CRS-10 Dragon completes homecoming to conclude successful ISS mission

by Chris Bergin

The latest SpaceX Dragon spacecraft concluded her mission to the International Space Station (ISS). Unberthing of the CRS-10 Dragon from the orbital outpost on Sunday began the critical End Of Mission (EOM) milestones, which was marked with a successful splashdown in the Pacific Ocean.


The CRS-10 Dragon was launched by SpaceX’s Falcon 9 carrier rocket on a hugely important mission, marking the company’s first Commercial Resupply Services (CRS) mission from Pad 39A.

The previous CRS missions launched from SLC-40. However, following the loss of the Falcon 9 that was set to loft the AMOS-6 satellite, which resulted in severe damage to that pad, SpaceX pressed forward with their conversion of the historic LC-39A at the Kennedy Space Center (KSC), with the CRS-10 Dragon mission marking the debut SpaceX Dragon launch from the former Apollo and Shuttle pad.

The launch was a success, with Dragon pushed towards a Low Earth Orbit destination. At the same time, the Falcon 9 booster returned home for a landing at Cape Canaveral’s LZ-1.

Dragon completed her chase of the Station a few days after launch, berthed via a collaboration of robotics and humans, as  ISS Commander Shame Kimbrough and Flight Engineer Thomas Pesquet – working in the Robotic Work Station in the Cupola lab – grabbed the Dragon via the use of the End Effector on the Space Station Remote Manipulator System (SSRMS).

The successful berthing marked the delivery of 2,490 kilograms, or 5,490 pounds, of cargo. This included 1,530 kilograms (3,373 lb) of pressurized cargo and 960 kg (2,116 lb) of unpressurized cargo in the Trunk.

The pressurised cargo included 732 kilograms (1,614 lb) of scientific hardware and experiments, 296 kilograms (653 lb) of provisions for the crew, 382 kilograms (842 lb) of hardware for the US segment of the station and 22 kilograms (49 lb) for the Russian segment, 11 kilograms (24 lb) of computer equipment and 10 kilograms of hardware to support extravehicular activity (EVA) at the station.

The unpressurized cargo included NASA’s Stratospheric Aerosol and Gas Experiment III, or SAGE III-ISS. SAGE III-ISS will monitor ozone, aerosol and trace gas levels in Earth’s stratosphere, by observing the refraction of sunlight and moonlight through the atmosphere.

It, along with the Lightning Image Sensor (LIS), or STP-H5 – were mounted externally to the space station during the berthed phase on the mission.

Aided by the Canadian robot, Dextre, the installations were followed by the reloading of numerous items for return and disposal. Dextre’s task was to install packages such as MISSE and the RRM payloads into the trunk of Dragon, which will be destroyed when the trunk is seperated during Dragon’s return to Earth.

Thousands of pounds of return items were also installed into the pressurized section of Dragon, including a long list of experiments that will be removed from Dragon once she is back on Earth.

To kick off the homecoming, the long sequence of events – that ultimately leads to Dragon safely bobbing the Pacific Ocean – start with the unberthing of Dragon from the Node 2 Nadir CBM came via the release of 16 bolts around the CBM berthing collar on the ISS side, performed in four sets of four bolts to ensure even unloading on the CBM interface.

Dragon was then pulled away from the ISS via the use of the SSRMS.

Dragon was maneuvered to the release position approximately 30 feet below the ISS. She was left in this position for the night – known as the parking position.

Sunday’s ops began with Dragon in the release position, ahead of the time for Dragon and the ISS to part ways.

Via a squeeze of the trigger on the Rotational Hand Controller (RHC) on the RWS to release the snares holding the SSRMS Latching End Effector (LEE) to the Dragon Flight Releasable Grapple Fixture (FRGF), the operation effectively “let go” of Dragon.

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This occurred at 05:11 Eastern – although the timing was subject to variation, based on communications and lighting conditions.

With the SSRMS retracted safely clear, Dragon conducted three departure burn to depart to the vicinity of the ISS, edging away from the orbital outpost, with small thruster firings to push down the R-Bar.

The larger of the three burns was conducted to send Dragon outside of the approach ellipsoid, at which point SpaceX controllers in MCC-X took full control of the mission.

Following the completion of departure burns, Dragon conducted a free-flying phase on-orbit for just under five hours, during which time she will completed a critical action – the closure of the GNC bay door, to which the FRGF is mounted – before conducting a de-orbit burn at around 10 am Eastern.

The 10 minute deorbit burn was carried out by the spacecraft’s Draco thrusters.

The umbilical between Dragon and its Trunk was disengaged, prior to the Trunk separating from the Dragon capsule. The trunk was destroyed by Entry Interface (EI), along with the payloads set for disposal.

As the spacecraft entered EI she was protected by her PICA-X heat shield – a Thermal Protection System (TPS) based on a proprietary variant of NASA’s phenolic impregnated carbon ablator (PICA) material – designed to protect the capsule during Earth atmospheric re-entry, and is even robust to protect Dragon from the high return velocities from Lunar and Martian destinations.

Once at the required velocity and altitude, Dragon’s drogue parachutes were deployed, followed by Dragon’s main parachutes, easing the vehicle to a splashdown in the Pacific Ocean off the coast of California at around 10:46 am Eastern.

Three main recovery boats then arrived on station, with fast boats racing to meet the Dragon shortly after she hit the water, allowing for the recovery procedures to begin. The vehicle was powered down and then hooked up to the recovery assets.

Dragon was transported to the port of Los Angeles, prior to a trip to Texas for cargo removal.

The cargo return – otherwise known as the downmass capability – is one of Dragon’s star roles following the retirement of the Shuttle fleet. No other Visiting Vehicle to the ISS is capable of the downmass provided by Dragon.

(Images: NASA, SpaceX, and L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)

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