Artist rendering of the SpaceX Dragon spacecraft being berthed to ISS
|Mission type||ISS resupply|
|Start of mission|
|Launch date||12 September 2014 (planned)|
|Rocket||Falcon 9 v1.1|
|Launch site||Cape Canaveral SLC-40|
|Berthing at ISS|
|Berthing port||Harmony nadir|
SpaceX CRS-4, also known as SpX-4, is a cargo resupply mission to the International Space Station, contracted to NASA, and is currently manifested for launch in the fourth quarter of 2014. It will be the sixth flight for SpaceX's uncrewed Dragon cargo spacecraft, and the fourth SpaceX operational mission contracted to NASA under a Commercial Resupply Services contract.
NASA has contracted for the CRS-4 mission and therefore determines the primary payload, date/time of launch, and target orbital parameters. Among other NASA cargo, the ISS-RapidScat will be launched as an external payload to be attached on the end of the station's Columbus laboratory. Also crs-4 will include the Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS). This launcher will provide still another means to release other small satellites from the ISS. SpaceX CRS-4 also will carry a new permanent life science research facility to the station. The Bone Densitometer (BD) payload, developed by Techshot, will provide a bone density scanning capability on ISS for utilization by NASA and the Center for the Advancement of Science in Space (CASIS). The system measures bone mineral density (and lean and fat tissue) in mice using Dual-Energy X-ray Absorptiometry (DEXA). 
SpaceX has the primary control over manifesting, scheduling and loading secondary payloads. However there are certain restrictions included in their contract with NASA that preclude specified hazards on the secondary payloads, and also require contract-specified probabilities of success and safety margins for any SpaceX reboosts of the secondary satellites once the Falcon 9 second stage has achieved its initial low-Earth orbit (LEO).
The CRS-4 mission will carry the 3D Printing in Zero-G Experiment to the ISS, as well as two small satellites as secondary payloads that will be deployed from the ISS: Arkyd-3 and SPINSAT.
3D Printing in Zero-G Experiment
The 3D Printing in Zero-G Experiment will demonstrate the use of 3D printing technology in space. 3D printing works by the process of extruding streams of heated material (plastic, metal, etc.) and building a three-dimensional structure layer-upon-layer. The 3D Printing in Zero-G Experiment will test the 3D printer specifically designed for microgravity, by Made In Space, Inc., of Mountain View, California. Made In Space’s customized 3D printer will be the first device to manufacture parts away from planet Earth. The 3D Printing in Zero-G Experiment will validate the capability of additive manufacturing in zero-gravity. This experiment on the International Space Station is the first step towards establishing an on-demand machine shop in space, a critical enabling component for deep-space crewed missions and in-space manufacturing.
Planetary Resources has packaged a number of the non-optical satellite technologies of its larger Arkyd-100 telescope satellite—essentially the entire base of the Arkyd-100 satellite model revealed in January 2013, but without the space telescope—into a "cost-effective box" of 'Arkyd 3, or A3, for early in-space flight testing as a subscale nanosatellite. The Arkyd 3 testbed satellite will be packaged in a 3U CubeSat form-factor of 10×10×30 centimetres (0.33×0.33×0.98 ft). The company has contracted with NanoRacks to take the A3 to the ISS where it will be released from the airlock in the Kibo module.
The subsystems to be tested include the avionics, attitude determination and control system (both sensors and actuators), and integrated propulsion system that will enable proximity operations for the Arkyd line of prospectors in the future.
SPINSAT will also be a technology demonstrator for electric solid propellant (ESP) thrusters from Digital Solid State Propulsion (DSSP). DSSP's technology utilizes electric propulsion to enable small satellites to make orbital maneuvers that have generally not been possible in the very small, mass-constrained satellites such as CubeSats and nanosats. This will be DSSP's first flight and will be deployed from the Kibo module airlock. NASA safety experts approved the mission—which by its nature must start with the satellite inside the habitable volume of the ISS—because the satellite's 12 thruster-clusters burn an inert solid fuel, and then only when an electric charge is passed across it.
- "Worldwide Launch Schedule". Spaceflight Now. Retrieved 2013-12-25.
- "SpaceX Launch Manifest". SpaceX. Retrieved 2013-01-31.
- Suffredini, Mike (14 April 2014). "NAC: International Space Station Program Status". NASA.gov. p. 18. Retrieved 31 July 2014.
- "Worldwide launch schedule". Spaceflightnow. 22 November 2012. Retrieved 2014-07-08.
- "Watching Earth’s Winds, On a Shoestring | NASA". Nasa.gov. 2013-10-29. Retrieved 2014-05-18.
- "Meet Space Station’s Small Satellite Launcher Suite | NASA". Nasa.gov. 2014-04-03. Retrieved 2014-05-18.
- "Dragon C2, CRS-1,... CRS-12". Space.skyrocket.de. Retrieved 2014-05-18.
- "Made In Space and NASA to Send First 3D Printer into Space". Made In Space. 2013-05-31. Retrieved 2014-08-04.
- "3D Printing In Zero-G Technology Demonstration (3D Printing In Zero-G)". Made In Space. 2014-07-31. Retrieved 2014-08-04.
- Heater, Bryan (2013-01-21). "Planetary Resources shows off Arkyd-100 prototype, gives a tour of its workspace". Engadget. Retrieved 2013-01-23.
- Mike Wall (2013-04-24). "Private Asteroid-Mining Project Launching Tiny Satellites in 2014". Space.com. Retrieved 2013-04-25.
- "Planetary Resources Inks 3D Systems Deal, Plans Test Launch From ISS". Xconomy. 2013-06-26. Retrieved 2014-05-18.
- Lewicki, Chris; Chris Voorhees; Spencer Anunsen (2013-04-24). "Planetary Resources One-year Update". Planetary Resources. Retrieved 2013-05-02.
- Messier, Doug (2014-04-06). "Digital Solid State Propulsion is Headed to ISS". Parabolic Arc. Retrieved 2014-04-07.
- "Spinsat". Space.skyrocket.de. Retrieved 2014-05-18.