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ACHAB: Analysis Code for High Altitude Balloons Chapter 3
3.2 – ACHAB: Analysis Code for High-Altitude Balloons
The development of this model is essentially based on many results given in Ref. 9,
Ref. 16, Ref. 17, Ref. 18, Ref. 20, Ref. 22, Ref. 26. We will start describing the
dynamical model then the general geometric properties of the balloon and finally the
thermal model.
3.2.1 – Dynamical Model
3.2.1.1 – Forces
In order to write the 3D differential equations that describe the balloon dynamics, it
is necessary to identify the forces that act on the system. A rigorous analysis of all
the forces to which a balloon system is subjected during inflation, launch, and flight
is beyond the scope and needs of this model; however, those of greatest importance
for the description of the balloon motion are considered to be 9,16,17,20 :
• net buoyancy
• weight
• aerodynamic drag
Drag
GI
M gross
V ˆ
g
Figure 3.2 – Forces acting on the balloon.
Figure 3.2 shows the forces acting on the balloon. The velocity vector is not oriented
vertically because the model is 3-dimensional and takes into account wind
disturbances.
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