I recently heard of an experiment to measure changes in the trajectory of spacecraft as evidence of gravity waves. Apparently this method is more sensitive than laser interferometer-type experiments.

Here's an idea: Minute rest-mass fluctuations could also cause changes in trajectory via the equation for momentum:

p = m * v

where,
p = momentum
m = rest mass
v = velocity

If mass increases or decreases, velocity has to compensate to prevent violation of conservation of momentum.

If we find a very fast-moving spacecraft's trajectory is being purturbed in some unpredictable manner then we might take is as evidence of rest-mass fluctuations.

Also, recent experiments with superconductors might suggest that superconduction may effect a slight change in rest-mass. I wonder if we could induce the same effect in a spacecraft and force some change in its trajectory. If we can demonstrate this effect then we may have invented a reactionless drive.

To wit, "statistics do not explain transient effects".