America at 500: Where will we be in space in 2276?

The United States has taken some significant steps into the final frontier during its first 250 years.The nation has put people on the moon, helped build and operate a long-running space station in low Earth orbit (LEO) and sent fleets of robotic explorers to many corners of the solar system — and even beyond it, into interstellar space. All of this work has been done relatively recently, as the space age didn't dawn until 1957; when the U.S. was born on July 4, 1776, humanity was still se