Delta 4-Heavy: success in doubt

[rocketwatcher2001]

I'm sure I could look this up somewhere, but I just got home, and I'm feeling really lazy. I understand that the second stage burned longer than it was "supposed" to, but how much "extra" fuel(and LOX <img src="/images/icons/wink.gif" /> ) does it carry? Does anyone know why the first stage cut off "early" How smart is the rocket?, did it figure out how to save fuel by cutting off the first stage early and burning the second stage a little longer? <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>Does anyone know why the first stage cut off "early"?</i><p>I'm sure the boffins at Boeing have some ideas by now, but they haven't shared them yet.<p>><i>How smart is the rocket, did it figure out how to save fuel by cutting off the first stage early and burning the second stage a little longer?</i><p>No. The first stage underburn was entirely unexpected and unplanned. The second stage IMU would have detected the lower-than-expected velocity (okay, <i>calculated</i> it due to the low acceleration) and would have automagically increased the length of the first second-stage burn to meet preset limits. I believe that the final burn of the upper stage was a burn to depletion, so it would necessarily have been shorter than planned.</p></p></p>

 

[rocketwatcher2001]

Naj-<br /><font color="yellow">and would have automagically increased the length of the first second-stage burn to meet preset limits. I believe that the final burn of the upper stage was a burn to depletion, so it would necessarily have been shorter than planned. </font><br /><br /><br />That's what I don't understand. It made it to it's planned orbit, right? But it didn't burn all of it's fuel, and it somehow messed up? It seems like those are the kinds of mess-ups that I'd like to see more often. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

Keep checking the SpaceFlightNow thread I pointed to starting this thread. One of the articles there states:<br /><br />1730 GMT (12:30 p.m. EST)<br /><br />The DemoSat satellite simulator launched aboard the Delta 4-Heavy rocket Tuesday was delivered into an orbit 10,000 miles short of the intended altitude, according to tracking data. The payload failed to reach the proper orbit because the upper stage ran out of fuel after compensating for low performance from the first stage. <br /><br />Information shows an elliptical egg-shaped orbit with a high point of 36,406 km, low point of 19,027 km and inclination of 13.5 degrees to the equator. That is 22,623 by 11,823 miles. <br /><br />The rocket was supposed to inject the payload into a circular geosynchronous orbit of roughly 36,000 km with an inclination of 10 degrees. <br /><br /> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[rocketwatcher2001]

Thanks,<br />Sorry about that, I thought it reached it's intendend orbit. <br /><br />*EDIT*<br />When are they going to learn not to launch them when I'm out of town? I've never seen a rocket fail with my own eyes, I wear a lucky cap that has never failed. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I need to keep that in mind for the next missile program I work!<br /><br /><img src="/images/icons/smile.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

I don't know, but years ago a no ex-girlfriend threw that phrase in my direction in an...uncomplementary fashion....oops...too much information.<br /><br /><img src="/images/icons/smile.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[rocketwatcher2001]

News-<br /><font color="yellow">"...I wear a lucky cap that has never failed...." <br />Careful! <br />I remember najaB boasting "We are too far south to get the big tropical storms" ...a week before his island got clocked... </font><br /><br />You're right, what was I thinking? I was fatigued, drinking beer....and it was past my bedtime, so it can't be held against me.....I hope. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i>".....Prop, <br /><br />How dangerous is this method of venting the exhaust? To the untrained eye like mine it does seem rather "comical" that such extreme caution is taken with the flamable fuels prior to launch, yet nothing untoward is thought of engulfing the rocket in a gi-normous fireball at T-0. It seems to defy common sense even though, as SG said, a rocket is a continuous controlled explosion...." </i></font><br /><br />Hey Space,<br /><br />Sorry for the late response. I went away on a vacation and just came back. <br /><br />The Delta IV launch pad at CCAS uses an enclosed duct design much like the old shuttle pad at Vandenberg AFB (SLC-6) which, ironically, became the D IV launch pad for the west coast launch. The main reason for this design is that so it minimizes the acoustic level impact on the vehicle. This is not insignificant as it reduces strucure dry weight for the vehicle (lower dry weight = higher propellant mass fraction = higher payload, yada, yada...). It also eliminates the active water sound suppression system employed on the Shuttle launch pad which was considered costly for ELV launches.<br /><br />The *free venting* of unburned hydrogen was an unintended consequence, although you'll probably not hear that from official Boeing sources. But the bottom line is that, although spectacular visually, it does little damage to the vehicle and the spray-on-foam-insulation was thick enough that the tank insulation was not affected. <br /><br />A more serious consideration, from the point of pad safety, was in the case of engine(s) abort. In the case of engine abort, it is anticipated couple hundred pounds of gaseous hydrogen <i>per engine</i> will be pumped into the exhaust duct that, when mixed with air in the presence of ignition sources, possed a potentially explosive hazard to the pad. This was studied carefully and the radially-outward-flame-ignitors (ROFI), e.g., sparklers, such as used on the Shuttle pad are p <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i> "... I was 4 miles from the pad however I did not have a view of the pad/vehicle untile it cleared the trees. The ignition did sound like an explosion. ..."</i></font><br /><br />Sounds like flames shot out of a canyon? <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i> Well, I might be remembering it incorrectly. That has happend a few times before. </i></font><br /><br />Yeah sometime I do recall that I have CRS, but you know memory is the 2nd thing to go..... <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i> I understand that the second stage burned longer than it was "supposed" to, but how much "extra" fuel(and LOX ) does it carry? </i></font><br /><br />The 2nd stage does not carry "extra" propellant.<br /><br />It does have "reserves" just in case some engineer's calculations are wrong. (we know that has NEVER happen !!) <img src="/images/icons/rolleyes.gif" /> <br /><br />In this case, it came in useful. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[rocketwatcher2001]

Thanks Prop. <div class="Discussion_UserSignature"> </div>

 

[SpaceKiwi]

Yeah, great explanation Prop ... thanks. <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>

 

[Swampcat]

<font color="orange"><b>Delta 4-Heavy's engines snuffed out by sensor glitch</b><br /><br />Errant readings from sensors inside the inaugural Boeing Delta 4-Heavy rocket triggered the premature shutdown of its three main engines during ascent last month, causing a massive underspeed that the vehicle's upper stage could not overcome and resulting in a final orbit lower than planned, the U.S. Air Force said Friday. A team investigating results of the test launch are confident the problem can be resolved.</font><br /><br />Spaceflight Now article... <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[padrat]

I'm hearing rumors that Boing is now making plans to install a water system to minimize the hydrogen flaring.<br /><br />-Pad Rat-

 

[padrat]

The scuttlebutt is that all 3 CBCs experienced the same phenomenon, and the two strap-ons saw it simultaneously. It is suspected that the flow sensors became unwetted, possibly by vortices, fooling the computers into thinking it was fuel depletion.<br /><br />Fixing this will involve more than patching a software bug.<br /><br />-Pad Rat-

 

[mikejz]

The question is why had this issue not happened on any other CBC launches?

 

[propforce]

Highly doubt it is a flow phenomenon, too consistent to be an "error". <br /><br />Each CBC has 3 depletion sensors, what are the odds that all 12 sensors experienced the same thing at two different times ? <div class="Discussion_UserSignature"> </div>

 

[padrat]

>>Highly doubt it is a flow phenomenon, too consistent to be an "error". <<<br /><br />Then, can you explain why Canoga Park has been asked to do CFD work on the LOx feed?<br /><br />The unwetted sensors in question are mounted in pairs near the top of the LOx feedline.<br /><br />-Pad Rat-<br /><br />

 

[propforce]

Covering all the bases... part of the fault tree analysis <div class="Discussion_UserSignature"> </div>

 

[rocketwatcher2001]

How many other "Common Booster Core" launches have there been? <div class="Discussion_UserSignature"> </div>

 

[padrat]

>>The engines and tanks had flown before, but never together as this was. A resonance unique to the 3-core unit?<<<br /><br />That could explain the strap-ons, but not the core. Once the strap-ons staged, we're back to a single-stick D-IV, albeit one with a 5-M upper stage on top.<br /><br />This is a mystery that will have to be cleared up before another D-IV of any configuration flies again.<br /><br />-Pad Rat-

 

[padrat]

>>How many other "Common Booster Core" launches have there been?<<<br /><br />Three.<br /><br />-Pad Rat-

 

[padrat]

>>Covering all the bases... part of the fault tree analysis<<<br /><br />Perhaps, but the flight data supports the theory of some sort of vortex as the propellant level was getting close to the bottom of the tank.<br /><br />-Pad Rat-