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© 2006 by Donald F. Robertson.
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This article originally appeared in International Space Review
Donald F. Robertson
Automated spaceflight is cheaper than human spaceflight. That's an accepted axiom throughout the space community. But is it correct?
Is it really cheaper to look for, say, a fossil on Mars with robots than it would be to send human scientists? Several recent events suggest that advocates of exploring the Solar System with robots are wearing few or no clothes.
There is no question that orbiting a single instrument to measure the Van Allen belts costs less than launching a Space Shuttle. But what do we get for our money? This question is rarely asked let alone answered.
These thoughts came to mind when then NASA Administrator Sean O’Keefe decided that launching the Space Shuttle to the Hubble Space Telescope -- far from the safe haven provided by the Space Station -- was too dangerous. Instead, NASA began working to develop and fly a teleoperated robot to attempt the repair of the Space Telescope. The estimated price tag proved to be an astonishing two billion dollars. The National Research Counsel gave the proposed mission a low chance of success and recommended that any Hubble repair be done by astronauts.
As the technical, financial, and political difficulties with a telerobotic repair mount, it now appears likely NASA's new Administrator Mike Griffin will reverse Mr. O’Keefe's decision and okay a Shuttle flight to repair Hubble. There are astronauts prepared to fly the mission whatever the risk.
Shuttle-based repair missions in the past have cost less than a quarter of the estimate for the teleoperated repair. Even if Mr. O’Keefe’s improbable defenses of the robotic mission prove correct, and even with the post-Columbia safety costs, a human mission to repair Hubble should cost no more than a teleoperated one. It would probably cost a lot less, while also having a far greater chance of success.
These are amazing observations. The Hubble Space Telescope is not some alien landscape full of unknown dangers. It is a well-understood, human-made artifact designed for repair with existing tools and interfaces. If there is any job ideal for telerobotics, this repair is it.
Consider a few other largely ignored facts:
Even the most recent attempts to automate complex operations in orbit have a poor track record. The Demonstration for Autonomous Rendezvous Technology spacecraft managed to ram its target, causing near-complete mission failure. This ignominious and expensive loss in Earth orbit hardly improves confidence for automated sample returns from Mars. Most sample return strategies depend on an automated docking in orbit around Mars, where telerobotics will be more difficult than it would be in Earth orbit and true robotic autonomy may be required.
The Russians have been docking freighters automatically to space stations for decades. However, this is a relatively simple operation, the reliability has been far from perfect, and the Russians always maintain a Cosmonaut on site to monitor the approach in real time and take over when needed.
To this date, the only absolute historical cratering record, with real dates attached to it, is for Earth's moon. All dates for planetary surfaces throughout the Solar System are estimates relative to that record. The lunar cratering history was obtained by Apollo astronauts. Despite almost half a century of automated spaceflight, that critical measurement has yet to be duplicated on any other world.
Before the Mars rovers were launched, Steve Squiers, the Principle Investigator for the Mars rovers' Athena science payload, was quoted as saying that the rovers would have ninety days to do what a field geologist probably could do in ninety minutes. While he did not mean the statement the way I am using it, it is undoubtedly true that a human being with a good laboratory could do in a few days everything one of the rovers has spent a year doing.
Asif A. Siddiqi makes a similar point in his outstanding history of the Soviet lunar program "Challenge to Apollo: the Soviet Union and the space race, 1945 to 1974.” During Apollo, the United States and the Soviet Union used human and robot missions, respectively, to return samples from Earth’s moon. On page 740 of the NASA History Office edition of the book, comparing the relative costs of Apollos-11 and –12 with the Luna-16 automated sample return, Mr. Siddiqi argued that, "astronauts conducted a wide variety of experiments on the surface while Soviet controllers were extremely limited in their choice of research. The Apollo astronauts, for example, had a much greater ability to choose particular samples from a very large area compared to Luna-16." Apollos-11 and -12 brought back sixty kilograms of carefully selected samples, while Luna-16 managed 105 unselected grams. While admitting that it is hard to directly compare Apollo with the Luna project, Mr. Siddiqi argued that, in terms of the unit cost and value of its scientific results, Luna-16 "probably was not, as Soviet officials of the day touted, a cheaper and better alternative to Apollo."
I would argue that there is no reason to expect things to be substantially different on Mars. Robots are better than they were in 1969 and 1970, but so are the skills and knowledge of the astronauts building the Space Station. An automated sample return from Mars might "only" cost $10 billion, and return a few grams of rocks. A $50 billion, or even a $200 billion, human mission would achieve far more than five or twenty -- or a thousand -- times the science that an automated mission to Mars could achieve.
It is highly unlikely that any of the robots on Mars, or that we are planning to send to Mars, placed on a terrestrial desert known to have fossils would find one except by purest chance.
What does it actually take to find a fossil on Mars? Probably about what it takes to find one on Earth.
Successfully finding the first fossil at a new location involves intelligently scouting a number of carefully-chosen regions for likely rocks; selecting, collecting, and keeping track of, a very large volume of samples at multiple scales from fine sand to boulders; handling and examining rocks from any angle; cleanly cutting open a large and intelligently selected set of samples along any axis; examining the cuts at a wide range of scales and at many wavelengths; and, most importantly, sophisticated pattern recognition to recognize a fossil once you have seen it. No likely robot will be able to do all of these things in the foreseeable future, yet a single skilled geologist with a limited set of good tools can do them all, quickly and easily.
If sending geologists to Earth's moon and Mars were affordable, no one would be arguing that it is better to send robots. After all, once you have found one fossil, you will to want to find another, and the nature of fossil-hunting is such that the second fossil will probably be almost as hard to find as the first. Then, scientists will start thinking about surveys and global distributions, which will multiply the difficulties by orders of magnitude.
If we really want to find and understand fossils on Mars, the trick is to find a way to get geologists and their supporting infrastructure there, regularly and affordably.
Historically, there has been one sure-fire way to bring down transportation costs, and that is through trade. Suppose a base on Earth's moon separated oxygen from lunar rocks or polar ice and exported it to the Space Station, for astronauts to breathe, to make drinking water, and to fuel the station and "third-party" application satellites. Another base on one of the Martian moons could supply carbon compounds to both the lunar base and the Space Station, to grow food and to make simple structural components to shield and repair application satellites. Raw regolith could be used to shield electronics and astronaut living quarters. Earth would trade sophisticated manufactured goods and trace minerals for refueling and other support of the applications satellites -- and for scientific knowledge of Earth's moon, and of Mars and its captured moons.
Trade. Over time, volumes go up; transportation costs go down. If Earth were trading high technology goods for lunar- and Phobos-derived fuels in orbit, geologists could go along for the ride.
No one should imagine that getting from where we are now to this future universe out of science fiction will be quick or easy. It will take immense effort and a great deal of time, but it is necessary if we want to do real science in the Solar System. With the space station partially built and requiring supplies, new generations of lower-cost commercial launch vehicles, and an apparently near-global interest in returning people to Earth's moon and going on to Mars, the seeds for an early trading economy have been planted.
If we want to understand the history of any Martian life – if we want to move beyond reconnaissance to science – the world’s space agencies must focus on building those early bases and encouraging trade, even if it means dropping a lot of the other “scientific” things they do today.
We've done enough robotic reconnaissance. Now is the time to put on our clothes, step out the door, and explore the neighborhood.
Donald F. Robertson is a freelance space industry journalist based in San Francisco.