Breakthrough Starshot

The project was announced on 12 April 2016 in an event held in New York City by physicist and venture capitalist Yuri Milner, together with cosmologist Stephen Hawking, who was serving as board member of the initiatives. Other board members include Facebook, Inc. (now known as Meta Platforms) CEO Mark Zuckerberg. 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 Professor Avi Loeb chairs the advisory board for the project.{{Cite web |url=http://breakthroughinitiatives.org/leaders/3 |title=Breakthrough Starshot: Management and Advisory Committee}}

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 Alpha Centauri within the next generation.{{cite web|title=Breakthrough Initiatives|url=https://breakthroughinitiatives.org/Initiative/3|website=breakthroughinitiatives.org|access-date=10 January 2017}} 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.{{cite web|url=http://blogs.scientificamerican.com/life-unbounded/can-starshot-work/|title=Can Starshot Work?|first=Caleb A.|last=Scharf |work=Scientific American Blogs |date=26 April 2016 |access-date=25 August 2016}}

The European Southern Observatory (ESO) announced the detection of a planet orbiting the third star in the Alpha Centauri system, Proxima Centauri in August 2016.{{cite web|title=Planet Found in Habitable Zone Around Nearest Star – Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri|url=https://www.eso.org/public/news/eso1629/|website=eso.org|access-date=10 January 2017}}{{Cite journal|last1=Witze|first1=Alexandra|title=Earth-sized planet around nearby star is astronomy dream come true|journal=Nature|volume=536|issue=7617|pages=381–382|doi=10.1038/nature.2016.20445|pmid=27558041|date=25 August 2016|bibcode = 2016Natur.536..381W |s2cid=4405961|doi-access=free}} The planet, called Proxima Centauri b, orbits within the habitable zone 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.{{cite web |title=VLT to Search for Planets in Alpha Centauri System |url=https://www.eso.org/public/news/eso1702/ |work=European Space Observatory (ESO) |date=9 January 2017 |access-date=10 January 2017}}{{cite web|title=Breakthrough Initiatives| url=http://breakthroughinitiatives.org/News/8|website=breakthroughinitiatives.org|access-date=10 January 2017}} 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 (VLT) in Chile. This upgrade will increase the likelihood of planet detection in the system.

file:Solar Sail (14914129324).jpg

The Starshot concept envisions launching a "mothership" carrying about a thousand tiny spacecraft (on the scale of centimeters) to a high-altitude Earth orbit for deployment. A phased array 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.[http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=5&page=2 Lightsail, Integrity under thrust].[http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=6&page=1 Lightsail | Stability on the beam]. An October 2017 presentation of the Starshot system model{{Citation|title=2. Breakthrough Starshot System Model|date=20 October 2017|url=https://www.youtube.com/watch?v=KIDuXQHt8pk|access-date=29 October 2017}}{{Cite web|url=http://parkinresearch.com/interstellar/|title=Starshot System Model|last=Parkin|first=Kevin}} 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 habitable zone. Ideally, the Breakthrough Starshot would aim its spacecraft within one astronomical unit (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.{{cite web|url=http://breakthroughinitiatives.org/Target/3|title=Breakthrough Initiatives|work=breakthroughinitiatives.org|access-date=25 August 2016}}

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 lasers with a combined output of up to 100 GW.{{cite web |url=http://breakthroughinitiatives.org/Concept/3 |title=Breakthrough Starshot: Concept |date=12 April 2016 |access-date=14 April 2016 }} A swarm of about 1000 units would compensate for the losses caused by interstellar dust collisions en route to the target.{{cite news |last=Emspak |first=Jesse |url=http://www.space.com/32592-breakthrough-starshot-interstellar-laser-sail-challenges.html |title=No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges |work=Space |date=15 April 2016 |access-date=15 April 2016 }} In a detailed study in 2016, Thiem Hoang and coauthors{{cite journal |last1=Hoang |author2-link=Alexandre Lazarian|last2= Lazarian |first2=A. |last3=Burkhart |first3=Blakesley |last4=Loeb |first4=Abraham |bibcode=2017ApJ...837....5H |title=The Interaction of Relativistic Spacecrafts with the Interstellar Medium|journal= The Astrophysical Journal|volume= 837|issue= 1|page= 5|arxiv=1608.05284|doi=10.3847/1538-4357/aa5da6|year= 2017|s2cid=55427720 |doi-access=free }} found that mitigating the collisions with dust, hydrogen, 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.{{cite news |last=Timmer |first=John |url=https://arstechnica.com/science/2016/08/could-breakthrough-starshots-ships-survive-the-trip/ |title=Just how dangerous is it to travel at 20% the speed of light? | publisher=Ars Technica |work=Science |date=24 August 2016 |access-date=28 August 2016 }}

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 of thrust.{{cite news| title=A new plan to send spacecraft to the stars: replace rockets with lasers| url=https://www.economist.com/news/science-and-technology/21696876-interstellar-travel-means-thinking-both-very-big-and-very-small-new-plan| access-date=13 April 2016| newspaper=The Economist| date=12 April 2016}} 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.{{cite web |url=http://breakthroughinitiatives.org/Challenges/3 |title=Potential Challenges for Starshot |work=Breakthrough Initiatives |access-date=14 April 2016 }} All components must be engineered to endure extreme acceleration, cold, vacuum, and protons. The spacecraft will have to survive collisions with space dust; 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.{{cite web|title=Interstellar Dust |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=7&page=1 |work=Breakthrough Initiatives |access-date=15 April 2016}} Focusing a set of lasers totaling one hundred gigawatts onto the solar sail will be difficult due to atmospheric turbulence, so there is the suggestion to use space-based laser infrastructure.{{cite journal |title=The Andromeda Study: A Femto-Spacecraft Mission to Alpha Centauri |author1=Andreas M. Hein |author2=Kelvin F. Long |author3=Dan Fries |author4=Nikolaos Perakis |author5=Angelo Genovese |author6=Stefan Zeidler |author7=Martin Langer |author8=Richard Osborne |author9=Rob Swinney |author10=John Davies |author11=Bill Cress |author12=Marc Casson |author13=Adrian Mann |author14=Rachel Armstrong |journal=Initiative for Interstellar Studies |year=2017

|arxiv=1708.03556}} 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.{{Cite web |last=Paschotta |first=Dr Rüdiger |title=Coherent beam combining |url=https://www.rp-photonics.com/coherent_beam_combining.html |access-date=2024-01-05 |website=rp-photonics.com}}{{Cite web |title=Resolving power |url=http://labman.phys.utk.edu/phys136core/modules/m9/resolving_power.html |access-date=2024-01-05 |website=labman.phys.utk.edu}} 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.{{Cite web |title=Starlight |url=https://www.deepspace.ucsb.edu/projects/starlight |access-date=2024-01-06}}{{Citation |title=Large Scale Directed Energy for Relativistic Flight | date=25 August 2023 |url=https://www.youtube.com/watch?v=iyUoFwNM9xI |access-date=2024-01-06}} According to The Economist, at least a dozen off-the-shelf technologies will need to improve by orders of magnitude.

StarChip is the name used by Breakthrough Initiatives for a very small, centimeter-sized, gram-scale, interstellar spacecraft envisioned for the Breakthrough Starshot program,{{cite web |last=Greene |first=Kate |title=What Will Make Interstellar Travel a Reality? |url=http://www.slate.com/articles/health_and_science/science/2016/04/an_100_million_investment_might_make_it_possible_to_reach_alpha_centauri.html |date=13 April 2016 |work=Slate |access-date=16 April 2016 }} a proposed mission to propel a fleet of a thousand StarChips on a journey to Alpha Centauri, the nearest star system, about 4.37 light-years from Earth.{{cite journal |last=Clery |first=Daniel |title=Russian billionaire unveils big plan to build tiny interstellar spacecraft |url=https://www.science.org/content/article/russian-billionaire-unveils-big-plan-build-tiny-interstellar-spacecraft |date=12 April 2016 |journal=Science |doi=10.1126/science.aaf4115 |access-date=15 April 2016 |url-access=subscription }}{{cite news |last= Stone |first=Maddie |url=https://gizmodo.com/a-russian-billionaire-and-stephen-hawking-want-to-build-1770467186 |title=Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship |work=Gizmodo |date=12 April 2016 |access-date=12 April 2016 }}{{cite news |last=Domonoske |first=Camila |title=Forget Starships: New Proposal Would Use 'Starchips' To Visit Alpha Centauri |url=https://www.npr.org/sections/thetwo-way/2016/04/12/473960826/forget-starships-new-proposal-would-use-starchips-to-visit-alpha-centauri |date=12 April 2016 |publisher=NPR |access-date=15 April 2016 }}{{cite web |last=Emspak |first=Jesse |title=No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges |url=http://www.space.com/32592-breakthrough-starshot-interstellar-laser-sail-challenges.html |date=15 April 2016 |work=Space.com |access-date=15 April 2016 }} The journey may include a flyby of Proxima Centauri b, an Earth-sized exoplanet that is in the habitable zone 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 speed of light, 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 from Satish Dhawan Space Centre.{{cite web |author=Staff |title=In Quest To Reach Alpha Centauri, BreakThrough Starshot Launches World's Smallest Spacecraft – First Prototype 'Sprites' – Precursors to Eventual 'StarChip' Probes – Achieve Low Earth Orbit |url=https://breakthroughinitiatives.org/News/12 |date=26 July 2017 |work=BreakThroughInitiatives.org |access-date=28 July 2017 }} 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.{{Cite web|url=https://news.stanford.edu/2019/06/03/chip-size-satellites-orbit-earth/|title=Inexpensive chip-size satellites orbit Earth|last=University|first=Stanford| date=2019-06-03|website=Stanford News|access-date=2019-06-03}}{{Cite web|url=http://www.nasa.gov/ames/kicksat|title=What is KickSat-2?|last=Tavares|first=Frank|date=2019-05-30|website=NASA|access-date=2019-06-05}}{{Cite web|url=https://news.cornell.edu/stories/2019/06/cracker-sized-satellites-demonstrate-new-space-tech|title=Cracker-sized satellites demonstrate new space tech|website=Cornell Chronicle|access-date=2019-06-05}}{{Cite web|url=https://techcrunch.com/2019/06/04/kicksat-2-project-launches-105-cracker-sized-satellites/|title=KickSat-2 project launches 105 cracker-sized satellites|website=TechCrunch|date=4 June 2019|access-date=2019-06-05}}

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.{{cite web |author=Staff |title=Breakthrough Starshot: Potential Challenges |url=http://breakthroughinitiatives.org/Challenges/3 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=14 April 2016 }}{{cite news |author=Staff |title=Starship enterprise |url=https://www.economist.com/news/science-and-technology/21696876-interstellar-travel-means-thinking-both-very-big-and-very-small-new-plan |date=16 April 2016 |newspaper=The Economist |access-date=15 April 2016 }}

Five sub-gram scale digital cameras, each with a minimum 2-megapixels resolution, are envisioned.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Cameras |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=18&page=1 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }}

Four sub-gram scale processors are planned.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Processors |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=19&page=1 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }}

Four sub-gram scale photon thrusters, each minimally capable of performing at a 1W diode laser level, are planned.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Photon Thrusters |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=17&page=1 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }}{{cite web |last=Gilster |first=Paul |title=Laser Travel by Photonic Thruster |url=http://www.centauri-dreams.org/?p=29341 |date=21 October 2013 |work=Centauri Dreams |access-date=16 April 2016 }}

A 150 mg atomic battery, powered by plutonium-238 or americium-241, is planned.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – Battery |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=16&page=1 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }}

A coating, possibly made of beryllium copper, is planned to protect the nanocraft from dust collisions and atomic particle erosion.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – Protective Coating |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=20&page=1 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }}

The light sail is envisioned to be no larger than {{convert|4 × 4|meter|ft|abbr=off}},{{cite web|author=Staff |title=Breakthrough Starshot: Lightsail, Integrity under thrust |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=5&page=2 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=16 April 2016 }} possibly of composite graphene-based material.{{cite web |author=Staff |title=Breakthrouth Starshot: Gram-Scale Starchip Components – Lightsail – Structure |url=http://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=21&page=2 |date=12 April 2016 |work=Breakthrough Initiatives |access-date=15 April 2016 }} 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.{{cite news |last=Patel |first=Neel V. |url=https://www.inverse.com/article/14352-the-starshot-breakthrough-light-beam-is-really-a-million-lasers-which-s-insane |title=The Starshot Breakthrough Light Beam Is Really a Million Lasers, Which Is Insane |work=Inverse |date=15 April 2016 |access-date=16 April 2016 }} 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.

A laser communicator, utilizing the light sail as the primary reflector, would be capable of data rates of 2.6-15 baud per watt of transmitted power at the distance to Alpha Centauri, assuming a 30 m diameter receiving telescope on Earth.{{cite arXiv|eprint=2005.08940|last1=Parkin|first1=Kevin L. G.|title=A Starshot Communication Downlink|year=2020|class=astro-ph.IM}}

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.{{Cite journal|arxiv=1704.03871|last1=Heller|first1=René|title=Optimized trajectories to the nearest stars using lightweight high-velocity photon sails|journal=The Astronomical Journal|volume=154|issue=3|page=115|last2=Hippke|first2=Michael|last3=Kervella|first3=Pierre|year=2017|doi=10.3847/1538-3881/aa813f|bibcode=2017AJ....154..115H|s2cid=119070263 |doi-access=free }} 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)

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 of unicellular microbes on otherwise only transiently habitable exoplanets.{{citation|doi=10.1007/s10509-016-2911-0|title=Developing ecospheres on transiently habitable planets: The genesis project|journal=Astrophysics and Space Science|volume=361|issue=10|page=324|year=2016|last1=Gros|first1=Claudius|author-link=Claudius Gros|bibcode=2016Ap&SS.361..324G|arxiv=1608.06087|s2cid=6106567}}{{cite journal|last1=Boddy|first1=Jessica|title=Q&A: Should we seed life on alien worlds?|journal=Science|year=2016|issn=0036-8075|doi=10.1126/science.aah7285}} 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.{{Cite magazine |first=James |last=Romero |url=https://www.newscientist.com/article/2153165-should-we-seed-life-through-the-cosmos-using-laser-driven-ships |title=Should we seed life through the cosmos using laser-driven ships? |magazine=New Scientist |date=November 2017 |issue=3152}}

In 2025, researchers from Brown University and TU Delft developed a cutting-edge, ultra-thin light sail optimized with artificial intelligence. 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.{{cite web |url=https://scitechdaily.com/breakthrough-lightsail-ultra-thin-ai-optimized-and-ready-to-race-to-alpha-centauri/ |title=Breakthrough Lightsail: Ultra-Thin, AI-Optimized, and Ready to Race to Alpha Centauri |publisher=SciTechDaily |date=31 March 2025 }}

{{Div col}}

• Interstellar probe
• {{annotated link|Project Dragonfly (space study)|Project Dragonfly}}
• {{annotated link|Project Daedalus}}
• {{annotated link|Project Icarus (interstellar)|Project Icarus}}
• {{annotated link|Project Longshot}}
• {{annotated link|2069 Alpha Centauri mission}}
• {{annotated link|Starlight (interstellar probe)|Starlight}}
• {{annotated link|Starwisp}}
• Interstellar travel
• {{annotated link|Starship}}
• {{annotated link|100 Year Starship}}

{{div col end}}

{{reflist}}

• {{Official website|http://breakthroughinitiatives.org/Initiative/3}}

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