After a successful demonstration flight in September, the next Orb-1 mission is scheduled to launch on an Antares rocket in January 2014 as part of the NASA Commercial Resupply to Station contract.
The first operational delivery flight to actually carry supplies and experiments, Orbital Sciences Corporation’s unmanned cargo freighter Cygnus will loft approximately 3,217 pounds (1,459 kg) of science equipment, spare parts and supplies to the International Space Station (ISS) for NASA.
Along for the ride with this payload will be the ISS Fluid Slosh experiment, a Space Technology Mission Directorate, Game Changing Development Program project dedicated to improving our understanding of how liquids behave when there is little to no gravity.
“Modern computer models try to predict how liquid moves inside a propellant tank,” said NASA’s Brandon Marsell, co-principal investigator on the Slosh Project. “Now that rockets are bigger and are going farther, we need more precise data. Most of the models we have were validated under 1 g conditions on Earth. None have been validated in the surface tension-dominated microgravity environment of space.”
The proposed research provides the first data set from long duration tests in zero gravity that can be directly used to benchmark computational fluid dynamics models, including the interaction between the sloshing fluid and the tank/vehicle dynamics.
Powerful rockets use liquid fuel to bring satellites into orbit, and are subjected to varying forces as they are propelled forward. But computer simulations may not accurately represent how liquids behave in low-gravity conditions, causing safety concerns. The Slosh experiments improve these models, and thereby improve rocket safety, by measuring how liquids move around inside a container when external forces are applied to it. This simulates how rocket fuels swirl around inside their tanks while a rocket moves through space.
To explore the coupling of liquid slosh with the motion of an unconstrained tank in microgravity, NASA’s Launch Services Program (LSP) teamed up with NASA’s Game Changing Development (GCD) Program, the Florida Institute of Technology (FIT), and the Massachusetts Institute of Technology (MIT) to perform a series of slosh dynamics experiments in the ISS using the Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) platform. The SPHERES test bed provides a unique, free-floating instrumented platform on ISS that can be utilized in a manner that would solve many of the limitations of the current knowledge related to propellant slosh dynamics on launch vehicle and spacecraft propellant tanks.
“It was a complex and detailed process to bring this concept to fruition,” said Charlie Holicker, an FIT student who worked on the physical design of the experiment and aluminum machining. “The data that this experiment will gather sets the foundation for all long-term space flight involving liquid fuels. It was an honor to be a part of something that will have such a great impact in the exploration of space.”
Rich Schulman, an FIT student involved in the Slosh experiment since its beginning, said, “One huge benefit for the students working on this project is seeing firsthand the requirements for developing a payload for the ISS. Having gone through this process successfully, the students involved can effectively build future payloads or projects at the same standard.”
Many satellites launch on rockets powered by liquid propellants, and improved understanding of these propellants could enhance efficiency, potentially lowering costs for industry and taxpayer-funded satellite launches.
Denise M. Stefula
NASA Langley Research Center