316 P. Mandel 
Normal diving and ascending procedures will be able to be carried out as follows on 
the Aluminaut. Condition 2 (see Table 2 and Fig. 4) would obtain when the Aluminaut is 
alongside an auxiliary vessel preparing for a dive. All solid variable as well as fixed 
ballast is on board, but it may be considered that the iron shot and water ballast had been 
jettisoned on a previous dive. When the boat has been made ready for submergence in all 
other respects, iron shot would be added from the mother ship to produce condition 3. In 
this condition the water tanks are still empty so that the boat is still afloat with over a 
foot of freeboard to the deck. The final submergence of the boat is now under the complete 
control of the pilot and when he is ready, he can flood the ballast tank, bringing the boat to 
condition 4 with a negative buoyancy of about 500 pounds. In all probability, the pilot 
would choose at this point 'to speed his descent by propelling the boat to the desired depth 
of operation. It would take roughly 50 minutes to reach 15,000 feet with a 30-degree down 
angle utilizing full power on the main propeller (40 minutes with the vertical propeller work- 
ing also). Otherwise, it would take about 4-1/2 hours. 
With no further change in ballasting the boat would be at neutral equilibrium at 15,000 
feet since due to compressibility effects (which will be discussed subsequently) the initial 
500 pounds of negative buoyancy would disappear at that depth. This corresponds to 
condition 5. 
Ascent can be achieved by any of the ballast arrangements shown in Table 2 and 
Fig. 4. The fastest panic condition ascent, which involves jettisoning the solid lead 
ballast and iron shot at 15,000-foot depth and the ballast water at 4,800 feet, utilizing full 
power on both the horizontal and vertical propellers, and a 30-degree up angle would take 
22 minutes from 15,000 feet with no leakage. With no power available (and no leakage) 
the panic ascent would consume about 44 minutes. Consideration was given earlier in the 
design to provision of an overboard discharge pump capable of handling a very modest 
amount of leakage at 15,000 feet. It was concluded that the weight saved by not installing 
the pump was greater than the weight of water which the pump could eject during an ascent. 
MOTION CHARACTERISTICS DURING VERTICAL ASCENT—PRELIMINARY 
CONSIDERATIONS 
Piccard reported in Ref. 3 that on several occasions the bathyscaphes experienced 
rather violent oscillations while rising freely under the influence of positive buoyancy. 
Since it was known that the Aluminaut would possess substantially less metacentric sta- 
bility than the Trieste, which would tend to permit larger oscillations, it was decided to 
study this problem thoroughly during the feasibility and design study of the Aluminaut. 
Bodies which are streamlined in planes through their longitudinal axis of symmetry, 
are usually very blunt in planes normal to their axis of symmetry. It is well known that 
such blunt bodies will shed Karman vortices. For cylindrical bodies moving normal to their 
axis, which corresponds fairly closely to the case of submarines rising vertically, it can be 
shown that the dependence of the period of the vortex shedding upon the various charac- 
teristics of the flow is expressed by a single curve of the Strouhal number D/T,V against 
the Reynolds number VD/v, where T, is the period of the vortex shedding (period of excita- 
tion), D is the diameter of the cylinder, V is the velocity, and v is the kinematic viscosity 
of the fluid. This curve was obtained experimentally in Ref. 4 for Reynolds numbers up to 
about 10° and plotted in such forms in Ref. 5 that extrapolation to slightly higher Reynolds 
was not too difficult. It is shown in Fig. 5 for Reynolds numbers up to about 4 x 10®. 
Also shown in Fig. 5 is cylinder-drag data as a function of Reynolds number taken from 
