Measuring and testing – With fluid pressure – Dimension – shape – or size
Patent
1997-07-11
1999-03-09
Williams, Hezron
Measuring and testing
With fluid pressure
Dimension, shape, or size
73149, 244172, B64G 140, G01F 1700
Patent
active
058803564
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a device for pressurizing a standardized two-liquid propulsion subsystem of a geostationary satellite.
2. Prior Art
Telecommunications satellites are placed on an orbit in the earth's equatorial plane at approximately 36,000 kilometres from the earth. This circular orbit has the special feature that any satellite object on this orbit has a 24 hour rotation period around the earth. Thus, such an object appears stationary above the earth for an observer on earth. This preferred orbit enables telecommunications satellites to best fulfil their communication relay function between several points on earth.
In order to inject a satellite into its final orbit and keep it there during its useful life, propulsion means must be provided. Standardized subsystems are now used in a general manner. A tendency occurring at present consists of providing a standardized propulsion subsystem, which injects the satellite into its final orbit from its initial or transfer orbit and then keeps the satellite in position.
In such a standardized two-liquid propulsion subsystem, the liquid bi-propellant engine or motor is supplied from the same tanks and primary circuits as the other engines necessary for attitude and orbit control. As a result the transfer phase must take place with the propulsion system under a regulated helium pressure of approximately 18 bars and which is stored in high pressure tanks and once placed in position, the apogee engine and helium source are isolated from the remainder of the subsystem, which then operates at a decreasing pressure as the propellants are consumed in the main tanks. Generally, use is made of two propellants, e.g. monomethyl hydrazine (MMH) as the fuel and nitrogen peroxide (N.sub.2 O.sub.4) as the oxidizer.
Up to now most geostationary telecommunications satellites use such a standardized two-liquid propulsion subsystem.
The user to whom a precise position on the geostationary orbit has been allocated, only wishes to keep on this position satellites which are effective for his particular communications traffic system. Therefore, he regularly replaces any satellite which has become obselescent by a new satellite. The obselescent satellite must then be sent into an orbit where it will not interfere with the new satellites or those around it, when its obsolescence has been established, in order to optimize the profitability of the system installed.
The most frequent reason for ending the life of the satellite is that it has consumed all the propellants maintaining it in position and its pointing towards the earth.
During the satellite life, a significant part of the propellant mass carried is burned in the apogee engine, whose aim is to increase the speed vector of the satellite in order to pass it from an elongated, elliptical orbit known as the transfer orbit to the circular orbit at an altitude of 36,000 km.
Once placed in its orbital position, the satellite is subject to disturbance forces (lunar/solar gravity, solar radiation pressure, etc.), which tend to make it describe cyclic movements with a decreasing amplitude around the initial position. As the ground stations are pointed towards a fixed point in the sky, in order to avoid overequipping the ground stations with satellite tracking means, and in order to keep the satellite in the allocated orbital position, it is necessary to periodically intervene in order to oppose interfering movements of the satellite, by periodically burning a quantity of propellants in the orbit control motors. The satellite is also exposed round its centre of gravity to disturbance torques, which would lead to the depointing thereof. Thus, a quantity of propellants is also periodically burned in the attitude control motors.
The user needs to know the satellite obsolescence date sufficiently well in advance in order to be able to initiate the activities necessary for its replacement. Thus, the satellite operator must be able to reliably predict the end of propellant consumption, so as to be ab
REFERENCES:
patent: 1885926 (1932-11-01), Lewis
patent: 2378849 (1945-06-01), Helleberg et al.
patent: 3234785 (1966-02-01), Rimsha
patent: 4148334 (1979-04-01), Richards
patent: 4485794 (1984-12-01), Kimberly et al.
patent: 4619284 (1986-10-01), Delarue et al.
patent: 4987775 (1991-01-01), Chobotov
patent: 5158362 (1992-10-01), Brauer et al.
patent: 5263666 (1993-11-01), Hubert et al.
Journal Of Propulson And Power, vol. 8, No. 1, Jan. 1992, New York, pp. 74-79, Tso Ping Yeh: "Bipropellant Propulsion Performance and Propellant-Remaining Prediction for INSAT-1B".
Journal Of Spacecraft And Rockets, vol. 30, No. 1, Jan. 1993, New York, pp. 92-101, M. V. Chobotov et al., "Low-Gravity Propellant Gauging System for Accurate Predictions of Spacecraft End-of-Life".
Delepierre-Massue Olivier
Fevrier Claude
Le Torrivellec Pierre
Salome Roland
Centre National d'Etudes Spatiales
Wiggins J. David
Williams Hezron
LandOfFree
Device for pressurizing a unified two-liquid propulsion subsyste does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for pressurizing a unified two-liquid propulsion subsyste, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for pressurizing a unified two-liquid propulsion subsyste will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1323004