COMMENTARY: Constellation Capabilities and Science

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If NASA’s current plans for the Constellation program continue according to schedule, by the 2020s the United States will have space capabilities that have not existed since the 1960s, including a human spacecraft capable of traveling beyond low Earth orbit and a heavy-lift rocket capable of placing very large payloads into space. In late 2007 NASA asked the National Research Council (NRC) to consider what this might mean for science in the 2020-2035 time period. The Committee on Science Opportunities Enabled by NASA’s Constellation System, which we chaired, has recently produced its interim report on this subject and will be delivering its final report by the end of the year.

Our committee was requested to produce an interim report quickly. The time span allocated for our work (four months) included the NRC’s extensive external review process to ensure the report’s integrity. As a result, the scope of our early study was limited to evaluating 11 Vision Mission studies sponsored by NASA in 2005. Approximately half of those studies were for new astronomical observatories; three concerned solar system exploration missions to Titan, Mars and Neptune; one involved sending a spacecraft over the poles of the sun at 0.5 astronomical units (AU); and another was for an interstellar probe that would travel 200 AU from the sun, reaching interstellar space.

The committee was asked to evaluate whether or not these missions initially sized for Evolved Expendable Launch Vehicle (EELV)-class boosters would be further enabled by the capabilities of the Constellation system. We concluded that some would be and others would not. For instance, the Advanced Compton Telescope would fit on existing rockets and does not require any of Constellation’s capabilities. In contrast, a Neptune Orbiter with Probes could use the capabilities of the Ares 5 to enable it to propulsively brake into orbit instead of using an EELV and undeveloped aerocapture technology.

All of these studies are impressive, and the missions would, if pursued, have scientific worth. But some of the missions would easily fit on existing launch vehicles and would still achieve impressive scientific results. Some of them also parallel studies under way in Europe and Japan and might be good prospects for international collaboration. More importantly, all of these proposed missions must be evaluated in the context of the NRC’s decadal surveys, which is where the different scientific communities in astronomy and astrophysics, heliophysics, Earth sciences and solar system exploration establish their priorities.

Our committee’s report, which is available via the Space Studies Board Web site (http://www7.nationalacademies.org/ssb/), states that the committee determined that those science missions that could be lofted by an Ares 5 will be expensive. The cost of space science missions is directly related to both their size and their complexity. Missions designed to use the Ares 5 will be larger and more complex than those currently flying or planned, and mission designers have a difficult time reducing complexity when they can expand their mass budgets and their ambitions. Considering that NASA’s near-term projected science budget is essentially flat, it is easy to imagine that bigger missions could highly stress the science budget, resulting in an imbalance of the scientific program and the potential cancellation or curtailment of a host of smaller projects.

It does not require an Ares 5 to stress the budget, however. All of these Vision Missions, which were originally baselined on the EELV family, would be expensive. The least expensive mission probably costs around a billion dollars in today’s dollars, but we estimated that most are in the $1 billion to $5 billion range, possibly higher. NASA and the scientific community naturally will proceed with caution when considering whether or not to pursue them.

Our committee has issued a request for information asking the scientific community to propose other mission concepts that could benefit from Constellation. We now are receiving inputs. We will be evaluating these at our upcoming meeting in June and summarizing our findings in our final report. Much can be done with the Constellation system that was previously very difficult, if not unthinkable – human missions to asteroids, astronomical observatories with very large apertures, very complex robotic missions to the outer planets and their moons, or networks of instruments placed on planetary bodies as well as on our Moon. But we have no illusions that these projects will be inexpensive, and no one else should either. If you think big, you need a big wallet – and patience – as our study aims at ideas to be implemented in the 2020-2035 time span.

George Paulikas is the former executive vice president of The Aerospace Corp. Kathryn Thornton is a professor at the University of Virginia and a former astronaut who flew on three shuttle missions, including a Hubble servicing mission. They are respectively the chair and vice chair of the NRC’s Committee on Science Opportunities Enabled by NASA’s Constellation System