What-Physics-Allows
A slide rule does not add; it multiplies, by sliding logarithms past each other. With the cursor fogged, Okonkwo could no longer read a quotient to three figures. He could read it to one, maybe two if he squinted and lied to himself. For the rocket equation, where the answer hid inside an exponential, one figure of error was the difference between braking and a crater.
He breathed. He thought about what physics actually allowed, as opposed to what the procedures preferred.
The procedures wanted him to carry fuel for the brake. But the *Cataract* had engines too, and a tether, and a crew who would much rather catch a tug than scrape one off their hull. He did not have to stop himself. He only had to arrive slowly enough that someone else could finish the stopping — and *slowly enough* was a number he could afford.
That bought back delta-v. Not enough.
The rest he stole from geometry. The window opened at a nominal point, but the equation didn't care about nominal; it cared about where the planets actually were. If he burned eleven minutes *early*, at a slightly worse angle, he wasted a little efficiency on the transfer but spent it from the fat part of the budget, and saved more than he wasted at the lean end. Worse heading, cheaper total. The universe granted no appeals, but it kept honest books, and sometimes the honest books had a back door.
He worked it twice, once with