NDSolve Singularity

*To*: mathgroup at smc.vnet.net*Subject*: [mg85504] NDSolve Singularity*From*: Tara.Ann.Lorenz at gmail.com*Date*: Wed, 13 Feb 2008 04:08:04 -0500 (EST)

Hello, The following input for NDSolve is giving me a "singularity" error (see error message below). As a result, my system of equations is being solved until the singularity at t=0.179 and not until t=30 as desired. Any suggestions on how to avoid this issue? Thank you! va = 4.71*y[t] - 246; q = 6; kl = 5; kt = 40; b = 760; mrco2 = 250; caco2 = 48 + 6*(paco2 - 40)/7; paco2 = (b - 47)*r[t]; fico2 = 0.07; grodinstime0to30 = NDSolve[{r'[ t] == (1/ kl)*((fico2*va + 8.63*q*(y[t] - caco2)/(b - 47) - r[t]*va)), y'[t] == (mrco2 + 10*q*(caco2 - y[t]))/(10*kt), r[0] == 0.058, y[0] == 0.533}, {r, y}, {t, 0, 30}] ERROR MESSAGE: NDSolve::ndsz: At t == 0.17926445744166167`, step size is effectively zero; singularity or stiff system suspected. >>