Interstellar Travel Research Articles

Photonic materials for interstellar solar sailing

Solar sails are of great promise for space exploration, affording missions that push the limits of the possible. They enable a variety of novel science missions ranging from ultrafast interstellar travel to imaging the poles of the sun—missions that are beyond the reach of current propulsion technology. Here, we describe requirements and challenges associated with optical materials and photonic designs facing the next generation of solar sails. A technology development roadmap is outlined to guide researchers in pioneering the space faring future.

Phase Change and Space Travel

Here we discuss the implications of phase change equations and what bearing they might have on interstellar space travel. The phase change equations are derived from either thermodynamics or statistical mechanics and have a similarity. Then, the main equation for limit of superheat is posited to be a solution to the problem of propulsion in space travel. There are two matter-antimatter systems considered: electron – positron and hydrogen – antihydrogen. What is involved in the space travel problem is harvesting of antimatter in magnetic bottles and keeping it separate.

‘Oumuamua as a light sail: Evidence against artificial origin

‘Oumuamua, the first detected interstellar visitor to the Solar System, exhibits non-gravitational acceleration in its trajectory. In ruling out other means of propulsion, such as the evaporation of material via a cometary tail, it has been argued that radiation pressure is responsible for this acceleration. From this (a = 5 × 10−6 m s−2), the mass of the object must be approximately 4 × 104 kg, and given its dimensions, ‘Oumuamua must have a thickness of ≲1 mm if of a similar rock and iron composition as the Earth. This raises the much publicised possibility that ‘Oumuamua is artificial in origin and intentionally sent across interstellar space by an alien civilisation. This conclusion, however, relies upon the common misapprehension that light (solar) sails can accelerate to a considerable fraction of the speed of light, permitting rapid interstellar travel. We show that such speeds are unattainable for conceptual man-made sails and that, based upon its observed parameters, ‘Oumuamua would require half a billion years just to travel to our Solar System from its closest likely system of origin. These cosmological timescales make it very unlikely that this is a probe sent by an alien civilisation.

Photonic solution to phase sensing and control for light-based interstellar propulsion

Reaching another star system within a human timescale requires traveling at a sizeable fraction of the speed of light. To achieve this, the Breakthrough Starshot program proposes a ground-based laser array to accelerate a gram-scale spacecraft through photon radiation pressure, requiring of order 100 GW of continuous wave optical power. The coherent combination of many lasers is one avenue to achieve a high optical power output. Here we present a photonic solution for optical phase sensing and control to enable the coherent combination of order 10 8 individual lasers, including the ability to sense and compensate for atmospheric distortions, assuming the laser system is ground based.

Minimal Conditions for Survival of Technological Civilizations in the Face of Stellar Evolution

Abstract The ease of interstellar rocket travel is an issue with implications for the long-term fate of our own and other civilizations and for the much-debated number of technological civilizations in the Galaxy. We show that the physical barrier to interstellar travel can be greatly reduced if voyagers are patient, and wait for the close passage of another star. For a representative time of ∼1 Gyr, characteristic of the remaining time that Earth will remain habitable, one anticipates a passage of another star within ∼1500 au. This lowers the travel time for interstellar migration by ∼two orders of magnitude compared with calculated travel times based on distances comparable to average interstellar separations (i.e., ∼1 pc) in the solar vicinity. We consider the implications for how long-lived civilizations may respond to stellar evolution, including the case of stars in wide binaries, and the difficulties of identifying systems currently undergoing a relevant close encounter. Assuming that life originates only around G-type stars, but migrates primarily to lower mass hosts when the original system becomes uninhabitable, the fraction of extant technological civilizations that exist as diaspora can be comparable to the fraction that still orbit their original host stars.

Energy production by laser-induced annihilation in ultradense hydrogen H(0)

Laser-induced nuclear processes in ultra-dense hydrogen H(0) give ejection of bunches of mesons similar to known baryon annihilation processes. This process was recently described as useful for relativistic interstellar travel (Holmlid and Zeiner-Gundersen 2020) and more precise experimental results exist now. The mesons are identified from their known decay time constants at rest as slow charged kaons, slow neutral long-lived kaons and slow charged pions. Other observed time constants are interpreted as relativistically dilated decays for fast mesons of the same three types, with kinetic energy up to 100 MeV for the kaons. Mouns are observed with kinetic energy of >100 MeV as decay products from the mesons. These particle energies are much too high to be due to nuclear fusion in hydrogen, and the only known process which can give such energies is baryon annihilation. A model of the annihilation process starting with two protons or two neutrons gives good agreement with the observed meson types and their masses and kinetic energies, thus now giving the complete energetics of the process. The process works with both D(0) and p(0). The efficiency from mass (of two baryons) to useful energy is 46% (contrary to 0.3% for T + D fusion) and the main non-recoverable energy loss is to neutrinos. Neutrons are not formed or ejected so this is an aneutronic process. The energy which can be extracted from ordinary hydrogen is 11.4 TWh per kg. This annihilation method is well suited for small and medium energy applications in the kW to MW range, but scaling-up to GW power stations requires further development. It is unlikely that this energy production method can be used for weapons since there is no ignition or chain reaction.

Nuclear Processes in Dark Interstellar Matter of H(0) Decrease the Hope of Migrating to Exoplanets

It is still generally assumed that interstellar travel will be possible after purely technical development and thus that mankind can move to some suitable exoplanet when needed. However, recent research indicates this not to be the case, since interstellar space is filled with enough ultradense hydrogen H(0) as stable condensed dark matter (Holmlid, Astrophysical Journal 2018) to make interstellar space travel at the required and technically feasible relativistic velocities (Holmlid et al, Acta Astronautica 2020) almost impossible. H(0) can be observed to exist in space from the so-called extended red emission (ERE) features observed in space. A recent review (Holmlid et al., Physica Scripta 2019) describes the properties of H(0). H(0) gives nuclear processes emitting kaons and other particles, with kinetic energies even above 100 MeV after induction for example by fast particle (spaceship) impact. These high particle energies give radiative temperatures of 12000 K in collisions against a solid surface and will rapidly destroy any spaceship structure moving into the H(0) clouds at relativistic velocity. The importance of preserving our ecosystem is pointed out, since travel to suitable exoplanets may be impossible. The possibilities of instead clearing interstellar space from H(0) are discussed, eventually providing tunnels suitable for relativistic interstellar transport. Finding regions with low intensity of ERE could even be a way to identify space-cleaning activities and thus to locate earlier space-travelling civilizations.

The radioactive nuclei and in the Cosmos and in the solar system

AbstractThe cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies,$^{26}\mathrm{Al}$and$^{60}\mathrm{Fe}$. Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of$^{26}\mathrm{Al}$and$^{60}\mathrm{Fe}$, the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of$\gamma$rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of$^{26}\mathrm{Al}$to$^{60}\mathrm{Fe}$eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.

Guide star catalog generation of star sensors for interstellar navigation

In interstellar travel, parallax and stellar aberration have a non-negligible influence on the star identification of star sensors. Through the analysis of the working principle of star sensors, only the guide star catalog generation can solve this problem. The influence mechanism of parallax and stellar aberration is synthetically analyzed by four-dimensional time-space diagrams, and a generation algorithm of the guide star catalog for the interstellar star identification is presented. The update cycle of the catalog is studied, and a block update method based on the distance distribution is given. The Hipparcos catalog is adopted as the fundamental catalog. On the premise of meeting the accuracy requirement of star identification, the maximum travel distance supported by the catalog is about 0.3 light-years. In order to balance the star identification and the influence of parallax, eliminating 30% to 40% of the nearby guide stars is an optimal criterion for the guide star selection. The analysis of the catalog distribution shows that the parallax and the stellar aberration have opposite effects on the distribution of guide stars. The methods and conclusions provide a theoretical basis for interstellar celestial navigation.

Прямоточный релятивистский двигатель - гипотеза для обсуждения

In this paper, the engineering and scientific community is invited to consider and discuss the possibility of developing and constructing a ramjet engine for movement in the interstellar medium when the speeds of an aircraft are close to the speed of light. The idea is based on existing developments in high energy physics and accelerator technology. For interstellar flight, a motion scheme is proposed using accelerated relativistic high-energy protons to create efficient jet engines based on accelerating superconducting structures. The proposed scheme is based on the existing developments in the field of accelerator technology, using superconducting resonator systems, klystrons and high-frequency generators. The use of the impulse of the relativistic motion of charged particles is proposed as a hypothesis for discussing the design of a direct-flow engine for motion in the interstellar medium.

Sharing Humanity

In science fiction, the construction of alien life forms is usually less concerned with the exploration of the other than with reflections on the human condition and our status in evolving environments. Joan Slonczewski’s Elysium Cycle is no exception to this rule, and its four novels discuss the question, “What does it mean to be human?” in ever new contexts. But instead of the action-driven plots that frequently structure tales of interstellar travel and colonization, we find a focus on negotiations between the different agents and representatives of alternate life forms to avoid escalating conflicts. Within these novels, the outbreak of large-scale violence can ultimately be prevented by compromise, but also by a willingness to recognize the similar in the other, the familiar in the non-human. This paper explores not only these aspects in Slonczewski’s novels, but also her feminist and participatory epistemology as the basis for an alternative practice of science and politics.

Advances in deep space exploration via simulators & deep learning

The NASA Starlight and Breakthrough Starshot programs conceptualize fast interstellar travel via small relativistic spacecraft that are propelled by directed energy. This process is radically different from traditional space travel and trades large and slow spacecraft for small, fast, inexpensive, and fragile ones. The main goal of these wafer satellites is to gather useful images during their deep space journey. We introduce and solve some of the main problems that accompany this concept. First, we need an object detection system that can detect planets that we have never seen before, some containing features that we may not even know exist in the universe. Second, once we have images of exoplanets, we need a way to take these images and rank them by importance. Equipment fails and data rates are slow, thus we need a method to ensure that the most important images to humankind are the ones that are prioritized for data transfer. Finally, the energy on board is minimal and must be conserved and used sparingly. No exoplanet images should be missed, but using energy erroneously would be detrimental. We introduce simulator-based methods that leverage artificial intelligence, mostly in the form of computer vision, in order to solve all three of these issues. Our results confirm that simulators provide an extremely rich training environment that surpasses that of real images, and can be used to train models on features that have yet to be observed by humans. We also show that the immersive and adaptable environment provided by the simulator, combined with deep learning, lets us navigate and save energy in an otherwise implausible way.

Design and analysis of a growable artificial gravity space habitat

The goal of this study is to show the feasibility of designing a space habitat that advances the ability of humans to live in space for long periods. We first review the previous work on space explorations and summarized five unsolved fundamental problems: providing gravity, radiation protection, sustainable life support system, a large open space for human physiological and psychological comfort (survivable by professionals in trades other than highly trained astronauts), and a growth strategy to avoid the economic infeasibility of starting with the largest final version of the habitat. We present a detailed design of a rotating shielded habitat system and a growth strategy by repeated addition of new layers, without disturbing the inhabitants of the current habitat. The tensegrity paradigm is used to design the structure and to optimize the mass and cost of the habitat. Then, a detailed discussion of the structural dynamics and attitude control is given. Based on the human needs of temperature, cosmic radiation protection, atmosphere, clean water, food, physical fitness, and mental health, a life support system is demonstrated to show the livable environment under thermal and energy equilibrium. This habitat, space village one, allows a long-term human presence in space such as space tourism, interstellar travel, space mineral mining, Mars colonization, etc.

Beating the Big Bang – Version 2

In “The Science Show” on Australian Broadcasting Corporation’s “Radio National” (July 4, 2020 - Robyn Williams says “Let's continue this quest into the weird and wonderful with Geraint Lewis's latest book, The Cosmic Revolutionary's Handbook (Or: How to Beat the Big Bang).” Then Professor Lewis says, “What we wanted to lay out in the book that we have is essentially what is the observational evidence that astronomers used to build up the picture of the Big Bang theory, and outline that if you want your theory to supplant the Big Bang theory, you're going to have to explain this observational evidence as well as the Big Bang picture does, if not better, before scientists will take note. Number one fact; the night sky is dark. It's Olbers' paradox, it's one of the nice famous philosophical, scientific ideas. If your scientific theory can't explain that simple fact, you are already in trouble.” This article will address several points in its refutation of the Big Bang – Olbers’ paradox, Edwin Hubble, redshift, blueshift, the cosmic microwave background, gravitational waves, quantum entanglement, the quantizing of E=mc2, the First Law of Thermodynamics, the initially plausible (though, I conclude, ultimately incorrect) multiverse hypothesis, vector-tensor-scalar geometry, dark matter, dark energy, mass, quantum spin, the Higgs boson and Higgs field, bosons of the strong and weak nuclear forces, as well as advanced waves and retarded waves. It concludes with the Mobius strip, figure-8 Klein bottle, Wick rotation, Albert Einstein’s time dilation, and Rene Descartes’ space-matter relation. Following the advice of Dr. Luke Barnes (coauthor of The Cosmic Revolutionary's Handbook), I’ve refined my ideas - by adding about 1,500 words I previously wrote to explain the ideas better. This new section is called 'Interstellar, Intergalactic and Time Travel plus Simply-Connected and Nonorientable Topology' and all additions, such as these extra lines in the abstract and the new paragraph about dark matter and dark energy, are highlighted in yellow.

Future interstellar rockets may use laser-induced annihilation reactions for relativistic drive

Interstellar probes and future interstellar travel will require relativistic rockets. The problem is that such a rocket drive requires that the rocket exhaust velocity from the fuel also is relativistic, since otherwise the rocket thrust is much too small: the total mass of the fuel will be so large that relativistic speeds cannot be reached in a reasonable time and the total mass of the rocket will be extremely large. Until now, no technology was known that would be able to give rocket exhaust at relativistic speed and a high enough momentum for relativistic travel. Here, a useful method for relativistic interstellar propulsion is described for the first time. This method gives exhaust at relativistic speeds and is a factor of at least one hundred better than normal fusion due to its increased energy output from the annihilation-like meson formation processes. It uses ordinary hydrogen as fuel so a return travel is possible after refuelling almost anywhere in space. The central nuclear processes have been studied in around 20 publications, which is considered to be sufficient evidence for the general properties. The nuclear processes give relativistic particles (kaons, pions and muons) by laser-induced annihilation-like processes in ultra-dense hydrogen H(0). The kinetic energy of the mesons is 1300 times larger than the energy of the laser pulse. This method is superior to the laser-sail method by several orders of magnitude and is suitable for large spaceships.

Design considerations for relativistic laser sails*

Physics based methods have been developed to obtain accurate design estimates for the performance of relativistic interstellar laser sails and to identify technologies to mitigate losses inherent in the physics. The physical principles that are applied include those of the Special Relativity and Quantum Mechanics. Special Relativity is especially difficult to apply consistently. A method is summarized which makes the application of the Special Relativity straightforward, reducing the possibility of errors generated by neglecting important effects and by reducing mathematical difficulties. Once launched, the spacecraft design must remain fixed, and this dictates a design for the sail that must be able to respond to a broad range of possible events. Although physics-based losses cannot be eliminated, or even reduced, technologies can be applied at the source to help reduce their effect at the sail. These losses include: 1) the decrease in frequency, and hence energy, due to Doppler effects and 2) decreases in the intensity due to delays in the arrival of the photons. Including relativistic effects amplifies these losses at the velocities necessary for interstellar flight. When the sail reaches one fifth of the speed of light the losses become significant. Some losses can be mitigated while others cannot. For example, free electron lasers can be used to keep the frequency (and hence the energy of the photons) constant at the sail and a phased array can be expanded in area to narrow the beam width. Both can be used keep the momentum transferred constant at the sail. A phased array will also allow the beam direction to be controlled. Mathematical models and results will be presented for Doppler and intensity losses, beam width and direction control. A straightforward method to include effects of relativity has been applied to aid in performance estimates for relativistic interstellar laser sails. Although losses based on the physics remain the same their effects at the sail can be reduced significantly. Phased arrays will help with direction control, beam spreading, and intensity adjustments while free electron lasers can help mitigate Doppler effects. Sail structural dynamics, an important consideration not previously discussed, is introduced and methods to lessen the effects are discussed.

Geodesy on surfaces of revolution: A wormhole application

We outline a general procedure to derive first-order differential equations obeyed by geodesic orbits over two-dimensional (2D) surfaces of revolution immersed or embedded in ordinary three-dimensional (3D) Euclidean space. We illustrate that procedure with an application to a wormhole model introduced by Morris and Thorne (MT), which provides a prototypical case of a “splittable space-time” geometry. We obtain analytical solutions for geodesic orbits expressed in terms of elliptic integrals and functions, which are qualitatively similar to, but even more fundamental than, those that we previously reported for Flamm's paraboloid of Schwarzschild geometry. Two kinds of geodesics correspondingly emerge. Regular geodesics have turning points larger than the “throat” radius. Thus, they remain confined to one half of the MT wormhole. Singular geodesics funnel through the throat and connect both halves of the MT wormhole, perhaps providing a possibility of “rapid inter-stellar travel.” We provide numerical illustrations of both kinds of geodesic orbits on the MT wormhole.

The Solar System: Favored for Space Travel

Here, we compare Earth to the most common type of exoplanet, the super-Earth, with respect to interplanetary space travel. The typical super-Earth should have higher gravity and atmospheric pressure at its surface. These factors pose significant challenges to rocket launches and to reentering spacecraft. In addition, the Solar System is compared to exoplanetary systems with respect to interstellar travel. It is easier to launch an interstellar spacecraft from a planet in the circumstellar habitable zone of the Sun than from planets in the circumstellar habitable zones of less massive stars. In the larger context of the Milky Way galaxy, our Solar System is in the best location to initiate interstellar missions. In summary, we here confirm and expand upon recent studies that argue that the Earth and the Solar System are rare in the degree to which they facilitate space exploration.

Solar One: A Proposal for The First Crewed Interstellar Spacecraft

In this paper it is presented the concept and design of a new type of spacecraft that could be used to make the first manned interstellar travel. Solar one would integrate three near-term technologies, namely: compact nuclear fusion reactors, extremely large light sails, and high-energy laser arrays. A system of lenses or mirrors to propel the sail with sunlight is suggested as an alternative to laser propulsion. With a mile-long light sail, Solar One could reach an average of 22% the speed of light, arriving to the closest potentially habitable exoplanet in less than 19 years with the help of a Bussard scoop producing reverse electromagnetic propulsion. Key challenges are reducing the weight of continuous-wave lasers and compact fusion reactors as well as achieving cryo-sleep and artificial gravity.

Electric sails are potentially more effective than light sails near most stars

Electric sails are propulsion systems that generate momentum via the deflection of stellar wind particles through electric forces. Here, we investigate the relative merits of electric sails and light sails driven by stellar radiation pressure for F-, G-, K- and M-type stellar systems. We show that electric sails originating near M-dwarfs could attain terminal speeds of ~500 km/s for minimal payload masses. In contrast, light sails are typically rendered ineffective for late-type M-dwarfs because the radiation pressure is not sufficiently high to overcome the gravitational acceleration. Our analysis indicates that electric sails are better propulsion systems for interplanetary travel than light sails in proximity to most stars. We also delineate a method by which repeated encounters with stars might cumulatively boost the speeds of light sails to ≳0.1c, thereby making them more suitable for interstellar travel. This strategy can be effectuated by reaching ~105 stars over the span of ~10 Myr.