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 19985 days, 2 hours, 29 minutes ago.