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Light sail-based propulsion systems are a candidate technology for interplanetary and interstellar missions due to their flexibility and the fact that no fuel has to be carried along. In 2014, the Initiative for Interstellar Studies (i4is) hosted the Project Dragonfly Design Competition, which aimed at assessing the feasibility of sending an interstellar probe propelled by a laser-powered light sail to another star system. We analyzed and designed a mission to the Alpha Centauri system, with the objective to carry out science operations at the destination. Based on a comprehensive evaluation of currently available technologies and possible locations, we selected a lunar architecture for the laser system. It combines the advantages of surface- and space-based systems, as it requires no station keeping and suffers no atmospheric losses. We chose a graphene-based sandwich material for the light sail because of its low density. Deceleration of the spacecraft sufficient for science operations at the target system is achieved using both magnetic and electric sails. Applying these assumptions in a simulation leads to the conclusion that 250 kg of scientific payload can be sent to Alpha Centauri within the Project Dragonfly Design Competition's constraints of 100 year travel duration and 100 GW laser beam power. This is only sufficient to fulfill parts of the identified scientific objectives, and therefore renders the usefulness of such a mission questionable. A better sail material or higher laser power would improve the acceleration behavior, an increase in the mission time would allow for larger spacecraft masses.

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 $\sim 500$ 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 $\gtrsim 0.1\,c$, thereby making them more suitable for interstellar travel. This strategy can be effectuated by reaching $\sim 10^5$ stars over the span of $\sim 10$ Myr., Published in Acta Astronautica; 20 pages; 4 figures

Herein we consider the cost of getting to space and contemplate the value of sending people there. Thereafter we examine other propulsion systems—things that are still rockets but are certainly not chemical rocket motors . Some of those are already in everyday use, some will exist one day and some probably never will but are still areas of active study because they just might take us to the stars. We’ll look at what might be required for interstellar travel before considering a propulsion concept that could possibly achieve it, albeit without rockets. Finally we will indulge ourselves with a quick stroll through a few flights of fancy pertaining to the wilder fringes of space travel after rockets.

[CASTELLÀ] El objetivo principal del trabajo es elaborar una propuesta de misión espacial para explorar el cinturón de Kuiper, una región del sistema solar situada a 30-55 ua del sol. Para la exploración se plantea el uso de una sonda capaz de llegar e investigar el cinturón. Este trabajo hace un estudio del estado del arte actual y se analizan cuatro temas distintos: el primero es el cinturón de Kuiper y las condiciones a las que nos enfrentamos en el espacio exterior. En segundo lugar, los sistemas de instrumentación de la sonda, donde se habla y se mencionan sistemas existentes y que han sido usados por otras sondas espaciales a lo largo de la historia. De esta manera, se propone un equipo de instrumentación preparado para el estudio de los cuerpos que constituyen el cinturón de Kuiper (objetos transneptunianos, cometas, planetoides). Los tipos de propulsores que puede llegar a equipar, haciendo una comparación y análisis de cada uno de ellos. Por último, se hace un estudio de la mecánica orbital para el cálculo aproximado de la trayectoria de la sonda. Se propone como punto de partida la órbita de la estación espacial internacional (ISS) y, con los cambios orbitales adecuados, la llegada a Júpiter, donde se analiza cómo llegar hasta Kuiper mediante asistencia gravitatoria y sin usarla. Se debe tener en cuenta que el diseño de una misión espacial es una tarea que requiere años y muchas personas especializadas en la materia. Por lo tanto, lo que recoge este trabajo es un humilde acercamiento al tema de viajes interplanetarios con sondas espaciales, teniendo en cuenta las limitaciones de tiempo y recursos para resolver los problemas que surjan durante el desarrollo del proyecto. [ANGLÈS] The main objective of this project is to elaborate a proposal of a space mission that aims to explore the Kuiper Belt. A payload that is able to properly investigate the Kuiper belt is presented for this exploration. This Project studies the recent state of the art and analyses four different aspects: In first place, the Kuiper belt and the conditions to be faced in the outer space, the instrumentation systems of the payload, where mentioned the previous systems employed in other payloads along the history. Thus, an instrumentation equipment towards the Kuiper belt objects is suggested. Lastly, a study of orbital mechanics for the approximate calculation of the payload path. The orbit of the International Space Station is suggested as a starting point, and with the right orbital changes, the arrival in Jupiter where we analyse how to arrive to Kuiper with -or without- the gravity assist. It should be taken into account that the work of designing a space mission involves years and many specialized people. Therefore, what the project accomplishes is a humble approach to the topic of interplanetary travelling with payloads, considering the limitations attached to the timing and resources when solving the problems that appear in the project’s development.

This concluding chapter shows practically that planetary defense is not about securing the mere absence of threat. Deflecting asteroids does not necessarily require its own dedicated technology. Quite the contrary, planetary defense can and should be approached as a civilian and scientific endeavor with historical importance. This will be challenging, but if we can build a laser capable of sending nanoprobes to the nearest stars at 20% light speed and use the same installation for possible asteroid deflection, then we should not need to rely on militarily oriented planetary defense by a leading nation. In this chapter, we discuss the associated challenges and required technologies, and also that our community of fate can become a security community—a community in which we do not perceive one another as enemies but as allies. We explain the science of Moon survival and structures for the multipurpose lunar base, as well as the main issues of building a super powerful laser on the Moon. The same installation can be built on Earth if we can reach a breakthrough in global governance. The chapter ends by discussing the notion that planetary defense is not national defense.

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.

The main benefit of an interstellar mission is to carry out in situ measurements within a target star system. To allow for extended in situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technology's shortcomings: a magnetic sail is more effective at higher velocities than the electric sail, whereas an electric sail demonstrates superior performance at low speeds. It is shown that using both sails sequentially outperforms using only the magnetic or electric sail for various mission scenarios and velocity ranges, at a constant total spacecraft mass. For example, for decelerating from 5% c, to interplanetary velocities, a spacecraft with both sails needs about 29 years, whereas the electric sail alone would take 35 years and the magnetic sail about 40 years with a total spacecraft mass of 8250 kg. Furthermore, it is assessed how the combined deceleration system affects the optimal overall mission architecture for different spacecraft masses and cruising speeds. Future work would investigate how operating both systems in parallel instead of sequentially would affect its performance. Moreover, uncertainties in the density of interstellar matter and sail properties need to be explored.

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.

The habitable zones of low-mass stars are characterized by escape speeds that can be a few times higher than the Earth's orbit around the Sun. Owing to the exponential dependence of the required fuel mass on the terminal speed for chemical rockets, interstellar travel may not be easy for technological species inhabiting planets around M-dwarfs., Accepted for publication in Research Notes of the AAS; 3 pages

Two technological problems must be solved before daring to interstellar flight: fuel and propulsion. The highest energy-density fuel is antimatter in its solid or liquid state and this fuel is likely to be our primary choice for multi-ton relativistic rockets. High-energy ion thruster powered by annihilation reactor promises superior performance in comparison with direct propulsion by annihilation products. However the power generator on board can significantly increase the rocket dry mass thus limiting the achievable speed. Two physical factors that stand against our dream of the stars are thermodynamics and radiation hazard. Heat-disposing radiator also increases the rocket dry mass. Interstellar gas turns into oncoming flux of hard ionizing radiation at a relativistic speed of the rocket while the oncoming relativistic interstellar dust grains can cause mechanical damage. Economy and psychology will play a decisive role in voting for or against the manned interstellar flights, 19 pages, 5 figures, acce[ted for publication in Acta Astronautica July 2018 article reference AA6993

In the search for habitable planets, the ultimate aspiration is finding an extraterrestrial technical civilization. We already lost a half of century for an active search for extraterrestrial civilizations. Should we lose another half? If all civilizations in the Universe are only recipients and not message-sending civilizations, then no SETI (Search for Extraterrestrial Intelligence) searches make any sense. Detecting only leaked radio signals is a hard job with present resources. Fear from the extraterrestrials is unfounded, having in mind physical difficulties and requirements of the interstellar travel. If possible extraterrestrial civilizations are more advanced than ours then they can pick up life signs from Earth easier than we can from their planets at present. Here we propose a scientifically based METI (Messaging to Extraterrestrial Intelligence) program.

The creator of an ideologically rich simulation of interplanetary colonization, Richard Garriott, has himself really traveled into space. The son of NASA astronaut Owen Garriott, Richard was a pioneer in creating the computer game industry with his Ultima series, then attempted to use the industry as a vehicle for promoting popular interest in spaceflight with Tabula Rasa, a massively multiplayer online game set on two imaginary planets, Foreas and Arieki. The name Tabula Rasa refers to the blank slate on which the player collects powerful Logos hieroglyphics hidden by an advanced intelligent species named Eloh that has apparently vanished, while battling the Neph traitors from Eloh civilization and their Bane army, in partnership with the Forean and Brann aliens. This conflict dramatized a rather sophisticated theory about the alternate meanings that interstellar travel might assume, in the history of our galaxy.

A very significant challenge in society’s relationship to spaceflight is the impossibility of quick travel over the cosmic distances that separate stars across our vast galaxy, leading contemporary computer simulations to adopt some of the literary conventions of classic science fiction, or Internet’s metaphor that a simple click on a hyperlink can leap instantly anywhere. Some massively social online simulations, like Jumpgate and EVE Online, explicitly use near-instantaneous teleportation between solar systems. Another challenge for galaxy simulations is how to create vast numbers of different planets and solar systems, and the solution used by Elite: Dangerous and No Man’s Sky is procedural generation algorithms that do the work without the need for people to create each and every simulated planet. Once it becomes possible to travel to vast numbers of worlds, the question becomes what forms of economic and social interaction will be possible.

Often called the Fermi Paradox, the apparent failure of other intelligent species to have invited humanity to join a galactic civilization suggests that intelligence may be very rare in the cosmos, or interstellar travel is technically too difficult, or some as-yet undiscovered socio-cultural factor is at work. Based on computer simulation research originally done for the British Interplanetary Society, this chapter suggests that cultural drift may be responsible, limiting the expansion of interstellar civilizations even after several solar systems have been colonized. It shows how variables may be adjusted in multiple runs of a simulation to measure the changing range of outcomes. The chapter concludes with a simulation that models not physical colonization but radio communication in a hypothetical galaxy that already has tens of thousands of intelligent species, that may or may not evolve toward shared regional cultures.

Interstellar travel is the term used for hypothetical piloted or unpiloted travel between stars. Interstellar travel will be much more difficult than interplanetary spaceflight; the distances between the planets in the Solar System are less than 30 astronomical units (AU), whereas the distances between stars are typically hundreds of thousands of AU.

International audience; PLATO stands for PLAnetary Transits and Oscillations and it is the forthcoming third Medium sized mission of ESA, planned to be launched in 2024. Its optical payload is an ensemble of 34 small telescopes that mimic a single one meter class aperture with a huge Field of View of more than 50 degrees in size. Aiming to find exoplanets around bright nearby stars it is designed to discover a significant number of relatively nearby Earth-like worlds. A description of the optomechanical adopted solution and a speculative scenario to further explore such alien worlds is briefly given. (C) 2015 IAA. Published by Elsevier Ltd. All rights reserved.

Hyperthin solar sails deployed as close to the Sun as possible are the only currently feasible approach to extrasolar solar exploration and interstellar travel. This paper quantifies and investigates the effects of timing errors in the unfurlment (or inflation) of solar sails at the perihelion of parabolic solar orbits upon the spacecraft's trajectory direction. Methods of correcting such aim errors include on-board solar-, radioisotope-, or nuclear-electric thrusters, electromagnetic thrustless turning, application of electric or magnetic sails, and a new application of toroidal magnetic ion scoops.

Co-founder of The Planetary Society, with Carl Sagan and Bruce C. Murray, he has been a guiding force with the Society for over 30 years and remains as excited as ever about humanity's journey into the solar system. His college career began when Sputnik launched the space age. Lou earned a B.S. in Applied Mathematics and Engineering Physics at the University of Wisconsin in 1961, followed by an M.S. in Engineering Mechanics at Cornell University in 1963. He earned his Ph.D. from the Aeronautics and Astronautics Department at M.I.T. in 1971 with a thesis on Extracting Scientific Information from Spacecraft Tracking Data. From 1963–1968, Lou worked at the AVCO Space Systems Division on both civilian and military space programs. The following decade, 1970–1980, found him at JPL, involved in planning deep space missions. His projects included Mariner-Venus-Mercury, the Grand Tour (Voyager), Venus Orbital Imaging Radar (Magellan), Halley Comet Rendezvous-Solar Sail, and the Mars Program. In 1978–79, Lou went to Washington, DC as the AIAA Congressional Fellow and worked on the staff of the subcommittee on Science, Technology, and Space of the Senate Committee on Commerce, Science and Transportation. He frequently returns to Washington, DC to testify to Congress regarding important issues concerning the space science community and the members of The Planetary Society. Although the solar sail never launched for Halley's Comet, the concept of using light to propel a spacecraft intrigued Lou so much that he wrote a book on the subject, Starsailing: Solar Sails and Interstellar Flight, and led Cosmos 1, the solar sail mission created by The Planetary Society and Cosmos Studios. He also conceived the Living Interplanetary Flight Experiment developed by The Planetary Society. Lou stepped down from the Executive Director position in 2010. Since then he has been co-leader of the Asteroid Redirect Mission program for the Keck Institute for Space Studies at Caltech and is completing a book that examines the future of human spaceflight from Mars to the stars. Dr. Friedman is a Corresponding Member of the International Academy of Astronautics.

Recent technological advances could make interstellar travel possible, using ultra-lightweight sails pushed by lasers or solar photon pressure, at speeds of a few percent the speed of light. Obtaining remote observational data from such probes is not trivial because of their minimal instrumentation (gram scale) and large distances (pc). We derive the optimal communication scheme to maximize the data rate between a remote probe and home-base. he framework requires coronagraphic suppression of the stellar background at the level of $10^{-9}$ within a few tenths of an arcsecond of the bright star. Our work includes models for the loss of photons from diffraction, technological limitations, interstellar extinction, and atmospheric transmission. Major noise sources are atmospheric, zodiacal, stellar and instrumental. We examine the maximum capacity using the "Holevo bound" which gives an upper limit to the amount of information (bits) that can be encoded through a quantum state (photons), which is a few bits per photon for optimistic signal and noise levels. This allows for data rates of order bits per second per Watt from a transmitter of size 1 m at a distance of $\alpha\,$Centauri (1.3 pc) to an earth-based large receiving telescope (E-ELT, 39 m). The optimal wavelength for this distance is 300 nm (space-based receiver) to 400 nm (earth-based) and increases with distance, due to extinction, to a maximum of $\approx3\,\mu$m to the center of the galaxy at 8 kpc., Comment: Accepted for publication in the International Journal of Astrobiology

Chapter 9, another chapter unique to this book, applies four-momentum conservation of Chapter 8 to rocket propulsion. The motion of fuel-carrying spacecraft is analyzed for massive as well as photon exhaust cases and their impracticality demonstrated. The alternative ground-based laser propulsion is covered in lengthy detail in light of the recent interest in such projects. The peculiarity of one-dimensional photon collisions is investigated and it is shown that both energy and momentum conservation are needed to come up with an equation that holds in all reference frames, unlike the equations in the existing literature. A manifestly relativistic differential equation of one-dimensional motion involving photons is derived and applied to the motion of a spacecraft equipped with a light sail from which laser photons can reflect. The position of the spacecraft as a function of speed is derived. The explicit time dependence of velocity is presented for the beginning of the voyage. It is shown that the craft has a terminal velocity determined by the characteristics of the ground-based lasers and the light sail. Nonrelativistic limits are obtained and shown to agree with those in the literature.

International audience; The classical theory of space-time, namely general relativity, suggests but does not demonstrate the existence of so-called wormholes allowing for interstellar journeys. Alternative proposals such as quantum gravity theories are developed nowadays to allow for wormhole travels by assuming hypothetical trans-Planckian effects at tiny scales. Here we show experimentally that analogue traversable and bidirectional wormholes exist in hydrodynamics following a suggestion by Wheeler. Using a water channel, we sent free surface waves on a countercurrent in an analogue gravity setup aiming at showing that hydrodynamic wormhole travels are controlled by a cascade of dispersive scales including surface tension effects: the capillary wavelength plays the role of a Planckian scale below which long gravity waves are transformed into short capillary waves that are able to move at speeds higher than the “flow” of space-time. Whereas our results do not apply to putative astrophysical wormholes per se, we anticipate that they will trigger new ideas to explore quantum gravity physics.