The article is pretty vague about how this is actually done. Basically, a rocket motor burn is done when the craft is at the high point of its (very elliptical) orbit, pushing against the direction of travel to slow the orbital speed, and that makes the lowest point of the next half-orbit low enough to get into the atmosphere and experience atmospheric drag. But, not so low that there is enough drag to cause the craft to slow down enough to come out of orbit. Just enough to lower the high point of the next half-orbit. If they want the next high point to be even lower, they can let the craft do another full orbit, getting atmospheric drag at its next low point so that the following high point is even lower. However if the craft is intended to stay in orbit, it will need to do a stabilizing burn at one of those high points, making it go faster so it raises the next low point out of the atmosphere and stops the slowing down process. Otherwise, the high points of the orbit keep decreasing, so the speed at the low points keeps decreasing, until the craft finally gets enough atmospheric drag during one of its low point passages that it can no longer orbit and completely reenters the atmosphere. So, the maneuver cab be used either to get into a stable lower orbit with less rocket fuel required, or even get to reentry with much less rocket fuel required. Reply