Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
  • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
  • B64G1/26—Guiding or controlling apparatus, e.g. for attitude control using jets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
  • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
  • B64G1/242—Orbits and trajectories
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
  • B64G1/64—Systems for coupling or separating cosmonautic vehicles or parts thereof, e.g. docking arrangements
  • B64G1/646—Docking or rendezvous systems

Definitions

• the present invention relates to a spacecraft, a spacecraft guidance system and a method for operating the spacecraft.
• the spacecraft is for example a satellite, a probe, a space shuttle or a refueling module.
• the orbiting of an interplanetary probe around a planet or the maintenance in formation of a satellite swarm also includes a phase of approaching an orbital position.
• the trajectory of a spacecraft, or fighter, in a phase of approach of an orbital position, or target is determined thanks to the equations of HiIl, sometimes still called equations of Clohessy-Wiltshire.
• the spacecraft after a so-called Hohmann transfer made from a low orbit, under the effect of a brief pulse F. ⁇ t (with in particular ⁇ t ⁇ 0.5 second) generated using a jet of gas or compressed liquid, undergoes a very small variation in its orbital velocity ⁇ v (between 10 "1 to 10 " m / s).
• the motion of the spacecraft is determined by geodetic deflection equations whose HiIl equations are a special case.
• the fighter and the target may be at relative rest on the same orbit, known as the parking orbit. Two parking positions are possible, in front of or behind the target in relation to its orbital movement.
• the relative position of the fighter and the target is not static and the HiIl radial equation shows that the fighter is gravitational with a gradient which is centrifugal when the fighter is above the parking orbit and centripetal when the fighter is below that orbit.
• the application EP 0 467 671 A2 discloses a method for making up the trajectory of an appointment by exerting successive pulses.
• Spacecraft Vol. 39, No. 5, concerns the final approach, made by a space engine, of a target, when the craft is at a distance of less than 100 m.
• the approach of the target is carried out by exerting impulses then a retromanoeuvre takes place at the end of the approach.
• Application US 2004/0026571 A1 discloses satellite navigation and guidance systems.
• the invention proposes in particular a new way of controlling a spacecraft in order to bring it closer to a target, which is for example another spacecraft, notably a satellite, a space station, a probe, or a place of an orbit.
• the invention thus relates, according to one of its aspects, to a spacecraft comprising: a propulsion system making it possible to exert on the spacecraft a force of variable intensity and orientation, a control system arranged to control the propulsion system in intensity and orientation so as to bring the spacecraft closer to a target around a planet.
• the force exerted by the propulsion system depends, in intensity and / or orientation, the coordinates of the spacecraft in the rotating reference linked to the target.
• This force can be of variable orientation and variable intensity, the orientation and the intensity being for example continuously modified.
• the force may have at least one component f x , f y or f z in the rotating reference frame linked to the target which varies, in particular substantially linearly, with the corresponding coordinate x, y or z of the apparatus in this reference, in particular which it is proportional.
• the force may have at least two components f x , f y or f z in the target-related rotational coordinate system which vary substantially linearly with corresponding coordinates x, y or z of the apparatus in this frame, in particular two coordinates, and which are, for example, proportional to them.
• the third component may be zero, for example.
• Such a force, directed substantially towards the target or substantially radial and directed towards the target, applied to the spacecraft, can make it possible to stabilize the movement of the spacecraft in the vicinity of the target and to reduce the duration of the phase of the spacecraft. 'approach.
• This force, exerted in the orbital plane of the target can be likened to a 'restoring force.
• the propulsion system comprises, if desired, at least one electric thruster, in particular a Hall effect thruster or, alternatively, an ion gate thruster.
• An electric thruster generally has a lower initial mass than a chemical thruster of equivalent thrust, which reduces the onboard weight of the spacecraft and therefore the launch costs.
• An electric thruster can also be used to accurately control the spacecraft's trajectory and reduce the duration of the approach phase, thanks to low thrusts.
• the propulsion system comprises at least one chemical thruster.
• the propulsion system is arranged to produce a thrust of between about 10 mN and 5 N, for example greater than 50 mN or 100 mN.
• the propulsion system can be arranged so that at least one of the intensity and the orientation of the force can be changed continuously or, alternatively, in increments.
• the intensity and / or orientation of the force can be controlled, if desired, by the addition of an external magnetic field.
• the propulsion system may comprise, where appropriate, a steerable support on which is disposed at least one propellant. This steerable support can be moved to change the orientation of the force applied to the spacecraft. The orientation may depend on the coordinates of the machine in the reference linked to the target.
• the spacecraft comprises several thrusters arranged at different locations of the spacecraft so as to vary, by a selective start of the various thrusters, the intensity and the orientation of the resulting force exerted on the spacecraft.
• the control system can be arranged to control the propulsion system in intensity and orientation so that, in a first approach phase of the spacecraft of the target, the spacecraft describes a substantially epicyclic trajectory in the rotating center mark coinciding with the target.
• the control system may be arranged so that the force exerted on the space vehicle, during the first approach phase, is directed substantially towards the target, the force having an intensity substantially proportional to the distance between the spacecraft and the target.
• This force is a collinear force to the vector ray joining the spacecraft to the target and directed towards the target, its intensity and its direction being chosen in particular to compensate the radial centripetal force that the spacecraft undergoes in the vicinity of the target.
• This force has a centripetal component tangentially to the orbit. This allows the spacecraft, especially when it is below or above the target, to get closer to it.
• control system may be arranged so that the force exerted on the spacecraft, during the first approach phase, is substantially radial and directed towards the target, the force having an intensity substantially proportional to the difference in altitude between the spacecraft and the target.
• This radial force allows in particular the spacecraft which is behind or in front of the target, to get closer to it.
• the spacecraft can be brought a few tens of meters from the target, for example at a distance of less than 100 m or 50 m.
• control system is arranged to control the propulsion system in intensity and orientation so that, in a second approach phase of the spacecraft of the target, succeeding the first phase, the spacecraft describes a trajectory substantially in a circular arc, in particular in a semicircle, in the rotating reference center coinciding with the target, the force exerted on the spacecraft being substantially radial and directed towards the target, the force having an intensity substantially proportional to the difference in altitude between the spacecraft and the target.
• This force makes it possible to bring the spacecraft closer to the target at a distance of less than a few meters, for example less than 1 m.
• a guidance system for guiding a spacecraft in order to bring it closer to a target around a planet comprising a propulsion system making it possible to exerting on the spacecraft a force of variable intensity and orientation and a control system arranged to control the propulsion system
• the guidance system comprising: a remote data transmission system arranged to transmit to the control system the spacecraft data useful to enable it to control the propulsion system in intensity and orientation to bring the spacecraft closer to the target, using a force that for example is:
• the data transmission system may be disposed at least partially: on a planet, and / or on another spacecraft such as a space station, this other spacecraft may in particular define the target.
• the data transmission system can be arranged to transmit, in particular in real time, to the control system of the spacecraft data relating to the distance between the spacecraft and the target. This distance is determined for example by a measuring system disposed on the surface of the planet around which the spacecraft gravitates.
• the spacecraft comprises at least one measurement system arranged to determine the distance separating it from the target.
• the control system of the spacecraft can be arranged to calculate the intensity and / or the orientation of the force to be generated by the propulsion system in the approach phase, which allows autonomous control of the machine spatial.
• the calculation of the intensity and / or the orientation of the force to be generated is achieved using the guidance system, for example based on the ground or embarked on another spacecraft.
• the invention further relates, in one aspect, to an assembly comprising the spacecraft and the guidance system.
• Another object of the invention is, according to another of its aspects, a method for operating a spacecraft in order to bring it closer to a target around a planet, comprising the step of: acting on a propulsion system of the spacecraft so as to exert a force which for example is:
• FIG. 1 schematically represents a rotating center mark coinciding with a target
• FIG. 2 represents, schematically and partially, a spacecraft according to the invention
• FIGS. 3 and 4 show, schematically and partially, two examples of a guidance system arranged to guide a spacecraft
• FIGS. 5 to 7 schematically illustrate various examples of the trajectory of a spacecraft according to the invention, in FIG. an approach phase of the target.
• the target is for example materialized by a space station orbiting the Earth.
• the circular orbit is centered on a point O ', corresponding substantially to the center of the planet.
• the spacecraft P of negligible mass m in front of M, is located in the original rotating reference mark O with three axes: O-axis radially outward, Oy tangent to the target's orbit in the direction of movement, and Oz perpendicular to the plane (Oxy). Equations of the movement of the spacecraft
• the spacecraft P is in the vicinity of the target O (for example a few kilometers).
• V 1 will be imposed.
• the final approach of the spacecraft P towards the target can be done in two directions: radial or orthoradial.
• EXAMPLE 1 An example of a vertical catch-up approach phase allowing the spacecraft below the station to approach it, using the solutions of the system of equations (FIG. ).
• the approach is radial.
• the radial force T above has an intensity proportional to the difference in altitude between the spacecraft and the target.
• the epicyclic trajectory of the spacecraft in the approach phase is illustrated in Figure 6.
• the approach is orthoradial.
• a second phase of approach is implemented to reduce the distance between the spacecraft and the target to allow, if necessary, stowage maneuvers or "docking".
• the maximum thrust required for a distance of 4 m and a satellite of 1000 kg is for example equal to approximately 15.6 n ⁇ N.
• the trajectory of the spacecraft for example over a quarter of an orbital period, in the second approach phase, is semi-circular, as illustrated in FIG.
• the force is defined by: where A is a positive constant positive force, hence:
• trajectory is an epicycloid on which the hunter moves in the direction of the positive x or the negative x according to the sign of ⁇ .
• FIG. 2 shows an example of the spacecraft P formed by a satellite orbiting the Earth.
• the spacecraft P may, alternatively, be a refueling module of a space station or an interplanetary probe.
• the spacecraft P comprises a propulsion system 1 for exerting on the spacecraft P a force of varying intensity and orientation.
• the propulsion system 1 comprises an electric thruster, in particular a Hall effect thruster.
• Hall effect thrusters include, for example, the SPT100, PPS1350, PP55000 thrusters manufactured by SNECMA, or the T-40, T-140, T200 and T220 T thrusters manufactured by PATT & WHITNEY.
• the electric thruster may be a grid propellant, for example the T5 or T6 propellant developed by Qinequq.
• the electric thruster 1 may for example produce a thrust of maximum intensity of about 2 N.
• the propulsion system may comprise at least one chemical thruster, provided for example with a turbopump, or a propellant with pressurized fluid and equipped with a centrifugal turbopump type Couette-Taylor both arranged to produce a variable thrust.
• the propulsion system 1 is arranged so that at least one of the intensity and orientation of the force can be changed continuously.
• the propulsion system 1 can be arranged so that at least one of the intensity and the orientation of the force can be changed in increments.
• the spacecraft P furthermore comprises a control system 2 arranged to control the propulsion system 1 in intensity and orientation so as to bring the spacecraft P closer to the target O by means of a force as defined above.
• the control system 2 may comprise an on-board computer and be arranged to allow autonomous control of the spacecraft in the approach phase, allowing it in particular to calculate the intensity and / or the orientation of the force to provide in this phase of approach.
• the spacecraft P may comprise, for example, a measurement system 3 making it possible to determine the distance separating it from the target O.
• a guidance system 5 may be provided to guide the spacecraft P in order to bring it closer to the target O, this guidance system possibly comprising one or more remote data transmission systems 6 arranged to transmit to the control system.
• control 2 of the spacecraft P useful data to allow control of the propulsion system 1 to have the spacecraft P describe the approach paths of the target O.
• the guidance system may be at least partially on board the space station 7.
• the control system 2 of the spacecraft P can be of relatively simple design since the trajectory calculations of the spacecraft P can be carried out on ground-based computers or embedded in another spacecraft and the data relating to the calculated trajectories are transmitted to the control system 2 of the spacecraft.
• the orbit is circular.

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• Engineering & Computer Science (AREA)
• Remote Sensing (AREA)
• Aviation & Aerospace Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Radar, Positioning & Navigation (AREA)
• Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Family Cites Families (7)

• 2006
  • 2006-02-27 FR FR0650678A patent/FR2897841B1/fr not_active Expired - Fee Related
• 2007
  • 2007-02-27 US US12/279,146 patent/US8262028B2/en not_active Expired - Fee Related
  • 2007-02-27 EP EP07731060A patent/EP1989113A1/de not_active Withdrawn
  • 2007-02-27 WO PCT/FR2007/000358 patent/WO2007096539A1/fr not_active Ceased

Non-Patent Citations (1)

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