File photo of a Dragon spacecraft on top of a Falcon 9 rocket before a previous mission. Credit: SpaceX

Ground teams at the Kennedy Space Center were packing last-minute cargo into a commercial Dragon supply ship Sunday, a day before the automated freighter is set for liftoff on top of a SpaceX Falcon 9 rocket on a two-day trek to the International Space Station.

The final biological research experiments, including a habitat with 20 mice, were to be installed inside the crafts pressurized cabin before technicians close the ships hatch and raise the Falcon 9 vertical on launch pad 39A.

Working under contract to NASA, SpaceX is set to launch its 12th cargo delivery flight to the space station at 12:31:37 p.m. EDT (1631:37 GMT), roughly the time the research labs ground track intersects Floridas Space Coast.

The 213-foot-tall (65-meter) Falcon 9 rocket will turn to the northeast to align with the stations orbit, kicking off a 42-hour pursuit with 6,415 pounds (2,910 kilograms) of experiments, food, supplies and spare parts to replenish the space labs research backlog and stockpiles.

That figure includes the weight of packaging needed to secure items stowed inside the Dragon spacecraft.

Weve loaded Dragon with 6,400 pounds of cargo, and Im happy to say 75 percent of that total mass is headed toward our research community, and our continued expansion of the research envelope on-board the International Space Station, said Dan Hartman, NASAs deputy space station program manager. So with the internal and external payloads going up, it sets a new bar for the amount of research that we were able to get on this flight.

SpaceX plans to recover the Falcon 9s first stage booster a few minutes after the launch. After detaching from the Falcon 9 second stage around two-and-a-half minutes into the mission, the 14-story booster stage will flip around and reignite a subset of its nine Merlin engines twice to return to Landing Zone 1 at at Cape Canaveral Air Force Station.

A final braking burn by the first stages center engine will slow the rocket just before touchdown. A four-legged landing gear will unfurl at the base of the booster as it settles on the concrete landing zone, located approximately 9 miles (14 kilometers) south of the rockets departure point at pad 39A.

If successful, Mondays landing will mark the 14th time SpaceX has recovered one of its Falcon 9 boosters intact, either at sea or on land. SpaceX aims to refit and reuse the rockets in a bid to make spaceflight less expensive, and two of the companys flown rockets have made second flights to date.

The rocket flying Monday is a new vehicle, but the first stages landing legs were previously-flown, according to Hans Koenigsmann, vice president of flight reliability at SpaceX.

The boosters touchdown will come moments before the Falcon 9s second stage engine delivers the Dragon cargo capsule to orbit. The freighter is scheduled to separate from the rocket around 10 minutes after blastoff, and the Dragons two power-generating solar panels will extended a couple of minutes later.

Multiple thruster firings by Dragons on-board rocket jets will begin steering the capsule toward the space station.

The automated rendezvous will conclude Wednesday, when the ship will approach the station from below, using lasers and a thermal imager for the in-orbit linkup.

Astronauts Jack Fischer and Paolo Nespoli will unlimber the stations Canadian-built robotic arm to grapple the free-flying spacecraft around 7 a.m. EDT (1100 GMT) Wednesday.

The robot arm will maneuver the Dragon to a berthing location on the space stations Harmony module for a month-long stay.

SpaceX and NASA have just one try to launch the station cargo freighter, or else face a delay that could stretch a week or longer.

Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy will release five small satellites during a spacewalk Thursday, and station managers want to ensure all of the spacecraft are well away from the complex when Dragon nears.

We do require good tracking on those, so we know where to help SpaceX fly Dragon when its approaching the ISS, Hartman said. Thats a big deal for us.

NASA does not want to launch the resupply mission and have the spacecraft loiter away from the space station until it is safe to approach. Some of the biological experiments inside Dragon are time-critical, including a nest of mice with limited food inside the capsule.

Could we loiter? Yes, at the expense of losing research because their samples have X amount of hours before they need to be offloaded and brought onto the station, Hartman said.

If the mission took off Tuesday, it would arrive at the space station Thursday, the same day as the spacewalk. Officials expect it to take several days to estimate the orbits of the five satellites released during the excursion, meaning the Dragon could not begin its two-day chase of the station until around Saturday, Aug. 19, Hartman said.

But there are other factors at play.

A NASA communications satellite is slated to launch from Cape Canaveral aboard a United Launch Alliance Atlas 5 rocket Friday. ULA has reserved a backup launch opportunity Saturday, and it takes a couple of days to reconfigure the U.S. Air Forces Eastern Range between rocket flights.

An Orbital ATK Minotaur 4 rocket is being prepped for launch Aug. 25 from Cape Canaveral. The range is required for the Minotaur flight, set to loft a military space surveillance satellite, and for a comprehensive launch rehearsal scheduled early next week, a few days after the Atlas 5 flight.

Whether SpaceX could find a hole in the jam-packed range schedule remains unclear.

Im cautiously optimistic for this launch opportunity, Koenigsmann said. Better one than none, I would say, so well see how it goes.

Forecasters predict a 70 percent chance of good weather for Mondays one-second launch window. Meteorologists will watch for rain and cumulus clouds in the rockets flight path.

Once Dragon arrives, the stations six-person crew will enter the capsule and unload the payloads inside, overseeing a multitude of biological experiments before the ships departure and return to Earth next month.

Twenty mice heading into space Monday will be examined after their return to the ground to aid researchers studying how spaceflight affects vision and movement.

Were looking at two different biomedical issues, said Michael Delp, principal investigator for the rodent research experiment from Florida State University. The first is visual impairment that occurs in some of the astronauts. To date, it only occurs in male astronauts, so were looking at a couple of different aspects of how visual impairment may occur.

The mice will come back to Earth inside the Dragon capsule alive, and SpaceX will hand over their transporters to scientists upon return to port in Southern California.

Researchers will examine the blood vessels inside animals eyes and the blood-brain barrier that regulates fluid movement inside the skull.

The second thing that well be doing is really looking at the brain circulation, and how that affects blood pressure within the skull, Delp said.

Part of the rodent research team will look at how an extended stay in the space stations weightless environment affects movement.

In microgravity, you have a fairly severe physical inactivity, and that can affect a number of the organ systems, such as muscle and bone loss, Delp said.

One focus of the study will be on how much cartilage in joints degrade after spending time in microgravity. Mice have an accelerated metabolism and undergo changes faster than humans, so a month on the space station is roughly equivalent to a three-year expedition by an astronaut, according to Delp.

The space station cargo mission will also help biologists investigating Parkinsons disease, a chronic neurological disorder that affects a million people in the United States, and about five million worldwide.

Although there are medications that ammeliorate the symptoms, we dont have any therapies that reverse or slow down the progression of the disease, said Marco Baptista, director of research and grants at the Michael J. Fox Foundation, which funded the station-bound experiment.

Scientists are sending a protein that causes Parkinsons to the station to measure how it grows without the influence of gravity. The protein, named LRRK2, could be targeted with drugs and therapies in Parkinsons patients if doctors understand it better.

The next breakthrough we need is the solving of the crystal structure of LRRK2, Baptista said. This is important for two reasons. First, it will allow us a better understanding of the biology of LRRK2 and secondly may help industry optimizing LRRK2 kinase inhibitors or develop novel ways to target LRRK2.

Growing the protein in microgravity will lead to bigger crystals, more regular crystallization and crystals with higher intrinsic order, said Sebastian Mathea, the lead scientist on the LRRK2 experiment from the University of Oxford.

With those crystals, we hopefully will be able to collect data that allow us to solve the three-dimensional structure of LRRK2, which hopefully will push forward the understanding of the onset of Parkinsons, Mathea said.

Another science team awaits results from an experiment probing how microgravity affects the growth of new lung tissue, specifically bio-engineered material tailored to repair damaged organs or reduce the chance of organ rejection in transplant patients.

Scientists have trouble managing the expansion of bio-engineered lung tissue on Earth. The tissue has trouble moving through structures designed to help shape it, and stem cells used to produce the tissue are slow to replicate, according to Joan Nichols, professor of internal medicine and infectious diseases and associate director of the Galveston National Laboratory at the University of Texas Medical Branch in Galveston.

Nichols said microgravity offers a more benign environment, aiding in cell dispersal to help form more uniform tissues.

Were getting two things out of this, she said. Were getting a better plan and a better strategy for how to manage production of tissues using microgravity environment, and were getting a model thats going to tell us what would happen in terms of lung repair on long-term spaceflight.

While astronauts get to work in experiments inside the stations lab facilities, the Canadian and Japanese robotic arms will remove a cosmic ray detector carried inside the Dragons external payload bay for mounting on a facility outside the stations Japanese Kibo module.

Derived from an instrument carried aloft on high-altitude balloons, the Cosmic Ray Energetics and Mass, or CREAM, payload will spend at least three years sampling particles sent speeding through the universe by cataclysmic supernova explosions, and perhaps other exotic phenomena like dark matter.

Scientists think the subatomic particles could hold the key to unlocking mysteries about the universe.

Four small satellites inside the Dragon capsule will be transferred inside the space station for deployment later this year.

The biggest of the bunch, named Kestrel Eye 2M, is a pathfinder for a potential constellation of Earth-imaging spacecraft for the U.S. military. About the size of a dorm room refrigerator, the Kestrel Eye 2M satellite was developed by the Armys Space and Missile Defense Command over the last five years.

While satellites the size of Kestrel Eye lack the fine imaging capability of large commercial and military spy satellites, they cost significantly less and could be spread around the planet in fleets of dozens or more.

Battlefield troops could connect with one of the satellites as it soars a few hundred miles overhead, ask it to take a picture of a nearby target, then receive the image, all within a few minutes.

The concept is to have warfighters to task and receie data directly from the satellite during the same overhead pass, said Wheeler Chip Hardy, the Armys Kestrel Eye program manager. The objective Kestrel Eye imagery data can be downlinked directly to provide rapid situational awareness to our Army brigade combat teams in theater without the need for continental United States relays.

From the space stations altitude around 250 miles (400 kilometers) up, Kestrel Eye 2Ms optical camera will be able to spot objects on Earths surface about the size of a car.

The Army has not approved development of further Kestrel Eye satellites. The demo craft set to launch Monday will be employed in military exercises with Pacific Command over the next few years, and Pentagon officials will evaluate its usefulness before deciding whether to press on with the program.

Three CubeSats will also be ferried to the space station for release from a ground-commanded deployer in the coming months.

The ASTERIA mission, developed by a team at the Massachusetts Institute of Technology and NASAs Jet Propulsion Laboratory in California, seeks to test miniature telescope components that could be used in future small satellites to observe stars and search for exoplanets. ASTERIA is about the size of a big shoebox and weighs around 26 pounds (12 kilograms).

Astronomers and engineers want to know if a CubeSat like ASTERIA can hold pointing to the precision necessary for stellar observations, and designers will also measure the performance of the focal plane inside an on-board telescope.

The Dellingr project spearheaded by NASAs Goddard Space Flight Center in Maryland aims to prove out a new type of microsatellite design that is more reliable than conventional CubeSats.

Around the same size as ASTERIA, the Dellingr CubeSat, named for the mythological Norse god for the dawn, took around three years to design, build and test. Officials said the effort was not always easy, and managers had to define a balance between affordability and reliability.

Engineers tried using commercially-available components and software, but testing revealed many of the parts were inadequate for the level of reliability sought for Dellingr, which carries a sensor suite to study the suns influence on Earths atmosphere.

Its a new way of doing things, said Chuck Clagett, Dellingr project manager at Goddard. We were applying old ways to doing things to an emerging capability and it didnt work very well.

But officials said the extra testing paid off, and Dellingr is now ready to fly after helping reduce the risk of unforeseen problems on future missions NASA has approved work on a follow-up CubeSat incorporating Dellingrs design and lessons to make measurements of Earths ionosphere.

Another CubeSat named OSIRIS-3U from Penn State University launching Monday will study space weather.

Working in coordination with the Arecibo Observatory, a giant radar antenna in Puerto Rico, OSIRIS-3U will fly into a region ionosphere heated to simulate the conditions caused by solar storms.

OSIRIS-3U will collect data on the electron density, temperature, and content in the region of space stimulated by radar emissions, according to a fact sheet released by NASA.

The Dragon spacecraft is scheduled to depart the space station Sept. 17, bringing home more than a ton of research specimens and other gear for a parachute-assisted splashdown in the Pacific Ocean southwest of Los Angeles.

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SpaceX rocket readied for space station resupply run - Spaceflight Now