Design
SpaceX, which aims to dramatically lower space transportation costs, designed Dragon 2 to be reused, not discarded as is typical of spacecraft. It is composed of a reusable capsule and a disposable trunk.
SpaceX and NASA initially certified the capsule to be used for five missions. As of March 2024, they are working to certify it for up to fifteen missions.[55]
To maximize cost-effectiveness, SpaceX incorporated several innovative design choices. The Crew Dragon employs eight side-mounted SuperDraco engines for its emergency escape system, eliminating the need for a traditional, disposable escape tower. Furthermore, instead of housing the critical and expensive life support, thruster, and propellant storage systems in a disposable service module, Dragon 2 integrates them within the capsule for reuse.
The trunk serves as an adapter between the capsule and the Falcon 9 rocket's second stage and also includes solar panels, a heat-dissipation radiator, and fins to provide aerodynamic stability during emergency aborts.[25] Dragon 2 integrates solar arrays directly into the trunk's structure, replacing the deployable panels of its predecessor, Dragon 1. On Cargo Dragon missions, the trunk can also be used to transport unpressurized payloads, such as the Roll Out Solar Array, or it can be fitted with a "boost kit" to perform reboosts of the ISS.[56] The trunk is connected to the capsule using a fitting known as "the claw".[57]
The typical Crew Dragon mission includes four astronauts: a commander who leads the mission and has primary responsibility for operating the spacecraft, a pilot who serves as backup for both command and operations, and two mission specialists who may have specific duties assigned depending on the mission. However, the Crew Dragon can fly missions with just two astronauts as needed, and in an emergency, up to seven astronauts could return to Earth from the ISS on Dragon.[58]
On the Crew Dragon, above the two center seats (occupied by the commander and pilot), there is a three-screen control panel. Below the seats is the cargo pallet, where around 500 lb of items can be stowed.[59] On the ground, crews enter the capsule through a side hatch. The capsule’s ceiling includes a small space toilet (with privacy curtain),[60] and an International Docking System Standard (IDSS) port. For private spaceflight missions not requiring ISS docking, the IDSS port can be replaced with a 1.2 m domed plexiglass window offering panoramic views, similar to the ISS Cupola.[61] Additionally, SpaceX has developed a "Skywalker" hatch for missions involving extravehicular activities.[62]
The Cargo Dragon is loaded from the side hatch as well as through the IDSS port on the ceiling. It lacks the control panels, life support, windows, and seats of the Crew Dragon.
The spacecraft can be operated in full vacuum, and crew wears SpaceX-designed space suits to protect them from a rapid cabin depressurization emergency event. The spacecraft has also been designed to be able to land safely with a leak "of up to an equivalent orifice of 6.35 mm in diameter".[25]
The spacecraft's nose cone protects the docking port and four forward-facing thrusters during ascent and reentry. This component pivots open for in-space operations.[25][32] Dragon 2's propellant and helium pressurant for emergency abort and orbital maneuvers are stored in composite-carbon-overwrap titanium spherical tanks at the capsule's base in an area known as the service section.
For launch aborts, the capsule relies on eight SuperDraco engines arranged in four redundant pairs. Each engine generates 71 kN of thrust.[30] Sixteen smaller Draco thrusters placed around the spacecraft control its attitude and perform orbital maneuvers.
When the capsule returns to Earth, a PICA-3 heat shield safeguards the capsule during reentry. Dragon 2 uses a total of six parachutes (two drogues and four mains) to decelerate after atmospheric entry and before splashdown, compared to the five used by Dragon 1. The additional parachute was required by NASA as a safety measure after a Dragon 1 suffered a parachute malfunction. The company also went through two rounds of parachute development before being certified to fly with crew.[63] In 2024, the use of the SuperDraco thrusters for propulsive landing was enabled again, but only as a backup for parachute emergencies.[64]