Arcjet rocket

About: Arcjet rocket is a research topic. Over the lifetime, 1121 publications have been published within this topic receiving 9687 citations. The topic is also known as: Arcjet.

Computation and Experiment of Nonequilibrium Nozzle Flow of Arc-heated Air

Abstract: Numerical simulations of a nonequilibrium nozzle flow of are-heated air were carried out using an eight-temperature model composed of translational, N 2 -rotational, O 2 -rotational, NO-rotational, N 2 -vibrational, O 2 -vibrational, NO-vibrational, and electron temperatures. The on-axis profile of each temperature in the nozzle is shown and the thermal characteristics of the nozzle flow are discussed. Measurements of NO emission spectra were also made at wavelengths 220-265 nm at the nozzle exit to determine NO rotational temperature by a curve-fitting method. Computed rotational temperature of NO at the nozzle exit was compared with the experimental temperature to discuss the nozzle flow model introduced to the present numerical analysis. Moreover, the present computation was applied to a nozzle flow in another arcjet facility

Ultrahigh vacuum arcjet nitrogen source for selected energy epitaxy of group iii nitrides by molecular beam epitaxy

Abstract: The key technical challenge in the molecular beam epitaxial (MBE) growth of group III nitrides is the lack of a suitable source of incorporatable nitrogen. In contrast with the growth of the other III–V compound semiconductors by MBE, direct reaction of N2 with excess group III metal is not feasible, because of the high bond strength of dinitrogen. An incorporatable MBE nitrogen source must excite N2 forming a beam of atomic nitrogen, active nitrogen (N2*), or nitrogen ions. rf and electron cyclotron resonance sources use electron impact excitation to obtain atomic nitrogen and in the process generate a wide variety of excited ions and neutrals. Experiments have shown that ionic species in the beam degrade the morphology of the epitaxial layer and generate electrically active defects. Recent theoretical studies have predicted that ground state atomic nitrogen will successfully incorporate into the growing GaN surface, while atomic nitrogen in either of the excited doublet states will lead to etching. In this article, we report on the development of an ultrahigh vacuum-compatible arcjet source which uses an electric arc to thermally dissociate N2. The thermal excitation mechanism offers selective excitation of nitrogen and control of kinetic energy of the active species. This source has been fabricated from refractory materials and uses two stages of differential pumping to minimize the pressure in the growth chamber. The arcjet has been reliably operated at power levels of 10–300 W, with no visible degradation of the thoriated tungsten cathode after 300 h. No metal contaminant lines can be found in the optical emission spectrum. Using an Ar-seeded beam for calibration of the optical spectrum, we find that the arcjet plasma is far from local thermodynamic equilibrium, and show that the fraction of atomic nitrogen in the beam ranges from 0.3% to 9%. This corresponds to a flux of 0.1–4 monolayers per second at the MBE sample location. With an articulated Langmuir probe sampling the beam at the MBE growth position, we find a positive ion flux of less than 4× 10−9 A/cm2, a maximum ion kinetic energy of 3.5 eV, a median electron energy of 1 eV, and a maximum electron energy of less than 4 eV. With increasing arcjet power, the ion and electron fluxes increase and the ion energy distribution shifts to lower energies. No change in the electron spectrum is observed. Quadrupole mass spectra of the ion flux measured on the arcjet axis show that the N+/N2+ ratio has a maximum at an arcjet power of about 35 W.

Computational Simulation of Emission Spectra from Shock-Layer Flows in an Arcjet Facility

Abstract: This paper reports computational comparisons with experimental studies of a nonequilibrium bluntbody shock-layer e ow in a high-enthalpy arcjet wind tunnel at NASA Ames Research Center. The experimental data include spatially resolved emission spectra of radiation emanating from a shock layer formed in front of a e at-faced cylinder model. Multitemperature nonequilibrium codes are used to compute the conical nozzle e ow, supersonic jet, and shock-layer e ow. A line-of-sight (LOS) radiation code is employed to predict the spectra from the computed e owe eld. Computed LOS emission intensities are directly compared with the experimental data at several axial locations along the stagnation streamline. Various LOS-averaged e ow properties, such as vibrational and rotational temperatures, and species number densities, deduced from the experimental spectra, are compared with computed results. Comparisons provide an assessment of thermochemical equilibration processes in an arcjet shock layer.

Increased deposition rate of chemically vapor deposited diamond in a direct‐current arcjet with a secondary discharge

Abstract: A secondary discharge was used to enhance chemical nonequilibrium in the boundary layer of a stagnation point flow reactor during the atmospheric pressure deposition of chemically vapor deposited (CVD) diamond with a direct‐current (dc) arcjet. The secondary discharge was induced by means of a positive potential on the deposition surface to drive a current through the boundary layer and produce energetic electrons. These electrons can promote superequilibrium concentrations of radicals at the growth surface. It was found that with 3.5 A/cm2 at 115 V in the secondary discharge, the growth rate of diamond in this reactor increased by a factor of 6 as compared with the floating or grounded substrate case.