NSTAR xenon ion thruster on Deep Space 1: Ground and flight tests (invited)

After having been in development for many years at the Glenn Research Cente r (formerly the Lewis Research Center), the national aeronautics and space administration-designed, 30 cm, ring-cusp, xenon ion engine was launched on the Deep Space 1 (DS1) spacecraft on 24 Oct. 1998 from the Kennedy Space C enter in Florida. It has since accumulated 2200 h of in-space thrusting at input power levels ranging from 0.52 to 1.96 kW, has successfully enabled t he spacecraft to fly by the asteroid Braille in July 1999, and is now thrus ting DS1 along a trajectory towards its comet destinations in 2001. The des ign, assembly, test, integration, and operation of this thruster comprise a unique path of technical determination, artful design choices, persistent engineering and analysis, and mastery of vacuum chamber operations. The tes ting program over the development years, the assembly and integration perio ds, and the flight operational period thus far have shown that the project test philosophy of segregating effects against unique causes proved itself most useful. The 8000 h life test, the culmination of the pre-launch ground test plan, not only met its goals but surpassed them with margin. This art icle will explain the thruster test program from beginning to end, illustra ting the technical and programmatic decision making along the way. It will justify the use of engineering models as an inexpensive method of determini ng answers to key design questions and will explain why testing of the thru ster alone only solved a portion of the system operations task. The highlig ht of the test program proved to be the vacuum firing of the ion engine dur ing the spacecraft's solar thermal vacuum test. A comparison of the preflig ht data with postflight data shows that high confidence was warranted for e xecuting a successful flight to the asteroid and beyond. (C) 2000 American Institute of Physics. [S0034-6748(00)51402-6].