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UltraFlex 175

>> Background

Mars '01 Lander with Ultraflex Solar Arrays.
A typical application for the UltraFlex 175 would be similar to the Mars '01 Lander.

Past interplanetary spacecraft have required from 300 to 10,000 Watts of electrical power to supply all the computers, radio transmitters and receivers, motors, valves, data storage devices, instruments, hosts of sensors, and other devices. But now, with solar ion propulsion a proven technology (validated on the New Millennium Program's Deep Space 1 mission and used to propel the DAWN spacecraft to visit two asteroids), many future missions will need considerably more electrical power to take advantage of the low but steady acceleration provided by ion propulsion.

Ion propulsion involves ionizing a gas to propel a craft. Instead of a spacecraft being propelled with standard chemicals, the gas xenon (which is inert like neon or helium, but heavier) is given an electrical charge, or ionized. It is then electrically accelerated to a speed of about 30 km/second. When xenon ions are emitted at such high speed as exhaust from a spacecraft, they push the spacecraft in the opposite direction.

Diagram of ion engine
Ion propulsion will be commonly used in future spacecraft and will require a considerable and continuous supply of electrical power.

Ion propulsion requires a considerable power supply to keep a continuous electrical charge on the gas and to charge the grid through which the ions are expelled.

Choices of technology to meet these power requirements are today limited mainly to large scaled-up solar photovoltaic arrays. In the future, new sources, such as high-power nuclear technology will be needed for missions where the sunlight is too faint to generate enough power.

As the term suggests, photovoltaic materials have the ability to convert light directly to electricity. Individual photovoltaic, or solar, cells are affixed to some sort of panels or arrays that can be pointed toward the Sun.

Because the power output is directly proportional to surface area exposed to the Sun, solar arrays need to be larger if they are to produce additional power. The design challenges for large solar arrays are to make them lightweight, deployable, stowable in a small space for launch, and strong. They must also be able to point at an optimum angle to the Sun, though they may be off-pointed slightly for periods when it may be desirable to generate less power.


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