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Fisher Space Systems LLC

Space Track Launch System

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Task 1: Effective Elastic Modulus

Objective: Determine the effective elastic modulus of an inflated Kevlar beam. To garner a working knowledge of inflated beam technology.

Discussion: The critical buckling load of the inflated beam is the primary design driver for the Space Track Launch System tower. The Euler equation for the critical buckling load is directly proportional to the elastic modulus of the material. Based on the literature, the elastic modulus of an inflated beam is linear with pressure and equal to the material modulus at a certain inflated pressure.

Results: For the Kevlar/Mylar beam tested, the elastic modulus was independent of pressure. The elastic modulus of the beam was an order of magnitude less than the elastic modulus of the Kevlar material. Further review of the literature showed that the elastic modulus is linear with pressure only for certain materials (e.g. Dacron) and independent of pressure for others (e.g. Nylon). In addition to the elastic modulus, the shear modulus and the geometry of the beam may have a significant contribution to the critical buckling load for a Kevlar/Mylar beam. Read ETR 20130510 in the reports section for further information on the test procedure and results.

Task 2: Elastic and Shear Modulus of an Inflated Kevlar Beam

Objective: Determine the material modulus of an inflated Kevlar beam as a function of pressure and geometry of the beam.

Discussion: To scale the inflated beams from the laboratory to the field requires a better understanding of the material moduli and their relationship to the critical buckling load. The critical buckling load of the inflated beam is the primary design driver for the Space Track Launch System tower. In Task #2, the elastic modulus and shear modulus will be measured as a function of pressure and radius of the beam. The results will be used in theoretical relationships between elastic modulus, shear modulus, and geometry for the critical buckling load of an inflated beam.

Results: Delayed




 Task 3: Critical Bending Moment - Single Beam

Objective: To investigate the critical bending moment as defined by the Euler beam theory for a single inflatable beam made of Kevlar and pressurized with air.

Disscussion: Kevlar is suitable for a proof of concept system. The beam will be approximately 1.5 m long and 5 cm in diameter giving it an L/D of 30 which means that the Euler beam theory applies. The beam will be inflated and run through a series of test to determine the critical bending moment of a single inflated beam.

Results: Delayed







Task 4: Critical Bending Moment - Multi-Beam

Objective: To investigate the critical bending moment of inflated multi-beams.

Disscussion: Three identical beams will be fabricated and arranged in a tripod type configuration as shown in the diagram. The multi-beam arrangement will go through the same series of test and compared with theory.


Results: Delayed
Updated Jun 2013