NASA’s Gravity Probe B

Gravity Measurement

NASA launched Gravity Probe B in 2004 using utra-precise sphere-shaped gyroscopes to measure Two Einstein Space-Time Theories.

The main difference in our ISS Falling Bodies Gravity Test is the spheres we will release are allowed to be acted upon by all natural forces as they accelerate in “free-fall” motion.

In NASA’s Gravity Probe B experiment the spheres were gyroscopes (spun mechanically) and enclosed in a spacecraft to measure gravity, shielded from the effects of all other forces.


Sphere materials

Magnetic Permeability

We need to select materials with varying magnetic permeability.

Here is where we will have the spheres precisely manufactured.


1. AISI 1006 Carbon Steel (high permeability)

2. Alloy Steel 52100 (not as high permeability)

3. Aluminum Bronze C95400 (low permeability)

4. Titanium (zero permeability)

5. Neodymium (high strength magnet)

6. Acrylic (PMMA):  (zero permeability) containing a cluster of 13 Neodymium (high strength magnets)