Self-repairing spacecrafts
NASA and CSIRO in Australia are working together to build future spacecrafts able to detect, diagnose and fix damage, whether inflicted by impacts or caused by equipment failures. The CSIRO team has developed a spacecraft skin based on the concept of a multi-cellular sensor and communication network. The current model is composed of 192 separate cells which can act as a reconfigurable network when a cell detects an impact and is using a software algorithm based on the ant colony metaphor. As writes New Scientist, "Ant logic makes sense in space." According to different documents from NASA, these nondestructive evaluation and health monitoring systems could be deployed by 2015, at least for some limited experiments in space.
Before going further, below is an image showing NASA's vision of "evaluation and repair robots fixing part of a futuristic space ship" (Credit: NASA's Langley Research Center, Nondestructive Evaluation Sciences Branch (NESB)).
But today's reality is far from this dream. Here is the current status of the project explained by New Scientist.
The team at CSIRO, Australia's national research organisation, is working with NASA on the project and has so far created a model skin made up of 192 separate cells. Behind each cell is an impact sensor and a processor equipped with algorithms that allow it to communicate only with its immediate neighbours. Just as ants secrete pheromones to help guide other ants to food, the CSIRO algorithms leave digital messages in cells around the system, indicating for instance the position of the boundary around a damaged region. The cell's processor can use this information to route data around the affected area.
Below is a computer screenshot showing how collections of cells may solve complex tasks, such as forming impact boundaries (Credit: CSIRO). Red and yellow cells indicate respectively major and minor damages to communications, while blue cells point to recoverable communication losses and white double lines show emergent impact boundaries.
As you can see, the current model is still pretty crude. And the different groups at CSIRO and NASA are exploring distributing systems which could survive to the destruction of the central processor. But this will take years.
For more information about the AAV concept at CSIRO, you can visit this page about the AAV application or this one about software simulation and multi-agent networks from where the image above was extracted.
The latest reseach work is being published by the journal Robotics and Autonomous Systems under the name "On connectivity of reconfigurable impact networks in ageless aerospace vehicles" (Volume 53, Issue 1, Pages 36-58, October 31, 2005). Here is a link to the abstract.
Finally, you might want to read two previous papers on this subject, "An Integrated Health Monitoring System for an Ageless Aerospace Vehicle" (PDF format, 8 pages, 309 KB) and "Self-organising Impact Boundaries in Ageless Aerospace Vehicles" (PDF format, 8 pages, 370 KB).
Sources: New Scientist, September 12, 2005; and various web sites
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