scholarly journals On the choice of a parking orbit for a service spacecraft

2020 ◽  
Vol 2020 (3) ◽  
pp. 30-38
Author(s):  
Yu.M. Holdshtein ◽  
Keyword(s):  
Mathematical Model ◽  
Operational Reliability ◽  
Analytical Determination ◽  
Transfer Program ◽  
Low Thrust ◽  
Transfer Energy ◽  
Orbital Transfer ◽  
Energy Expenditures ◽  
Parking Orbit ◽  
Orbital Transfers

At present, the requirements for increasing spacecraft active life and operational reliability and reducing spacecraft operation costs become more and more stringent. Because of this, on-orbit servicing becomes more and more attractive. One of the most promising ways to increase the efficiency of transport operations in space is to carry out on-orbit servicing using reusable spacecraft with low-thrust solar electrojet engines. The aim of this paper is to develop a mathematical model for the choice of an optimal low near-Earth parking orbit for a reusable service spacecraft. The case of noncoplanar near-circular orbits of spacecraft and a shuttle scenario of their servicing is considered. The solution of the problem of choosing an optimal parking orbit for a reusable service spacecraft involves repeated solutions of the problem of determining the delta-velocity of the service spacecraft’s orbital transfers between its parking orbit and the orbits of the serviced spacecraft. In this connection, using the averaging method, a mathematical model is developed for the analytical determination of orbital transfer program controls and trajectories and assessing orbital transfer energy expenditures. With its use, a mathematical model is developed for the choice of a service spacecraft’s optimal parking orbit. The objective function is the total delta-velocity of the service spacecraft’s orbital transfers from its parking orbit to the orbits of the serviced spacecraft and vice versa with the inclusion of the orbital transfer frequency. The optimizable parameters are the service spacecraft parking orbit parameters. The use of the proposed models is illustrated by an example of service spacecraft parking orbit optimization. What is new is the mathematical models developed. The results obtained may be used in the preliminary planning of on-orbit servicing operations.

Planar High-Thrust and Low-Thrust Orbital Transfers from Earth to Europa

2004 ◽  
Vol 52 (4) ◽  
pp. 421-439
Author(s):  
Hans Seywald ◽  
Carlos M. Roithmayr ◽  
Daniel D. Mazanek ◽  
Frederic H. Stillwagen ◽  
Patrick A. Troutman ◽  
...  
Keyword(s):  
Low Thrust ◽  
Orbital Transfers ◽  
High Thrust

scholarly journals Reliability of the RBMK-1000 coolant flow measurement system

2019 ◽  
Vol 5 (1) ◽  
pp. 81-87
Author(s):  
Arkady I. Pereguda
Keyword(s):  
Mathematical Model ◽  
Measurement System ◽  
Flow Measurement ◽  
Rotation Period ◽  
Operation Time ◽  
Operational Reliability ◽  
Coolant Flow ◽  
Reliability Indicators ◽  
Parametric Reliability ◽  
Two Parameters

An analysis of statistical data of diagnostic measurements of two parameters determining the performance of the RBMK-1000 SHADR-8A flowmeters – the minimum value of the negative amplitude half-wave at the transistor flow measuring unit (TIBR) input and the mean-square deviation over the flowmeter ball rotation period – made it possible to develop a mathematical model of the flowmeter parametric reliability. This mathematical model is a random process, which is a superposition of two delayed renewal processes. Studying the flowmeter operational reliability model provides an exponential estimate of the probability that the parameters determining the flowmeter performance will not exceed the specified levels. Using the Bernoulli scheme and the probability-estimating relationship for the flowmeter performance parameters, it is possible to calculate the probability of failure-free operation of both a single reactor quadrant and the coolant flow measurement system. In addition, it becomes possible to estimate the quadrant failure rate. Important for practice is the possibility of predicting the number of failed flowmeters depending on the system operation time. An indicator of the system reliability can be the average number of failed flowmeters, the relation for which is given in the paper. All the research results were obtained without any additional assumptions about the random values distribution laws. The obtained results can be easily generalized for the cases when the vector dimension of the determining parameters is greater than two. The use of the results of this study is illustrated by calculated quantitative values of the flowmeter parametric reliability indicators and the coolant flow measurement system.

Fast solution of minimum-time low-thrust transfer with eclipses

2018 ◽  
Vol 233 (7) ◽  
pp. 2699-2714
Author(s):  
Max Cerf
Keyword(s):  
Shooting Method ◽  
Optimal Solution ◽  
Search Space ◽  
Low Thrust ◽  
Indirect Methods ◽  
Transversality Conditions ◽  
Derivative Free ◽  
Fast Solution ◽  
Orbital Transfers ◽  
Zero Values

Optimizing low-thrust orbital transfers with eclipses by indirect methods raises several issues, namely the costate discontinuities at the eclipse entrance and exit, the initial costate guess sensitivity and the numerical accuracy required by the shooting method. The discontinuity issue is overcome by detecting the eclipse within the simulation and applying the costate jump derived analytically from the shadow constraint function. By fixing completely the targeted final position and velocity, the transversality conditions are removed and the shooting problem is recast as an unconstrained nonlinear programming problem. The numerical sensitivity issues are alleviated by using a derivative-free algorithm. The search space is reduced to four angles taking near zero values. This procedure yields a quasi-optimal solution from scratch in few minutes without requiring any specific user’s guess or tuning. The method is applicable whatever the thrust level and the eclipse configuration, as illustrated on transfers towards the geostationary orbit.

The Dynamics of Low-Thrust Spacecraft Manoeuvres

1968 ◽  
Vol 72 (695) ◽  
pp. 925-940 ◽  
Author(s):  
E. G. C. Burt
Keyword(s):  
Power Supplies ◽  
Relativity Theory ◽  
Time Varying ◽  
Low Thrust ◽  
Orbital Elements ◽  
Propulsion Systems ◽  
Optimum Time ◽  
Orbital Transfers ◽  
Electrical Propulsion ◽  
Increasing Function

Summary Orbital manoeuvres by means of impulsive thrusts, such as those available with chemical rockets, are well known, but a different treatment is needed for the small, continuous thrusts that are typical of electrical propulsion systems. It is shown that with the aid of these small forces it is possible to change independently all the orbital elements of a spacecraft, and thus to proceed slowly from a given orbit to any other. For each manoeuvre there exists an equivalent velocity which depends only on the initial and final orbital states, and which can be related directly to the spacecraft propulsion parameters. For any form of propulsion where the propellent acquires some or all of its energy from a separate energy source, as in electrical propulsion, it is found that optimum time-varying relations exist between the flow of mass and of energy, which may also be expressed in terms of the exhaust velocity and the thrust. In particular, the optimum exhaust velocity is shown to be an increasing function of time, related to the way in which the energy is released. The practical realisation of electrical propulsion depends on the development of efficient propulsion units and of lightweight power supplies; these and other spacecraft components are discussed, and a number of examples of orbital manoeuvres are given, including close-Earth, far-Earth and lunar orbits. The paper concludes with a discussion of these orbital transfers in relation to their possible uses, including communication satellites and a test of relativity theory

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