Hmm.... per SFN this launch has slipped to October 23 at 5:53-6:12 pm EDT (21:53-22:12 UTC). I wonder why?
ULA @ulalaunch@Cosmic_Penguin Yes. To allow technicians time to change out a faulty ground system valve on the liquid oxygen storage tank prior to launch.
ULA Cape Canaveral Air Force Station, Fla. (Oct. 18, 2013) -- The launch of the GPS IIF-5 mission on a ULA Delta IV launch vehicle, currently scheduled for Oct. 23, 2013, is being delayed. The team has continued with Phase II of an investigation related to a successful Delta IV launch that occurred in October 2012 in which the second stage RL10B-2 engine thrust was lower than expected. It was determined that a fuel leak occurred within the engine system and that this fuel leak caused the low thrust. The ongoing Phase II investigation has included extremely detailed characterization and reconstructions of the instrumentation signatures obtained from the October 2012 launch and these have recently resulted in some updated conclusions related to dynamic responses that occurred on the engine system during the first engine start event. The GPS IIF-5 Delta IV launch is being delayed to allow the technical team time to further assess these updated conclusions and assess the improvements already implemented and determine whether additional changes are required prior to the next Delta IV launch. The Delta IV booster for the GPS IIF-5 mission has completed the standard processing and checkout on the launch pad and will be maintained in a ready state for spacecraft mate and launch pending completion of this assessment. A new launch date will be established when the assessment of the updated dynamic response information is completed in the coming weeks. The processing of Atlas V vehicles for upcoming missions including the Nov. 18 launch of the MAVEN mission for NASA are proceeding as planned. Jessica Rye, APRULA Communications
My guess is it's got something to do with the "some updated conclusions". I.e. they OK-d the engine based on earlier investigation but they're now having some second thoughts about that.
Since the last few flights went off without a hitch, I would say it's not a multiple engine issue. Whatever happened seems to be very rare/unlikely, they likely just want to understand it as best as they possibly can in order to guarantee this doesn't happen again.
Quote from: ugordan on 10/19/2013 11:31 AMSince the last few flights went off without a hitch, I would say it's not a multiple engine issue. Whatever happened seems to be very rare/unlikely, they likely just want to understand it as best as they possibly can in order to guarantee this doesn't happen again.A hold preventing launch was placed on several DIVs by Phase II of the commission to allow for inspection of the DCSS and the engine modifications and other changes implemented after the engine failure. If they are happy with the results they will release this DIV just like all of the DIVs since engine incident happened. This process will repeat for the foreseeable future for DCSS stages that have had the required mods implemented while the engine was attached to the DCSS during the modification process. This stage by stage review by the investigation will end soon as the engines that were not installed at the time of the incident can be inspected before installation to a DCSS. This is my understanding. Also RL-10C conversions begin flying at the end of 2014 to the beginning of 2015.