Spacecraft Systems
Discussion of the design of the electronics subsystems operating onboard the spacecraft into two parts:
A Millennium of Operation
Even electronic components have a limited lifetime. Over the years of space travel, the wiring, active and reactive components and even the junctions in the spacecraft's microchips will slowly degrade and cease to work. This is unavoidable, and will be accelerated due to the the spacecraft being exposed to healthy doses of cosmic radiation throughout its journey. This however, can be lessened by proper shielding and careful temperature monitoring of all of the electronic subsystems and using hardware that is specifically designed for longevity rather than performance and macroeconomics.
Sufficient redundancy within our subsystems will ensure that the spacecraft has a good chance of remaining operational after centuries of use. It is important to note that auxiliary electronic components that are not powered have the highest chance of surviving the journey. For this reason, the spacecraft will be launched with large quantities of redundant circuitry that can be easily swapped into the system when an older component dies.
Another important aspect in the electronic systems design is the design of circuitry that is capable of partial operation. Systems are to be designed in such a way that they still maintain limited functionality even when part of the circuitry is damaged. Cosmic radiation for example can cause microprocessors to malfunction, resulting in potentially errant calculations. NASA has invested resources in designing hardware and software that allows microprocessors to work even while being bombarded by cosmic radiation1. Redundancy is used in hardware to provide multiple verifications for calculations, while software can be used to manage the hardware and use more or less hardware depending on the importance of the calculations. This will further improve the system's chances of survival.
Proper temperature control is also vital to the success of the mission. Heat must be transferred efficiently from the inside of the spacecraft outwards where it can be dissipated. In areas that are not oriented toward the sun, up to 300 Watts per square foot can be dissipated. Heat dissipation will always be a concern for the spacecraft, however, proper planning and contingency planning will allow the systems to remain functional.
From Dust and Harmful Radiation
Relativistic dust, or rather interstellar dust lying in the path of the moving spacecraft is a major source of concern for shielding the electronic subsystems. Deep space is populated by a non-negligaible number of tiny particles per cubic meter. Since the spacecraft is colliding with the dust at velocities significantly near the speed of light, the spacecraft's hull will slowly erode over time. Shielding the front and back end of the spacecraft where the majority of these collisions will occur is absolutely vital for the success of this mission.
Cosmic Radiation is another important factor in the design of the spacecraft's shielding. High-mass density materials, are actually not good choices for shielding the spacecraft and should be avoided as interaction with positive ions causes these materials to produce secondary radiation3. Hydrogen is effective at reducing neutron energies through a process called elastic scattering.
Aluminum has been commonly used as a shielding material in spacecraft design. However it is unfortunately relatively heavy. The Bound Vehicle however, will have shields constructed of Polyethylene, a material that has already being utilized in constructing the protective armor for helicopters. Polyethylene was chosen mainly for its lower weight and its high Hydrogen content, Hydrogen is known to be very effective at absorbing and dispersing radiation4.
Sensor systems
Bound will also carry the following sensor systems on-board:
All devices on board collect data autonomously. Because of the tremendously long distance it will be difficult to control devices from an earth station.