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We explore the capability of a VASIMR ® reusable probe "catapult" concept to send a 4000-5000 kg spacecraft to Jupiter on a Hohmann-like transfer orbit, arriving in just 36 months elapsed time. The VASIMR ® performs a slingshot pass close to the Sun and uses the high level of available solar energy to produce a sustained burst of high thrust. Enough kinetic energy is provided to the probe to reach Jupiter orbit within 0.7-1.4 AU. The Catapult release the probe with enough speed to reach Jupiter in three years, and returns to Earth for another mission. This study identifies the important parameters in the probe ejector operation (power level, propellant mass, payload release point, distance of closest approach to the Sun), and scan these parameters to understand and optimize the capabilities of the proposed system. We assume that the Catapult and its payload begin at the Earth's sphere of influence (SOI), and are coasting in the Earth's orbit about the Sun. The VASIMR ® engine's power rating must match the peak power available when the spacecraft is closest to the Sun. The solar array is assumed to be a planar array rather than a concentrator since it will have to operate near the Sun, where a concentrator would overheat photovoltaic cells. The feasibility of not releasing the payload and using the VASIMR ® to provide thrust for the duration of the transfer orbit will also be examined. In this scenario, the VASIMR ® RF generators could serve double duty as radar RF sources.

Extensive testing using the VASIMR ® VX-200 TM experiment at power levels up to 200 kW has established system DC-to-jet power performance while the injected-gas and plasma operated in steady-state conditions. The thruster efficiency, using argon propellant, ranges from 60% to 72% in the I sp domain of 3000 to 5000 s. These tests were performed using highly efficient (~ 95%) and lightweight (< 1 kg/kW) solid-state RF power processing units built by Nautel, Ltd and a cryogen-free superconducting magnet. Detailed mapping of the plasma plume over a large scale length (> 2 m) and low background pressure (< 2×10-4 Torr) has revealed plasma detachment from the system. A recent study has evaluated that a system alpha in the range of 3 kg/kW at high power (~ 250 kW) is achievable with existing technology. A benchmarked physics-based model predicts further improvement in efficiency with argon and efficient (~ 70% system) krypton propellant operation extending down to an I sp of 2000 s. Efficient operation and mass performance is competitive with Hall effect thruster technology at power levels of 50 kW and improves with increasing power. With the physics of the electrical and plasma power flow demonstrated and understood, a progressing effort is to demonstrate the operation in thermal steady-state and long duration testing (> 100 hours). With thermal measurements from VX-200 TM and fluid flow analysis, an active high-temperature (> 200 C) thermal control system meets the power density needs to readily operate a single core VASIMR ® system at up to 250 kW. This paper reviews the state-of-the-art of VASIMR ® technology and describes activities toward testing a spaceflight relevant system in steady-state, a program named VX-200SS. With a thermal solution in hand, the elements of a VASIMR ® system are ready for a straight forward progression to spaceflight. Such a system has many exciting applications using a VASIMR ® Solar Electric Propulsion (VASIMR ®-SEP) spacecraft, such as cislunar cargo, orbital servicing and debris removal, orbital reboost, asteroid redirection, deep space missions and others.

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The VX-200SS program will complete design verification, testing and lifetime estimates of a VASIMR ® prototype engine, operating under thermal steady-state at power levels greater than 100 kW for at least 100 continuous hours. The work will bring the integrated VX-200SS VASIMR ® prototype to Technology Readiness Level of 5 (TRL-5), including RF Power Processing Units (PPUs), superconducting magnet, propellant management system, internal thermal management subsystems and the rocket core. The rocket core element resides down the bore of the magnet and is designed to utilize the RF power in conjunction with the high magnetic field to create and accelerate a high power-density plasma stream and manage any waste heat from the process. The accumulation of significant operating time will allow a measurement of the wear of plasma-facing components with sufficient accuracy to evaluate their projected lifetime. The VX-200SS program builds on the successful VX-200™ program and involves manufacturing of a new rocket core and significant upgrades to the RF subsystems, vacuum chamber, computer control, and performance measurement diagnostics. This paper describes the three-year multi-phase VX-200SS program that has been underway for one year.