended up with at MECO...

Philip Sloss

Offline mkirk

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RE: Shuttle Questions Q and A (2)
« Reply #98 on: 05/13/2006 06:13 pm »
Quote
psloss - 13/5/2006  12:49 PM

One thing I didn't see in the mission report was when the first sensor reading went over its redline on the center engine, which was earlier in the ascent (if I recall correctly, somewhere around plus 3 and 1/2 minutes)...

Whoops, the other thing that I was looking for was how much of an underspeed they ended up with at MECO...

Philip Sloss

I'll have to look that up and also listen to the entire tapes.

FIDO should have called out the underspeed value right around MECO but it is not on this recording.

Also here is a link to main engine stuff.  It is slighly dated but far more current than the STS News Reference.  Page 26 and 27 discuss the engine limit switch.  It also discusses the 6 parameter the controller tracks for redline shutdowns.  The new Block II engines only use 5 of them.

http://www.shuttlepresskit.com/scom/216.pdf

Mark Kirkman
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Offline psloss

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RE: Shuttle Questions Q and A (2)
« Reply #99 on: 05/13/2006 06:32 pm »
Quote
mkirk - 13/5/2006  2:00 PM

Also here is a link to main engine stuff.  It is slighly dated but far more current than the STS News Reference.  Page 26 and 27 discuss the engine limit switch.  It also discusses the 6 parameter the controller tracks for redline shutdowns.  The new Block II engines only use 5 of them.

http://www.shuttlepresskit.com/scom/216.pdf

Mark Kirkman
Thanks, Mark -- I probably have a copy of that somewhere, but obviously I need to re-read it.

Philip Sloss

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