One final thought on the Big Science/ Space Chronicles stuff from last week. One of the things I found really frustrating about the book, and the whole argument that we ought to be sinking lots of money into manned space missions is that the terms of the argument are so nebulous. This is most obvious when Tyson or other space advocates talk about the need for “inspiring” people, but it shows up even in what ought to be relatively concrete discussions of actual science.

Take, for example, the argument over humans vs. robots. Given the success of the robotic missions to Mars and other bodies, many people ask why we should bother to send people to any of those places. Tyson himself estimates the cost of sending a human to be around fifty times the cost of sending a robot, and says that “if my only goal in space is to do science, and I’m thinking strictly in terms of the scientific return on my dollr, I can think of no justification for sending a person into space.” But then, he turns around and tries to justify it on fairly standard grounds: that humans are more flexible, while a robot can only “look for what it has already been programmed to find.” Having humans on the scene would enable faster and more “revolutionary” discoveries.

This is an argument that sounds fairly convincing on a surface level, but on closer inspection it breaks down in two ways: it’s too generous to humans, and too hard on the robots.

One line of argument in favor of sending humans is that, being autonomous multi-function life forms, humans can notice things that robots wouldn’t, and adjust accordingly– Tyson cites the example of Apollo 17 astronaut Harrison Schmitt, a geologist by training, noticing some oddly colored soil that turned out to be interesting after he sampled it. The claim being that a robot, following a strict program, would not be able to adjust on the fly and sample that soil rather than some other soil.

Which would be true, if we were dealing with Apollo-era robot technology. But we’re not. In fact, the actual existing robot rovers on Mars have the capability to do exactly what he wants: they send back pictures of the surface of Mars to Earth, where human geologists study them. Based on the pictures, they select what targets to investigate on more or less the same criteria Schmitt used: that rock is an interesting-looking shape, or this spot is a different color than that other spot. That’s been the beauty of the robot rover program from the beginning.

And, in fact, if you go down the list of discoveries made by the Mars rovers, a large number of them have been serendipitous in exactly the manner that you’re supposed to be able to get from a human. The hematite “blueberries,” for example: scientists on Earth looking at the pictures sent back by Opportunity saw some odd little spherules on the ground, and directed the robot to investigate.

This also oversells human ability a bit– by definition, serendipitous discoveries have an element of chance. There’s no guarantee that even a human geologist would happen to notice everything interesting. In fact, tons of psychology research has shown that humans are just as susceptible to not noticing things as robots are supposed to be– people miss gorillas right in front of them, after all. A human geologist on Mars with limited time to work might well miss some things that would turn out to be interesting.

Another branch of the flexibility argument holds that humans could move more quickly past problems– Tyson cites the 12 hours that it took to navigate Spirit past the airbag from its lander, and says that a human could’ve cleared it in seconds– and make on-the fly repairs– “Give a person a wrench, a hammer, and some duct tape, and you’d be surprised what can get fixed,” he says. This again, is true to a point, but also elides a lot. For one thing, a mission including humans would be vastly more complicated than a robot mission, and a more complicated mission has many more possible failure points. So, yes, a human is less likely to be thwarted by an airbag on a ramp, but then a robot doesn’t have to worry about maintaining a pressurized breathable atmosphere, or securing supplies of food and water, or a comfortable temperature, or adequate radiation shielding, or waste disposal, or any of a host of other problems that preserving human scientists on Mars and returning them to Earth would entail. There are lots of possible failures that are just as stupid as an airbag on a ramp that could easily trap a human inside for as long as Spirit was stuck.

The repair argument also has its flaws, the most obvious being that any repairs would be limited by the available materials. Glib comments about duct tape are great if the only failures you worry about are gross mechanical ones, but nobody’s going to make a new Mössbauer spectrometer out of duct tape. Any Mars mission worth doing will include a lot of highly specialized components, and you can’t send spares of everything.

It also slights the ingenuity of the humans controlling the robots. Spirit famously had one of its wheels lock up in 2006, but the scientists “driving” it not only worked out a way to get around the stuck wheel (by driving the rover “backwards,” basically), but it turned out to be the vehicle for another of those serendipitous discoveries: the dragging wheel scraped away dust, revealing a silica layer underneath.

So, again, a lot of what appear to be more concrete arguments in favor of human space missions don’t seem to hold up very well, and end up turning on things that are as vague and unquantifiable as “inspiration.” There’s no question that certain things would go faster for humans than they do for robots, but then, they would need to go faster, because there’s no way we’d be able to leave a human on Mars for the nearly 3000 “sols” that the current robot rovers have been operating there. And it’s not at all clear that the small advantage in flexibility from having a human there rather than at the other end of a radio link would make a positive difference.

The one unquestionable advantage would be that a mission putting humans on Mars would eventually return to Earth, and could bring samples back that could then be subjected to a vast range of tests that can’t be done by a robot rover with a limited instrument set. Which is true, but then, you could get the same thing from a robotic sample return mission, at one-fiftieth the price.

So, while the pro-human arguments based on science sound convincing at first, they’re ultimately not that great, and fall back on the same sort of vague and airy platitudes as the general “inspiration” argument. And given the gigantic cost multiplier involved in sending humans rather than robots (or in addition to robots), I’d really like to see more than that.


  1. #1 Anton P. Nym
    May 9, 2012

    I still wonder, thirty-five years after the event, what a manned mission would’ve made of the Viking Life Sciences anomalous results… that’s the best argument I can think of for manned planetary missions. (And that’s far from a knock-out blow in its favour, I’ll admit.)

    — Steve

  2. #2 Emory Kimbrough
    May 9, 2012

    Even if you believe that human missions to Mars and beyond are so glorious that they’re ultimately the sole purpose of having a space program, you should STILL favor robotic missions today.

    First reason, you have to send numerous robots to survey and understand your target before planning the scientific goals, tackling the picky engineering details, and risking the lives and resources of a manned mission.

    Our civilization currently excels impressively at robotic missions, but has very poor capability for deep manned missions. The 50:1 cost ratio shows that. Even if the technology and expense issues somehow start improving at an astounding pace thus enabling fantastic manned missions unexpectedly soon, we’d find that…OOPS!!!…we’re gonna be badly delayed in actually USING our imagined wonderful new manned technology because now we’re stuck waiting for years catching up on all those necessary robotic missions that we could have done so well so much earlier.

    Second, if manned missions to Mars and beyond ever become practical, that will likely require new and different approaches to propulsion and other technologies. It’s a lot easier, quicker, cheaper, and safer to try out bold new approaches on robots. So, curiously, focusing on robots instead of humans now is probably a far faster route to manned-flight technology breakthroughs.

    Summary – Favoring manned missions over robots now and in the near future results only in rather dull manned missions, and ironically it badly delays exactly those man-on-Mars-and-beyond fantasies that are motivating the manned-mission cheerleaders to demand lots of funding now.

  3. #3 Anonymous Coward
    May 9, 2012

    You’re correct in your assessment of humans vs. robots, and you’re too charitable with respect to Tyson.

    I think the 50:1 is also baloney. The ISS bill to date is (according to Google) pushing 150 billion. The Spirit/Opportunity Mars Exploration Rover Mission ran (according to Wikipedia) 1 billion. I’m no expert, but I think the scientifically, Spirit and Opportunity were much more productive than the ISS. Actually, I can’t think of a single significant scientific discovery that came from the ISS.

    These days, any decision to send humans into space has nothing to do with science and everything to do with spectacle. Maybe spectacle is OK. The Romans had the Colosseum, we have the NFL and manned space flight. Why not? But let’s stop pretending we send humans to space for science, and just admit we do it for amusement.

  4. #4 Jim Plassard
    May 9, 2012

    I am a funding proponent but I would love to see advancement in both areas. There is a symbiotic relationship between manned and unmanned exploration. Robotic exploration is obvious cheaper and safer for the human explorers who get to sit behind a console and sleep in their own beds at night. Our space program is in dire shape and needs some small wins so that we can stop talking about renting space station trips from the Russians. Unmanned projects fit the bill now but they need to be geared toward manned projects in the future. The psychological issue of ‘doing it ourselves’ will always need to be fulfilled.

  5. #5 John Novak
    May 9, 2012

    Not to mention, the “inspirational” part of humans being in space comes with the downside of putting humans in the path of so many extreme harms it’s hard to count them all… and every time something goes wrong, the whole program gets shut down for a few years.

  6. #6 John Novak
    May 9, 2012

    Actually, come to think of it, you can make almost exactly the same arguments for robotic space craft vs manned missions, as you can for unmanned vehicles of any stripe (military UAVs, Google robotic cars, etc) vs human-piloted ones– at some point, the human becomes a cost bottleneck.

    It might be reaction time, it might be training time, it might be reduced vehicle performance to keep the squishy humans alive, it might be life support/safety equipment, etc, but that point does come. When it does, you need to look at those variables rationally, not, uh, inspirationally.

  7. #7 Lyle
    May 9, 2012

    If you sent a human to mars the human would be in a can and would not directly interact with the environment. So the human would see things, but it turns out cameras can see more and better with a larger range of wavelengths. So its not clear what the 50 to 1 cost ratio buys you.

  8. #8 kevin r
    May 9, 2012

    The voyager, hubble, and mars rovers have provided a wealth of inspirational images and have fired the imagination of millions. I would love to see robotic missions to Titan and Europa. Those are both doable for a fraction of the cost of a manned mars mission

  9. #9 Roland
    May 10, 2012

    Robots are poised to eliminate most USAF fighter and bomber pilots. Commercial diving at depths beyond 300′ is declining due to advances in remotely-operated vehicles. The trend is clear. Dangerous, dull, or dirty-time for robots. I for one welcome etc.-you’ve heard it before.

  10. #10 Jim C
    May 11, 2012

    Shall we all look forward to the day when Humans are simply lumps of unthinking protoplasm tended by a vast network of robots who have surpassed us in every field?

  11. #11 Gabe Spradlin
    May 11, 2012

    I have several counter-points so this comment is long…

    I have not read the Tyson book, but I have strong opinions on manned vs robotic space flight. And I think we should clearly be pursuing both solely robotic missions and manned missions augmented with robotic.

    Why am I qualified to have an opinion on the topic? I worked as an Aerospace engineer for 11 years until 2009 (when I’d seen one layoff too many). I have worked on the F-22, the Apache (very briefly), Shuttle payloads, Astronaut training, military satellites (Systems/Controls – pointing lasers at a very small spot a very long way), and Guidance, Navigation and Control on the ISS. And I spent the entirety of my time in engineering school (BSME and MSEE with an emphasis in Controls) working towards the ultimate goal of putting robots into space (hopefully with AI).

    I really, really, really like robots – especially in space.

    That said, I think it is a terrible idea to remove people from space. Manned space flight is worth pursuing despite the costs.

    First, in my opinion, the science derived from the ISS is minimal because of budget issues not for lack of good science opportunities. In the beginning the ISS was designed for science but first we had to get an infrastructure to support people in orbit. Then when the infrastructure was done and the time came to fund the science modules (admittedly after many budget adjustments) the US and our allies weren’t as willing to spend any more money. So not all of the science modules that were planned are in orbit.

    Also, for most of the ISS’s life there have been only 3 people on-board. So long as there were only 3 people on-board they had their hands tied up doing maintenance and operations activities. Now we’ve learned a lot about operations and the hardware is broken in so there are fewer operations related duties (at least that was true when I left in 2005). But the science modules got cut and NASA handed the politicians the ax to do it.

    Most politicians and NASA people seem to focus on the biology of what happens to people in space due to radiation and long term exposure to zero Gs (which is really micro-gravity at the ISS not truly zero G). This gave the politicians (and NASA) a way to say we’re accomplishing ISS’s mission of science in orbit – by studying the people up there. That’s great but I think the biology can, at this stage of our infantile knowledge of biology in micro-gravity, be studied with a host of sensors on-board and upon the astronauts’ return – without interfering while we do other science. My main interest/hope for the ISS (that will never be realized) was Materials. There are alloys you could make in micro-gravity you could never make at 1 G because the 2+ constituent materials will separate before they cool. Also, metals inherently have a crystalline structure. A piece of metal typically exists as a series of crystals bound together. The bonds between crystals are much weaker than the bonds between atoms and thus the failure mechanisms of metal usually revolve around the crystal size and crystal boundaries (where one crystal meets another). For the F-22 APU (auxiliary power unit – small turbine engine) that I worked on the turbine blades were made of a single crystal because that allowed for much better stress and heat characteristics. However, again gravity is one of the limiting factors in our ability to grow a larger single crystal and so the maximum turbine blade size is limited so long as the blade is made on Earth.

    Remember what materials have done for our standard of living and our economy over the past 30 years – graphite, titanium alloys, carbon fibers, and ceramics? Everything has gotten lighter and stronger. I see a whole new wave of materials impossible to manufacture on Earth that brings with it decades of new military, entertainment, and sports equipment all revolving around items much stronger and lighter than ever before. I think it would make us look like we live in the Middle Ages today.

    Second, I have heard since I was high school that we (in the US) are not graduating enough scientists & engineers. China and India produce plenty and we have been importing them as fast as we can for decades. China and India both have manned missions to the Moon in development and have had for years. Obviously, they won’t be the first people to the Moon. So why are spending billions on an exploration mission to a body we’ve already “explored”? Because they recognize, as we once did, that the US mission to the Moon inspired 10s of thousands to pursue careers in science and engineering. And the US gained military superiority and TRILLIONS in economic benefits for the following 4-5 decades as a result.

    The Moon missions made a lot of kids pursue science & engineering in college and once there they didn’t all stay focused on space, NASA, or the Moon but many did stay in science & engineering. Thus we get all the inventions for Space plus a flood of engineers into the rest of the economy fueling our technology based economic growth and productivity gains for the past roughly half century.

    While robotics leads to a number of inventions it doesn’t inspire nearly as many people as manned missions do. The level of passion and dedication (by the engineers) to ISS and Shuttle missions despite constantly getting kicked around for budget was unmatched by anywhere else I worked after leaving college. You had 60 year old engineers with the passion and dedication of a college kid working on manned space programs. I worked (as a contractor or direct) at Allied Signal, Boeing, Lockheed Martin, and a smaller aerospace company name Ball. Nowhere were the engineers more fired up than on the manned space flight missions. Not by a long shot.

    That energy and dedication led to innovation (mostly small things, but some were big) on a nearly weekly basis in the GNC ISS group I worked in. Manned space flight, in my experience, is how you fuel a half century of technological innovation. Innovation not driven by profit motive (which always inspires short term thinking) but tackling the next big obstacle to the men and women whose lives depend on your ingenuity. Huge profits come later and the economy as a whole benefits tremendously. How’s that for payback on your manned space flight dollar? I suggest that any manned space flight mission is a much better way to stimulate the economy than an equivalent amount in tax breaks. You just have be willing to wait approx 10 years to see the benefit. But once you flood engineering schools with students you will see benefits for decades to come. (Manned space isn’t the only thing that inspires; the oceans, climate change, or nanotech might be the next big inspiration I don’t know but it’s the inspiration that’s crucial to these downstream economic benefits.)

    Third, while nothing would make me happier than working on robotic space missions for the rest of my life, robots are limited by the imaginations of those who designed them and those who operate them (for now at least). Every mission is limited by the designers’ imagination but a person on-site brings a level of adaptability that robots commanded by people with 10s of seconds of delay time (travel time of light from Mars to Earth and back) just can’t. The people driving the rovers make much less progress each day than they would if they were on-site due to the delay. They also have to be very conservative with how they operate the rovers because they are limited to essentially just one sense – sight – and that from a camera with a limited field of view providing you data in a non-intuitive way. Would you feel comfortable driving your car through only a camera even if the images were enhanced using false colors and infrared? I wouldn’t – not without a lot of practice in a safe environment. So while the rovers (and their drivers) generate tremendous amounts of science, I believe they would have generated that same science in a much shorter time frame with someone driving the rover nearby rather than 10s of seconds of delay time away. And with proper mission design, it should not add any cost to the rover to make it command-able from Mars as well as Earth since the signals (if memory serves) all pass through a satellite orbiting Mars. (It would however add some cost, mostly in additional software and testing, to the manned portion of the mission.)

    Fourth, I believe we’ve lost our sense of wonder and tolerance for risk in this country. We didn’t expand the US westward without losing a lot of people to Native Americans, disease, starvation, and weather. Those people took that risk because they wanted a better life than they had in the more settled Eastern portion of the country. Today we have astronauts who fully understand the risks of riding a controlled explosion into an entirely hostile environment. So why exactly are we shutting everything down and doing a bunch of soul searching when something goes catastrophically wrong? Did we miss the memo on this being a risky endevour? Were we so arrogant as to assume nothing would ever fail? Or too stupid to realize that when certain somethings go wrong astronauts were going to die? The astronauts realize this why don’t the rest of us? The only real valid questions for me after Columbia were: how best to honor the fallen, and how best to improve the design of future spacecraft to be more robust – fewer ways for a single failure causing a catastrophic failure of the vehicle.

    Our handling of risk in manned space flight is all wrong (and I think indicative of a societal misunderstanding of risk how ot manage it but that’s a much bigger topic than this). We fixate on eliminating the risk of the failure we just witnessed which is utterly idiotic even though it seems entirely rational. It leads to design band-aids that always mean safety design trade-offs because of weight or budget. We eliminate the one failure mode we’ve just seen (even though it wasn’t a failure mode the last 100 launches) while making several other failure modes more likely or more likely to be catastrophic instead of recoverable because of what we did to band-aid the design for the failure we just saw. Assessing the risk and doing nothing is never an option even if the astronauts would be safer for it.

    Finally, as Steven Hawking has suggested we are exactly 1 catastrophe (asteroid, plague, etc) from extinction or near extinction. Sending robots to space is a great idea for a memorial but not a good survival technique.

  12. #12 panax
    May 15, 2012

    The voyager, hubble, and mars rovers have provided a wealth of inspirational images and have fired the imagination of millions. I would love to see robotic missions to Titan and Europa. Those are both doable for a fraction of the cost of a manned mars mission