Breakthrough Propulsion Study: Assessing Interstellar Flight Challenges and Prospects

Author: Marc Millis, MS, Propulsion Physicist, NASA, retired

Abstract Background: An assessment of interstellar propulsion concepts is proceeding in 3 stages: (1) assessment methods tailored to interstellar ambitions [Done, HQ-E-DAA-TN60290], (2) relevant information on proposed solutions collected, and (3) comparisons run. Assessment challenges:

• Prior concepts proposed using different missions and assumptions.
• Divergent propulsion measures cannot be directly compared (e.g. specific impulse versus beam divergence).
• Most performance predictions not yet experimentally verified.
• Readiness levels vary significantly.
• Required infrastructure is unplanned.
• Development times are comparable to historic technological revolutions.
• The next decisions are about choosing research, instead of selecting a mission and its technology.
• There are differing motives and priorities from which to infer relative merit.

Abstract Objectives: Identify which propulsion concepts might be the most advantageous and under what circumstances. Identify which research paths have the greatest leverage for increasing NASA’s ability to travel farther, faster, and with more capability.

Abstract Methods: Assess concepts using common mission scenarios and calculate performance in common terms. Develop defensible figures of merit. Use analyses consistent with predictions uncertainty. Use historic patterns to model technological progress.

Abstract Results: To begin stage 2, creating a database of comparison-enabling information, the following will be presented:

• Work breakdown structure for organizing information.
• Basic analysis flow diagram and analysis methods.
• Top 10 list of technology challenges.
• Baseline mission scenarios.
• Methods to distill performance measures to energy, time, and mass.
• Infrastructure modeled as proportional to spacecraft mass and propulsive energy.
• Technology progression modeled using successive S-curves.
• Figures of merit: mission value, energy required, time required, and efficiency.

Abstract Conclusions: This study is not about picking the next interstellar mission and its technology, but rather to identify the most impactive suite of research to get to that point. Information needed for stage 2:

• Concepts performance tailored to analysis questions.
• Scaling information to apply concepts to differing missions.
• Consistent specs for ancillary technologies (e.g. radiators, magnets, power storage).
• Research plans to validate and advance concepts (next research task, plus conceptual plans thereafter).
• History of performance gains and readiness levels.
• Upper physics limits of concepts performance.