Project Mohole Drilling Platform 



M^ = yaw moment, positive when producing yaw to port 



P = 0.00238 slugs/cu ft 



u = forward velocity of vessel relative to air 



V = lateral velocity of vessel relative to air, positive to port 



v^ = total velocity of vessel relative to air 



a = arctan VAJ 



CpS = drag coefficient times reference area in square feet 



C^S = cross-force coefficient times reference area 



C^jS = moment coefficient times reference area. 



Values of c^s and Cj^s are tabulated in the program as a function of a. The 

 tabulated values were based on a DTMB Wind Tunnel Report.* The formula for 

 Cj^S was also derived from the DTMB data for this item. 



PROPULSIVE FORCES 



The propulsive forces produced by the main propellers and positioning units 

 under the control of the positioning system computer are determined as de- 

 scribed in the steps which follow. Where numerical values are given, these are 

 the values typically used; they may be varied as desired from problem to prob- 

 lem. 



Apparent Vessel Position 



The apparent position of the vessel with respect to the hole is determined 

 as follows: 



If the integrator is on, AX and ay are incremented by a specified fraction 

 of X and Y , respectively, at each sampling interval. If the integrator is off, 



AX = AY = 0. 



Xg = X + AX 

 Y„ = Y + AY 



*J. T. Matthews, "Low Speed Wind Tunnel Tests of a 1:60-Scale Mohole Drilling 

 Platform Model," David Taylor Model Basin Report, Aero Tests A551, June 

 1964. 



439 



