The Space AdvocateAug 12, 2021

The Space Advocate Newsletter, August 2021

From the Chief Advocate

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Is nuclear propulsion the answer for sending humans to Mars, or just a costly diversion?

The answer depends on your point of view.

Fission nuclear power (powered by uranium, not the stately Plutonium-238 used by spacecraft since the 1960s) can enable powerful and efficient engines. These can reduce travel times and allow access to more orbital trajectories, providing value for a wide range of missions: scientific, human exploration, and national security.

The problem is these engines don't yet exist. Deciding on what type of nuclear propulsion to make, and to what specifications, all depends on the point of view of what you're trying to do. Science missions favor nuclear electric propulsion. The U.S. Space Force is interested in nuclear thermal. Human missions to Mars could use either, but require orders-of-magnitude more power and reliability.

A recent report by the U.S. National Academies evaluated nuclear propulsion from the point of view of sending humans to Mars. Its conclusion was that a mission powered by nuclear propulsion is feasible by 2039 if a rapid and significant technology development program began immediately. To understand this better, I spoke with Bhavya Lal, an expert in nuclear engineering and space policy, on this month's Space Policy Edition podcast.

The Biden administration did not provide funding for nuclear propulsion research in NASA's 2022 budget request, choosing instead to invest in fission power systems for the lunar surface. This is in line with the Trump administration's Space Policy Directive #6 released last December, which endorsed the need for nuclear propulsion but recommended investing in surface power systems first.

Congress, however, is likely to restore at least $100 million to NASA for nuclear propulsion next year, though that is itself far too little to support an uncrewed demonstration mission, let alone a human-rated system scaled for Mars.

We should not shirk from the complexity of this problem: either type of nuclear propulsion would require a Mars spacecraft on the scale of the International Space Station or larger, and faces steep engineering hurdles that require many billions of dollars of investments over the next two decades. Is the outcome worth the cost, particularly as NASA and its partners are attempting to establish a permanent presence at the Moon?

From the point of view of sending humans to Mars, nuclear propulsion is an expensive, uncertain, potentially transformative technology. And this is, of course, why we have government-funded research and development to begin with. The outcome may be decades away, but investing in space nuclear systems in a strategic way — one that benefits science, commerce, and national security in the near term — could yet pave the way for humans to the Red Planet.

Until next time,

Casey Dreier
Chief Advocate
The Planetary Society

Space Policy Highlights


For Humans to Reach Mars, Advances Are Needed in Space Nuclear Propulsion Technologies ( "Using nuclear propulsion technologies to support a human mission to Mars in 2039 will require NASA to pursue an aggressive and urgent technology development program...NASA should commit within the year to conducting an extensive and objective assessment of the merits and challenges of using different types of space nuclear propulsion systems and to making significant technology investments this decade."


GAO rules in favor of NASA—Lunar Starship is a go ( "The Government Accountability Office denied protests by Blue Origin and Dynetics against NASA’s award of a Human Landing System contract to SpaceX in April. GAO determined NASA did not violate procurement laws or regulations and its evaluation of the bids was reasonable. Blue Origin vows to continue its efforts to secure a second contract nonetheless."

Not unrelated: Bezos surprises with offer to pick up $2 billion of HLS tab


The National Space Council has a new executive secretary ( "The White House announced that Chirag Parikh will be executive secretary of the council, responsible for its day-to-day activities. The council is chaired by Vice President Kamala Harris. Parikh was director of space policy at the National Security Council from 2010 to early 2020 he joined Microsoft, where he was senior director of Azure Space, the company’s effort to extend its cloud computing platform to space applications."


The Europa Clipper will take a Falcon Heavy—not an SLS—to Jupiter ( "After years of speculation, NASA officially announced that SpaceX's Falcon Heavy would launch what is arguably the space agency's most important Solar System exploration mission of the 2020s—the Europa Clipper. Slated to launch in October 2024...the deal also saves NASA about $2 billion."

The Planetary Society asked Congress last year to loosen restrictions on the Europa Clipper mission that would allow NASA to select the best launch vehicle available. This decision saves the project time and money, and frees up an SLS for use in the Artemis program.

Planetary Radio: Space Policy Edition

Planetary Radio Space Policy Edition logo

Mars via the Nuclear Option, featuring Bhavya Lal

Can nuclear propulsion fundamentally transform our ability to send humans to Mars? Bhavya Lal, a policy and nuclear engineering expert now working at NASA, helped write a new report on the topic for the National Academies of Sciences. She joins the show to talk about the advantages of various types of nuclear propulsion, the engineering and policy challenges that face them, and the role of government versus the private sector in developing and deploying transformational technologies.