Skip to main content

NASA and Nash Equilibriums

Since the final Space Shuttle mission, which launched on July 8, 2011, Americans have been yearning to see their country regain the capability of domestically launching astronauts into space.  With the landing of the NASA Curiosity rover on August 6, 2012, the United States’ appetite for a “Made in America” presence in space was whetted.  Nevertheless, nothing can compare to watching U.S. astronauts soaring to “the final frontier” aboard a home-grown rocket.  Thankfully, NASA is not dead.  In fact, the development of the NASA Space Launch System (SLS) is currently underway, with a goal of giving back America’s capability of launching humans into space – to the Moon, to asteroids, or even to Mars in the near future.

The road to developing this new human Space Launch System has been a rough and rugged one, with many twists and turns along the way.  In his 2009 paper, “NASA Equilibrium: Game Theory and National Policy,” Edgar Zapata, an Operations Analyst for NASA, employs simple game theory ideas (just like those covered in Networks class lectures) to discuss possible reasons why NASA has made the decisions it has in developing this new system and to argue that these decisions may not actually be the best choices in the long run for America’s space exploration endeavors.

Zapata’s paper discusses the outcomes of the NASA Exploration System Architecture Study (ESAS), which was tasked with determining several important aspects of what would define the “next generation” of manned space launch vehicles.  One of the most important decisions NASA had to make in the ESAS study was whether the new manned rocket should be “reusable” (the same rocket hardware can be launched several times, like Shuttle) or “expendable” (the rocket can be launched only once).  Ultimately, NASA chose to go with the expendable SLS, which bears a striking resemblance to the Apollo-era Saturn V rocket design.  Zapata argues that NASA may have chosen this expendable Space Launch System in an effort to avoid repeating the tragic Columbia and Challenger Shuttle disasters.

The main purpose of Zapata’s paper, however, is to explore whether making the SLS expendable was really the best possible choice for NASA, especially in the now very competitive space technology industry.  Due to recent, large budget cuts for NASA and increased government encouragement of commercial development, private industry has become an equally large player as NASA in the space exploration industry, if not larger.  To investigate this idea, Zapata sets up a game theory model, in which the two key players are, not surprisingly, NASA and commercial industry.  Each player in the game can choose between two strategies: to make their rockets reusable or expendable.  Zapata argues that “the first airplanes or cars, technological devices of some complexity for the time, may rightly be called ‘fractionally’ expendable, given lack of robustness, or expensive, regular ‘re-build’ needs. Yet it was only as true reusability was achieved that these industries took on the growth characteristics and benefits that would dwarf all previous notions of doing well in the industry.”  Thus, reusability should have a much higher payoff for any type of transportation technology in the long run.  To reflect that notion, Zapata eventually creates the (admittedly exaggerated) payoff matrix below.  Clearly, there are two Nash equilibriums, one where both players choose the “Reusable” strategy, and one where they both choose the “Expendable” strategy.  The fact that these equilibriums occur where NASA and Industry both choose the same design strategy presumably reflects the reality that both NASA and Industry benefit when they can work together and utilize common core technologies and infrastructure.


                                   Reusable    Expendable

NASA        Reusable          10,10          1,2

                Expendable        2,1            2,2

Zapata’s paper was written in 2009 and the space launch industry has changed considerably since then.  However, his model is definitely still valid for use in analyzing the current state of affairs.  At present, industry has chosen the expendable launch vehicle strategy.  The largest space launch vehicle provider to the U.S. Government is United Launch Alliance (ULA), which launches the EELV (Evolved Expendable Launch Vehicle) Atlas and Delta rockets, which have been around in some form since the 1950’s and 1960’s.  Alternatively, ULA’s largest soon-to-be competitor, SpaceX, is perfecting the new Falcon 9 rocket, which is currently expendable, but should soon be reusable.  In fact, it appears that much of the newest space technologies are starting to tend toward reusability.

Throughout the life of the Shuttle program, the state of the game was such that NASA had chosen the “Reusable” strategy, while Industry had persisted on with the “Expendable” strategy. Given the Shuttle program’s high costs and relatively short lifespan, as compared to expendable rockets, it is clear why this state was unstable and why the payoff was lower for NASA (the payoff for NASA in this state is 1, and the payoff for Industry in this state is 2).  The game currently appears to be in the Nash equilibrium state where both players have chosen the “Expendable” strategy, given NASA’s expendable SLS development and ULA’s jam-packed manifest for future EELV rocket launches.  However, with new industry leaning toward reusable designs, the game may soon again be temporarily in an unstable state, in which NASA chooses the “Expendable” strategy and Industry tends toward a “Reusable” strategy.  Although this state has a higher payoff for NASA, perhaps in the form of a reinvigorated American spirit, with decreasing government funding for NASA, it follows that this unstable state cannot and will not endure for long.  (By definition, the game cannot remain in an unstable state for long.)  So will America’s next generation of space launch vehicles ever finally reach the high-payoff and “socially optimal” equilibrium point where both players have chosen the “Reusable” strategy that maximizes both their payoffs?  John Nash’s 1994 Nobel Prize winning research and the principles taught in Networks class all say this will happen.  And if rockets follow suit with planes and cars, this universal reusability could mean amazing things for the future of manned space exploration and space travel.

Edgar Zapata’s paper, along with some background information, is available here:



Leave a Reply

Blogging Calendar

September 2012
« Aug   Oct »