NASA rocket engine runs 5+ years

[muriel_volestrangler]

12. 30 million newton seconds over 5 years is a thrust of about 0.19 N

5 * 365.25 * 24 * 3600 = 1.58*10^8 seconds
30 *10^6 / 1.58*10^8 = 0.19 N

It used 770 kg of propellant; if the empty mass of the rocket is 100 kg, then you should be able to use the formula here: http://www.physicsforums.com/showthread.php?t=476154
D = (Ve / mdot) * (M0 - M * (log(M0 / M) + 1))
where Ve = exhaust velocity (90,000mph, which is 39,000 m/s); mdot = rate of change of mass = 770kg/1.58*10^8s; M0=initial mass with propellant = 870kg; M= final mass=100kg
which, if I've plugged it all in correctly, gives 4.4*10^12 metres. The distance from the Sun to Neptune is about 4.5*10^12 metres, so we'll say "it could have gone from here to Neptune - ignoring gravity".