That is a great question! I am part of a design team at Tufts University and we are looking into the problem of small balloon stabilization in light/moderate wind. (Specifically for the mini-balloon-kit) Currently we just finished the design scoping phase of our process and have started prototyping potential solutions. A design we are really interested in is shown below:
The pictures show a very rough prototype that does not include any mylar balloons or tethers. Nevertheless, the design is called the Magnus Effect Balloon (MEB); it will utilize the upward lift of both helium balloons and the magnus effect. The magnus effect is described by the following physics outlined below:
Currently we are trying to figure out the exact design parameters (materials, # of balloons, max lift, target wind speed, max wind speed, tethering system) that will go into the a next prototype that will be a lot closer to the final design. We have CAD models of the design and are quickly iterating in virtual space and with scale models to find an optimized design.
The design developed out of a literature review on vertical wind turbines. It was believed that due to the dynamics of a vertical wind turbine the linear momentum of the wind could effectively be transferred into angular momentum of the system. Applying this concept to a balloon mapping kit, the balloons would acquire angular momentum that would in turn stabilize the system by resisting changes to the angular momentum vector. Similarly vertical wind turbines have high lift to drag ratios, which would maximize the flying angle of the balloons. It was found however, that a vertical wind turbine would not be sufficient alone. Physically the system would still be unstable to procession due to the unavoidable torque applied by the string, required a lot of materials, and would be difficult to transport. The final design of the MEB is clearly better because it does not suffer from any of the problems suffered by the vertical turbine and produces upward lift! Furthermore, some of the same concepts used for vertical wind turbine can be used to design fins for the MEB.
At the same time we are also pursuing a much simpler design that can be produced quickly and has been done before in the past.
The design shown above combines a balloon with a small kite that can self-oriented itself into the wind. The best materials to be used for the kite are currently under-investigation. One balloon would be ideal for this design but it might not provide enough lift on a windless day. Therefore there might be a minimum wind speed requirement or two balloons will be used.