“I certainly hope we will nail the landing this time,” said Hans Koenigsmann, SpaceX’s vice president for flight reliability.

If launched on Friday, the Dragon capsule on top of the Falcon 9 rocket will arrive at the space station on Sunday. Plans are for it to stay at the space station until May, and then return to Earth carrying experimental samples including blood samples of Scott Kelly, the NASA astronaut who returned to Earth last month after nearly a year in space.

Among the nearly 7,000 pounds of supplies, equipment and experiments packed in the Dragon are seeds that will be grown on the space station. Last year for the first time, station astronauts ate red romaine grown and harvested in orbit.

This time, Chinese cabbage, chosen as the best growing and best tasting among tested vegetables, was added to the mix.

Gioia D. Massa, the principal investigator of the experiment, said the research “gives us a lot more information on how we can grow crops to provide supplemental nutrition to the astronauts as we start to do regular salad crop lettuce production on space station.”

Other experiments include an effort to track and catalog the variety of microbes living on the space station and a study of fungi in hopes that the weightless environment could spur them to produce novel compounds potentially useful as medicine.

The payload also includes 25 students’ experiments that were lost on the earlier SpaceX flight.

The biggest piece will be the $17.8 million Bigelow Expandable Activity Module, or Beam. Unlike the other metal modules of the International Space Station, Beam has soft sides made of layers of materials including tough fabrics similar to those found in bulletproof vests. The soft sides allow the module to be packed into a tuna can-shape enclosure at the bottom of the Dragon capsule.