by John Schnurer
The Gravity Society
Post Office Box CN 652
Yellow Springs, Ohio
We have recently succeeded in partially reproducing the weak gravitational shielding effect described by Podkletnov. Our experimental setup was designed to eliminate, as far as is possible, any non-gravitational disturbance, and to show a precise temporal correspondence between actions taken on the HTC disk and the weight reduction of the sample/proof mass. Although the observed weight reduction was large enough to be clearly distinguished from the noise (of the order of 1 % or more), it was detected only in transient form, lasting up to ca. 3 s. This happened because the weight reduction was coincident with the superconducting transition of the HTC disk, which occurred quite rapidly when the disk warmed up over its critical temperature.
Our earlier experimental setup is described in the Appendix of the old version of report gr-qc/9612022. An improved setup allowed us to run more than 400 trials with an heavier proof mass (a glass rods bundle - total weight 63 g), accumulating better statistics. Approximately 10 % of the trials gave positive result, i.e., a clear transient reduction in the weight of the proof mass. This apparently random behavior signals that some of the conditions which are necessary to trigger the effect are not well under control yet. In particular, we found that the duration of the superconducting transition is crucial: if the transition is too quick or too slow with respect to certain criteria, no effect is observed. The duration of the transition, in turn, depends strongly on the thermal conditions of the disk, and the latter can be controlled only with limited accuracy.
Our improved setup did not comprise the AC generator anymore. Thus error analysis is further simplified. One only needs to consider the parasitic effects of buoyancy and molecular diamagnetism. For both error sources, upper limits can be set according to the discussion by Podkletnov and these limits are much smaller (by a factor 20 at least) than the observed effect.
As mentioned above, the transient reduction in the weight of the proof mass was always coincident with the thermal transition of the YBCO disk from the superconducting to the non-superconducting state. This was checked as follows.
Figure 1. (http://www.gravity.org/dew.htm)
Fig. 1 - Scheme of our [magnet+LEVHEX] setup.
Figure 2. (http://www.gravity.org/bil.htm)
Fig. 2 - Detection system for the demonstration experiment of transient shielding effect at the superconducting transition.