by Phil Rowe
Just because you've got a team loaded with PhD's and world class scientists, doesn't mean you've got, even collectively, a whole lot of sense. That's the view held by some test pilots at Edwards AFB, California a while back. I guess an explanation is in order.
During the days when the Air Force encouraged development and testing of equipment to catch intelligence gathering satellites falling from orbit, parachutes were a high interest item.
Parachutes gently lowered satellite payload capsules to earth for retrieval by aircraft. Specially equipped JC-130 Hercules transports actually caught the descending payloads in mid-air. A system of grappling hooks dragged below and aft of the plane snagged the parachute canopy. Then a motorized winch would reel the catch in like a fish.
Parachutes perform some pretty wild dances during descent. Some twist and turn. Others skitter left and right, not at all falling in a straight line. Some turn and wander at the same time. And to make it even more challenging for aerial recovery crews, quite often no two parachutes of the same design, from the same manufacturer, behave the same way during descent.
One of the many technical problems to overcome, in bringing such a system to operational readiness, was the design of sturdy parachutes. Catching a vertically descending parachute, with an airplane traveling 160 knots horizontally, presented tough requirements on the chute's canopy and the shroud lines. Dragging hooks into the parachute without tearing through the fabric posed design challenges.
Engineers and scientists in Los Angeles pondered this problem. Some of the experts were German expatriate brought to this country after WWII. They were among the world's leading authorities on this subject. One, or more, of these outstanding paradynamicists decided that a special test parachute was needed. They wanted to instrument the fabric of a parachute canopy to determine the loads and stresses applied when retrieval hooks snagged the fabric. That would enable them to design parachutes strong enough to withstand the applied loads.
What could be more logical?
All their creative energies were brought to bear on the design of special parachute materials. They soon came up with a fabric which incorporated unique wires woven into the cloth. When stretched, as happens with hooks pulling through the material, the electrical resistance of the embedded wires changes. Now they had a means of correlating applied loads to electrical signals. Eureka! Instrumented fabric to measure the stresses and strains of retrieval.
Just one problem. The cost of making enough wire instrumented fabric for even one parachute was prohibitive. The Air Force could not afford such an expense. What to do?
Undaunted, the experts came up with a way to use less of the expensive fabric and still gather the essential data. Who says scientists aren't creative?
Their solution required that only one gore of the test parachute include the wire-instrumented fabric. Gores in a parachute canopy are like orange peel sections, all sewn together to form the hemispheric canopy. Shroud lines and riser cords carried the payload weight to the canopy above. Such a clever solution.
The test pilots, supposed to catch the experimental parachute, worried. Just how were they to know which gore had the special wire materials, and how could they spot it in flight?
No problem, the erstwhile scientists responded. We will simply paint that particular gore black. Since all the others are alternately white or orange, the black gore will stand out like a sore thumb. All you pilots have to do is put the hooks into that black gore. It's easy.
The pilots shook their heads. Obviously, those learned experts had never watched a descending parachute, much less tried to catch one.
How did those scientists expect the pilots to maneuver their plane for the catch, and assure the hooks were placed precisely into the black gore? Fat chance!
The day of the test came, hot and clear in the southern California sun. Two JC-130's participated. The first was the drop ship, climbing ahead and high above the retrieval aircraft. At 25,000 feet the first would toss out the practice payload and its special parachute.
At 18,000 feet the recovery airplane was supposed to start making passes over and by the descending parachute. After a few fly-bys, to gauge the behavior of the quarry and determine the best heading to fly to meet the single black gore, the pilots headed in for the catch.
Unfortunately, the parachute would not cooperate. It turned and oscillated in a random manner, making placement of the hooks into that special gore impossible. Only pure chance gave the pilots any hope of success.
Oh, they caught the parachute all right, and winched the payload into the aft cargo door normally. But the special gore was untouched. No data was collected, save the obvious. Expecting pilots to do what the scientists wanted was wholly unrealistic.
The "I told you so's" had their day, for the tests were not resumed and the whole idea of putting hooks into one part of a twisting, turning parachute was abandoned.
Some sensible and unsung hero simply decided to strengthen the risers and shroud lines, giving the parachutes the needed reinforcement at a very minor cost.
So, if you thought that parachutes were simple creations, beyond further tinkering, then you underestimated what government and contractor scientists and engineers could produce. Dozens of unique designs for recovery parachutes, and equipment to catch them in mid-flight, were developed over the span of 25 years. Those were the years when keeping the technological edge was deemed crucial to national security.