G. F. Karabadzhak

Modeling of ultraviolet radiation in steady and transient high-altitude plume flows

Ultraviolet radiation from hydrazine spacecraft thruster plumes interacting with ambient atomic oxygen is modeled forlow-Earth-orbit conditions. Two numerical techniquesthatemploy the direct simulation MonteCarlo method are applied for the e rst time to the modeling of space plume radiation transient and three-dimensional e ows. These efe cient procedures allow one to analyze the effect of atomic oxygen penetration of the thruster plume, which is a key factor in modeling raree ed space plume radiation. The overlay technique is used to model thetransiente owevolutionduringthee rstseveralsecondsaftermotorignition.Goodagreementbetweenmodeling and experiment are obtained before 1-s motor burn time. The sensitivity of the plume radiation to the molecular total collision model is analyzed using the overlay technique, and the radiation spatial distribution was found to be strongly dependent on the temperature exponent of the coefe cient of viscosity. Three-dimensional computations are conducted for different angles between the plume axis and the freestream directions, and the radiation maps forOH(A)andNH(A)arepresented.Signie cantdifferencebetween OH (A)andNH(A)radiatione eldsasafunction of the angle of attack is shown.

DSMC computations of the Progress-M spacecraft retrofiring exhaust plume

Abstract : A set of DSMC computations using the SOCRATES computer code has been performed to aid in the development and analysis of the MirEx experiment to observe UV radiation from spacecraft thruster plumes. The plumes of interest for this report originate from the amine propellant main engine of the Progress-M and Soyuz-TM spacecraft. The altitude of the plume observations is approximately 380 km. The SOCRATES calculations provide a baseline estimate of the spatial distribution of the exhaust gases as they interact with the ambient low-density atmosphere composed predominantly of atomic oxygen. In addition, a proposed mechanism for OH(A) excitation based upon high-velocity collisions between H2O and O is exercised. A sequence of calculations was performed to investigate the influence of the angle of attack of the engine upon the predicted radiation levels. In general, it is found that the predicted OH(A) generation has a very large spatial scale, on the order of several kilometers. Comparison of the predictions with data showed the predictions were high, leading to speculation that the excitation cross section used in the calculations may be suspect. A preliminary variation of the energy threshold was performed using a set of experimental conditions. It was found that an increase in the energy threshold could bring the predictions into agreement with both the spatial distribution and the absolute signal level of the experimental data.

Measurements of the Progress-M main engine retrofiring plume at orbital conditions

Abstract : An experiment set has been performed using the Progress-M spacecraft and a set of dedicated and non-dedicated maneuvers in the vicinity of the Mir space station. The purpose of the experiment was to acquire ultraviolet data from the far-field glow of rocket exhaust plumes at very high altitudes. Ultraviolet imagery of the Progress main engine was acquired using a camera with a response function that peaked at 290 nm. The data show an intense near-field radiation accompanied by a low-level glow that exists over spatial scales of kilometers. The emission is attributed to the decay of the OH(A) state, presumably formed in reactive collisions of plume species with atmo- spheric atomic oxygen. While many observations were recorded of the main engine that is used on both the Progress-M and Soyuz-TM spacecraft, as well as the smaller attitude control system thrusters, two key main engine measurements are reported here. In the first measurement, the imager field of view was at a right angle to the plume axis, at a radial range of 9.2 km. The firing lasted 5.3 sec. In the second measurement of the main engine plume, the aspect angle varied from 173 to 168 deg while the range from the main engine to the Mir station ranged from 15 to 28 km. The firing lasted 244 sec in that case. In both measurements, the far-field emission was found to completely fill the imager field of view. A relatively sluggish rise of the far-field radiation was observed at ignition, as compared to the near-field radiation. The measurements of the far-field plume were calibrated using the irradiance of a known star. It was estimated that within the portion of the plume observed by the Imager, the plume radiated 30 and 150 W of power for the first and second measurements, respectively. These results are briefly compared with the requirements for OH(A) generation the H(2)O+O reaction.

Auroral activity caused by high-power radioemission from the SURA facility

A series of experimental modifications of the ionosphere in the HF range, performed at the SURA facility base, together with optical measurements onboard the International Space Station (ISS), indicated that such impacts on the ionosphere are effective when the facility operational frequency is higher than the critical plasma frequency (for the main ionospheric F2 layer). The experimental measurements were supported by measurements at ground-based observatories, ISS, and the Demeter and GPS satellites. The analysis results of the entire data set are presented. The ray HF radio tracing for the experiment of October 2, 2007, has been calculated, and it has been indicated that the ionosphere to the north of the facility up to 60°–62° N latitudes was irradiated by the facility beam (the effects of ray redistribution and refocusing) due to refraction on the gradient of the F2 layer critical frequencies. An analysis of the ground-based and satellite measurements (both in the vicinity of a heater and in the magnetically conjugate region) indicates that it is possible to trigger a substorm in experiments with the Sura heating facility.

Nonequilibrium shock-layer radiation in the systems of molecular bands NO and N2(+)(1-) - Experimental study and numerical simulation

The results of investigation of nonequilibrium air radiation in a shock layer of the systems of molecular bands NO and N^O-) are presented. The studies included the experiments on a measurement of the nonequilibrium radiation behind a strong shock wave in the Electric Arc-driven Shock Tube within the range of shock wave velocity change Vs = 5 to 10 km/s at the initial air pressure Pl = 0.1 torr and numerical simulation of radiation processes behind the shock wave and hi a hypersonic viscous shock layer, where nonequilibrium processes were simulated on the basis of Navier-Stokes equations. A numerical model of the radiation behind the strong shock wave has been used to verify a kinetic scheme of radiation processes by comparison with experimental results. The examples of emission calculations in the systems NO and N£ (1-) for the conditions of flight test described in Ref. 1 are presented.