The Gas Column to Proxima Centauri and the Drag Energy It Removes from a Fast Probe

This paper addresses a single quantitative question about interstellar objects and interstellar traversal: How much interstellar gas does a probe actually sweep up on the way to the nearest star, and what energy does that column carry away? Working from published survey values for the known interstellar objects and for the local interstellar medium, the paper computes swept-up column density, areal mass and drag energy per unit area at three speeds. The headline values obtained are col = 8.03e+17; sigma = 1.34e-05; drag01 = 1.21e+10. Each number is produced by the deposited computation script from inputs that are stated in full, so the result can be reproduced, checked and updated as survey measurements improve. The study is a computation from stated assumptions and published data; it presents no new observations. Its contribution is a transparent budget: a set of numbers, the relations that produce them, and an explicit account of how sensitively each number depends on the assumptions behind it.