Breakthrough Starshot is a research and engineering project by Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft, named StarChip, capable of making the journey to the Alpha Centauri star system, 4.37 light-years away, at speeds between 15% and 20% of the speed of light, taking between 30 and 20 years to get there respectively, and about 4 years to notify Earth of a successful arrival. The journey may include a flyby of Proxima Centauri b, an Earth-sized exoplanet that is in the habitable zone of its host star in the Alpha Centauri system. 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 square-kilometer of 10 kW lasers, operating as a phased array. This is needed for the spot size to fit the sail size at long range, so that the duration of the push is sufficiently long to reach these velocities. Getting sufficiently large effective aperture with one big laser would be impractical.
The project was announced on 12 April 2016 in an event held in New York City by physicist and venture capitalist Yuri Milner and cosmologist Stephen Hawking who is 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 start research. Milner places the final mission cost at $5–10 billion, and estimates the first craft could launch around 2036. Pete Worden is the project's executive director.
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."
The Breakthrough Starshot program aims to demonstrate 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.
Breakthrough Starshot is a proof of concept mission to send a fleet of ultra-fast light-driven nanocraft to fly by a planet in a nearby star system, which could pave the way for a first launch within the next generation. An objective of the mission would be to make a fly-by of and possibly photograph any Earth-like worlds that might exist in the system.
In August 2016, the European Southern Observatory 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 (ESO) entered a collaboration to enable and implement a 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.
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, 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 has been 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. Each spacecraft would transmit data back to Earth using a compact on-board laser communications system using its solar sail as an antenna and the propulsion array as the receiver. A swarm of about 1000 units would compensate for the losses caused by interstellar dust collisions en route to the target. In a recent detailed study, 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.
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. 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, 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 nanocrafts, 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.
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.
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.
Reference interstellar travel catalog to use photogravitational assists for a full stop.Edit
Possible target stars for photogravitational assist travel:
|α Centauri A||20||4.36||1.52|
|α Centauri B||20||4.36||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)
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.
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NASA is pleased to hear that Professor Lubin has received external funding to continue the work started in his NIAC study.
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