IRG 2021 Abstracts

A Gravitational Wave Transmitter

Author: Gregory Benford, Department of Physics & Astronomy, UC Irvine

Description: We consider how an advanced civilization might build a radiator to send gravitational waves signals by using small black holes. Micro black holes on the scale of centimeters but with masses of asteroids to planets are
manipulated with a super advanced instrumentality, possibly with very large electromagnetic fields. The machine envisioned emits gravitational waves in the GHz frequency range. If the source to receiver distance is a characteristic length in the galaxy, up to 10000 light years, the masses involved are at least planetary in magnitude. To provide the energy for this system we posit a very advanced civilization that has a Kerr black hole at its disposal and can extract energy by way of super-radiance. Back ground gravitational radiation sets a limit on the dimensionless amplitude that can be measured at interstellar distance using a LIGO like detector.

Is ET Lurking in Our Cosmic Backyard?

Author: James Benford, President of Microwave Sciences

Description: I argue that a strategy of exploring for alien artifacts near Earth is a credible alternate approach relative to the existing listening-to-stars SETI strategy. Stars come very close to our solar system frequently. About two stars per million years come within a light year. An extraterrestrial civilization that passes nearby can see there is an ecosystem here, due to the out-of-equilibrium atmosphere. They could send interstellar probes to investigate. I estimate how many probes could have come here from passing stars. And where could we find them now? The Moon and the Earth Trojans have the greatest probability of success. Close inspection of bodies in these regions, which may hold primordial remnants of our early solar system, yields concrete astronomical research. I suggest additional resources devoted to imaging of our Moon’s surface, the Earth Trojans and Earth co-orbitals, and for probe missions to the latter two. The Search for Extraterrestrial Artifacts (SETA) concept can be falsified: if we investigate these near-Earth objects and don’t find artifacts, the concept is disproven for this nearby region. I construct a ratio of a Drake Equation for alien artifacts to the conventional Drake Equation, so that most terms cancel out. This ratio is a good way to debate the efficacy of SETI vs. SETA. The ratio is the product of two terms: One is the ratio of the time Lurkers could be present in the solar system to the length of time extraterrestrial (ET) civilizations transmit electromagnetic signals. The second term is the ratio of the respective ‘origin volumes’: the volume from which Lurkers can come (which is affected by the long-term passage of stars nearby) to the volume of transmitting civilizations. This Drake Equation logic argues for emphasis on artifact searches, a strategy of ET archaeology.

Orbital Architectures of Nearby Planetary Systems

Author: Jeremy Dietrich, PhD student at the University of Arizona’s Steward Observatory

Background: Exoplanet systems display a large variety in their architectures, from single planets to tightly packed compact multiple systems, from sub-Earth-sized planets to planets larger than Jupiter. Our knowledge of how to form these variations in planetary frameworks is still improving, but we are able to now infer general properties at a population level.

Objective: Here, we will review the orbital architectures of the planetary systems within 15 parsecs. Methods: We will provide statistical interpretations of their parameters and discuss the most likely and most unlikely system characteristics. We can then perform an analysis of the system to predict the likelihood of additional “hidden” planets in these systems

Results:  We will further fill out our interpretation of exoplanet systems in the solar neighborhood, narrowing down orbital configurations and planet parameters.

Conclusions: In the future, this could enable us to determine the most likely system to contain an Earth-like planet when the known architecture seems to be incomplete. Our knowledge of orbital architectures can help provide targets for interstellar probe missions and potential human interstellar travel.

Reconnecting Plasmoid Propulsion

Author: Fatima Ebrahimi

Description: A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The magnetic reconnection process here converts magnetic energy of the applied fields to kinetic energy of the plasmoids, accelerating them to a velocity of tens to hundreds of km/s, adjustable by varying the magnetic fields strength. Our novel electromagnetic thruster concept, the Alfvenic reconnecting plasmoid thruster has been shown to produce an exhaust velocity in the range of 20 to 500 km/s controlled by the coil currents in our first sets of three-dimensional simulations. The plasmoids carry large momentum, leading to a thruster design capable of producing thrusts from tenths to tens of newtons. The optimal parameter range for this new thruster is expected to be ISP (specific impulse) from 2,000 to 50,000 s, power from 0.1 to 10 MW and thrust from 1 to 100 N. It would thus occupy a complementary part of parameter space with little overlap with existing thrusters, and be suitable for long-distance travel with high Delta-v, including the solar system beyond the Moon and Mars. Because the Alfvenic plasmoid thruster can use a wide range of gases as fuel, it will be ideal for asteroid mining, since, for example, hydrogen could be extracted from asteroids. The next steps include performing more detailed computer simulations to both develop a reduced size (50 kW or less) solar-powered thruster version, more suitable for lab testing and with more near-term commercial viability, as well as a larger (tens of MW) fission-powered version.

Cryopreservation of Organisms in Space in Preparation for Interstellar Travel

Authors: Alvaro Diaz Flores, Claire Pedersen, Athip Thirupathi Raj, and Jekan Thangavelautham

Background: The next stages of human exploration towards the outreaches of the solar system and into interstellar space will require traveling vast distances that will inevitably take very long travel times. Taking on such risk in search of new habitable planets is warranted, considering Earth faces several existential threats that can result in mass extinction at any time.  However, such long travel poses challenges, namely the fate of the crew as they age.  Could the crew, over time, fall into conflict, jeopardizing the entire mission? If the journey were to require multiple generations, would later generations have the same motivation or will to proceed? Such a journey will require us not to fail.

Objective: Our objectives are to determine the practical benefit of putting a human crew and living organisms in cryogenic stasis (below -180 ^oC) for long journeys.

Methods: By keeping the crew in stasis and fresh at their destination, we can avoid the organizational challenges described earlier.  This journey will require transporting not just a human crew but an entire support ecosystem.  Keeping an ecosystem in stasis is a smart option that minimizes complexity in operation and could potentially avoid risks of disease or mutational damage spreading during the journey. Yet important questions remain, particularly the effect of micro-gravity and low-gravity conditions. For these reasons, we have set out to better understand cryo-preservation under space and low-gravity. We propose the development of a prototype cryogenic laboratory that would operate on the International Space Station.  The laboratory would be composed of a 12U CubeSat that would be spun at 22 RPM, with the cryo-container located at a distance of 0.3 m from the spinning axis to simulate lunar gravity.  The lab would contain six cryo-bags, two having tardigrades, two containing mice eggs/sperm, and two containing chicken eggs/sperm.  The test will need to be performed for years and repeated with other organisms.

Results and Conclusions: Our work has developed a prototype design model of this facility and determined electrical and thermal needs, and all appear to be feasible. Our next steps are towards the development of a laboratory prototype to advance the component technologies.

Visiting an Exoplanet

Author: Louis Friedman, Executive Director of The Planetary Society, Emeritus

Description: There are two ways to visit an exoplanet — real and virtual.  Real involves going there — something not possible now nor, except with extreme limitations, in the foreseeable future.  Those limitations are with trips times of eons or with a one gram (or so) spacecraft to only the nearest star  powered by a cost and politically prohibitive laser array.   To visit a potentially inhabited exoplanet with extraterrestrial life will require searching over a large number of candidates probably within a distance of 10-50 times the distance to the nearest star, and a spacecraft 2-3 orders of magnitude larger.  The spacecraft will also have to be capable of observing the exoplanet continuously for a while, rather than flying by it at an interstellar speed of (say) 1.5 AU/hour. But, fortunately, nature comes to the rescue – enabling virtual visits to exoplanets by remote observation using the solar gravity lens and positioning a spacecraft and its telescope along its focal line, beginning at 547 AU from the Sun.  That is still a very tall order — but it can be done with today’s technology with a smallsat-solar sail combination and a trip time of 20-30 years.   Such a mission has been under study for several years and is now the subject of a NASA Innovative Advanced Concepts Phase III study including the development of a technology demonstration mission to prove the smallsat-sail concept for high-speed exit of the solar system.  The mission requires technology development — including lightweight electric micro-thrusters with a small RTG or nuclear battery, and multiple small spacecraft to enable a 1-2 meter optical telescope to operate in the solar gravity lens focal region.  The resulting kilometer scale high-resolution of the exoplanet will enable seeing continents, large features, and even (should such exist) large scale evidence of life, as well as incredibly detailed spectral and compositional analysis of the atmosphere.  No other scheme exists for such high-resolution observations, and it is possible even many tens of light-years from our Sun.  It may be the only way to see life on another world.

Wind-Pellet Shear Sailing

Author: Jeffrey Greason, B.S., Chairman, Tau Zero Foundation

Background: Gaining the kinetic energy required for interstellar flight affordably is difficult and tapping existing natural sources of energy such as the solar wind is attractive for reducing costs.  However, a gap exists in the published concepts, in that solar wind speeds are limited to ~700 km/s, while even with concepts such as the wind-powered reaction drive (‘q’-drive), speeds of ~5% of c must be reached before they can take over.  A cost effective way to fill that gap has been lacking. Objective – Demonstrate a method by which inert pellets, accelerated by the solar wind, can be used to accelerate a spacecraft from solar wind speeds up to ~5% of c.

Methods: Classical physics computations to support the basic physics and feasibility of the approach.

Results: When two matter streams are in proximity but with different velocities, or when they move through the same space but with different velocities and distinguishable properties, the difference in velocities, or velocity shear, can be used to gain propulsive energy.   A stream of pellets moving through the interstellar medium is an example of such a case.   Propulsion by pellets is an idea explored in the prior art that requires high speed pellets; the extraction of useful work from the difference in speed between the pellets and the interstellar medium allows a ship running over the pellets and also drawing energy from the passage through the interstellar medium to gain propulsive energy even when faster than the pellets and even when the pellets are composed of inert reaction mass.  We will discuss the basic physics of this and the performance equations and discuss this in the context of using relatively slow pellets (accelerated by solar wind), to send a spacecraft to a substantial multiple over the solar wind velocity.   Another case where small macroparticles and a plasma wind are at different speeds is the inner solar system in the plane of the ecliptic, where the solar wind and zodiacal dust have different velocity distributions; this may offer further applications of the same principle.

Dynamic Soaring as a Means to Exceed the Solar Wind Speed

Author: Andrew Higgins, PhD, Aeronautics and Astronautics, Professor, McGill University

Background: A number of concepts exist for exploiting the solar wind as a means of propulsion: the MagSail, the e-sail, and the plasma magnet. All of these concepts work predominately as drag devices and thus are limited to velocities equal to the solar wind (~700 km/s), with only limited ability to generate force transverse to the local direction of the solar wind (i.e., lift). An interesting possibility to be explored is dynamic soaring: Exploiting the difference in wind speed in two different regions of space. Albatrosses and sailplanes are known to use this technique, circling in and out of regions of wind shear. Birch (JBIS, 1989) suggested such a technique could be used via a “MHD Wing” for interstellar travel applications, but did not explore the concept further.

Objective: The potential for dynamic soaring to enable a spacecraft using the dynamic pressure of the solar wind in order to greatly exceed the wind speed will be explored. Analysis of the concepts will be organized around passive (meaning simple wing- or sail-like structures) and active (wherein there is a power and thrust interaction with the solar wind) approaches.

Methods: For passive methods, charged particle interaction with static electromagnetic fields will be directly numerically simulated and the lift and drag values derived. Techniques of generating electromagnetic fields capable of providing ideally (specular) reflection of particles will be assessed. For active methods, the ability to extract power from the wind and accelerate a transverse flow—thus generating lift—will be analyzed. Simple analytic models of the fast/slow solar wind and the termination shock will be adopted to explore the required trajectories for soaring.  3-degree-of-freedom simulations of spacecraft trajectories will be performed to assess the potential gains that might be realized by the dynamic soaring maneuver.

Results: While passive methods appear capable of generating high lift-to-drag ratio, the requisite structural mass limits them to very low accelerations and thus not directly applicable to interstellar flight. Active concepts wherein plasma structures have a power and momentum transfer interaction with the solar wind are more promising, but have greater uncertainty associated with their principles of operation.

Pulsed Plasma Rocket- Developing a Dynamic Fission Process for High Specific Impulse and High Thrust Propulsion

Author: Troy Howe, PhD, CEO, Howe Industries

Background: To realistically establish a human presence on Mars or to enable faster transit on any deep-space mission, high specific impulse and high thrust are key. Having each of these would allow for efficient propulsion and fast transit, eliminating restrictive launch windows and risks of long-term radiation exposure to crewed missions. The Pulsed Plasma Rocket (PPR) aims to meet these needs via a fissioning propulsion system that produces rapid plasma bursts. Previous efforts have examined pulsed propulsion methods, including the use of plasma as propellant, but the PPR achieves these plasma bursts via a fission-based system, wherein a highly moderated fuel projectile is propelled through a uranium barrel to reach supercriticality. The barrel and projectile material architecture results in much higher energy deposition in the projectile than in the barrel. After experiencing significant fission events, the projectile changes from a solid to a plasma over a period of a few microseconds, and is expelled through a magnetic nozzle. 

Methods: Performed for a Phase I NASA NIAC study to determine feasibility and performance.  Computational modeling has been performed using MCNP, MOOSE, and SERPENT neutronics programs. Thermal systems analyzed using COMSOL Multiphysics. Plasma interactions modeled with SPFMax. 

Results: Neutronics modeling has determined the projectile constituents to include a high-assay low enriched uranium water-ice mix encased in a thin iron shell. Control drums generate a pulse of extreme supercriticality by rotating at different rates to create a Fourier series delta function which flashes the projectile into an ionized plasma at the end of the barrel. With the combined use of a coilgun as the initial propellant injector and a magnetic coil and nozzle for exhaust, the projectile is able to produce a thrust of roughly 100 kN with an Isp of 5,000s. 

Conclusions: The necessary criticality to reach plasma-generating temperatures can be achieved in the projectile, while maintaining overall system integrity. The ship is capable of a 2-month transit to Mars, consumes no highly enriched uranium material, and can power itself by recuperating energy from the propulsion system.

Deceleration of Interstellar Spacecraft Utilizing Antimatter

Author: Gerald Jackson, Ph.D. Physics, Co-Founder and President, Hbar Technologies, LLC

Description: This paper summarizes the results from a recently completed NASA Innovative Advanced Concepts (“NIAC”) Phase I grant. The grant explored a mission architecture wherein a 10kg-scale unmanned spacecraft decelerates and inserts itself into orbit around an exoplanet.  In this research the antimatter-initiated fission of depleted uranium produces electrical power, thrust, or both to accomplish these maneuvers and enable robust scientific discovery and two-way communications with Earth.  A mission to the nearby habitable-zone exoplanet Proxima b is explored as a concrete example, wherein the acceleration stage of the spacecraft is separated after its 10-year burn and deflected to perform a fly-by through the Alpha Centauri AB binary system.  Similar to the Voyager 2 mission, wherein a grand tour of the outer planets justified the spacecraft investment that is still yielding scientific results decades later beyond the heliopause, a program of prompt science results regarding interstellar clouds, Oort cloud population distributions, interstellar magnetic fields, and radiation spectra in the interstellar void are envisioned.  As one example, an exciting conclusion is that the detection of 10km-scale Oort cloud objects by a small semi-relativistic spacecraft is indeed feasible.  During this grant, several potential methods of deceleration were investigated, starting with the emission of electrostatically-focused  fission daughters as reaction mass, each having an average exhaust velocity of 4.6% of the speed of light.  The other methods involve dissipating the large kinetic energy of the spacecraft into the interstellar medium, using a variety of possible coupling mechanisms.  A significant impediment to progress along these lines is the lack of data concerning plasma composition and density of the interstellar medium and the directions and intensities of the interstellar magnetic field.  The allure of these other methods is the possibility that their consumption of scarce antimatter, in this case used to generate onboard electrical power, might be smaller than the primary reaction mass method.  This paper will also briefly summarize other results in the areas of antimatter production and storage, spacecraft instrumentation, and other mission objectives.

Bussard’s Fusion Ramjet: the Impossible Dream

Author: Geoffrey A. Landis

Description: “To dream the impossible dream… to reach the unreachable star…” — Joe Darion In 1960, physicist Robert Bussard proposed that the main problem of interstellar flight, the high mass ratio required for most propulsion systems, could be avoided if the fuel is not carried on the rocket, but instead fuel (and reaction mass) could be scooped up from the interstellar medium along the flight path of the vehicle, using a hypothetical electromagnetic scoop to gather hydrogen as fuel for a fusion reaction. Although Bussard’s original proposal was lacking in solutions to practical difficulties, the idea of an interstellar vehicle that did not carry fuel, and hence was capable of true relativistic velocities, caught the attention of the interstellar community, as well as science fiction writers. This system is not likely to be practical for a number of reasons, including the fact that the interstellar medium contains too low a density of material to be useful; the interstellar material is primarily hydrogen atoms, which cannot be used as the feedstock of any proposed fusion reactor or any hypothetical future fusion reactors based on known physics; and the fact that proposed scoop designs create more drag from the interstellar medium than the thrust produced by the interstellar hydrogen. Other investigators have proposed that that the collected material is not harvested as the energy source, but could be used as reaction mass; this concept is known as the “ram-augmented interstellar rocket.”  However, the difficulties of the low density of the interstellar remain. These problems can be alleviated if, instead of using the ambient interstellar medium, fuel is deliberately emplaced in the path of the spacecraft before the flight. Kare proposed that, at the velocities proposed for interstellar flight, nuclear fusion can be accomplished at the temperatures produced by impact, and proposed a propulsion system he tagged the “Bussard Buzz-bomb”. Analysis shows, however, that Kare’s initial concept is only plausible if the pellets can be pre-compressed before impact, a process which would have great difficulty to implement.  A more detailed variant of the impact-fusion runway will be presented, and the major difficulties to this approach discussed.

Phenomenology and Capabilities of Mutually Guided Laser and Neutral Particle Beams for Deep Space Propulsion

Author: Chris Limbach, Ph.D.

Background: By circumventing the rocket equation, particle and laser beams provide attractive mechanisms for accelerating spacecraft to relativistic velocities for interstellar flight. In both approaches the beam divergence and momentum coupling play a central role in architecture optimization and propulsion capabilities. The possibility of combining both approaches, entailing an overlap of co-propagating laser and particle beams, provides an opportunity to tailor an interaction between the optical field and atoms which allows self-guiding through the space environment. 

Objective: The working principle of self-guiding and potential for long-range guided propagation will be explored. In particular, this work addresses the stability of the overlapped beams and progress toward laboratory studies. 

Methods: Self-channeling in vacuum arises from the interplay of refractive modulation of the laser wavefront and optical dipole forces influencing the motion of the atoms. Analyses of the paraxial wave equation and collisionless Boltzmann equation are applied toward obtaining self-consistent spatial soliton solutions. The application of a Landau stability analysis to the coupled equations is then used to understand the dynamical evolution. These analytical approaches are subsequently connected with laboratory methods with the goal of reproducing key phenomenology in ground-based experiments. Relevant experimental methods include TDLAS for characterization of the atomic beam and ultra-high vacuum technologies for simulating the space environment. 

Results: Axisymmetric soliton solutions are obtained for a range of atomic beam mass flow-rates and laser power, with two non-dimensional parameters governing the soliton spatial profiles. These parameters correspond to 1) the strength of refraction versus diffraction, and 2) the strength of the optical dipole force relative to thermal motion of the atoms. Together, they also play a key role in the dynamics, determining the strength of the feedback loop that amplifies or dampens perturbations in the beam profile. It will be shown that a newly discovered phenomenon analogous to Landau damping results in the decay of high wavenumber (small-scale) perturbations that can serve to stabilize long-range propagation. Using modern experimental methods for generating cold, supersonic atomic beams, we show that this phenomenon should be observable in laboratory experiments.

Communications challenges for the exploration of nearby star systems with low mass probes

Author: Philip Mauskopf, PhD Physics, Professor, Arizona State University

Description: Typically, in the field of interstellar exploration most attention is paid to propulsion schemes, but developing the technology to send information back to Earth from a nearby star is a no less daunting undertaking. For the Breakthrough Starshot system – relying as it does on ultra-low-mass probes to approach near-relativistic speeds – this task is all the more challenging. In this paper, we describe the figures of merit and requirements for such a communication system and compare them to the current state-of-the-art in planetary missions such as NASA’s New Horizons spacecraft and the upcoming Psyche mission – which will include NASA’s first deep space optical communications system demonstration. We also identify areas in which we see potential for improvements and investments in deep space communications. Finally, we will introduce and describe a new dedicated research effort in this area by the Breakthrough Initiatives, focused on meeting the size, mass, power and cost requirements of the Starshot system.

The Interstellar Communication Relay (What If SETI Succeeds, Now What?)

Author: Brian McConnell

Description: SETI organizations are rightly focused on the task of detecting artificial radio or optical signals from other solar systems, but what if they succeed in detecting an information bearing signal? While the initial detection effort is the domain of a small community of subject experts, the process of analyzing and comprehending the information extracted from a signal will involve a diverse and global community of scientists, including citizen scientists. In this talk, we discuss the information infrastructure that should be in place to support these efforts, the different user communities it would support, as well as the risks and challenges associated with distributing information extracted from an ET transmission. This system, which we can call the Interstellar Communication Relay, can be built using low cost and highly scalable cloud computing and source code management systems, and can be designed to be highly resilient.

Using New Physics to get to Alpha Centauri in a Human Lifetime

Author: Mike McCulloch

Background: According to standard physics we cannot travel to the stars in a human lifetime because we need impractical amounts of fuel to get close to light speed. However, a new theory of inertia has been proposed called Quantised Inertia (QI). It predicts standard inertia, as a vacuum effect, at normal accelerations. It also predicts a drop in inertia at low accelerations that predicts disc galaxy rotation without dark matter. Therefore it has solid empirical backing.

Objective: Quantised inertia predicts that a new kind of propulsion can be achieved by energising the vacuum and making gradients in it using synthetic ‘horizons’ (conductive materials). This form of propulsion does not need heavy fuel, only an energy source, so it would allow interstellar travel in a human lifetime. The objective is to demonstrate this prediction unambiguously in the lab.

Method: $1.3M was won from DARPA to test this prediction and a network of, so far, six labs have joined the effort, formerly and informally. The methods used include firing lasers into asymmetric metal cavities, lasers into fibre-optic loops shielded by metal on one side, high-acceleration electrons in capacitors, and other methods.

Results: So far, one experiment has shown no thrust but several others have measured the thrust expected from the theory, with force to power ratios of for example 0.08 N/kW (comparable to ion drives, without needing fuel) and up to 100 N/kW (enough to enable launch).

Conclusion: If these positive results can be replicated and confirmed then interstellar travel within a human lifetime becomes possible. This talk will present the quantised inertia theory, the evidence for it, the experimental thruster results so far (where possible) and an outline of a QI-based interstellar propulsion system (horizon drive).

Mass and propulsion implications for interstellar scientific observation by flyby

Author: David G Messerschmitt, Roger Strauch Professor Emeritus, Electrical Engineering and Computer Sciences, University of California at Berkeley

Description: In view of the vast distances to an interstellar target, the highest technologically achievable spacecraft speed is often assumed, thus minimizing the mass of the scientific payload and communication gear. This is generally a compelling assumption for human spaceflight,  where many considerations favor short time to target. These include biological constraints such as the lifetime of astronauts, life support and physiological needs, and even psychological well being and onboard culture. However, for the coming century interstellar missions are expected to be robotic and employ flyby observation (as opposed to landing) to avoid deceleration. We address missions in which a space probe performs a target flyby during scientific observations, with data conveyed back to earth by electromagnetic radiation. In this scenario the scientifically relevant metrics are the observation time, the total volume of data returned, the number or frequency of probe flybys, and the total data latency (time elapsed from probe launch until completion of data return). The four components of data latency are travel time to target, observation time at target, the subsequent data transmission time, and the signal propagation delay. The mission design should be optimized with respect to objective functions like maximizing data volume for a given latency or, when a swarm of probes is launched, launch cost per unit of data volume. While  reducing probe speed (increasing payload mass) does increase the travel time to target, for directed-energy propulsion with a fixed launch infrastructure the dependence is a weak quarter-power penalty. Offsetting this is an expected mass-squared increase in data rate, a longer scientific observation time, a moderation of the distance-squared decrease in data rate, and a smaller signal propagation delay at the end of transmission. Several examples of design optimization under appropriate criteria illustrate the benefits of substantially increased probe mass with a resultant lower speed. The scaling law governing the relationship of probe mass and transmission data rate is observed to be a significant issue in interstellar probe design.

Breakthrough Propulsion Study – Assessing Interstellar Challenges and Prospects

Authors: Marc Millis and James Gilland

Objective: A database of interstellar propulsion options is being created. The database aims to capture a span of concepts in the peer-reviewed literature and cover the evaluation factors devised in the 1st stage. The focus is on identifying which research paths have the most leverage for traveling farther, faster, and with more capability, rather than being a system to select pick an interstellar mission and its technology. The assessments will allow for varying assumptions and priorities. Though NASA is the sponsor, the results will be publicly accessible.

Methods: To collect information, three database sets are planned, the first of which is underway; (1) Mission-Vehicle Concepts, (2) Propulsion and Power System Performance, (3) Research Plans and Roadmaps. In the process of collecting information, “dashboards” for accessing the information are being developed, including a publicly accessible version.

Results: In March, 2021, an online questionnaire began collecting information for Mission-Vehicle concepts. By June, 2021, the following concepts were submitted: • Pulsed Fission Fusion Hybrid (PUFF) [Cassibry] • Firefly Icarus [Freeland] • Q-Drive to Alpha Centauri [Greason] • Project Hyperion [Hein] • Icarus Interstellar [Lamontagne] • Deep In, Starlight, Starship [Lubin] • Graphene Solar Photon Sail [Matloff] • Project Daedalus [Millis] • Forward’s Starwisp [Millis] • Forward’s Rendezvous Laser Sail to Alpha Centauri [Millis] • Forward’s Round-Trip Interstellar Sail [Millis] • Solar Sail with Thermal Desorption [Starinova]

Conclusions: Techniques have been devised to equitably compare the disparate and unproven propulsion options, and in a way to accommodate the uncertainties. Collecting data has begun, but not all of the needed information is available. Examples include predictions on infrastructure growth, technology readiness rates, and having consistent performance specs for ancillary technologies (e.g. thermal radiators, magnetic nozzles, power storage). Developing user-interfaces for the database is a work in progress, adjusting to the submissions received.

Extrasolar Object Intercept and Sample Return Mission Using Ultra Power Dense Radioisotope Electric Propulsion

Author: Christopher Morrison

Background:  In the past three years, we have detected the first two known interstellar objects passing through our solar system: Oumuamua in 2017 and C/2019 Q4 (Borisov)in 2019. Both interstellar objects contain a wealth of undiscovered information about what the universe is like outside our solar system. Being able to visit, take a sample from these extrasolar objects, and return them to Earth for study has the potential to fundamentally change our view of the universe and its evolution. This study is the subject of an ongoing Phase I NIAC. 

Objective: Intercepting and returning from an extrasolar object requires an extremely high ∆V on the order of 100 km/s. Currently chemical propulsion cannot feasibly achieve a Δ𝑉 exceeding 20. Electric propulsion can achieve Δ𝑉on the order of 100 km/s but requires a power source that can operate at vast distances from the sun and with a low mass.  

 Methods: USNC-Tech is proposing a power source technology called a Chargeable Atomic Battery (CAB). The key innovation is a novel manufacturing process for radioisotope power systems that unlocks the ability to produce high performing non-traditional radioisotope materials that can be produced cheaply and quickly compared to traditional Pu-238 radioisotope systems. The CAB batteries are manufactured using natural non-radioactive feedstock material and then be activated or “charged” inside of a fission reactor to the desired power. They can then be packaged without the need for chemistry or separation. 

Results: When combined with other state-of-the-art and near-term technologies, this architecture can achieve this ambitious mission. The proposed technology is a radioisotope electric power system capable of achieving a specific mass of 5-10kg/kWe. The CAB sources scale well to low mass and a 1-metric ton wet mass vehicle which can be delivered using a single ground launch vehicle. The spacecraft would be capable of delivering a 50 kg payload with a 100 km/s Δ𝑉 over a 5-to-10-year timeline. 

Conclusions: Radioisotope electric propulsion combined with CAB technology can enable sample return missions from extra solar objects.

FarView – An In-Situ Manufactured Lunar Far Side Radio Observatory

Authors: Ronald S. Polidan, Jack Burns, Alex Ignatiev, Javier Lopez Jr., and Elliot Carol

Description: We will discuss interim results from a NIAC funded concept study of FarView: a low frequency (5‑40 MHz) radio observatory that will be built on the lunar farside using almost exclusively lunar regolith materials. FarView will be a sparse array of ~100,000 dipole antennas populating a ~10×10 km area on the lunar far side.  Building FarView on the lunar far side is required to shield it from Earth’s anthropogenic and natural radio noise that would severely limit its performance.  The innovative technology elements enabling FarView will be the near exclusive use of in situ resources and on-site manufacturing of almost all system elements for the radio observatory, including dipole antennas, wiring, power generation and energy storage systems. FarView science is focused upon investigation in exquisite detail of the unexplored Cosmic Dark Ages using the highly redshifted hydrogen 21-cm line and identifying the conditions and processes under which the first stars, galaxies, and accreting black holes formed.  This radio telescope will be the first of its kind at this scale and sensitivity and will open a new window (low frequency radio) into the early universe.  FarView will be continuously serviceable and evolvable using in situ manufacturing with occasional system upgrades from Earth.  It will be lower cost and have a longer lifetime than a complete antenna array launched from Earth. The key enabling technology is the molten regolith electrolysis (MRE) facility developed by Lunar Resources.  This revolutionary technology is a high-temperature electrolytic process in which the naturally high-oxide lunar regolith is liquefied by electric current to produce metals and oxygen.  By landing ~300 kg of “tools” we can extract ~7 MT of metals and ~10 MT of oxygen per year. FarView’s development of lunar surface infrastructure (power and energy storage systems, in-space manufacturing assets, space mining assets) will enable future lunar surface scientific and commercial missions.  The demonstration of the extraction and refinement of oxygen and metallics and the utilization of these materials to manufacture functional components will enable future lunar outposts and advance human spaceflight activities on the surface of the Moon and Mars.

On moving faster than light

Author: Gabriele Rizzo, PhD

Description: Achieving faster-than-light (FTL) travel, akin to sci-fi “warp speed,” has long been one of the dreams of the astrophysical community. However, a number of issues plague this achievement since Alcubierre’s warp drive metric in 1994, among them the need for negative energy to obtain the desired spacetime geometry and the creation of horizons around the payload. Challenges associated with the creation of horizons also include the invasion by Hawking radiation of the inside space and the stress-energy buildup on the leading horizon. Recently, an article by Lentz in Classical and Quantum Gravity offers a novel construction to avoid resorting to negative energy, moving the warp drive problem from an existential, fundamental point to an engineering issue. By overcoming the negative energy problem, it then make sense to revisit some literature about FTL astronavigation, and investigating the use of warp bubbles also for subluminal travel and not just for superluminal speed.

In this talk we will take a cross cutting view of some of the latest evolutions (Lentz 2020; Bobrick & Martire 2020) as well as some literature made relevant again (Clark, Hiscock & Larson 1999; Alcubierre & Lobo, 2017) to take stock of the progresses in warp drive spacetimes and discuss their consequences in engineering and astronavigation.

Synthetic biology as the enabling technology for NASA’s missions

Author: Lynn Rothschild

Description: Synthetic biology – the design and construction of new biological parts and systems and the redesign of existing ones for useful purposes – is transforming fields from fuels to pharmaceuticals and beyond.  Our lab has pioneered the potential of synthetic biology to revolutionize two areas of interest to NASA: astrobiology and as an enabling tool for exploration.  Synthetic biology is allowing us to answer whether the evolutionary narrative that has played out on planet Earth is likely to have been unique or universal.  For example, can we create organisms that expand the envelope for life, for example, radiation resistance?  For exploration, we will rely increasingly on biologically-provided life support, as we have throughout our evolutionary history. But once life itself is seen as an enabling technology, we can do so much more. What about the exploration platforms themselves? Using fungi to build structures off planet? Using peptides to recycle metals from integrated circuits and provide the raw materials to build new structures in space? Building materials? Using DNA as a scaffold to create wires a atom or two in thickness? Producing pharmaceuticals and other small molecules in small quantities, on demand? Finally, Will this technology work in space? The PowerCell payload on the DLR EuCROPIS mission is designed to do just that.  Activated in December 2018, early results will be presented.

The Solar Shield Concept: Current Status and Future Possibilities

Author: Kenneth Roy

Description: The idea of using solar radiation management technologies to mitigate Earth’s global warming problem is not new.  The idea of positioning solar shades at the Sun-Earth L1 point is not new.  However, a number of concerns relative to this approach have been raised by various sources.  This paper will review past proposals, address the varied concerns raised to date,  examine new technologies that make this approach more viable, and outline one possible deployment scenario that could begin within the next decade. The magnitude of the task will be defined based on assumed target reductions in the Earth’s global temperature. New technologies for using solar sails for this purpose are derived primarily from NASA’s proposed Solar Cruiser (a mission powered by a 1.6 km2 solar sail) scheduled to be launched in 2025. One possible deployment scenario is discussed assuming the availability of private, reusable, heavy launch vehicles with greatly reduced costs compared to today’s launch capability. This approach can reduce Earth’s temperature rise but cannot address other environmental problems such as ocean acidification due to higher levels of CO2 in the atmosphere.  It can buy time to allow carbon neutral energy sources to be developed and deployed.  It will also result in a robust space launch capability that can then be used to facilitate space industrialization and the utilization of the massive material and energy resources available in space for the benefit of all humanity and indeed, all life on planet Earth.

SAM: Construction of a hi-fidelity, hermetically sealed Mars habitat analog at Biosphere 2.

Author: Kai Staats, project lead, SAM at Biosphere 2

Description: A Space Analog for the Moon and Mars (SAM) is a hi-fidelity, hermetically sealed analog and research center composed of a living quarters for four inhabitants, airlock and hub, and greenhouse with temperature, humidity, and carbon dioxide level controls. When complete, SAM will include a half-acre Mars yard for pressure suit, tool use, and rover tests; a constructed lava tube and gravity-assist rig for reduced gravity simulations.

In 1987 Taber MacCallum and William Dempster designed and build the now iconic Test Module, a sealed greenhouse prototype used to test the fundamental functions of the structure and lung used to build the massive Biosphere 2. Now, project lead Kai Staats, Trent Tresch, John Adams and a compliment of volunteers are constructing SAM with intent to welcome the first research teams in the fall of 2021.

SAM design and development is guided by experts at NASA Johnson Space Center, Grant Anderson, CEO of Paragon SDC; Dr. Murat Kacira and Dr. Gene Giacomelli at the Controlled Environment Agriculture Center at the University of Arizona, and original Biospherian Taber MacCallum.

In this presentation Trent will engage the audience in the construction process, lessons learned, and the long-term goals of this unique research facility as it relates to sealed habitats of any volume or duration, and how SAM will inform the computer model SIMOC with a long-term goal of management of on-board life support systems.

Objective: To build a habitat analog and research station that welcomes research teams from around the world, to help prepare our species to become interplanetary.

Methods: Grinder, sander, scraper, primer and paint; electrical wiring, lighting, HVAC. CO2 scrubber, pressure seals, monitors and regulators, pressure suits and EVAs.

Results and Conclusions: To be determined!

An Overview and Plan for an Interstellar Mission Study with the novel Helicity Drive fusion propulsion concept

Author: Alan Stern, Ph.D., Astrophysics and Planetary Science, Univ. Colorado-Boulder

Background: Helicity Space is a startup based in California developing an in-space fusion propulsion drive.

Objective: In this presentation we will summarize the company’s objectives, team, technology, progress, and plans. We will also outline our planned 2021 NASA Innovative Advanced Concepts (NIAC) proposal to study an interstellar probe traveling to 1000 Astronomical Units (AU) using the Helicity Drive fusion propulsion system.

Methods: The Helicity Drive is a new magneto-inertial fusion concept based on decades of experimental and theoretical fusion plasma research. The concept exploits magnetic reconnection and a new magnetic confinement configuration (plectonemes) to enable scalable propulsion characteristics and simplify fusion engineering.

Results: Our calculations show that the engine concept can operate from small 100 kW engines to 10 Giga-watt engines by increasing the number of plasma sources, similar to the way a car engine increases power with more cylinders. With variable high specific impulses inherent to fusion, our Helicity Drive engines could thus take, for example, a 5-ton probe to 1000 Astronomical Units in about 11 years using medium-sized 37 Megawatt-thrust engines or as little as 3 years using large 5 GW-thrust engines.

Conclusion: The Helicity Drive fusion propulsion system presents a significantly new capability for an interstellar mission concept. The interstellar mission could use larger scientific instruments and be completed substantially earlier and faster, eliminating the need for difficult and expensive design and qualification issues associated with conventional propulsion approaches.

Overview of the NASA Innovative Advanced Concepts Program

Author: Ronald Turner, Distinguished Analyst, Analytic Services (ANSER)

Description: The NASA Innovative Advanced Concepts (NIAC) Program nurtures visionary ideas that could transform future NASA missions with the creation of breakthroughs — radically better or entirely new aerospace concepts — while engaging America’s innovators and entrepreneurs as partners in the journey. NIAC projects study innovative, technically credible, advanced concepts that could one day “Change the Possible” in aerospace. NIAC supports innovative research through two phases of study, both competitively awarded. The Phase I studies are for nine-month efforts to explore the overall viability of visionary concepts. Phase II studies further develop the most promising Phase I concepts for up to two years, and explore potential infusion options within NASA and beyond. Phase III are awarded to a select few Fellows to support those concepts that have a high potential for transition to an immediate sponsor. While NIAC seeks innovators with a passion for changing the possible, it is sometimes difficult for them to frame their concept in a way that is within NIAC’s scope. This presentation will provide a quick look at many of the NIAC studies funded recently and relevant to IRG. It will also touch on what is needed to be competitive in NIAC.

Power Generation from Interplanetary and Interstellar Plasma and Magnetic Fields

Authors: Matt Wentzel-Long and Geoffrey A. Landis

Background: The proposal to send an ultra-lightweight probe to a nearby star by accelerating a sail using a laser array will require miniaturization of the spacecraft by many orders of magnitude compared to existing spacecraft. One difficulty for such a concept is reducing the mass of the power source for the onboard computer and scientific instruments. 

Method: In this work, the possibility of generation of power by the sail’s relativistic motion through the ambient magnetic field is analyzed, in which a voltage is created by the induced electric field of a conductor passing through a magnetic field, and a current is established by electrical contact with the ambient plasma. Approximations are estimated for several magnetic environments: that of the interstellar environment, a solar-type star, and the environment of Proxima Centauri as example destinations. 

Results: The results of this analysis were presented at the AIAA Propulsion and Energy Forum in August of 2020. The results show that to generate a power of 10 mW, a sailcraft with the following cross-sectional areas are needed: 5,000 – 12,000 m² in the interstellar medium, 2,800 – 600,000 m² in a solar-type interplanetary medium, and < 500 m² in the interplanetary medium of Proxima Centauri. 

Conclusions: According to this analysis, power can be generated by the passage of a sail through the interplanetary medium, but this may require sizes that are large compared to some currently proposed sails.

Alpha Centauri: getting there – and what to expect when we do

Author: S. Pete Worden, PhD, Brig. Gen., USAF, Ret., Chairman, Breakthrough Prize Foundation

Description: The Alpha Centauri System is the nearest star system to our own at a little over 4 light years from the Sun. A three-star system, it is comprised of two Sun-like stars, Alpha Centauri A and B, and a distantly orbiting red dwarf, Proxima Centauri – the nearest star to our own. The past decade has been an exciting time for exo-planet astronomy and the Alpha Centauri system is no exception. In 2016 and 2019, two planets were confirmed around Proxima and, earlier this year, astronomers associated with the Breakthrough Watch program identified a candidate planet in the habitable zone of Alpha Centauri A. This paper will detail the latest data we have on the Alpha Centauri system and outline the key remaining questions about our nearest neighbor. In particular it will consider the case for life, or the conditions for life around Alpha Centauri and describe ongoing and future efforts to further characterize the system. Finally, it will provide an update on Breakthrough Starshot and discuss what implications these latest astronomical discoveries might have on the interstellar probe research and development program.