guy6, Let me see if I can clarify this. My understanding is that it is a reference to the Stratellite. The ability to move gas from one gas cell to another would allow the nose to dip or raise as need to achieve the porpoising effect until an acceptable trim can be achieved to restore level flight. The shifting of gas amongst gas cells, in conjunction with the motors should achieve the desired results. Below is an explanation and visual reference to porpoising in action. Hope this helps.
Porpoising is a common name for a condition when an aircraft cannot maintain a steady or level flight path. This behavior is also related to lift and its dependence on speed as well as angle of attack. Lift tends to increase with angle of attack until a point called the stall angle is reached. At this angle, the airflow separates from the surface of the wing and the lift rapidly decreases. As the speed of the glider relative to the air decreases in a tailwind, the glider will try to increase its angle of attack to compensate for the loss in lift. This increasing angle of attack increases the lift coefficient (CL) that in turn increases lift as described by the equation introduced earlier. In other words, as velocity goes down, angle of attack needs to go up to keep the lift the same.
However, the angle of attack eventually reaches the stall angle where lift no longer increases but starts to drop off. When this occurs, the glider nose dives because it no longer has enough lift to remain level. However, a dive increases the glider's speed, so lift again increases and the glider can start to climb. This tradeoff between speed and altitude is a classic aerodynamic phenomenon that has a special name called a phugoid.
Your Question: could this be a reference to the Sky Worm/Sky Dragon concept?
No, i believe the paper was refering to a very different scheme in airship design (AHAB). Cell segmentation internally not externally is used to develop the porpoising action.
Could the Airworm operate in a similar manner? Because the Airworm lacks a Aerobody (like Stratellite or AHAB [mentioned below] or lifting body shape, it would be expending more electrical energy in the pursuit of such a manuever.
The porpoising motion is being attributed to the third pictured airship, just below the quote you've used. Third craft (first GTE, second a Telesphere balloon) is New Mexico State Universities approach to nearspace airship. It goes by the handle AHAB. Using it's aerobody in combination with unique internal gas management system as previously posted, the airship hopes to use stalling as a technique to operate in high winds; converting the forces experienced into a series of elevation gains and loses while at the same time maintaining it's relative position. From my past readings, believe it to be a CIA funded endeavor. Did you see the movie Syriana? CIA loves this UAV stuff!!
"In addition, the Physical Science Lab at New Mexico State University is designing the Advanced High-Altitude Aerobody (AHAB). This superpressure balloon incorporates wing-like devices to give it a sleek aerodynamic shape. AHAB is designed to offset the effects of light winds by using a porpoising technique as necessary, trading altitude for horizontal motion. The craft is made up of a series of individual cells, and helium is pumped between cells to effect movement."
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