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Introduction
Following on the success of the Phase 1 of the Robotic Refueling Mission, our project continues work on studying technology to perform the repair and upgrading of satellites in space.  One key technology for this kind of mission is how to handle a flexible fuel hose.

In our initial handling of a sample hose, we realized that it could be easily damaged if handled incorrectly.  We decided to test technology and procedures associated with handling such an item, and I came to head up various parts of this work, including the project to fly a sample hose on a zero gravity flight to truly see how this object behaves in the environment of space.  

Investigation of the Flexible Hose
We started the investigation in the Spring of 2012 by using a robot in our lab equipped with its force-torque sensor to better understand how to handle the hose without breaking it.

Perhaps not surprisingly, these initial tests, called "Test 5.2" inside our organization, showed us that the gravitational pull of the weight of the hose really affects how the hose handles.  In order to investigate further if our handling procedures work correctly, we needed to offload this gravitational force.  Just like in astronaut training, which occurs in a large water tank, we decided to take our next steps in water.


For tests in the bouyancy benefits of water, we went to the nearby University of Maryland Space Systems Laboratory in early 2013.  The internal name for these round of tests was "Test 5.7".  In order to perform the tests we modified the frame above to only include the start and endpoints of the hose, rather than emulate the volumetric space of the two vehicles.

Our conclusions with the 5.7 test were partially hampered by the damping effects of the water.  So in order to address this problem we were granted a series of test flights on the zero gravity plane from gozerog.com.  This flight was funded by NASA's Office of Chief Technology via the Flight Opportunities Program.


In order to perform the tests on the zero gravity airplane, we further shrank the fixture holding the hose.  From the large frame representing the entire two satellites in 5.2, to the smaller one showing only the start and end point in the water test of 5.7, to now a minimal fixture as shown below. The reason is that the plane is flown down the zero G parabola by the pilot, and you only experience true zero gravity if you are floating in the plane.  So our fixture needs to 'free float', and as a result needs to be as small and light as possible.

In order to gather data on the behavior of the hose, the fixture has a mechanism that gives it a 'push', and we then use motion capture cameras to capture the resulting motion of the hose.