XIPS: The Latest Thrust in Propulsion Technology

ETI is the world leader in the development and production of xenon ion thrusters and associated power processors. ETI's xenon ion propulsion system (XIPS) equipment is used exclusively for on-orbit station keeping of Boeing Satellite Systems' 702 commercial communications satellites. We are the center of excellence in electric propulsion technology for L-3, with a heritage of more than 40 years of design experience beginning at the Hughes Research Laboratory, and production experience of over 70 thrusters in use on 18 satellites.

ETI has a dedicated staff of engineers and scientists, production facilities for ion thrusters and power processors, and an unequalled thermal vacuum test facility. We are also developing advanced thruster and power processor technologies and designs for the next generation of longer life, higher power XIPS.

Electric Propulsion Products

ETI offers two qualified ion propulsion designs, the 25cm, 4.5kW thruster and power processor used for the BSS satellites, and the NSTAR 30cm, 2.3kW thruster and power processor used for the Deep Space 1 spacecraft.
Our capabilities and products include:

We also offer our technical expertise to assist with XIPS integration and operation on new satellites.

25cm Xenon Ion Propulsion System (XIPS)

The 25cm XIPS is used on all Boeing 702 commercial communications satellites. The 25cm XIPS provides all on-station orbit and attitude control using the thruster low power mode:

	N-S and E-W station keeping
	Attitude control
	Momentum dumping

XIPS can also be used for orbit raising and station changes using the thruster in the high power mode.

The 25cm XIPS includes two fully redundant subsystems with 2 ion thrusters and 1 power processor each. The entire on-orbit mission maneuvers can be performed by a single pair of thrusters. These functions are accomplished autonomously with a series of four daily burns providing precise orbit control.

25cm Ion Thruster

The 25cm ion thruster consists of a cylindrical plasma discharge chamber, discharge hollow cathode, 3-ring magnetic cusp plasma confinement, and neutralizer hollow cathode. The three grid ion accelerator utilizes domed molybdenum grids with approximately 11,000 apertures to produce the high purveyance xenon ion beam.

The 25cm thruster is designed to operate at two different power levels. The high power mode utilizes about 4.5kW of input power to produce a 1.2kV, 3A ion beam. In this mode the thruster produces 165mN thrust at a specific impulse (ISP) of about 3500 seconds. The high power mode is used exclusively for the orbit insertion phase. Nearly continuous operation in the high-power mode for times of 500 to 1000 hours is required, depending on the launch vehicle and satellite weight.

The low power mode, with a thruster input power of 2.2kW, is used for station keeping. In this mode the thruster produces nominally 79 mN of thrust with an ISP of 3400 seconds. Typical performance of the 25 cm thruster are summarized in the Table below.

Table 1. Typical parameters of the 25 cm XIPS thruster.

The mass of the 25cm thruster is 35 lbs.

Power Processor (XPC) for XIPS

The XIPS power processor (XPC) provides all the electrical inputs and controls the functions and operation of the 25cm thrusters. The XPC functions include:

	Conditioned input voltages to the thruster
	Timing and sequencing for start-up
	Fault protection and grid clearing circuits
	Thruster and XPC telemetry

The XPC consists of seven separate power supplies and operates from a regulated 100V bus input voltage. The efficiency of the XPC is greater than 91%. The XPC measures 8.1 x 21.3 x 13.9inches and has a mass of 46 lbs.

30cm NSTAR Ion Propulsion System

The 30cm ion thruster and power processor for the NSTAR Ion Propulsion System was developed in 1995 - 1997 by Boeing ETI for NASA Glenn Research Center and JPL. NSTAR was developed for use as the primary spacecraft propulsion for NASA deep space exploration missions. The NSTAR ion propulsion system was flown on the Deep Space 1 spacecraft, launched in October 1998, where it performed flawlessly for over 3 years and 16,000 hours of operation.

NSTAR operates over a wide range of thrust and input power with high ISP. This is to accommodate thruster operation when the spacecraft is far from the sun and the available solar power is limited. Thruster operation is remotely programmable from earth, providing mission flexibility.

The NSTAR ion propulsion system is scalable to higher powers and higher thrusts by using several thrusters and PPUs. For the Deep Space 1 mission, only a single thruster and PPU was used.

30cm NSTAR Ion Thruster

The 30cm ion thruster is designed for the minimum mass, without significant compromises in performance. The thruster consists of a lightweight discharge chamber with conical/cylindrical geometry. A three ring-cusp magnetic circuit with no iron flux return (lower mass) is used. The ion accelerator assembly uses two domed molybdenum grids. The discharge and neutralizer hollow cathode assemblies are similar to those used in the 25cm thruster.


The 30cm thruster operates anywhere within a wide range of input power (0.5kW to 2.3kW) and thrust (92mN to 19mN). Thruster ISP varies from 3280s at the highest input power to 1950s at the lowest input power. The thruster operating point is controlled by the power processor. Typical thruster performance is shown in Table 2.

Table 2. 30cm NSTAR ion thruster performance

The NSTAR thruster is designed to meet the typical shock and vibration environments of several launch vehicles including the Delta 7920. Random vibration qualification levels (with force limiting) are 13grms. A detailed computer structural model of the thruster was developed to predict the resonance modes and stresses. This model was used to ensure that the design safety margins for mechanical stresses within the thruster were acceptable. Extensive thruster vibration testing was also performed to validate the computer model.

The NSTAR thruster is designed to be thermally isolated from the spacecraft and self cooled during operation. There is very little heat conduction in or out of the thruster. Radiation is the dominant cooling mechanism. As a result, internal thruster temperatures reach high levels during operation. When the thruster is off, radiation to deep space causes the thruster temperature to drop below -100C. Qualification temperatures, measured at the front mask (near the ion beam exit plane), are +153C to -109C.

NSTAR Power Processor

The NSTAR power processor (PPU) provides six conditioned electrical outputs to the thruster, as well as telemetry and fault protection. The beam, accelerator grid and discharge supplies are

variable to operate the thruster over the required range of performance. The PPU interfaces with a digital control interface unit that sets the specific thruster operating conditions and sequences and also controls the propellant feed system. The PPU input bus voltage comes directly from the solar array and can vary from 80V to 160V.

Table 3. Typical characteristics of the NSTAR PPU