Stanley O. Starr

A low voltage “railgun”

Due to recent advances in solid-state switches and ultra-capacitors, it is now possible to construct a “railgun” that can operate at voltages below 20 V. Railguns typically operate above a thousand volts, generating huge currents for a few milliseconds to provide thousands of gs of acceleration to a small projectile. The low voltage railgun described herein operates for much longer time periods (tenths of seconds to seconds), has far smaller acceleration and speed, but can potentially propel a much larger object. The impetus for this development is to lay the groundwork for a possible ground-based supersonic launch track, but the resulting system may also have applications as a simple linear motor. The system would also be a useful teaching tool, requiring concepts from electrodynamics, mechanics, and electronics for its understanding, and is relatively straightforward to construct.

Mass Conservation in Modeling Moisture Diffusion in Multi-layer Composite and Sandwich Structures

Moisture diffusion in multi-layer composite and sandwich structures is difficult to model using finite-difference methods due to the discontinuity in moisture concentration between adjacent layers of differing materials. Applying a mass-conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite/epoxy composite sandwich coupon with a Rohacell® foam core.

A DC Transformer

A component level dc transformer is described in which no alternating currents or voltages are present. It operates by combining features of a homopolar motor and a homopolar generator, both dc devices, such that the output voltage of a dc power supply can be stepped up (or down) with a corresponding step down (or up) in the current. The basic theory for this device is developed, performance predictions are made, and the results from a small prototype are presented. Based on demonstrated technology in the literature, this dc transformer should be scalable to low megawatt levels, but it is more suited to high current than high voltage applications. Significant development would be required before it could achieve the kilovolt levels needed for dc power transmission.

A slowly rotating hollow sphere in a magnetic field: First steps to de-spin a space object

Modeling the interaction of a slowly rotating hollow conducting sphere in a magnetic field provided an understanding of the dynamics of orbiting space objects moving through the Earths magnetic field. This analysis, performed in the late 1950s and limited to uniform magnetic fields, was innovative and acknowledged the pioneers who first observed rotary magnetism, in particular, the seminal work of Hertz in 1880. Now, there is interest in using a magnetic field produced by one space object to stop the spin of a second object so that docking can occur. In this paper, we consider, yet again, the interaction of a rotating hollow sphere in a magnetic field. We show that the predicted results can be tested experimentally, making this an interesting advanced student project. This analysis also sheds light on a rich set of previously unaddressed behaviors involving eddy currents.

Drag and lift forces between a rotating conductive sphere and a cylindrical magnet

Modeling the interaction between a non-uniform magnetic field and a rotating conductive object provides insight into the drag force, which is used in applications such as eddy current braking and linear induction motors, as well as the transition to a repulsive force, which is the basis for magnetic levitation systems. Here, we study the interaction between a non-uniform field generated by a cylindrical magnet and a rotating conductive sphere. Each eddy current in the sphere generates a magnetic field which in turn generates another eddy current, eventually feeding back on itself. A two-step mathematical process is developed to find a closed-form solution in terms of only three eddy currents. However, the complete solution requires decomposition of the magnetic field into a summation of spherical harmonics, making it more suitable for a graduate-level electromagnetism lecture or lab. Finally, the forces associated with these currents are calculated and then verified experimentally.Modeling the interaction between a non-uniform magnetic field and a rotating conductive object provides insight into the drag force, which is used in applications such as eddy current braking and linear induction motors, as well as the transition to a repulsive force, which is the basis for magnetic levitation systems. Here, we study the interaction between a non-uniform field generated by a cylindrical magnet and a rotating conductive sphere. Each eddy current in the sphere generates a magnetic field which in turn generates another eddy current, eventually feeding back on itself. A two-step mathematical process is developed to find a closed-form solution in terms of only three eddy currents. However, the complete solution requires decomposition of the magnetic field into a summation of spherical harmonics, making it more suitable for a graduate-level electromagnetism lecture or lab. Finally, the forces associated with these currents are calculated and then verified experimentally.

Why Major Programs Need Innovation Support Labs: An Example from the Space Shuttle Launch Program at KSC

For over 30 years the Kennedy Space Center (KSC) has processed the Space Shuttle; handling all hands-on aspects from receiving the Orbiter, External Tanks, Solid Rocket Booster Segments, and Payloads, through certification, check-out, and assembly, and ending with fueling, count-down, and launch. A team of thousands have worked this highly complicated, yet supremely organized, process and have, as a consequence, generated an exceptional amount of technology to solve a host of problems. This paper describes the contributions of one team that formed with the express purpose to help solve some of these diverse Shuttle ground processing problems. I. Introduction round processing of the Space Shuttle has occurred at the Kennedy Space Center for over 30 years. This activity has encompassed everything from safing an Orbiter just after landing to launching the completed stack from one of two launch pads. It includes demating an Orbiter from the 747 when it flies in from the west coast, moving External Tanks (ET) from barges to the Vehicle Assembly Building (VAB), and receiving Solid Rocket Booster (SRB) segments from rail cars. It includes detailed processing of an Orbiter in one of three Orbiter Processing Facilities (OPF) to return it to a safe launching configuration, and then within the VAB, stacking the SRB segments, hanging an ET from these SRBs, and finally forming a complete stack by adding the Orbiter; forming a complete Space Shuttle Vehicle. It includes maintenance and processing of launch pads, handling of cryogenic fuels and hypergols, and monitoring of thousands of sensors and cameras needed to ensure that all is well. Finally, it includes safely launching the vehicle.

Launching astronauts: 50 years of electronic checkout and launch systems at the Kennedy Space Center

When NASA was created in 1958 one of the elements incorporated into this new agency was the Army Ballistic Missile Agency (ABMA) in Huntsville, Alabama and its subordinate Missile Firing Laboratory (MFL) in Cape Canaveral. Under NASA, the MFL became the Launch Operations Directorate of the George C. Marshall Space Flight Center in Huntsville, but expanding operations in the build-up to Apollo dictated that it be given the status of a full-fledged center in July, 1962 [1]. The next year it was renamed the John F. Kennedy Space Center (KSC) after the president whose vision transformed its first decade of operation. The ABMA was under the technical leadership of Dr. Wernher von Braun. The MFL was run by his deputy Dr. Kurt Dehus, an electrical engineer whose experience in the field began in the early days of V-2 testing in war-time Germany. In 1952, a group led by Dehus arrived in Cape Canaveral to begin, test launches of the new Redstone missile [2]. During the 1950s, the MFL built several launch complexes and tested the Redstone, Jupiter, and Jupiter C missiles. This small experienced team of engineers and technicians formed the seed from which has grown the KSC team of today. This briefly reviews the evolution, successes, and setbacks of KSC electronic technologies for integration, checkout, and launch of space vehicles and payloads. We show that this very successful technology development was driven by greater vehicle complexity and heavily influenced and constrained by the commercial state-of-the-art in electronics.