CASPER, Wyo. — Dozens of people filled the newly minted viewing deck at Hell’s Half Acre on Friday, celebrating the site’s reopening and many improvements. Encompassing roughly 320 acres, Hell’s Half Acre is a geologic oddity composed of deep ravines, caves, rock formations and hard-packed eroded earth. The landform was famously used as the location for the fictional planet of Klendathu in the 1997 Paul Verhoeven–directed movie “Starship Trooper…