Following a 13-month hiatus in International Space Station (ISS) operations, SpaceX—the Hawthorne, Calif.-based launch services organization, headed by entrepreneur Elon Musk—secured its latest triumph Easter Sunday morning with the successful rendezvous, capture, and berthing of the snub-nosed Dragon spacecraft at the expansive orbital outpost. Expedition 39 Commander Koichi Wakata, assisted by Flight Engineers Rick Mastracchio and Steve Swanson, grappled the cargo vessel with the station’s 57.7-foot-long (17.4-meter) Canadarm2 robotic arm precisely on time at 7:14 a.m. EDT and installed it onto the Earth-facing (or “nadir”) port of the Harmony node. Completion of the two-stage capture and berthing operation was confirmed by NASA at 10:06 a.m. EDT. Dragon, which is flying the third of 12 dedicated missions under SpaceX’s $1.6 billion Commercial Resupply Services (CRS) contract with NASA, will remain attached to the ISS for about a month as its myriad payloads are unloaded. Today’s success also comes hard on the heels of SpaceX’s electrifying announcement of success in its effort to soft-land the first stage of the Falcon 9 v1.1 launch vehicle on water, by means of experimental landing legs.
The CRS-3 mission launched, against many odds, on Good Friday, four days later than originally planned due to a helium leak in the first stage of the Falcon 9. In spite of the risk of thunderstorms, thick clouds, and precipitation across the Cape Canaveral area, SpaceX “threaded the needle” through the inclement weather and accomplished an “instantaneous” liftoff at 3:25:22 p.m. EDT, successfully delivering Dragon on its long-awaited mission to deliver equipment and supplies to the space station. Within minutes of achieving orbit, SpaceX noted that the spacecraft had separated from the second stage of the Falcon and was in the process of deploying its electricity-generating solar arrays and communications and navigation appendages, preparatory to a berthing about 38 hours after liftoff.
Overnight Saturday, it was reported by SpaceX that Dragon conducted a series of thruster “burns” to bring itself closer to the space station, along the so-called “R-Bar” (or “Earth Radius Vector”), an imaginary line running from the center of Earth toward the ISS. By approaching its quarry from “below,” Dragon took advantage of natural gravitational forces to brake its final approach and limit the need for additional thruster burns. Similar R-Bar rendezvous profiles have been adopted since the Shuttle-Mir era in the 1990s.
To accomplish today’s capture and berthing at the Harmony node, Wakata, Mastracchio, and Swanson rose early, ate a quick Easter breakfast, and began setting up their laptops and other equipment in the space station’s multi-windowed cupola, which would afford them a panoramic view of the events to come. A carefully orchestrated symphony of maneuvers brought the cargo craft to a “Hold Point” about 1.5 miles (2.4 km) from the space station, where it passed a “Go/No-Go” poll to proceed. Further polls and holds were made at distances of 3,700 feet (1,130 meters) and 820 feet (250 meters), with the latter “Hold Point” being reached at 5:14 a.m. EDT, as both vehicles flew high above southern Africa.
Less than 20 minutes later, Dragon resumed its approach, keeping rigidly to the R-Bar path and creeping toward the ISS at a steady, slowpoke pace of less than 3 inches (7.6 cm) per second. Inside the cupola, Wakata, clad in a dark blue shirt, monitored the spacecraft’s approach via binoculars, as Mastracchio, in a green shirt, provided a running commentary of Dragon’s orientation for Capcom Jack Fischer in the Mission Control Center in Houston, Texas. The pair were quickly joined by a jubilant, red-shirted Swanson. Overseeing the berthing operation in Mission Control today was Flight Director Matt Abbott.
Passing within the so-called “Keep Out Sphere” (KOS)—a collision-avoidance exclusion zone, extending 650 feet (200 meters) around the ISS—Dragon’s rate of closure had by now slowed to a little under 2 inches (5 cm) per second. Just before 6:15 a.m. EDT, watched by the Expedition 39 crew and anxious Mission Control teams in Houston and Hawthorne, the spacecraft reached its next-to-last “Hold Point” at 100 feet (30 meters), where SpaceX controllers verified good navigational data and the polling of all stations began. By this point, the two spacecraft were flying through orbital darkness, high above Chile.
Shortly afterward, at about 6:50 a.m. EDT, clearance was given to advance to the 30 feet (10 meter) “Capture Point,” which would position Dragon within range of Canadarm2′s Latching End Effector (LEE). “Step away from the chocolate,” the Canadian Space Agency (CSA) tweeted its Easter-egg-munching followers, “and take a short break to watch #Canadarm2 catch #Dragon!” The arm is part of Canada’s contribution to the ISS and builds upon the heritage of the original “Canadarm,” the shuttle’s Remote Manipulator System (RMS), which supported dozens of missions and a wide variety of construction, retrieval, deployment, and repair tasks from 1981 until 2011. It was also noted that today’s capture of CRS-3 marked the 10th capture of a cargo craft by Canadarm2, which was installed aboard the space station in April 2001. Since September 2009, the arm has supported the capture and berthing of four H-II Transfer Vehicles (HTVs) on behalf of the Japan Aerospace Exploration Agency (JAXA), four Dragons—including the Commercial Orbital Transportation Services (COTS) Demo in May 2012 and three dedicated CRS missions—and two Cygnus resupply ships for Orbital Sciences Corp.
Later, CSA tweeted its own self-confessed “Bad Space Joke” of the day by encouraging Dragon to draw closer, telling it that “We’re waiting for you with open arm!” Adding to the humor, upcoming Expedition 40/41 resident Alexander Gerst of Germany—who will launch aboard Soyuz TMA-13M for his six-month “Blue Dot” mission on 28 May—also tweeted that half of his clothes, food, toothpaste, and running shoes were also aboard Dragon. His future crewmate, NASA astronaut Reid Wiseman, also later tweeted thanks to Wakata for bringing his food supply safely to the space station.
By 6:58 a.m. EDT, the extended Canadarm2 was within the 30 feet (10 meter) range of Dragon, and, following earlier niggling UHF communications dropouts, Jack Fischer radioed Wakata at 7:02 a.m. EDT with a “Go for Capture.” The official time at which Canadarm2′s LEE grappled the cargo craft was 7:14 a.m. EDT, a little under 40 hours since launch, as Dragon and the ISS flew high above Egypt’s River Nile. In announcing the successful capture, Wakata thanked both the NASA and SpaceX teams for their support and described Dragon and Canadarm2 as having been very stable during the final proximity operations. Jack Fischer replied that Wakata’s performance today demonstrated that his nickname of “The Man” was indeed an apt one.
Over the following 2.5 hours, the crew and Mission Control worked to maneuver Dragon toward its eventual berthing point on the nadir interface of the Harmony node. With astronaut Randy Bresnik now on the Capcom’s console, it was for him to convey the welcome news of Expedition 39′s Easter Sunday visitor: “The Easter Dragon,” he told the crew, “is knocking at the door.” The physical berthing took place in two parts, with Mastracchio overseeing first-stage capture, in which hooks from Harmony’s nadir Common Berthing Mechanism (CBM) extended and grabbed Dragon to pull their respective CBMs into contact. This was then followed by second-stage capture, in which a series of 16 bolts were driven to rigidize the two vehicles in a tight, mechanized embrace. Completion of second-stage capture was confirmed by NASA at 10:06 a.m. EDT as the spacecraft flew high above Brazil. Following berthing, the crew will be given a “Go” to pressurize the vestibule leading from the Harmony nadir hatch into Dragon and will then be able to access the cargo craft, which has delivered about 3,500 pounds (1,590 kg) of equipment, food, water, and supplies to the space station.
Today’s successful capture caps a remarkable two days for SpaceX, which saw its first Dragon launch atop the new Falcon 9 v1.1 rocket on Good Friday. As part of ongoing efforts to eventually make its rockets fully reusable, and capable of flying themselves back to touch down at their launch sites, it was hoped that this mission would deploy four fold-out carbon-fiber/aluminum honeycomb landing legs on its first stage to execute a “soft” splashdown in the Atlantic Ocean. As pointed out in AmericaSpace’s CRS-3 preview article, SpaceX have gone to great lengths to stress that the landing legs are experimental and anticipated only a 40-percent likelihood of success in the early stages.
In the minutes after launch, it was feared that rough seas in the Atlantic and wave heights in the range of 13-20 feet (4-6 meters) might ruin the soft splashdown. However, against many odds, it appears that a successful deployment of the landing legs and a safe, vertical splashdown was accomplished. Significantly, the excessive and uncontrollable roll motions which foiled the first soft-splashdown attempt during the Falcon 9 v1.1′s maiden voyage in September 2013 were notably absent on Friday, with recorded roll rates close to zero. “Data upload from tracking plane shows first-stage landing in Atlantic was good,” exulted Elon Musk in a Friday evening tweet. “Flight computers continued transmitting for 8 seconds after reaching the water. Stopped when booster went horizontal. Several boats en-route through heavy seas … ”
Following its berthing at the ISS, Dragon will shortly be unloaded of its enormous payload of supplies, which is considerably larger than its predecessors, thanks to the enhanced lift capacity of the upgraded Falcon 9 v1.1. “Dragon got a few upgrades since its last trip to station,” explained SpaceX on its Facebook page. “To support the more critical science payloads for the ISS, the spacecraft … has nearly quadrupled its previous powered cargo capability. Dragon will carry additional freezers in its pressurized section and, for the first time ever, powered cargo inside its unpressurized Trunk … The spacecraft is also sporting redesigned cargo racks to accommodate the additional payloads.”
One of the freezers is a powered General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER), which provides for the transportation and preservation of biological and other samples at temperatures between -160 degrees Celsius (-301 degrees Fahrenheit) and 4 degrees Celsius (39 degrees Fahrenheit). Dragon will also carry a pair of Microgravity Experiment Research Locker Incubators (MERLINs), both of which will supply a refrigerator/incubator at temperatures from -20 degrees Celsius (-4 degrees Fahrenheit) to 48.5 degrees Celsius (119 degrees Fahrenheit).
Powered cargoes inside the spacecraft’s unpressurized Trunk include the Optical Payload for Lasercomm Science (OPALS) to demonstrate high-bandwidth space-to-ground laser communications and the High-Definition Earth Viewing (HDEV) quartet of commercial HD video cameras to film Earth from multiple angles. Both of these payloads will be robotically installed onto the exterior of the ISS. Also aboard the vehicle will be a new Extravehicular Mobility Unit (EMU) space suit to replace the unit which malfunctioned and allowed water seepage into the helmet area during Luca Parmitano’s ill-fated EVA-23 in July 2013. The problematic suit will be returned to Earth aboard Dragon. Other payloads include the long-awaited legs for Robonaut-2.