Spacecraft with modulated thrust electrostatic ion thruster and associated method
First Claim
1. An electrostatic ion thruster with thrust modulation comprising:
- means for providing a gaseous propellant;
means for ionizing said gaseous propellant to generate a plasma;
means for containing said plasma;
an ion extraction assembly for extracting a beam of positively charged ions from said plasma,said extraction assembly including a screen electrode and an accel electrode, said screen electrode being positioned between said accel electrode and said plasma; and
voltage control means for complementary modulation of the voltage potentials of said screen electrode and said accel electrode such that a substantially constant potential difference is maintained therebetween;
whereby a relatively constant ion beam current is maintained while the thrust from said ion thruster is modulated.
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Accused Products
Abstract
An axial electrostatic ion thruster for use on a dual-spin stabilized spacecraft is disclosed. The thruster is mounted on the spun portion of the spacecraft and continuously fired for an integral number of spin periods to provide north-south velocity and attitude control. To achieve zero attitude precession with a statically imbalanced despun platform, or an intentional attitude precession generally, the ion thrust is spin-synchronously varied between two non-zero levels to achieve a prescribed Fourier component amplitude and phase at the spin frequency. Modulation of the thrust is achieved with constant ion beam current by complementary modulation of the beam voltage, VB, and accel voltage, VA by varying the ion extraction system grid voltages. This varies the thrust while maintaining a constant total accelerating voltage VTOT =VB +|VA |.
71 Citations
13 Claims
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1. An electrostatic ion thruster with thrust modulation comprising:
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means for providing a gaseous propellant; means for ionizing said gaseous propellant to generate a plasma; means for containing said plasma; an ion extraction assembly for extracting a beam of positively charged ions from said plasma, said extraction assembly including a screen electrode and an accel electrode, said screen electrode being positioned between said accel electrode and said plasma; and voltage control means for complementary modulation of the voltage potentials of said screen electrode and said accel electrode such that a substantially constant potential difference is maintained therebetween; whereby a relatively constant ion beam current is maintained while the thrust from said ion thruster is modulated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A dual-spin stabilized spacecraft comprising:
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a nominally despun platform; a nominally spun rotor which rotates relative to said platform about a rotational axis; an electrostatic ion thruster positioned on said rotor off the rotational axis of said rotor for providing axial thrust by generating a charged ion beam; means for modulating the thrust of said ion thruster between an upper thrust value and a lower thrust value; and means for maintaining the ion beam current from said thruster substantially constant for all thrust values. - View Dependent Claims (10, 11)
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12. A method of operating an electrostatic ion thruster including an ion extraction assembly having a screen electrode and an accel electrode, said method comprising the steps of:
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providing a relatively constant flow of a gaseous propellant to an ionization chamber; ionizing said gaseous propellant to generate a plasma of positively charged ions and negatively charged electrons; extracting a beam of positively charged ions from said plasma with said ion extraction assembly by maintaining a positive voltage on said screen electrode and a negative voltage on said accel electrode; and modulating the voltage on said screen and accel electrodes between predetermined bounds while maintaining a substantially constant potential difference between said electrodes; whereby thrust modulation is achieved while maintaining substantially constant ion beam current. - View Dependent Claims (13)
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Specification