Juan R. Sanmartin

Universidad Politécnica de Madrid | UPM · Departamento de Física Aplicada a la Ingeniería Aeronáutica

Past planetary missions have been broad and detailed for Gas Giants, compared to flyby missions for Ice Giants. Presently, a mission to Neptune using electrodynamic tethers is under consideration due to the ability of tethers to provide free propulsion and power for orbital insertion as well as additional exploratory maneuvering --- providing more...

Past planetary missions have been broad and detailed for Gas Giants, compared to flyby missions for Ice Giants. Presently, a mission to Neptune using electrodynamic tethers is under consideration due to the ability of tethers to provide free propulsion and power for orbital insertion as well as additional exploratory maneuvering — providing more mi...

Search for habitability in Outer Planets moons, requires presence of proper chemistry, water, and energy. Dissipation from tidal forces is major energy source in evolution of Icy moon systems, generically exhibiting a multi-layer structure, with outer solid (ice) and intermediate liquid layers, and solid (rocky) core. Saturn moon Enceladus has been...

A low work-function tether (LWT), a subclass of electrodynamic tether made of a conductor partially coated with a low work function material, can exchange momentum and energy with planetary magnetospheres without any consumable. If fed by an onboard power source to reverse the natural direction of the current given by the motional electric field, a...

Saturn, Uranus, and Neptune, among the four Giant Outer planets, have magnetic field B about 20 times weaker than Jupiter. This could suggest, in principle, that planetary capture and operation using tethers, which involve B effects twice, might be much less effective at Saturn, in particular, than at Jupiter. It was recently found, however, that t...

An analytical comparison of four technologies for deorbiting spacecraft from Low-Earth-Orbit at end of mission is presented. Basic formulas based on simple physical models of key figures of merit for each device are found. Active devices - rockets and electrical thrusters - and passive technologies - drag augmentation devices and electrodynamic tet...

All four giant planets, far from the Earth and sun and having deep gravitational wells, present propulsion and power mission issues, but they also have an ambient plasma and magnetic field that allows for a common mission concept. Electrodynamic tethers can provide propellantless drag for planetary capture and operation down the gravitational well,...

A principle on the macroscopic motion of systems in thermodynamic equilibrium, rarely discussed in texts, is reviewed: Very small but still macroscopic parts of a fully isolated system in thermal equilibrium move as if points of a rigid body, macroscopic energy being dissipated to increase internal energy, and increase entropy along. It appears par...

A Thermionic Bare Tether (TBT) is a long conductor coated with a low work-function material. In drag mode, a tether segment extending from anodic end A to a zero-bias point B, with standard Orbital-motion-limited current collection, is followed by a complex cathodic segment. In general, as bias becomes more negative in moving from B to cathodic end...

It has recently been shown that a thin-tape tether, as opposite to a round one, has a high probability of survival to single impacts by space debris, under a broad range of de-orbit operation conditions. The purpose of the present work is to extend that analysis to survival to multiple impacts by smaller, but more abundant, debris. The method used...

De-orbiting satellites at end of mission would prevent generation of new space debris. A proposed de-orbit technology involves a bare conductive tape-tether, which uses neither propellant nor power supply while generating power for on-board use during de-orbiting. The present work shows how to select tape dimensions for a generic mission so as to s...

With a thin coating of low-work-function material, thermionic emission in the cathodic segment of bare tethers might be much greater than orbital-motion-limited (OML) ion collection current. The space charge of the emitted electrons decreases the electric field that accelerates them outwards, and could even reverse it for high enough emission, prod...

The low earth orbit (LEO) environment contains a large number of artificial debris, of which a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Deorbiting defunct satellites at the end of their life can be achieved by a successful operation of an Electrodynamic Tether (EDT)...

BETs is a three-year project financed by the Space Program of the European Commission, aimed at developing an efficient deorbit system that could be carried on board any future satellite launched into Low Earth Orbit (LEO). The operational system involves a conductive tape-tether left bare to establish anodic contact with the ambient plasma as a gi...

The current space environment, consisting of a huge population of man-made debris in addition to natural micrometeoroids, pose a serious risk to safe operations in space, and the situation is continuously deteriorating due to in-orbit debris collisions and to new satellite launches. Bare electrodynamic tethers can provide an efficient mechanism for...

A new material, C12A7:e{sup -} electride, which might present a work function as low as 0.6 eV and moderately high temperature stability, was recently proposed as coating for floating bare tethers. Arising from heating under space operation, current is emitted by thermionic emission along a thus coated cathodic segment. A preliminary study on the s...

The accumulation of space debris around the Earth has become critical for Space security. The BETs project, financed by the European Commission through its FP7-Space program, is focusing on preventing generation of new debris by de-orbiting satellites at end of mission. The de-orbiting system considered, involving an electrodynamic bare tape-tether...

The current I to a cylindrical Langmuir probe with a bias {Phi}{sub p} satisfying {beta}{identical_to}e{Phi}{sub p}/m{sub e}c{sup 2}{approx}O(1) is discussed. The probe is considered at rest in an unmagnetized plasma composed of electrons and ions with temperatures kT{sub e}{approx}kT{sub i} Much-Less-Than m{sub e}c{sup 2}. For small enough radius,...

We present the possibility of a low work-function material, calcium aluminate electride, being used for a coating on a bare electrodynamic tether system. Analyses suggest that the coating would eliminate the need for an active cathodic device like a hollow cathode and, consequently, eliminate the need for an expellant to the hollow cathode, thus re...

A two-stage mission to place a spacecraft (SC) below the Jovian radiation belts, using a spinning bare tether with plasma contactors at both ends to provide propulsion and power, is proposed. Capture by Lorentz drag on the tether, at the periapsis of a barely hyperbolic equatorial orbit, is followed by a sequence of orbits at near-constant periapsi...

A 3-year Project financed by the European Commission is aimed at developing a universal system to de-orbit satellites at their end of life, as a fundamental contribution to limit the increase of debris in the Space environment. The operational system involves a conductive tapetether left bare to establish anodic contact with the ambient plasma as a...

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. T...

A spaceflight validation of bare electrodynamic tape tether technology was conducted. A S520-25 sounding rocket was launched successfully at 05:00am on 31 August 2010 and successfully deployed 132.6m of tape tether over 120 seconds in a ballistic flight. The electrodynamic performance of the bare tape tether employed as an atmospheric probe was mea...

A 3-year Project started on November 1 2010, financed by the European Commision within the FP-7 Space Program, and aimed at developing an efficient de-orbit system that could be carried on board by future spacecraft launched into LEO, will be presented. The operational system will deploy a thin uninsulated tape-tether to collect electrons as a gian...

A bare electrodynamic tether (EDT) is a conductive thin wire or tape tens of kilometres long, which is kept taut in space by gravity gradient or spinning, and is left bare of insulation to collect (and carry) current as a cylindrical Langmuir probe in an ambient magnetized plasma. An EDT is a probe in mesothermal flow at highly positive (or negativ...

Propulsion and power generation by bare electrodynamic tethers are revisited in a unified way and issues and constraints are addressed. In comparing electrodynamic tethers, which do not use propellant, with other propellant-consuming systems, mission duration is a discriminator that defines crossover points for systems with equal initial masses. Ba...

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...

The excitation of Fast Magnetosonic (FMS) waves by a cylindrical array of parallel tethers carrying time-modulated current is discussed. The tethers would fly vertical in the equatorial plane, which is perpendicular to the geomagnetic field when its tilt is ignored, and would be stabilized by the gravity gradient. The tether array would radiate a s...

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...

The so-called electrical power generation problem for exploration of the outer planets could be solved deploying an electrodynamic tether. Wave radiation by a conductor carrying a steady current in a polar, highly eccentric, low perijove orbit, as in the planned NASA Juno mission, is considered. The high Jupiter's oblateness produces fast apsidal p...

An electrodynamic bare tether is shown to allow carrying out scientific observations very close to Jupiter, for exploration of its surface and subsurface, and ionospheric and atmospheric in-situ measurements. Starting at a circular equatorial orbit of radius about 1.3/1.4 times the Jovian radius, continuous propellantless Lorentz drag on a thin-tap...

An electrodynamic bare-tether mission to Jupiter, following the capture of a spacecraft (SC) into an equatorial highly elliptical orbit with perijove at about 1.3 times the Jovian radius, is discussed. Repeated applications of the propellantless Lorentz drag on a spinning tether, at the perijove vicinity, can progressively lower the apojove at cons...

An electrodynamic tether system for power generation at Jupiter is presented that allows extracting energy from Jupiter's corotating plasmasphere while leaving the system orbital energy unaltered to first order. The spacecraft is placed in a polar orbit with the tether spinning In the orbital plane so that the resulting Lorentz force, neglecting Ju...

An overview of a sounding rocket, S-520-25th, project on space tether technology experiment is presented. The project is prepared by an international research group consisting of Japanese, European, American, and Australian researchers. The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009. The sounding r...

A power generation scheme based on bare electrodynamic tethers (EDT) working in passive mode is investigated for the purpose of supplying power to scientific missions at Saturn. The system employs a spinning EDT on a low-altitude polar orbit which permits to efficiently convert plasma sphere energy into useful power. After optimizing the tether des...

Tethered spacecraft missions to the Jovian system suit the use of electrodynamic tethers because: 1) magnetic stresses are 100 times greater than at the Earth; 2) the stationary orbit is one-third the relative distance for Earth; and 3) moon Io is a nearby giant plasma source. The (bare) tether is a reinforced aluminum foil with tens of kilometer l...

Analytical expressions for current to a cylindrical Langmuir probe at rest in unmagnetized plasma are compared with results from both steady-state Vlasov and particle-in-cell simulations. Probe bias potentials that are much greater than plasma temperature (assumed equal for ions and electrons), as of interest for bare conductive tethers, are consid...

Palabras claves: ondas de Alfvén, DNLS, métodos espectrales. Resumen. Interacciones no lineales de ondas de Alfvén existen tanto para plasmas en el espacio como en laboratorios. En ingeniería aeroespacial amarras electrodinámicas espaciales ("tethers") generan emisión de ondas de Alfvén en estructuras denominadas "Alas de Alfvén". La ecuación Deriv...

An electrodynamic tether mission at Jupiter, starting with capturing the spacecraft into a retrograde, equatorial, highly elliptical orbit at low perijove, is discussed. The tether would be a thin tape, 50 kilometers long and 0.05 mm thick, with a 12 minutes spin period. In a first phase, repeated application of propellantless Lorentz drag on the t...

Electrodynamic tethers are known to exhibit high performance in the Jupiter environment , both as propellantless propulsion devices and as power generating systems. In spite of the considerable amount of research work of electrodynamic tethers in the Jupiter environment the case involving high inclination orbit has never been addressed so far. We p...

Space applications of electrodynamic tethers, and basic issues and constraints on their operation are reviewed. The status of the bare-tether solution to the problem of effective electron collection from a rarefied magnetized plasma is revisited. Basic modes of tether operation are analyzed; design parameters and parametric domains where a bare ele...

A study supported by the European Space Agency (ESA), in the context of its General Studies Programme, performed an investigation of the possible use of space for studies in pure and applied plasma physics, in areas not traditionally covered by 'space plasma physics'. A set of experiments have been identified that can potentially provide access to...

The non-linear wave front generated by modulating the current in an orbiting electrodynamic tether (1) is considered. A parametric Mathieu-like instability excited by the driven oscillating magnetic field (2) in the induction region around the tether is analyzed. Both Alfven and Fast Magnetosonic modes, including ion cyclotron and whistler frequenc...

Electrodynamic (ED) tethers could be alternative sources of electrical power for missions to Jupiter. Waves radiated by an ED tether, as if supplying power in a JUNO-like (polar, low perijove, high-eccentricity) orbit, are considered. Radiation differs from the Earth ionospheric case [1] because of differences in orbital and planetary conditions, t...

An orbiting conductive tether provides a dissipative mechanism in planets that have magnetic field and ionosphere/magnetosphere. The Jovian system is a particularly appropriate place for use of an electrodynamic tether because the magnetic field is intense, the stationary orbit is close to the planet, and moon Io provides a dense plasma torus farth...

An electrodynamic bare tether could be an alternative source of power for jovian missions such as Juno, which is NASA´s latest proposed mission to Jupiter; Juno, which will be a polar orbiter, is planned to move away from previous use of radioisotope thermoelectric generators to use of solar arrays, required to be very large due to the great distan...

Four-dimensional flow in the phase space of three amplitudes of circularly polarized Alfven waves and one relative phase, resulting from a resonant three-wave truncation of the derivative nonlinear Schrödinger equation, has been analyzed; wave 1 is linearly unstable with growth rate Γ, and waves 2 and 3 are stable with damping γ2 and γ3, respective...

Use of a conductive bare tape electrically floating in low Earth orbit as an effective electron beam source to produce artificial auroral effects, free of problems that mar standard beams, is considered. Ambient ions impacting the tape with keV energies over most of its length liberate secondary electrons that race down the magnetic field, excite n...

Deorbit, power generation, and thrusting performances of a bare thin-tape tether and an insulated tether with a spherical electron collector are compared for typical conditions in low-Earth orbit and common values of length L=4-20 km and cross-sectional area of the tether A=1-5 mm². The relative performance of moderately large spheres, a...

Palabras claves: ondas de Alfvén, DNLS, amarras espaciales, caos. Resumen. Interacciones no lineales de ondas de Alfvén existen tanto para plasmas en el espacio como en laboratorios, con efectos que van desde calentamiento hasta conducción de corriente. Un ejemplo de emisión de ondas de Alfvén en ingeniería aeroespacial aparece en amarras espaciale...

Use of electrodynamic bare tethers in exploring the Jovian system by tapping its rotational energy for power and propulsion is studied. The position of perijove and apojove in elliptical orbits, relative to the synchronous orbit at 2.24 times Jupiter's radius, is exploited to conveniently make the induced Lorentz force to be drag or thrust, while g...

The performance efficiency of electrodynamic bare tethers acting as thrusters in low Earth orbit, as gauged by the ratio of the system mass dedicated to thrust over mission impulse, is analyzed and compared to the performance efficiency of electrical thrusters. Tether systems are much lighter for times beyond six months in space-tug operations, whe...

The efficient performance of hybrid systems such as electrodynamic Tethers against ion thrusters was investigated. The ED tether is more efficient than ion thruster as it uses no propellant and the HC expellant mass for the same mission impulse. ED tether shows a higher impulse-to-mass ratio which results in greater efficiency of the ED tether. Res...

Defining special type of uppercase notation newcommand names 1 textsc 1 In order to characterise the names lageos dynamical behaviour to the mm level a study has been made on an important contributor to the names lageos non-gravitational perturbations problem the charged particle drag names cpd with its two main components direct collision and scat...

The derivative nonlinear Schrödinger (DNLS) equation, describing propagation of circularly polarized Alfven waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. No matter how small the growth rate of the...

The development of a three-phase full tour of the Jovian system using a bare electrodynamic tether with a new prograde-orbit design, with no need of propellant and power sources, was discussed. In the first phase, following capture, tether current was off all along the resulting elongated ellipse untill rendering the drag sphere, when it was again...

This paper is to introduce two space tether experimental projects including; 1) a sounding rocket experiment in a ballistic flight extending 1km bare tape tether, and 2) a small satellite experiment on a circular orbit with the altitude 600km extending 20km electro-dynamic tether. The sounding rocket experiment employs bare electro-dynamic tether f...

A (bare) conductive tether electrically floating in LEO orbit would be an effective e-beam source free of problems that marred standard beams producing artificial auroras. Ambient ions impacting the tether with KeV energies over most of its length liberate secondary electrons that result in emissions in the E-layer. Brightness measurements from the...

Tours of the great outer planets and their moons can be accomplished by utilizing an electrodynamic tether attached to the spacecraft as both power system and propulsion device. Through interaction with the planetary magnetic field and inner plasmasphere, the tether could get electrical power, and either thrust or drag, out of the rotational motion...

This study purports to investigate whether a conductive tether left uninsulated and electrically floating in LEO could serve as an effective e-beam source to produce artificial auroras. An electrically floating tether comes out biased highly negative over most of its length. Ambient ions impacting it with KeV energies liberate secondary electrons,...

The features of space tethers, which are used in space mission, are discussed. The masses of the electrodynamic tether systems are separated by flexible, electrically conductive cable. Tethers perform the same functions as the conventional spacecraft but without the use of chemical or nuclear fuel sources. In low Earth orbit, tether systems provide...

A mission on board a sounding rocket to carry out two bare-tether experiments is proposed: a test of orbital-motion-limited (OML) collection and the proof-of-flight of a technique to determine the (neutral) density vertical profile in the critical E-layer. Since full bias from the motional field will be small (∼ 20V), corresponding to a tape 1 km l...

The derivative nonlinear Schrödinger (DNLS) equation, describing propagation of circularly polarized Alfvén waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. In a reduced three-wave model (equa...

NASA's tether experiment ProSEDS will be placed in orbit on board a Delta-II rocket to test bare-tether electron collection, deorbiting of the rocket second stage, and the system dynamic stability. ProSEDS performance will vary because ambient conditions change along the orbit and tether-circuit bulk elements at the cathodic end follow the step-by-...

The electron-retarding range of the current-voltage characteristic of a flat Langmuir probe perpendicular to a strong magnetic field in a fully ionized plasma is analysed allowing for anomalous (Bohm) cross-field transport and temperature changes in the collection process. With probe size and ion thermal gyroradius comparable, and smaller than the...

It was recently suggested that the magnetic field created by the current of a bare tether strongly reduces its own electron-collection capability when a magnetic separatrix disconnecting ambient magnetized plasma from tether extends beyond its electric sheath. It is here shown that current reduction by the self-field depends on the ratio L*/Lt para...

Usual long, flexible, ED tethers kept vertical by the gravity gradient might be less efficient for deorbiting S/C in near-polar orbits than conventional (Hall, Ion) electrical thrusters. A trade-off study on this application is here presented for tethers kept horizontal and perpendicular to the orbital plane. A tether thus oriented must be rigid an...

Performances, design criteria, and system mass of bare tethers for satellite deorbiting missions are analyzed. Orbital conditions and tether cross section define a tether length, such that 1) shorter tethers are electron collecting practically in their whole extension and 2) longer tethers practically the short-circuit current in a fixed segment le...

The operational advantages of electrodynamic tethers of moderate length are becoming evident from studies of collision avoidance. Although long tethers (of order of 10 kilometers) provide high efficiency and good adaptability to varying plasma conditions, boosting tethers of moderate length (∼1 kilometer) and suitable design might still operate at...

Current to a cylindrical probe of arbitrary cross section is discussed. Previous results for circular cylinders at the high bias and moderate radius R of interest for electrodynamic bare tethers, for which space charge may be ignored over a large neighborhood of the probe, depend in separate ways on both R and perimeter p. These results are extende...

The efficiencies of electrodynamic-tether (EDT) thrusters made of single bare tethers with different types of cross sections, several parallel bare tethers, or a fully insulated tether with a three-dimensional passive end-collector, are discussed. Current collection, mass, and ohmic resistance considerations are balanced against each other in discu...

ED bare tethers are best systems to deorbit S/C at the end of service. For near polar orbits, usual tethers kept vertical by the gravity gradient, yield too weak magnetic drag. Here we propose keeping tethers perpendicular to the orbital plane. They must be rigid and short for structural reasons, requiring power supply like Ion thrusters. Tether tu...

Inverse bremsstrahlung has been incorporated into an analytical model of the expanding corona of a laser-irradiated spherical target. Absorption decreases slowly with increasing intensity, in agreement with some numerical simulations, and contrary to estimates from simple models in use up to now, which are optimistic at low values of intensity and...

The transition that the expansion flow of laser-produced plasmas experiences when one moves from long, low intensity pulses (temperature vanishing at the isentropic plasma-vacuum front, lying at finite distance) to short, intense ones (non-zero, uniform temperature at the plasma-vacuum front, lying at infinity) is studied. For planar geometry and l...

Resonant absorption of p-polarized light shone on a plane-layered plasma with a step profile, is discussed as a function of wavelength (or critical density nc) of the light; for simplicity the incidence angle is assumed small. If nc lies within or above the step, the absorption A is given by Ginzburg's result (1970) modified by strong reflections a...

The acceleration of a thin foil using a laser pulse is studied. It is shown that the acceleration efficiency eta H is heavily dependent on the behaviour of the corona ejected by the foil: there is no universal relation eta H( Delta M/M0),M0 and Delta M being initial foil mass and ablated mass, respectively. Known results on the coronal flow are use...

The Retarding Potential Analyzer (RPA) is the standard instrument for in situ measurement of ion temperature and other ionospheric parameters. The fraction of incoming ions rejected by a RPA produces perturbations that reach well ahead of a thin Debye sheath, a feature common to all collisionless, hypersonic flows past ion-rejecting bodies. This ph...

The current I to a cylindrical probe at rest in an unmagnetized plasma, with probe bias highly positive, is determined. The way I lags behind the orbital-motion-limited (OML) current, IOML~R, as the radius R exceeds the maximum radius for the OML regime to hold, is of interest for space-tether applications. The ratio I/IOML is roughly a decreasing...