Measuring and testing – Center of gravity; turning moment; metacentric height
Patent
1989-03-27
1991-08-13
Ruehl, Charles A.
Measuring and testing
Center of gravity; turning moment; metacentric height
G01M 110, G01M 112
Patent
active
050386042
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns apparatus for determining the mass-related characteristics of a vertically disposed body such as an artificial satellite, for example, which is large, fragile and difficult to manipulate.
The methods of launching a satellite, placing it in orbit and positioning it in orbit require a knowledge of its mass, the position if its centre of gravity and its moments of inertia, these being generally referred to as its "mass-related characteristics". In practice these characteristics correspond to the satellite with its payload in a stowed configuration but without any fuel (hence "dry").
In the current state of the art these characteristics are each determined by means of a specific device which for the satellite as a whole multiplies the risk of damage due to handling and increases the duration and overall cost of the measurements.
In particular, the mass is often measured by weighing and the longitudinal moment of inertia is measured by placing the satellite vertically and centering it on a table mounted to oscillate about a vertical axis on a base resting on the ground. A device marketed by the SCHENCK company under the reference M7 may be used for this purpose. Measuring the transverse moments of inertia requires the satellite to be disposed horizontally using complex machinery with significant mass and inertia. The presence of this machinery during measurement of the transverse moments reduces the accuracy of the inertia measurements relative to a given transverse axis and reduces the number of measurement axes that can be used to two, which is insufficient for determining the transverse central inertia ellipse.
The present invention is directed to alleviating these disadvantages by making it possible to measure all the mass-related characteristics of a satellite or a like object in a constant single orientation, preferably a vertical disposition, with a single manipulation.
The measuring device in accordance with the present invention essentially comprises two superposed devices constituting oscillating free pendulums with respectively vertical and horizontal axes.
The invention proposes measuring apparatus for determining the mass, the position of the centre of gravity and the moments of inertia of a body held in a predetermined constant orientation, of the kind comprising, carried by a base, a receiving table for the body mounted to oscillate relative to a substantially vertical axis normal to the table to either side of a stable equilibrium angular position to which the table is returned elastically by return means, the table and the base being provided with a sensor for sensing the angular position of the table relative to the base and locking elements for locking the table to the base, characterised in that the base is carried by a movable structure carried by a stand and mounted to oscillate relative to a horizontal axis intersecting said vertical axis at a height adjustable to either side of a stable equilibrium angular position in which the normal axis of the table is vertical and towards which the mobile structure is returned elastically by second return means, the stand and the movable structure being provided with a system for sensing the angular position of the movable structure relative to the stand, locking elements for locking the movable structure relative to the stand in a stable equilibrium position and means for adjusting the height of the instantaneous horizontal oscillation axis, the apparatus being further provided with means for positioning and locking the body relative to the movable structure in a plurality of angular positions.
As will emerge hereinafter apparatus of this kind can be used, without any intermediate manipulation of the body, to measure its mass, to determine the position of its centre of gravity and to measure its longitudinal moment of inertia and its transverse moments of inertia.
The body is preferably mounted on the table so that one of its main axes of inertia is coincident with the axis normal to the table. The body is advantageous
REFERENCES:
patent: 3040563 (1962-06-01), Eckles et al.
patent: 3418847 (1968-12-01), Nantz
Articles Moments of Inertia and Mass Centre Coordinates Determn. Rig--Uses Period of Free Oscillations to Fix Moment of Inertia, CONS ROAD RES 03.02.83-SU-548506 CSRO S02 85-030064/05 SU 1097-899-A.
Aerospatiale - Societe Nationale Industrielle
Ruehl Charles A.
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