He is a Technical Lead & Research Specialist for Wyle Integrated Science & Engineering at NASA's Johnson Space Center (JSC) in Houston, Texas.

[2][3][4][5] After graduating, he used his newly gained expertise to help design and develop aircraft and missile simulations to assist pilots with real-time combat decision making, but still had a strong desire to be a part of human spaceflight.

[4][5] Chappell's intent upon returning to college was to become a medical doctor specializing in aerospace medicine and he began taking classes to make that possible, but being a climber led him to learn about Rocky Mountain Rescue Group based in Boulder, CO.

He became a member of the all-volunteer team, one of the busiest in the country, and quickly became active performing technical rock, snow, and ice rescue missions.

Over time, his involvement on the mountain rescue team fed his interest in helping people while doing something he loved and he changed his educational course to pursue bioastronautics-related graduate degrees, studying how humans perform in the harsh environment of space.

[4][5] Chappell earned masters and doctoral degrees from the University of Colorado at Boulder (M.S., Aerospace Engineering, 2003; PhD, 2006),[2][5] studying human performance in simulated Moon and Mars gravity.

[6] While he was performing his graduate research, he worked as one of the lead systems engineers developing and launching a satellite to study cloud formation in the upper atmosphere.