Discretionary Spending

Function 250 - General Science, Space, and Technology

Eliminate Human Space Exploration Programs

CBO periodically issues a compendium of policy options (called Options for Reducing the Deficit) covering a broad range of issues, as well as separate reports that include options for changing federal tax and spending policies in particular areas. This option appears in one of those publications. The options are derived from many sources and reflect a range of possibilities. For each option, CBO presents an estimate of its effects on the budget but makes no recommendations. Inclusion or exclusion of any particular option does not imply an endorsement or rejection by CBO.

Billions of Dollars 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2019-
Change in Spending  
  Budget authority 0 -9.4 -9.6 -9.9 -10.1 -10.3 -10.6 -10.8 -11.0 -11.3 -38.9 -92.9
  Outlays 0 -7.1 -9.0 -9.7 -10.0 -10.2 -10.5 -10.7 -11.0 -11.2 -35.7 -89.3

This option would take effect in October 2019.


The National Aeronautics and Space Administration's (NASA's) Human Exploration and Operations Mission Directorate oversees both the development of the systems and capabilities required to explore deep space and the agency's operations in low-Earth orbit. The directorate's human exploration programs fund the research and development of the next generation of systems for deep space exploration and provide technical and financial support to the commercial space industry. Complementing those efforts, the space operations programs carry out missions in low-Earth orbit, most notably using the International Space Station, and provide facilities and services to communicate with satellites in space. In 2017, the directorate's funding included all of the funding provided for deep space exploration, 85 percent of the funding for low-Earth orbit and spaceflight, and 20 percent of the funding for exploration research and technology.


This option would eliminate all funding for NASA's directorate for human exploration and operations in space starting in 2020. The agency's science and aeronautics programs and robotic space missions would continue unchanged.

Effects on the Budget

Provided that federal appropriations were reduced accordingly, eliminating human space programs would save $89 billion between 2020 and 2028, the Congressional Budget Office estimates. By eliminating NASA's Human Exploration and Operations Mission Directorate, this option would decrease appropriations in three areas that support human space exploration. The eliminated appropriations would not immediately decrease outlays by the same amount, however, because funds appropriated in one year are typically spent over four years. If funding was eliminated in 2020, CBO expects that 75 percent of the resulting savings would accrue in that same year, 18 percent in the next year, and the remainder over the following two years. If funding was decreased rather than eliminated, the savings would be proportional to the change in spending, in CBO's estimation. There is some uncertainty about the option's savings as a result of restructuring in NASA's budget accounts in recent years and the potential for actual appropriations to differ from CBO's baseline projections.

Other Effects

The main argument for this option is that increased capabilities in electronics and information technology have generally reduced the need for humans to fly space missions. The scientific instruments used to gather knowledge in space today rely much less (or not at all) on nearby humans to operate them. Also, to avoid putting humans in harm's way, NASA and other federal agencies have increasingly used robots to perform potentially dangerous missions. To explore and study Mars, for example, NASA uses robotic rovers and orbiters. The Curiosity rover launched in November 2011, landed on Mars more than eight months later, and has been exploring the planet and conducting scientific studies since then, following commands delivered remotely.

Eliminating humans from spaceflights would avoid risk to human life and would decrease the cost of space exploration by reducing the weight and complexity of the vehicles needed for the missions. (Unlike instruments, humans need water, air, food, space to move around in, and rest.) In addition, by replacing people with instruments, one-way missions would be possible, thus eliminating the cost and complexity of return and reentry into the Earth's atmosphere. Return trips would be necessary only when a particular mission required it, such as to collect samples for further analysis.

A major argument against this option is that eliminating human spaceflight from the orbits near Earth would end the technical progress necessary to prepare for human missions to Mars (though such missions are—at a minimum—decades away). Moreover, if robotic missions proved too limiting, then human space efforts might have to be restarted. Another argument against this option is that there might be some scientific advantage to having humans at the International Space Station to conduct experiments in microgravity that could not be carried out in other, less costly, ways. (However, the International Space Station is currently scheduled to be retired in 2024; its decommissioning was twice postponed, first from 2015 and then from 2020.)