SpaceX Dragon 2


The SpaceX Dragon 2 is a class of reusable spacecraft developed and manufactured by American aerospace manufacturer SpaceX as the successor to Dragon, a reusable cargo spacecraft. It has two variants: Crew Dragon, a space capsule capable of ferrying up to seven astronauts, and Cargo Dragon, an updated replacement for the original Dragon spacecraft. The spacecraft launches atop a Falcon 9 Block 5 rocket and returns to Earth via an ocean splashdown. Unlike its predecessor, the spacecraft can dock itself to the ISS instead of being berthed. Crew Dragon is equipped with an integrated launch escape system capable of accelerating the vehicle away from the rocket in an emergency at, accomplished by using a set of four side-mounted thruster pods with two SuperDraco engines each. The spacecraft features redesigned solar arrays and a modified outer mold line compared to the original Dragon, and possess new flight computers and avionics. As of March 2020, four Dragon 2 spacecraft have been manufactured.
Crew Dragon serves as one of two spacecraft that is expected to transport crews to and from the International Space Station under NASA's Commercial Crew Program, the other being the Boeing CST-100 Starliner. It is also expected to be used in flights by American space tourism company Space Adventures and to shuttle tourists to and from Axiom Space's planned space station. Crew Dragon's first non-piloted test flight occurred in March 2019, and its first crewed flight – with astronauts Robert Behnken and Douglas Hurley – occurred in May 2020. This test flight marked the first time a private company launched a crewed orbital spacecraft. Cargo Dragon is expected to supply cargo to the ISS under a Commercial Resupply Services-2 contract with NASA, along with Northrop Grumman Innovation Systems' Cygnus spacecraft and Sierra Nevada Corporation's Dream Chaser spacecraft. The first flight of the Cargo Dragon is planned to launch in October 2020.

Development and variants

There are two variants: Crew Dragon and Cargo Dragon. Crew Dragon was initially called "DragonRider" and it was intended from the beginning to support a crew of seven or a combination of crew and cargo. It is able to perform fully autonomous rendezvous and docking with manual override ability, using the NASA Docking System. For typical missions, Crew Dragon will remain docked to the ISS for a period of 180 days, but is designed to remain on the station for up to 210 days, matching the Russian Soyuz spacecraft. From the beginning of the development process, SpaceX planned to use an integrated pusher launch escape system for the Dragon spacecraft.

Crew Dragon

SpaceX originally intended to land Crew Dragon on land using the LES engines, with parachutes and an ocean splashdown available in the case of an aborted launch. Precision water landing under parachutes was proposed to NASA as "the baseline return and recovery approach for the first few flights" of Crew Dragon. Propulsive landing was later cancelled, leaving ocean splashdown under parachutes as the only option., the Paragon Space Development Corporation was assisting in developing Crew Dragon's life-support system.
In 2012, SpaceX was in talks with Orbital Outfitters about developing space suits to wear during launch and re-entry. Each crew member wears a custom space suit fitted for them. The suit is primarily designed for use inside the Dragon : however, in the case of a rapid cabin depressurization, the suit can protect the crew members. The suit can also provide cooling for astronauts during normal flight. For the Demo-1 mission, a test dummy nicknamed Ripley was fitted with the spacesuit and sensors. The spacesuit "is made from Nomex", a fire retardant fabric similar to Kevlar.
At a NASA news conference on 18 May 2012, SpaceX confirmed their target launch price for crewed Dragon flights of US$160 million, or about US$23 million per seat if the maximum crew of seven is aboard and NASA orders at least four Crew Dragon flights per year. This contrasts with the 2014 Soyuz launch price of US$76 million per seat for NASA astronauts. The spacecraft's design was unveiled on 29 May 2014, during a press event at SpaceX headquarters in Hawthorne, California. In October 2014, NASA selected the Dragon spacecraft as one of the candidates to fly American astronauts to the International Space Station, under the Commercial Crew Program. SpaceX is using the Falcon 9 Block 5 launch vehicle to launch Dragon 2.

Cargo Dragon

Although Dragon 2 was intended from the earliest design concept to carry crew, or with fewer seats, both crew and cargo, a second round of multi-year cargo supply contracts was solicited by NASA in 2014, to supply the ISS in 2020–2024. This led to SpaceX proposing a separately-named model, Cargo Dragon, for the NASA flights. SpaceX won a contract award for Cargo Dragon as a result of the CRS2 bid competition, with contracts awarded in January 2016 for six flights.

Design

Dragon 2 includes the following features:
Dragon 2 is partially reusable, potentially resulting in a significant cost reduction. After earlier plans of SpaceX to use new capsules for every crewed flight for NASA both agreed to reuse Crew Dragon capsules for NASA flights. Cargo Dragon can carry to the ISS; Crew Dragon has a capacity of seven astronauts. Above the seats, there is a three-screen control panel, a toilet, and the docking hatch. Ocean landings are accomplished with four main parachutes in both variants. The parachute system was fully redesigned from the one used in the prior Dragon capsule, due to the need to deploy the parachutes under a variety of launch abort scenarios.
Crew Dragon has eight side-mounted SuperDraco engines, clustered in redundant pairs in four engine pods, with each engine able to produce of thrust to be used for launch aborts. Each pod also contains four Draco thrusters that can be used for attitude control and orbital maneuvers. The SuperDraco engine combustion chamber is printed of Inconel, an alloy of nickel and iron, using a process of direct metal laser sintering. Engines are contained in a protective nacelle to prevent fault propagation if an engine fails.
Once in orbit, Dragon 2 is able to autonomously dock to the ISS. Dragon used berthing, a non-autonomous means to attach to the ISS that was completed by use of the Canadarm2 robotic arm. Pilots of Crew Dragon retain the ability to dock the spacecraft using manual controls interfaced with a static tablet-like computer. The spacecraft can be operated in full vacuum, and "the crew will wear SpaceX-designed space suits to protect them from a rapid cabin depressurization emergency event". Also, the spacecraft will be able to return safely if a leak occurs "of up to an equivalent orifice of 6.35 mm in diameter".
Propellant and helium pressurant for both launch aborts and on-orbit maneuvering is contained in composite-carbon-overwrap titanium spherical tanks. A PICA-X heat shield protects the capsule during reentry, while a movable ballast sled allows more precise attitude control of the spacecraft during the atmospheric entry phase of the return to Earth and more accurate control of the landing ellipse location. A reusable nose cone "protects the vessel and the docking adaptor during ascent and reentry", pivoting on a hinge to enable in-space docking and returning to the covered position for reentry and future launches.
The trunk is the third structural element of the spacecraft, containing solar panels, heat-removal radiators, and fins to provide aerodynamic stability during emergency aborts.
The previous Cargo Dragon's deployable solar arrays have been eliminated and are now built into the trunk itself. This increases volume space, reduces the number of mechanisms on the vehicle and further increases reliability.

Crewed flights

Dragon is intended to fulfill a set of requirements that will make the capsule useful to both commercial and government customers. SpaceX and Bigelow Aerospace were working together to support round-trip transport of commercial passengers to low Earth orbit destinations, but the plan was canceled. Instead Axiom plans to launch tourists to the Space Station and eventually their own private space station. NASA flights to the ISS will only have four astronauts, with the added payload mass and volume used to carry pressurized cargo.
On 16 September 2014, NASA announced that SpaceX and Boeing had been selected to provide crew transportation to the ISS. SpaceX will receive US$2.6 billion under this contract. Dragon was the least expensive proposal, but NASA's William H. Gerstenmaier considered the CST-100 proposal the stronger of the two.
In a departure from the prior NASA practice, where construction contracts with commercial firms led to direct NASA operation of the spacecraft, NASA is purchasing space transport services from SpaceX, including construction, launch, and operation of the Dragon 2.
In August 2018, NASA and SpaceX agreed on the loading procedures for propellants, vehicle fluids and crew. High-pressure helium will be loaded first, followed by the passengers approximately two hours prior to scheduled launch; the ground crew will then depart the launch pad and move to a safe distance. The launch escape system will be activated approximately 40 minutes prior to launch, with propellant loading commencing several minutes later. The first automated test mission launched to the International Space Station on 2 March 2019.
In early 2019, crewed flights were expected to begin no earlier than July 2019. They were later planned to begin no earlier than on 30 May 2020. The first crewed flight launched on 30 May 2020 with the launch of the Demo-2 mission.
In June 2019, Bigelow Space Operations announced it had reserved with SpaceX up to four missions of four passengers each to ISS as early as 2020 and planned to sell them for around US$52 million per seat. These plans were canceled by September 2019.
On 18 February 2020, building on development for NASA's commercial crew program, Space Adventures announced an agreement with SpaceX to fly up to four paying space tourists on a standalone mission aboard a Crew Dragon spacecraft in late 2021 or 2022 that could reach an altitude two-to-three times higher than the International Space Station.

Testing

SpaceX planned a series of four flight tests for the Crew Dragon - a "pad abort" test, an uncrewed orbital flight to the ISS, an in-flight abort test, and finally a 14-day crewed demonstration mission to the ISS, which was initially planned for July 2019, but after a Dragon capsule explosion, was delayed to May 2020.

Pad abort and hover tests

The pad abort test was conducted successfully on 6 May 2015 at SpaceX's leased SLC-40. Dragon landed safely in the ocean to the east of the launchpad 99 seconds after ignition of the SuperDraco engines. While a flight-like Dragon 2 and trunk were used for the pad abort test, they rested atop a truss structure for the test rather than a full Falcon 9 rocket. A crash test dummy embedded with a suite of sensors was placed inside the test vehicle to record acceleration loads and forces at the crew seat, while the remaining six seats were loaded with weights to simulate full-passenger-load weight. The test objective was to demonstrate sufficient total impulse, thrust and controllability to conduct a safe pad abort. A fuel mixture ratio issue was detected after the flight in one of the eight SuperDraco engines causing it to under perform, but did not materially affect the flight.
On 24 November 2015, SpaceX conducted a test of Dragon 2's hovering abilities at the firm's rocket development facility in McGregor, Texas. In a video, the spacecraft is shown suspended by a hoisting cable and igniting its SuperDraco engines to hover for about 5 seconds, balancing on its 8 engines firing at reduced thrust to compensate exactly for gravity. The test vehicle was the same capsule that performed the pad abort test earlier in 2015; it was nicknamed DragonFly.

Demo-1: orbital flight test

In 2015, NASA named its first Commercial Crew astronaut cadre of four veteran astronauts to work with SpaceX and Boeing – Robert Behnken, Eric Boe, Sunita Williams, and Douglas Hurley. The Demo-1 mission completed the last milestone of the Commercial Crew Development program, paving the way to starting commercial services under an upcoming ISS Crew Transportation Services contract. On 3 August 2018, NASA announced the crew for the DM-2 mission. The crew of two will be formed by NASA astronauts Bob Behnken and Doug Hurley. Behnken previously flew as mission specialist on the STS-123 and the STS-130 missions. Hurley previously flew as a pilot on the STS-127 mission and on the final Space Shuttle mission, the STS-135 mission.
The first orbital test of Crew Dragon was an uncrewed mission, officially designated "Crew Demo-1" and launched on 2 March 2019. The spacecraft tested the approach and automated docking procedures with the ISS, remained docked until 8 March 2019, then conducted the full re-entry, splashdown and recovery steps to qualify for a crewed mission. Life-support systems were monitored all along the test flight. The same capsule was planned to be re-used in June 2019 for an in-flight abort test before it exploded on 20 April 2019.

Explosion during testing

On 20 April 2019, the Crew Dragon capsule used in the Demo-1 mission was destroyed in an explosion during static fire testing at the Landing Zone 1 facility. On the day of the explosion, the initial testing of the Crew Dragon's Draco thrusters was successful, with the accident occurring during the test of the SuperDraco abort system.
Telemetry, high-speed camera footage, and analysis of recovered debris indicate the problem occurred when a small amount of dinitrogen tetroxide leaked into a helium line used to pressurize the propellant tanks. The leakage apparently occurred during pre-test processing. As a result, the pressurization of the system 100 ms before firing damaged a check valve and resulted in the explosion.
Since the destroyed capsule had been slated for use in the upcoming in-flight abort test, the explosion and investigation delayed that test and the subsequent crewed orbital test.
The SuperDraco engine test that failed on 20 April 2019 was repeated successfully on 13 November 2019. The full duration static fire test of Crew Dragon's launch escape system took place at Cape Canaveral Air Force Station at SpaceX's Landing Zone 1 at 20:08 UTC. The test was successful, showing that the modifications made to the vehicle to prevent a failure like the one that happened 20 April 2019 were successful. The vehicle used for this ground test would also be used for the following in-flight abort test.
Some of the modifications are:
The Crew Dragon in-flight abort test was launched on 19 January 2020 at 15:30 UTC from Launch Complex 39A on a suborbital trajectory to conduct a separation and abort scenario in the troposphere at transonic velocities shortly after passing through max Q, where the vehicle experiences maximum aerodynamic pressure. The Dragon 2 used its SuperDraco abort engines to push itself away from the Falcon 9 after an intentional premature engine cutoff. Ten seconds after Dragon 2 was jettisoned, the Falcon 9 exploded and was destroyed. The spacecraft followed its suborbital trajectory to apogee, at which point the spacecraft's trunk was jettisoned. The smaller Draco engines were then used to orient the vehicle for the descent. All major functions were executed, including separation, engine firings, parachute deployment, and landing. Dragon 2 splashed down at 15:38:54 UTC just off the Florida coast in the Atlantic Ocean. The test objective was to demonstrate the ability to safely move away from the ascending rocket under the most challenging atmospheric conditions of the flight trajectory, imposing the worst structural stress of a real flight on the rocket and spacecraft. The abort test was performed using a Falcon 9 Block 5 rocket with a fully fueled second stage with a mass simulator replacing the Merlin engine.
Earlier, this test had been scheduled before the uncrewed orbital test, however, SpaceX and NASA considered it safer to use a flight representative capsule rather than the test article from the pad abort test.
This test was previously planned to use the capsule C201 from Demo-1, however, C201 was destroyed in an explosion during a static fire testing on 20 April 2019. Capsule C205, originally planned for Demo-2 was used for the In-Flight Abort Test with C206 being planned for use during Demo-2. This was the final flight test of the spacecraft before it began carrying astronauts to the International Space Station under NASA's Commercial Crew Program.
Prior to the flight test, teams completed launch day procedures for the first crewed flight test, from suit-up to launch pad operations. The joint teams conducted full data reviews that needed to be completed prior to NASA astronauts flying on the system during SpaceX's Demo-2 mission.

Demo-2: crewed orbital flight test

On 17 April 2020, NASA Administrator Jim Bridenstine announced the first crewed Crew Dragon Demo-2 to the International Space Station would launch on 27 May 2020. Astronauts Bob Behnken and Doug Hurley crewed the mission, marking the first crewed launch to the International Space Station from US soil since STS-135 in July 2011. The original launch was postponed to 30 May 2020 due to weather conditions at the launch site. The second launch attempt was successful, with capsule C206, later named Endeavour by the crew, launching on 30 May 2020 19:22 UTC. The capsule successfully docked with the International Space Station on 31 May 2020 at 14:27 UTC.
Launching in the Dragon 2 spacecraft was described by astronaut Bob Behnken as "smooth off the pad" but "we were definitely driving and riding a dragon all the way up... a little bit less g's but more 'alive' is probably the best way I would describe it".

List of vehicles

List of flights

As of June 2020, there are nine Crew Dragon flights contracted to carry crew, seven are contracted by NASA, and two contracted by private companies Axiom Space and Space Adventures.

Other crewed orbital spacecraft

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