SpaceX stands ready to launch its fourth Dragon cargo mission of 2017 to the International Space Station (ISS) at 10:35 a.m. EST Friday, 15 December, marking the first use of Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., in more than a year. The pad has been out of service since the Amos-6 explosion in September 2016 and its return to operational use is expected to free up historic Pad 39A at the neighboring Kennedy Space Center (KSC) for the long-awaited maiden voyage of the Falcon Heavy booster.
Meanwhile, at the space station, the incumbent Expedition 53 crew bade farewell to Orbital ATK’s OA-8 Cygnus cargo ship on Tuesday, 5 December, as U.S. astronaut Randy Bresnik, Russian cosmonaut Sergei Ryazansky and Italy’s Paolo Nespoli prepare for their own return to Earth next week.
Video Credit: Jeff Seibert/AmericaSpace
Current plans call for the CRS-13 Dragon mission—flying under the Commercial Resupply Services contract, negotiated between SpaceX and NASA and signed back in December 2008—to launch no sooner than 10:35 a.m. EST Friday. Originally targeted for earlier this month, the launch date settled on Tuesday, 11 December, but was slipped by 24 hours to Wednesday, 12 December, in order “to allow for additional time for pre-launch ground systems checks”. This was followed by a SpaceX tweet late Tuesday, confirming a further delay until No Earlier Than (NET) Friday. “Taking additional time for the team to conduct full inspections and cleanings due to detection of particles in 2nd stage fuel system,” it was noted. “Now targeting CRS-13 launch from SLC-40 on Dec. 15. Next launch opportunity would be no earlier than late December.” According to NASA’s Rob Navias, in comments provided to AmericaSpace on Wednesday, any more slips past Friday will necessitate the launch to be rescheduled for the end of the month, due to solar beta-angle cutout constraints.
The two-stage Upgraded Falcon 9 will deliver Dragon into low-Earth orbit, inclined 51.6 degrees to the equator, where it will follow a two-day rendezvous profile to reach the space station on Sunday, 10 December. Capture of the cargo ship, via the station’s 57.7-foot-long (17.6-meter) Canadarm2 robotic manipulator, is expected early Thursday, with berthing at the Earth-facing (or “nadir”) port of the Harmony node about two hours later. At the controls of Canadarm2 will be Expedition 53 astronauts Mark Vande Hei and Joe Acaba, who also oversaw Tuesday’s unberthing of the OA-8 Cygnus.
Under the terms of the original CRS1 contracts, SpaceX was required to launch 12 Dragon cargo missions and transport upwards of 44,000 pounds (20,000 kg) of equipment and supplies to successive ISS crews. Early in 2015, three additional CRS1 missions were secured by NASA, followed by five more in mid-2016. These were designed to bridge the gap before the second-round CRS2 series of contracted missions. The CRS2 series will see SpaceX, Orbital ATK and Sierra Nevada Corp. each fly at least six more cargo missions apiece to keep the station operational between 2019 and 2024.
All told, CRS-13 will carry about 4,861.2 pounds (2,205 kg) of payload to the Expedition 53 crew. Around a quarter of this quantity will be devoted to crew supplies, with 1,567.5 pounds (711 kg) of science-related hardware, 416.7 pounds (189 kg) of vehicle hardware, 363.8 pounds (165 kg) of Extravehicular Activity (EVA) tools and a smaller amount of computer equipment.
Within Dragon’s pressurized cargo module, two core experiments are Plant Gravity Perception and the Biorasis Glucose Biosensor. The former will utilize the European Modular Cultivation System (EMCS) in the station’s Columbus lab to investigate plant responses to the microgravity environment. Specifically, Arabidopsis thaliana—a small Eurasian flowering plant, popular in studies of plant biology and genetics—will be used to explore how mutant plants which lack gravity-sensing statoliths still manage to show consistent responses to gravity. Meanwhile, the latter experiment seeks to evaluate the usefulness of a medically-implantable glucose biosensor, called Glucowizzard, for daily management of diabetes sufferers.
Two major unpressurized payloads are also accommodated within Dragon’s roomy “trunk” for the journey to orbit. The first is the Total and Spectral Solar Irradiance Sensor (TSIS), which will be robotically installed onto Flight Releasable Attachment Mechanism (FRAM) Site 5 of ExPRESS Logistics Carrier (ELC)-3, situated on the space-facing (or “zenith”) face of the station’s P-3 truss segment. Assuming that Dragon is berthed at the space station on Thursday, TSIS will be robotically extracted from the trunk on Friday, 15 December, and attached to ELC-3 on Sunday, 17 December. The TSIS instrument, developed by the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder, is charged with measuring total solar irradiance and solar spectral irradiance, thereby deriving parameters for Earth’s total energy input from the Sun and how our atmosphere responds to the changeability of our parent star. Knowledge of the magnitude and variability of solar irradiance is key to understanding Earth’s climate.
With solar irradiance data having been collected continuously for almost four decades, TSIS stands ready to continue a legacy whose benefits include an enhanced predictability of space weather events—including solar winds and geomagnetic storms—and their effect upon humans and satellites in orbit, as well as electrical power transmissions and radio communications on the ground.
The second trunk-carried payload aboard CRS-13 is the Space Debris Sensor (SDS), a calibrated impact measurement device to examine the Micrometeoroid Orbital Debris (MMOD) environment around the station for up to three years. The sensor will be mounted on the exterior of the Columbus lab and combines dual-layer thin films and a suite of measurement instruments to provide semi-real-time impact detection and recording capability. It can measure the time, speed, direction, size and density of impacting objects, greater than 50 nanometers in diameter. This data will enable updates to the NASA Orbital Debris Engineering Model for objects smaller than 0.04 inches (1 mm) near the altitude of the station and provide lessons to plan for a second-generation SDS. Assuming an on-time berthing of CRS-13, current plans call for the extraction of SDS from Dragon’s trunk and its installation onto the station to occur on Tuesday, 19 December. The instrument will reside at the Columbus Starboard Overhead Platform, an at-present-unused payloads site.
Current plans call for CRS-13 to remain berthed at the ISS until early in the New Year, with departure and splashdown anticipated on 13 January. The mission will launch atop a reused Upgraded Falcon 9 first stage—which last saw service to deliver CRS-11 into orbit in June 2017—and will also feature a reused Dragon, which previously journeyed to the station on CRS-6 in the late spring of 2015. If CRS-13 launches before the end of 2017, and completes its mission, it will be the fourth Dragon of the year. This will effectively double the number of fully successful Dragon missions ever achieved in a single calendar year for SpaceX. The Hawthorne, Calif.-based launch services provider has previously achieved no more than two fully successful Dragon missions in any single year to date. CRS-13 comes on the coattails of the highly successful CRS-10 in February 2017, CRS-11 in June and CRS-12 in August.
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