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SLS Block II illustration
Development of the Space Launch System (SLS), deemed an essential element of any space exploration pathway by the NRC’s Committee on Human Spaceflight, could force tough decisions about other programs, like the ISS, if NASA’s budget does not increase. (credit: NASA)

Space policy via the rearview mirror

A discussion of the National Research Council report “Pathways to Exploration: Rationales and Approaches for a U.S. Program of Human Space Exploration”

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The long-awaited (since 2010) National Research Council (NRC) report on human spaceflight has arrived (see “A new pathway to Mars”, The Space Review, June 9, 2014), much to the dismay of space settlement and commercial space advocates. This report seems to call for ditching the International Space Station (ISS) to fund a series of Apollo-style space adventures using the Space Launch System (SLS) while dismissing commercial space as “speculative.”1

Unfortunately, the report is flawed by an excessive focus on “What can humans discover?” combined with an unexamined dismissal of “What can we achieve when we get there?” especially as it applies to economic development and space settlement.

As a member of the National Space Society (NSS) Policy Committee, I was involved in drafting formally-approved input to the NRC report generation process. The following material does not attempt to reprise the contents of the NRC report or earlier coverage of it here, and you may find it helpful to read them before continuing with this article. This article is not an NSS position and represents only my personal views.

At 286 pages, the NRC report is long and contains some excellent and cogent material. Chapter 2, titled “Why Do We Go There?” contains a generally well thought out presentation of the reasons for human interest in space.

The report outlines five “pragmatic” rationales:

  • Economic and technological benefits
  • National security
  • National stature and international cooperation
  • Education and inspiration
  • Science

In addition, two “aspirational” rationales are mentioned:

  • Human survival
  • Shared human destiny

Section 2.3, “Enduring Questions,” asks:

  • How far from the Earth can humans go?
  • What can humans discover and achieve when we get there?

These deceptively simple questions do provide some useful guidance. The NRC committee reasonably assumes that the answer to the first question is limited to the Lagrange points, asteroids, Mars, and Moon. Unfortunately, the report is flawed by an excessive focus on “What can humans discover?” combined with an unexamined dismissal of “What can we achieve when we get there?” especially as it applies to economic development and space settlement.

The report next turns, in section 2.4.1, to the economic and technology impact of human space flight. The report states “There is now a substantial space-based element of the communications industry and multiple commercial uses of space-based Earth-observing capability. Clearly, these industries would not exist without the original NASA… development work, but they benefited only modestly if at all from human spaceflight programs.” This statement underlines a key weakness in the committee’s approach. The report does not discuss the vast economic benefits of satellites (which they grossly understate by ignoring location-based services) but those satellites only found their way into orbit in the context of a human spaceflight program. In some cases, the applications (i.e., weather observation) now done by robotic craft were originally envisioned as being provided via crewed space stations.

As a result, the NRC report makes no attempt to look at future robotic space applications that might result from a focus on human spaceflight. For example, there is enormous overlap between developing large space solar power arrays for a solar electric propulsion (SEP) system for flight to Mars or providing beamed power to lunar mines, and developing a solar power satellite for returning power to Earth. There is such a strong synergy between human and robotic applications in space that it is not clear that attempting to separate out the economic benefits of human spaceflight alone is a productive exercise.

The NRC report is burdened with a persistent skepticism toward commercial space activities, and often reports such efforts in a misleading fashion. In section, “Evaluation of Economic and Technological Rationales,” we are given a barebones and minimally referenced discussion of current space commerce trends, with the conclusion that “It is currently impossible to assess whether commercial capabilities will develop to the point that they can create significant cost savings (on the order of tens of billions of dollars) for NASA human space exploration efforts beyond LEO.”

A major implication of the NRC report is that NASA should abandon all human LEO activity, commercial and otherwise, in the name of a drive to Mars.

There is no discussion at all that the prospect for increased traffic to LEO for all purposes, including tourism, might lead to significantly lower costs; or that it may lead to reusable spacecraft with superior operational characteristics relative to existing vehicles or the SLS. This glaring absence seems remarkable given the stated goal of SpaceX to develop just such lower-cost, reusable craft, as well as their considerable progress in this direction. Of course, the efforts of SpaceX, Virgin Galactic, Blue Origin, XCOR Aerospace, and others to greatly reduce launch costs may all fail. However, the NRC report is based on the unstated assumption that over the entire period considered, all the way out to 2054, there will be essentially no progress in rocketry other than that funded by NASA exploration programs, and that for the entire period the SLS as currently envisioned will remain the preferred method for Americans to reach space. It is difficult to imagine a more unlikely foundation for the planning of future space efforts than this.

The committee considers that “even robotic exploitation of space resources for on-Earth use to be a highly speculative idea because of the cost-benefit equation would need to change substantially in order to make such exploitation commercially viable,”2 while failing to mention that “on-Earth” use of space resources is not a current target of any of the companies pursuing the area of robotic asteroid mining for the foreseeable future.

The report lets slip some hostility to commercial space by adding “investments to foster new commercial partners may create a tension in NASA as the goal of the facilitation of new commercial ventures can compete with that of exploration (that is, the goal of answering the enduring questions) in making decisions about program priorities.”3 This statement is not logical, even in the context of the report itself, which holds that one of the enduring questions was to ask “What can humans discover and achieve when we get there?” Surely mining the Moon and asteroids for human benefit comes under the heading of “What can humans… achieve once we get there?” We are in LEO now, and we are just starting to figure out what we can achieve. A major implication of the NRC report is that NASA should abandon all human LEO activity, commercial and otherwise, in the name of a drive to Mars.

The entire direction of the NRC report is highly ironic, as it rejects the possibility that in-space mining might support fueling a Mars expedition. The report also rejects the probability that commercial space efforts will greatly lower launch costs, while focusing on a series of mission plans little changed from those discussed in the 1950s or ’60s.

With regard to the role of human spaceflight and the national security rationale, discussed in section 2.4.2, it is hard to argue with the NRC’s conclusion that there is little connection between the two, and that national security is not a strong rationale for human spaceflight. The section that follows on international stature as a rationale for human spaceflight ends with the statement that human spaceflight has important benefits to the international status of the United States, and also has important geopolitical benefits. The current difficulty with Russia aside, this conclusion seems firmly grounded.4 The section on education and inspiration winds up with the bromide that although spending on human spaceflight may not be sufficient to produce engineers and scientists, there are certainly many scientists and engineers who were inspired by human spaceflight.

The section on scientific exploration and observation, while it supplies a number of excellent pages on discoveries made on the ISS, states “Science done in LEO, other than that directed to furthering human exploration, provides a rationale only for LEO.” This hints at the total rejection of on-going human LEO operations that appears in the conclusion of the report.

The report does mention the shifting boundary between when it might be best to send humans or robots to explore, but there is no systematic examination of where this boundary might end up over the next 30 or 40 years. Since the apparent operating assumption of the NRC is that regardless of progress in artificial intelligence and robotics over a multi-decade interval, humans will still remain the more flexible solution for exploration needs, and thus there is little need to consider a future where robots are vastly more capable than today. The science section ends with “This may change at some indeterminate time in the future.”5

It would seem logical in addressing the role of robots in space exploration to start by developing a baseline understanding of where technology is likely to go over the next 20 to 40 years. Given that driverless cars for general use are being tested today, it seems only reasonable to project substantial gains in robotic abilities in the future, with an ever-narrowing zone where humans have a meaningful advantage in the realm of scientific space exploration. There is a time limit on the “humans are more flexible than robots” argument, and during the next 100 years, with very high probability, this argument will no longer have salience. What the NRC ignores is that the argument could lose salience in 20 years or even sooner. In other words, well before we can get human footprints on Mars, it will be obvious that sending robots for scientific exploration is the better approach.

This leaves us with the “aspirational” rationales. The NRC provides an extremely brief examination of the “survival” rationale in section 2.4.6, running only about one page, and settlement is lumped with “survival.” This discussion is of poor quality, and does not even bother to provide a complete list of reasonable threats to human existence: biological threats are missing, for example. After minimal examination, the NRC blandly asserts that “It is not possible to say whether human off-Earth settlements could eventually be developed that would outlive human presence on Earth and lengthen the survival of the human species.” A reference is provided to S. Brand’s Space Colonies but not to the NASA space colony studies6 or to the classic The High Frontier.7 No mention is made of what the specific obstacles to such settlements might be, although the indifference of the committee to this rationale for humans in space looms as the first that must be overcome.

None of this should come as a surprise to any space advocate: curing cancer, creating jobs, reducing crime, and so on are always going to lead the spending priority list of the average person over trips to Mars.

The NRC report twists space settlement and human survival from a viable stand alone “Horizon Goal” to a mere rationalization for further space exploration of the type exemplified by Apollo—a series of one-shot “missions” with no actual sustainability or permanence. The last line of the section is “This [human species extension in space] is a question that can only be settled by pushing the human frontier in space.” The question of whether a series of one-shot missions to the Moon, asteroids, and Mars might be the best or most cost-effective way to answer questions related to human settlement in space is never considered.

The final rationale section on “Shared Human Destiny and Aspiration” ends on a banal note: “Some say it is human destiny to continue to explore space. While not all share this view, for those who do, it is an important reason to engage in human spaceflight.” The truth of this cannot be argued; its usefulness in determining policy direction remains unclear.

The NRC report then attempts to analyze the impact of the various rationales for human spaceflight. This effort includes a consideration of both value propositions and stakeholder value. Of particular interest is a section where the various impacts of (1) ending all human spaceflight, (2) ending only LEO human spaceflight, or (3) ending only beyond Earth orbit (BEO) human spaceflight are considered. The section on ending only LEO human spaceflight, section, contains a reasonable discussion of significant impacts and risks. Unfortunately, the NRC seems to place little value on LEO human activity, regardless of how long the list of benefits of ISS research, the importance of ISS research for BEO exploration, or the very long list of things we have yet to even start doing on the ISS. Currently, increasing numbers of student experiments are being flown to the ISS;8 the impact of removing these opportunities for student inspiration and their replacement with vicarious observation of BEO astronauts active on multi-year timeframes is not discussed.

When considering termination of BEO human spaceflight, the bias of the NRC against LEO and commercial activities is shown by a refusal to recognize that LEO commercial and scientific operations answer the “enduring question” of what we can achieve in space just as much as BEO human operations would.

These observations need to be viewed in the context of Chapter 3, “Public and Stakeholder Attitudes,” which contains 28 pages of considerable interest and value to space advocates, including a fresh stakeholder survey with raw data provided in the appendices. Alas, the entire mass can be summed up in the following quote: “despite positive attitudes toward NASA, there is relatively little public support for increased spending for space exploration.”9 One can also find this gem: “In comparison to other possible spending priorities, space exploration generally fares poorly. Only foreign aid and welfare spending were less popular than space exploration.”10

None of this should come as a surprise to any space advocate: curing cancer, creating jobs, reducing crime, and so on are always going to lead the spending priority list of the average person over trips to Mars. Since NASA and space advocates have failed to connect space to economic growth, personal security, or long-term survival, it is to be expected that the average person sees no reason for more spending on humans in space.

Scott Pace, director of the Space Policy Institute at George Washington University and a member of the NSS Board of Governors, recently said, “What’s the question for which space is the answer?”11 This is a reasonable thought to entertain. Of all the rationales listed above, “space” is the singular answer for only one, species survival via space settlement. All the other rationales can be satisfied on Earth in other fashions. Until human survival via space settlement becomes the “Horizon Problem” around which NASA is organized, we are unlikely to achieve an enduring policy consensus. Organizing around Mars as a horizon goal, as the NRC does, is dangerously shortsighted and fraught with peril, as will be seen below.

Chapter 4, “Technical Analysis and Affordability Assessment of Human Exploration Pathways,” comes last and contains both the most interesting and the most depressing material in the report. The committee has chosen to advocate for “pathways” as distinguished from “capability-based” and “flexible-path” approaches of other reports. A “pathway” consists of a set of design reference missions (DRMs) that lead to a particular goal or set of goals. As the report states, “The committee is not recommending one pathway over another, but is does recommend… that NASA ‘maintain long-term focus on Mars as the “horizon goal” for human space exploration.’”12

Since the NRC committee has already dismissed economic development and survival/settlement as possible reasons for humans to be in space, and limited the scope of exploration to the Lagrange points, the Moon, Mars, and the asteroids, the content of the “pathways” becomes predictable. In addition, the DRMs, although drawn from a number of sources, and sharing some common technologies and vehicles, retain the flavor of the Apollo program: one-shot enterprises with minimal infrastructure left behind.

We are in for a “Thunderdome” style cage match between SLS, ISS, and any new human exploration projects. Assuming a flat budget and continued use of the expensive SLS system, the ISS must be ditched to do anything new in human space exploration.

Finally, all planning assumes the de-orbiting and non-replacement of the ISS at some date in the 2020s, although the report admits that the longer the ISS operates the better chance it will have to answer important questions related to BEO human spaceflight. Thus, at the completion of any of the pathways, the US will be left as it was after the end of Apollo: no space station anywhere, no occupied lunar base, no means to reach LEO on a routine basis, no infrastructure on Mars (with one exception)13 , and a big pile of rocks in a few labs. The phrase “pathways” is misleading—they might better be called “tricks” or “stunts”—as they lead nowhere except to the achievement of the stated goal of footprints on Mars.

Overall, the methodology of NRC report is good, with proper use made of sand charts, and detailed examination of budgets. The report assembles a very solid review of the challenges of going to Mars, and makes a strong case that doing so is at least several times more complex, risky, and expensive than going to the Moon. After reading these sections, one is left with the sense that “Humans to Mars” advocates often don’t fully appreciate many of these points, and that the general public suffers from a “If we could put a man on the Moon, how hard can going to Mars be?” syndrome. NASA then finds itself with a related need to “top itself” by going to Mars, since only this goal seems worthy compared to the initial lunar adventure.

A key assumption that receives minimal examination or discussion is that “the SLS would be the primary launcher enabling exploration beyond LEO.”14 One chart of particular interest examines the likely date of “footprints on Mars” based on various assumptions about budget, schedule, and launch tempo.15 This chart shows an earliest possible “Boots on Mars” date of 2033, and a latest possible date of 2054, forty years from today. As the report admits, these dates are based on a long list of optimistic assumptions, and could easily slip by many years. Thus, the NRC report assumes that the SLS will be used for about an additional half century , even though it is based on late-’70s/early-’80s shuttle technology, and that during this entire period there will be no significant advances in rocketry that would call into question this assumption. Perhaps this is a defensible assumption, but it is a largely unexamined one in the context of the NRC report.16 Even a brief survey of current rocket engine development efforts outside of NASA suggests a strong likelihood that the SLS will be visibly obsolete on its first flight, and a true horse and buggy operation by 2054.

The dirtiest secret in the report resides in the various budget charts. As can be easily seen, we are in for a “Thunderdome” style cage match between SLS, ISS, and any new human exploration projects. Assuming a flat budget17 and continued use of the expensive SLS system, the ISS must be ditched to do anything new in human space exploration, absent significant NASA budget increases that have not been visible over the past decade, and that are even less likely in the future. Even with ditching the ISS, the new funds available are modest and will not support humans to Mars.

Like many past commissions on human space exploration, the NRC report concludes with a plea for more funds, for consensus, and for leadership, all the while acknowledging the coming ISS/SLS “cage match,” saying “Maintaining the ISS and developing SLS leave precious little budgetary maneuvering room to plan the next steps beyond LEO.”18 The most straightforward conclusion that some would draw from this report is that going to Mars is completely unaffordable with current technology and budgets, and that we need to deal out a new deck of cards before starting on this journey. Until we establish the principle of a reusable, permanent, in-space infrastructure that routinely supports new missions, including fuel depots, robotic lunar/asteroidal mining stations, and Lagrange point way-stations that are resupplied using commercial fixed price contracts, Mars will remain forever on our “Horizon.”


  1. NRC report, Section last line.
  2. NRC report, page 2-11.
  3. NRC report, page 2-11.
  4. In later sections the NRC report urges greater cooperation with the Chinese, a proposal that will likely fall on deaf ears in Washington in the context of the current difficulties with Russian and the RD-180 engine. The probable fate of this recommendation illustrates the hazards of writing reports that can be overtaken by events.
  5. NRC report, page 2-26. It is interesting to note that in Section, “A Game-Changing Vision of Robotics,” there is additional discussion of the rapid progress of information technology, and reference to how these technologies might change the space game fundamentally. Alas, this thinking has not been allowed to escape this section and have any impact on the conclusions of the report.
  6. See a list of NASA space colony studies and related books at the following link:
  7. The High Frontier: Human Colonies in Space, by Gerard K. O’Neill
  8. See, for example, the link:
  9. NRC report, page 3-4.
  10. NRC report, page 3-5.
  11. IEEE Spectrum, “No Buck Rogers, No Bucks.” Page 39, June 2014.
  12. NRC report, pg 4-1.
  13. The exception is one or more devices used to remove oxygen from the Martian atmosphere and store it in tanks for use as fuel. As was the case with Apollo, bits and pieces would be scattered across the Martian and Lunar surfaces, but not in the form of ready-to-use infrastructure.
  14. NRC report, page 4-5.
  15. Table 4-4, page 4-63.
  16. NRC report, Section contains a one paragraph discussion of SLS alternatives, notably the Falcon Heavy, rejecting both these alternatives and the conclusions of the Augustine report. Oddly, Section “Heavy-Lift Launch Vehicles” contains a somewhat more favorable treatment of the Falcon Heavy. It concludes “…the crossover point at which an SLS-based approach would be more economical than an approach using smaller launch vehicles has yet to be determined.” This second section appears to have been written by a different person than the first and to be part of a report that might have reached different conclusions.
  17. NRC report, Figure 4.29, page 4-50.
  18. NRC report, page 4-74.