Mass measurement under weightless conditions

• Published in: Review of scientific instruments 1999-01, Vol.70 (1), p.111-113
• Main Authors: Fujii, Yusaku, Fujimoto, Hiroyuki, Namioka, Shuhei
• Format: Article
• Language: English
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.1149550

A method for quickly and accurately measuring mass under weightless conditions is proposed using the principle of action and reaction, in other words, the law of conservation of momentum. In this method, the velocities of two different uniform motion states of the object and the impulse, that is, the time integration of the impact force, between them are measured, and then the mass of the object is determined. The velocity can be easily measured highly accurately using an optical interferometer. For the preparatory experiments on earth, an instrument with which linear motion with constant velocity is realized using an air cushion linear bearing and which detects impact using a force sensor, has been developed. The relative combined standard uncertainty in mass measurements from 2 to 11 kg in a single impact measurement is estimated to be about u c,r =0.6×10 −2 (0.6%). For more accurate measurements, we propose an improved method in which the impulse is measured using the reference mass and its momentum change instead of the force sensor which is the biggest error source in the experiments.