Challenges

The nanocraft concept, combining light beamer, lightsail and StarChip, is by far the most plausible system for launching a realistic mission to Alpha Centauri within a generation. The key elements of the proposed system design are based on technology either already available or likely to be attainable in the near future under reasonable assumptions.

No ‘dealbreakers’ have been identified by the team of expert scientists and engineers leading the program.

As with any ‘moonshot’, however, there are major engineering challenges to be overcome. It is hoped that addressing them will not only open a path to the stars, but will also spur innovation and new frontiers of exploration.

Below are listed the most significant challenges identified so far for a light-propelled nanocraft mission, along with the areas of research and development that could provide solutions to them.

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  • Gram-scale StarChip components | 4 photon thrusters

    Sub-gram scale 1W diode lasers are currently widely available at very low costs. The manufacturing trend has seen power double for the same mass every two years. It is anticipated this trend will continue for these devices for some time. More...

    Comments: 33. Last comment by Monroe Pattillo – Aug 25, 2016 15:44.

  • Gram-scale StarChip components | 4 cameras

    Sub-gram-scale 2 megapixel cameras are currently widely available at very low costs. The trend has been a doubling of pixels for the same mass every two years. More...

    Comments: 9. Last comment by Kenneth Olive – Aug 24, 2016 22:37.

  • Gram-scale StarChip components | 4 processors

    Sub-gram scale microprocessors are currently widely available at very low costs. The trend has been a doubling of processor count for the same mass every two years. It is anticipated that these devices will continue this trend for some time. More...

    Comments: 12. Last comment by Breakthrough Initiatives – Aug 01, 2016 13:44.

  • Gram-scale StarChip components | Battery

    Battery design is one of the most challenging aspects of the mission. Currently under consideration for the energy source onboard are plutonium-238, which is in common use, or Americium-241. 150mg has been allocated for the mass of the battery. This includes the mass of the radioisotope and the ultra-capacitor. More...

    Comments: 24. Last comment by william@theroses.me.uk – Aug 26, 2016 11:15.

  • Gram-scale StarChip components | Power management

    The power available needs to be balanced with the tasks that need to be completed on the nanocrafts. The radioisotope power sources establish the power budget in the most conservative design. More...

    Comments: 3. Last comment by Breakthrough Initiatives – Aug 01, 2016 13:47.

  • Gram-scale StarChip components | Protective coating

    A protective coating is required for the dust collisions and the erosions caused by atomic particles in the interstellar medium. More...

    Comments: 18. Last comment by michael.million@sky.com – Aug 05, 2016 06:59.

  • Lightsail | Integrity under thrust

    To inform the study, a beamer in the 100 GW class was considered. If, for example, 10-5 of the energy is absorbed by a 4mx4m sail, it will be heated by about 60kW per m2, which is roughly 60 times more than sunlight illumination on Earth. This will heat the material but not melt it. More...

    Comments: 26. Last comment by Markus Hlusiak – Aug 28, 2016 06:41.

  • Lightsail | Structure

    Building a skeleton structure that will be able to hold the sail in shape during launch, be resilient to the interaction with the interstellar medium and potentially be able to modify the shape of the sail, is a major challenge given the gram-scale mass constraint. More...

    Comments: 22. Last comment by michael.million@sky.com – Aug 26, 2016 15:08.

  • Lightsail | Stability on the beam

    Beam shape and lightsail structure should be optimized for stability during the launch phase. In this period, on the order of 10 minutes, an illumination energy of order 1TJ is delivered to the sail. More...

    Comments: 14. Last comment by Denny Johansson – Aug 26, 2016 12:14.

  • Light Beamer | Cost

    The estimated cost of the laser array is based on extrapolation from the past two decades, and the prospects of mass production to reduce the associated cost. More...

    Comments: 19. Last comment by Adam Skrodzki – Aug 26, 2016 11:51.

  • Light Beamer | Phase

    In order to test the feasibility of the system, the case of a meter-scale sail was examined. For example, to focus the light beam on a 4mX4m sail across an acceleration distance of 2x106 km requires a focusing angle of 2 nano-radians (0.4 milliarcseconds), which is the diffraction limit for a kilometer-scale light beamer operating at a wavelength of 1 micron. More...

    Comments: 14. Last comment by Joe Hale – Aug 24, 2016 22:26.

  • Light Beamer | Atmosphere

    The atmosphere introduces two effects: absorption (or ‘reduction of transmission from unity’), and loss of beam quality (or ‘blurring of the beam spot’). The transmission of the atmosphere at a wavelength of 1 micron is extremely good, exceeding 90% at high altitude ground-based sites. More...

    Comments: 27. Last comment by Alberto Rabell – Aug 24, 2016 22:18.

  • Launch Site | Power Generation and Storage

    Power generation and storage at the launch site is challenge. Developing a site with adequate infrastructure to generate the energy at a high altitude site is difficult. More...

    Comments: 26. Last comment by Markus Hlusiak – Aug 28, 2016 08:55.

  • Launch | Precision pointing for a meter-scale lightsail

    The light beamer must focus a spot smaller than the sail onto the sail, as it orbits 60,000km above the Earth’s surface. More...

    Comments: 5. Last comment by Breakthrough Initiatives – Jul 23, 2016 21:19.

  • Launch | Keeping beam pointed on meter-scale lightsail

    There are a number of effects that make this task difficult. These include beam instabilities, laser mode issues, differential forces on the sail, differential heating of the sail, and instabilities in the atmosphere induced by the energy of the beam. More...

    Comments: 6. Last comment by Joe Hale – Aug 26, 2016 23:05.

  • Launch | Precisely determining orbital position of an exoplanet

    In order to bring a nanocraft to within 1AU of a planet in a system like Alpha Centauri, accurate locations of all the bodies near the path of flight would be required. More...

    Comments: 2. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:33.

  • Launch | Cooling the light beamer

    The most challenging element in terms of cooling the laser array system would be the small optical instruments in front of the primary mirror. This would be addressed with conventional cooling systems and possibly by cooling the beam director assemblies (lens assemblies). More...

    Comments: 3. Last comment by michael.million@sky.com – Jul 25, 2016 10:58.

  • Launch | Range safety and objects in beam path

    The radiative flux on an object such as a bird, airplane, or spacecraft moving through the beam would be about the same as the output energy flux at the beamer, or 100 kw/m2 – about two orders of magnitude above sunlight on Earth. More...

    Comments: 5. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:40.

  • Launch | Range safety and space debris

    Space debris is a serious challenge, both for detection and mitigation. More...

    Comments: 2. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:42.

  • Launch | Potential collision of nanocraft with planet

    Breakthrough Starshot has no intention of colliding any nanocraft with any object in space. Even though an accidental collision between a nanocraft and another object is a remote possibility happens, the resulting effects must still to be examined. More...

    Comments: 11. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:44.

  • Cruise | Interstellar dust

    Based on estimates of the density of dust in the local interstellar medium, over the course of a journey to Alpha Centauri each square centimeter of the frontal cross-sectional area of the StarChip and lightsail would encounter about 1,000 impacts from dust particles of size 0.1 micron and larger. However, there is only a 10% probability of a collision with a 1 micron particle, and a negligible probability of impact with much larger particles. More...

    Comments: 15. Last comment by william@theroses.me.uk – Aug 26, 2016 11:43.

  • Cruise | Interplanetary dust

    Since the trajectory to Alpha Centauri would take the nanocrafts away from the ecliptic plane of the solar system, there would be much less impact from solar system dust than from interstellar dust. Little is currently known about the dust content in the Alpha Centauri star system. More...

    Comments: 5. Last comment by william@theroses.me.uk – Aug 26, 2016 11:39.

  • Cruise | Interstellar medium and cosmic rays

    The mean free path and Larmor radius of interstellar plasma particles is far greater than the size of the nanocraft, meaning that they would impact the nanocraft walls independently rather than forming a bow shock. More...

    Comments: 12. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:55.

  • Cruise | Maintaining functionality over decades in space

    The voyage from earth to our nearest neighbor, at up to 20% of the speed of light, takes about 20 years. Maintaining the functioning of a sophisticated nanocraft through the rigors of deep space over this time is a challenging task. More...

    Comments: 2. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:58.

  • Flyby | Pointing camera at target planet

    During an encounter with an exoplanet, the nanocraft’s camera would need to rotate in order to image the target. More...

    Comments: 7. Last comment by Breakthrough Initiatives – Jul 23, 2016 21:22.

  • Communication | Pointing transmitter towards earth

    Finding the Earth should be reasonably straightforward, given its proximity to the Sun, which would be bright from the vantage of Alpha Centauri. The on-board star tracker would also be useful, as would locking onto the Starshot laser system. More...

    Comments: 4. Last comment by Nicola Petts (nee Waite) – Aug 24, 2016 19:17.

  • Communication | Sending images with laser using sail as antenna

    Images of the target planet could be transmitted by a 1Watt laser onboard the nanocraft, in a ‘burst mode’ which uses the energy storage unit to rapidly draw power for the power-intensive laser communications mode. Upon approach to the target, the sail would be used to focus the laser communication signal. More...

    Comments: 24. Last comment by Carl Hinton – Jun 15, 2016 09:57.

  • Communication | Receiving images with light beamer array

    Recent advances by groups at MIL Lincoln Labs and the Jet Propulsion Laboratory have demonstrated that it is possible to detect single photons emitted by lasers from very large distances. More...

    Comments: 14. Last comment by Breakthrough Initiatives – Jul 25, 2016 02:36.

  • Policy | Light beamer and relativistic-speed nanocrafts

    Clearance for launches will be required from all the appropriate government and international organizations. More...

    Comments: 14. Last comment by benedictrodgers@hotmail.com – Aug 27, 2016 19:08.