Since the Scouts and the Pioneers had begun adding more bits onto Izzy, its ballistic coefficient had been dropping again, and boost burns had come more frequently. And it was always the case that thrusters had to be fired every now and again to correct the station’s altitude. All of it grew more problematic as more was added onto the basic structure. Izzy had been an ungainly construct even before all the new pieces had been added onto it. Thrust applied to one part of it would ramify through the other modules as various parts of the truss and other structural members took up the strain and passed it on down the line. To put it in the simplest possible terms, Izzy had gotten all floppy as more stuff was attached to it, and its floppiness made it difficult to reboost the orbit or even to tweak the angle at which it "flew" through space. They had allowed the orbit to decay by a serious amount, over sixteen kilometers, during the busiest part of the Pioneers’ efforts, but now reboosting had to become a routine operation. And every firing of the engine on the bottom of H2 revealed structural weaknesses that had to be jury-rigged, sometimes literally with zip ties and duct tape, before it could proceed.