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BR-112023006886-B1 - METHOD FOR CONTROLLING MIXING RATIO BY THERMAL ACTION IN PROPELLANT TANKS OF SPACE SYSTEMS

BR112023006886B1BR 112023006886 B1BR112023006886 B1BR 112023006886B1BR-112023006886-B1

Abstract

METHOD FOR CONTROLLING MIXING RATIO BY THERMAL ACTUATION IN PROPELLANT TANKS OF SPACE SYSTEMS. This patent application relates to a method, which uses real pressure, temperature, and mass data obtained from real telemetry, to control the mixing ratio by altering the adjusted temperature in its tanks. For the purposes of this patent application, the mixing ratio is defined as the ratio between the consumption of oxidizer mass and the consumption of fuel mass. To this end, the space system in question must have a bipropellant propulsion system operating in blow-down mode, containing independent temperature control systems for each tank. This patent application is related to the space field; the application of this method is of interest to the areas of manufacturing and operation of space systems.

Inventors

  • Henrique OLIVEIRA DA MATA

Assignees

  • INSTITUTO DE APLICACOES OPERACIONAIS - IAOP
  • COMANDO DE OPERAÇÕES AEROESPACIAIS - COMAE

Dates

Publication Date
20260310
Application Date
20201016

Claims (19)

  1. 1. Method for controlling the mixing ratio by thermal actuation in the propellant tanks of space systems for a bipropellant propulsion system operating in blow-down mode containing independent temperature control systems for each of the tanks, characterized by allowing, from the use of real pressure, temperature and mass data obtained from real telemetry, the control of the mixing ratio of propellant consumption from the alteration of the temperature set in its tanks and comprising three stages and respective sub-stages: - Stage 1 - Obtaining the Pressure as a function of Temperature Relationship - P(T): which, from a qualitative model, uses a set of telemetry data from the space system to obtain the mathematical relationship that allows calculating the pressure as a function of a temperature set in the propellant tanks; - Stage 1 comprises the Substages of Data Acquisition (211), Metric Definition (212), Parameter Estimation (213) and Relationship Evaluation (214); - Stage 2 - Obtaining the Mixing Ratio as a function of Pressure - MR (P): which, based on a qualitative model, uses a set of space system telemetry data to obtain the mathematical relationship that allows calculating the mixing ratio of consumption as a function of pressure in the propellant tanks; Stage 2 comprises the Substages of Data Acquisition (221), Metric Definition (222), Parameter Estimation (223) and Relationship Evaluation (224); Step 3 - Obtaining the Temperature to be Adjusted (TA) for Mixing Ratio Control: This step uses both relationships obtained in Steps 1 and 2 recursively to find the temperature that causes the system to operate at a specific mixing ratio of interest. In Step 3, the relationships are sequenced, generating the Direct Relationship of the Mixing Ratio as a function of Temperature - RM (T). A search algorithm is used to "invert" this relationship, leading to the Inverse Relationship Temperature as a function of the Mixing Ratio - T (RM). By applying a value of the Mixing Ratio of Interest (RMI) as Input (231) to the Relationship T (RM), the temperature to be adjusted (TA) is finally obtained in Output (235). This is also the final result of the Method. By acting thermally on the propellant tanks of space systems, the temperature (T) will be regulated to the value of the temperature at to be adjusted (TA) obtained at Output (235) of Step 3 and, as a result, the Mixing Ratio (MR) is controlled to an Adjusted Mixing Ratio (AMR), so that the difference with the Interested Mixing Ratio (IMR) tends to zero, with Step 3 comprising Input (231), Pressure Estimation Substep (232), Mixing Ratio Estimation Substep (233), Error Minimization Substep (234) and Output (235).
  2. 2. A method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized by being implementable by means of a computer program.
  3. 3. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized in that: - Steps 1 and 2 are independent of each other and can be calculated by means of one of the following methods: a) sequentially; b) simultaneously; or c) with the start of either of the two steps without necessarily the completion of the other previously started; and - Step 3 can only be started after the complete completion of both Step 1 and Step 2.
  4. 4. A method for controlling the mixing ratio by thermal actuation in the propellant tanks of space systems, according to claim 1, characterized in that Steps 1 and 2 are based on the formulation of relationships based on the physicochemical behavior of the propellants and the propulsive characteristics of bipropellant systems, and that techniques are used to identify the parameters that adjust these relationships to the real telemetry data.
  5. 5. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized in that in the Data Acquisition Substep (211) of Step 1, the operator must obtain pressure telemetry data. temperature and remaining mass For each of the propellant tanks, it is sufficient to access the space system's telemetry database and prepare the obtained data for analysis. In addition to eliminating corrupted data, the preparation mainly consists of synchronizing the telemetry data, thus obtaining three synchronized sets with the same number of data points, allowing analysis by the subsequent Substeps.
  6. 6. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1 and 5, characterized in that in the Metric Definition Substep (212) of Step 1, the operator must calculate a mass estimate (M0) based on any initial values for the parameter vector (KM) and the values of α, β and Y, these values being calculated using telemetry data prepared in the Data Acquisition Substep (211) of Step 1, according to the equation: where P is the pressure in the tank, T is the temperature in the tank, M is the mass of propellant available, U is the free volume in the tank, v0 is the initial volume of the tank, e is the elasticity coefficient of the tank, rho is the density of the propellant, nhe is the number of moles of pressurizing gas, R is the universal gas constant, Pv is the vapor pressure, and Z is the solubility coefficient.
  7. 7. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 5 and 6, characterized in that in the Parameter Estimation Substep (213) of Step 1, the operator must minimize the errors found in the estimate (M0) by changing the parameter values in the vector (KM) and obtaining, using any parameter estimation method, the vector of estimators (KM).
  8. 8. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 5, 6 and 7, characterized in that in the Ratio Evaluation Substep (214) of Step 1, the operator must evaluate the predictive capacity of this ratio, and for this purpose, must use the estimator vector (KM) estimated from telemetry data of a given period to predict the pressure (P*) of the following period by solving the equation: , where P is the pressure in the tank, T is the temperature in the tank, M is the mass of propellant available, U is the free volume in the tank, v0 is the initial volume of the tank, e is the elasticity coefficient of the tank, rho is the density of the propellant, nhe is the number of moles of pressurizing gas, R is the universal gas constant, Pv is the vapor pressure, and Z is the solubility coefficient, so that this prediction must be compared with the telemetry value of the pressure. .
  9. 9. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized in that in the Data Acquisition Substep (221) of Step 2, the operator must obtain telemetry data of the pressures in the lines. and the mass consumption of both propellants for each use of the propulsion system To do this, one simply needs to access the space system's telemetry database and prepare the obtained data for analysis. In addition to eliminating corrupted data, the preparation mainly consists of synchronizing the telemetry data, thus obtaining two synchronized sets with the same number of data points, allowing analysis by the subsequent Substeps.
  10. 10. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1 and 9, characterized in that in the Metric Definition Substep (222) of Step 2, the operator must relate the consumption data obtained by telemetry. and calculate the Mixing Ratio , such that: , where the operator must calculate an estimate of the mixing ratio. based on any initial values of the parameter vector (KRM) using telemetry data of line pressures , applied in the equation , where POX is the pressure in the oxidant tank, PCO is the pressure in the fuel tank, and a, b, c, d, and e are equation parameters to be estimated.
  11. 11. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 9 and 10, characterized in that in the Parameter Estimation Substep (223) of Step 2, the operator must minimize the errors found between the estimate and the measured value by altering the values of the parameter vector (KRM) and obtaining the estimator vector (K*RM), the estimation must be done by separating the telemetry data into groups of operating conditions for the same type of propeller sets.
  12. 12. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 9, 10 and 11, characterized in that in the Ratio Evaluation Substep (224) of Step 2, the operator must evaluate the predictive capacity of this model, and for this purpose, must use the estimator vector (K*RM) estimated from telemetry data of a given period to predict the mixing ratio. of the following period applying the equation , where POX is the pressure in the oxidant tank, PCO is the pressure in the fuel tank, and a, b, c, d, and e are parameters of the equation to be estimated, and this prediction should be compared with the value of the reference mixing ratio.
  13. 13. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1 and 3, characterized in that, after Steps 1 and 2 are completed, the operator has the ability to predict the mixing ratio based on pressure values by estimating the parameter vector (K*RM) and the ability to predict the pressure based on temperature and mass values by means of the subsystem parameter vector (K*M), such that the operator can calculate the mixing ratio (RM) as a function of the propellant tank adjustment temperatures (T).
  14. 14. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized in that the operator must enter, as Input (231) of Step 3, the value of the mixing ratio of interest (RMI).
  15. 15. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 1, characterized in that in the Pressure Estimation Substep (232) of Step 3, from any initial temperature value, the pressure in the tanks is calculated under that temperature.
  16. 16. Method for controlling the mixing ratio by thermal actuation in the propellant tanks of space systems, according to claims 1 and 15, characterized in that in the Mixing Ratio Estimation Substep (233) of Step 3, from the pressure value calculated in the Pressure Estimation Substep (232) of Step 3, the propulsion mixing ratio is calculated under that pressure.
  17. 17. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 15 and 16, characterized in that in the Error Minimization Substep (234) of Step 3 it evaluates whether the calculated mixing ratio is equal to the mixing ratio of interest (RMI), and in the case of a negative evaluation, the Error Minimization Substep (234) of Step 3 defines another temperature to be tested and restarts the search from Substep (232) of Step 3 and in the case of a positive evaluation, the temperature to be adjusted (TA) is presented in the Output (235) of Step 3.
  18. 18. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claim 17, characterized by the fact that, for the Error Minimization Substep (234) of Step 3, the implementation of numerical methods is recommended that allow minimizing the error function: error(T)=RMI- RM (T) .
  19. 19. Method for controlling the mixing ratio by thermal actuation in propellant tanks of space systems, according to claims 1, 8, 12, 15 and 16, characterized in that the Pressure Estimation Substep (232) of Step 3 and the Mixing Ratio Estimation Substep (233) of Step 3 are adaptations of the Ratio Evaluation Substep (214) of Step 1 and the Ratio Evaluation Substep (224) of Step 2, respectively, for the recursive search application performed in Step 3.

Description

PRESENTATION OF THE INVENTION [1] This patent application relates to a method, which uses real pressure, temperature and mass data obtained from real telemetry, to control the mixing ratio based on changes in the temperature set in its tanks, wherein, for the purposes of this patent application, the mixing ratio is defined as the ratio between the oxidant mass consumption and the fuel mass consumption. [2] To that end, the space system in question must have a bipropellant propulsion system operating in blow-down mode containing independent temperature control systems for each of the tanks. It should be noted that the term blow-down, derived from the English language, is the one widely adopted in the area of space systems, but it is also identified, in a free translation into Portuguese, as “modo sopro”. FIELD OF APPLICATION [3] The present patent application is related to the Space field, the application of this method is of interest to the areas of Manufacturing and Operation of Space Systems. DESCRIPTION OF THE STATE OF THE ART [4] Patent reference US 6755378B2 - System and Method for Controlling a Space-Borne Propulsion System - presents the state of the art of controlling performance parameters of a space propulsion system using a system and method based on the thermal actuation of a propellant tank using the ideal gas equation PV=nRT as a qualitative model. [5] Patent reference KR 100985741B1 - The satellite thruster system pressurized with electrical motor pump - presents the use of a satellite propulsion system pressurized by an electric pump, allowing pressure control in the thrusters for better use of the available propellant. [6] US patent reference 5251852A - Thermal Fuel Transfer and Tank Isolation to Reduce Unusable Fuel, presents the transfer of propellants by thermal actuation, in which the different heating between two propellant tanks of the same propulsion system leads to a pressure differential between the tanks in order to transfer propellant from one to the other. [7] Patent reference WO 87000816A1 - Bi-Liquid Propulsive System for an Artificial Satellite and Utilization of Said System for Ejecting the Satellite - presents a bipropellant propulsion system for artificial satellites and the use of this system in the context of end-of-life satellites. In this patent, two pairs of tanks are filled unequally in such a way that, when the tanks in short supply are observed to be depleted, propellant remains available in the excess tanks to perform the end-of-life maneuver. [8] Patent reference WO 2014/058503A2 - Estimation of Propellant Remaining in a Satellite - presents a method for estimating propellants available in a satellite based on obtaining telemetry data on pressure and temperature from its propellant tanks. [9] Patent reference US5880356 (A) - Device for pressurizing a unified two-liquid propulsion subsystem geostationary satellites - discloses equipment capable of ensuring, during the orbit transfer phase, pressurization in the tanks of a bipropellant system and, during the operational phase, repressurization of the tanks and measurement of available propellants. TECHNICAL PROBLEMS EXISTING IN THE STATE OF THE ART [10] US patent reference 6755378B2 utilizes the concept of thermal action on a propellant tank of a monopropellant propulsion system in order to maintain pressures in this tank at acceptable levels for maintaining the propulsive efficiency of the system. To this end, it uses the efficiency in thrust generation (ΔV) as a performance parameter. This is very relevant in space systems with only one tank (monopropellants) where this is the main limiting factor of lifespan. In monopropellant systems, a greater pressure drop in the tanks is expected throughout the service life, implying a significant loss of performance. But when considering larger systems with two or more tanks (bipropellants), the pressure drop is not so significant as to significantly impair thrust efficiency. Therefore, in bipropellant systems it is not enough to analyze the efficiency in thrust generation, but mainly the consumption ratio between the propellants. This consumption ratio, called the mixing ratio, must be controlled in such a way as to reduce the excess of one propellant when the other is depleted, that is, to reduce the residue. The residue occurs because the consumption rate of each propellant depends on the pressure in the propellant tanks. As propellant is consumed, the free volume in the tank increases, reducing the pressure in the tanks. This pressure reduction leads to a reduction in the consumption rate of that propellant. And since each tank will have a distinct pressure reduction over time, the consumption rate will also occur differently, leading to the existence of residual propellants. In other words, the existence of residues at the end of life has a more significant impact on shortening the operational life of bipropellant space systems than the decrease in thrust generation ef