SpaceX’s CRS-1 Dragon arrives at the ISS for successful berthing

by Chris Bergin and William Graham

The first official commercial resupply mission to the International Space Station (ISS) successfully passed the critical phase of its arrival at the orbital outpost, as SpaceX’s CRS-1 Dragon was “tamed” by the Space Station Remote Manipulator System (SSRMS) ahead of schedule, at 6:56am Eastern. The vehicle was then successfully berthed to the Harmony module.

Dragon Berthing (milestones will be updated during the events):

Advancing from its tasks during the C2+ test objectives – that involved Dragon undertaking a lap around the Station to test communication assets – the private spacecraft was now qualified to arrive at the ISS on Flight Day 3 of its mission.

The spacecraft made a series of thruster burns, each taking it closer to the station; holding at distances of 2,500, 1,200, 250, 30 and 10 metres (2,735, 1,310, 273, 33 and 11 yards), before finally being grappled by the Canadarm2 Remote Manipulator System, and attached to the nadir port of the Harmony module.

Akihiko Hoshide operated Canadarm2 during capture, while Sunita Williams will later use it to berth the Dragon.

However, as always, Dragon was required to pass a series of “Go No/Go” points during its rendezvous, ensuring it provides no risk to the $100 billion Station.

The series finite manuevers began as Dragon caught up to the Station via the Height Adjustment (HA) and Co-Elliptical (CE) burn points, bringing Dragon 2.5 km below ISS. A Go/No-Go was performed for the HA3/CE2 burn pair bringing Dragon to 1.2 km below ISS.

The HA3/CE3 burn pair, using RGPS and configured with the ISS’ own GPS system, were then conducted, followed by the HA4 (Ai) burn, taking Dragon inside the corridor where the crew began to monitor the spacecraft’s approach.

With both SpaceX mission control in California, and NASA’s ISS Flight Control Room (FCR) in Houston monitoring, Dragon arrived and held at 250 meters distance from the Station, where checks of Dragon’s LIDAR system were successfully conducted, a key element of hardware that has a heritage of testing via the Space Shuttle Discovery during her STS-133 mission.

With all parties are satisfied with Dragon’s performance – and ability to abort if required – Dragon was given a “Go” to approach to 30 meters distance from the Station where it automatically paused.

At all points, the ability to abort could be made by controllers on the ground, the Dragon itself and the Expedition 33 crew – via the Commercial Orbital Transportation Services (COTS) Ultra High Frequency (UHF) Communication Unit, or CUCU, which rode in the middeck stowage locker on Atlantis during STS-129 late in 2009, before being handed over to ISS crewmembers ahead of the demonstration flights.

The CUCU provides a bi-directional, half-duplex communications link between Dragon and ISS using existing ISS UHF Space to Space Station Radio (SSSR) antennas, which provides a communication path between MCCX (SpaceX) and Dragon during proximity operations and a command security between ISS and Dragon.

“SpaceX1 Capture Preparations: The crew and ground controllers performed a checkout of the CUCU, the RWS (Robotic Work Station), and the SSRMS, in preparation for SpaceX1 capture. All checkouts went well and there were no problems,” noted L2 CRS-1 Status – LINK – in the days prior to Dragon’s launch.

Proceeding from 30m to the Capture Point at 10 meters out, Dragon automatically held position again, allowing the ISS’ robotic assets – already translated to the pre-capture position – to make the move towards the Dragon via controls in the Cupola RWS.

“MT Translation: The MT translated from worksite 5 to worksite 2, in preparation for SpaceX1 arrival. All MSS hardware is repowered, without any significant issues,” added the Status reports, showing the translation of the large ISS robotic assets for the grapple of Dragon upon arrival,

Upon receiving the “Go for Capture” call from Houston, the ISS crew armed the SSRMS capture command and begin tracking the vehicle through the camera on the Latching End Effector (LEE) of the SSRMS, noted an overview presentation (L2 – Link).

With the ISS’ thrusters inhibited and Dragon confirmed to be in free drift, the arm’s LEE maneuvered over the Grapple Fixture (GF) pin on Dragon to trigger the capture sequence ahead of pre-berthing maneuvers.

With the addition of several holds into the timeline, capture was confirmed at 6:56am Eastern.

The Dragon, secured by the SSRMS, was then carefully translated to the pre-install set-up position, 3.5 meters away from the Station’s module, allowing the crew to take camcorder and camera footage of the vehicle through the Node 2 windows.

This footage will be downlinked to the ground for engineers to evaluate the condition of the Dragon spacecraft (See raw download collection from C2+ mission in L2).

The SSRMS then maneuvered Dragon to the second pre-install position, at a distance of 1.5 meters out. Desats were inhibited prior to the maneuver of the Dragon into Common Berthing Module (CBM) interface to begin the securing of the spacecraft to the ISS.

A “Go” at this point was marked by all four Ready To Latch (RTL) indicators providing confirmation on the RWS panel.

As has been seen with other arrivals – and indeed new additions to the Station itself – Dragon was put through first stage capture tasks, allowing the SSRMS to go limp, ahead of second stage capture, officially marking Dragon’s berthing with the ISS.

With all of the ISS berthing milestones ahead of the pre-planned schedule, the ISS crew decided to open the hatch to the Dragon a day ahead of the timeline.

The Dragon spacecraft is carrying 905 kilograms (1995 lb) of cargo to the space station, consisting of 461.5 kilograms (1015 lb) of usable items.

The cargo includes 118 kilograms (260 lb) of supplies for the crew; including food and clothing; 117 kilograms (390 lb) of scientific equipment for NASA, the US National Laboratory, ESA and JAXA; 102 kilograms (225 lb) of spares and other station hardware; and 3.2 kilograms (7 lb) of computer equipment; mostly spare hard drives and CD cases.

The US scientific payloads include a General Laboratory Active Cryogenic ISS Experiment Refrigerator, or GLACIER, cryogenic experiment; the Fluids Integrated Rack (FIR); Commercial Generic Bioprocessing Apparatus Micro-6 (CGBA/Micro-6), a commercial biosciences payload studying fungi in the space environment and Capillary Flow Experiments 2 (CFE-2), a fluid dynamics experiment.

Hardware for the Alpha Magnetic Spectrometer (AMS), retrieval equipment for the MISSE-8 exposed experiment, and refrigeration bags, are also being carried.

The European Space Agency’s BioLab and Energy experiments are also being delivered by the SpaceX CRS-1 mission. BioLab will be used to perform biological research in the Columbus module, while Energy will study the station’s crew’s energy balance.

The Japan Aerospace Exploration Agency has included its Education Payload Operations 10 (EPO-10) payload, which will be used to record video of experiments aboard the station for educational purposes. Dragon is also carrying an experiment to study plant microtubules, and an ammonia test kit.

The Dragon spacecraft is scheduled to depart the International Space Station on 28 October; with the spacecraft being unberthed and released via Canadarm2. The spacecraft will perform a burn to depart the vicinity of the ISS, before closing its GNC bay and beginning its deorbit burn.

Once the deorbit is complete, the trunk module will be jettisoned, and the spacecraft will reenter the atmosphere. The trunk section is expected to disintegrate, while the capsule descends under parachute for a landing in the Pacific Ocean.

For its return to Earth, the capsule will be loaded with completed experiments and equipment no longer needed aboard the space station, including 74 kilograms (163 lb) of crew equipment, 393 kilograms (866 lb) of scientific equipment and samples, 253 kilograms (518 lb) of station hardware, 5 kilograms (11 lb) of computer equipment, 33 kilograms (68 lb) of spacesuit parts used by previous crews, and a 20 kilogram (44 lb) payload for Roskosmos.

(Images: via L2’s SpaceX Dragon Mission Special Section – Containing presentations, videos, images (Over 2,000MB in size), space industry member discussion and more. Additional imagery via SpaceX and NASA).

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