launchdrag.frink

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/** This program calculates the total energy expended by a rocket fighting
    atmospheric drag. */

use StandardAtmosphere.frink

getDensity[altitude] :=
{
   [temp, pressure] = StandardAtmosphere.getTemperatureAndPressure[altitude]
   return StandardAtmosphere.getDensity[altitude, temp, pressure]
}

getDensityVelocitySquaredProduct[altitude, velocity] :=
{
   getDensity[altitude] * velocity^2
}


altitude =  0 ft
v =  0 mph

mass = 13500 kg        // Full mass of X-15B, empty is 4500 kg
Frocket =  262.5/1 kN  // Thrust of X-15B

target = 350 km
Cd = 0.10
A = 33 ft^2

timestep = .01 s

t = 0 s
Esum = 0 J
while (altitude < target)
{
   density = getDensity[altitude]
   Fdrag = 1/2 density v^2 A Cd

   weight = G earthmass mass / (altitude + earthradius)^2   // Correct weight for decreasing gravity
   Fup = Frocket - Fdrag - weight

   a = Fup/mass                                             // Actual upward acceleration

   vnew = v + a timestep
   vave = (v + vnew) / 2                  // Average velocity during timestep

   stepdist = vave * timestep             // Distance traveled in timestep
   Esum = Esum + Fdrag * stepdist         // Energy lost due to drag

   println[format[t,"s",2] + "\t" + format[altitude,"km", 3] + "\t" + formatSig[v, "mach", 3] + "\t" + formatSig[a,"gee",3] + "\t" + formatSig[Fdrag, "lbf", 6] + "\t" + formatEng[Esum, "J", 5]]
   
   v = vnew
   altitude = altitude + stepdist

   t = t + timestep
}


Download or view launchdrag.frink in plain text format

This is a program written in the programming language Frink.
For more information, view the Frink Documentation or see More Sample Frink Programs.

Alan Eliasen was born 20217 days, 23 hours, 43 minutes ago.