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 spacecraft named StarChip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away.
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. At a speed between 15% and 20% of the speed of light,
it would take between twenty and thirty years to complete the journey,
and approximately four 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. 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.
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 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 Professor Avi Loeb (Harvard University) chairs the Advisory Board for the project.
In 2017 Stephen Hawking told the audience at Starmus Festival:
Our physical resources are being drained at an alarming rate. We have given our planet the disastrous gift of climate change. Rising temperatures, reduction of the polar ice caps, deforestation and decimation of animal species. We can be an ignorant, unthinking lot. We are running out of space and the only places to go to are other worlds. It is time to explore other solar systems. Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth.
Leaders
Management and Advisory Committee:
- Pete Worden, Executive Director, Breakthrough Starshot; former Director of NASA Ames Research Center
- Avi Loeb, Chairman, Breakthrough Starshot Advisory Committee; Harvard University
- Jim Benford, Microwave Sciences
- Steven Chu, Nobel Prize winner, Stanford University
- Bruce Draine, Princeton University
- Ann Druyan, Cosmos Studios
- Freeman Dyson, Princeton Institute of Advanced Study
- Lou Friedman, Planetary Society, JPL
- Robert Fugate, Arctelum, LLC, New Mexico Tech
- Giancarlo Genta, Polytechnic University of Turin
- Olivier Guyon, University of Arizona
- Mae Jemison, 100 Year Starship
- Joan Johnson-Freese, US Naval War College
- Pete Klupar, Director of Engineering, Breakthrough Starshot; former Director of Engineering, NASA Ames Research Center
- Jeff Kuhn, University of Hawaii Institute for Astronomy
- Geoff Landis, SA Glenn Research Center
- Kelvin Long, Journal of the British Interplanetary Society
- Greg Matloff, New York City College of Technology
- Claire Max, University of California, Santa Cruz
- Kaya Nobuyuki, Kobe University
- Kevin Parkin, Parkin Research
- Mason Peck, Cornell University
- Saul Perlmutter, Nobel Prize winner, Breakthrough Prize winner, UC Berkeley and Lawrence Berkeley National Laboratory
- Martin Rees, Astronomer Royal
- Roald Sagdeev, University of Maryland
- Ed Turner, Princeton University, NAOJ
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. 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.
Target planet
In August 2016, the European Southern Observatory (ESO) announced the detection of a planet orbiting the third star in the Alpha Centauri system, Proxima Centauri. The planet, called Proxima Centauri b,
is orbiting within the habitable zone of its star, and it could be a
potential target for one of the projects of Breakthrough Initiatives.
In January 2017, Breakthrough Initiatives and the European Southern Observatory entered a collaboration 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 greatly increase the likelihood of planet detection in the system.
Concept
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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 and then deploying them. 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 examines circular sails and finds that the beam director capital cost is minimized by having a sail diameter of 5 meters.
Earth-size planet Proxima Centauri b was discovered in 2016 orbiting within the Alpha Centauri system habitable zones, compelling the Breakthrough Starshot to try to aim its spacecraft within 1 astronomical unit
(150 million kilometers or 93 million miles) of it. From this distance,
a craft's cameras could potentially capture an image of high enough
quality to resolve surface features.
The fleet would have about 1000 spacecraft, and each one (dubbed 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 coworkers found that mitigating the collisions with dust, hydrogen and galactic cosmic rays may not be quite as severe an engineering problem as first thought.
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.
The spaceship will compensate for the low thrust by having a mass of
only a few grams. The camera, computer, communications laser, a plutonium 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.
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, a proposed mission to propel a fleet of a thousand StarChips on a journey to the Alpha Centauri star system, the nearest extrasolar stars, about 4.37 light-years from Earth. 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 lightsails, 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 for the Starshot project.
In July 2017, scientists announced that precursors to StarChip, named Sprites, were successfully launched and flown through Polar Satellite Launch Vehicle by ISRO from Satish Dhawan Space Centre. Sprites will also be flown on the KickSat-2 mission scheduled for November 2018.
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 lightsail, made of lightweight materials, with a gram-scale mass.
Cameras
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 laser level, are planned.
Battery
Protective coating
A coating, possibly made of beryllium copper, is planned to protect the nanocraft from dust collisions and atomic particle erosion.
Lightsail
The lightsail 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.
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).
| Name | Travel time (yr) |
Distance (ly) |
Luminosity (L☉) |
|---|---|---|---|
| Proxima Centauri | 121 | 4.2 | 0.00005 |
| α Centauri A | 101.25 | 4.36 | 1.52 |
| α Centauri B | 147.58 | 4.36 | 0.50 |
| Sirius A | 68.90 | 8.58 | 24.20 |
| Procyon A | 154.06 | 11.44 | 6.94 |
| Vega | 167.39 | 25.02 | 50.05 |
| Altair | 176.67 | 16.69 | 10.70 |
| Fomalhaut A | 221.33 | 25.13 | 16.67 |
| Denebola | 325.56 | 35.78 | 14.66 |
| Castor A | 341.35 | 50.98 | 49.85 |
| Epsilon Eridani | 363.35 | 10.50 | 0.50 |
- Successive assists at α Cen A and B could allow travel times to 75 yr to both stars.
- Lightsail 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 Lightsail, 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 utilized in a second step to establish a biosphere of unicellular microbes on otherwise only transiently habitable exoplanets. A Genesis probe would travel at lower speeds, about 0.3% of the speed of light. It could hence be decelerated using a magnetic sail.
