At the start of 2019’s fifth month, SpaceX has successfully launched its fifth mission of the year, with a spectacular pre-dawn liftoff of an Upgraded Falcon 9 from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla. Lighting up the darkened sky along the shores of the Space Coast, the 230-foot-tall (70-meter) rocket—its Block 5 core tail-numbered “B1056” and making its maiden flight—departed Earth during an “instantaneous” window at 2:48:15 a.m. EDT Saturday and smoothly delivered the CRS-17 Dragon cargo ship into low-Earth orbit to begin a two-day pursuit of the International Space Station (ISS).
This particular Dragon had previously seen service on the CRS-12 mission in August 2017 and marked the sixth occasion in under two years that one of SpaceX’s cargo ships had made a repeat flight to the ISS. Current plans are for Dragon to return to Earth at the end of May and, when combined with the 34 days logged from CRS-12, this particular spacecraft is expected to total around two months off the planet across its two missions.
Less than nine minutes after launch, B1056 descended to a smooth touchdown on the Autonomous Spaceport Drone Ship (ASDS), nicknamed “Of Course I Still Love You”, situated offshore in the Atlantic Ocean. It marked the 25th successful landing of Falcon 9 core hardware onto the deck of a drone ship—either the East Coast-based OCISLY or the West Coast-based “Just Read the Instructions” (JRTI)—since April 2016.
All told, the first half of 2019 has seen an impressive tempo of launches for SpaceX, with one flight per month, equaling a similar achievement of five flights by the beginning of May back in 2017, although somewhat less than the eight missions accomplished in the same time period last year. The multi-satellite Iridium NEXT low-orbiting constellation was completed in January, Israel’s (ultimately) ill-fated Beresheet lunar lander was boosted towards the Moon in February, the Crew Dragon undertook a successful unpiloted test flight to the ISS in early March—before later succumbing to an explosive failure during a ground run of its SuperDraco thrusters on 20 April—and the Falcon Heavy saw its first operational launch, just last month.
Looking ahead beyond May, SpaceX expects to launch the initial members of its much-hyped Starlink internet communications satellite network, two more ISS-bound cargo Dragons and another Falcon Heavy.
Originally targeted to fly on 26 April, the launch of CRS-17—which is launching under an extension to the first-round Commercial Resupply Services (CRS1) contract between NASA and SpaceX, signed back in December 2008 and modified in 2015-2016—was routinely postponed until the 30th, which was described as “the most viable date…due to station and orbital mechanics constraints”. Launch slipped an additional 24 hours to 1 May when the customary Static Fire Test of the Upgraded Falcon 9’s nine Merlin 1D+ first-stage engines moved to the right. Following the conclusion of the test, launch was firmly scheduled for Wednesday, 1 May.
However, on Monday morning, the ISS Program identified an issue with one of the station’s four Main Bus Switching Units (MBSUs). These serve as distribution hubs for the Electrical Power System (EPS) and each 220-pound (100-kilogram) MBSU supports two of the eight power channels on the sprawling multi-national orbital outpost. The one which failed on 29 April was MBSU-3, which supports two starboard-side power channels. Delivered with the S-0 truss during shuttle mission STS-110, way back in April 2002, it had experienced no previous troubles and had enjoyed 17 years of unblemished operations. It was robotically replaced with one of two spare MBSUs, located on External Stowage Platform (ESP)-2, on Thursday. The failed MBSU-3 will remain temporarily parked on ESP-2 for the foreseeable future.
“Great efforts from the robotics ground controllers in Mission Control Houston,” tweeted Expedition 59 astronaut Nick Hague, “for successfully replacing the MBSU and restoring full power on station so we can support the arrival of the SpaceX Dragon spacecraft.”
One of the key effects pertaining to CRS-17 was a loss of redundancy in the 57.7-foot-long (17.6-meter) Canadarm2, which will serve a critical role during the robotic grappling and installation of Dragon onto the Earth-facing (or “nadir”) port of the station’s Harmony node. Another, less serious impact was upon the Alpha Magnetic Spectrometer (AMS), although NASA advised AmericaSpace that the instrument’s science-gathering capability was down for a “negligible” period of time.
Missing the 1 May launch date target was unfortunate, for weather conditions were highly favorable at 80-percent, with a slight drop to 70 percent for a two-day slip to Friday. SpaceX teams pressed ahead with final launch readiness, wrapping up the late loading of cargo and Launch Readiness Review (LRR) activities. The Upgraded Falcon 9, with Dragon perched at its tip, was rolled horizontally out to SLC-40 and teams stepped smartly through a nominal countdown. It was not to be. Friday’s attempt was scrubbed in order to allow SpaceX teams to address a ground-side helium leak and deal with an electrical issue on the ASDS, with Saturday, 4 May established as the next viable opportunity.
Following a smooth countdown under a crystal clear moonless sky, liftoff occurred at 2:48 a.m. EDT, as the booster performed to perfection on the Falcon 9’s 70th flight in a “single-stick” configuration, smoothly delivering the CRS-17 Dragon to orbit. Thirteen minutes after launch, following separation from the second stage, Dragon’s power-producing solar arrays were successfully deployed. It will be robotically grappled and installed early Monday, 6 May, with Canadian astronaut David Saint-Jacques and NASA’s Nick Hague at the controls of Canadarm2 in the station’s multi-windowed cupola.
Coming barely a couple of weeks after the arrival of Northrop Grumman’s NG-11 Cygnus cargo ship at the adjacent Unity node, the launch and berthing of the CRS-17 Dragon promises a busy period for the six-strong Expedition 59 crew of Commander Oleg Kononenko of Russia, U.S. astronauts Anne McClain, Nick Hague and Christina Koch, veteran cosmonaut Alexei Ovchinin and Canada’s David Saint-Jacques. This is not the first time that “dual berthed ops” have occurred on station, with the visiting vehicles of both Commercial Resupply Services (CRS) partners, SpaceX and Northrop Grumman, simultaneously in residence. That accolade belongs to the OA-5 Cygnus and CRS-8 Dragon, which arrived in late March and early April 2016. However, the dual berthed ops with NG-11 and CRS-17 in the coming days represents the first occasion that two ships from the two CRS providers have arrived in such a short period of time.
“It will definitely be a large workload for the crew, but teams on the ground always make sure there is a plan to keep it manageable before these flights get scheduled,” NASA’s Dan Huot told AmericaSpace. “Cargo ops (both loading and unloading) will happen in tandem with both vehicles.” He added that the entire U.S. Operational Segment (USOS) crew “will have cargo loading/unloading tasks on their timeline.”
Aboard Dragon’s pressurized cargo module for CRS-17 is an estimated 3,250 pounds (1,477 kg) of equipment, experiments and supplies. This figure includes approximately 1,590 pounds (698 kg) of science hardware, 760 pounds (345 kg) of crew supplies, 754 pounds (342 kg) of vehicle equipment, 165 pounds (75 kg) of computer resources and smaller quantities of Extravehicular Activity (EVA) tools and parts and materials for the station’s Russian Operational Segment (ROS). External hardware in Dragon’s unpressurized “trunk” totals 2,130 pounds (965 kg) and is visibly dominated by NASA’s next-generation Orbiting Carbon Observatory (OCO-3), which has been provided by the Jet Propulsion Laboratory (JPL) in Pasadena, Calif.