# Breakthrough Starshot
**Breakthrough Starshot** is a research program announced on April 12, 2016, by the internet investor and science philanthropist [Yuri Milner](https://www.edgepedia.org/yuri-milner) and the cosmologist [Stephen Hawking](https://www.edgepedia.org/stephen-hawking), with the goal of propelling gram-scale spacecraft to the [Alpha Centauri](https://www.edgepedia.org/alpha-centauri) star system within a generation using a powerful ground-based laser array and light sails.[1](https://www.prnewswire.com/news-releases/internet-investor-and-science-philanthropist-yuri-milner--physicist-stephen-hawking-announce-breakthrough-starshot-project-to-develop-100-million-mile-per-hour-mission-to-the-stars-within-a-generation-300249986.html) Milner kick-started the initial development with $100 million.[2](https://www.scientificamerican.com/article/100-million-plan-will-send-probes-to-the-nearest-star1/) The announcement took place at One World Observatory in New York City, on the 55th anniversary of Yuri Gagarin's spaceflight.[1](https://www.prnewswire.com/news-releases/internet-investor-and-science-philanthropist-yuri-milner--physicist-stephen-hawking-announce-breakthrough-starshot-project-to-develop-100-million-mile-per-hour-mission-to-the-stars-within-a-generation-300249986.html) • [3](https://physicstoday.aip.org/opinion/breakthrough-starshot-started-with-a-bang)
| Key fact | Detail |
|---|---|
| Announced | April 12, 2016, at One World Observatory, New York, by Yuri Milner and Stephen Hawking[1](https://www.prnewswire.com/news-releases/internet-investor-and-science-philanthropist-yuri-milner--physicist-stephen-hawking-announce-breakthrough-starshot-project-to-develop-100-million-mile-per-hour-mission-to-the-stars-within-a-generation-300249986.html) |
| Initial funding | $100 million from Milner for early development[2](https://www.scientificamerican.com/article/100-million-plan-will-send-probes-to-the-nearest-star1/) |
| Propulsion concept | Kilometer-scale, ground-based 100 GW coherent phased-array laser pushing a sail of a few grams by photon momentum transfer[4](https://opg.optica.org/ao/abstract.cfm?uri=ao-60-31-H20) |
| Cruise speed | About 0.2c, one fifth the speed of light[5](https://arxiv.org/abs/1704.04310) |
| Destination and flight time | Alpha Centauri system, 4.37 light years away, in about 20 years[6](https://web.stanford.edu/~cantwell/AA283_Course_Material/AA283_Lectures/AA283_Chapter_12_Space_Sailing_Photonic_Propulsion_Brian_J_Cantwell_2024.pdf) |
| Status | Effectively defunct; funding frozen since late 2025, with no final project report published[7](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/) |
## Mission concept
The plan called for a tiny spacecraft, described as a nanocraft or StarChip, weighing no more than a few grams and built around a small computer chip carrying cameras, sensors, and communications equipment, attached to a light sail roughly 4 meters across.[7](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/) • [8](https://www.johnlyon.org/wp-content/uploads/STEAMMagSummer2021.pdf) A fleet of about a thousand such craft would be carried to orbit by a conventional rocket mothership and deployed one at a time.[8](https://www.johnlyon.org/wp-content/uploads/STEAMMagSummer2021.pdf)
**Propulsion.** Because the craft carry no fuel, acceleration comes from photon momentum transfer. A kilometer-scale, ground-based coherent phased-array laser, built from many small lasers ganged so their light combines into a single beam, would illuminate each sail for a few minutes and drive it to about 20 percent of the speed of light.[4](https://opg.optica.org/ao/abstract.cfm?uri=ao-60-31-H20) • [9](https://www.scientificamerican.com/article/inside-the-breakthrough-starshot-mission-to-alpha-centauri/) • [8](https://www.johnlyon.org/wp-content/uploads/STEAMMagSummer2021.pdf) The sail would need to withstand an acceleration up to 60,000 g; in an early laboratory test, Philip Lubin's team achieved about 13 g.[9](https://www.scientificamerican.com/article/inside-the-breakthrough-starshot-mission-to-alpha-centauri/) Thermal analysis indicates that, for firing times of a few minutes and operating temperatures below 300 degrees C (573 K), the sail must absorb fewer than 1 in 260,000 incident photons.[5](https://arxiv.org/abs/1704.04310)
**Flight and data return.** At 0.2c the transit to Alpha Centauri, 4.37 light years away, takes about 20 years.[6](https://web.stanford.edu/~cantwell/AA283_Course_Material/AA283_Lectures/AA283_Chapter_12_Space_Sailing_Photonic_Propulsion_Brian_J_Cantwell_2024.pdf) As the sailcraft transits the system, it would look for signs of life by imaging planets and gathering other scientific data, then transmit findings back to Earth.[10](https://arxiv.org/abs/2005.08940) For comparison, the [New Horizons](https://www.edgepedia.org/new-horizons) probe, one of the fastest spacecraft in history, would need nearly 80,000 years to reach the same stellar system.[11](https://www.pbs.org/newshour/science/stephen-hawking-yuri-milner-launch-new-space-exploration)
## Organization and funding
Milner funded the Breakthrough Prizes and other Breakthrough Initiatives before Starshot, and he framed the project as open source, calling for researchers across the globe to contribute.[11](https://www.pbs.org/newshour/science/stephen-hawking-yuri-milner-launch-new-space-exploration) Chaired by Harvard professor [Avi Loeb](https://www.edgepedia.org/avi-loeb), the project sought to prove the feasibility of nanocrafts propelled at extreme speeds by light, while establishing the groundwork for an initial voyage to Alpha Centauri within a generation.[12](https://lweb.cfa.harvard.edu/~loeb/Loeb_Starshot.pdf) The advisory committee included experts in lasers, sails, chips, exoplanets, aeronautics, and large-project management, among them two Nobel Prize winners and the UK's Astronomer Royal.[9](https://www.scientificamerican.com/article/inside-the-breakthrough-starshot-mission-to-alpha-centauri/)
The $100 million covered initial development only. Philip Lubin of the [University of California, Santa Barbara](https://www.edgepedia.org/university-of-california-santa-barbara), whose laser phased-array work shaped the concept, later said that Breakthrough contributed less than 5 percent of the funding in his program.[7](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/) A system-model study estimated that a 0.01c point design would assume $1/W lasers, $10,000 per square meter of optics, and $100/kWh energy storage, giving a $517 million capital cost for the beam director and an $8,000 energy cost to accelerate each 19 cm diameter sail.[13](https://www.sciencedirect.com/science/article/pii/S0094576518310543)
## Engineering challenges
Early on, the project recognized where its greatest difficulties lay: how to build the sail, how to make the laser system work, what the spacecraft should consist of, and how to create a communications device able to transmit back to Earth across distances of light-years.[7](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/) Research addressed several of these areas:
- **Beam-riding stability.** A sail must hold its position on the laser beam during acceleration. Studies modeled the nanocraft as a rigid body with a flat or concave circular sail and mirror reflection of the beam, and later work analyzed dynamic stability using Lyapunov theory.[14](https://arxiv.org/abs/1610.08043) • [15](https://arxiv.org/abs/2203.14699) Metasail designs have been proposed that provide self-stabilized beam-riding and optical communication in the same structure.[16](https://www.sciencedirect.com/org/science/article/pii/S2516023023025005)
- **The interstellar medium.** At 0.2c the craft sweeps through dust and gas, mostly hydrogen, and calculations of particle bombardment identified this as a significant hazard for a gram-scale probe on a 20-year mission.[17](https://arxiv.org/abs/2307.12160)
- **The laser itself.** The 2021 assessment by the Starshot team, including former NASA Ames director S. Pete Worden, found no physical or economic restrictions that would preclude the 100 GW phased-array laser, while noting that challenges remained.[4](https://opg.optica.org/ao/abstract.cfm?uri=ao-60-31-H20)
## Outcome
Nine and a half years after its launch, the project had effectively ended. [Scientific American](https://www.edgepedia.org/scientific-american) reported in 2025 that Breakthrough Starshot had been on hold with its funding frozen since late 2025, that physicists at the [University of Sydney](https://www.edgepedia.org/university-of-sydney) learned of the stoppage only informally, and that a promised project report, expected around spring 2025, had not appeared by the time the article went to print.[7](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/) A German report in *Die Zeit* summarized the same finding: practically dead.[18](https://www.zeit.de/wissen/2025-09/breakthrough-starshot-forschung-raumfahrt-finanzierung) The project's technology development nonetheless left results that other programs can use, including work on ultrathin lightsail membranes and direct radiation-pressure measurements pursued at Caltech, and a 2025 technology-readiness assessment rated the components of Starshot's giant laser among the least mature elements of any proposed lightsail mission.[19](https://www.space.com/astronomy/can-solar-sails-really-send-humans-out-into-interstellar-space)
## References
1. [Internet Investor and Science Philanthropist Yuri Milner & Physicist Stephen Hawking Announce Breakthrough Starshot Project, PR Newswire (April 12, 2016)](https://www.prnewswire.com/news-releases/internet-investor-and-science-philanthropist-yuri-milner--physicist-stephen-hawking-announce-breakthrough-starshot-project-to-develop-100-million-mile-per-hour-mission-to-the-stars-within-a-generation-300249986.html)
2. [$100-Million Plan Will Send Probes to the Nearest Star, Scientific American (April 12, 2016)](https://www.scientificamerican.com/article/100-million-plan-will-send-probes-to-the-nearest-star1/)
3. [Breakthrough Starshot started with a bang, Physics Today (May 19, 2016)](https://physicstoday.aip.org/opinion/breakthrough-starshot-started-with-a-bang)
4. [S. Pete Worden et al., Progress on the Starshot laser propulsion system, Applied Optics 60, H20 (2021)](https://opg.optica.org/ao/abstract.cfm?uri=ao-60-31-H20)
5. [Relativistic Light Sails, arXiv:1704.04310](https://arxiv.org/abs/1704.04310)
6. [Breakthrough – Starshot – 2018, Stanford AA283 course material, B. J. Cantwell](https://web.stanford.edu/~cantwell/AA283_Course_Material/AA283_Lectures/AA283_Chapter_12_Space_Sailing_Photonic_Propulsion_Brian_J_Cantwell_2024.pdf)
7. [The Quiet Demise of Breakthrough Starshot, Scientific American (2025)](https://www.scientificamerican.com/article/the-quiet-demise-of-breakthrough-starshot-a-billionaires-interstellar/)
8. [STEAM Magazine, Summer 2021, John Lyon School](https://www.johnlyon.org/wp-content/uploads/STEAMMagSummer2021.pdf)
9. [Inside the Breakthrough Starshot Mission to Alpha Centauri, Scientific American (2016)](https://www.scientificamerican.com/article/inside-the-breakthrough-starshot-mission-to-alpha-centauri/)
10. [A Starshot Communication Downlink, arXiv:2005.08940](https://arxiv.org/abs/2005.08940)
11. [Stephen Hawking and billionaire plan interstellar cruise with $100 million initiative, PBS NewsHour (April 12, 2016)](https://www.pbs.org/newshour/science/stephen-hawking-yuri-milner-launch-new-space-exploration)
12. [Avi Loeb, Chair of the Breakthrough Starshot project, SciTech Europa Quarterly interview](https://lweb.cfa.harvard.edu/~loeb/Loeb_Starshot.pdf)
13. [The Breakthrough Starshot system model, Acta Astronautica](https://www.sciencedirect.com/science/article/pii/S0094576518310543)
14. [On the stability of a space vehicle riding on an intense laser beam, arXiv:1610.08043](https://arxiv.org/abs/1610.08043)
15. [Towards Stable Interstellar Flight: Levitation of a Laser-Propelled Sailcraft, arXiv:2203.14699](https://arxiv.org/abs/2203.14699)
16. [Multifunctional metasails for self-stabilized beam-riding and optical communication, Journal of the Optical Society of America](https://www.sciencedirect.com/org/science/article/pii/S2516023023025005)
17. [Calculations of Particle Bombardment due to Dust and Charged Particles in the ISM on the Project Starshot Gram-Scale Interstellar Probe, arXiv:2307.12160](https://arxiv.org/abs/2307.12160)
18. [Breakthrough Starshot: Wie das gewagteste Raumfahrtprojekt der Geschichte starb, Die Zeit (September 2025)](https://www.zeit.de/wissen/2025-09/breakthrough-starshot-forschung-raumfahrt-finanzierung)
19. [Can solar sails really send humans out into interstellar space?, Space.com (2025)](https://www.space.com/astronomy/can-solar-sails-really-send-humans-out-into-interstellar-space)
---
*Topic: Encyclopedia › Physical world and mathematics › Astronomy › Stars and galaxies › Nebulae and the interstellar medium › Interstellar medium, travel and communication › Interstellar travel concepts and probes*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license