Actor Bill Murray might not be aboard, but SpaceX’s B1056 first-stage core will glimpse a “Groundhog Day” of its own on Wednesday, 24 July, when it launches a second mission to the International Space Station (ISS) in a matter of less than 12 weeks. Previously utilized back in May to deliver the CRS-17 resupply ship to the sprawling multi-national orbital outpost, the blackened and scorched Upgraded Falcon 9 core—teamed with a sparkling-fresh second stage and brand-new Dragon cargo craft—is slated to rise from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., during an instantaneous “window” at 6:24 p.m. EDT.
Assuming the mission launches on time, the CRS-18 Dragon will berth at the Earth-facing (or “nadir”) port of the station’s Harmony node early Friday, 26 July and remain part of the ISS for four weeks, with unberthing and departure presently targeted for sometime after 19-20 August.
It was suggested at the time of CRS-17 in May that NASA would fly three consecutive Dragon missions atop the same B1056 core, although this remained unclear on the eve of the CRS-18 launch. “Can only confirm that the Falcon 9 approved for use on CRS-18 was previously used for CRS-17,” NASA’s Dan Huot told AmericaSpace. “Booster reuse is still approved by NASA on a case-by-case basis.”
B1056 might not yet be confirmed for a third ISS-bound flight, but CRS-18 will mark the first time that a Dragon spacecraft has flown on a third occasion to the sprawling multi-national outpost. Previously deployed in support of the CRS-6 and CRS-13 flights, launched in April 2015 and December 2017, respectively, Wednesday’s launch also represents the seventh reuse of Dragon hardware—and the sixth reuse in an unbroken row of missions—since June 2017.
Primary payload for the mission, tucked securely into Dragon’s unpressurized “trunk”, is the second International Docking Adapter, numerically designated “IDA-3”, which will provide a secondary port at the space station for visiting Commercial Crew vehicles.
Original plans called for two Boeing-built IDAs—with IDA-1 sitting at the forward end of the Harmony node and IDA-2 on its space-facing (or “zenith”) port—but in June 2015 IDA-1 was lost during the CRS-7 launch failure. A year later, in July 2016, IDA-2 successfully reached orbit and was attached to the forward end of Harmony a few weeks later by Expedition 48 spacewalkers Jeff Williams and Kate Rubins, thereby taking up the role of the original IDA-1.
In February 2016, NASA and Boeing finalized a $9 million contract to build and test a replacement IDA in the Space Station Processing Facility (SSPF) at the Kennedy Space Center (KSC) in Florida. IDA-3 arose from around 300 extant ground spares (representing about 70 percent of the whole), with original hopes that it may launch as soon as the spring or fall of 2017, but this date was pushed back several times as the Commercial Crew Program (CCP) suffered extensive delays and key ISS science payloads—including the Global Ecosystem Dynamics Investigation lidar (GEDI)—took priority.
Like IDA-2, the new IDA-3 is fully compliant with the International Docking System Standard (IDSS), an effort by the ISS Multilateral Co-ordination Board to create an international spacecraft docking standard for the U.S. Operational Segment (USOS). “Connecting spacecraft from different nations has required unique development and expensive integration and test,” NASA Headquarters conference notes from April 2011 explained. “Expansion of spacefaring nations (and non-governmental entities) will compound this issue in the future. Exploration co-operation could be much easier with internationally-accepted interface standards.” As well as having a firm heritage in flight-proven design, IDSS incorporates low-impact technology, which “accommodates a wide range of vehicle contact and capture conditions”.
The 1,150-pound (520-kilogram) IDA-3 will sit atop Pressurized Mating Adapter (PMA)-3, which was relocated from the station’s Tranquility node to Harmony’s zenith port via a ballet of spacewalking and ISS robotics, back in March 2017. The new docking port will effectively convert PMA-3 from its original Androgynous Peripheral Attach System (APAS)-95 specification to Boeing’s new Soft Impact Mating and Attenuation Concept (SIMAC), which NASA accepted in late 2012 to satisfy its Commercial Crew requirements and replace earlier plans for an international Low-Impact Docking System (iLIDS).
Also aboard CRS-18 are a raft of critical science payloads for the ISS itself. The Biorock investigation, provided by the University of Edinburgh in the United Kingdom, will explore the interactions between microbes and rocks in a liquid phase and how they are affected by the reduced-gravity conditions in low-Earth orbit. Specifically, low levels of thermal convection are known to minimize the natural stirring in liquids and gases and may restrict the supply of food and oxygen to bacteria, thereby hampering their growth. It is expected that data from Biorock will provide insights into bacterial/rock interactions both on Earth, in microgravity conditions and in the one-third-gravity environment on Mars. This is expected to prove beneficial when devising life-support systems with microbial components for long-term deep-space missions and for space mining applications in support of lunar or Martian bases and eventual colonies.
The Space Tango-Induced Pluripotent Stem Cells experiment seeks to examine how microglial cells—a type of immense defense cell, found in the central nervous system—grow, move and change in the microgravity environment. Data from this investigation may offer valuable insights into characterizing, understanding and devising therapies for conditions such as Parkinson’s disease and multiple schlerosis. More broadly, understanding nerve-cell growth and survival, together with changes in gene expression in space, are expected to yield clues about how best to protect astronauts on longer missions into deep space.
The BioFabrication Facility (BFF) will seek to 3D-print, for the first time, organ-like tissues in microgravity, as a stepping-stone toward long-term plans to manufacture whole human organs in space with refined biological 3D-printing technologies. NASA’s Cell Science-02 experiment will gain further information on the practicalities of carrying out bone-fracture repair/regeneration programs on future missions, whilst the MVP Cell-02 investigation will utilize NASA’s Multi-Use Variable-g Platform—launched to the station aboard the CRS-14 Dragon in April 2018—to understand the evolution and adaptability of the fast-growing Bacillus subtilis bacterium to microgravity conditions. Its core characteristic of rapid growth will allow it to be observed through many generations over a matter of just a few weeks on-orbit.
According to NASA’s Dan Huot, the payload for CRS-18 totals 5,097 pounds (2,312 kg), of which 3,920 pounds (1,778 kg) is pressurized cargo and 1,177 pounds (534) is unpressurized. A successful Static Fire Test of the nine Merlin 1D+ first-stage engines occurred on Friday evening, 19 July. Weather conditions for Wednesday’s opening launch attempt are predicted to be only 30-percent favorable, deteriorating to just 20 percent in the event of a 24-hour scrub to Thursday. Unsettled weather, thunderstorms from the interior of Florida and an elevated risk of lightning considered primary violating factors.
Assuming an on-time launch on Wednesday, the CRS-18 Dragon will arrive at the ISS early Friday morning, to be robotically captured by Expedition 60 Flight Engineers Nick Hague and Christina Koch. Their newly-arrived crewmate Drew Morgan will back them up, monitoring the cargo ship’s systems during final approach. According to NASA’s Rob Navias, current plans are for IDA-3 to be robotically extracted from Dragon’s trunk in August and moved to the Harmony zenith work site by means of the Robotics Officer (ROBO) in Mission Control. An Extravehicular Activity (EVA) by Hague and Morgan will then occur in mid-August to install IDA-3 onto its permanent home. CRS-18 will remain berthed at the station until at least 19-20 August.
“The latest timeline doesn’t show an exact extraction date but it is looking most likely that they will extract theIDA one day prior to the EVA and just position it overnight a few feet away from PMA-3,” Mr. Huot told AmericaSpace. “All IDA-3 extraction and maneuvering will be ground controlled.” This will follow a similar process as was achieved in August 2016 during the IDA-2 installation campaign.