11 Application of Low-Power Pulse Plasma Thrusters in Thrust Units …
151
system designed for the mentioned purpose: EPS of “EO-1” satellite [13] and its
analog, APPT-120 developed at the RIAME MAI [7]. EO-1 and APPT-120 belong to
the same class of thrust and power consumption. Some difference in individual characteristics is explained by different schemes of the discharge channel. An extremely
low impulse bit (of the order of 0.5 … 1.0 mN s) is interesting, which makes thrusters
of this type the most promising for fine attitude control systems of SSC.
11.6 Immediate Opportunities for Further Development
of Electric Propulsion with Ablative Pulse Plasma
Thrusters
At present, APPT-based Corrective Electric Propulsion System (CEPS) of
autonomous remote-sensing small spacecraft, which has high thrust and power, massand-size characteristics, is being developed at the RIAME MAI. APPT CEPS continuing the line of development of APPT-45–2 and APPT-250 refers to the same size
of propulsion systems in terms of power consumption, thrust, and total pulse. One
of the main characteristics of a pulsed plasma thruster, which determines its size
and technical appearance, is the discharge energy (energy content) of a capacitor
energy storage unit. It was shown in [18] that the most promising way to improve
the mass-and-size characteristics of an electric propulsion system based on APPT is
to make a capacitor energy storage unit less heavy by optimizing its energy content
and using power capacitors with increased energy storage density. Optimization of
the energy content of the capacitor bank can reduce the total mass of the electric
propulsion system by 10 … 15%.
In the aforementioned paper, the structural diagram of the propulsion system based
on APPT is analyzed and the estimative calculations of CEPS total mass depending
on the discharge energy are performed for the following given total pulse J values:
10 kN s, 30 kN s, 50 kN s, and for the energy storage density of the capacitors ω C
= 28 J/kg, which corresponds to the lightest of the currently used capacitors of the
MSR25 type produced by ICAR (Italy) and domestic pulse capacitors by Nukon.
The calculation results are shown in Fig. 11.6.
We can see from the diagrams presented in Fig. 11.6 that the discharge energy
of the available APPT-based CEPS models (the diagrams show the experimental
points corresponding to APPT-155 and APPT-95) are significantly higher than the
optimum one from the point of view of obtaining the minimum mass of EPS. The
RIAME MAI experience in APPT development and testing shows that a decrease in
discharge energy is accompanied by an increase in the thrust cost (C T ). Sometimes the
C T value is of great importance for a low-power SSC. The experimentally obtained
dependence of the thrust cost C T of flight models of APPT-based propulsion systems
on the discharge energy is shown in Fig. 11.7.
Taking into account the above analysis of the influence of the energy content of the
capacitor bank on the total mass of the electric propulsion system when developing
151
system designed for the mentioned purpose: EPS of “EO-1” satellite [13] and its
analog, APPT-120 developed at the RIAME MAI [7]. EO-1 and APPT-120 belong to
the same class of thrust and power consumption. Some difference in individual characteristics is explained by different schemes of the discharge channel. An extremely
low impulse bit (of the order of 0.5 … 1.0 mN s) is interesting, which makes thrusters
of this type the most promising for fine attitude control systems of SSC.
11.6 Immediate Opportunities for Further Development
of Electric Propulsion with Ablative Pulse Plasma
Thrusters
At present, APPT-based Corrective Electric Propulsion System (CEPS) of
autonomous remote-sensing small spacecraft, which has high thrust and power, massand-size characteristics, is being developed at the RIAME MAI. APPT CEPS continuing the line of development of APPT-45–2 and APPT-250 refers to the same size
of propulsion systems in terms of power consumption, thrust, and total pulse. One
of the main characteristics of a pulsed plasma thruster, which determines its size
and technical appearance, is the discharge energy (energy content) of a capacitor
energy storage unit. It was shown in [18] that the most promising way to improve
the mass-and-size characteristics of an electric propulsion system based on APPT is
to make a capacitor energy storage unit less heavy by optimizing its energy content
and using power capacitors with increased energy storage density. Optimization of
the energy content of the capacitor bank can reduce the total mass of the electric
propulsion system by 10 … 15%.
In the aforementioned paper, the structural diagram of the propulsion system based
on APPT is analyzed and the estimative calculations of CEPS total mass depending
on the discharge energy are performed for the following given total pulse J values:
10 kN s, 30 kN s, 50 kN s, and for the energy storage density of the capacitors ω C
= 28 J/kg, which corresponds to the lightest of the currently used capacitors of the
MSR25 type produced by ICAR (Italy) and domestic pulse capacitors by Nukon.
The calculation results are shown in Fig. 11.6.
We can see from the diagrams presented in Fig. 11.6 that the discharge energy
of the available APPT-based CEPS models (the diagrams show the experimental
points corresponding to APPT-155 and APPT-95) are significantly higher than the
optimum one from the point of view of obtaining the minimum mass of EPS. The
RIAME MAI experience in APPT development and testing shows that a decrease in
discharge energy is accompanied by an increase in the thrust cost (C T ). Sometimes the
C T value is of great importance for a low-power SSC. The experimentally obtained
dependence of the thrust cost C T of flight models of APPT-based propulsion systems
on the discharge energy is shown in Fig. 11.7.
Taking into account the above analysis of the influence of the energy content of the
capacitor bank on the total mass of the electric propulsion system when developing