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#1900
by
Lee Jay
on 12 May, 2009 12:56
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There's an ET-breakup "video" (looks like 16mm film, perhaps) on L2. How did they get that footage when the ET is normally so far from the orbiter at breakup?
I'd bet it was shot from below, not above. Without seeing the video, can't say for sure.
It's about 17 minutes into the ASRM video on L2.
Definitely from below. The orbiter's cameras simply cannot track that smoothly.
That makes a lot of sense. I should have thought of the "from below" option, but it just never occurred. Thanks Jorge!
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#1901
by
Lee Jay
on 12 May, 2009 14:33
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
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#1902
by
Jim
on 12 May, 2009 14:39
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
APM does not equate to leftover propellant
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#1903
by
Lee Jay
on 12 May, 2009 16:51
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
APM does not equate to leftover propellant
Huh. I thought APM was roughly equivalent to leftover *usable* propellant because that unused prop ended up as payload the LV carried to orbit. No?
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#1904
by
Jim
on 12 May, 2009 17:29
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
APM does not equate to leftover propellant
Huh. I thought APM was roughly equivalent to leftover *usable* propellant because that unused prop ended up as payload the LV carried to orbit. No?
There is leftover propellant, but it is not one for one with APM.
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#1905
by
Lee Jay
on 12 May, 2009 17:48
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
APM does not equate to leftover propellant
Huh. I thought APM was roughly equivalent to leftover *usable* propellant because that unused prop ended up as payload the LV carried to orbit. No?
There is leftover propellant, but it is not one for one with APM.
Okay, yes, this part I knew and it's why I used a lot of terms like "ish" and "around".
What I was getting at was that it is a very short time (potentially a second or less) between a nominal MECO and an ECO shutdown. Is that correct?
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#1906
by
Jim
on 12 May, 2009 19:32
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What I was getting at was that it is a very short time (potentially a second or less) between a nominal MECO and an ECO shutdown. Is that correct?
There is more propellant than that left over if there is a "nominal" MECO. The APM is in addition to the 3 sigma margins needed to assure a nominal MECO.
In terms of structural safety factors/margins:
A 1.25 safety factor is like the 3 sigma performance reserves. It is the "minimum" allowed to fly a successful mission.
APM is like safety margins in structural safety factors. If 1.25 SF is required and you have 1.35 SF, your margin is a positive .10. This is similar to the 1500 pounds of APM
For the shuttle, I don't know what the 3 sigma reserves equate to in lift performance.
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#1907
by
Danny Dot
on 13 May, 2009 03:51
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I seem to remember reading, some years back, that there was discussion of eliminating RTLS and replacing it with an abort mode that had the shuttle landing at an east coast airport or military airfield. I believe that John Young was involved in this study.
1. Which fields were in consideration for this mode?
2. What would have been the difficulties involved?
3. Why wasn't it ultimately adopted?
This seems like a no brainer as it eliminates the element of RTLS that made everyone's hair gray, the supersonic turnaround.
You are correct. John Young used the Shuttle Motion Simulator at JSC to look at landing on the East Coast for a single engine out -- starting at lift off. The landing sites mentioned were to be the same as currently used for ECALs -- two engine out aborts.
Commander Young does NOT like RTLS at all and tried to get NASA to use single engine out East Coast aborts. They worked great in the sim, but it would take HUGE dollars to certify them as being safe. RTLS still remains in the system.
Danny Deger
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#1908
by
Danny Dot
on 13 May, 2009 03:56
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If Ascent Performance Margin is in the 1500-ish pounds range for Shuttle and the SSMEs are consuming propellant at the rate of around 3000 pounds per second, does that mean a nominal MECO is around a half second before an ECO shut down?
As Jim points out, ascent performance is VERY complex. To answer your question, the shuttle is very close to ECO as measured in time of burn remaining in the ET.
Danny Deger
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#1909
by
Sesquipedalian
on 13 May, 2009 06:10
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And another one.
They made such a big deal about using the remote-control capability for damaged orbiters. Now they talk about ditching a shuttle with a controlled reentry instead.
Is the option to try a remote landing at White Sands still an option?
I'm curious about this as well. According to Wikipedia, the RCO cable was left on the ISS:
http://en.wikipedia.org/wiki/STS-3xx#Remote_Control_OrbiterWhy wasn't it brought up on Atlantis on this flight? Or even left on Earth so it could go up on Endeavour in the event of STS-400 call-up?
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#1910
by
ChrisGebhardt
on 13 May, 2009 06:46
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And another one.
They made such a big deal about using the remote-control capability for damaged orbiters. Now they talk about ditching a shuttle with a controlled reentry instead.
Is the option to try a remote landing at White Sands still an option?
I'm curious about this as well. According to Wikipedia, the RCO cable was left on the ISS:
http://en.wikipedia.org/wiki/STS-3xx#Remote_Control_Orbiter
Why wasn't it brought up on Atlantis on this flight? Or even left on Earth so it could go up on Endeavour in the event of STS-400 call-up?
The RCO cable, to my knowledge, is still on the ISS.
Any damage severe enough on Atlantis to necessitate the launch of STS-400 would not be covered by the repair options/capabilities available to the crew of Atlantis (or would be so severe that, even with attempted repairs, the MMT would not be comfortable with the repair's capability to work properly). Thus, RCO-controlled reentry would be null and void as there would be no way to repair Atlantis enough to allow her to survive reentry. Hence the plan to ditch her into the Pacific.
Furthermore, an RCO-controlled reentry to White Sands from a 28.45-degree inclination orbit would violate land overflight rules... something you would
NOT want to attempt with a damaged orbiter (if it even made it far enough in the reentry profile to fly over land).
The RCO cable controlled reentry is really for ISS missions where a repair
might be enough to bring the
orbiter home safely but the risk of flying her home with a crew is too great.
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#1911
by
elmarko
on 13 May, 2009 09:47
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Thanks Chris, that pretty much covers everything I needed.
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#1912
by
elmarko
on 13 May, 2009 09:48
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One more from me, I asked in the 125 FD1 thread but it was skipped over.
After MECO there's usually an LOS due to "spreading" - can someone tell me what this is please?
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#1913
by
duane
on 14 May, 2009 01:46
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I read that a turkey vulture was struck by the shuttle last year or a few years ago upon liftoff.
Just wondering if there has been any other bird strikes to rockets in the past ? What would happen if Orion hit a bird upon accent near supersonic ? (I am assuming bad things... )
Thanks
Duane
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#1914
by
kch
on 14 May, 2009 01:51
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What would happen if Orion hit a bird upon accent near supersonic ? (I am assuming bad things... )
Well, the bird wouldn't be too happy about it ...
Seriously, I suspect that's one of the things the "boost protective cover" is there to protect against.
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#1915
by
Jorge
on 14 May, 2009 01:58
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What would happen if Orion hit a bird upon accent near supersonic ? (I am assuming bad things... )
Well, the bird wouldn't be too happy about it ...
Seriously, I suspect that's one of the things the "boost protective cover" is there to protect against.
And it's the very rare bird that can fly at the altitudes where Ares I goes supersonic. Most concern over bird strikes is at lower altitudes.
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#1916
by
oxford750
on 14 May, 2009 02:02
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Hi folks:
I just finished watching flight day 2 highlights and I saw a burn from the OMS engine.
My question is: why did it glow red on the tail but it looked like a "yellow jet" shooting to the right?
I got a screen grab of it, however I don't know how to attach it without starting a new post. I am now using "Quick-Reply"
Oxford750
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#1917
by
oxford750
on 14 May, 2009 02:04
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opps that should be flight day 3.
SORRY
Oxford750
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#1918
by
Lee Jay
on 14 May, 2009 02:12
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I got a screen grab of it, however I don't know how to attach it without starting a new post. I am now using "Quick-Reply"
Go to the top of the screen and use the regular reply button. You can attach in there.
In answer to your question, I thought it was radiative heat transfer from the engine and plume to the tail, but I can't claim to know what I'm talking about here so I'm curious to hear from one of the experts.
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#1919
by
duane
on 14 May, 2009 02:13
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yep I was wondering about that. Was not sure what altitude they went supersonic. If over 30,000 then probably not a issue
Was interested whether anything else ever hit a bird on accent ?
I guess if you have a beefy cover over the capsule, it would not be any worse to it than a bird hitting the leading edge of a 747 at cruise speed.
Duane
