Copyright (c) 1996 by Christopher M. Dicely Cruising Performance for Vehicles: Most vehicles don't go flat out most of the time. First, its very fuel wasting, second, its dangerous, and third (for civilian ground vehicles especially) its often illegal. So how do vehicles perform under these conditions? Well, finding out is simple... Cruising Power Requirement Once you've figured out the basic performance stats of the vehicle, decide on a "cruising speed" (you can easily calculate stats for a variety of different cruising speeds if thats what you want). To figure out the (motive) power or thrust requirement for this cruising speed, just reverse the appropriate top speed equation using the cruising speed as the top speed. F=speed factor used originally to calculate top speed, M=vehicle loaded mass (tons)] P = (S x S x M) / (F x F) Notes: If a vehicle has Fair streamling and a cruising speed above 50mph, use the higher of 50mph or (S/1.05) instead of S in the above equation. If a vehicle has Good or better streamlining and a cruising speed above 50mph, use the higher of 50mph or (S/1.1) in the above equation. If using thrust systems from ground propulsion, 4lbs of thrust is equivalent to 1kW of motive power. Water Vehicles: [T=cruising (aquatic) thrust, D=hydrodynamic drag, S=cruising speed] T = (S x S x S) x D / 216 Notes: if using a track, wheel, or leg drivetrain to provide aquatic thrust, 1kW of motive power is equivalent to 2lb of thrust. If a flexibody drivetrain, 1kW of motive power is equivalent to 5lb of thrust. Air Vehicles: [T=motive thrust, D=aerodynamic drag, S=cruising speed] T = (S x S) x D / 7500 ------------ Once this power/thrust level is determined, all other performance stats, as well as fuel consumption, can be recalculated using this power or thrust level. Note: Jet engine fuel consumption is already designed to represent cruising, if using these rules all Jet fuel consumptions should be tripled when figuring "full power" performance. Note that reduced thrust levels will reduce the amount of electrical power available from jet engine systems, and may require installation of additional power systems to make up for the shortfall. Remember: Thrust needed for *lift* remains the same for vehicles using thrusting systems for aerostatic lift. Helicopters: Helicopters don't calculate cruising stats, as their attainable speed and lift are linked -- they can, however, calculated performance at lower power levels noting reduced available lift.