The conceptual principles to enable this interstellar travel project were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara. Sending the lightweight spacecraft involves a multi-kilometer phased array of beam-steerable lasers with a combined coherent power output of up to 100 GW.
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 CEO Mark Zuckerberg. The project has an initial funding of US$100 million to initialize research. 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.
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. Secondary goals are Solar System exploration and detection of Earth-crossing asteroids. The spacecraft would make a flyby of, and, possibly photograph any Earth-like worlds that might exist in the system.
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 (VLT) in Chile. This upgrade will increase the likelihood of planet detection in the system.
A solar sail concept
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 crafts' sails 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 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.
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. 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, hydrogen and galactic cosmic rays may not be as severe an engineering problem as first thought.
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. 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, 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. 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. According to The Economist, at least a dozen off-the-shelf technologies will need to improve by orders of magnitude.
In July 2017, scientists announced that precursors to Spaceprobe, called Sprites, were successfully launched and flown through Polar Satellite Launch Vehicle by ISRO from Satish Dhawan Space Centre. 105 Sprites were also flown to the ISS on the KickSat-2 mission that launched on November 17 2018, from where they were deployed on March 18, 2019. They successfully transmitted data before reentering the atmosphere and burning up on March 21.
Each Spaceprobe 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.
The light sail is envisioned to be no larger than 4 by 4 meters (13 by 13 feet), possibly of composite graphene-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
Laser communicator, utilizing light sail as the primary reflector, would be capable of data rates 2.6-15 baud per watt of transmitted power at distance to the Alpha Centauri, assuming 30m diameter receiving telescope on Earth.
Other potential destinations
The table below lists possible target stars for similar photogravitational assist travel. The travel times are for the spacecraft to travel to the star and then enter orbit around the star (using photon pressure in maneuvers similar to aerobraking).
^ abcdefghiOverbye, Dennis (12 April 2016). "Reaching for the Stars, Across 4.24 Light-Years; A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away". The New York Times. Retrieved 12 April 2016.
^Stone, Maddie (12 April 2016). "Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship". Gizmodo. Retrieved 12 April 2016.
^Staff (12 April 2016). "Breakthrough Initiatives – Breakthrough Starshot". Breakthrough Initiatives. Retrieved 14 April 2016.
^ abLubin, Philip (2016). "A Roadmap to Interstellar Flight". Journal of the British Interplanetary Society. 69: 40. arXiv:1604.01356. Bibcode:2016JBIS...69...40L.(file available at University of California, Santa Barbara here Archived 17 April 2016 at the Wayback Machine Accessed 16 April 2016)
^Hall, Loura (7 May 2015). "DEEP IN Directed Energy Propulsion for Interstellar Exploration". NASA News. Retrieved 22 April 2016. NASA is pleased to hear that Professor Lubin has received external funding to continue the work started in his NIAC study.
^"Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 25 December 2017.
^ ab"Breakthrough Starshot: Management and Advisory Committee".
^"Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 10 January 2017.
^Scharf, Caleb A. (26 April 2016). "Can Starshot Work?". Scientific American Blogs. Retrieved 25 August 2016.
^"Planet Found in Habitable Zone Around Nearest Star – Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri". www.eso.org. Retrieved 10 January 2017.
^Witze, Alexandra (25 August 2016). "Earth-sized planet around nearby star is astronomy dream come true". Nature. 536 (7617): 381–382. Bibcode:2016Natur.536..381W. doi:10.1038/nature.2016.20445. PMID27558041. S2CID 4405961.
^"VLT to Search for Planets in Alpha Centauri System". European Space Observatory (ESO). 9 January 2017. Retrieved 10 January 2017.
^"Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 10 January 2017.
^"Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 25 August 2016.
^ ab"Breakthrough Starshot: Concept". 12 April 2016. Retrieved 14 April 2016.
^ abcde"A new plan to send spacecraft to the stars: replace rockets with lasers". The Economist. 12 April 2016. Retrieved 13 April 2016.
^ abEmspak, Jesse (15 April 2016). "No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges". Space. Retrieved 15 April 2016.
^Hoang, Thiem; Lazarian, A.; Burkhart, Blakesley; Loeb, Abraham (2017). "The Interaction of Relativistic Spacecrafts [sic] with the Interstellar Medium". The Astrophysical Journal. 837 (1): 5. arXiv:1608.05284. Bibcode:2017ApJ...837....5H. doi:10.3847/1538-4357/aa5da6. S2CID 55427720.
^Timmer, John (24 August 2016). "Just how dangerous is it to travel at 20% the speed of light?". Science. Ars Technica. Retrieved 28 August 2016.
^"Potential Challenges for Starshot". Breakthrough Initiatives. Retrieved 14 April 2016.
^Andreas M. Hein, Kelvin F. Long, Dan Fries, Nikolaos Perakis, Angelo Genovese, Stefan Zeidler, Martin Langer, Richard Osborne, Rob Swinney, John Davies, Bill Cress, Marc Casson, Adrian Mann, Rachel Armstrong (2017). "The Andromeda Study: A Femto-Spacecraft Mission to Alpha Centauri". Initiative for Interstellar Studies. arXiv:1708.03556.CS1 maint: uses authors parameter (link)
^ abcGreene, Kate (13 April 2016). "What Will Make Interstellar Travel a Reality?". Slate. Retrieved 16 April 2016.
^ abcClery, Daniel (12 April 2016). "Russian billionaire unveils big plan to build tiny interstellar spacecraft". Science. doi:10.1126/science.aaf4115. Retrieved 15 April 2016.
^ abStone, Maddie (12 April 2016). "Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship". Gizmodo. Retrieved 12 April 2016.
^ abcDomonoske, Camila (12 April 2016). "Forget Starships: New Proposal Would Use 'Starchips' To Visit Alpha Centauri". NPR. Retrieved 15 April 2016.
^ abcdeEmspak, Jesse (15 April 2016). "No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges". Space.com. Retrieved 15 April 2016.
^Staff (26 July 2017). "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". BreakThroughInitiatives.org. Retrieved 28 July 2017.
^University, Stanford (3 June 2019). "Inexpensive chip-size satellites orbit Earth". Stanford News. Retrieved 3 June 2019.
^Tavares, Frank (30 May 2019). "What is KickSat-2?". NASA. Retrieved 5 June 2019.
^"Cracker-sized satellites demonstrate new space tech". Cornell Chronicle. Retrieved 5 June 2019.
^Heller, René; Hippke, Michael; Kervella, Pierre (2017). "Optimized trajectories to the nearest stars using lightweight high-velocity photon sails". The Astronomical Journal. 154 (3): 115. arXiv:1704.03871. Bibcode:2017AJ....154..115H. doi:10.3847/1538-3881/aa813f. S2CID 119070263.
^Gros, Claudius (2016), "Developing ecospheres on transiently habitable planets: The genesis project", Astrophysics and Space Science, 361 (10): 324, arXiv:1608.06087, Bibcode:2016Ap&SS.361..324G, doi:10.1007/s10509-016-2911-0, S2CID 6106567
^Boddy, Jessica (2016). "Q&A: Should we seed life on alien worlds?". Science. doi:10.1126/science.aah7285. ISSN 0036-8075.
^Romero, James (November 2017). "Should we seed life through the cosmos using laser-driven ships?". New Scientist. No. 3152.
Breakthrough Initiatives' official website
Video (00:35) – Launching a StarChip – concept on YouTube
Video (02:06) – Going interstellar (NASA) on YouTube
Video (12:16) – Will Starshot's Insterstellar Journey Succeed? (PBS Digital Studios) on YouTube