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. As the isotope decays it will charge the ultra-capacitor. Then, at the appropriate time, the StarChip components will be switched on and begin to operate. The power budget is informed by the available energy in the battery. An innovative approach could take advantage of the heating of the frontal surface of the nanocraft through its interaction with the interstellar medium. The heat supply, at a rate of 6mW per cm2, could provide a thermoelectric energy source during the interstellar cruising phase.

It may be possible to coat the lightsail with a thin film of photovoltaic material, which was demonstrated on the IKAROS mission. This could be extremely useful during approach to the host star. The photovoltaics will be able to supply significant energy when they are within 2AU of the target star. Even with just 10% efficient photovoltaics, the energy supplied would be nearly 2kW at 1AU. This is more than 100,000 times the power of the radioactive energy source, and could conceivably allow much higher data rates for laser communication. This is one option that will be explored.

Coating the StarChip itself with PV would allow for high efficiency, and potentially gain several Watts just from the StarChip. These options open up a host of possibilities to greatly enhance functionality at the host star in the crucial data and imaging phases.

Comments (38)

  1. Agustín Alemán González:

    Maybe, you should consider this University of Bristol Iniciative to encapsulate radioactive materials inside diamonds to produce a small current during very long periods of time (i.e., 5000 years). Details @



  2. Breakthrough Initiatives:

    "Dec 30, 2016 19:37 Agustín Alemán González Posted on: Breakthrough Initiatives
    Maybe, you should consider this University of Bristol Iniciative to encapsulate radioactive materials inside diamonds to produce a small current during very long periods of time (i.e., 5000 years). Details @


    Thank you for the link to “‘Diamond-age’ of power generation as nuclear batteries developed”. This is indeed an interesting read and relevant to the Initiatives.

    - Pete Klupar, Breakthrough Starshot

  3. Stuart Heinrich:

    In addition to coating the sail with PV, there has been some research showing that a pixel's photodiode can be used to not only measure the incident light level, but also to convert the incident light into electrical energy. This was used to prototype an "eternal camera":


    It might be a good idea to have some of the sail material or easily ionised material be impacted (sputtered off) by the ISM which will ionises it which we could then use to power our circuits, using the ISM as a power source would be of great value to the design.

  5. Breakthrough Initiatives:

    Apr 10, 2017 16:26 Stuart Heinrich Posted on: Breakthrough Initiatives

    That is a very cool camera idea. However, the amount of power generated by a such a camera would be much less than could be generated by a solar panel.

    – Zac Manchester, Breakthrough Initiatives

  6. Breakthrough Initiatives:

    Apr 29, 2017 07:45 Posted on: Centauri Dreams

    Using ISM collisions to provide power is a really cool idea that has been discussed by a few people. It might be possible to harness the heating caused by the collisions on the front of the spacecraft.

    – Zac Manchester, Breakthrough Initiatives

  7. Vittorio Palmieri:

    Hello, you mention that the electric power of the radioactive energy source is 100'000 less than 2kW or 20mW. Also the mass budget for the battery is 150mg including the supercapacitor.

    Now considering that Pu238 has a specific thermal power of about 0.5 W/g (, even assuming that the supercapacitor weights near to nothing, the thermal power from the 150mg radioisotope mass would be 75mW and the thermolectric conversion efficiency would be very high at 27%.

    Considering that thermoelectric efficiency is determined by temperature and figure of merit, which respective values have you considered?


  8. Breakthrough Initiatives:

    Oct 23, 2017 16:37 Vittorio Palmieri Posted on: Breakthrough Initiatives

    Thank you for your thoughts. The power conversion efficiency at these very low power levels are around 30 percent thus we must also consider the distribution losses.

    – Pete Klupar, Breakthrough Initiatives

Please sign in to be able to add new comments.