A major external payload to conduct laser-ranging observations of Earth’s forests, an investigation into muscle abnormalities in microgravity, first-time testing of liquid methane storage and transfer technologies and other experiments are among the cargo on SpaceX’s CRS-16 Dragon mission to the International Space Station (ISS), launched at 1:16 p.m. EST today (Wednesday, 5 December), from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla. Launch was postponed 24 hours from Tuesday, reportedly after mold was identified on food bars for an on-board rodent experiment.
CRS-16 becomes the first Dragon to fly atop a Block 5 variant of the Upgraded Falcon 9—a vehicle characterized by enhanced thrust on its Merlin 1D+ engine suite, strengthened landing legs to accommodate oceanic or ground touchdowns and better flight control systems—and will now follow a two-day rendezvous profile to reach the space station this weekend.
The primary payload—housed in Dragon’s unpressurized trunk for ascent—is the Global Ecosystem Dynamics Investigation (GEDI), jointly developed by the University of Maryland at College Park and NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Md. After arrival at the station, GEDI will be robotically extracted from Dragon’s trunk and installed onto Site 6 on the Exposed Facility (EF) of Japan’s Kibo lab. “Trunk robotics operations will only take about five days,” Mr. Huot explained. “One day of setup for each external payload and three days of payload transfer ops.”
GEDI will utilize lidar instrumentation to observe Earth’s tropical and temperate forests in high resolution and across three dimensions, in order to better comprehend important carbon and water-cycling processes, biodiversity and habitat. In doing so, GEDI is expected to harvest the first-ever high-resolution imagery of forest vertical structure on a global scale, quantifying above-ground carbon storage in vegetation and changes resulting from vegetation disturbance/recovery, as well as the potential for forests to sequester carbon in the future and the impact of changes in terrestrial forests on habitats and biodiversity.
It follows in the footsteps of the Global Laser Altimeter System (GLAS) from NASA’s 2003-launched ICESat mission, with which it shares a 1064-nanometer lidar capability, but GEDI’s three lasers will produce eight ground-tracks, achieving a narrower-resolution “footprint”—just 80 feet (25 meters), as opposed to over 210 feet (65 meters) for GLAS—which affords it improved accuracy in its measurements, particularly in areas of sloping terrain or dense canopy cover. It is expected that GEDI will make around ten billion cloud-free observations during its two years of near-continuous operations.
Another experiment aims to grow large crystals of Human Manganese Superoxide Dismutase (MnSOD), to assess the importance of this antioxidant protein in protecting humans from oxidizing radiation and oxidizers produced by the body. MnSOD rids harmful superoxide from the mitochondria of human cells and, in doing so, plays a key role in limiting major health problems like cancer, neurological degeneration and heart disease.
Also aboard CRS-16 is NASA’s third Robotic Refueling Mission (RRM3), which will include the first-ever demonstration of storage and transfer of 9.2 gallons (42 liters) of liquid methane in space. It incorporates “source” and “receiver” tanks, together with various transfer lines, and its operations will be conducted by the station’s Dextre robot.
All told, Mr. Huot noted that CRS-16’s total payload amounts to 5,673 pounds (2,573 kg), two-thirds of which is pressurized cargo, including crew supplies, science investigations, Extravehicular Activity (EVA) tools, vehicle and computer hardware and equipment for the station’s Russian segment.
Passing the point of maximum aerodynamic turbulence (colloquially dubbed “Max Q”) at 70 seconds into the flight, the booster later throttled back two of the Merlins to reduce the rate of acceleration at Main Engine Cutoff (MECO). Two and a half minutes after launch, the seven remaining Merlins fell silent and the first stage separated from the stack.
It was now the turn of the second stage, equipped with a single, restartable Merlin 1D+ Vacuum engine, capable of 210,000 pounds (92,250 kg). This now picked up the baton to deliver its payload into low-Earth orbit. During its burn, the protective nose fairing—covering Dragon’s berthing mechanism—was jettisoned and the spacecraft separated from the second stage a little under ten minutes after launch. Shortly thereafter, its pair of power-generating solar arrays were deployed. By 2.5 hours into the flight, Dragon’s Guidance and Navigation Control (GNC) Bay Door was opened to expose critical rendezvous sensors, ahead of the two-day journey to the ISS.
Meanwhile, SpaceX also aimed for a secondary objective to land their Falcon 9 rocket’s first stage back on land shortly after launch, and while the rocket missed Landing Zone (LZ)-1, the rocket did manage to compensate for whatever malfunction happened and kept the rocket offshore, making a soft-landing in the water and remaining in-tact as it tipped over.
“Grid fin hydraulic pump stalled, so Falcon landed just out to sea,” said Elon Musk on Twitter. “Appears to be undamaged & is transmitting data. Recovery ship dispatched. Engines stabilized rocket spin just in time, enabling an in-tact landing.”
The rocket, which landed probably only a couple thousand feet offshore (despite Hans saying he believes it was 2 miles), automatically targeted a landing point in the water to keep the surrounding Cape safe. “We have a safety function onboard to make sure the rocket avoids land if anything onboard goes wrong,” said Hans Koenigsmann, SpaceX Vice President of Mission Assurance. “As much as we are disappointed, it shows that the system knows how to recover from certain malfunctions.”
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon. pic.twitter.com/O3h8eCgGJ7
— Elon Musk (@elonmusk) December 5, 2018
“There is no public safety or health risks posed,” noted the U.S. Air Force 45th Space Wing, who secures the range for every mission flying off the Cape.
As with its predecessors, CRS-16 will approach the space station along the “R-Bar” (or “Earth Radius Vector”), which provides an imaginary line from Earth’s center, effectively approaching from “below”. In so doing, Dragon will take advantage of natural gravitational forces to brake its final approach and reduce the need to perform excessive numbers of thruster firings.
Rendezvous and capture are expected on Saturday morning. Dragon will remain attached to the space station until early January, before returning back to Earth with several thousand more pounds of science coming home from the ISS.