NASA scientists can only sit and watch anxiously as SpaceX’s Dragon capsule carries their experiments to the International Space Station. SpaceX’s Falcon 9 rocket is set to carry the Dragon on the April 8 launch at 4:43 p.m. Eastern, and today, NASA researchers provided details about the approximately 4,409 pounds of precious cargo aboard the SpaceX vessel — a payload much heavier than the average payload.

“This is a launch that we’ve been waiting for for quite some time because it’s really important to our overall ISS research program,” Julie Robinson, chief scientist for the ISS program at NASA’s Johnson Space Center in Houston, Texas, said during today’s teleconference. “SpaceX is a workhorse for us.”

The two tons of research supplies on board the Dragon capsule will support over 280 investigations, some new and some ongoing. Typically, cargo rockets burn up upon return, but this flight will finally bring back some important blood and urine samples from Scott Kelly’s one-year expedition. If the samples are successfully returned for analysis, it will mark a big success for SpaceX and private space companies that have been pushing for reusable rockets.

“These flights are really important in biology and human research, so we’re really excited about this flight,” said Robinson.

In addition to fungi, rodents, and Chinese cabbage, 1,400 kilograms of the payload will be devoted to an expandable space habitat called Bigelow Expandable Activity Module (BEAM) — an extra comfortable space where astronauts can work.

“In general, expandable modules require minimal payload volume on a rocket. That’s their main benefit,” said Rajib Dasgupta, the NASA project and technical integration manager of BEAM at Johnson. BEAM, which lies in the trunk of the Dragon capsule, has a habitable volume of 16 cubic meters, which is about the size of small bedroom, said Dasgupta. This will be the first time astronauts on the ISS will interact on an expandable inflatable habitat, and is a big step toward building manned habitats in space.

The cargo resupply mission to the International Space Station is the first since the company’s failed launch back in June when Falcon 9 burst into bits two minutes and 19 seconds into its supply mission. If all goes according to plan, SpaceX’s Falcon 9 will launch from Cape Canaveral Air Force Station in Florida on April 8, and researchers expect the Dragon will reach the ISS two days later. After a five-day period of thermal conditioning, BEAM will be extracted from the capsule’s trunk. The vessel is expected to return in May.