Purdue University

ADVANCING DIAPHRAGM MODELING TECHNOLOGY FOR PROPELLANT MANAGEMENT (2016)

A common method of controlling liquid propellants in missions with high accelerations is the tank diaphragm (or bladder). The diaphragm is a flexible solid barrier separating the liquid from the pressurant gas. Motion of the liquid and diaphragm during spacecraft accelerations from maneuvering, docking, or similar, needs to be predicted during design. Fully coupled solid-dynamics and liquid-dynamics modeling for design is expensive. If one knew how to design into stiffness-dominated or a fully flexible regimes, then modeling and design would be simpler, cheaper, faster. This experiment seeks to further the work at Purdue to define a dimensionless parameter which can be used to assure that one is designing into the simper regimes.

The experiment will have two parts: static (actually g-jitter excitation) testing and dynamic testing. For each portion, five transparent acrylic spherical tanks with internal diaphragms will be tested. Each tank will be tested at five different fill levels using water as the liquid. For the dynamics portion, the tanks will be perturbed using a spring and drawer-slide system for small linear motions. For both static testing and dynamic testing, cameras will monitor the motion of the diaphragms and post-flight analysis produces the necessary evaluations of diaphragm motions.

P.I. Steven Collicott monitors experiment during a zero gravity parabola.

BUBBLE DETACHMENT FOR ENHANCED HEAT TRANSFER SURFACE GEOMETRIES IN MICROGRAVITY (2016)

This experiment will examine the formation, growth, and detachment of vapor bubbles during boiling on four different surface geometries in microgravity. Flow boiling heat transfer provides high rates of heat transfer such that the mass and volume of the heat transfer system can be minimized and still meet the heat transfer requirements. The investigation of flow boiling systems in microgravity is relevant to the design of space-flight heat transfer systems in addition to several applications on earth.

This experiment builds on the knowledge from an experiment submitted and flown in 2009-2010 with the RGEFP. The previous experiment also studied the vapor bubble growth and detachment along textured surfaces in microgravity. A significant difference between the two experiments lies in the growth of bubbles by heat transfer rather than vapor injection. By opting to use heat transfer to form and grow the bubbles, the volumetric growth rate in our experiment will depend on the surface geometry rather than fixing the bubble growth rate as a constant for all surfaces.

Students observe data on Bubble Detachment experiment during zero gravity parabola.

Purdue students and P.I. Steven Collicott verify experiment set up prior to first mission.