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. The vehicle must operate during 4 distinct stages: in Earth orbit, in the solar system, cruising through deep space, and in the Alpha Centauri system. Each of these phases have significantly different environments that must be accounted for in the design of the nanocraft. The vehicle will have to be designed to operate from a range of 300 to a handful of degrees Kelvin. However, properly doped electronics have already operated over extreme temperature ranges for more than 30 years.
The onboard RTG battery could also be used to heat the entire StarChip or selective parts. For example, the StarChip could be self-heated to about 100-200 Kelvin or above - well within the range of doped silicon and other semiconductors.
The vehicle would only go through one thermal cycle. It is also intended to minimize the number of power cycles on the vehicles components. The StarChip would have a constant power source from the radio-isotope generator, which would both heat and electrically power it. Various approaches are currently being debated.
One concept envisions that the system would operate continuously for decades without being turned off, which would have the advantage of improving reliability. Another approach being considered is for the StarChip to operate only for a short period every six months. This would allow for a lighter, smaller craft with a lower power demand. Both these systems would employ a power source which trickles charges from an energy storage unit. This would supply peak power when needed - for instance during imaging, maneuvering with the photon thrusters, and the critical period of transmitting data back to Earth.
Information would be sent continuously from the moment the nanocraft leaves Earth until 3 days or so after launch, when it would be approximately 20 billion kilometers away (the distance Voyager 1 has travelled since its launch in 1977). Because significant numbers of nanocrafts could be sent, a variety of payloads might be carried. Besides taking images, some of them would measure and telemeter data about the ambient magnetic field, particle density and radiation environment, as well as taking images of outer solar system objects.
A challenge to maintaining operational integrity for 20 years is posed by the impact of interstellar and interplanetary dust, and erosion by the interstellar medium. Two approaches can be contemplated. First, significant redundancy in the design of the nanocraft, so that no single cosmic ray or dust particle will be a mission-ending event. Secondly, the addition of a protective coating around specific key components. A material such as beryllium copper is a leading candidate for this coating.
Although the requirements for are challenging, they are known, and a program of analysis, design and testing can be developed to ensure confidence in mission success prior to launch.
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