Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a

proof-of-concept A proof of concept (POC or PoC), also known as proof of principle, is an inchoate realization of a certain idea or method in order to demonstrate its feasibility or viability. A proof of concept is usually small and may or may not be complete ...

fleet of light sail

interstellar probe An interstellar probe is a space probe that has left—or is expected to leave—the Solar System and enter interstellar medium, interstellar space, which is typically defined as the region beyond the Heliopause (astronomy), heliopause. It also r ...

s named ''Starchip'', to be capable of making the journey to the

Alpha Centauri Alpha Centauri (, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus (constellation), Centaurus. It consists of three stars: Rigil Kentaurus (), Toliman (), and Proxima Centauri (). Proxima Centauri ...

star system 4.34 light-years away. It was founded in 2016 by Yuri Milner,

Stephen Hawking Stephen William Hawking (8January 194214March 2018) was an English theoretical physics, theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between ...

, and

Mark Zuckerberg Mark Elliot Zuckerberg (; born May 14, 1984) is an American businessman who co-founded the social media service Facebook and its parent company Meta Platforms, of which he is the chairman, chief executive officer, and controlling sharehold ...

. A flyby mission has been proposed to Proxima Centauri b, an Earth-sized

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

in the

habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...

of its host star,

Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years away in the southern constellation of Centaurus. This object was discovered in 1915 by Robert T. A. Innes, Robert Innes. It is a small, low-mass st ...

, in the Alpha Centauri system. At a speed between 15% and 20% of the

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

, it would take between 20 and 30 years to complete the journey, and approximately 4 years for a return message from the starship to Earth. The conceptual principles to enable this interstellar travel project were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara.(file available at University of California, Santa Barbar
here
Accessed 16 April 2016) Sending the lightweight spacecraft involves a multi-kilometer

phased array In antenna (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...

of beam-steerable

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

s with a combined coherent power output of up to 100 GW.

General

The project was announced on 12 April 2016 in an event held in

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

by physicist and venture capitalist Yuri Milner, together with cosmologist

, who was serving as board member of the initiatives. Other board members include Facebook, Inc. (now known as

Meta Platforms Meta Platforms, Inc. is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, Threads ...

) CEO

. The project has an initial funding of US$100 million. Milner places the final mission cost at $5–10 billion, and estimates the first craft could launch by around 2036. Pete Worden is the project's executive director and

Harvard Harvard University is a private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher lear ...

Professor Avi Loeb chairs the advisory board for the project.

Objectives

The Breakthrough Starshot program aims to demonstrate a proof-of-concept for ultra-fast, light-driven nano-spacecraft, and lay the foundations for a first launch to

within the next generation. The spacecraft would make a flyby, and possibly photograph, of any Earth-like worlds that might exist in the system. Secondary goals are Solar System exploration and detection of Earth-crossing asteroids.

Target planet

The

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 m ...

(ESO) announced the detection of a planet orbiting the third star in the Alpha Centauri system,

in August 2016. The planet, called Proxima Centauri b, orbits within the

of its star. It could be a target for one of the Breakthrough Initiatives' projects. In January 2017, Breakthrough Initiatives and the European Southern Observatory began collaborating to search for habitable planets in the nearby star system Alpha Centauri. The agreement involves Breakthrough Initiatives providing funding for an upgrade to the VISIR (VLT Imager and Spectrometer for mid-Infrared) instrument on ESO's

Very Large Telescope The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with ...

(VLT) in

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. This upgrade will increase the likelihood of planet detection in the system.

Concept

A solar sail concept The Starshot concept envisions launching a "

mothership A mother ship, mothership or mother-ship is a large vehicle that leads, serves, or carries other smaller vehicles. A mother ship may be a maritime ship, aircraft, or spacecraft. Examples include bomber aircraft, bombers converted to carry exp ...

" carrying about a thousand tiny spacecraft (on the scale of centimeters) to a high-altitude Earth orbit for deployment. A

of ground-based lasers would then focus a light beam on the sails of these spacecraft to accelerate them one by one to the target speed within 10 minutes, with an average acceleration on the order of 100 km/s² (10,000 ɡ), and an illumination energy on the order of 1 TJ delivered to each sail. A preliminary sail model is suggested to have a surface area of 4 m × 4 m. An October 2017 presentation of the Starshot system model examined circular sails and finds that the beam director capital cost is minimized by having a sail diameter of 5 meters. The Earth-sized planet Proxima Centauri b is within the Alpha Centauri system's

. Ideally, the Breakthrough Starshot would aim its spacecraft within one

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

(150 million kilometers or 93 million miles) of that world. From this distance, a craft's cameras could capture an image of high enough resolution to resolve surface features. The fleet would have about 1000 spacecraft. Each one, called a StarChip, would be a very small centimeter-sized vehicle weighing a few grams. They would be propelled by a square-kilometre array of 10 kW ground-based

s with a combined output of up to 100 GW. A swarm of about 1000 units would compensate for the losses caused by interstellar dust collisions ''en route'' to the target. In a detailed study in 2016, Thiem Hoang and coauthors found that mitigating the collisions with

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

, and galactic cosmic rays may not be as severe an engineering problem as first thought, although it will likely limit the quality of the sensors on board.

Technical challenges

Light propulsion requires enormous power: a laser with a gigawatt of power (approximately the output of a large nuclear plant) would provide only a few

newtons The newton (symbol: N) is the unit of force in the International System of Units (SI). Expressed in terms of SI base units, it is 1 kg⋅m/s2, the force that accelerates a mass of one kilogram at one metre per second squared. The unit i ...

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...

. The spaceship will compensate for the low thrust by having a mass of only a few grams. The camera, computer, communications laser, a nuclear power source, and the solar sail must be miniaturized to fit within a mass limit. All components must be engineered to endure extreme

acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Acceleration is one of several components of kinematics, the study of motion. Accelerations are Euclidean vector, vector ...

, cold, vacuum, and protons. The spacecraft will have to survive collisions with

space dust Cosmic dustalso called extraterrestrial dust, space dust, or star dustis dust that occurs in outer space or has fallen onto Earth. Most cosmic dust particles measure between a few molecules and , such as micrometeoroids (30 μm). Cosmic dust can ...

; Starshot expects each square centimeter of frontal cross-section to collide at high speed with about a thousand particles of size at least 0.1 μm. Focusing a set of lasers totaling one hundred gigawatts onto the solar sail will be difficult due to

atmospheric turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between t ...

, so there is the suggestion to use space-based laser infrastructure. In addition, due to the size of the light sail and distance the light sail will be from the laser at the end of the acceleration, very large coherent combining optics would be required to focus the laser. The diffraction limit of the laser light used sets the minimum diameter of the coherently focused laser beam at the source. For example, to accelerate the previously mentioned 4m sail at 10,000Gs to 0.2 ''c'' requires combining optics which are approximately 3 kilometers in diameter to focus the laser light on the sail. This could be implemented using a phased array system which is being researched at The University of California Santa Barbara. According to ''

The Economist ''The Economist'' is a British newspaper published weekly in printed magazine format and daily on Electronic publishing, digital platforms. It publishes stories on topics that include economics, business, geopolitics, technology and culture. M ...

'', at least a dozen off-the-shelf technologies will need to improve by

orders of magnitude In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are wi ...

StarChip

StarChip is the name used by Breakthrough Initiatives for a very small, centimeter-sized, gram-scale, interstellar

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

envisioned for the Breakthrough Starshot program, a proposed mission to propel a fleet of a thousand ''StarChips'' on a journey to

, the nearest

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...

, about 4.37 light-years from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. The journey may include a flyby of Proxima Centauri b, an Earth-sized

that is in the

of its host star. The ultra-light ''StarChip'' robotic nanocraft, fitted with light sails, are planned to travel at speeds of 20% and 15% of the

, taking between 20 and 30 years to reach the star system, respectively, and about 4 years to notify Earth of a successful arrival. The conceptual principles to enable practical interstellar travel were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara, who is an advisor to the Starshot project. In July 2017, scientists announced that precursors to ''StarChip'', called Sprites, were successfully launched and flown through Polar Satellite Launch Vehicle by

ISRO The Indian Space Research Organisation (ISRO ) is India's national space agency, headquartered in Bengaluru, Karnataka. It serves as the principal research and development arm of the Department of Space (DoS), overseen by the Prime Minister o ...

from Satish Dhawan Space Centre. 105 Sprites were also flown to the ISS on the KickSat-2 mission that launched on 17 November 2018, from where they were deployed on 18 March 2019. They successfully transmitted data before reentering the atmosphere and burning up on 21 March.

Components

Each ''StarChip'' nanocraft is expected to carry miniaturized cameras, navigation gear, communication equipment, photon thrusters and a power supply. In addition, each nanocraft would be fitted with a meter-scale light sail, made of lightweight materials, with a gram-scale mass.

Cameras

Five sub-gram scale

digital camera A digital camera, also called a digicam, is a camera that captures photographs in Digital data storage, digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film or film stock. Dig ...

s, each with a minimum 2-

megapixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...

s resolution, are envisioned.

Processors

Four sub-gram scale processors are planned.

Photon thrusters

Four sub-gram scale photon thrusters, each minimally capable of performing at a 1W diode

level, are planned.

Battery

A 150 mg atomic battery, powered by

plutonium-238 Plutonium-238 ( or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage ...

americium-241 Americium-241 (Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of . Am is the most common isotope of americium as well as the most prevalent isotope of americium in nuclear waste. It ...

, is planned.

Protective coating

A coating, possibly made of

beryllium copper Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze, and spring copper, is a copper alloy with 0.5–3% beryllium. Copper beryllium alloys are often used because of their high strength and good conductivity of both ...

, is planned to protect the nanocraft from

collisions and atomic particle erosion.

Light sail

The light sail is envisioned to be no larger than , possibly of composite

graphene Graphene () is a carbon allotrope consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice, honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating ...

-based material. The material would have to be very thin and be able to reflect the laser beam while absorbing only a small fraction of the incident energy, or it will vaporize the sail. The light sail may also double as power source during cruise, because collisions with atoms of interstellar medium would deliver 60 watt/m² of power.

Laser data transmitter

A laser communicator, utilizing the light sail as the primary reflector, would be capable of data rates of 2.6-15

baud In telecommunications and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulat ...

per watt of transmitted power at the distance to Alpha Centauri, assuming a 30 m diameter receiving telescope on Earth.

Orbital insertion

The Starshot project is for fly-by missions, which pass the target at high velocity. Heller ''et al.'' proposed that a photo-gravitational assist could be used to slow such a probe and allow it to enter orbit (using photon pressure in maneuvers similar to aerobraking). This requires a sail that is both much lighter and much larger than the proposed Starshot sail. The table below lists possible target stars for photogravitational assist rendezvous. The travel times are the calculated times for an optimized spacecraft to travel to the star and then enter orbit around the star. * Successive assists at α Cen A and B could allow travel times to 75 yr to both stars. * The light sail has a nominal mass-to-surface ratio (σ_nom) of 8.6×10⁻⁴ gram m⁻² for a nominal graphene-class sail. * Area of the light sail, about 10⁵ m² = (316 m)² * Velocity up to 37,300 km s⁻¹ (12.5% c)

Other applications

The German physicist Claudius Gros has proposed that the technology of the Breakthrough Starshot initiative may be used in a second step to establish a

biosphere The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...

of unicellular microbes on otherwise only transiently habitable

s. A Genesis probe would travel at lower speeds, at a speed 4.6% of the speed of light, which would take at least 90 years to get to Alpha Centauri A. The sail could be configured so that the stellar pressure from Alpha Centauri A brakes and deflects the probe toward Alpha Centauri B, where it would arrive after a few days. The sail would then be slowed again to 0.4% of the speed of light and catapulted towards Proxima Centauri. At that speed it will arrive there after another 46 years – about 140 years after its launch. It could hence be decelerated using a magnetic sail.

AI-optimized light sail

In 2025, researchers from

Brown University Brown University is a Private university, private Ivy League research university in Providence, Rhode Island, United States. It is the List of colonial colleges, seventh-oldest institution of higher education in the US, founded in 1764 as the ' ...

and TU Delft developed a cutting-edge, ultra-thin light sail optimized with

artificial intelligence Artificial intelligence (AI) is the capability of computer, computational systems to perform tasks typically associated with human intelligence, such as learning, reasoning, problem-solving, perception, and decision-making. It is a field of re ...

. This light sail, designed for interstellar missions, was only 200 nanometers thick, with a surface covered in billions of nanoscale holes. These microscopic holes reduced weight while significantly increasing reflectivity, making the light sail more efficient for light-driven propulsion. This breakthrough could play a crucial role in advancing interstellar travel, allowing spacecraft to reach distant stars within a human lifetime.

References

External links

* {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Alpha Centauri Interstellar travel Proposed space probes Proxima Centauri Projects established in 2016 Yuri Milner Stephen Hawking