There’s a bit of a logjam out at the Cape: the launch dates of TDRS-M and CRS-12 fell very close to each other, and they’re both high-priority missions for NASA. Chris Gebhardt explains in a post on NASASpaceFlight yesterday:
The issue then became that 10 August was the already requested and range approved launch date for the CRS-12 Dragon as well as the launch date the ISS Program had for crew scheduling and an upcoming Russian EVA on the Station.
Nonetheless, as both missions are NASA flights, the agency had the ability to internally determine which mission had priority over the other. Given an identical NET launch dates for both missions, NASA opted to prioritize TDRS-M over CRS-12.
TDRS-M was first delayed to August 10, which pushed CRS-12 to August 14. Yesterday, TDRS-M was delayed again to August 20, but due to the shuffle, CRS-12 stuck with August 14. This is also complicated by an upcoming Russian EVA on the ISS:
Nonetheless, NASA is leaving open the possibility of a further slip to TDRS-M pending final antenna replacement testing. Should the satellite incur an additional delay, NASA will reevaluate which mission has priority – a discussion, should it become necessary, that will have an added element to the equation: the fact that CRS-12 Dragon has to launch at least two days before an upcoming 17 August Russian EVA at the Station or be delayed until “several days after” that EVA is complete.
The priority decision by NASA delayed SpaceX’s launch of CRS-12 by a few days or maybe even a week, which isn’t a big deal. But given SpaceX’s single pad situation on the east coast right now, that also delays any other upcoming flights for them.
This type of situation is exemplary of something I’ve been hearing lately: that SpaceX is going to keep Pad 39A focused on government and Falcon Heavy flights while they fly commercial missions out of SLC-40. That means they could keep commercial operations flowing regardless of the shifting plans that are common with a program as complex as ISS.