User:Craigboy/Dragon (spacecraft)



COTS Demo Flight 2 is the planned second test-flight for SpaceX's uncrewed Dragon cargo spacecraft, Dragon C2+, and the third overall flight for the company's two-stage Falcon 9 launch vehicle. It is expected to be the first American vehicle to visit the International Space Station (ISS) since the end of the Space Shuttle program, and the first commercial spacecraft to ever rendezvous and be berthed with another spacecraft.

The flight is under contract to NASA as the second Dragon mission in the Commercial Orbital Transportation Services (COTS) phase one program. The purpose of the COTS program is to develop and demonstrate commercial sources for cargo re-supply of the ISS.

Initially, the mission was to carry out a fly-by of the ISS, practice rendezvous maneuvers and berthing communications, and return to Earth. In July 2011, NASA gave tentative approval for combining the objectives of COTS 2 and COTS Demo Flight 3 into one flight. The proposed mission will first test rendezvous techniques and communications between Dragon and the ISS. If all goes well, then the mission's next phase would include berthing the Dragon to the ISS using the Canadarm2, staying for almost three weeks, and having astronauts unload cargo, and then load it with Earth-bound cargo. It would then be unberthed and return to Earth with a splashdown in the Pacific Ocean near the California coast.

In December 2011, NASA formally approved the merger of the COTS 2 and 3 missions into the Dragon C2+ flight. There have been several launch date delays since the mission was announced, most recently on 23 April 2012. The new targeted launch date is for 7 May. If all the COTS objectives are successfully completed, then the Falcon 9-Dragon system will be certified to start regular cargo delivery missions to the ISS.

Payload
The pressurized section will carry 520 kg worth of cargo to the ISS, which includes food, water, clothing, cargo bags, computer hardware, the NanoRacks Module 9 (student experiments and scientific gear) and other miscellaneous cargo. The return flight is planned to carry 660 kg worth of pressurized cargo back to Earth, the cargo includes experiment samples, experiment hardware, ISS' systems hardware and Extravehicular Mobility Unit hardware.

Originally, SpaceX also intended to launch two secondary payload satellites from the Dragon sometime in the first 72 hours after launch; however, on 28 December 2011, SpaceX and Orbcomm announced a revised schedule that dropped the satellite deployment from the Dragon C2+ flight plan.

History
NASA and SpaceX signed a contract for COTS cargo resupply services on 18 August 2006. The agreement called for three test-flights, under the COTS phase 1 demonstration program. The first COTS mission, COTS Demo Flight1, was planned to take place as early as 2008, with the COTS 2 and COTS 3 missions taking place in 2009 but numerous delays pushed the launches back.

The COTS Demo Flight 1 was completed on 8 December 2010, when the Dragon capsule was successfully recovered from orbit, making it the first commercially-built and operated spacecraft to ever do so. Due to the mission's success, SpaceX lobbied NASA to combine the COTS 2 ISS flyby flight, which would have seen a Dragon spacecraft approach the ISS but stay about 10 km away from it, and the COTS 3 flight that would actually berth with the station. At a 15 July 2011 meeting, NASA tentatively approved combining the two COTS missions to accelerate the program into the operational supply mission phase in 2012.

Also in July 2011, the Falcon 9 launch vehicle arrived at SpaceX's Cape Canaveral Launch Complex 40 (LC-40) facilities and SpaceX announced a November 30th launch date for the combined mission. There was concern that the Russian Progress 44 cargo resupply failure in August 2011, which might have forced the ISS to be temporarily abandoned in mid-November would have affected the mission launch date. The COTS 2 Dragon spacecraft arrived at the launch site on 23 October 2011. In late November the mission was delayed to December 19th.

On 9 December, NASA officially approved the merger of the COTS 2 and 3 missions into the Dragon C2 flight, but delayed the flight to tentatively 7 February 2012. However, on 16 January 2012, SpaceX announced it needed more time for engineering tests, and postponed the launch date again, with no replacement date initially announced. With a busy launch schedule at Cape Canaveral, and with other missions to the ISS, NASA and SpaceX did not announce a new date until mid-March for a 30 April launch. On 1 March 2012, a fueled countdown test called a Wet Dress Rehearsal (WDR), was successfully completed for the COTS 2 mission. On 16 April its Flight Readiness Review (FRR) was completed by NASA who stated that SpaceX's 30 April launch was feasible. But on April 23rd SpaceX chose to delay the launch to 7 May. A static fire of the Falcon 9 is scheduled for April 30th.

Flight days one and two
About ten minutes after lift off, Dragon will reach its preliminary orbit it will then deploy its solar arrays and begin a series of engine firings to reach the station. During this part of the flight, Dragon will demonstrate the first set of tests as part of its COTS 2 milestone requirements. The spacecraft will perform a test of its Absolute GPS (AGPS) system, using global positioning system satellites to determine its location. It also will conduct a free drift demonstration, allowing the spacecraft to float freely with all of its thrusters not firing. Then Dragon will perform a demonstration of its abort capability, to ensure it could move away from the station if necessary.

Flight day three
On the flight day three, Dragon will perform a burn that will bring it to a path 2.5 kilometers (1.5 miles) below the station. During this “fly‐under,” Dragon will establish communications with the station using its COTS Ultra‐high frequency Communication Unit (CUCU). Dragon will perform a test of its Relative GPS (RGPS) system, which uses the relative positions of the spacecraft to the space station to determine its location. Also, using the Crew Command Panel (CCP) on board the Cupola module, the Expedition 31 crew will briefly interact with Dragon, monitoring the fly‐under and sending a command to Dragon to turn on its strobe light. Once the fly‐under is complete, Dragon will fire its engines to begin a loop out in front, above and then behind the station in a racetrack pattern at a distance between 7‐10 kilometers (4‐6.2 miles). This will set the spacecraft up for a re‐rendezvous with the station the next day.

Flight day four
On flight day four, Dragon will perform another engine burn that will bring it 2.5 kilometers (1.5 miles) below the station once again. A go/no‐go is performed by NASA's Mission Control Houston team to allow SpaceX to perform another set of burns that will bring Dragon to within 1.4 kilometers (0.87 miles) of the station. Another go/no‐go will take place from Mission Control Houston, and then Dragon will move from up to 250 meters (820 feet) from the station. The COTS 3 demonstration milestones will begin, the first of which is a test of Dragon’s LIDAR based DragonEye system. This test will confirm that Dragon’s position and velocity is accurate by comparing the LIDAR image that Dragon receives against Dragon’s thermal imagers. A series of checkout maneuvers will commence. The SpaceX flight control team in Hawthorne, Calif., will command the spacecraft to approach the station from its hold position. It will move from 250 meters to 220 meters below the station (720 feet). The crew, using the command panel, will then insruct Dragon to retreat, and the spacecraft will move back down to the hold point. This test will ensure that Dragon’s range to the ISS is accurate, and that the flight control team sees the spacecraft’s acceleration and braking perform as expected. It will hold at 250 meters, and once again the Dragon flight team will command it to approach the station. At the 220 meter position, the crew will command the vehicle to hold.

Another go/no‐go is performed in Houston, and then Dragon is permitted to enter inside the Keep‐Out Sphere (KOS), an imaginary circle drawn 200 meters (656 feet) around the station that prevents the risk of collision with the orbiting complex. Dragon will proceed to a position 30 meters (98 feet) from the station and will automatically hold. Another go/no‐go is completed, and then Dragon will proceed to the 10 meter (32 feet) position, which is the capture point. A final go/no‐go is performed, and the Mission Control Houston team will notify the crew they are go to capture Dragon. At that point, from the Cupola module, Expedition 31 crew member Don Pettit will use the station’s Mobile Servicing System (Canadarm2) to reach out and grapple the Dragon spacecraft. Pettit, with the help of fellow crewmember Andre Kuipers, will guide Dragon to the Harmony module's Earth‐facing Common Berthing Mechanism, and berth it to the station. If the rendezvous and Dragon testing runs long, Mission Control could elect to leave Dragon grappled to the station’s arm overnight before berthing it the next day.

Flight day five and remainder of mission
On flight day five, after performing an inspection of the air inside Dragon, the crew will open the hatch between Dragon and the station. Dragon will spend about 18 days berthed to the space station, giving ISS astronauts time to unload cargo and load Dragon with Earth-bound cargo. At which point the crew will unberth Dragon from Harmony using the station's RMS. The arm will move Dragon about 10 meters away from the station and release it. Dragon will then perform a series of engine burns what will place it on a trajectory to take it away from the vicinity of the station. Mission Control Houston will then confirm that Dragon is on a safe path away from the complex. Approximately four hours after Dragon leaves the station, it will conduct its deorbit burn, which lasts about seven minutes. It takes about 30 minutes for Dragon to re‐enter the Earth’s atmosphere and splashdown in the Pacific Ocean. It will be recovered from about 450 kilometers (250 miles) off the West Coast of the United States. If all mission objectives are successfully completed then the Falcon 9-Dragon system would achieve certification for cargo delivery and SpaceX would be allowed to begin its COTS contract.