square wave list making

import math

def kecur(rad):
    return 1.50335 * (10 ** - 10) * (- 1 + math.sqrt(1 + 0.146603 * rad ** 2))


def timearound(rad):
    return 2.73682 * (10 ** - 8) * math.sqrt(1 + 0.146603 * rad ** 2)


def radfromke(ke):
    return 427.933  * math.sqrt(ke) * math.sqrt(495534. + 1.6481 * (10 ** 15) * ke)


q =  1.60 * (10 ** -19)
vol = 5000
kdiff = q * vol
rad = .15
r = radfromke(kdiff)
t = 0
print(t)
f = open("swaptimes.txt","w")
while (r < rad):
    t = t + (timearound(r) / 2)
    r = radfromke(kecur(r) + kdiff)
    t = t + (timearound(t) / 2)
    print(t)
    f.write(str(t)+"\n")