Gill, D. | Search NASA

NASA NTRS1988

Requirements and an approach for coating the Gravity Probe B gyroscope rotor

A process to coat a quartz gyroscope rotor uniformly with superconducting niobium as part of a NASA sponsored experiment to test general relativity is described. The requirements for uniformity, film adhesion, and superconducting properties of the niobium thin film rotor coating are discussed. A uniformity of 1.5 percent (peak to valley) (38 nm) with good adhesion, no pinholes larger than 0.25 mm, transition temperature of 9.8 K, and the ability to survive repeated thermal cycling to 4.2 K have been achieved. Problems concerning abrasive damage and electrical arc damage during earthbound testing have been observed. Many hours of ground-based gyro operation demonstrate the applicability of this approach to rotor coating.

Gill, D.↗

NASA NTRS1986

Hardware development for Gravity Probe-B

Gravity Probe-B (GP-B), also known as the Stanford Relativity Gyroscope Experiment, will test two fundamental predictions of Einstein's General Theory of Relativity by precise measurement of the precessions of nearly perfect gyroscopes in earth orbit. This endeavor embodies state-of-the-art technologies in many fields, including gyroscope fabrication and readout, cryogenics, superconductivity, magnetic shielding, precision optics and alignment methods, and satellite control systems. These technologies are necessary to enable measurement of the predicted precession rates to the milliarcsecond/year level, and to reduce to 'near zero' all non-General Relativistic torques on the gyroscopes. This paper provides a brief overview of the experiment followed by descriptions of several specific hardware items with highlights on progress to date and plans for future development and tests.

Bardas, D.↗