A new approach to selling human Mars explorationby Joseph F. Smith
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| Stop work and pretending we will send humans to Mars in the next 20 years, and divert the money spent from NASA’s human exploration programs to the robotic exploration program. This will increase public support for exploration and may be the only way to start a human Mars program. |
Currently we spend about $4 billion a year on exploration programs, primarily for development of the Space Launch System and the Orion spacecraft. At the present time, there is a grand total of one human mission on the books for this vehicle combination. At the present rate, we will not get science from a program of human travel to Mars until the 2030s, or the 2040s, or maybe the 2050s, if ever. And how would the cost and amount of science from a human Mars program be compared to the science from a robotic science and exploration program? If we make some assumptions, we can do some simple math and compare science and cost between the two approaches.
The analysis that follows is based on one assumption. All of the discussions in this paper on cost are assuming fiscal year 2016 dollars. That means there is no impact included or implied for inflation or other factors that can affect the cost over time.
Science from a human Mars program
Calculating the amount of science a human Mars exploration program would generate is difficult, because we don’t have a baseline mission to use as a basis for the calculations. So, lets define a human Mars program that many of the readers of The Space Review are familiar with. That is the human Mars exploration program described by Andy Weir in his excellent book The Martian (see “Review: The Martian”, The Space Review, February 17, 2014). Weir describes a set of five Ares missions to the Martian surface, each mission has a crew of six, and the duration of their stay on the surface is 30 sols (Martian days). Weir also assumes that of the surface crew of six would have one geologist. However, the non-geologists will also be able to do geology on the Martian surface. So we can make a reasonable assumption that the six properly-trained crewmembers on the surface would be approximately equal to four trained geologists. We can debate this point, but it’s a reasonable working assumption.
We will assume that the Mars surface crew could work for all of the 30 sols they are on the surface as a best-case assumption. But this is probably not valid since the crew should require at least a couple days of rest during their stay on the surface. But with these assumptions we can calculate that each of these missions would provide an opportunity for 120 geologist-equivalent sols of science. This is would be a total of 600 geologist-equivalent sols of science for the entire set of five Ares missions. We will guess that an Ares Program would cost of $400 billion, but I have seen estimates all the way up to $1.5 trillion. But using the $400 billion cost estimate, each sol of geologist-equivalent work would cost $667 million. Some will argue with my guess for the cost of this set of Ares missions, but I believe that this is as good as anyone else’s guess, and is probably low.
Budget for robotic planetary science and exploration program
How much geologist equivalent work would we expect from an aggressive program of robotic missions to Mars? We can also estimate that if we make some assumptions.
The first thing we need to do is estimate the number of missions we need to consider. We can do this by looking at the current NASA budget for fiscal year 2016 to see what money is available, because as of this writing Congress has not passed an appropriations bill for fiscal year 2017.
| How do we compare the amount of work that a robotic rover can perform compared to trained geologist? |
Where would we get significantly more money for the planetary science budget from within the NASA budget? Looking over the budget, we are proposing to cancel all of the expenses currently slated for the exploration budget and move them over to the planetary science budget for more missions. If we do this, we have much less reason to keep the Johnson Space Center (JSC) in Houston open, especially if we move the International Space Station (ISS) operations to Kennedy Space Center (KSC) in Florida. Likewise, without the work on the development of the Space Launch System there would be much less work to perform at the Marshall Space Flight Center (MSFC). So we should be able to move the residual work from MSFC to KSC, Goddard Space Flight Center (GSFC), Jet Propulsion Laboratory (JPL), or one of NASA’s three aeronautics research centers.
This would allow NASA to close JSC and MSFC, thereby saving this money would be important to being able to use the entire $4 billion in the exploration budget to the Planetary Science and Exploration (PSE) budget.
Furthermore, the ISS is expected to end operations and be deorbited somewhere about 2024, or perhaps later. For the sake of this analysis we will assume that the ISS operations budget of $3 billion will be available to the PSE budget starting in fiscal year 2026.
Number of robotic Mars missions
The cost for the missions we are discussing is spread out over a number of years; the high level of development usually takes three to five years. However, the length of the mission operations is as long as necessary, and can’t be reasonably described here. But the length of the mission operations can be ignored, since we are only looking at estimating the number of missions that are possible. Thus, we will make a simplifying assumption that all of the money for a mission is allocated to a single year.
The current Planetary Science program has three sizes of missions, based on the size of the project budget: the Discovery missions which cost about $500 million per mission, the New Frontiers missions that cost about $1 billion per mission, and the larger Flagship missions. We will assume that a Flagship mission costs $2.5 billion, which is also the cost of the last Flagship mission, the Curiosity Mars Rover (2011).
In 2016, the planetary science budget was $1.6 billion. We will assume for the purpose of this analysis that we can move the human exploration budget of $4 billion to the new PSE area in fiscal year 2019 for a total budget of $5.6 billion. Furthermore, starting in 2026 we will move the $3 billion for ISS operations over to the PSE budget. This gives the PSE a total $8.6 billion per year. In this analysis, the last year of the surge in this new PSE program will be fiscal year 2040.
For this analysis we will assume that only 40 percent of the PSE budget is used for Mars surface exploration, in the form of rovers. We assume that the rest of the PSE budget is used for Mars orbit science, Mars infrastructure (especially communications infrastructure), and science at other planets, asteroids, and comets. This 40 percent number is an assumption without significant justification.
With this allocation of Mars surface spacecraft we are assigning a 25-percent share of a flagship mission for 2016 until 2020 to cover the costs of the Mars 2020 rover as a simplifying assumption. With the reprogramming of the exploration funds to the PSE budget starting in 2018, we have assigned one Discovery class and one New Frontiers mission and 25 percent of a Flagship mission for fiscal years 2018 through 2024 (one flagship mission every four years). In 2025, there are two Discovery and one New Frontiers class missions. This gets us to the final period of 2026 to 2040. For this period we have assigned two Discovery, two New Frontiers missions, and one fifth of a Flagship class mission to each of these fiscal years. This means that there would be a new flagship mission every five years.
Mars rover costs
The next question is, how do we compare the amount of work that a robotic rover can perform compared to trained geologist? This is a difficult question to answer in a reasonable fashion, so I will have to defer to somebody much better qualified than myself. Another engineer who worked directly with Dr. Steve Squyres on the Mars Exploration Rover (MER) 2003 project has told me that Squyres thought that each of these rovers could perform about as much field work as a trained field geologist could perform in one day. I assume that the time period he’s using for comparisons is the 90-sol period of the MER prime mission. The conversion would then be that one Earth year on the surface of Mars a rover could perform four geologist-equivalent sols of work. This is the conversion rate used in this analysis.
| Another issue is that robots can’t be as effective as humans, because science requires a human in the loop for many decisions. However, this ignores the fact that humans are always in the loop in decision-making. |
Another factor to consider is how long would a rover would (on average) be operational on the surface of Mars. We have three data points to work with, in the form of the three rovers landed on Mars so far this century. The Spirit rover lasted 2,269 (Earth) days or 6.2 years, the Opportunity rover has lasted 4,645 days (and still operating) or 12.7 years, and the Curiosity rover has lasted 1,529 days so far, or 4.2 years. The Opportunity and Curiosity rovers are both still operational and either or both of them could still be operating for many more years before they have a mission-ending failure. The average mission length of these three missions as of this writing is 7.7 years. Since Opportunity and Curiosity are still operating, I have rounded this up to 8 years, and used this figure.
This comes out to a huge increase in the number interplanetary robotic spacecraft operating at one time. The peak number of rovers operating on the surface of Mars grows to 34 for fiscal years 2035–37, and with the launch of a flagship mission in 2040. This leads to an incredible 648 years of rover operation on Mars, and using the previously discussed conversion factor, we get 2,592 geologist-equivalent work days.
When we consider that the total PSE cost is $166 billion, this leads to a cost of $64 million for each geologist-equivalent workday. If we only use the cost of the Mars surface rovers, then the cost of each geologist-equivalent workday is reduced to less than $26 million. This is only 3.9 percent of the cost of a geologist-equivalent workday provided by the Ares program. For less money, the robotic program provides more than 4.3 times the number of geologist-equivalent workdays.
Quality of rover science
Many have argued that humans generate superior quality science to the science delivered by robotic spacecraft. This may or may not be true, but many of the arguments to this proposition are not reasonable, and will be quickly examined herein.
Nobody will say that robotic spacecraft can perform equivalent surface science in the same time scale as a human. This is why we are using a 90-to-1 ratio of science from robotic spacecraft to a trained human. This ratio takes care of the issue of the difference between the two types of science.
Another issue is that robots can’t be as effective as humans, because science requires a human in the loop for many decisions. However, this ignores the fact that humans are always in the loop in decision-making. It’s just that the humans are back in the mission control center back on Earth, and not, in this case, on Mars. These humans look at the observations taken by the rover, use this to determine the next set of activities, and then send the proper commands to the rover for the next tasks that it will perform. The robotic rovers perform their tasks autonomously, but humans decide on what tasks the rover will perform.
One might say that, because of the 90-to-1 ratio for robotic to human science on another planetary body like Mars, there is a huge latency in the robotic science. This is correct as far as it goes, but it doesn’t go far enough. We will have to wait for 20, 30, or 40 years or more before we start to get the human-collected science. Once we make a commitment to move towards a robotic-only science on the surface of Mars, we will start to receive science within a few years, because it won’t take 30 years before we are ready for the first launch. Instead, we have the technology to start the first mission immediately. We know this because we have already done it, landing and operating rovers on the surface of Mars three times in the last 15 years.
Some might say that the dexterity of rovers isn’t as good as the dexterity of a space-suited human. This is true in some sense, but on others rovers might have an advantage. For example, in the area of sample manipulation, there probably is a slight advantage to the human, even when the person is handling a sample with a pressurized gloved hand. But in the case of the rover, the manipulator used to handle the samples will be specifically designed to handle the samples. We can give an advantage to the human, although it may be close.
Another issue related to dexterity can be specific sites a rover can access relative to those available to a human, such as up a cliff. This may be generically true, depending on the implementation of future rovers.
| While a human Mars exploration program would be very exciting, and most people would like to see it happen, very few people really think it would be worth the great expense. |
Lets look at this question in greater detail. A human can go up a cliff to collect some interesting samples if they can be identified from level ground. However, before it is possible for a human to attempt to scale a cliff, the crew safety team in the back room at the Mission Control Center (MCC) will need to review and approve the attempt, and also approve the procedure that has been written to perform the cliff sample collection. A human will not be able to collect some samples, no matter how important they seem. This is because the safety team will decide if this activity can be performed with adequate safely.
Well, there is a solution to this safety issue. The human can send a drone designed to scale the cliff in order to collect the sample. By definition, the drone can be sent to places that are unsafe for a human, because the drone is a machine and therefore expendable, while a human is not. But if this is a solution for the humans, it is also the solution for the robotic mission. The rover can carry a small drone, similar to the one a human may use, that is designed to climb the cliff. This drone will be able to scale the cliff and collect the sample. If the human directed drone can collect the sample in four hours (a quarter of a workday), then the 90-to-1 ratio implies that the rover-carried drone can do the same task, under the control of the humans in the control center, in 15 days.
There is one issue where the robotic approach to Mars exploration is clearly superior, and where the human missions can’t compete. That issue is the number of sites that can be visited where science can be performed, and in some cases samples collected. The Ares program as outlined by Weir has the crews visiting five locations on the surface of Mars. The crew at each of the Ares landing sites will be able to sample the geology within tens of kilometers of the landing site. Sending the crews further would be unsafe, if the surface vehicle carrying the crews were to break down.
Crew and mission safety would be the most important factor in the selection of the landing sites for the Ares program. This means that the interesting geology will be far from the landing sites, and it will be necessary for the crews to travel miles, probably tens of kilometers just to get to the interesting geology.
Of course, with the expense of the Ares program as outlined, we expect that some money can be spent to send a few rovers to gather samples in the area around the landing site, but this will just increase the area of collected samples by tens of kilometers. This is not a very large area on a planet the size of Mars.
The robotic program outlined here would have up to 79 spacecraft for Mars surface operations. We could assume that all of them would go to 79 different sites. Another approach would be to set up a program for collection of samples for return to Earth. If we were to assume that the rovers would only go to 50 locations on Mars, then we have 29 rovers that can be used to collect samples from more areas around the landing sites and return them to Earth. We could select 10 of the most interesting sites (twice as many as the Ares program) and send an extra two rovers to those locations (one location would only get one extra rover), to do more science and collect more samples. There would then be one vehicle used to lift the sample back into Mars orbit, where it would transfer the sample to an Earth Return Vehicle. However, the total mass of the samples returned by the two approaches can’t be adequately assessed and understood at the present time.
It will be possible to send the rovers to landing sites that would be unsafe for a human Mars landing site. Less money would be as risk and only a robot would be as risk for each landing attempt, so a higher risk would be acceptable. Not only that, but having experience of nearly 80 landings on Mars would mean that the operations teams would be extremely well prepared and practiced in the art and science of Mars landings. This means that the rovers can be sent to more dangerous but geologically interesting sites on Mars.
Using the robotic program to jumpstart humans to Mars
And now we get back to the title of this essay, how to use a new approach to jumpstart a program to send humans to Mars in a reasonable timeframe.
The first thing we need to accept is that a government or private human Mars exploration program will be extremely expensive. Certainly this will have a cost on the order of hundreds of billions of US dollars, whether it was done by a private organization or a government.
While such a program would be very exciting, and most people would like to see it happen, very few people really think it would be worth the great expense. This is probably the main reason that even though activists have been pushing for a human Mars program for nearly 50 years, we are no closer today than we have been at any point during this time.
There are only a few ways to get a human Mars program approved and really moving forward. One way is to reduce the cost of the program relative to the size of the economy. This is very difficult due to the number of technology and programmatic unknowns, and the current lack of technology solutions for many of the remaining problems that such a program must solve. A better approach to reduce the size of the program relative to the economy is to grow the economy, so that in a relative sense the program is more affordable. But this will take decades to sufficiently increase the size of the economy.
| A high level of robotic activity would have an effect on the general public, which would grow accustomed to it. Public support for planetary exploration should grow significantly. It might even grow enough to provide the level of public and political support necessary to see the approval of a human Mars program. |
The second method is to increase the utility of a human Mars program to the general public. But how can that be accomplished? I am sure that there are many ways to do that, but I believe that one way to do that is to implement a robust robotic exploration program as a marketing aide before proposing that we send humans to Mars. This would prove the value of exploration to the public, Congress, and whatever administration is in office at the time. This must be an affordable exploration program. Probably the only way to provide this proof is with an extensive robotic exploration program.
Today, the media likes to detail the significant events of the current moderate level of robotic exploration. We see headlines and stories about these spacecraft and their discoveries up to a few times of year. If we were to constantly have dozens of spacecraft exploring the solar system, these headlines would be much more frequent. Stories of new discoveries would be occurring on a monthly and sometimes even a weekly basis. This high level of activity would have an effect on the general public, which would grow accustomed to it. Public support for planetary exploration should grow significantly. It might even grow enough to provide the level of public and political support necessary to see the approval of a human Mars program. This is something that we haven’t seen in the last 45 years.
One final point to make is that some may try to make an exception to this discussion by saying that the quality of these calculations makes the entire argument irrelevant. Certainly, these calculations are only of a back-of-the-envelope quality. However, my purpose was not to develop a complete program plan, but to provide quick look at the concept to see if it deserves further consideration. I think that these numbers do provide a sufficient reason to start a discussion, if that is what the community desires.