Magnetic pumping of whistler waves by tether current modulation

Magnetic excitation of whistlers by a square array of electrodynamic tethers is discussed. The array is made of perpendicular rows of tethers that carry equal, uniform, and time-modulated currents at equal frequency with a 90° phase shift. The array would fly vertical in the orbital equatorial plane, which is perpendicular to the geomagnetic field B0 when its tilt is ignored. The array radiates a whistler wave along B0. A parametric instability due to pumping by the background magnetic field through the radiated wave gives rise to two unstable coupled whistler perturbations. The growth rate is maximum for perturbations with wave vector at angles 38.36° and 75.93° from B0. For an experiment involving a wavefront that moves with the orbiting array, which might serve to study nonlinear wave interactions and turbulence in space plasmas, characteristic values of growth rate and parameters, such as the number of tethers and their dimensions and distances in the array, are discussed for low Earth orbit ambient conditions.

The radiation impedance of electrodynamics tethers in a polar Jovian orbit

Juno, the second mission in the NASA New Frontiers Program, will both be a polar Jovian orbiter, and use solar arrays for power, moving away from previous use of radioisotope power systems (RPSs) in spite of the weak solar light reaching Jupiter. The power generation at Jupiter is critical, and a conductive tether could be an alternative source of power. A current-carrying tether orbiting in a magnetized ionosphere/plasmasphere will radiate waves. A magnitude of interest for both power generation and signal emission is the wave impedance. Jupiter has the strongest magnetic field in the Solar Planetary System and its plasma density is low everywhere. This leads to an electron plasma frequency smaller than the electron cyclotron frequency, and a high Alfven velocity. Unlike the low Earth orbit (LEO) case, the electron skin depth and the characteristic size of plasma contactors affect the Alfven impedance.

Tether radiation in Juno-type and circular-equatorial Jovian orbits

Wave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determine the current in the overall tether circuit. In a cold plasma model, radiation occurs mainly in the Alfven and fast magnetosonic modes, exhibiting a large refraction index. The radiation impedance of insulated tethers is determined for both modes and either mission. Unlike the Earth ionospheric case, the low-density, highly magnetized Jovian plasma makes the electron gyrofrequency much larger than the plasma frequency; this substantially modifies the power spectrum for either mode by increasing the Alfven velocity. Finally, an estimation of the radiation impedance of bare tethers is considered. In LJO, a spacecraft orbiting in a slow downward spiral under the radiation belts would allow determining magnetic field structure and atmospheric composition for understanding the formation, evolution, and structure of Jupiter. Additionally, if the cathodic contactor is switched off, a tether floats electrically, allowing e-beam emission that generate auroras. On/off switching produces bias/current pulses and signal emission, which might be used for Jovian plasma diagnostics.

T-REX: Bare electro-dynamic tape-tether technology experimetn on sounding rocket S520

The project to verify the performance of space tether technology was successfully demonstrated by the launch of the sounding rocket S520 the 25tu. The project is the space demonstration of science and engineering technologies of a bare tape electrodynamic tether (EDT) in the international campaign between Japan, USA, Europe and Australia. Method of "Inverse ORIGAMI (Tape tether folding)" was employed in order to deploy the bare tape EDT in a short period time of the suborbital flight. The deployment of tape tether was tested in a various experimental schemes on ground to show high reliability of tape tether deployment. The rocket was launched on the summer of 2010 and deployed a bare electro-dynamic tape tether with length 132.6 m, which is the world record of the length deployment of tape tether. The verification of tether technology has found a variety kind of science and technology results as the first in the humankind and will lead a large number of applications of space tether technologies

On the formation of nitrogen oxides in the combustion processes of hydrogen in air

A research programme is being carried out at the Institute Nacional de Tecnica Aeroespacial of Spain, on several aspects of the formation of nitrogen oxides in continuous flow combustion systems, considering hydrogen and hydrocarbons as fuels. The research programme is fundamentally oriented on the basic aspects of the problem, although it also includes the study of the influence on the formation process of several operational and design variables of the combusters, such as type of fuels, fuel/air ratio, degree of mixing in premixed type flames, existence of droplets as compared with homogeneous combustion.This problem of nitrogen oxides formation is receiving lately great attention, specially in connection with automobile reciprocating engines and aircraft gas turbines. This is due to the fact of the increasing frequency and intensity of photochemical hazes or smog, typical of urban areas submitted to strong solar radiation, which are originated by the action on organic compounds of the oxidants resulting from the photochemical decomposition of nitrogen dioxide N02. In the combustion process almost all nitrogen oxides are in form of NO. This nitric oxide reacts with the oxygen of the air and forms N02, this reaction only taking place in or near the exhaust of tne motors, since the N0-02 reaction becomes frozen for the concentration existing in the atmosphere.

Self-similar deflagration in laser half-plasmas

The self-similar motion of a half-space plasma, generated by a linear pulse of laser radiation absorbed anomalously at the critical density, has been studied. The resulting plasma structure has been completely determined for [pulse duration (critical density)maximum irradiation] large enough

New electrodynamic tether technology

New Electrodynarnic Tether Technology (NETT) is an experiment we proposed to ESA as part of the Columbus Precursor Flights. It was designed to fly as an exposed payload in the Spacelab carrier. Its primary objective is performance testing for the innovative bare tether concept. The experiment also includes two scientific objectives, specific for uninsulated tethers: i) detection of artificial auroral effects produced by secondary electron emission, and ii) detection of VLF wave emission. Additional objectives of the project are space performance of an electron-emitting hollow cathode and engineering verification of an open-loop deployment strategy.

Science with an electrodynamic tether

Ionospheric interaction experiments using a conductive, fully bare tether are discussed. With an optimal design, requiring 1.15 mm diameter and 7.5 km full length for a collected current of 0.87 A at day conditions, the tether radiates 0.33 watts as Fast Magnetosonic waves and 0.16 watts as Alfven waves. Secondary keV electrons are produced over a 6.5 km length, giving raise to noticeable auroral effects in the D-layer, at low geomagnetic latitudes. A preliminary design of the experiment, to be implemented on either a satellite or a Station, has been carried out. An ejector gives an initial velocity to an end mass, a free spool of tether unwinding from that mass during a first stage of deployment; other phases are monitored through the tether velocity, driving a reel with an unwinding device.

Short, high current electrodynamic tether

An electrodynamic tether experiment, to be carried out in the Russian spacecraft Almaz, is proposed. A 10 km tether would be deployed downwards; the lower 8 km would be nonconductive, the upper 2 km would be conductive, bare, and 2.2 mm in diameter, and would act as a thruster, with power supply at the top. This hybrid arrangement allows for other, onelectrodynamic experiments,reducing costs; it also limits the induced electromotive force, reducing the power to be handled. The current-voltage characteristic of contactors would be measured. With the anode switched off, the wire itself should collect a current over 5 A at day conditions, providing a thrust of 0.11 N at a 0.77 kW power.

Magnetantrieb für Raumfahrzeuge

Einfache Metallseile könnten Raumfahrzeuge mit billigem Strom versorgen, zu Antrieb und Steuerung beitragen und der Besatzung die Annehmlichkeiten künstlicher Schwerkraft verschaffen. Dahinterstecken elementare Naturgesetze aus Mechanik und Elektrodynamik

An anodeless (bare) tether experiment

NETT (New Electrodynamic Tether Technology) is an experiment proposed to ESA in 1991 as part of the Columbus Precursor Flights. It was originally intended to fly as an exposed payload in the Shuttle cargo bay. The main purpose was to demonstrate the electrodynamical capabilities of the innovative "bare tether" concept. The proposed conceptual design was recommended by a Scientific Panel of ESA, meeting in Heidelberg in March 1992. Unfortunately, the Precursor Flights have all but been scuttled, particularly as far as exposed payloads are concerned. The experiment, horever, is being considered in accomodation studies (APLSS, PIERS) for the European modulus of the future Space Station. Additionally, it might be possible to fly the bare tether in a Russian spacecraft.