# Development and Sea Trials of a Shuttle Type AUV "ALBAC"

## Estimation of Gliding Performance

*****FIG. 3 AUV in Gliding ******

The gliding performance of the ALBAC was estimated and evaluated in the first design stage, because it completely depends on the shape of hull. Suppose that the center of gravity of the vehicle O is gliding at speed V. Configuration of the vehicle is illustrated in Fig. 3 where the gliding angle and the angle of attack are denoted by ge and a, respectively. The proportional gliding angle ge and static stability of the system are given by

(1)

(2)

Here,

- CL : lift coefficient,
- CD : drag coefficient,
- Cm : moment coefficient,
- a : angle of attack. These Coefficients are functions of the shape and the angle of attack, and can be calculated on the basis of USAF DATCOM[3] compiled for estimation of the stability and for improvement of aircraft[4].

Equilibrium equations of forces and moment which determine a, ge and V are given by

(3)

(4)

(5)

Here,

- B: buoyancy,
- G : dry weight,
- LW : wing lift,
- DW : wing drag,
- LT : tail lift,
- DT : tail drag,
- LB : body lift,
- DB : body drag,
- lG : location of center of gravity from body apex,
- lbuoy : location of center of buoyancy from body apex,
- lW : aerodynamic center location of wing from body apex,
- lT : aerodynamic center location of tail from body apex,
- lbody : aerodynamic center location of body from body apex.

At the first stage of development, a 30 cm length model was made and tested to evaluate gliding performance. Results of the test show good agreement with the estimated values as in Fig. 4.

****FIG. 4 Results of Gliding Experiment with a Small Model***

Last modified: Tue June 6 1995