NASA and SpaceX successfully launched cargo headed for the International Space Station, sending about 5,500 pounds of supplies and research equipment to the space station. The event was the first commercial launch to be carried out from the historic Launch Complex 39A at the Kennedy Space Center.

Originally, the launch was scheduled for Saturday, Feb. 18. However, even with all systems go at liffoff, Elon Musk personally called it off because "an upper stage engine steering hydraulic piston was slightly odd."

"If this is the only issue, flight would be fine, but need to make sure that it isn't symptomatic of a more significant upstream root cause," he tweeted.

The launch was halted to make way for an investigation, but Musk said the situation is likely to be 99 percent fine. Still, he didn't think that the remaining 1 percent was worth taking the risk.

"Better to wait a day," he added.

SpaceX's Dragon spacecraft aboard the company's Falcon 9 rocket finally saw liftoff Sunday, Feb. 19 at 9:39 a.m. EST.

ESA's Thomas Pesquet and NASA's Shane Kimbrough will be tasked with capturing the Dragon spacecraft when it arrives at the space station using the ISS's robotic arm. The capture can be viewed live on NASA TV on Wednesday, Feb. 22 starting 4:30 a.m.

This is SpaceX's 10th resupply mission to the ISS and will support investigations carried out by crew members of Expeditions 50 and 51.

Research Materials Aboard SpaceX Resupply Cargo

Several researches are headed for the ISS in this resupply mission, including a crystal growth experiment for crystallizing a monoclonal antibody undergoing clinical trials as an immunological disease treatment. Growing crystals in space is seen as a next step in the research because it will allow for the antibodies to be better preserved in the crystal as there won't be gravity that causes the crystals to collapse on themselves. Once in the crystal, the antibody's biological molecules will be more readily observed.

Another experiment will be focusing on how to better define how superbugs become drug-resistant. Aimed at countering bacterial resistance, it will explore the use of stem cells in the fight against drug-resistant bacteria.

At 2,200 pounds, the Stratospheric Aerosol and Gas Experiment takes up nearly half of the resupply mission's total cargo weight. Once installed on the ISS, the instrument will be used for surveying Earth's upper atmosphere to continue one of the space agency's longest-running programs for observing the planet.

Kennedy Space Station Launch Complex 39A

Launch Complexes 39A and 39B were built by NASA during the Apollo program. Except for Apollo 10, most space shuttle missions and every moon landing launch were done on 39A. The space agency decided it didn't need two launching pads after the last space shuttle took flight in 2011 so 39A was leased to SpaceX.

The company had intended to use 39A for commercial crew missions and launches for the new Falcon Heavy rocket but a static fire test accident put Launch Complex 40 out of commission, which pushed SpaceX to expedite refurbishments for 39A so all East Coat launches can be accommodated.

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