TABLE 2-1 NASA’s SERT Program—Model System Category Definitions

NASA Model System Category

Power Capability

Flight Test Demonstration Options (to be chosen competitively)

Projected Time Frame


~100 kW

Free flyer

LEO-to-Earth power beaming research platform

Solar power plug in space

Cryogenic propellant depot

“Mega-commsat” demonstrator


MSC 1.5

~1 MW

GEO-to-Earth solar power satellite (SPS) demonstrator

Lunar exploration SPS platform

Earth neighborhood transportation system



~10 MW

Free flyer

GEO-based SPS demonstration platforms for wireless power transmission, solar power generation, power management and distribution, and solar electric propulsion

Interplanetary transportation system



~1 GW

Commercial space full-scale solar power satellite



SOURCE: Adapted in part from Mankins and Howell, 2000a.

to validate technology advancement. However, the committee also realizes, as does NASA, that the schedule of milestones and roadmap should be reconfigured as research and development for components of the program are realized (or not realized) and new results are obtained. NASA demonstrated during the course of the study that the roadmaps were revamped several times during the first 2 years of the program in response to both internal agency assessments and external peer review. Continued annual and biannual assessment of the roadmaps, schedules, and goals are an inherent part of the program. The committee recommends that future roadmaps, however, contain more transparent information tying together cost, performance, and schedule. The roadmaps should also more visibly demonstrate their reliance on advances in space transportation and robotics that are entirely or largely funded by other programs.

NASA’s SERT program presented a concept for reviewing its time-phased plans, which include the incorporation of NASA’s strategic plans and goals, information gleaned from independent program and technology assessments, new innovative technology applications, government and commercial application opportunities, and research efforts in other organizations. This iterative process review would be cycled at least annually because strategic research and technology investments must be selected each fiscal year as part of the NASA budget development process (assuming the work becomes part of the overall NASA program).

The committee has also seen evidence that the current SERT program’s roadmaps do not adequately incorporate the planned advances of low-cost space transportation development, both Earth-to-low-Earth-orbit (LEO) and in-space options. Because any advancements in space transportation are key to the SSP program’s ultimate success, the timing and achievement of technology advances and cost and mass goals by the separate space transportation programs within NASA should be included directly in the SSP roadmaps. A periodic revamping of the roadmaps should be made based on the achievements of NASA in space transportation. SSP program technology investments, flight test demonstrations, and full-scale deployment should be rescheduled accordingly. Adequate contingency plans also need to be developed to be able to react positively to the failure of any flight or ground test demonstration planned by the program.

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