Following a successful launch early Saturday morning, SpaceX’s Crew Dragon spacecraft has successfully conducted a rendezvous and docking to the International Space Station for the first time. Docking was ahead of schedule at 5:51 AM EST (10:51 UTC) on Sunday, March 3.
A Falcon 9 Block 5 rocket lofted Dragon to orbit from LC-39A at NASA’s Kennedy Space Center in Florida, kicking off the first orbital test flight of NASA’s Commercial Crew program.
The Demo-1 mission marks the first flight of the new and improved Dragon 2 spacecraft, which is longer and more massive than its Dragon 1 predecessor.
Furthermore, the crew variant of Dragon 2 is one of two spacecraft that will return domestic crew launch capability to the United States, the other being Boeing’s CST-100 Starliner.
In order to certify Crew Dragon to carry humans, NASA and SpaceX will complete a series of four test flights, of which Demo-1 is the second. Following a successful pad abort test in 2015, the objective of Demo-1 is to demonstrate nominal end-to-end performance of Crew Dragon and its launcher, Falcon 9.
This includes demonstrating the on-orbit operation of avionics, communications, telemetry, life support, electrical, and propulsion systems, as well as the guidance, navigation, control (GNC) systems aboard both Falcon 9 and Dragon. GNC system performance must be demonstrated during ascent, on-orbit operations, and reentry.
The first two post-launch milestones for Crew Dragon were successfully completed shortly separating from Falcon 9’s second stage, as confirmed by SpaceX CEO Elon Musk during a post-launch press conference Saturday morning.
The nosecone of Dragon opened to reveal the docking port and forward-facing Draco thrusters, and the first of a series of burns to gradually match the ISS’s orbit was completed. Musk also confirmed that Dragon’s solar panels and electrical systems were operating nominally.
Dragon 2 was the first SpaceX vehicle to attempt an autonomous docking in orbit. Dragon 1, which has been flying cargo resupply missions to the ISS since 2012, only maneuvered close enough to be grappled by the station’s robotic arm, which then moved the spacecraft into position to be berthed.
Dragon 2, on the other hand, will not utilize the robotic arm, but rather use the onboard Draco thrusters to dock with the station. During a crewed mission, astronauts aboard the spacecraft will have the capability to intervene and fly the vehicle manually, if needed.
Crew Dragon docked to the forward port of the space station’s Harmony module, which has been fitted with an International Docking Adaptor (IDA). The IDA was launched aboard Dragon 1 on the SpaceX CRS-9 mission. Crew currently aboard the ISS completed a checkout of the docking port in advance of Saturday’s launch, and verified the docking system was “go” for docking.
During the rendezvous, Dragon went through numerous milestones, first coming into view at around 3,000 meters out, before approaching towards the Approach Elipsode and arrive at Waypoint 0.
With permission to enter the Keep Out Sphere (KOS), Dragon approached to within 150 meters of the docking port, where the station’s crew tested a retreat command at Waypoint 1.
Sending this command to the spacecraft moved Dragon back to 180 meters. After remaining in this position for approximately 10 minutes, Dragon was cleared to proceed to 20 meters for another brief hold, at Waypoint 2, followed by the historic docking to the ISS at 5:51 AM Eastern.
— Michael Baylor (@MichaelBaylor_) March 3, 2019
A single action item concerning Dragon’s approach to the station was identified during the Flight Readiness Review (FRR) conducted before launch.
A concern over Dragon’s docking abort procedures was raised by the Russian space agency Roscosmos, one of NASA’s international partners in the ISS program. While a scenario in which this issue would arise is unlikely, NASA and Roscosmos agreed to additional procedures to follow should Dragon encounter a problem during the rendezvous. No issues were suffered during the test objectives.
Also of interest over the course of Dragon’s mission will be the performance of the Draco thrusters used to maneuver in orbit. Thermal vacuum testing conducted last year revealed less than nominal performance within the full thermal environment the Draco thrusters were expected to experience during the Demo-1 mission.
As a result, NASA and SpaceX modified the mission design to constrain the thermal environment and ensure the thrusters would be ready for flight. Lessons learned, including the addition of heaters to the thrusters’ fuel lines, will allow the removal of those thermal constraints for the Demo-2 mission.
After docking to the station, Dragon’s hatch was opened, and the station crew boarded the spacecraft to perform inspections. Aboard Dragon is Ripley, a mannequin fitted with instruments to gather data during the flight, along with 181 kg of supplies and equipment.
Dragon will spend four days docked to the ISS, after which Dragon will return to Earth with science samples as well as a failed spacesuit part needing repair. During operational crew missions, Dragon will be able to carry approximately 50 kg of cargo to and from the station, in addition to the crew.
Dragon’s hatch is set to be closed at 12:25 PM EST (17:25 UTC) on Thursday, March 7. The following morning at 2:31 AM EST (07:31 UTC), Dragon will autonomously undock from the Harmony module and maneuver away from the station.
The deorbit burn, which will last up to 15 minutes, will begin at 7:50 AM EST (12:50 UTC). Like its Dragon 1 predecessor, the Dragon 2 capsule will separate from the spacecraft’s trunk prior to reentry.
Unlike Cargo Dragon, Crew Dragon will splash down via four parachutes in the Atlantic Ocean off of the coast of Florida, whereas Cargo Dragon has always landed in the Pacific. Splashdown is scheduled for 8:45 AM EST (13:45 UTC) on Friday, March 8.