Poor weather at the start of the weekend and uncertainty about Autonomous Spaceport Drone Ship (ASDS) landing conditions in the Atlantic Ocean have put paid to SpaceX’s efforts to get its next batch of 60 Starlink internet communications satellites into low-Earth orbit. Originally scheduled for Sunday, the mission initially slipped to Monday, then Tuesday, following the delay of United Launch Alliance’s (ULA) Atlas V, due to concerns about an evolving tropical depression off the Florida coastline.
But with Demo-2—the maiden voyage of SpaceX’s Crew Dragon with astronauts aboard—scheduled for Wednesday, 27 May, SpaceX has decided that insufficient time exists for the ASDS to safely recover the B1049 Falcon 9 booster core from Starlink, return it to Port Canaveral, then about-turn in enough time to also pick up the returning B1058 core from Demo-2. As such, the next launch from the Space Coast will be arguably the most momentous of SpaceX’s career: the return of U.S. human spaceflight aboard a U.S. spacecraft, atop a U.S. rocket and from U.S. soil for the first time since the end of the Space Shuttle era in July 2011.
It now looks likely that next Starlink mission, at least some of whose satellites will benefit from new “VisorSat” optical-darkening technology to limit their visibility in the night sky and corresponding impact for astronomers, will occur no sooner than June. This is a pity, as the mission is expected to mark the first time a Falcon 9 booster will have launched and safely landed on a fifth occasion. Although one other core, tailnumbered B1048, successfully flew its fifth mission in March, its attempt to land on the ASDS failed due to the premature shutdown of one of its Merlin 1D+ engines. The cause was reportedly due to a small quantity of cleaning fluid that had gotten trapped in a sensor. The B1049 core assigned to the next Starlink mission has a chequered history, having supported two previous Starlink flights in May 2019 and January 2020 and, prior to that, the launches of the final batch of Iridium NEXT satellites in January 2019 and the heavyweight Telstar 18V communications satellite in September 2018.
In hopes of achieving a launch last weekend, B1049 and a brand-new upper stage were rolled out of the Horizontal Integration Facility (HIF) to Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., on 13 May, where a successful Static Fire Test of the nine Merlin 1D+ first-stage engines was conducted. As is customary for Starlink missions, the payload fairing was pre-installed atop the stack throughout the test. The East Coast-based ASDS, “Of Course I Still Love You”, and its supporting vessels also put to sea later that same day, in anticipation of a launch at 3:53 a.m. EDT Sunday. But the delay of ULA’s Atlas V on Saturday pushed Starlink back to 3:32 a.m. EDT Monday at the soonest. And with the developing tropical depression off the southeastern coast of Florida posing added concerns for the safe recovery of B1049, launch was moved to 3:10 a.m. EDT Tuesday, before SpaceX elected to scrub the flight and delay it until after Demo-2.
This was a pity, for Tuesday promised a 70-percent probability of acceptable conditions at T-0. In its update Sunday, the 45th Weather Squadron at Patrick Air Force Base noted the departure of Tropical Storm Arthur to the northeast and cautioned against an upper-level low and associated boundary moving in from the west. But most of the predicted rain showers and storms associated were expected to weaken or be east of the launch site, although it was stressed that “lingering moisture will likely keep cloud coverage elevated”. And although the ASDS has done back-to-back Falcon 9 core recoveries in rapid-fire succession in the past—logging just eight days between the launches of the Nusantaru Satu/Beresheet mission on 22 February 2019 and the Demo-1 Crew Dragon on 2 March 2019—SpaceX’s decision to err on the side of caution is indeed a wise one.
As such, for the first time in 2020, a brand-new Falcon 9 core will be utilized to boost NASA astronauts Doug Hurley and Bob Behnken into low-Earth orbit on 27 May. B1058, as it is tailnumbered, was static-fired at SpaceX’s testing facility in McGregor, Texas, last August, prior to transfer to the Space Coast for final launch preparations. Last month, NASA Administrator Jim Bridenstine shared images of the Falcon 9’s appearance on this mission, emblazoned with not only the agency’s “meatball” logo, but also the newly-reintroduced “worm” on the B1058 core.
The Crew Dragon itself arrived in Florida in February and on 30 April its unpressurized trunk was attached to the crew module. Hurley and Behnken entered pre-flight quarantine in Houston on 13 May, ahead of their scheduled arrival at the Cape this coming Wednesday. And last week, the complete Crew Dragon was moved from its fueling facility to historic Pad 39A for integration atop the Falcon 9.
Events upcoming in the next few days include the formal Flight Readiness Review (FRR) on Thursday. Liftoff is currently scheduled for 4:33 p.m. EDT Wednesday, 27 May, with Hurley and Behnken expected to spend around 19 hours in transit before docking at the International Docking Adapter (IDA)-2 inteface at the forward end of the space station’s Harmony node. It remains to be seen how long they will remain aboard the station alongside Expedition 63 crewmen Chris Cassidy, Anatoli Ivanishin and Ivan Vagner, but based upon the capabilities of the Demo-2 vehicle a mission duration of at least 30 days and a maximum of 119 days—primarily determined by the capability of Crew Dragon’s solar panels—is the present expectation.
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