As the cone fills up the airship drops ballast till its "mooring mast" is half submerged. The principle of the drag rope comes into play--if the airship starts to rise it finds itself lifting an increasingly heavier load, counteracting the rising tendency. If it starts to settle down toward the water, the load is correspondingly lessened and the ship grows lighter. The result is that the airship is held highly stable, even in a rough sea. The surface ship then sends a small boat alongside and dispatches the relief crew members or supplies, them up and down the ladder, or uses a winch, the platform atop the anchor serving as the operating base. This system also permits the moving of a sick passenger ashore, or the rescue of a man overboard.
When the airship is ready to leave its anchorage, the cone is tipped by a line attached to the bottom, spilling the water, and hauled aboard. The servicing ship need carry no special equipment. The weight of cone and ladder is negligible.
By being able to pick up ballast and borrow fuel from a passing ship, (neither airship nor surface ship need slow down for the fuel exchange if going in the same direction) the airship greatly increases its radius of operations.
The advantage of being able to change crews at sea may not be quite as clear. This, however, grows out of the fact that today's non-rigid airship has greater endurance than the crew which flies it. An anti-submarine, anti-mine patrol calls for constant alertness. Reduction of vibration and noise, the use of closed cars instead of open cockpits has lessened fatigue, enabling men to remain on duty over longer periods than before. But obviously there are limits.
The Navy is conservative in estimating how long its new "K" ships may stay out without refueling. Weather and the nature of the mission will have some bearing on that, but if we assume a cruise of 48, 60 or even 72 hours which might be done under favorable conditions and idling the motors, we still cannot expect a crew of men to remain vigilant and alert for that length of time.
Extra men for relief watches can be carried only at the expense of the fuel load. However, if a fresh crew could be sent aboard every 12 hours from a nearby surface ship, along with fuel, ballast and supplies, the blimps might operate for extended periods.