The next SpaceX resupply launch to the International Space Station, scheduled for Dec. 4, will bring a host of science material to astronauts living and working on the orbiting laboratory. 

This flight, called CRS-19, marks the 19th mission for SpaceX under its commercial cargo resupply services contract with NASA, with launch scheduled for 12:51 p.m. EST (1751 GMT). Perched atop a Falcon 9 rocket will sit a cargo Dragon capsule filled with more than 5,700 lbs. (2,585 kilograms) of supplies, including more than 2,100 lbs. (952 kg) of science equipment. 

"The Dragon spacecraft is an important component of space station delivery," Bryan Dansberry, an associate administrator of science at NASA, said during a news conference held Nov. 20. The scientific cargo will support a host of experiments across Expeditions 61 and 62 about topics including seed germination, combating muscle wasting and a new way of stowing tools on the station. 

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Seed germination  

Anheuser-Busch and its Budweiser brand are sending the team's fourth experiment to the space station to evaluate how seeds germinate in the harsh environment of space. 

"Germination is a key step in the life cycle of any plant," Gary Hanning, director of global barley research for Anheuser-Busch explained during the same news conference. "This investigation will look at environmental impacts that affect seed germination." 

Researchers on the project want to better understand why different plant genes are turned on and off in space than on the ground. To that end, the scientists will send up barley seeds to germinate on orbit before their growth is halted during a process known as malting. 

Malting, a three-step process that turns barley into malt, which is one of the main ingredients of beer and is responsible for the taste and color variations that give each beer its unique flavor profile. Malting involves hydrating, germinating and drying the grain. "It's all about moving air, moving water and controlling temperature," Hanning said.

Once the experiment is over, it will come back to Earth, where Budweiser scientists will analyze the malt quality to better understand how the plants germinated in space. Researchers will also compare gene expression in space plants to that of plants here on Earth that have been exposed to environmental stressors like extreme heat and cold. 

Hanning said that this research is important to the future of space travel as it will help botanists better understand how plants grow in microgravity and could help researchers figure out the best ways to grow crops in space. 

"As we move farther and farther from Earth into space, we need to understand how plants will react," Michael Roberts, interim chief scientist for the International Space Station's national laboratory, said during the same briefing. "We need to develop new ways to propagate plants for food consumption."

Mighty mice 

Also on board the Dragon capsule will be a group of 40 mice that will allow researchers to investigate muscle degradation in space. Se-Jin Lee, a professor at the Jackson Laboratory and University of Connecticut School of Medicine, and his team are sending a group of moustronauts to the space station.

Those mice don't have a key protein called myostatin, which inhibits muscle growth. "When we engineered the mice to lack myostatin, they grew to twice their normal size," Lee said during the news conference. "We call them mighty mice."

Myostatin can be used to treat a variety of muscle-wasting disorders, Lee said, and microgravity mimics the type of human muscle loss associated with common disorders seen on Earth. So the team wants to test whether blocking myostatin in orbiting mice can prevent muscle loss in space. 

The mice visiting the station are divided into five groups of eight: a group of mighty mice with no myostatin, a control group of normal lab mice, a group given a compound that blocks myostatin, and two groups that won't experience any treatment in space. 

All 40 mice are due to return alive, at which point the last two groups will be given a myostatin blocker. Lee and his colleagues hope that this format will let them determine whether the mice can recover any of the muscle mass they lose in space. 

The team is using an experimental myostatin blocker that also blocks another protein called actavin, which regulates bone mass and increases bone density — and that means it could counteract another key side effect of spaceflight. 

"Astronauts lose muscle and bone mass, so anything to prevent this can help maintain astronauts during space flight," Lee said. "It's also a huge problem for people here on Earth, in both children and adults. We hope to test a therapeutic strategy that will help [people with] lots of different conditions."

Extreme physics 

The cargo shipment will also include a new science package for NASA's Cold Atom Lab (or CAL for short), which has been in orbit since May 2018. CAL produces clouds of ultra-cooled atoms called Bose-Einstein condensates, which are just a fraction of a degree warmer than absolute zero. The ultra-cold temperatures act like a magnifying glass on atoms in a Bose-Einstein condensate, giving researchers a chance to better study the quantum characteristics of this material. 

Here on Earth, gravity affects Bose-Einstein condensates in such a way that their quantum characteristics can only be observed for a fraction of a second; however, in microgravity, these properties can be observed for up to 10 seconds. This gives researchers more time to study the atoms' exotic physical properties and how they interact with each other. 

According to Robert Thompson, CAL project scientist at NASA's Jet Propulsion Laboratory, this Dragon launch will send the lab a new science package that will help researchers in their quest to probe fundamental theories of gravity. 

"We're extremely excited to fly our first upgrade to the CAL," Thompson explained during the pre-launch briefing. "[The Dragon] will deliver a new module called Science Module 3. This will be the heart of the CAL instrument."

CAL is operated from the ground but requires astronaut time for any maintenance or upgrades, including this one.

"One of the things we're going to be doing with [the new module] is a test of Einstein's equivalence principle," Thompson said, referring to the idea that gravity should affect all forms of matter in the same way. "If that breaks down, we need new physics rules." 

He explained that Galileo performed a famous experiment to test this same theory. Galileo dropped two different items off the Leaning Tower of Pisa to show that they fell at the same rate, no matter the material. Thompson says that with CAL, researchers will do a similar experiment on station, using rubidium and potassium atoms, which are easy to work with and have a similar atomic structure. "With our equipment, we can measure precisely how far they move to a few nanometers," he said. "We will try to show that they fall at the same rate." 

The space station will also receive a small, portable tool shed as part of its next cargo shipment. The structure will serve as a long-term storage option for robotic equipment that will be mounted on the station's exterior but remain safe from the harsh environment of space. Essentially a miniature two-car garage, the storage facility will protect twin robotic leak detectors that act as bloodhounds to sniff out potential gas leaks that can develop on the orbital outpost. 

The station's cooling system, a network of thousands of feet of exterior plumbing, relies on ammonia to function properly, according to Mark Neuman, a mechanical systems engineer at NASA's Goddard Space Flight Center in Maryland.

Small leaks are common and typically occur at joints or because of micrometeor impacts, Neuman said. There's typically no safety risk to the crew, but in the past, astronauts have had to perform spacewalks to search for the tiny leaks.

Instead, in 2015 NASA launched the first Robotic External Leak Locator, which can zero in on the ammonia source, reducing the time the crew spends searching for leaks. "The original version was so useful that a second one was built," Neuman said during the briefing. "That version arrived on station in April, and is currently stored inside space station." 

Both leak-locating robots will be installed in the storage locker once it's unpacked from Dragon's trunk after arrival. 

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Expanding the fleet 

The star of the upcoming launch will be a shiny, new Falcon 9 booster, internally dubbed B1059.1. Unlike the Falcon 9, this Dragon has flown before; CRS-19 will be the spacecraft's third trip to the space station. 

The next flight for SpaceX is scheduled for less than two weeks later as a veteran booster makes its third flight to loft the JSCAT-18 communications satellite co-owned by Japanese and Singaporean companies. 

According to Dansberry, the CRS-19 Dragon capsule will return to Earth about a month after launch, carrying with it 1,800 lbs. (816 kg) of science samples and other materials. 

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