NIAC Phase I Awards for Advanced Propulsion

The NASA Innovative Advanced Concepts (NIAC) program recently awarded 25 grants for the development of visionary new technologies. Here we’re going to take a closer look at three Phase I awards focused on advanced propulsion.

PROCSIMA: Diffractionless Beamed Propulsion for Breakthrough Interstellar Missions
Chris Limbach
Texas A&M Engineering Experiment Station

Advanced Diffractive MetaFilm Sailcraft
Grover Swartzlander
Rochester Institute of Technology

Radioisotope Positron Propulsion
Ryan Weed
Positron Dynamics

Each award is worth up to $125,000 for a nine-month study. Descriptions of the awards are below.

Graphic depiction of PROCSIMA: Diffractionless Beamed Propulsion for Breakthrough Interstellar Missions (Credits: C. Limbach)

PROCSIMA: Diffractionless Beamed Propulsion for Breakthrough Interstellar Missions

Chris Limbach
Texas A&M Engineering Experiment Station

We propose a new and innovative beamed propulsion architecture that enables an interstellar mission to Proxima Centauri with a 42-year cruise duration at 10% the speed of light. This architecture dramatically increases the distance over which the spacecraft is accelerated (compared with laser propulsion) while simultaneously reducing the beam size at the transmitter and probe from 10s of kilometers to less than 10 meters.

These advantages translate into increased velocity change (delta-V) and payload mass compared with laser propulsion alone. While primarily geared toward interstellar missions, our propulsion architecture also enables rapid travel to destinations such as Oort cloud objects and the solar gravitational lens at 500 AU.

The key innovation of our propulsion concept is the application of a combined neutral particle beam and laser beam in such a way that neither spreads or diffracts as the beam propagates. The elimination of both diffraction and thermal spreading is achieved by tailoring the mutual interaction of the laser and particle beams so that (1) refractive index variations produced by the particle beam generate a waveguide effect (thereby eliminating laser diffraction) and (2) the particle beam is trapped in regions of high electric field strength near the center of the laser beam.

By exploiting these phenomena simultaneously, we can produce a combined beam that propagates with a constant spatial profile, also known as a soliton. We have thus named the proposed architecture PROCSIMA: Photon-paRticle Optically Coupled Soliton Interstellar Mission Accelerator. Compared with a diffracting laser beam, the PROCSIMA architecture increases the probe acceleration distance by a factor of ~10,000, enabling a payload capability of 1 kg for the 42-year mission to Proxima Centauri.

The PROCSIMA architecture leverages recent technological advancements in both high-energy laser systems and high-energy neutral particle beams. The former has been investigated extensively by Lubin in the context of conventional laser propulsion, and we assume a similar 50 GW high-energy laser capability for PROCSIMA.

Neutral beam technology is also under development, primarily by the nuclear fusion community, for diagnostics and heating of magnetically confined fusion plasmas. By combining known physics with emerging laser and neutral beam technologies, the PROCSIMA architecture creates a breakthrough payload capability for relativistic interstellar missions.

Graphic depiction of Advanced Diffractive MetaFilm Sailcraft. (Credit: G. Swartzlander)

Advanced Diffractive MetaFilm Sailcraft

Grover Swartzlander
Rochester Institute of Technology

The abundant untapped momentum of solar photons is becoming increasingly attractive as a means to propel spacecraft with an attached solar sail. Decades of theoretical mission studies have examined how microscopically thin films ranging from meters to kilometers in extent may make use of freely available sunlight for near-Earth, interplanetary, and interstellar space travel.

In nearly all cases a reflective metal-coated film was the presumed mechanism for photon-to-sail momentum transfer. Here we describe an attractive and innovative alternative that makes use of the recently matured design and fabrication of meta-materials: Diffractive Sails.

Advances in the design and fabrication of broadband high-efficiency single diffraction order gratings and active electro-optic control schemes may make diffractive sails superior to reflective sails for orbit raising or lowering, station keeping, and other mission types.

The proposed new aerospace architecture could, for example, provide a low cost and efficient means for raising hundreds of LEO CubeSats and other satellites to higher orbits. Such satellites are becoming of great US importance for science, security, and commercial purposes. Experiments, numerical modeling, and roadmap development are proposed.

The project will explore the superior radiation pressure force combined with a significant reduction in atmospheric drag in LEO for a diffractive sail compared to a reflective one. The potential to raise (as well as de-orbit or station keep) hundreds of CubeSats from low-cost very-low Earth orbit would be a recognized game changer that would build enthusiasm and advocacy amongst the growing small satellite community of students, entrepreneurs, and aerospace scientists and engineers. Diffractive films provide an innovative approach that will widely affect future solar and laser driven sailing. This proposal represents the first step toward those innovations, raising the TRL from 1 to 3.

Graphic depiction of Radioisotope Positron Propulsion concept. (Credits: R. Weed)

Radioisotope Positron Propulsion

Ryan Weed
Positron Dynamics

Current state of the art in-space propulsion systems based on chemical or ion propellants fail to meet requirements of 21st century space missions. Antimatter is a candidate mechanism for a propulsion system that could transport humans and/or robotic systems with drastically reduced transit times, providing quicker scientific results, increasing the payload mass to allow more capable instruments and larger crews, and reducing the overall mission cost.

Unfortunately, previous propulsion concepts relied on unrealistic amounts of trapped antimatter – orders of magnitude away from any near-term capability. The goal of this effort is to determine the feasibility of a (TRL 1-2) radioisotope positron catalyzed fusion propulsion concept that does not rely on trapped antimatter.

Such a transformative technology inspires and drives further innovation within the aerospace community and can be applied to a relevant mission – the bulk retrieval of an entire asteroid into translunar space – a mission of great scientific and commercial interest (e.g. asteroid mining). The idea of harnessing resources from asteroids goes back more than a century to Tsiolkovsky.

Fundamentally, for asteroid mining to become financially viable, the cost of the retrieval spacecraft must be less than the value gained from the asteroid. Therefore, developing technology (e.g. efficient propulsion systems) that decreases the mass and complexity of the retrieval spacecraft must be a priority.