Aerotecnica Missili & Spazio

, Volume 97, Issue 1, pp 19–26 | Cite as

Unsteady 1-D Thrust Modeling with EOS Effects for Ram Accelerator Experiments at Different Bores

  • C. Knowlen
  • P. Bauer
  • T. Bengherbia
  • Y. F. Yao
  • A. P. Bruckner
  • M. Giraud


Advances made to the unsteady, one-dimensional (1-D) modeling of the thermally choked ram accelerator thrust-Mach number characteristics include the use of real-gas equations of state to account for the compressibility effects of the combustion products. Equations of state based on generalized empirical and theoretical considerations are incorporated into a 1-D computer code to predict the combustion end state equilibrium conditions when the propellant starts out a relatively high fill pressure (>2.5 MPa) and the projectile acceleration exceeds 100 km/s2. The objective of this work is to improve the unsteady 1-D model as a useful tool to predict the thrust of the thermally choked ram accelerator propulsive mode by utilizing key results from the more computationally intensive 2-D or 3-D simulations. New thrust-Mach number calculations compared with experimental data from 25-mm, 30-mm, 38-mm, 90-mm, and 120-mm-bore experiments are generally in good agreement until the point where enhanced accelerations are observed, presumably due to projectile material combustion. The results of this investigation indicate the need for more research on ram accelerator flow fields and the role projectile material may play in the combustion process.

List of Symbols


cross sectional of the tube


acceleration of the projectile


co-volume of species i


specific heat capacity at constant pressure


Chapman-Jouguet state


control volume


CJ detonation speed


specific internal energy




specific enthalpy


length of projectile


length of control volume


Mach number


mass of projectile


static pressure


heat of reaction


non-dimensional heat release, Δq/cp1T1


gas constant




projectile velocity


specific volume


molar fraction

1, 2

inlet, outlet reference of control volume


acceleration parameter, (Lcvap)


adjustable parameter in BKW EoS


adiabatic heat capacity rate,(dh/de)s


specific heat ratio


adjustable parameter in BKW EoS


non-dimensional enthalpy, h/cp1T1


adjustable parameter in BKW EoS


compressibility factor


adjustable parameter in BKW EoS


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Copyright information

© AIDAA Associazione Italiana di Aeronautica e Astronautica 2018

Authors and Affiliations

  • C. Knowlen
    • 1
  • P. Bauer
    • 2
  • T. Bengherbia
    • 2
  • Y. F. Yao
    • 3
  • A. P. Bruckner
    • 1
  • M. Giraud
    • 4
  1. 1.University of WashingtonSeattleUSA
  2. 2.Laboratory PPRIMEENSMAFrance
  3. 3.University of the West of EnglandBristolUK
  4. 4.Exobal ConsultingFrance

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