A practical and lightweight instrument for measuring the mass of astronauts under microgravity conditions is proposed. The principle of our 'space balance' is as follows. Connect the subject astronaut to the base with a rubber cord. Use a force transducer to measure the force acting on the subject and an optical interferometer to measure the acceleration of the subject. The subject's mass is calculated as the force divided by the acceleration, i.e. M = F/a. For the proof-of-concept ground model developed for this paper, linear motion of the mass with a negligible external force was achieved using an aerostatic linear bearing.

https://iopscience.iop.org/article/10.1088/0957-0233/17/10/024/pdf

Instrument for measuring the mass of an astronaut

A method for efficiently and accurately measuring mass under conditions of weightlessness is proposed using the law of conservation of momentum. In this method, the velocities of two different uniform motion states of an object and the reference mass are measured highly accurately using an optical interferometer. For the preparatory experiments on earth, an instrument, with which linear motion of constant velocity is realized using pneumatic linear bearings, is developed. The combined standard uncertainty in mass measurements from 4 to 18 kg by a single collision is estimated to be about u c = 0.012 kg, which corresponds to 0.07% (7 x 10 -4 ) of the maximum value of 18 kg. For a mass-measurement instrument employed under microgravity conditions, a design for the instrument and a measurement procedure are proposed.

Balance for Measuring Mass Under Microgravity Conditions

An improved prototype of the space scale, which has been proposed as a practical and lightweight instrument for measuring the body mass of astronauts under microgravity conditions in the International Space Station (ISS), has been developed A prominent feature of the proposed instrument is the use of a bungee cord as the source of force This results in a simple, lightweight, and compact structure of the instrument It also results in a large displacement during the measurement and then the reduction of the effect of change in subject posture The feasibility of the prototype design has been evaluated by quantifying the body mass of a human subject in a parabolic flight test The present and future statuses of the space scale are discussed

Instrument for Measuring the Body Mass of Astronauts Under Microgravity Conditions

A prototype instrument for measuring astronaut body mass under microgravity conditions has been developed and its performance was evaluated by parabolic flight tests. The instrument, which is the space scale, is applied as follows. Connect the subject astronaut to the space scale with a rubber cord. Use a force transducer to measure the force acting on the subject and an optical interferometer to measure the velocity of the subject. The subject’s mass is calculated as the impulse divided by the velocity change, i.e., M=∫Fdt∕δv. Parabolic flight by using a jet aircraft produces a zero-gravity condition lasting approximately 20s. The performance of the prototype space scale was evaluated during such a flight by measuring the mass of a sample object.

Mass measuring instrument for use under microgravity conditions.

A practical, high-precision method for measuring the mass of an astronaut under microgravity conditions is proposed. Using an instrument called the “Space Scale”, the velocities of a target object and a reference mass are measured with high accuracy by optical interferometry. The two are connected by a linear ball bearing and have separate linear-motion states, with some acceleration due to friction in the linear ball bearing. For this paper, a ground instrument was developed in which linear motion of the whole mechanical system is achieved with negligible external force by means of a pneumatic linear bearing. The effect of linear ball bearing friction that involves the target object and the reference mass is theoretically negligible, as we proved experimentally in this study. We conclude that an operational model for in-orbit use, which takes advantage of an optical interferometer, would be extremely compact and accurate.

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Kaname Nagata

Papers

Mass-measurement under weightless conditions by the frequency-controlled method