Flattening spacetime near the Earth
Experimental regions where all forces are minimized are desired for many types of space experiments such as those involving gravity measurements and materials processing. In a free-fall orbit, the gravity acceleration force of the Earth is canceled to first order by the orbital motion. The cancellation, however, is perfect only at the center of mass of the freely falling object. At the other points in the object there will be accelerations induced by the gravity gradient tides of the Earth. These can cause acceleration forces of 10/sup -7/ m/sec/sup 2/ (10 nanogravities) at a distance of only 3 cm from the center of mass and proportionately larger accelerations at greater distances. We show that if we place six 100-kg spheres in a ring whose plane is orthogonal to the local vertical and whose center is at the center of mass of the experiment, the gravity attraction of the spheres will produce a counter-tide that can reduce the Earth tide accelerations by factors of 100 or more in significant experiment volumes. We give an example where we produced calculated acceleration levels below 10/sup -11/ m/sec/sup 2/ (1 picogravity) over a disk-shaped experiment volume 30 cm in diameter and 20 cm thick in a geostationary orbit space laboratory. In materials-processing experiments, the acceleration levels attainable will be limited by the self-gravity of the material being processed.The self-gravity of a disk-shaped sample can be reduced by first using ''guard rings'' and ''guard caps'' to smooth out edge effects. Then a combination of gravity gradients from two massive spheres and rotation of the sample can be used to null the self-gravity everywhere inside the sample disk.
- Research Organization:
- Hughes Research Laboratories, 3011 Malibu Canyon Road, Malibu, California 90265
- OSTI ID:
- 6686825
- Journal Information:
- Phys. Rev. D; (United States), Vol. 26:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
GRAVITATIONAL INTERACTIONS
SPACE-TIME
EARTH PLANET
GRAVITATIONAL FIELDS
GRAVITY WAVES
RIEMANN SPACE
BASIC INTERACTIONS
INTERACTIONS
MATHEMATICAL SPACE
PLANETS
SPACE
657003* - Theoretical & Mathematical Physics- Relativity & Gravitation
645400 - High Energy Physics- Field Theory