A model of a Mercury-Atlas.
Of course, Grissom never rode atop an Atlas booster; the museum displays one
for completeness. The accompanying sign reads
Two types of rockets were used for Project Mercury. The first two manned
flights (Shepard, Grissom) used a Redstone
rocket. The next four flights used Atlas rockets (silver model) to
achieve orbit. Both rocket types were adapted from military missiles.