Ritsu Watanabe

Bio: Ritsu Watanabe is an academic researcher. The author has contributed to research in topics: Circular motion & Mass flow controller. The author has an hindex of 2, co-authored 3 publications receiving 33 citations.

Balance for Measuring Mass Under Microgravity Conditions

Abstract: 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.

Liquid helium transfer using a mass-flow controller

Abstract: An automated liquid helium transfer method using a mass-flow controller, by means of which an empty cryostat at room temperature can be filled with liquid helium without thermal shock, has been developed. Before liquid helium collection is initiated, mass flow is controlled to be constant. After the start of liquid helium collection, mass flow is controlled so that the differential pressure of the empty cryostat against the storage Dewar containing the liquid helium is of the proper value to overcome the height difference due to the transfer tube. A mass-flow controller, a vacuum pump, a differential pressure sensor, a liquid helium level sensor and a computer with suitable software are required to replace the conventional manual transfer by this method.

Measurement of force acting on a moving part of a pneumatic linear bearing

Abstract: A method for evaluating the components of the force acting on a moving part of a pneumatic linear bearing is proposed. The total force acting on the moving part is accurately measured as the inertial force using an optical interferometer. Then, the components of the force, such as the force component depending on position, the force component depending on velocity, and the force component depending on tilt angle, are evaluated using the least-squares method. In the experiment, the total force acting on the moving part is measured with the standard uncertainty of approximately 0.001 N, which corresponds to approximately 0.003% (30 ppm) of the gravitational force acting on it (M=4.119 kg) of approximately 40 N (40 N). The experimentally evaluated values of these force components well coincide with the theoretically expected values.

Instrument for measuring the mass of an astronaut

Abstract: 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.

Instrument for Measuring the Body Mass of Astronauts Under Microgravity Conditions

Abstract: 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

Mass measuring instrument for use under microgravity conditions.

Abstract: 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.