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Starship
U.S.S. T-Rex
33. 3BP Theory
X 0 1 2 3 4 5 6 7 8 |
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Starship |
| U.S.S. T-Rex |
| ___ |
| 33. 3BP Theory |
| 34. Light Barrier |
| 35. L-1011 Tristat |
| 36. Floor Plan |
| 37. Power |
| 38. Gravity |
| 39. A. I. |
| 40. Weapons |
| the book |
( TWO ) illustrates a powerful new computational technique. Virtually every computer program uses some type of numerical integration. In the Mars Pathfinder program, the equations of motion are solved (integrated) using a variable step Runge Kutta integrator.TAB 39
Artificial IntelligenceThe Mars trajectory computer program
The optimization algorithm was the integrator to determine neighboring optimal trajectories, making it possible to solve the problem very quickly and accurately. More specifically, the variable step integrator stops whenever all the conditions of the problems change enough to require a new integration calculation (i.e. the step size is varied to match the changing conditions, or forces acting on the spacecraft - close to a large body the steps are very small; far away they are large). Normally this decision must be made by the user, or done randomly; and many trials occur before arriving at a decision. The RK 7/8 makes this decision as part of the program algorithm itself, and using this decision instead of some elaborate, convoluted, artificial decision process is much faster and more efficient.
The gist of the argument is that using the RK 7/8 integrator to make the important decisions
( 10 ) not only makes the algorithm more efficient (replacing thousands of computer steps or lines of code, with a single command), more accurate (every computation involves a miniscule round off error, and the cumulative affect of thousands of such steps is great compared to a single step) and greatly compacts the code. That is, the thousand lines of code of Mars Pathfinder replaces a NASA program 100 times larger, finding a better result, faster, and on a much smaller computer - a PC versus a mainframe.This numerical method is ubiquitous in engineering analysis. Modifying hundreds of such programs will not only reduce the storage space by a factor of 100 or more, but make the routines easier to use and modify. Overall, a complex machine like a starship that could run hundreds of these programs at once - maybe thousands in battle conditions - simultaneously. With the vessel going so fast, needing to make critical decisions each and every instant, then the faster and more compact each routine, the better.
So, speed is critical. Storage space is also at a premium on a space craft. Power is another limiting factor for such a complex, massive computer system - reducing the size by a factor of 100, increases speed of the routine by a like proportion, as well as accuracy and dependability.