 Testing was performed using a low-thrust torsion pendulum able to detect force at the micronewton level within a sealed but unevacuated vacuum chamber (the RF power amplifier used an electrolytic capacitor unable to operate in a hard vacuum).The experimenters recorded directional thrust immediately upon application of power.Their first tests of this tapered cavity were conducted at very low power (2% of Shawyer's 2002 experiment).