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Article

Ahmad Soleymani and Alireza Toloei

– The purpose of this research was to analyze application effects of the stable frozen orbit conditions in the spacecraft Orbital Maintenance Maneuver (OMM) reduction.

Abstract

Purpose

The purpose of this research was to analyze application effects of the stable frozen orbit conditions in the spacecraft Orbital Maintenance Maneuver (OMM) reduction.

Design/methodology/approach

One challenge in implementing these motions is maintaining the relations as it experiences orbital perturbations (zonal harmonics), most notably due to the non-spherical Earth. A natural phenomenon exists called a frozen orbit, for which the orbital elements: argument of perigee (ω) and eccentricity (e) remain virtually fixed over extended periods of time.

Findings

Simulation results show that, using stable frozen orbit condition results in considerable propellant saving, decreased OMM, increase of accuracy position errors and thus performance improvement of the spacecraft for orbiter mission is preferable. So, from among three proposed theories, the Brouwer–Hori theory has provided better accuracy and more stable conditions in the frozen orbit.

Practical implications

Simulation algorithm has been achieved to solve this problem by extracting and combining the equations that govern the frozen conditions with the tangential forces (ΔV) equations for orbit correction.

Originality/value

In all studies with content of harmonic perturbation effects on the spacecraft motion dynamics, main goal is to obtain a solution for optimization of the operation process, so that overshadowed mission costs. The case studies about this aim, mostly to the trajectory parameters optimization by considering the vehicle orbital conditions under various control methods are formed. While in this regards, the intrinsic properties of stable Earth orbits and using them effectively is less than to analyse the problems is considered.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 87 no. 1
Type: Research Article
ISSN: 0002-2667

Keywords

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Article

Elham Mohammadi and Alireza Toloei

The purpose of this paper is to analyze the flowfield structure and performance of dual secondary injection system for thrust vectoring in a convergent‐divergent nozzle…

Abstract

Purpose

The purpose of this paper is to analyze the flowfield structure and performance of dual secondary injection system for thrust vectoring in a convergent‐divergent nozzle and to compare it with a single secondary injection system.

Design/methodology/approach

Dual secondary injection for thrust vectoring in a convergent‐divergent nozzle is studied by solving three‐dimensional Reynolds‐averaged Navier‐Stokes equations by the means of Fluent. Realizable k‐ε turbulent model with enhanced wall‐treatment approach is used for viscous model. Density‐based solver and explicit scheme are employed in the computational model. In order to study the effect of injection location on the flowfield, distance between ports is considered as the key variable.

Findings

Results show that under some circumstances, dual secondary injection system is more effective than a single injection system with the same mass flow rate. The study shows that when the distance between two ports is 8.5 times of the injection port's diameter (or more) and in the same time the first injection port is at least 1 throat diameter far from the nozzle throat, this system will show a better performance. In addition, this system reduces the probability of bow shock impingement to the opposite wall and consequently, the side force production has less limitation.

Practical implications

Dual secondary injection for thrust vector control (SITVC) needs less secondary flow and therefore it makes less reduction in the primary thrust. It means that for a specific primary thrust, less mass fuel is needed which makes it more economic regarding the traditional SITVC systems.

Originality/value

The paper's value lies in using a three‐dimensional model to study the effect of two ports distance on SITVC performance and comparison among the performance of dual and single injections when there is an impingement.

Details

Aircraft Engineering and Aerospace Technology, vol. 83 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

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Article

Mohammad Reza Nasiri Avanaki and Alireza Toloei

The purpose of this paper is to find the best way to obtain the Sagnac phase shift in the output signal of open loop interferometric fiber optic gyroscopes (IFOGs). Also…

Abstract

Purpose

The purpose of this paper is to find the best way to obtain the Sagnac phase shift in the output signal of open loop interferometric fiber optic gyroscopes (IFOGs). Also, the utilized digital filtering based on FIR kaiser window for implementing the digital signal processing part is evaluated.

Design/methodology/approach

The approach is based on implementing four kaiser FIR filters, the coefficients of which have been obtained from SPtool. They were simulated with SPtool in the Matlab 7.1.

Findings

The results show that the chosen computational method has reliable accuracy. On the other hand, it could require low‐computational effort, and it is a simple way which is important for the signal processors.

Research limitations/implications

The limitation in this paper is that the designed filters have high order and they require much time; therefore, a high‐speed device is needed. For solving this problem, it is proposed to perform some estimation by experiments.

Practical implications

IFOGs are used in aircraft, missiles, and new civil fields such as automobile navigation, antenna stabilization, crane control, unmanned vehicle control, wind, and renewable energy platform stabilization.

Originality/value

There is no other paper which has explained mathematics of IFOG implementation in the signal processing part as completely as is done here.

Details

Aircraft Engineering and Aerospace Technology, vol. 81 no. 5
Type: Research Article
ISSN: 0002-2667

Keywords

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Article

Ahmad Soleymani and Alireza Toloei

The purpose of this paper is to analyze the inclusion effects of the linearized time‐varying J2‐perturbed terms for relative accuracy increase significantly over Melton's problem.

Abstract

Purpose

The purpose of this paper is to analyze the inclusion effects of the linearized time‐varying J2‐perturbed terms for relative accuracy increase significantly over Melton's problem.

Design/methodology/approach

The methodology is based on the previous studies provided by Ross's paper. He gives a set of equations based on the CW equations which incorporates the J2 gravitational perturbations and states in his introduction that this method can be expanded for the elliptical reference orbits as described by Melton.

Findings

One challenge in implementing the relative motions is maintaining the relations as it experiences gravitational perturbations, most notably due to non‐spherical Earth. Simulation results show that the inclusion of time‐varying J2 perturbation terms in the derived linear equations increased the accuracy of the solution significantly in the out‐of‐orbit‐plane direction, while the accuracy within the orbit plane remained roughly unchanged.

Practical implications

By reason of replacing approximate terms (e, M) in this solution, for continues accuracy increase of time‐varying parameters containing θ(t) and RO(t), this solution could be useful in the element‐errors evaluation and analysis of orbital multiple rendezvous missions, that are involved to the limited orbit periods.

Originality/value

The originality of this paper is to develop Melton's researches. He provided a method for generalizing the linear equations of motion to an elliptical orbit which enabled the determination of a time‐explicit, approximate solution. In this regard, there is no paper which has evaluated the inclusion effects of the linearized time‐varying J2 perturbation terms over Melton's equations with such an approach.

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