Mike LaPointe of NASA Headquarters. The authors would like to acknowledge their encouragement and support for this effort.
Additional assistance came from Jim Gilland of the Ohio Aerospace Institute, Paul Gilster of the Tau Zero Foundation, Les Johnson of NASA, and the staff who helped run the 2017 Tennessee Valley Interstellar Workshop.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Aeronautics and Space Administration.
pg 2 of 69

Millis 2018 Grant NNX17AE81G_for_CR.docx TABLE OF CONTENTS LIST

  OF	
  TABLES .....................................................................................................................................5 LIST	
  OF	
  FIGURES....................................................................................................................................5 ACRONYMS ..............................................................................................................................................5
1.	
   EXECUTIVE	
  SUMMARY.................................................................................................................6
1.1. At-­a-­glance	
  highlights	
  in	
  this	
  report..............................................................................................6 1.2. Content	
  by	
  Section ...............................................................................................................................6
2.	
   INTRODUCTION .............................................................................................................................8
2.1. Provocations..........................................................................................................................................8 2.2. Objective	
  and	
  Approach.....................................................................................................................9 2.2.1. Stage	
  I	
  –	
  Defining	
  the	
  Problem	
  as	
  a	
  Work	
  Breakdown	
  Structure	
  (WBS).............................. 10 2.2.2. Stage	
  II	
  –	
  Comprehensive	
  Update	
  to	
  Interstellar	
  Challenges	
  &	
  Prospects	
  WBS ................ 11 2.2.3. Stage	
  III	
  –	
  Remaining	
  Analysis	
  and	
  Recommendations................................................................ 11 2.3. Outside	
  Scope	
  of	
  Study .................................................................................................................... 11
3.	
   PRIMER	
  ON	
  THE	
  DISTINCTIONS	
  OF	
  INTERSTELLAR	
  FLIGHT ......................................12
3.1. Distance................................................................................................................................................ 12 3.2. Timescales........................................................................................................................................... 15 3.3. Energy ................................................................................................................................................... 16 3.4. Infrastructure	
  Dependence ........................................................................................................... 18
4.	
   INTERSTELLAR	
  TECHNOLOGY	
  CHALLENGES	
  (Top-­Down)...........................................19
4.1. Payload	
  Challenges........................................................................................................................... 19 4.2. Propulsion	
  &	
  Power	
  Challenges................................................................................................... 20 4.3. Incremental	
  and	
  Affordable	
  Infrastructure	
  Creation........................................................... 21
5.	
   PROPULSION	
  &	
  POWER	
  PROSPECTS	
  (Bottom-­Up)..........................................................22
5.1. Historical	
  Spacecraft	
  Baselines.................................................................................................... 22 5.2. Proposed	
  Interstellar	
  Mission-­Propulsion	
  Architectures................................................... 23 5.3. Propulsion	
  &	
  Power	
  Concepts ...................................................................................................... 24 5.4. 2017	
  Workshop	
  Review.................................................................................................................. 27
6.	
   PROPOSED	
  WORK	
  BREAKDOWN	
  STRUCTURE	
  (WBS) ...................................................28
6.1. WBS	
  Hierarchical	
  List...................................................................................................................... 28 6.2. Basic	
  Analysis	
  Flow	
  Diagram ........................................................................................................ 29 6.3. List	
  of	
  Variables ................................................................................................................................. 31
7.	
   MEASURING	
  MISSION	
  CHOICES	
  (Top-­Down) ....................................................................33
7.1. Destination.......................................................................................................................................... 33 7.2. Mission	
  Ambition .............................................................................................................................. 33 7.2.1. Arrival	
  Trajectory.......................................................................................................................................... 33 7.2.2. Science	
  Sought................................................................................................................................................ 34 7.3. Timing................................................................................................................................................... 35 7.4. Motive ................................................................................................................................................... 37 7.5. Figures	
  of	
  Merit.................................................................................................................................. 37
8.	
   METHODS	
  FOR	
  EQUITABLE	
  COMPARISONS ......................................................................39
8.1. Distinct	
  Eras	
  of	
  Interstellar	
  Flight............................................................................................... 39 8.1.1. Era	
  of	
  Precursors........................................................................................................................................... 39
Millis 2018 Grant NNX17AE81G_for_CR.docx