Update September 9, 2020: ULA CEO Tory Bruno tweeted out that they have found the source of the fault in the ground service equipment that caused the abort. They will be checking more equipment that is related to it to make sure it won’t happen again. Also, according to temporary flight restrictions filed with the FAA and along side notices to mariners given by the Coast Guard. It looks like the primary launch date will be September 18th at 12:00 AM with a backup date for September 19th.
After being on the launch pad since last November. The United Launch Alliance Delta IV Heavy finally had its chance to shine last week. The first launch attempt was set for August 26th at 2:16 AM EST but was pushed 24 hours upon customer request and no other explanation.
The second attempt was plagued by an issue with ground service equipment. This caused a hold at L-4 hours and 15 minutes which then pushed the launch attempt another 48 hours into early Saturday morning.
Everything was go for Saturday morning. No weather problems or anomalies were found prior to the opening of the launch window. After fueling there was a lower than normal temperature reading coming from a component in one of the three cores. This issue stayed until the planned T-4:00 hold that is built into every ULA launch. Eventually, this issue was resolved after thorough analysis that determined since the rocket would fly into sunlight, the lower temperature would be fine.
This pushed the launch back to 3:28 AM and the countdown continued. The launch continued as normal. We saw the iconic fireball caused by the excess hydrogen around the engines caused by the start up procedure. Normally a few seconds after the fireball the engines come to full thrust and the rocket lifts off the pad. In this case, the engines shut down at T-3 seconds when the rocket aborted the launch.
Other rockets with this long of a window may have been able to reset, if the data allowed it, but not with the Delta. At T-14 seconds, the ROFIs or Radial Outward Firing Igniters are fired to burn off excess hydrogen before engine start up. After these are ignited they must be replaced. The mandatory reset time is 7 days minimum.
We are still waiting on word from ULA about when the next launch attempt will happen. ULA CEO Tory Bruno did tweet out that the rocket looks good and the issue was with the ground service equipment. So pending weather and range availability, we may see this attempt this coming weekend.