Credit: SpaceX   Dragon is a free-flying, reusable spacecraft developed to carry cargo, and eventually astronauts, into space.

• Built by SpaceX from the ground up. SpaceX developed Dragon from a blank sheet to its first mission in just over four years.
  
  
• First privately developed spacecraft to attach to the International Space Station (ISS). In May 2012, Dragon became the first commercial spacecraft to deliver cargo to the ISS and return safely to Earth, a feat previously achieved only by governments. In October 2012, Dragon completed its second mission to the ISS, its first of 12 official cargo resupply missions for NASA.
  
  
• Payload capability. Dragon carries cargo in a pressurized capsule and an unpressurized trunk. It can carry 6,000 kilograms (13,228 pounds), split between pressurized cargo inside the capsule and unpressurized cargo in the trunk, which also houses Dragon's solar panels.
  
  
• Dimensions. Dragon is 4.4 meters (14.4 feet) tall and 3.66 meters (12 feet) in diameter. The trunk is 2.8 meters (9.2 feet) tall and 3.66 meters (12 feet) wide. With solar panels fully extended, the vehicle measures 16.5 meters (54 feet) wide.
  
  
• Advanced heat shield. Dragon has the most effective heat shield in the world. Designed with NASA and fabricated by SpaceX, it is made of PICA-X, a high-performance variant on NASA's original phenolic impregnated carbon ablator (PICA). PICA-X is designed to withstand heat rates from a lunar return mission, which far exceed the requirements for a low-Earth orbit mission.
  
  
• Smooth, controlled reentry. Dragon's passively stable shape generates lift as it reenters the Earth’s atmosphere. Its 18 Draco thrusters provide roll control during reentry to keep it precisely on course toward the landing site before its parachutes deploy.
  
  
• Designed for astronauts. Although this resupply mission carries only cargo, Dragon was designed from the outset to carry crew. Under a $440 million agreement with NASA, SpaceX is developing refinements for transporting crew, including seating for seven astronauts, the most advanced launch escape system ever developed, a propulsive landing system, environmental controls, and life-support systems. SpaceX expects to undertake its first crew demonstration in 2015.
  
  
• True rumor. Dragon was named for the fictional Puff the Magic Dragon after critics in 2002 deemed SpaceX's founding goals fantastical.
  
  

Key Components

Draco Thrusters: Dragon's 18 Draco thrusters permit orbital maneuvering and attitude control. Powered by nitrogen tetroxide/monomethylhydrazine (NTO/MMH) storable propellants; 90 lbf (400 N) thrust is used to control the approach to the ISS, power departure from the ISS, and control Dragon's attitude upon reentry.

Power: Two solar array wings on trunk (eight panels total) produce more than 5 kilowatts of power. Surplus power recharges Dragon's batteries for the periods when it is in darkness. In low-Earth orbit, Dragon is in darkness about 40% of the time.

Avionics: Dual fault-tolerant computing provides seamless real-time backups to all critical avionics components, providing one of the most reliable architectures to fly. The RIOs (remote input/output modules) provide a common computing platform with configurable input and output control cards. This architecture facilitates manufacturing and ensures the components' reliability.

Communications: Communications between Dragon and the ISS are provided by COTS UHF Communications Unit (CUCU). CUCU was delivered to the Space Station on STS-129. The ISS crew commands Dragon using the Crew Command Panel (CCP). Dragon can also communicate on S-band via either tracking and data relay system (TDRSS) or ground stations.

Environmental Control System: Astronauts will enter Dragon to remove cargo. Dragon's cabin is habitable, with air circulation, lighting, fire detection and suppression, air temperature control, pressure and humidity monitoring.

Thermal Protection System: Primary heat shield: Tiled phenolic impregnated carbon ablator (PICA-X), fabricated in-house. The backshell is made of SpaceX Proprietary Ablative Material (SPAM).

Parachutes: Dual drogue parachutes slow and stabilize the craft before three main parachutes bring it to a gentle landing. Dragon can also land safely with only one drogue and one main parachute if needed.

Transporting Crew: While it initially is transporting cargo, Dragon was designed from the beginning to transport crew and is currently undergoing modifications to make this possible. Crew configuration will include life support systems, a crew escape system, and onboard controls that allow the crew to take control from the flight computer when needed. This focus on commonality between cargo and crew configurations minimizes the design effort and simplifies the human-rating process, allowing systems critical to Dragon crew safety and ISS safety to be fully tested on unmanned flights.