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Star Cores: Computers in space

Posted on 3 Sep 2008 at 14:26

With these challenges in mind, it's no surprise that software is designed in-house, and with the same obsessively detailed care and attention paid to hardware development. Each line of code is tested and re-tested, requiring multiple sign-offs before it's accepted as bug-free. The cost of failure doesn't bear thinking about: the Ariane 5 rocket's voyage lasted only 37 seconds before the software system crashed due to an error-handling element in the code not being enabled. The result? The $370 million-project ended in a ball of fire.

Boldly going...

As the nature of space missions becomes more specialised, the demands placed on the software on board increases. The Phoenix Mars Lander is a case in point. "The software running the RAD6000 was responsible for navigating the spacecraft from Earth to Mars," Scuderi said. "The same computer was used for the landing process. Once on the ground, that same software evolves into a science lab, where all of the scoops of dirt collected by the robotic scoop are collected, placed in containers and analysed. All elements of this computer can be reprogrammed depending on need."

Such adaptability is likely to become increasingly important. In 1975, CC Kraft Jr observed: "Virtually every online, direct access, commercial computer system in the world reflects to some degree the space guidance and checkout requirements of some years ago." Now that situation is being reversed. The commercial sector's hunger for more energy-efficient processors and components means the space programme can now benefit from some of the power we take for granted in our PCs.

Some added: "The future of space computing is, in my view, likely to see high-performance multi-core machines based on commercial off-the-shelf components being used to implement parallel-processing clusters used as on-board computer servers for processing science data and to support autonomous operations.

"Missions being planned [even now] need significantly higher processing throughput than can be provided by radiation-hardened computers currently available or planned in the near future. The use of commercial state-of-the-art processing chips in fault-tolerant hardware/software architectures is a strategy that has the potential to meet these needs, has been in development for some time and should be ready for flight in the near future."

Scuderi gives an example of how companies such as BAE Systems are meeting this need with a new type of memory. "There are no hard drives that will survive 15 years in space," he said. "We are working with technology partner Ovonyx on a phase-change material called chalcogenide - the same material used on read/write CDs and DVDs. A small laser is used to heat up this material, and changes from a solid state to a crystalline state, so it's a basic binary sequence. We have taken this stuff and created C-RAM, which is non-volatile and non-destructive. So, in cases where programs are uploaded and changed as a space mission progresses, previous elements can be retained and stored, to be restored later. C-RAM is being looked into for future missions to Jupiter."

In the meantime, the likes of the Phoenix Mars Lander will continue to provide groundbreaking data and images from space. Designers of the Apollo spacecraft felt the on-board computer was so important it was virtually a "fourth crew member"; today, the computer is, arguably, the most important crew member of all.

Author: Martin James