SpaceX CRS-4, also known as SpX-4, was a cargo resupply mission to the International Space Station, contracted to NASA, which was launched on 21 September 2014 and arrived at the space station on 23 September 2014. It was 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. The mission brought equipment and supplies to the space station, including the first 3D printer to be tested in space, a device to measure wind speed on Earth, and small satellites to be launched from the station. It also brought 20 mice for long-term research aboard the ISS.