On 24 August 2016, ESO hosted a press conference to discuss the announcement of exoplanet Proxima b at its headquarters in Germany. In this picture, Pete Worden giving a speech.

Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named Starchip,[1] to be capable of making the journey to the Alpha Centauri star system 4.34 light-years away. It was founded in 2016 by Yuri Milner, Stephen Hawking, and Mark Zuckerberg.[2][3]

A flyby mission has been proposed to Proxima Centauri b, an Earth-sized exoplanet in the habitable zone of its host star, Proxima Centauri, in the Alpha Centauri system.[4] At a speed between 15% and 20% of the speed of light,[5][6][7][8] 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.[9][10] 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.[11]

General

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 Meta Platforms (then known as Facebook, Inc.) 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.[6] Pete Worden is the project's executive director and Harvard Professor Avi Loeb chairs the advisory board for the project.[12]

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 Alpha Centauri within the next generation.[13] 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.[14]

Target planet

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.[15][16] 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.[17][18] 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.

Concept

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.[19][20] An October 2017 presentation of the Starshot system model[21][22] 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.[23]

The fleet would have about 1000 spacecraft. Each one, called a StarChip, would be a very small centimeter-sized vehicle weighing a few grams.[1] They would be propelled by a square-kilometre array of 10 kW ground-based lasers with a combined output of up to 100 GW.[24][25] A swarm of about 1000 units would compensate for the losses caused by interstellar dust collisions en route to the target.[24][26] In a detailed study in 2016, Thiem Hoang and coauthors[27] 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.[28]

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 of thrust.[25] 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.[25][29] All components must be engineered to endure extreme acceleration, cold, vacuum, and protons.[26] 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.[25][30] 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.[31] 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.[32][33] 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 0.2C requires combining optics which are approximately 3 kilometers in diameter to focus the laser light on the sail. [34][35] This could be implemented using a phased array system which is being researched at The University of California Santa Barbara .[36][37] According to The Economist, at least a dozen off-the-shelf technologies will need to improve by orders of magnitude.[25]

StarChip

StarChip is the name used by Breakthrough Initiatives for a very small, centimeter-sized, gram-scale, interstellar spacecraft envisioned for the Breakthrough Starshot program,[1][38] 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.[39][6][40][5][41][42] The journey may include a flyby of Proxima Centauri b, an Earth-sized exoplanet that is in the habitable zone of its host star.[4] The ultra-light StarChip robotic nanocraft, fitted with light sails, are planned to travel at speeds of 20%[1][6][40][5] and 15%[5] 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.[6] The conceptual principles to enable practical interstellar travel were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara,[9] who is an advisor to the Starshot project.

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.[43] 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.[44][45][46][47]

Components

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.[1][38][39][6][41][42][48][49]

Cameras

Five sub-gram scale digital cameras, each with a minimum 2-megapixels resolution, are envisioned.[1][50]

Processors

Four sub-gram scale processors are planned.[41][51]

Photon thrusters

Four sub-gram scale photon thrusters, each minimally capable of performing at a 1W diode laser level, are planned.[38][52][53]

Battery

A 150 mg atomic battery, powered by plutonium-238 or americium-241, is planned.[6][42][54]

Protective coating

A coating, possibly made of beryllium copper, is planned to protect the nanocraft from dust collisions and atomic particle erosion.[42][55]

Light sail

The light sail is envisioned to be no larger than 4 by 4 meters (13 by 13 feet),[1][56] possibly of composite graphene-based material.[1][39][6][42][49][57] 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.[1][6][58] 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.[54]

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 per watt of transmitted power at the distance to Alpha Centauri, assuming a 30 m diameter receiving telescope on Earth.[59]

Orbit

The Starshot project is for fly-by missions, which pass the target at high velocity. Heller et al.[60] 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.[60] The travel times are the calculated times for an optimized spacecraft to travel to the star and then enter orbit around the star.

NameTravel time
(yr)		Distance
(ly)		Luminosity
(L☉)
Proxima Centauri1214.20.00005
α Centauri A101.254.361.52
α Centauri B147.584.360.50
Sirius A68.908.5824.20
Epsilon Eridani363.3510.500.50
Procyon A154.0611.446.94
Altair176.6716.6910.70
Vega167.3925.0250.05
Fomalhaut A221.3325.1316.67
Denebola325.5635.7814.66
Castor A341.3550.9849.85
  • 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 (σnom) 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 of unicellular microbes on otherwise only transiently habitable exoplanets.[61][62] 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.[63]

See also

  • Interstellar probe
    • Project Dragonfly – Feasibility study of a small laser-propelled interstellar probe
    • Project Daedalus – 1970s proposal for a large fusion powered unmanned interstellar probe
    • Project Icarus – 2009 project to update design of Project Daedalus
    • Project Longshot – Design for a 400 tonne nuclear pulse propelled uncrewed spacecraft to reach and orbit Alpha Centauri
    • 2069 Alpha Centauri mission – NASA concept for uncrewed probe - possibly a light sail
    • Starlight – UCSB study of fleet of small laser light sail interstellar probes
    • Starwisp – 1985 proposal for microwave sail flyby of a nearby star

References

  1. 1 2 3 4 5 6 7 8 9 Gilster, Paul (12 April 2016). "Breakthrough Starshot: Mission to Alpha Centauri". Centauri Dreams. Retrieved 14 April 2016.
  2. ↑ F, Jessica (14 April 2016). "Stephen Hawking, Mark Zuckerberg, Yuri Milner Launch $100M Space Project Called Breakthrough Starshot". Nature World News.
  3. ↑ Lee, Seung (13 April 2016). "Mark Zuckerberg Launches $100 Million Initiative To Send Tiny Space Probes To Explore Stars". Newsweek. Retrieved 29 July 2019.
  4. 1 2 Chang, Kenneth (24 August 2016). "One Star Over, a Planet That Might Be Another Earth". The New York Times. Retrieved 24 August 2016.
  5. 1 2 3 4 Staff (12 April 2016). "Breakthrough Starshot". Breakthrough Initiatives. Retrieved 12 April 2016.
  6. 1 2 3 4 5 6 7 8 9 Overbye, 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.
  7. ↑ Stone, Maddie (12 April 2016). "Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship". Gizmodo. Retrieved 12 April 2016.
  8. ↑ Staff (12 April 2016). "Breakthrough Initiatives – Breakthrough Starshot". Breakthrough Initiatives. Retrieved 14 April 2016.
  9. 1 2 Lubin, Philip (2016). "A Roadmap to Interstellar Flight". Journal of the British Interplanetary Society. 69: 40. arXiv:1604.01356. Bibcode:2016JBIS...69...40L. Archived from the original on 15 May 2021. Retrieved 17 September 2017.(file available at University of California, Santa Barbara here Archived 17 April 2016 at the Wayback Machine Accessed 16 April 2016)
  10. ↑ 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.
  11. ↑ "Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 25 December 2017.
  12. ↑ "Breakthrough Starshot: Management and Advisory Committee".
  13. ↑ "Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 10 January 2017.
  14. ↑ Scharf, Caleb A. (26 April 2016). "Can Starshot Work?". Scientific American Blogs. Retrieved 25 August 2016.
  15. ↑ "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.
  16. ↑ 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. PMID 27558041. S2CID 4405961.
  17. ↑ "VLT to Search for Planets in Alpha Centauri System". European Space Observatory (ESO). 9 January 2017. Retrieved 10 January 2017.
  18. ↑ "Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 10 January 2017.
  19. ↑ Lightsail, Integrity under thrust.
  20. ↑ Lightsail | Stability on the beam.
  21. ↑ 2. Breakthrough Starshot System Model, 20 October 2017, retrieved 29 October 2017
  22. ↑ Parkin, Kevin. "Starshot System Model".
  23. ↑ "Breakthrough Initiatives". breakthroughinitiatives.org. Retrieved 25 August 2016.
  24. 1 2 "Breakthrough Starshot: Concept". 12 April 2016. Retrieved 14 April 2016.
  25. 1 2 3 4 5 "A new plan to send spacecraft to the stars: replace rockets with lasers". The Economist. 12 April 2016. Retrieved 13 April 2016.
  26. 1 2 Emspak, Jesse (15 April 2016). "No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges". Space. Retrieved 15 April 2016.
  27. ↑ Hoang; Lazarian, A.; Burkhart, Blakesley; Loeb, Abraham (2017). "The Interaction of Relativistic Spacecrafts 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.
  28. ↑ 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.
  29. ↑ "Potential Challenges for Starshot". Breakthrough Initiatives. Retrieved 14 April 2016.
  30. ↑ "Interstellar Dust". Breakthrough Initiatives. Retrieved 15 April 2016.
  31. ↑ 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.
  32. ↑ Paschotta, Dr Rüdiger. "Coherent beam combining". www.rp-photonics.com. Retrieved 5 January 2024.
  33. ↑ "Resolving power". labman.phys.utk.edu. Retrieved 5 January 2024.
  34. ↑ "Diffraction-limited system", Wikipedia, 5 December 2023, retrieved 5 January 2024
  35. ↑ "Acceleration", Wikipedia, 20 November 2023, retrieved 5 January 2024
  36. ↑ "Starlight". Retrieved 6 January 2024.
  37. ↑ Large Scale Directed Energy for Relativistic Flight, retrieved 6 January 2024
  38. 1 2 3 Greene, Kate (13 April 2016). "What Will Make Interstellar Travel a Reality?". Slate. Retrieved 16 April 2016.
  39. 1 2 3 Clery, Daniel (12 April 2016). "Russian billionaire unveils big plan to build tiny interstellar spacecraft". Science. doi:10.1126/science.aaf4115. Retrieved 15 April 2016.
  40. 1 2 Stone, Maddie (12 April 2016). "Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship". Gizmodo. Retrieved 12 April 2016.
  41. 1 2 3 Domonoske, Camila (12 April 2016). "Forget Starships: New Proposal Would Use 'Starchips' To Visit Alpha Centauri". NPR. Retrieved 15 April 2016.
  42. 1 2 3 4 5 Emspak, Jesse (15 April 2016). "No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges". Space.com. Retrieved 15 April 2016.
  43. ↑ 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.
  44. ↑ University, Stanford (3 June 2019). "Inexpensive chip-size satellites orbit Earth". Stanford News. Retrieved 3 June 2019.
  45. ↑ Tavares, Frank (30 May 2019). "What is KickSat-2?". NASA. Retrieved 5 June 2019.
  46. ↑ "Cracker-sized satellites demonstrate new space tech". Cornell Chronicle. Retrieved 5 June 2019.
  47. ↑ "KickSat-2 project launches 105 cracker-sized satellites". TechCrunch. 4 June 2019. Retrieved 5 June 2019.
  48. ↑ Staff (12 April 2016). "Breakthrough Starshot: Potential Challenges". Breakthrough Initiatives. Retrieved 14 April 2016.
  49. 1 2 Staff (16 April 2016). "Starship enterprise". The Economist. Retrieved 15 April 2016.
  50. ↑ Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Cameras". Breakthrough Initiatives. Retrieved 15 April 2016.
  51. ↑ Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Processors". Breakthrough Initiatives. Retrieved 15 April 2016.
  52. ↑ Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – 4 Photon Thrusters". Breakthrough Initiatives. Retrieved 15 April 2016.
  53. ↑ Gilster, Paul (21 October 2013). "Laser Travel by Photonic Thruster". Centauri Dreams. Retrieved 16 April 2016.
  54. 1 2 Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – Battery". Breakthrough Initiatives. Retrieved 15 April 2016.
  55. ↑ Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – Protective Coating". Breakthrough Initiatives. Retrieved 15 April 2016.
  56. ↑ Staff (12 April 2016). "Breakthrough Starshot: Lightsail, Integrity under thrust". Breakthrough Initiatives. Retrieved 16 April 2016.
  57. ↑ Staff (12 April 2016). "Breakthrouth Starshot: Gram-Scale Starchip Components – Lightsail – Structure". Breakthrough Initiatives. Retrieved 15 April 2016.
  58. ↑ Patel, Neel V. (15 April 2016). "The Starshot Breakthrough Light Beam Is Really a Million Lasers, Which Is Insane". Inverse. Retrieved 16 April 2016.
  59. ↑ Parkin, Kevin L. G. (2020). "A Starshot Communication Downlink". arXiv:2005.08940 [astro-ph.IM].
  60. 1 2 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.
  61. ↑ 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
  62. ↑ Boddy, Jessica (2016). "Q&A: Should we seed life on alien worlds?". Science. doi:10.1126/science.aah7285. ISSN 0036-8075.
  63. ↑ Romero, James (November 2017). "Should we seed life through the cosmos using laser-driven ships?". New Scientist. No. 3152.


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