Mars, the red planet named for the god of war, a mysterious dust-ridden place, is most like Earth in its climate and seasons. Of all the possible destinations in space to travel, Mars is the most likely for humans to reach. According to esteemed scientist Louis Friedman, it may be the only destination outside the moon to ever see human footprints.

Far from diminishing our future in space, Human Spaceflight lays out a provocative future for human space travel. The noted aerospace engineer and scientist says that human space exploration will continue well into the future, but space...