Development of Space Exploration Technologies' (SpaceX) Dragon crew and cargo capsule is progressing, with testing and selecting under way for the mix of internally developed and commercially procured subsystems.
The crew and cargo versions of the blunt-body capsule are essentially the same, with a 3.81m (12.5ft)-diameter base, when the ablative thermal protection system is in place, and a maximum take-off weight of around 7,000kg (15,400lb,) including 2,500kg of crew or cargo mass. The SpaceX-built Falcon 9 to launch the Dragon will have at least an 8,700kg payload capability to low-Earth orbit.
Using NASA human spaceflight safety standards for the Dragon, SpaceX has adopted a quad-redundant design philosophy and is purchasing "high-end-class geostationary satellite" systems for long-duration mission capability, such as lithium-ion batteries. The life-support system for the manned variant will be an upgraded version of the cargo model's environmental control system.
The descent parachute provider has been selected, but not announced, and thermal protection materials testing is under way. In January SpaceX completed construction of its manufacturing pathfinder engineering model Dragon for structural and splashdown tests.
SpaceX is now fabricating test units of its internally developed bi-propellant roll control system/orbital manoeuvring system thruster, which is now in fabrication. "At our test stand in Texas there will be testing in the third quarter. It is capable of short impulses, up to 20s, but can also fire for minutes at a time," says SpaceX chief executive Elon Musk.
The thruster's fuel tanks are in the base of the capsule, in an integrated service module section that Musk says aids re-entry orientation.
The Dragon also has what SpaceX calls a "trunk" - the skirt between the Dragon and the Falcon 9's second stage, that will contain commercially purchased solar arrays and the thermal radiators.
While the capsule's software will be an enhanced version of that developed for the reusable Falcon 9's second stage, the company has already procured the flight computer hardware.
Source: Flight International
