https://ntrs.nasa.gov/search.jsp?R=20140013174 2019-08-31T16:39:30+00:00Z Human Outer Solar System Exploration via Q-Thruster Technology B. Kent Joosten Harold G. “Sonny” White Associate, MBO Partners, Inc. NASA Johnson Space Center 2383 York Harbour Ct. 2101 NASA Parkway League City, TX 77573 Houston, TX 77058 281-543-7043 281-483-0178 [email protected] [email protected] Abstract— Propulsion technology development efforts at the NASA Johnson Space Center continue to advance the under- standing of the quantum vacuum plasma thruster (Q- 1. INTRODUCTION Thruster), a form of electric propulsion. Through the use of electric and magnetic fields, a Q-thruster pushes quantum Q-Thruster Overview particles (electrons/positrons) in one direction, while the Q- thruster recoils to conserve momentum. This principle is It is not the intent here to detail the theory or engineering of similar to how a submarine uses its propeller to push water in quantum vacuum plasma thrusters (Q-Thrusters). Rather, an one direction, while the submarine recoils to conserve momen- overview of the foundational physics and laboratory find- tum. Based on laboratory results, it appears that continuous ings are given. specific thrust levels of 0.4 - 4.0 N/kWe are achievable with essentially no onboard propellant consumption. Q-Thrusters attempt to use the properties of the “quantum vacuum” to propel a spacecraft. Quantum Electrodynamics To evaluate the potential of this technology, a mission analysis (QED) predicts that the quantum vacuum (the lowest state tool was developed utilizing the Generalized Reduced Gradient of the electromagnetic field) is not empty, but rather a sea of non-linear parameter optimization engine contained in the virtual particles and photons that pop into and out of exist- Microsoft Excel® platform. This tool allowed very rapid assessments of “Q-Ship” minimum time transfers from earth ence stemming from the Heisenberg uncertainty principle. to the outer planets and back utilizing parametric variations in A number of approaches to utilize this quantum vacuum to thrust acceleration while enforcing constraints on planetary transfer momentum from a spacecraft to the vacuum have phase angles and minimum heliocentric distances. A conserva- been synopsized in [1]. tive Q-Thruster specific thrust assumption (0.4 N/kWe) combined with “moderate” levels of space nuclear power (1 - 2 A Q-Thruster uses the same principles as conventional MWe) and vehicle specific mass (45 - 55 kg/kWe) results in plasma thrusters, namely magnetohydrodynamics, where continuous milli-g thrust acceleration, opening up realms of plasma is exposed to crossed electric and magnetic fields human spaceflight performance completely unattainable by which induce a drift of the entire plasma in a direction any current systems or near-term proposed technologies. orthogonal to the applied fields. The difference arises in Minimum flight times to Mars are predicted to be as low as 75 that a Q-Thruster uses quantum vacuum fluctuations as the days, but perhaps more importantly new “retro-phase” and “gravity-augmented” trajectory shaping techniques were “propellant” source, eliminating the need for conventional revealed which overcome adverse planetary phasing and allow on-board propellant. A discussion of spacecraft “conserva- virtually unrestricted departure and return opportunities. tion of energy” is given in Appendix A. Recent laboratory Even more impressively, the Jovian and Saturnian systems test results [2] indicate the expected thrust-to-power ratio would be opened up to human exploration with round-trip for flight applications could be in the 0.4 – 4.0 N/kWe times of 21 and 32 months respectively including 6 to 12 range, which is one to two orders of magnitude greater than months of exploration at the destinations. Finally, interstellar current operational electric thrusters. This combination of trip times are assessed at milli-g acceleration levels. characteristics – relatively high specific thrust combined with essentially zero on-board propellant requirement - TABLE OF CONTENTS suggest space mission performance levels significantly 1. INTRODUCTION ................................................. 1 exceeding current capabilities. 2. Q-THRUSTER SYSTEM BEHAVIOR ................... 2 Mission Analysis Approach 3. MARS MISSIONS ................................................ 4 The following analyses are intended to investigate the 4. EXTREME PERFORMANCE MISSIONS ............... 7 potential of Q-Thruster performance in the context of 5. SUMMARY ......................................................... 9 human exploration of the outer solar system. A parametric REFERENCES ......................................................... 9 understanding of the interplay of thruster, vehicle and BIOGRAPHY .......................................................... 9 mission characteristics is first developed followed by APPENDIX A ........................................................ 11 specific instantiations of round-trip missions to Mars, Jupiter and Saturn along with investigations of several APPENDIX B ........................................................ 12 unique mission capabilities. Finally, a brief discussion of APPENDIX C ........................................................ 13 interstellar mission performance is offered. 978-1-4799-1622-1/14/$31.00 ©2014 IEEE 1 4 � − � 2. Q-THRUSTER SYSTEM BEHAVIOR !"#$%! !"#$! (1) �! = , �! To evaluate the potential of Q-Thrusters in the human ! exploration of the outer solar system, an understanding of ! ! ⊙ − ⊙ (2) generalized system behavior is in order. The unique Q- !!"#$! !!"#$%! � = , Thruster characteristics described above imply a nearly ! � constant-mass spacecraft with thrust level varying linearly ! with thruster power input. While required power levels and �! = �! + �! . system specific masses are some of the desired findings !!!"#$ ! ! (3) from the following analyses, it is clear that for outer planet Here, � and � are the heliocentric orbital radii of missions, especially those beyond Mars, reasonable power !"#$! !"#$%! levels can only be maintained with nuclear systems. Since the earth and the target planets respectively, and �⊙ is the the output power of such systems can be held constant sun’s gravitational parameter. The �! term is immediately (independent of heliocentric distance) the spacecraft will recognizable as the “field-free” constant acceleration experience essentially constant thrust acceleration. magnitude required to traverse the radial distance between the planets’ orbits in time �! assuming zero radial velocity at Excellent continuous-thrust mission analysis tools exist, each end and a reversal of acceleration direction at the however many of these require specialized operator exper- midpoint. Similarly, �! is simply the field-free constant tise and exhibit levels of fidelity unnecessary for rapid tangential acceleration needed to match the target planet’s assessment of a broad range of mission and vehicle parame- orbital velocity over the same time interval. There is no ters. For this high-level analysis, a closed-form analytical tangential position constraint since this problem was defined solution exists for the minimum time, phase independent as phase independent. It is a fairly trivial exercise to prove orbit-to-orbit heliocentric transfer of a constant thrust- that these rectilinear solutions satisfy the optimality condi- acceleration spacecraft. To evaluate more complex mis- tions and terminal state constraints. Their validity to the sions with additional constraints, a computational tool was “true” dynamics is based on the observation that �! main- constructed utilizing the programmability and optimization tains the spacecraft in a gravitational “pseudo-equilibrium” capabilities of Microsoft Excel®. Results from this analyti- such that radial gravitational accelerations can be ignored. cal solution and numerical tool were compared with classic Even so, upon evaluation �! contributes less that 1% to the test cases and with a sophisticated NASA production magnitude of �!!!"#$ for all outer planet missions and thrust trajectory optimizer. acceleration levels of interest, so can therefore be neglected. This allows the minimum flight time for a given constant Heliocentric Analytical Solution thrust acceleration level to be expressed as Prior to the availability of computationally rapid numerical trajectory integration and calculus of variation analysis �!"#$%! − �!"#$! tools, various techniques were investigated to analytically � = 2 . !"# � (4) approximate optimal continuous thrust trajectories [3], [4]. !!!"#$ One somewhat successful method [5] sought to identify The validity of the analytic solution will be demonstrated characteristic distances or velocity changes which, when subsequently. used in rectilinear motion equations satisfying the specific problem’s optimality conditions (usually minimum propel- Heliocentric Vehicle and Mission Parameterization lant usage with specified terminal position and velocity constraints) gave reasonable approximations to the propel- For a Q-Thruster propelled nuclear-powered spacecraft the lant usage and flight times obtained from the more rigorous sole parameter affecting the vehicle dynamics is the (con- tools. These analytical solutions could become quite cum- stant) thrust acceleration level and the associated steering bersome however, since traditional propulsion systems policy. The thrust level is determined by the Q-Thruster provide varying