SpaceX’s Dragon spacecraft has concluded her mission to the International Space Station (ISS) with a successful return to Earth on Sunday. The EOM (End Of Mission) events began with the successful unberthing and release of the CRS-3/SpX-3 spacecraft from the orbital outpost, ahead of a parachute-assisted splashdown in the Pacific Ocean at around 3:05pm Eastern.
CRS-3 Dragon – EOM:
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Launched on April 18 atop of SpaceX’s Falcon 9 v1.1 launch vehicle, Dragon has enjoyed a successful stay at the ISS.
This was the fourth time the commercial vehicle – that has aspirations of becoming crew-rated – had paid a visit to the Station.
Grabbed by the tail by Canada’s Space Station Remote Manipulator System (SSRMS), Dragon was carefully translated towards her orbital on the Earth facing port of the Harmony module.
(Animation created by Artyom Zharov, via L2′s huge collection of CRS-3 arrival hi res images)
Riding uphill with the Dragon was a cargo compliment of 476 kilograms (1,050 pounds) of supplies for the crew, 715 kg (1,600 lb) of equipment for scientific research, 204 kg (450 lb) of replacement parts and hardware for the space station, 123 kg (270 lb) of equipment for conducting extra-vehicular activities, 600 grams (1.3 lb) of computer equipment.
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The ISS crew removed and stored the cargo, before refilling Dragon with downmass, including that will be removed once Dragon has been brought back to port. Dragon is the only American vehicle capable of returning downmass since the retirement of the Space Shuttle fleet.
She also provided the Station with two new payloads that were located in her Trunk section.
This included the High Definition Earth Viewing (HDEV) package – which is comprised of four high-definition cameras to be placed on the Station’s exterior for use in streaming live video of Earth for online viewing, along with the OPALS payload – which aims to demonstrate free-space optical communications technology.
Removing these payloads from the Dragon’s Trunk is the responsibility of Canada’s amazing space robot, Dextre (SPDM).
To kick off the homecoming, the long sequence of events that will ultimately lead to Dragon safely bobbing the Pacific Ocean began with the unberthing of Dragon from the Node 2 Nadir CBM, 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.
One of these bolts proved to be troublesome during berthing and has since been replaced.
Dragon will be under the firm grip of the SSRMS, which arrived back in the location of the spacecraft, following its role with Dextre and the Trunk payload removal tasks.
“Space Station Remote Manipulator System (SSRMS) Walk-off: Ground teams relocated the SSRMS from the Mobile Base System (MBS) to Node 2,” noted L2 ISS Status Updates.
“A series of walk-offs is required to arrive at the Node. The SSRMS was based on the MBS Payload Data Grapple Fixture (PDGF) 4. The first walk-off was to MBS PDGF1, then to the Lab PDGF.
“The final walk-off was to the Node 2 PDGF. The relocation is in preparation for SpaceX 3 release.”
With the SSRMS holding on to the Dragon – and the bolts released through the opposite process that saw first and second stage capture – the ISS crew used the “big arm” to pull Dragon away from the port, controlled from the Robotic Workstation (RWS) in the panoramic-viewed Cupola.
Dragon was then maneuvered to the release position approximately 30 feet below the ISS.
Once in the release position, the time came for Dragon and the ISS to part ways, via a squeeze of the trigger on the Rotational Hand Controller (RHC) on the RWS.
This was initiated by the release of the snares holding the SSRMS Latching End Effector (LEE) to the Dragon Flight Releasable Grapple Fixture (FRGF) – effectively “letting go” of Dragon.
This process concluded with a 09:26 Eastern release of SpaceX’s Dragon.
With the SSRMS retracted safely clear of the spacecraft, Dragon then conducted three departure burns to depart to vicinity of the ISS, edging away from the orbital outpost, with small thruster firings to push down the R-Bar.
This departure towards the edge of the ISS’ neighborhood was monitored by the COTS UHF Communication Unit (CUCU) Crew Command Panel (CCP), which was successfully checked out last week ahead of departure.
The third burn was the larger of the thread, which was successfully conducted to send Dragon outside of the approach ellipsoid, at which point SpaceX controllers inside MCC-X at SpaceX’s Californian facility took full control of the mission.
Dragon then enjoyed a free-flying phase on-orbit for around five hours, during which time she completed a critical action – closure of the GNC bay door, to which the FRGF is mounted – before conducting a de-orbit burn at 2:12 Eastern.
The 10 minute deorbit burn was conducted by the spacecraft’s Draco thrusters, although SpaceX then decided they wouldn’t provide any updates. However, the burn was later confirmed as successful via sources and eventually by SpaceX.
The umbilical between Dragon and its Trunk then disengaged, prior to the Trunk separating from the Dragon capsule.
As the spacecraft entered Entry Interface (EI) she was protected by the 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 was deployed, followed by Dragon’s main parachutes, easing the vehicle to a splashdown in the Pacific Ocean off the coast of California at around 3:05pm Eastern.
Three main recovery boats soon 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 recover assets.
Dragon was then transported to the port of Los Angeles, prior to a trip to Texas for cargo removal.
(Images: via L2′s SpaceX Special Section, which includes over 1,000 unreleased hi res images from Dragon’s four flights to the ISS. Other images via NASA and SpaceX)
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