Dynamic performance of low-thrust, cold-gas reaction jets in a vacuum.

Greer, H.; Griep, David J.

doi:10.2514/3.29006

Cited by 7 publications

(1 citation statement)

References 11 publications

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“…The non-dimensional Knudsen number, Kn, is used to decide whether the continuum postulate is valid or not. Knudsen Number is defined as the ratio of the molecular mean free path of fluid to the characteristic length of the flow field [Greer et al, 1967].…”

Section: Continuum Postulate Validationmentioning

confidence: 99%

Su2 Real Gas Models’ Performance Predictions on a Cold Gas Thruster

Ozden

Baran

Aksel

et al. 2021

Isı Bilimi Ve Tekniği Dergisi

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Cold gas propulsion systems are preferred, especially for the altitude and trajectory control for satellites, since the 1960s. Both depressurizing the propellant in the propellant tank throughout the mission and the expansion occurring in the divergent part of the thruster nozzle are the reasons for observing very low temperatures and pressure at the outlet section. We have decided to use an open-source compressible CFD tool, SU 2 , in order to predict the performance of the propulsion system in the early design phase. The scope of this study is the comparison of the results of the vacuum chamber performance tests and the outcomes of unsteady simulations with SU 2 using different gas models, including ideal gas, van-der Waals, and Peng-Robinson models. Then, the accuracy and performance of these models are evaluated for the extremely low temperature and pressure conditions. Thruster performance tests have been conducted in the thermal vacuum chamber test campaign at the specially built testing facilities. In order to simulate nominal and low-temperature operation conditions, a propellant tank is thermally conditioned to the predetermined values, and performance test parameters are used as the input for the CFD simulations. The obtained results showed that the van der Waals gas model is the most appropriate gas model for both cases and provides the most realistic results in terms of performance parameters.

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Section: Continuum Postulate Validationmentioning

confidence: 99%

Su2 Real Gas Models’ Performance Predictions on a Cold Gas Thruster

Ozden

Baran

Aksel

et al. 2021

Isı Bilimi Ve Tekniği Dergisi

View full text Add to dashboard Cite

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Pulsed performance of a steam reaction jet.

Greer

Griep

1969

Journal of Spacecraft and Rockets

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The dynamic propulsive performance of a saturated steam reaction jet is analyzed and compared with experimental results at vacuum thrust levels up to 0.015 Ib. The techniques used to obtain accurate test results for a low-thrust, dynamic mode of operation are described. Impulse bit size /bit? steam consumption, and specific impulse / are characterized in terms of thruster geometry, gas properties, and command pulse width 0 C . For 6 C < 50 msec, transient effects cause a loss in / (e.g., 10% for 6 C = 20 msec); steady-state / varies from 85 to 108 sec for saturation temperatures of 150° to 300°F. System performance of the steam reaction jet is compared with that of 9 other gases for equal temperatures and thrust levels. The results indicate that steam is competitive with subliming solids and superior to the propellants stored as gases. However, the NH 3 system, stored as a liquid, has a higher / eff . The steam system requires 20% more heating power (12 w/mlb thrust) than the subliming solid and twice more than NHs, but the danger of line clogging due to solidification is somewhat less. At very low thrust levels, or if the installation is such that a weight penalty for the power source is not incurred, a steam system may be attractive.A 0 a*(2/ 7 yi*/2 V c acoustic velocity = equivalent orifice-to-nozzle area ratio = a\/an ozzle discharge coefficient = w m /P c A t K n thrust coefficient thrust correlation factor = F m /(P c C/At)ideal exhaust velocity coefficient or impulse efficiency characteristic velocity = a*/y[2/(y + l)](7+D/2(7-D diameter thrust, Ibf proportionality constant in Newton's second law enthalpy specific impulse, Ibf-sec/lbm impulse bit ( per pulse), Ibf-sec effective system specific impulse, Ibf-sec/lbm total impulse, Ibf-sec mechanical equivalent of heat ipirical decay time integration factor I P c d0 I P s 0d = 0.0685 choked nozzle flow factor = a* [2/(y -f ; = empirical rise time integration factor I P c d0 I P s 0 r 0.69 k = system factor in Eq. (9) to account for electric heater and minimum gage tank weights (0.87 for gases and 0.80 for liquids and solids) I = nozzle length M = Mach number = u/a* 2fTl = molecular weight N r = Reynolds number = Dup/v N k = Knudsen number = (7r T /2) 1/2 (M/N r ) P = pressure R = universal gas constant T = temperature u = velocity V, v = volume and specific volume, respectively w, w = weight and weight flow rate, respectively x = fraction of condensate present in flow y = pressure ratio transformation = [1 -(F C /P 5 )] 1/2 y. = [1 -(P a /P,)V»7 = ratio of specific heats 5 = surface tension e = nozzle expansion ratio 77 = efficiency B = time v = viscosity £ = Te/Tr p, a = density and working stress, respectively; (p/ J -S as an d incipient condensation, respectively m = measured or delivered Downloaded by UNIVERSITY OF MICHIGAN on February 19, 201...

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Vacuum startup of reactors for catalytic decomposition of hydrazine

Greer

1970

Journal of Spacecraft and Rockets

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Dynamic performance of low-thrust, cold-gas reaction jets in a vacuum.

Cited by 7 publications

References 11 publications

Su2 Real Gas Models’ Performance Predictions on a Cold Gas Thruster

Su2 Real Gas Models’ Performance Predictions on a Cold Gas Thruster

Pulsed performance of a steam reaction jet.

Vacuum startup of reactors for catalytic decomposition of hydrazine

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