HaveBlue From United States of America, joined Jan 2004, 2081 posts, RR: 1 Reply 8, posted (8 years 12 months 4 days 11 hours ago) and read 2164 times:
I could see it VERY clearly here from Daytona Beach. I didn't realize the launch was today and the phone rings and my buddy is like "what rocket am I looking at?" and I said "damnit, that's gotta be the Delta IV I've been waiting for!". Scramble outside the door and see the huge white plume of smoke, which ended oddly a little ways up the sky, then it was just clear and you could see the rockets fire clearly up above that. I'm assuming the plume stopped where the seperation occurred, but it looked kinda low.
Still, an impressive sight, wish I had caught the whole thing. Very happy that it was successful, especially after all the delays.
"The root cause of the anomaly has been identified as a fluid cavitation within the liquid oxygen feed system. Analyses show that the cavitation originated at the entrance of the propellant feedline, where a filtration screen and turning elbow restrict the propellant flow as it accelerates leaving the tank."
Areopagus From United States of America, joined Sep 2001, 1364 posts, RR: 1 Reply 13, posted (8 years 9 months 1 week 8 hours ago) and read 1544 times:
I saw the article on this at Spaceflight Now, which quoted the Air Force report:
"Analyses show that the cavitation originated at the entrance of the propellant feedline, where a filtration screen and turning elbow restrict the propellant flow as it accelerates leaving the tank. This feedline restriction has been present in all previous Delta 4 flights, but the unique combination of vehicle acceleration, liquid level in the tank, and propellant flow rate for this mission, reduced the fluid pressure enough to enable the creation of gaseous oxygen at this location as the tanks emptied," Wednesday's Air Force statement said.
But I'm left wondering, what's so unique about it? The acceleration at center core burnout must have been higher (well, at least different) than at strap-on burnout, and the problem occurred in both conditions. As far as liquid level in the tank and flow rate, how would this differ from earlier flights?