-
#120
by
ChrisGebhardt
on 23 Nov, 2007 03:59
-
Zoomer30 - 22/11/2007 9:54 PM
Ok I have a "did they ever consider doing this test "question. I know that they at one point were really thinking about using one of the test flights of the Columbia as a RTLS abort test flight. Bascially fly to SRB sep, then simulate some "issue" and swtich to RTLS abort mode and do it. That was quickly dropped since that abort mode is very risky and was not worth the risk for a somewhat low chance of being needed option (ATO, TAA and AOA are much more likely).
Anyway, did they ever consider using Enterprise to do a ALT type test at the KSC runway? I guess they was not much NEED to do one since no landings where planned their till 83 or so (Solar Max mission was the first I think, even though it had been planned for the flight before).
Did they ever think to do that just to get a feel for a landing at the ultra long but ultral narrow KSC strip??
Seeing as how this question has already been answered, I've got one for you... what makes you think an RTLS abort has a "somewhat low chance of being needed" and that the "ATO, TAA (which is TAL) and AOA are much more likely"? Abort modes are dependent on the type of failure experienced and when a failure occurs. For example, if an SSME were to fail during SRB powered flight, the Shuttle wouldn't have enough energy to make a TAL site and certainly wouldn't have enough energy to execute an AOA or ATO. In fact, the TAL sites don't even become an option until after 2min 30secs of flight. Therefore, the RTLS abort provides protection for failures that occur before this time.
Are you thinking of the statements by some engineers and others in the Shuttle program who have said that the RTLS is the abort option that carries the most risk? Because this is true. But RTLS is an abort mode for a reason and could just as easily be neccessary given a certain failure.
I don't mean this as an attack, as re-reading the first part it I realize it certainly could come across as such. I'm just curious why you used that phrasing.
-
#121
by
Hoonte
on 23 Nov, 2007 10:31
-
-
#122
by
brahmanknight
on 23 Nov, 2007 10:42
-
Those are the Tail Service Masts. They provide electrical and fuel/oxydizer connections for the shuttle. The External Tank is fueled through those masts via the shuttle.
-
#123
by
MKremer
on 23 Nov, 2007 13:19
-
Also, they provide no structural support to the Shuttle stack. They're only there to handle Shuttle stack/pad umbilical connections (fluid/gasses/electrical) until T-0 and then withdraw and protect them from the engine/motor exhausts and heating.
-
#124
by
Zoomer30
on 25 Nov, 2007 02:54
-
The RTLS would be needed in only a few very specific situations. I think if an engine failed during the first 2 mins they would not have enough thrust to pull off an RTLS at that point, I think it would end up being a ditching abort. An engine failure very late in the SRB burn would probably be the only time I can see. Its a very low probability of being needed in my mind, since so many things need to happen just right to be able to get back. I think its only about the first 3mins or so one can be attempted. Something happens after that and your in TAL or ATO area. AOA is also very small, would be needed if they make orbit but lose cabin pressure or something like that.
I just remember reading that about the RTLS once and how they figured it was not worth the risk for something that would more than likely never be needed.
-
#125
by
Jorge
on 25 Nov, 2007 03:58
-
Zoomer30 - 24/11/2007 9:54 PM
The RTLS would be needed in only a few very specific situations. I think if an engine failed during the first 2 mins they would not have enough thrust to pull off an RTLS at that point, I think it would end up being a ditching abort.
No, that is incorrect. An RTLS is possible, and would be used, for an engine failure any time between SRB ignition and Negative Return. Of course, even if the engine fails right after liftoff the RTLS itself cannot be initiated until after SRB SEP (T+2:30, specifically).
In practice, an RTLS would not be used for an engine failure after the first TAL boundary. However, in the event of a systems failure that requires earliest possible landing, such as a cabin leak or loss of both Freon loops, a 3-engine RTLS may be performed up to Negative Return.
An engine failure very late in the SRB burn would probably be the only time I can see. Its a very low probability of being needed in my mind, since so many things need to happen just right to be able to get back. I think its only about the first 3mins or so one can be attempted.
Also incorrect. Negative Return is usually after T+3:40.
-
#126
by
rdale
on 25 Nov, 2007 04:53
-
For more specific info on abort modes - read the back of EVERY shuttle press kit release.
-
#127
by
dbhyslop
on 25 Nov, 2007 04:54
-
Jorge - 24/11/2007 11:58 PM
In practice, an RTLS would not be used for an engine failure after the first TAL boundary. However, in the event of a systems failure that requires earliest possible landing, such as a cabin leak or loss of both Freon loops, a 3-engine RTLS may be performed up to Negative Return.
It is interesting to learn this. I recall reading in another thread that RTLS is considered risky, particularly separating from an ET that may have sloshing propellants. Would they really choose the RTLS abort mode over the TAL in the event of a cabin leak, given the fact that the crew are in pressure suits? I assume these risks have already been quantified to determine the abort criteria in the flight rules, etc?
-
#128
by
Jorge
on 25 Nov, 2007 05:44
-
dbhyslop - 24/11/2007 11:54 PM
Jorge - 24/11/2007 11:58 PM
In practice, an RTLS would not be used for an engine failure after the first TAL boundary. However, in the event of a systems failure that requires earliest possible landing, such as a cabin leak or loss of both Freon loops, a 3-engine RTLS may be performed up to Negative Return.
It is interesting to learn this. I recall reading in another thread that RTLS is considered risky, particularly separating from an ET that may have sloshing propellants. Would they really choose the RTLS abort mode over the TAL in the event of a cabin leak, given the fact that the crew are in pressure suits?
RTLS is risky, but it is a certified Intact Abort mode. It will be performed if less risky than the alternatives.
Remember, even though the crew is in pressure suits, much of the shuttle's avionics are air-cooled and will not last long in a vacuum. And the shuttle is a fly-by-wire vehicle, so the avionics are absolutely required to safely land the vehicle.
I assume these risks have already been quantified to determine the abort criteria in the flight rules, etc?
Yes. The rules require RTLS to be performed for:
1) Impending loss of all APU/hydraulic capability
2) Failure of a forward windshield or side hatch thermal (outer) window pane
3) Cabin leak with dP/dt > 0.15 psia/min
4) Impending loss of all O2 or H2 cryo
5) Loss of two Freon loops
6) Loss of any two main DC electrical buses (due to loss of ET door closure capability)
-
#129
by
Zoomer30
on 25 Nov, 2007 07:07
-
Well yes I said 3 mins or so, I did not know right when neg return was called. 3:40 is close.
-
#130
by
spaceshuttle
on 26 Nov, 2007 04:38
-
External Tank No. 1 was never flown. Does anyone know what it was used for?
-
#131
by
thomasafb
on 26 Nov, 2007 08:19
-
spaceshuttle - 25/11/2007 11:38 PM
External Tank No. 1 was never flown. Does anyone know what it was used for?
According to Jenkins, Serial Number 1 was assigned to the MPTA-ET. It was used at the NSTL (Stennis) during the testing of the SSMEs in a realistic environment. It is currently used for the Pathfinder Orbiter on display at MSFC.
-
#132
by
MB123
on 26 Nov, 2007 09:12
-
Loss of power on both DC buses, thats an interesting one. I thought that astronauts were trained, and have been since STS-1, to perform a spacewalk to close ET doors in this event. Does anyone have any dot-points as to why the spacewalk is (apparently) a less attractive option than the RTLS abort in this case?
mb
-
#133
by
MB123
on 26 Nov, 2007 09:15
-
Yes. The rules require RTLS to be performed for:
1) Impending loss of all APU/hydraulic capability
2) Failure of a forward windshield or side hatch thermal (outer) window pane
3) Cabin leak with dP/dt > 0.15 psia/min
4) Impending loss of all O2 or H2 cryo
5) Loss of two Freon loops
6) Loss of any two main DC electrical buses (due to loss of ET door closure capability)
-
#134
by
mkirk
on 26 Nov, 2007 13:40
-
MB123 - 26/11/2007 4:12 AM
Loss of power on both DC buses, thats an interesting one. I thought that astronauts were trained, and have been since STS-1, to perform a spacewalk to close ET doors in this event. Does anyone have any dot-points as to why the spacewalk is (apparently) a less attractive option than the RTLS abort in this case?
mb
Well yes the crew is trained on ET Umbilical Door closure, but going into orbit, which now requires a much more thermally severe re-entry compared to an RTLS, is less desireable. First there is no assurance that the EVA will be successful, the loss of 2 main busses makes on-orbit operations far more difficult, and now you are only one main bus failure away from a loss of all electrical power – in which case you are really screwed.
So given those issues and the desire for the most thermally benign entry possible, the best option is to abort RTLS. If RTLS is not an option (i.e. past Negative Return) then pressing on uphill to attempt to resolve the door issue would be preferred over a TAL (and now on station missions crew rescue and CSCS are an option).
Mark Kirkman
-
#135
by
Jorge
on 26 Nov, 2007 14:03
-
MB123 - 26/11/2007 4:12 AM
Loss of power on both DC buses, thats an interesting one.
mb
Not "both" - I said "any two" buses. There are three.
-
#136
by
spaceshuttle
on 28 Nov, 2007 04:09
-
I've slacked off on the coverage of both STS-120 and next week's STS-122. I'm asking this for modeling purposes--would either of these missions be considered a "milestone/historic mission in Shuttle history" by anyone here?
-
#137
by
rdale
on 28 Nov, 2007 04:21
-
Only at a press conference, when some reporter asks "is this the most complex mission to date" and the answer is completely up to the asker. If you think adding a European module is historic, then 122 is a biggie. If you think that fixing a solar array is a milestone, then 120 is too...
-
#138
by
spaceshuttle
on 28 Nov, 2007 05:19
-
rdale - 27/11/2007 11:21 PM
Only at a press conference, when some reporter asks "is this the most complex mission to date" and the answer is completely up to the asker. If you think adding a European module is historic, then 122 is a biggie. If you think that fixing a solar array is a milestone, then 120 is too...
That rules those two out for me! :cool: Thanks!
-
#139
by
Susan27
on 28 Nov, 2007 13:30
-
Hi,
I am completely new to this page, so I hope this is the correct place to ask... [Sorry for my bad english, I only had basic-school english in German school...
]
In a lot of shuttle-related essays concerning the vessel`s Flightdeck there are desriptions for the shuttle window-system like...
"Startracker: Its two units are located just forward and to the left of the commander's plus X window" and so...
Do you know if there is (online) a graphic/picture availabe where all shuttle flight-deck windows are showed (perhapes together with the main consoles)...?
Thanks very much in advance!
Kind regards
Susan
]