1.5e7 m/s is 5% of speed of light
v = at so t = v/a
t = (1.5e7 m/s) / (10 m/s^2) = 1.5e6 sec
(1.5e6 sec) / (3600 sec/hour) ~ 417 hours ~ 17 days
Your error is that 1 g is not 1 m/s^2 but rather 10 m/s^2.
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