STS-114 Mission Update Thread (Part 2)

[marslauncher]

Any more news?

 

[erauskydiver]

Press conference coming up very soon ("Next") on NASA TV.

 

[llivinglarge]

AOA? Abort or abandon?

 

[georgeniebling]

AOA = Abort Once Around ...<br /><br />one of the early Shuttle flights actually *used* this abort event as I remember .....

 

[elguapoguano]

Ok I know we want this launch to be perfect. And nobody wants to be the guy that says go fly, and then have a bad day. But.... If it takes two sensors to cause MECO and the sensors are only turned on 8 seconds before predicted MECO. Why didn't we fly? Even in the very worst senario, MECO happens the whole 8 sec early, would we still have enough left in the OMS to get to ISS? If the answer is no, then I understand the scrub, if the answer is yes, I guess I don't get it. <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[llivinglarge]

No it was an ATO "Abort to Orbit"...<br /><br />STS-51-F was aborted 5 minutes into flight when the engines cut off.

 

[georgeniebling]

my bad .... you're right ....

 

[georgeniebling]

http://news.yahoo.com/fc/science/space_shuttle

 

[shuttle_rtf]

I'm sorry to say that Wayne Hale is Mr Optimistic when it comes to making claims like that. Let's not forget he made no reference to the ECO (double) fault on Tanking Test 1, nor the overcycling of the pre-press valve.<br /><br />The conference immediately after he said everything went great.<br /><br />I prefer to listen to the engineers, not the managers, when it comes to this.

 

[SpaceKiwi]

Anyone catch the press briefing just finished? I turned the TV on just in time to see people leaving the room. What's the prognosis? <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[robot_pilot]

>That's quite a small timewindow compared to the total burn<br /> />time. What happens if engines run dry before that 8<br /> />seconds, does some other system detect that and do cut<br /> />off?<br /><br />Well, first - it's not necessarily eight seconds. This time is typically eight seconds, but it does vary a little bit... probably a nit-picky thing to say but it's not a fixed number, that was my point. The arming is done when the vehicle reaches a certain velocity, which is typically around eight seconds prior to MECO.<br /><br />Now, the ECO sensors were put in place to protect us only from a circumstance where one of the SSMEs might be consuming too much of one propellant. Case in point - STS-93, which (coincidentally) was Eileen Collins' first flight as Commander - right at liftoff one of the SSMEs blew out a plugged post, and so there was a small amount of one of the propellants (I'm sorry, I don't remember which but I want to say that it was LOX) leaking out of the engine. This was somewhat similar, consumption-wise, to one of the SSMEs consuming its propellant at an unusually high rate. Near the planned MECO, that propellant was running so low that it went dry a couple seconds before the projected MECO time - tripping the two ECO sensors needed to protect the SSMEs. The engines did shut down early, but just in time to prevent them from ingesting vapors that would have resulted in a catastrophe.<br /><br />The ECO sensors are only in place to prevent against such an event. It's possible that an SSME will consume higher than expected propellant, and while it might not be a huge amount, over 500 seconds it adds up and would cause the tank to run dry (even with any reserves used up) a few seconds early. So, if the ECOs are armed 8 or 9 seconds prior to MECO, they will protect the vehicle against a catastrophic loss in such a case.<br /><br />As far as I know, there's nothing to protect the system from running out of propellant say, halfway through flight.

 

[redgryphon]

Hi Kiwi.<br /><br />I saw most of the briefing. On draining the tank the LH2 Sensor #2 stayed WET for 3 hours after drain, then went DRY. ie intermittent fault again. They are currently inerting the tank. Tomorrow they'll make a decision whether to top up the reactants in prep for another attempt, or drain them to allow orbiter access. That decision comes as part of the overall troubleshooting plan which will be firmed up tomorrow. Today seems to have been a day of organizing a massive engineering analysis effort. <br /><br />Wayne, Mr Optimistic, said they could launch Sunday, but really thought that was unlikely. They can maintain a high level of launch readiness for a few more days, supporting a launch up to early next week. Otherwise they need to back out a little more. <br /><br />No decision on roll-back. Could still make the July window with a roll-back as long as the work in the VAB didn't take too long. <br /><br />There is a replacement box available, but it also has some questions over operation at low voltage. It did pass its acceptance test, however. A wholly new box would take 10-21 days to build up, depending on how much you wanted to add to the new box.<br /><br />Engineers discussing how the thermal environment of the box affects its operation. There was no mention of or question about the cold plate. <br /><br />Storms were withing 20 nm of the SLF at launch time yesterday, so there would have been a scrub.<br /><br />Crew staying at KSC for now.

 

[shuttle_rtf]

Good work with the round up there!

 

[SpaceKiwi]

Thanks red, great summary, I appreciate that.<br /><br /><img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[robot_pilot]

Hi, just wanted to add one thing to this excellent summary:<br /><br /> />On draining the tank the LH2 Sensor #2 stayed WET for 3<br /> />hours after drain, then went DRY. ie intermittent fault again.<br /><br />I have read this on the Florida Today site as well but I'm not so sure it's really "intermittent". During the drain, they kept both LOX and LH2 ECO #2 in "checkout" mode, which was supposed to make them both indicate a false reading of DRY. The sensors would remain in this configuration for the entire drain, to see if the LH2 ECO would change to DRY when the other three did. As you guys know, it remained WET when the other three sensors went DRY.<br /><br />However, I thought that the ECO sensor #2 only went DRY when they switched the checkout mode OFF (if someone knows if this is true or not, please post - but I have been told by someone at KSC that this is what happened). If so, then the problem is most definitely not "intermittent" and would not be as hard to find.<br /><br />However, I do know that they've been calling this problem "intermittent" from the start, which was definitely incorrect - the sensor worked perfectly when it was not in checkout mode, and if they finally turned checkout mode OFF and that's when it went DRY - then the problem is most likely with the circuit itself. I do know there are a lot of people looking around the Orbiter today, I hope they find it quickly...

 

[tap_sa]

<font color="yellow">"Hope this helps!"</font><br /><br />Helped a lot, especially the real life example, thanks! That must have been one lucky failure that the SSME just kept slowly leaking without further damage, considering the pressure and temperature inside it.

 

[robot_pilot]

I do remember that it was a surprise, because Commander Collins announced something about it immediately after liftoff - their instrumentation indicated a problem, and I think it was only after their return that engineers were able to inspect the SSME to find the missing post plug. I do remember being incredibly relieved when they hit MECO, but also incredibly surprised when someone yelled out that it was ECO-tripped.<br /><br />Rocketdyne builds an incredible engine with the SSMEs, and the fact that the missing post plug didn't result in more damage is a testament to the great work they do.

 

[star_sirius]

<blockquote><font class="small">In reply to:</font><hr /><p>The LOX ECOs are in the feed line leading to the SSMEs and in fact are in the feedline which is in the Orbiter aft fuselage. <br /><br />TheLH2 ECOs are in the bottom of the LH2 tank. <br /><br />The latest problem is with the fuel sensor number 2. <p><hr /></p></p></blockquote>OOps! I'm not used to abbreviations. Am i correct?<br /><br />LOX "Liquid Oxygen"<br />ECO "Engineering Change Order" <br />ECOS "Experiement Computer Operating System"?? <br />SSMEs "Space Shuttle Main Engines "<br /><br />Is LH2 Liquid Hydrogen? <br /><br />Wow S_G, did you write below software? Am very interested in any shuttle sofware!! This is version 2, what version are you using now? <img src="/images/icons/wink.gif" /><br /><br />OMS-RCS computes and displays resulting failures within the Orbital Maneuvering System (OMS) and Reaction Control System (RCS) engines. <div class="Discussion_UserSignature"> <font size="0" color="#10bdee"><strong>A dazzling bluish luminosity from A distant south pacific.</strong></font><p><br /><img id="cb51e87e-8221-424c-8ff2-78c95122196c" src="http://sitelife.livescience.com/ver1.0/Content/images/store/11/15/cb51e87e-8221-424c-8ff2-78c95122196c.Large.jpg" alt="blog post photo" /></p> </div>

 

[marslauncher]

ECO = Engine Cut Off <br /><br />LH2 is indeed Liquid Hydrogen

 

[shuttle_rtf]

And more one being I believe you've seen ECOS as Engine Cut Off (Sensors).

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>I have read this on the Florida Today site as well but I'm not so sure it's really "intermittent".<p><hr /></p></p></blockquote><br /><br />In the post scrub press briefing from yesterday, there was a question from a journalist about the ECO sensor failure being characterised as an "intermittent". He made the point that the failure on <b>this</b> occasion should be classed as a hard failure. The panelist which fielded the question agreed that it was a hard failure, though Griffin went on to make the observation that the on-going problems with ECO sensors were generally intermittent in nature. <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[marslauncher]

Today should be the day that we find out more info regarding what the troubleshooting plan entails and possibly where to look, I hope they isolate and fix this problem quickly without having to roll back to the VAB, I would love to see a launch in July. The longer they wait to launch (Wait on technical issues not because they dont want to launch) The less likely it will be to fully complete the ISS by the 2010 deadline.

 

[marslauncher]

I fear that a delay to next spring would put a lot of pressure from congress on NASA to potentially cancel the ISS

 

[redgryphon]

Bill Harwood at the press conference yesterday asked about the November window for STS-121 if 114 moved to September. At the moment it is only a few days long. Hale said some analysis showed it could be a few days longer than that, and that if NASA had to, they would go for it.

 

[llivinglarge]

Other than the Mercury Atlas 9 capsule, has a pilot ever had to a manual re-entry using the shuttle?