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An apparatus and method of measuring the mass of a test specimen located in a microgravity environment. The test specimen is attached to the free end of a cantilevered spring for joint vibration. The natural frequency of vibration of the spring and specimen are measured. The spring constant is calcu

An apparatus and method of measuring the mass of a test specimen located in a microgravity environment. The test specimen is attached to the free end of a cantilevered spring for joint vibration. The natural frequency of vibration of the spring and specimen are measured. The spring constant is calculated and compared with known masses having the same frequency and spring constant. When a match is found, the mass of the test specimen is known.

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1. An apparatus for measuring the mass of specimen in a microgravity environment, comprising:a test mass;a support member attached to the test mass, wherein the support member includes a tank enclosing a flexible member and having ports extending through wall portions of the tank on opposite sides o

1. An apparatus for measuring the mass of specimen in a microgravity environment, comprising:a test mass;a support member attached to the test mass, wherein the support member includes a tank enclosing a flexible member and having ports extending through wall portions of the tank on opposite sides of the flexible member;a spring attached at one end to the support member and attached at an opposite end to a rigid member, allowing the spring, support member and test mass to vibrate with one degree of freedom;a device for vibrating the spring, support member and test mass; anda sensor positioned to monitor the frequency of vibration of the spring, support member and test mass;whereby the mass of the test mass is determined from a comparison of frequencies of vibration of known masses. 2. The measuring apparatus according to claim 1 wherein the flexible member comprises a bellows and the test mass comprises a mass of fluid disposed in the tank on one side of the bellows. 3. The measuring apparatus according to claim 2, wherein a pressurized gas is disposed in the tank on a side of the bellows opposite from the mass of fluid, whereby the pressurized gas serves to press the bellows against the mass of fluid. 4. The measuring apparatus according to claim 3, wherein the pressurized gas comprises pressurized nitrogen. 5. A The measuring apparatus according to claim 1, wherein the spring comprises a vibrating mount having a base portion attached to the rigid member and a pair of arm portions rigidly attached to the tank, whereby the vibrating mount is free to vibrate in a manner similar to a cantilevered beam. 6. The measuring apparatus according to claim 5, wherein the sensor is attached to the support member. 7. The measuring apparatus according to claim 5, wherein the sensor comprises a strain gage mounted for joint movement with the support member. 8. An apparatus for measuring the mass of a test specimen, comprising:a support member, wherein the support member includes a tank enclosing a flexible member;the test specimen supported by the support member;a generally fork-shaped vibrating mount having a base portion fixedly attached to a rigid member and further having a pair of arm portions on an opposite end fixedly attached to the support member;a device for imparting vibration to the vibrating mount and the attached support member; anda sensor mounted on the tank for monitoring the frequency of vibration of the support tank and fluid, whereby the frequency of vibration of the test specimen is compared to frequencies of vibration of known masses to determine the mass of the test specimen. 9. The measuring apparatus according to claim 8, wherein the tank is located in a microgravity environment. 10. The measuring apparatus according to claim 9, wherein the flexible member divides the tank into two compartments, with one compartment containing the test specimen which comprises a mass of fluid and the other compartment contains a quantity of pressurized gas pressing the bellows against the mass of fluid. 11. The measuring apparatus according to claim 9, wherein the vibrating mount is made of 6061 Alloy having a modulus of elasticity E of approximately 6.83×10 10 Pa (or 9.9×10 6 psi). 12. The measuring apparatus according to claim 11, wherein the spring constant k of the vibrating mount is approximately,wherein L is the distance measured along the vibrating mount from the rigid member to approximately the center of the tank and I is the moment of inertia. 13. The measuring apparatus according to claim 12, wherein the moment of inertia I of the tank is approximatelywherein bxh is the rectangular cross section of the tank. 14. A method of determining the mass of a test specimen, comprising:attaching a tank enclosing a flexible member to a free end of a spring having an opposite end attached to a rigid member;depositing a test specimen in the tank;causing the test specimen and spring to vibrate at its natural frequency;monito ring the natural frequency f n of vibration of the test specimen and spring;calculating the spring constant k of a known mass having the same natural frequency; andcomparing known masses having approximately the same spring constant k and frequency of f n with the test specimen to determine the mass of the test specimen. 15. The method according to claim 14, including the step of maintaining the test specimen in a microgravity environment when monitoring the natural frequency f n of vibration. 16. The method according to claim 15, including the step of forming the spring in the shape of a elongated fork having one end attached to a rigid member and a pair of arms attached to the tank. 17. A method of determining the mass of a fluid test specimen while located in a microgravity environment, comprising:depositing the fluid test specimen in a tank, enclosing a flexible member, attached to a free end of a cantilevered spring having an opposite end attached to a rigid member;causing the fluid test specimen and spring to vibrate at its natural frequency;monitoring the natural frequency f n of vibration;calculating the spring constant k of a known mass having the same frequency of vibration; andcomparing known masses having approximately the same spring constant k and frequency of f n with the test specimen to determine the mass of the fluid test specimen. 18. The method of claim 17, including the step of forming the cantilevered spring in the shape of an elongated fork having a base portion attached to the rigid member and a pair of arms attached to the tank for joint vibration. 19. An apparatus for measuring the mass of a fluid test specimen located in a microgravity environment, comprising:a hollow tank having two compartments separated by a bellows member;the fluid test specimen deposited in one compartment and pressurized Nitrogen deposited in the second compartment;a generally fork-shaped, cantilevered spring vibrating mount having a base portion fixedly attached at one end to a rigid member and further having a pair of arm portions attached at opposite ends fixedly attached to the hollow tank;a device for repeatedly imparting vibration to the cantilevered spring vibrating mount and the attached hollow tank; anda sensor mounted on the hollow tank for monitoring the frequency of vibration of the hollow tank and fluid test specimen, whereby the frequency of vibration of the fluid test specimen is compared to frequencies of vibration of known masses to determine the mass of the fluid test specimen. 20. A method of determining the mass of a fluid test specimen located in a microgravity environment, comprising:depositing the fluid test specimen in a first compartment in a tank attached to a free end of a fork-shaped cantilevered spring having an opposite end attached to a rigid member;depositing pressurized Nitrogen gas in a second compartment separated from the first compartment by a flexible bellows;causing the fluid test specimen and cantilevered spring to repeatedly vibrate at its natural frequency;monitoring the natural frequency f n of vibration;calculating the spring constant k of a known mass having the same frequency of vibration; andcomparing known masses having approximately the same spring constant k and frequency of f n with the test specimen to determine the mass of the fluid test specimen. 21. The method according to claim 17, including the step of maintaining the test specimen in a microgravity environment when monitoring the natural frequency f n of vibration. 22. The method according to claim 20, including the step of maintaining the test specimen in a microgravity environment when monitoring the natural frequency f n of vibration.