Swan song: Final SpaceX Block 4 Falcon 9 launches CRS-15 cargo mission
CAPE CANAVERAL, Fla — Clear weather and a Moonlit pre-dawn sky provided perfect conditions as SpaceX launched its final Block 4 Falcon 9 on its fifteenth cargo resupply mission to the International Space Station (ISS). The rocket lifted off at 5:42 a.m. EDT (09:42 GMT) from Space Launch Complex 40 (SLC-40).
If everything continues to go as it is planned, the CRS-15 Dragon spacecraft should deliver an estimated 5,900 pounds (2,676 kilograms) worth of supplies and equipment to low-Earth orbit (LEO), where it is scheduled to rendezvous with the ISS on July 2.
The mission, part of NASA’s Commercial Resupply Services (CRS) contract with SpaceX, saw the use of two flight-proven vehicles — the Falcon 9 rocket that launched NASA’s TESS spacecraft, and the Dragon capsule that was used for the CRS-9 mission in 2016. Only 10 weeks separated the TESS mission and the flight of CRS-15, highlighting how far SpaceX has come with their reusable technology.
Approximately three seconds prior to liftoff, the nine Merlin 1D engines ignited with a telltale green flash. The engines, which burn a mixture of liquid oxygen and a highly refined kerosene called RP-1, produce a combined 1.71 million pounds-force (7,600 kilonewtons) of sea-level thrust. This provided enough power to propel the rocket and the Dragon spacecraft off the pad. The vehicle cleared the tower shortly thereafter.
After gaining speed and altitude, the Falcon 9 began its gravity turn and assumed a northeasterly heading.
As the vehicle accelerated, the forces experienced by the rocket – atmospheric pressure combined with velocity, a condition known as maximum aerodynamic pressure (max Q) – reached their greatest at approximately 79 seconds into the flight.
The first stage’s nine Merlin 1D engines continued to power the vehicle for another 96 seconds, shutting down at 2 minutes and 45 seconds after it had left the launch pad far below. This was followed three seconds later by separation of the first and second stages.
Like most SpaceX launches carried out this year, the Falcon 9 rocket was deemed expendable and not reused. As such, the F9’s first stage was not recovered. Given this, there were no in-flight acrobatics from a returning booster orchestrating a series of flips and engine burns so that it could return safely for a ground landing or on an Autonomous Spaceport Drone Ship out in the Atlantic.
Shortly after stage separation, the second stage’s lone Merlin 1D-Vacuum (MVac) came to life. The vacuum-optimized engine – similar to the power plants on the first stage, but with a larger nozzle extension – continued to accelerate the stage and its payload with some 210,000 pounds-force (934 kilonewtons) of thrust.
The second stage continued accelerating the spacecraft and its cargo over the next 5 minutes and 35 seconds, with engine cutoff coming at 8 minutes and 31 seconds after liftoff. After a short coast phase, the Dragon spacecraft separated from the second stage and was flying freely, only nine and a half minutes after taking to the skies above SLC-40.
The first order of business for the Dragon is to deploy its twin solar panels to power the spacecraft and its systems. It will spend the next three days slowly raising its orbit as it rendezvous with the ISS, where it should be captured by the space station’s Canadarm2 robotic arm, which will be operated by NASA astronaut Ricky Arnold.
The CRS-15 mission marks SpaceX’s twelfth flight of 2018, with up to another sixteen on the launch manifest slated for the remainder of the year. The company’s next scheduled launch is the seventh Iridium NEXT mission, currently set for July 20, 2018.
When it arrives at the orbiting laboratory, it will have carried with it an array of science experiments including ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station – an effort to study how plants respond to changes in water availability.
“ECOSTRESS’ unique orbital perch aboard the space station will allow it to observe the same spot on Earth every few days at different times of day for at least a year, giving scientists the ability to track changes in plant water use over the course of a typical day,” said ECOSTRESS Principal Investigator Simon Hook of JPL. “Current polar-orbiting satellites can only provide a single snapshot of evapotranspiration each day, at the same time of day. The team is ready to receive our first science data, expected in early July.”
SpaceX was awarded an estimated $1.6 billion to carry out 12 resupply missions to the orbiting lab in 2008. Three additional missions were added to the Phase 1 contract of this program in 2015.
Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.