Dr. Ian Crawford, Reader in Planetary Science and Astrobiology at Birkbeck College London, has published a paper that seeks to dispel the myth that robots are more efficient than humans for conducting space science.  The paper, published in Astronomy and Geophysics, is available for PDF download here.

Dr. Crawford says, “There is a widely held view in the astronomical community that unmanned robotic space vehicles are, and will always be, more efficient explorers of planetary surfaces than astronauts. Partly this is due to a common assumption that robotic exploration is cheaper than human exploration (although, as we shall see, this isn’t necessarily true if like is compared with like).”

According to Crawford, “The relative efficiency of human over robotic exploration of planetary surfaces is in fact well recognized by scientists directly involved with the latter on a day-to-day basis.” He quotes Steve Squyres, principal investigator for the Mars exploration rovers Spirit and Opportunity, who states, “The unfortunate truth is that most things our rovers can do in [a martian day] a human explorer could do in less than a minute.”

As supporting evidence for this point, Crawford examines the number of peer-reviewed scientific papers produced by the Apollo expeditions and the unmanned Mars program. Crawford finds that, “Apollo was over three orders of magnitude more efficient in producing scientific papers per day of fieldwork than are the [Mars exploration rovers]…. The ratio of costs between human and robotic missions, while large, may nevertheless be smaller than the corresponding ratio in scientific productivity.”

Crawford points out that cost comparisons only make sense when comparing like to like. “In terms of cost per site ,Apollo was only 12 times as expensive as [Mars Science Laboratory], yet each Apollo mission was vastly more capable…. Human missions like Apollo are between two and three orders of magnitude more efficient in performing exploration tasks than robotic missions, while being only one to two orders of magnitude more expensive.”

Crawford does not see this pattern changing in the future. “The cost of the robotic exploration of Mars has not been decreasing as technology advances, but rather has been increasing steadily . There is a good reason for this – planetary surfaces are large, rough, rugged places, not at all amenable to exploration with small, cheap rovers no matter how much ‘intelligence’ can be built into them.”

Crawford identifies several specific advantages which humans have over robots:

Dr. Crawford may, in fact, be understating the case. The cost of human spaceflight may decrease significantly in the near future. SpaceShip One was dramatically cheaper than the X-15 (which itself was substantially cheaper than unmanned expendable rockets with similar performance). There is every reason to believe that similar dramatic reductions in the cost of orbital and planetary spaceflight will occur in the future. SpaceX has already taken some first steps down that path, but there is a long way to go.

On the other hand, the cost of unmanned robotic missions may fall significantly with the development of new technologies such as planetary CubeSats. We may see an interesting “race to the bottom” in costs.

It’s important to recognize, however, that human space exploration is not an activity carried out solely (or even primarily) for scientific reasons. Science may benefit from becoming a free rider (or, at least, a low-cost rider) on missions and programs that are conducted for economic, political, or even personal reasons. A good example is the new generation of low-cost suborbital spacecraft, developed initially for self-funded citizen explorers (“space tourists”), which are finding wide application to suborbital science. Organizations such as NASA and the SouthWest Research Institute are taking advantage of these developments to buy low-cost rides for professional researchers, while Citizens in Space has acquired flights for citizen scientists.

There is every reason to believe that orbital and planetary spaceflight will develop the same way, although their development will take a bit longer. As Burt Rutan likes to say, all progress begins at the low end.