STS-122 (1E) Updates

[larper]

Is it the engine that explodes, or the fuel pump that cavitates, leading to an explosive destruction? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[MeteorWayne]

Like I said, I can't remember the details. Still trying to find where I heard or read it. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[Testing]

I can't remember the exact numbers (too many years) but the turbopumps are spinning REAL fast. Imagine the impact on the impellor blades of having liquid and then not, or a burp. Very bad. <div class="Discussion_UserSignature"> </div>

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>Is it the engine that explodes, or the fuel pump that cavitates, leading to an explosive destruction?<p><hr /></p></p></blockquote><br />As I understand it, the turbopump can only spin as it does with the assistance of the resistance of propellant flowing through it. In a 'dry mode' the pump spins too fast and flys apart, creating shrapnel and destroying the engine and Orbiter.<br /><br />With respect to the ECO sensors, I can't recall ever hearing of a mission during which the SSME's were instructed to shutdown due to low propellent in either tank? That is to say, MECO has always been as a result of reaching the nominal altitude for the flight profile they are on.<br /><br />Which makes the quadruple redundency seem a tad excessive when the ECO sensors have been ongoing problem over the last couple of years.<br /><br />I think they will end up 'rationalising' this in order to create a situation whereby the launch commit rule will change to only two of four ECO's good to fly. They will try and spin it good, but it will come down to schedule pressure IMVHO.<br /><br /><img src="/images/icons/smile.gif" /><br /><br /> <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>

 

[MeteorWayne]

Post MMT News conference in about 10 minutes, at the top of the hour.<br /><br />Allegedly, of course <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> <br /><br />Edit: The top of the hour has come and gone with no indication....<br /><br />Edit 2:<br /><br />Neither the NASA site or spaceflight now has been updated in hours <img src="/images/icons/frown.gif" /><br /><br />NASA's Space Shuttle location last update was 2:15 AM, 17 hours ago.<br /><br />Very bad, for the new improved site.<br /><br />??<br /><br />Edit 3:<br /><br />Now it's NET 8PM EST (0100 UT) for the news conference.<br /><br />Edit 4: NET 8:15 PM EST<br /><br />I know you are shocked, but edit 5 is 8:45 EST.................... <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[erioladastra]

<br />"Which makes the quadruple redundency seem a tad excessive"<br /><br />Several times we have been within 2 seconds of the ECO levels - when you think about 8.5 minute flight, that is a small margin. Tad excessive doesn't seem to be a fair assessment.

 

[erioladastra]

No go for Saturday - will keep working and looking at a Sunday option.

 

[MeteorWayne]

OK, NET 9PM EST.<br /><br />PLEASE do not hold yer breath... <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[MeteorWayne]

Scribblenotes...<br /><br />No go Saturday, will reevaluate during MMT meeting tomorrow.<br />A third sensor (#2) also failed for a short time AFTER detanking during "boiloff" #3 started working again first during detank, then #4.<br /><br />Flight crew recommended 4 of 4 working be reinstituted as Launch Commit Criteria, WH concurred.<br /><br />It is unlikely a root cause will be found during this launch window, but based on previous experience, when these failures have occured during the first tanking, everything has worked great the second time.<br /><br />To provide extra fuel margin, launch window will be shortened to 1 min (vs the total window of 10 min, with cneter time +5 min being the actual normal window). This better alignment means less "propellant" is needed.<br /><br />So, current plan is to aim for Sunday (70% chance good weather), with 24 hour delay (also 70%) possible. After that, a 3 day standown is required, which leaves only the 13th as a potential launch day in this window.<br /><br />Launch would be ~3:20:50 PM EST SUnday.<br /><br />MW <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[scottb50]

It seems the real problem is assuring the needed propellant is in the tank at launch due to boil-off. Why not reduce the time between loading and launch?<br /><br />I would also think a turbo-pump rpm sensor would be a pretty easy fix, if it suddenly starts to go crazy cut off everything, there has to be a margin between normal speed and boom. <div class="Discussion_UserSignature"> </div>

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>Several times we have been within 2 seconds of the ECO levels<p><hr /></p></p></blockquote><br />I stand corrected, erioladastra. I didn't realise it had been so close on occasion. Good hunting to you and your colleagues trouble-shooting the problem.<br /><br /><br /> <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>

 

[halman]

Scottb50,<br /><br />By the time an RPM sensor can fire and the system react, the rpms are already going through the roof. Cutoff must occur while there is fluid in the impellers.<br /><br />Unfortunately, we are looking at determining the physical presence of something which is very cold. Immersion in liquid hydrogen tends to alter many characteristics of materials and processes, making reliability suspect. Going with the best design at the time, and overbuilding, then requiring multiple redundancy, this was the only way that the safety of the crew could be assured without designing the orbiter with a detachable crew compartment. The weight penalty of such a design negated the abilities of the orbiter to carry sizable payloads, so the system had to be made as fail-safe as possible.<br /><br />To be able to inject fuel into a combustion chamber operating at pressures in the thousands of pounds per square inch, the pumping system must generate even higher pressures. When the designs were finalized in the mid 1970's, the turbopumps of the orbiter were the latest word in hydrodynamics. I have no idea, but I would imagine that we have learned a few things since then, and could build something better if we wanted to. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[montmein69]

<font color="yellow">Unfortunately, we are looking at determining the physical presence of something which is very cold. Immersion in liquid hydrogen tends to alter many characteristics of materials and processes, making reliability suspect. Going with the best design at the time, </font><br /><br />Maybe the ECO sensors used in the ET were of the best design 25 years ago. But now for unknown reason the system is completely erratic.<br /><br />It is a hard job to decide to change ... but new sensors with high reliability exist and are used for space launchers.<br /><br />http://www.dta.airliquide.com/space/index_space1.1.html<br /><br />and probably in the same way of design for an american cryogenic launcher like Delta IV Heavy. <div class="Discussion_UserSignature"> </div>

 

[Testing]

So all you have to do is go thru the process of getting a new unproven component man rated. Piece of cake, right? Two years into a change to an Atlas Centaur compont now. The cost and risk are so high that there can be a VERY low % in an analysis of failure. <div class="Discussion_UserSignature"> </div>

 

[bobblebob]

Can Nasa trust the ECO sensor now in this ET? Id be very apprehensive to put my trust in sensors that fail and then come back online<br />

 

[farmerman]

No NASA can't do that very easily. I saw photos of them replacing the eco's they had to remove the foam over the tank lid, unbolt the lid from the tank, and then replace the sensors. These sensors are in a sense the fuel guage for the tank. First I hope that they find the problem today, if they decide to go on two sensors tomorrow, I hope that they reviewed the data very carefully because for some reason this has me nervous that they are thinking about going on two sensors. I would tank the hydrogen as full as the weight limits would allow to reduce the chance of running out of fuel.

 

[MeteorWayne]

Well, maybe. In all previous cases, the second time the tank was filled, they have worked flawlessly, all the way uphill. They suspect that will happen this time as well. But just to be sure, they are tightening the launch criteria to require that all 4 (rather than just 3 of 4) are working after tanking in order to launch. <br /> This is just a backup system, but a crucial one just in case it's needed.<br />Apparently as well, the "wet" signal from these sensors when they fail is different that the normal "wet" signal, additional instrumentation that has been added allows them to tell whether it's a sensor failure, so this gives a better way to asses the accuracy of the information.<br /><br />Even if only 2 sensors are working properly, if they both show "dry" it would initiate main engine shutdown. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[MeteorWayne]

Well they're not really the fuel gauge. The fuel gauge is based on F=ma.<br /><br />They calculate instant by instant the force of the engines and the acceleration measured by the inertial guidance unit. This allows the mass of the Shuttle to be calculated. The amount of mass missing since launch tells you how much propellant you've used, hence how much is left.<br /><br />These sensors are more like the little light that goes on with modern cars that tells you you are running low on fuel. Just a warning that it's getting low. In a car, it's time to refuel; on the shuttle, it's time to shut the engines down. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[erioladastra]

"No NASA can't do that very easily. I saw photos of them replacing the eco's they had to remove the foam over the tank lid, unbolt the lid from the tank, and then replace the sensors. These sensors are in a sense the fuel guage for the tank. First I hope that they find the problem today, if they decide to go on two sensors tomorrow, I hope that they reviewed the data very carefully because for some reason this has me nervous that they are thinking about going on two sensors. I would tank the hydrogen as full as the weight limits would allow to reduce the chance of running out of fuel. "<br /><br />May not be the sensors at all but somewhere along the wiring path.

 

[erioladastra]

"Those were LOX ECOs correct?"<br /><br />I think these were the hyrdogen ones. Hale said we has seen them flash just after MECO but it was due to sloshing, but the data show we were still under /> 1 g.

 

[bobblebob]

What time is tanking tomorrow? Assuming Nasa give tho go ahead for it

 

[bobblebob]

http://www.nasa.gov/images/content/122488main_ECO_sensors.jpg<br /><br />Useful pic of the sensors and their location

 

[MeteorWayne]

Not yet.<br /><br />They are having a MMT meeting this afternoon to determine whether to proceed or not, 1PM IIRC. So there will be another news conference after that.<br /><br />I predict erioladastra will let us know about 45 minutes before the news conference starts <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[bobblebob]

Just listened to a conference on Nasatv (assume its one repeated from yesterday) and they said 5:55am<br /><br />MMT meeting today again, so lets play a game of guessing when the conference will be <img src="/images/icons/wink.gif" /> Im going for 9pm ET

 

[MeteorWayne]

Well the MMT is 2 hours earlier, my prediction is 5:15 PM <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>