CRS-20 – Final Dragon 1 arrives at the ISS
Following its ride on a SpaceX Falcon 9 rocket on Friday, the company’s CRS-20 Dragon cargo spacecraft arrived at the International Space Station on Monday. Liftoff from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida occurred at 11:50 pm Eastern time (04:50 UTC), prior to berthing at the ISS early on Monday.
This launch began the month-long CRS-20 mission, which will see the Dragon spacecraft deliver more than 4,300 pounds (1,950 kilograms) of supplies and science to the space station before returning to Earth with the results of multiple scientific experiments conducted, along with some surplus hardware.
The CRS-20 mission is being flown as part of NASA’s Commercial Resupply Services (CRS) program, which uses commercially-built vehicles to deliver cargo to the International Space Station. SpaceX was awarded a contract for twelve initial CRS missions in 2008, with a later extension increasing the number of flights to twenty.
The first iteration of SpaceX’s Dragon has successfully flown twenty missions to the ISS to date: a demonstration flight under NASA’s Commercial Orbital Transportation Services (COTS) program, and nineteen operational CRS flights. The CRS-7 mission, which launched in June 2015, failed to reach the station after its Falcon 9 launcher disintegrated on ascent.
CRS-20 is the last flight of the first-generation Dragon spacecraft, with the cargo version of the upgraded Dragon 2 spacecraft expected to take over services next year as part of Phase 2 of the CRS program, also known as CRS2.
Artistic render of Dragon 2 approaching the ISS for docking – credit: Nathan Koga for NSF/L2
New contracts for the CRS2 program were announced in 2016, with SpaceX’s Dragon and Northrop Grumman’s Cygnus spacecraft selected to continue delivering cargo to the station. Sierra Nevada Corporation’s Dream Chaser spaceplane was added to the program to provide additional services.
The first version of Dragon is equipped to carry both pressurized and unpressurized cargo to the International Space Station – the former within the recoverable capsule and the latter being housed in the spacecraft’s aft trunk section. Dragon provides a unique capability to return cargo and hardware to Earth, whereas all other uncrewed cargo delivery spacecraft currently servicing the station are not built to withstand reentry. Only the pressurized capsule is recovered during CRS missions (Dragon’s trunk will be destroyed when it reenters Earth’s atmosphere at mission end).
The Dragon capsule was also designed to be reusable, and can be reused for up to three missions. CRS-20 will mark the third flight for spacecraft C112, which flew to the International Space Station in February 2017 and December 2018 as part of the CRS-10 and CRS-16 missions.
Dragon C112 approaches the ISS during the CRS-10 mission – credit: NASA
This mission also marks the fastest turnaround time for a Dragon capsule since its last flight, with only 14 months between C112’s second splashdown in January 2019 and its third launch.
In total, the CRS-20 Dragon vehicle carries 4,358 pounds (1,977 kilograms) to the International Space Station, with 3,326 pounds (1,509 kilograms) being transported in the pressurized capsule. This includes 602 pounds (273 kilograms) of crew supplies, 123 pounds (53 kilograms) of equipment required to support future spacewalks, 483 pounds (219 kilograms) of vehicle hardware, a single kilogram of computer equipment, and 2,116 pounds (960 kilograms) of scientific experiments.
Dragon’s unpressurized trunk contains the Bartolomeo research platform, which was developed by Airbus Defense and Space and will be operated with the support of the European Space Agency (ESA). Bartolomeo will be mounted on the forward-facing side of the European Columbus module, and will offer thirteen payload sites – twelve being active and one remaining passive – to host external commercial scientific payloads and experiments.
About to be launch on March, 6th, with @NASA’s CRS-20 mission, #Bartolomeo will provide exceptional information about the Earth.
Stay tuned to follow the launch in the Dragon #ISS cargo supply vehicle. pic.twitter.com/qM3st8JNUC
Eight of these active payload sites, along with the passive site, are provided through interfaces that are directly mounted on the Bartolomeo platform, while the four additional active sites are provided in a chain-link configuration. These sites also have the capability to combine two external payloads into one double payload. Bartolomeo’s avionics system is able to provide power and data management, payload commanding, flight environment determination functions, and temporary data storage to multiple payloads that will be installed on the platform.
The CRS-20 Dragon’s ride to space was the workhorse two-stage Falcon 9 rocket, which utilized a flight-proven first stage. The booster itself, B1059.2, previously supported the launch of the CRS-19 Dragon spacecraft to the International Space Station in December 2019.
The booster landed on the autonomous spaceport droneship Of Course I Still Love You, which was stationed 213 miles (343 kilometers, 185 nautical miles) off the coast of Florida. The use of the droneship for the CRS-19 mission, rather than utilizing a return-to-launch-site (RTLS) landing profile with a touchdown at Cape Canaveral’s Landing Zone 1 (LZ-1), was chosen because of SpaceX’s decision to perform additional thermal tests on Falcon 9’s second stage after spacecraft separation.
Following its successful landing on Of Course I Still Love You, the first stage was transported back to Cape Canaveral, where it underwent refurbishment. SpaceX conducted a static fire test of this booster at Space Launch Complex 40 on Sunday, March 1st, as is customary for all Falcon 9 missions.
The booster was then rolled back into the Horizontal Integration Facility (HIF) at SLC-40, where the CRS-20 Dragon spacecraft and its payloads were integrated. The entire stack was then rolled out to the pad and lifted vertical ahead of its launch at 11:50 pm local time on Friday (04:50 UTC on Saturday).
The countdown on launch day officially commenced when SpaceX began loading supercooled, densified RP-1 fuel into both stages of the Falcon 9 rocket at T-35 minutes before liftoff. First stage liquid oxygen (LOX) loading also got underway at this time.
Liquid oxygen loading on the second stage began at the T-16 minute mark. Both stages continued to be topped off until the final minutes of the countdown, replacing any liquid oxygen that is boiled off and vented from the launcher.
The Falcon 9 rocket and the Dragon spacecraft transitioned to internal power – in which both vehicles began to use internal battery power rather than using pad connections – in the last ten minutes before launch. The strongback (the structure that supports Falcon 9 and Dragon during the countdown) began to rotate about 1.5 degrees away from the rocket at the T-4 minute and 30 second mark, and remained in that position until liftoff.
Absolutely unreal sunset lighting for remote setup at SLC-40 this evening. SpaceX is poised to launch the final first gen Cargo Dragon tonight at 11:50 pm est. on a resupply mission to the ISS. I placed two cameras at the launch pad, cross your fingers they work! @NASASpaceflight pic.twitter.com/7es5NxZZbH
At T-60 seconds before launch, Falcon 9 ensured startup mode, in which the rocket’s onboard computers took over control of the countdown and began conducting final checks on all systems before flight. Falcon 9’s tanks were also brought up to flight pressure at this point. SpaceX’s Launch Director then gave a “go” for launch at T-45 seconds.
At the T-3 second mark, Falcon 9’s nine Merlin-1D first stage engines ignited, with liftoff occurring at T-0 following a quick check to ensure that the engines are performing as expected.
Falcon 9 passed through the area of maximum aerodynamic pressure, or “Max-Q”, at T+1 minute and 18 seconds into the flight. This is the point during launch where the vehicle experiences the highest levels of stress due to aerodynamic conditions.
Meanwhile, Falcon 9’s first stage engines continued to burn up until the T+2 minute and 18 second mark, where all nine engines shut down simultaneously in an event known as Main Engine Cutoff, or MECO.
The second stage separated from the first stage four seconds later, with the Merlin Vacuum engine igniting at T+2 minutes and 29 seconds.
After separation, core B1059.2 fliped itself around and performed a short burn – a boostback burn – to propel itself back towards Cape Canaveral for a return-to-launch-site landing at Landing Zone 1. Following the completion of this burn, the titanium grid fins used to control the booster though descent deployed.
At about 6 minutes and 32 seconds into the flight, B1059.2 once again ignited its engines to conduct its entry burn, which is done to reduce velocity and limit heating as it passes through the denser regions of the atmosphere.
Once this burn was complete, the booster continued to descend towards Landing Zone 1, with the final landing burn and touchdown taking place just over eight minutes after liftoff.
Falcon 9 B1059.2 has landed at LZ-1.
That’s SpaceX’s 50th landing! Congrats to all concerned! pic.twitter.com/Iu1g837ycW
Meanwhile, Falcon 9’s second stage continued to carry Dragon to orbit. The Merlin Vacuum engine burned for six minutes and six seconds, with Second Engine Cutoff (SECO) occurring at the T+8 minute and 35 second mark.
One minute after SECO, the Dragon spacecraft separated from the second stage and began its mission. Dragon’s solar arrays, which are mounted on the unpressurized trunk section, deployed at just over 12 minutes into the flight. The spacecraft’s Guidance, Navigation and Control (GNC) bay door opened at T+2 hours and 19 minutes, enabling data downlink and uplink from SpaceX Mission Control in Hawthorne, California.
In the days following launch, Dragon performed a series of maneuvers to prepare for a rendezvous with the International Space Station on Monday morning. Upon arrival at the orbiting outpost, the spacecraft was grappled by the station’s Canadarm2 robotic arm and berthed to the nadir – or Earth-facing – port of the US Harmony module.
Canadarm2 prepares to grapple Dragon C112 as part of the CRS-16 mission – credit: NASA
NASA astronaut Jessica Meir performed the capture operation, with fellow NASA astronaut Drew Morgan assisting. While berthed at the station, Dragon’s pressurized cargo will be unloaded and then loaded with returning hardware, including several rodent research habitats.
Dragon is expected to remain at the International Space Station until April, at which point it will be unberthed using Canadarm2 and released. The spacecraft will then depart the vicinity of the station and deorbit itself, separating its trunk section before reentering and splashing down in the Pacific Ocean under its parachutes.
The CRS-20 mission was the fifth of the year for SpaceX, with four of them being orbital launches. The lone exception was the in-flight abort test of the company’s Crew Dragon spacecraft, which took place in January. This test was done in preparation for the first crewed Crew Dragon demonstration flight to and from the International Space Station, known as Demo-2 or DM-2. SpaceX and NASA are currently working towards a launch no earlier than May of this year.
The company’s next launch is slated for no earlier than March 14, with a Falcon 9 lofting another batch of Starlink satellites to low Earth orbit from Launch Complex 39A at Florida’s Kennedy Space Center. Another Falcon 9 is scheduled to launch the CONAE-built SAOCOM-1B spacecraft on a polar trajectory from Cape Canaveral’s SLC-40 at the end of the month.
SpaceX’s first mission for the CRS2 program, CRS-21, is currently scheduled for late October, with Northrop Grumman launching a Cygnus mission ahead of it in early August.