Journal of Jet Propulsion 

About: Journal of Jet Propulsion is an academic journal. The journal publishes majorly in the area(s): Combustion & Rocket. Over the lifetime, 305 publications have been published receiving 4944 citations.

Laminar Heat Transfer Over Blunt-Nosed Bodies at Hypersonic Flight Speeds

Abstract: This paper deals wi th two l imit ing cases of laminar heat transfer over blunt-nosed bodies at hypersonic flight speeds, or high s tagnat ion temperatures: (a) thermodynamic equil ibrium, in which the chemical reaction rates are regarded as "very fas t" compared to the rates of diffusion across streamlines; (b) diffusion as rate-governing, in which the volume recombination rates within the boundary layer are "very s low" compared to diffusion across streamlines. In either case the gas density near the surface of a blunt-nosed body is m u c h higher than the density jus t outside the boundary layer, and the velocity and stagnation enthalpy profiles are m u c h less sensitive to pressure gradient than in the more familiar case of moderate temperature differences. In fact, in case (a), the nondimensionalized enthalpy gradient at the surface is represented very accurately by the "classical" zero pressure gradient value, and the surface heat-transfer rate distribution is obtained directly in terms of the surface pressure distribution. In order to i l lustrate the method , this solution is applied to the special cases of an unyawed hemisphere and an unyawed, b lunt cone capped by a spherical segment . In the opposite l imit ing case where diffusion is ratecontrolling the diffusion equation for each species is reduced to the same form as the low-speed energy equation, except that the Prandtl number is replaced by the Schmidt number . The simplifications introduced in case (a) are also applicable here, and the expression for surface heat transfer rate is similar; the maximum value of the ratio between the rate of heat transfer by diffusion alone and by heat conduction alone in the case of thermodynamic equil ibrium is given by: (Prandtl n o . / S c h m i d t no.)'. When the diffusion coefficient is es t imated by taking a reasonable value of a tom-molecule collision cross section this ratio is 1.30. Additional theoretical and (especially) experimental studies are clearly required before these s imple results are accepted.

On Catalytic Recombination Rates in Hypersonic Stagnation Heat Transfer

Abstract: Stagnation laminar heat transfer at hypersonic speeds depends on the rate of recombination of the dissociated air behind the detached shock wave. This paper is concerned with the case of a large recombination t ime compared to the t ime of diffusion across the boundary layer. The conditions of existence of such a "frozen flow" and i ts coupling with the dissociation lag behind the shock are discussed. In order to account for finite catalytic recombination rates at the wall, a nonsimilar boundary condition is introduced which can be reduced to similarity for stagnation flow only. In this latter case, Lees' ( l ) 3 and Fay and Ridell's (2) heat transfer solutions are shown to correspond to the l imit ing case of an infinitely fast catalyst. The validity of their solutions is extended to the general case of a wall of finite catalytic efficiency, by introducing a correction factor (p. This factor is a s imple function of the flight condit ion, nose geometry and the wall catalytic recombinat ion rate constant . For a given nose material , the percentage of the heat transfer by catalysis is found to in crease wi th the velocity, the nose diameter and the wall temperature and to decrease with alt itude. Finally, the experimental values obtained for the catalytic recombination rates of oxygen and nitrogen atoms on various surfaces i l lustrate numerically the importance of the nature of the wall on the catalytic heat transfer to a missi le nose . In particular, the superiority of pyrex over metal l ic surfaces stresses the need for more experimental values for glassy and ceramic coatings.

Observation of High Intensity Radiation by Satellites 1958 Alpha and Gamma

Abstract: A preliminary report of results obtained concerning radiation intensities measured with single Geiger tubes carried by Explorer I and III is presented. Resonable cosmic-ray counting rates were obtained for altitudes below about 1000 km. A plot of omnidirectional intensity vs. height in the vicinity of California for the first two weeks in February was obtained, This curve, extrapolated down to altitudes previously reached by rockets, agrees with earlier data, At altitudes greater than about 1100 km, very high counting rates were obtained. (W.D.M,)

Intermittent Detonation as a Thrust-Producing Mechanism

Abstract: The feasibility of a reaction device operating on intermittent gaseous detonation waves is considered. The results of a simplified theoretical analysis are presented and discussed. Preliminary experiments were conducted to determine the impulse derived from a single detonation wave and to investigate some of the more influential parameters: These tests were effected by suspending the detonation tube as a pendulum. A cyclic detonation tube was designed and operated utilizing hydrogen-air mixtures. Measurements of thrust, fuel flow, air flow, and temperatures were obtained over a range of operating conditions. Specific impulses of over 2100 sec were realized, which was in good agreement with the predicted performance.