Well, I've been working on writing my undergraduate thesis so that I can graduate. The topic of my research is "Asteroid Interdiction." In other words, I studied how to prevent an asteroid (or other large projectile object) from hitting the earth. Specifically, I studied the energy coupling between the high-energy neutron or photon source device (aka a nuclear bomb) and the target NEO (asteroid).
One of the bug-bears of this project is using the vacuum surrounding the target (for once the assumption that everything is in a relative vacuum is a good one). In the first simulations (in which we had to model how much of the energy from the bomb was actually deposited in the asteroid), the vacuum require material (albeit, a particle per square meter), or else the energy from the device would be assumed lost. In the later simulation (in which we looked at shocks, temperatures, ablation, and most importantly the deflection velocity of the asteroid), the vacuum caused another problem. The equations of state and failure models that we needed to use were causing the asteroid to "want" to fly apart even if there wasn't a bomb present (we're only trying to ablate a thin layer from one side of the asteroid). This is because of the pressure difference between the object (which was apparently compressed slightly) and the vacuum (which had an effective pressure of zero). This second problem probably took about a week to fix during the summer and might be something that I ought to include a mention of in my thesis (which will be a pain because of the nature of theses).
In conclusion, vacuums suck.