Can outgassing produce a significant thrust on a space ship? There are a variety of materials that outgas in the atmosphere, and I imagine they would do so even more in the vacuum of space.
I imagine an object in space would experience a small force as outgassing of its vacuum-exposed surfaces occurs, especially if one side of the object is made of a material that outgasses significantly more than the materials on the other side.
Is the force exerted by outgassing significant enough that it must be taken into account in orbital mechanics? If so, is there a case where this has actually caused a problem, or could have caused a problem if it hadn't been taken into account?
 A: Back of the envelope: mean thermal velocity of the molecules or atoms times mass loss rate. At room temperature that may be something on the order of 1000m/s*1e-9kg/s =1e-6N. For a 1000kg spacecraft this amounts to 1e-9m/s^2 acceleration and a position error after a year of about 500km. OK, if you want to land on Mars, maybe you want to correct for that, after all. :-) In practice we measure the position to a higher accuracy and don't worry where it came from, unless the mass loss is much larger (my example is probably already at the upper tolerable end of it with about 30g/year), indicating a faulty propellant valve. 
A: Depending on your exact definition, I've seen it. 
An exoatmospheric experiment got messed up when the expended solid fuel engine on the booster continued to expel hot gas and small chunks of motor housing out the back. The added delta-v was more than 1 m/sec, and caused unplanned movement of the booster, which messed up the experiment.
It turns out the phenomenon is known in the rocket community, and is called "chuffing". 
Oh well, live and learn.
