The Deep Space 1 and Dawn used the NSTAR, a solar-powered electrostatic ion propulsion engine

The NASA Solar Technology Application Readiness (NSTAR) is a type of spacecraft ion thruster called electrostatic ion thruster.[1][2] It is a highly efficient low-thrust spacecraft propulsion running on electrical power generated by solar arrays. It uses high-voltage electrodes (including two fine grids) to accelerate ions with electrostatic forces.

Development and performance

Diagram of a generic gridded electrostatic ion thruster

The purpose of NSTAR program was to develop a xenon-fueled ion propulsion system for deep space missions.[3] The NSTAR electrostatic ion thruster was developed at NASA's Glenn Research Center and manufactured by Hughes, and Spectrum Astro, Inc. in the early 1990s. The feed system development was a collaborative effort between JPL and Moog Inc.[1]

The ions are accelerated through two fine grids with roughly a 1300 V difference between them for 2.3 kW operation,[4][5] with a thrust of 20-92 mN, a specific impulse of 19000-30500 N·s/kg (1950-3100 s) and a total impulse capability of 2.65 x106 Ns on DS1.[5]

In 1996, the prototype engine endured 8000 hours of continuous operation in a vacuum chamber that simulates conditions of outer space. The results of the prototyping were used to define the design of flight hardware that was built for Deep Space 1 probe. One of the challenges was developing a compact and light weight power processing unit[6] that converts power from the solar arrays into the voltages needed by the engine.[3]

Performance

The engine achieves a specific impulse of up to three thousand seconds. This is an order of magnitude higher than traditional space propulsion methods, resulting in a mass savings of approximately half. Although the engine produces just 92 millinewtons (0.331 ounce-force) thrust at maximum power (2,100W on DS1 mission), the craft achieved high speed because ion engines thrust continuously for long periods of time.[7] "The 30-cm ion thruster operates over a 0.5 kW to 2.3 kW input power range providing thrust from 19 mN to 92 mN. The specific impulse ranges from 1900 s at 0.5 kW to 3100 s at 2.3 kW."[1]

Applications

Deep Space

The NSTAR ion thruster was first used on the Deep Space 1 (DS1) spacecraft, launched on 24 October 1998.[8] The Deep Space mission carried out a flyby of asteroid 9969 Braille and Comet Borrelly. Deep Space 1 had 178 pounds (81 kilograms) of xenon propellant, with a total impulse capability of 2.65 x106 Ns[5] and was capable of increasing the speed of DS1 by 7900 miles per hour (12,700 kilometers per hour, 3.58 km/s) over the course of the mission.[3] It used 2.3 kW of electrical power and was the primary propulsion for the probe.[4]

Dawn

The second interplanetary mission using NSTAR engine was the Dawn spacecraft, launched in 2007 with three redundant units[9] with a 30 cm diameter each.[6][10] Dawn is the first NASA exploratory mission to use ion propulsion to enter and leave more than one orbit.[11] Dawn carried 425 kg (937 lb) of on-board xenon propellant, and was able to perform a velocity change of 25,700 mph (11.49 km/s) over the mission.

Proposed uses

As of 2009 NASA engineers state that NSTAR engines, in the 5-kilowatt and 0.04 pound-thrust range, are candidates for propelling spacecraft to Europa, Pluto, and other small bodies in deep space.[1]

See also

References

  1. ^ a b c d "NASA Solar Electric Propulsion Technology Application Readiness (NSTAR)". NASA's Glenn Research Center. April 21, 2009. Archived from the original on January 11, 2003. Retrieved 2015-03-18.
  2. ^ Sovey, J. S., Rawlin, V. K., and Patterson, M. J.: "Ion Propulsion Development Projects in U. S.: Space Electric Rocket Test 1 to Deep Space 1." Journal of Propulsion and Power, Vol. 17, No. 3, May–June 2001, pp. 517-526.
  3. ^ a b c "Innovative Engines - The NSTAR Program". NASA Glenn Research Center. Archived from the original on 2004-12-08. Retrieved 2015-03-18. Has diagram, and photo that shows exit grid.
  4. ^ a b "NSTAR". Encyclopedia Astronautica. Archived from the original on 2014-02-09. Retrieved 2015-03-18.
  5. ^ a b c In-flight performance of the NSTAR ion propulsion system on the Deep Space One mission. Aerospace Conference Proceedings. IEEExplore. 2000. doi:10.1109/AERO.2000.878373.
  6. ^ a b Bond, T.; Benson, G.; Cardwell, G.; Hamley, J. (1999-04-06). NSTAR Ion Engine Power Processor Unit Performance: Ground Test and Flight Experience. Aerospace Power Systems Conference. SAE International. doi:10.4271/1999-01-1384.
  7. ^ Rayman, M.D.; Chadbourne, P.A.; Culwell, J.S.; Williams, S.N. (1999). "Mission design for deep space 1: A low-thrust technology validation mission" (PDF). Acta Astronautica. 45 (4–9). Elsevier: 381–388. Bibcode:1999AcAau..45..381R. doi:10.1016/s0094-5765(99)00157-5. Archived from the original (PDF) on 2015-05-09.
  8. ^ "Contributions to Deep Space 1". NASA. Archived from the original on 2023-04-10.
  9. ^ Dawn - Key spacecraft characteristics. 2014.
  10. ^ NSTAR Ion Engine Xenon Feed System: Introduction to System Design and Development Archived 2016-03-04 at the Wayback Machine. Edward D.Bushway (PDF)
  11. ^ Rayman, Marc; Fraschetti, Thomas; Raymond, Carol; Russell, Christopher (April 5, 2006). "Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres" (PDF). Acta Astronautica. 58 (11): 605–616. Bibcode:2006AcAau..58..605R. doi:10.1016/j.actaastro.2006.01.014. Retrieved April 14, 2011.
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