Thursday, June 18, 2009

Constellation: Launching Science, or Leeching Science? Part 2: Constellation and Technology Development

In Part 1: Science Enabled by Heavy Lift, I covered the analysis in the NRC's Launching Science: Science Opportunities Provided by NASA's Constellation System of a variety of large robotic space science missions, and how they would be enabled or enhanced by the Ares V heavy lift launcher. The authors clearly appreciate many improvements that could be made to major space science missions with heavy lift, but they also show great concern not only with the cost of the heavy lift vehicle itself, but also with the tendency for very large space science missions to become even more expensive than expected. Although quite skeptical that it would actually happen, they hope that much of the mass enabled by heavy lift would be used not to overload the missions with bristling arrays of science instruments and other capabilities, but rather to lower mission costs by avoiding efforts such as technology development. This part of the series will investigate that concept: using heavy lift to avoid technology development.

Assessing the value of lowering science mission costs by avoiding technology development clearly has to be done on a case by case basis. Many factors come into play. What is the cost of the heavy lift vehicle, in terms of development and operations? What is the cost of the specific technology development? Can this cost be accurately estimated before the technology is developed? How much mission cost does the technology, if developed, save? Is the technology applicable to one special science mission, or is it relevant to many science missions, or perhaps even other missions, both commercial and government?

The report cites examples where Ares V capabilities can replace a new technology altogether for some missions:

"For Generation-X, the Ares V would eliminate the need for multiple launches, complex packaging, and on-orbit assembly."

A number of questions arise. From a policy standpoint, do we want to eliminate the need for multiple launches, if those launches are done by vehicles that already exist and are under-used? Would multiple launches be beneficial from the standpoint of sharing fixed launcher costs with other missions - missions that perhaps are critical to national security, the commercial space economy, or monitoring the Earth's environment? Likewise, do we want to avoid on-orbit assembly, or is this a capability that is in the national interest to develop more fully? In essence, is the science mission to be evaluated simply on its science merits, or by other considerations as well? Finally, strictly from a science mission benefit perspective, how does the cost savings of avoiding multiple launches, complex packaging, and on-orbit assembly compare to the cost of using Ares V?

"The reliance on technologies such as aerocapture, nuclear electric propulsion, solar electric propulsion, or solar sails can potentially be eliminated from missions such as the Solar Polar Imager, Interstellar Probe, Titan Explorer, and Neptune Orbiter with Probes."

Do we really want to avoid developing technologies like aerocapture, nuclear electric propulsion, solar electric propulsion, or solar sails? These technologies can be applicable to many missions. Can we support a technology development effort, and perhaps a technology demonstration effort like the recently cancelled New Millenium program, so the first science mission in line for a technology doesn't have to pay for it? If we back up a second, we might ask ourselves which technology we want to develop: heavy lift, or technologies like aerocapture, solar sails, and others? What will the technology development cost? Will developing solar sails and aerocapture cost as much as heavy lift? Once developed, will solar sails and aerocapture cost as much as heavy lift to operate, or will these technologies tend to decrease operations costs (or increase science capabilities for a given dollar amount)? Similar thoughts seem to have crossed the minds of the committee members:

"... the committee noted that several technologies were required for multiple mission concepts and were essentially “mission enabling,” meaning that the mission could not be accomplished without them. These include propulsion technologies that might allow an alternative to the use of a heavy-lift launch vehicle such as the Ares V and are applicable to multiple missions (for example, aerocapture, which can be used at Venus, Mars, Titan, and Neptune; and solar sails, which can be used for the Solar Polar Imager and Interstellar Probe missions). If NASA develops these technologies, an Ares V launch vehicle might not be required for these missions but might enhance them."

Of course given the choice, the committee will take the technology development AND the heavy lift! It's not clear that they'd choose heavy lift if they had to choose between the 2, though.

Note that even the massive Ares V heavy lift capability is not necessarily enough to allow science missions to avoid technology development. From the report:

"Of the mission concepts that the committee considered, the Interstellar Probe, Neptune Orbiter with Probes, Solar Polar Imager, and Titan Explorer could all directly benefit from some form of in-space propulsion technology even if the Ares V is available."

The committee notes that NASA technology development isn't what it used to be. I'm sure the members realize where those technology development dollars went:

"In the recent past, NASA undertook a number of impressive in-space propulsion technology development projects that reached moderate to high technology readiness levels and demonstrated significant promise for future missions. However, for various reasons the agency has eliminated much of this research. The committee concluded that at least some of these technologies will be required for future missions even if they use the capabilities of the Constellation System.

Finding: Advanced in-space propulsion technology may be required for some science missions considered for using the Constellation System."

But how can we afford advanced propulsion system development when we need to fund Ares 1, Ares V, Orion, and so on?

Advance propulsion isn't the only technology that isn't being developed:

"The committee requested and received information from NASA about the planned course of evolution of the Deep Space Network. It learned that by 2025 the DSN may not reliably meet the current and projected uplink and downlink requirements. These current and projected requirements do not include any of the Constellation-enabled missions reviewed during this study, which nominally would fly in the 2020-2035 time interval. NASA is concerned with the deterioration of the existing infrastructure, particularly the 70-m antennas now more than 40 years old, and the lack of overall investment to modernize the DSN to accommodate the expected increase in data rates from a variety of missions, including missions to the Moon and Mars. Absent such modernization, the data return from the Constellation-enabled missions might be compromised and fail to fulfill the potential of these very expensive missions.

Finding: Science missions enabled by the Constellation System will increase the strain on the capabilities of the Deep Space Network."

The whole theory of using Ares V to enable highly-capable science missions is starting to sound worse and worse. The launcher will be expensive, the missions will be expensive, advanced propulsion has been dropped, and we won't have appropriate DSN capabilities for such missions. One gets the impression that we should be working on advanced propulsion and other technologies, as well as the DSN, before considering heavy lift. In fact, the original Vision for Space Exploration was intended to invest heavily in advanced technologies of many kinds.

In the case studies I'm covering, the committee was concerned with ambitious robotic science missions, but one has to wonder how such technology development (advanced propulsion, advanced communication, aerocapture) and operations (multiple launchers, space assembly) could also be used in astronaut exploration missions?

1 comment:

Gaetano Marano said...

now and in the next weeks, you'll find dozens good and rational suggestions for the Human Space Flight Plans Committee in my new ghostNASA article: