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.
Research:
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Eiting, C. J., et. al. “Demonstration of a radiation resistant, high efficiency SiC betavoltaic,” Applied Physics Letters, Vol. 88 no. 6 (2006)
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Chandrashekhar, M. V. S., Thomas, C. I., Li, H., Spencer, M. G., and Lal, A. “Demonstration of a 4H SiC betavoltaic cell,” Applied Physics Letters, Vol. 88, no. 3, pp. 1351-1354 (2006)
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Huang, P. et. al. “On-chip and freestanding elastic carbon films for micro-supercapacitors,” Science, Vol. 351, no. 6274, pp. 691-695 (2016)
Aug 01, 2016 13:46
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
In the vicinities of the Earth and of AC the solar sail could collect from about 20W (10 AU) to 2KW (1 AU) of power (see summary). It would take the nanosat about 14 hours to cover 20 AU near AC, thus enough time to transmit back to Earth.
A radioisotope power source would keep the nanosat in a safe, low functional mode during cruise, while possibly storing some energy in a battery.
Power is also imparted to the nanosat by the interstellar hydrogen (1 atom per cm3) in the form of 20 MeV protons and 10 keV electrons (see summary). The 15 nm solar sail does not stop either protons or electrons. 10keV electrons will stop in about 1μm of Al, while 20MeV protons will stop in 2 mm of Al (or 0.5 g/cm2).
The about 20mW power delivered by protons stopping in a 1 cm2 component, could be used to charge a storage device for periodic communications with Earth.
– Prof. Sasha Buchman, Breakthrough Initiatives
Aug 23, 2016 07:25
michael.million@sky.com
Posted on: Centauri Dreams
We might be able to use shallow angle deflection of ions and neutral particles by using two sheets of material that opens like a clam to guide particles into a central heating or electrical convertor region. Should be able to get a fair amount of power due to the kinetic energy of the sail.
Aug 26, 2016 11:15
william@theroses.me.uk
Posted on: Breakthrough Initiatives
Would it be possible to coat the front of the sail in ultralight piezoelectric crystals which would turn the pressure created by passing through the interstellar medium at high speed into electricity.
Sep 25, 2016 21:22
mh@markus-harder.de
Posted on: Breakthrough Initiatives
A power supply of 2kW on a mass of the order of one gram will rapidly heat up the mass, even if only a small fraction of this energy is effectively absorbed. A concept is needed to get rid of the excess energy to avoid overheating of the spacecraft.
Dr. Markus Harder
Sep 28, 2016 05:22
michael.million@sky.com
Posted on: Centauri Dreams
'A power supply of 2kW on a mass of the order of one gram will rapidly heat up the mass, even if only a small fraction of this energy is effectively absorbed. A concept is needed to get rid of the excess energy to avoid overheating of the spacecraft.
Dr. Markus Harder'
We could tilt the craft to absorb less energy over the area.
Oct 03, 2016 14:52
oren.watson@gmail.com
Posted on: Breakthrough Initiatives
I have envisioned a very small power source, to provide only every small amounts of power, for extreme spans of time.
Put two plates in a vacuum, such as space. Plate A would be an alpha particle emitter that is also conductive.
Plate B would be a suitable conductive material. The alpha particles emitted from one plate would hit the other and be slowed enough that they could take electrons from that plate. Hence over time plate B would become positively charged relative to plate A, by a small amount. With a small gap, the device would be a small self-charging capacitor.
Nov 05, 2016 03:02
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
RE:
"Oct 03, 2016 14:52 oren.watson@gmail.com Posted on: Breakthrough Initiatives
I have envisioned a very small power source, to provide only every small amounts of power, for extreme spans of time. Put two plates in a vacuum, such as space. Plate A would be an alpha particle emitter that is also conductive. Plate B would be a suitable conductive material. The alpha particles emitted from one plate would hit the other and be slowed enough that they could take electrons from that plate. Hence over time plate B would become positively charged relative to plate A, by a small amount. With a small gap, the device would be a small self-charging capacitor."
Answer:
We consider this a valid approach to generating power. We have considered using americium-241 as the alpha emitter. Many trades still need to be done to find the best way to generate power. There may be approaches that use the interstellar gas or solar wind as source of energy.
- Avi Loeb, Breakthrough Starshot
