An abundant source of energy in space, electromagnetic radiation can provide spacecraft with a gentle yet persistent thrust for interplanetary and interstellar missions. Early successes with microlaser and solar propulsion platforms confirm their potential for near-Earth and deep space exploration, although practical realization of reliable photonic devices is not trivial. This Perspective outlines the recent achievements and future outlook in the field of photonic space propulsion. We highlight several light-enabled mechanisms of thrust generation via photon–matter interactions such as photonic pressure and ablation, optical gradient forces, light-induced electron emission and others. Finally, we outline some of the key challenges in the area and possible solutions for practical applications. Recent achievements and future opportunities for light as a propulsion scheme for space vehicles is discussed.

Prospects and physical mechanisms for photonic space propulsion

A vacuum test campaign evaluating the impulsive thrust performance of a tapered radio-frequency test article excited in the transverse magnitude 212 mode at 1937 MHz has been completed. The test campaign consisted of a forward thrust phase and reverse thrust phase at less than 8×10−6  torr vacuum with power scans at 40, 60, and 80 W. The test campaign included a null thrust test effort to identify any mundane sources of impulsive thrust; however, none were identified. Thrust data from forward, reverse, and null suggested that the system was consistently performing with a thrust-to-power ratio of 1.2±0.1  mN/kW.

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Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum

http://emdrive.com/iac2014presentation.pdf

Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe

The EMDrive has been proposed as a revolutionary propellantless thruster using a resonating microwave cavity. It is claimed to work on the difference in radiation pressure due to the geometry of its tapered resonance cavity. We attempted to replicate an EM Drive and tested it on both a knife-edge balance as well as on a torsion balance inside a vacuum chamber similar to previous setups in order to investigate possible side-effects by proper thermal and electromagnetic shielding. After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive’s inventor, we built a breadboard out of copper with the possibility to tune the resonance frequency in order to match the resonance frequency of the magnetron which was attached on the side of the cavity. After measuring the Q-factor of our assembly, we connected the EMDrive to a commercial 700 W microwave magnetron. Our measurements reveal thrusts as expected from previous claims (due to a low Q factor of <50, we observed thrusts of +/-20 μN) however also in directions that should produce no thrust. We therefore achieved a null measurement within our resolution which is on the order of the claimed thrusts. The purpose of the test program was to investigate the EMDrive claims using improved apparatus and methods. To this end it was successful in that we identified experimental areas needing additional attention before any firm conclusions concerning the EMDrive claims could be made. Our test campaign therefore can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurement methods used so far. We identified the magnetic interaction of the power feeding lines going to and from the liquid metal contacts as the most important possible side-effect that is not fully characterized yet and which needs to be evaluated in the future in order to improve the resolution.

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Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects

A careful study of plasma-material interactions is essential to understand and improve the operation of devices where plasma contacts a wall. Key contributions of this work include (i) novel continuum kinetic algorithms with novel boundary conditions that directly discretize the Vlasov/Boltzmann equation using the discontinuous Galerkin method, (ii) fundamental studies of a plasma sheath physics with collisions, ionization, and physics-based wall emission, and (iii) theoretical and numerical studies of the linear growth and nonlinear saturation of the kinetic Weibel instability, including its role in plasma sheaths. The continuum kinetic algorithm has been shown to compare well with theoretical predictions of Landau damping of Langmuir waves and the two-stream instability. Benchmarks are also performed using the electromagnetic Weibel instability and excellent agreement is found between theory and simulation. The role of the electric field is significant during nonlinear saturation of the Weibel instability, which was not noted in previous studies. A focus is put on understanding plasma sheath physics which is essential for studying plasma-material interactions. Initial simulations are performed using a collisionless model to match classical sheath theory and the Bohm criterion. A collision operator and volumetric physics-based source terms are introduced and effects of heat flux are briefly discussed. Novel physics-based boundary conditions are developed and included in a general manner with the continuum kinetic algorithm for bounded plasma simulations. These are the first continuum kinetic simulations using self-consistent, wall emission boundary conditions with broad applicability across a variety of regimes.

Continuum Kinetic Simulations of Plasma Sheaths and Instabilities

This paper describes the test campaigns designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster (QVPT), but instead will describe the recent test campaign. In addition, it contains a brief description of the supporting radio frequency (RF) field analysis, lessons learned, and potential applications of the technology to space exploration missions. During the first (Cannae) portion of the campaign, approximately 40 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 935 megahertz and 28 watts. During the subsequent (tapered cavity) portion of the campaign, approximately 91 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 1933 megahertz and 17 watts. Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level. Test campaign results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.

/pdf/anomalous-thrust-production-from-an-rf-test-device-measured-4i2ofvebkh.pdf

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum

NASA is transforming human spaceflight. The Agency is shifting from an exploration-based program with human activities in low Earth orbit (LEO) and targeted robotic missions in deep space to a more sustainable and integrated pioneering approach. However, pioneering space involves daunting technical challenges of transportation, maintaining health, and enabling crew productivity for long durations in remote, hostile, and alien environments. Subject matter experts from NASA's Human Exploration and Operations Mission Directorate (HEOMD) are currently studying a human exploration campaign that involves deployment of assets for planetary exploration. This study, called the Evolvable Mars Campaign (EMC) study, explores options with solar electric propulsion as a central component of the transportation architecture. This particular in-space transportation option often results in long duration transit to destinations. The EMC study is also investigating deployed human rated systems like landers, habitats, rovers, power systems and ISRU system to the surface of Mars, which also will involve long dormant periods when these systems are staged on the surface. In order to enable the EMC architecture, campaign and element design leads along with system and capability development experts from HEOMD's System Maturation Team (SMT) have identified additional capabilities, systems and operation modes that will sustain these systems especially during these dormant phases of the mission. Dormancy is defined by the absence of crew and relative inactivity of the systems. For EMC missions, dormant periods could range from several months to several years. Two aspects of uncrewed dormant operations are considered herein: (1) the vehicle systems that are placed in a dormant state and (2) the autonomous vehicle systems and robotic capabilities that monitor, maintain, and repair the vehicle and systems. This paper describes the mission stages of dormancy operations, phases of dormant operations, and critical system capabilities that are needed for dormant operations. This paper will compare dormancy operations of past robotic missions to identify lessons that can be applied to planned human exploration missions. Finally, this paper will also identify future work and analysis planned to assess system performance metrics and integrated system operations.

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Design Considerations for Spacecraft Operations During Uncrewed Dormant Phases of Human Exploration Missions

Pilot wave theories are a family of realist interpretations of quantum mechanics that conjecture that the statistical nature of the formalism of quantum mechanics is due to an ignorance of an underlying more fundamental real dynamics, and that microscopic particles follow real trajectories over time just like larger classical bodies do. The first pilot wave theory was proposed by de Broglie in 1923 [1] where he proposed that a particle interacted with an accompanying guiding wave field, or pilot wave, and this interaction is responsible for guiding the particle along its trajectory orthogonal to the surfaces of constant phase. In 1952, Bohm [2] published a pilot wave theory where the guiding wave is equivalent to the solution of the Schrödinger equation and a particle's velocity is equivalent to the quantum velocity of probability. A family of models categorized as vacuum-based pilot wave theories or Stochastic Electrodynamics (SED) [3] explore the idea that the zero point field, electromagnetic vacuum fluctuations represent a natural source of stochasticity in the subquantum realm and provides classical explanations for the origin of the Planck constant, Casimir effect, ground state of hydrogen, and much more. While the idea of a pilot wave or realist interpretation of quantum mechanics is not the dominant view of physics today (which favors the Copenhagen Interpretation), it has seen a strong resurgence of interest over the last decade based on some quantum analog experimental work pioneered by Couder and Fort [4]. In addition to these quantum analogs, Bohmian trajectories in an interferometer may have recently been observed in the lab [5]. In the approach used in the Quantum Vacuum Plasma Thruster (Q-thruster) supporting physics models, the Zero Point Field (ZPF) plays the role of the guiding wave in a similar manner to the vacuum based pilot wave theories. To be specific, the vacuum fluctuations (virtual fermions and virtual photons) serve as the dynamic medium that guides a real particle on its way. During this talk, a physics model will be developed in detail and its place in the taxonomy of ideas about the nature of the quantum vacuum will be discussed. The experimental results from the recently completed vacuum test campaign evaluating the impulsive thrust performance of a tapered RF test article excited in the TM212 mode at 1,937 megahertz (MHz) will be summarized. The empirical data from this campaign will then be compared to the predictions from the physics model tools. The talk will conclude with a discussion on the follow-on activities being pursued in the investigation of the conjectured physics models.

James Lawrence

Papers

Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum

Design Considerations for Spacecraft Operations During Uncrewed Dormant Phases of Human Exploration Missions

Pilot Wave Model for Impulsive Thrust from RF Test Device Measured in Vacuum