21st Century Space Grant Modernization Act of 2021 This bill revises provisions relating to the National Space Grant College and Fellowship Program. The National Aeronautics and Space Administration (NASA) shall carry out the program with the objective of providing hands-on research, training, and education programs with measurable outcomes in each state. NASA shall carry out the program through a space grant consortium in each state. The bill revises the purposes of the program to support space research programs that promote equally the state and regional STEM (science, technology, engineering, and mathematics) interests of each space grant consortium. NASA shall award grants to the lead institution of each state's space grant consortium to carry out at least three of six specified research, training, and education programs. The bill repeals certain provisions relating to the program, including provisions establishing the space grant review panel.