Development and characterization of small SPT

Abstract

Problems appearing in the development of small SPT are analyzed and some results of the small SPT development and characterization are represented in a paper, namely: general relationships reflecting the thruster performance level dependence on the thruster scale, results of the special SPT-80 methodical model tests, illustrating the restrictions caused by the scaling factor impact results of the SPT-30 as well as results of the SPT-25 development and characterization. These results confirm that it is possible to ensure the accelerator thrust efficiency (calculated without cathode mass flow rate) level of 0.25...0.30 at least in a power range (100-200)W under specific impulse (1000-1400)s and thruster life time (500-1000)hours. INTRODUCTIONAs it is well known one of the modern space technology development tendencies is an increase of small spacecraft number in space allowing to reduce a mission cost. Therefore it is necessary to develop adequate propulsion subsystems (PS) and, in particular, the PS based on electric propulsion. Taking into account the great flight heritage of SPT it was natural to investigate the performance level of such thrusters of reduced scale and power. There are some physical particularities of these thrusters limiting the possibility to ensure high level of thrust efficiency while thruster scale is reduced. To check these particularities there was developed, manufactured and tested in a wide range of operation modes SPT-80 methodical model. This study had been fulfilled in the frames of International Space Technology, Inc. R&D efforts.Then there was developed and tested the SPT-30 demo model for the NASA LeRC having external accelerating channel diameter 30 mm and according to

A Hall thruster performance model incorporating the effects of a multiply-charged plasma

“…Although the ion species fractions have been shown to be a function of voltage and flow rate, 28 the multiply-charged model will neglect such considerations. Figure 2 plots data from several thrusters [8][9][10][11][12][13][14][15][16][17][18] as I sp versus discharge voltage. Curves labeled "theory" assume no voltage loss while the "model" curves are those predicted by the model.…”

“…[6][7] Commercially developed Hall thrusters typically operate between 50-60% efficiency, achieving specific impulses between 1500-2500 seconds. [8][9][10][11][12][13][14][15][16][17][18] Operation below 1500 s generally results in intolerable decay in thruster efficiencies (<35% efficiency around 1200 s specific impulse). 10 Operation above 2500 s has not been demonstrated for extended periods of time in the literature, but it is widely believed that the lifetime of a high I sp Hall thruster will be significantly less due to the production of multiply-charged ions resulting from the higher voltages encountered in the discharge chamber.…”

Erosion Measurements in a Low-Power Cusped-Field Plasma Thruster

“….200 ≈3.8 [57] HBC BN 2.2 [57] HT-100 [16] 1,500 ×, ‡, § [17] 445 300 [17] .175 9 60/40:BN/SiO 2 [4] 7.5 MIT DCFT >1,220 204 1,220 * .165 1.9 HP BN 2-3 SPT-30 [18] 600 × --.150 -borosil -SPT-20M [20] 4,000 ‡ 1,000 594-910 <.100 -alumina [5] w/ additive 24 [5] -Indicates data not found in reviewed literature. * Indicates an extrapolation from measured erosion profiles, not an experimental demonstration † A material grade is specified where possible.…”

“…A more complete summary of Hall thruster erosion measurements is provided in Table 4. SPT-50 [13] 320 47% >2,500 × -KM-45 [14] 310 40-50% [1] 3,500-4,000 -KM-32 [2] 200 30-40% 2,000-3,000 3,000 * BHT-200 [15] 200 43.5% 1,287-1,519 >1,700 HT-100 [16] 175 25% [4] 300 [17] 1,500 [17] * * SPT-30 [18] 150 26% [19] 600 * -SPT-20M [20] <100 ≤38% [5] 594-910 4,000…”

Krypton Performance Optimization in High-Voltage Hall Thrusters

“…Channel width is chosen for their scaling constant because they say that channel width is characteristic of the region with significant electric fields. According to Kim, 19 discharge channel length and width scale proportionally, so that either choice for scaling is probably equivalent. Bugrova et al 18 suggest that the value of α is approximately constant at 0.02 mg/(s mm) and is similar for both krypton and xenon.…”