Advanced Space Propulsion Research Articles

Test of a miniature double-focusing mass spectrometer for real-time plasma monitoring

A miniature double-focusing mass spectrometer with an 8 mm radius was tested at the Advanced Space Propulsion Laboratory (ASPL) at NASA Johnson Space Center (JSC). The purpose of these experiments was to provide residual gas-analysis and single-ion-monitoring capabilities for the vacuum chamber where NASA's new plasma propulsion system, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), is being developed. The instrument used here was an alpha (α) version of the Integrated Leak Detector System (ILD 50) and represents a smaller version of the original 20 mm-radius Compact Double Focusing Mass Spectrometer prototype (CDFMS) developed at the University of Minnesota. The instrument successfully provided gas-composition information on the vacuum test chamber and several different plasma formulations, provided resolving powers close to the theoretical value of 40 at full width half maximum (FWHM) and demonstrated an operational mass range of 1–50 Da.

Design and fabrication of an HTS magnet for the VASIMR experiment

An International Team consisting of DuPont Superconductivity, Oak Ridge National Lab, the Advanced Space Propulsion Laboratory, and Sumitomo Electric Industries, Ltd. has designed and fabricated a conduction-cooled High Temperature Superconducting (HTS) coil for use in the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). The HTS coil will be installed and tested in the ongoing VASIMR experiment at the Advanced Space Propulsion Laboratory at the Johnson Space Center in Houston, TX. The HTS coil is 0.04 m in length, with a 0.23 m inner diameter, and has a mass less than 5.0 kg. The central operating magnetic field is a nominal 0.28 T with a design operating current of /spl sim/105 A. The HTS coil is conduction cooled with a nominal operating temperature of 40 K. The HTS conductor uses a Bi-2223 material with a stainless steel backing strip for reinforcement. Details and test results of the mechanical, thermal, and electromagnetic analyses are discussed.

A study of plasma propulsion system with RF heating

Some experiments and computer simulations to develop a plasma propulsion system by using electron and ion cyclotron resonance (EICR) plasma are reported. The EICR thruster is an advanced space propulsion concept that has possible uses in satellite station keeping and interplanetary travel. An experimental apparatus to generate EICR plasma was constructed in 1999. It consists of a cylindrical vacuum chamber (inner diameter of 21 cm and axial length of 150 cm), RF power supply, and eight electromagnets. It is run at a pressure in the 10 −2 Pa range with Ar or He gas as propellant. This experiment aims to generate plasma (without electrode) by ECR and to accelerate ions (without grid) by ICR under a proper magnetic field configuration. We also plan to develop a compact ECR plasma source that uses hot electron ring for ion acceleration.

Experimental Status of the Development of a Variable Specific Impulse Magnetoplasma Rocket

The Advanced Space Propulsion Laboratory (ASPL) is developing a Variable Specific Impulse Magnetoplasma Rocket (VASIMR) using a Radio Frequency (RF) heated magnetic mirror operated asymmetrically. The system comprises of three stages: 1) plasma ionization and injection into the magnetic system; 2) ion heating by action of Ion Cyclotron Resonance Heating (ICRH); 3) plasma exhaust through a magnetic nozzle. The central experimental device is a small versatile tandem mirror configured system. The system can also be easily reconfigured to operate as a simple mirror. The total length of the device is 3.2 m, and the maximum magnetic field is 3.0 T. The exhaust end connects to a 5 m vacuum chamber where we are installing a 40,000 liter/second pumping capacity. Radio frequency power is available at approximately 3 MHz at up to 200 kW. A set of plasma diagnostics is being developed and installed, starting with two fast reciprocating probes, one quadruple Langmuir and one Mach.2 We are now evaluating the use of a helicon3 RF plasma source for an efficient ionization stage of the system. Initial results from experiments using a single double-half turn antenna are presented. In addition, we are exploring the use of a Lorentz Force Accelerator (LFA) as a plasma injector source.4

Antimatter-driven fusion propulsion scheme for solar system exploration

The potential use of the proton-antiproton annihilation reaction as a driver for an inertially confined, magnetically insulated fusion plasma with application to advanced space propulsion is examined. The fusion scheme utilized is the magnetically insulated inertial confinement fusion (MICF) concept which combines the favorable aspects of both inertial and magnetic fusions into one. Using an appropriate set of governing equations for the fusion plasma, along with those that detail the annihilation reactions and the energy deposition by the annihilation products including contributions from muon catalysis, we calculate the energy gain for the system as well as the amount of antihydrogen needed to ignite the plasma. We find about 13 ng of antihydrogen are needed to supply a megajoule of energy to the plasma, and about 10 g will be needed for a 220-mT space vehicle to make a one-way trip to Mars in about 2 months. I. Introduction I N several previous publications1-3 we examined the potential use of the magnetically insulated inertial confinement fusion (MICF) concept as a propulsion device that could be utilized in solar explorations and/or interplanetary travel. The concept in question combines the favorable aspects of both magnetic and inertial fusions in that physical containment of the hot plasma is provided by a metallic shell while its thermal energy is insulated from the material wall by a strong, self-generated magnetic field as illustrated in Fig. 1. Unlike the conventional implosion-type inertial fusion schemes, energy production in this approach does not require compression of the fusion fuel to many times solid-state densities and simultaneous delivery of energy to the core to initiate the burn. Instead the fusion plasma is created through wall ablation by an incident laser beam that enters the target through a hole. The same laser gives rise to the strong magnetic field through a process known as the thermoelectric effect, whereby it can be shown that such a field can be generated in a hot plasma when its density gradient is perpendicular to its temperature gradient. We have seen that MICF is capable of producing specific impulses of several thousand seconds and thrusts of tens of kilonewtons that would allow round trips to Mars, for example, to be made in relatively short periods (a few months) even when the massive power supply system for the laser driver is carried on board. It is clear that such travel times can be substantially reduced if the power supply component is eliminated from the dry weight of the vehicle. Several recent studies4 have proposed beaming the needed energy from an Earth-orbiting space station, but it is evident that a more reliable performance can be assured if a compact energy source is taken along. Clearly no source can match that of matter-antima tter annihilation reactions since such a fuel (e.g., anti-hydrogen) possesses the largest specific energy, i.e., energy per unit mass, provided, of course, that the technology for producing, storing, and manipulating such

Materials for advanced space propulsion systems

The potential for improved performance in advanced space propulsion systems through innovative application of advanced materials is discussed. The importance of a high-to-weight ratio, together with high temperature capability is examined, as also is the need for high thermal conductivity in actively cooled structures. Many advanced space propulsion systems are hydrogen fueled, making hydrogen compatibility a major requirement. The performance of candidate materials in high pressure hydrogen environments is discussed at length, and promising systems are identified.

Probabilistic Structural Analysis for Advanced Space Propulsion Systems

This paper reports on recent extensions to ongoing research into probabilistic structural analysis modeling of advanced space propulsion system hardware. The advances concern probabilistic dynamic loading, and probabilistic nonlinear material behavior. In both cases, the reported work represents a significant advance in the state-of-the-art for these topics. Random, or probabilistic loading is normally concerned with the loading described in power spectral density (PSD) terms. The current work describes a method for incorporating random PSD’s along with random material properties, damping, and structural geometry. The probabilistic material response is concerned with the prediction of nonlinear stress-strain behavior for physical processes that can be linked to the original microstructure of the material. Such variables as grain size and orientation, grain boundary strength, etc., are treated as random, initial variables in generating stochastic stress-strain curves. The methodology is demonstrated for a creep simulation.

Probabilistic structural analysis methodology and applications to advanced space propulsion system components

The development of reliability-based design methods requires the development and use of general purpose structural analysis tools that predict the uncertainty of structural response due to uncertainties in a full range of design conditions. The goal of the reported work has been to develop and apply new technology that will enable the designer to efficiently and accurately account for each of the design sources of uncertainty as it might affect structural reliability and risk assessment. The paper discusses the development of the NESSUS ™ (Numerical Evaluation of Stochastic Structures Under Stress) finite element code and its supporting reliability algorithms. The elements of the solution strategy are outlined and application is made to several propulsion system components.

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NASA selects new space research centers

The National Aeronautics and Space Administration (NASA) announced the selection of seven new Centers for the Commercial Development of Space (CCDS) on July 28, 1987. The centers will be eligible for NASA grants of as much as $1 million annually for the next 5 years to carry on scientific and technical research related to the commercial development of space. The locations and concentrations of the new centers are as follows: The University of Tennessee Space Institute‐Center for Advanced Space Propulsion, Tullahoma, Tenn. Auburn University‐Center for the Commercial Development of Space Power, Auburn, Ala. Environmental Research Institute of Michigan—Center for the Commercial Development of Autonomous and Man‐Controlled Robotic Sensing Systems in Space, Ann Arbor, Mich. Pennsylvania State University‐Center for Secretion Research, University Park, Penn. University of Colorado‐Center for Bioserve Space Technologies, Boulder, Colo. Case Western Reserve University‐Center on Materials for Space Structures, Cleveland, Ohio. Texas A&M Research Foundation‐Center for Commercial Development of Space Power, College Station, Tex.