In-Flight Contamination Measurements of the ESEX 26 kW Ammonia Arcjet
Abstract
The United States Air Force Research Laboratory's Electric Propulsion Space Experiment (ESEX) was launched and operated in early 1999 in order to demonstrate the compatibility and readiness of a 30-kW class ammonia arcjet for satellite propulsion applications. As part of this flight, an array of on-board contamination sensors was used to assess the effect of the arcjet on the spacecraft surfaces and environment. The contamination sensors have also been used to assess the spacecraft outgassing and to provide information during in-flight anomalies. The sensors consisted of microbalances to measure material deposition, radiometers to assess material degradation due to thermal irradiation, and solar cell segments to quantify the potential for solar array degradation. No material deposition is observed during six arcjet firings, with the exception of the first firing. Deposition during the first firing is observed only on the microbalance near the arcjet exit, and is attributed to the expulsion of foreign material within the arcjet that presumably accumulated during the fabrication, integration, and storage of the device prior to launch. Solar cell degradation is observed during the firings and is attributed to the exhaust plasma forming slightly conductive paths away from the cell load. Once the firing ends, the solar cell returns to full operation with no observable degradation. Initial evaluation of the radiometer data suggests some material degradation of the 513-GLO coating, however a more detailed transient analysis is required for a conclusive result. Flight data is continuing to be collected on all contamination sensors to further quantify changes to the spacecraft atmosphere due to operation of the other 8 experiments aboard the ARGOS spacecraft.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1999
- Accession Number
- ADA404912
Entities
People
- D.b. Bromaghim
- G.g. Spanjers
- J.h. Schilling
- L.k. Johnson
- S.f. Engelman
Organizations
- Air Force Research Laboratory