Apollo Lightcraft Project

The ultimate goal for this NASA/USRA-sponsored Apollo Lightcraft Project is to develop a revolutionary manned launch vehicle technology which can potentially reduce payload transport costs by a factor of 1000 below the Space Shuttle Orbiter. The Rensselaer design team proposes to utilize advanced, highly energetic, beamed-energy sources (laser, microwave) and innovative combined-cycle (airbreathing/rocket) engines to accomplish this goal. The research effort focuses on the concept of a 100 MW-class, laser-boosted Lightcraft Technology Demonstrator (LTD) drone. The preliminary conceptual design of this 1.4 meter diameter microspacecraft involved an analytical performance analysis of the transatmospheric engine in its two modes of operation (including an assessment of propellant and tankage requirements), and a detailed design of internal structure and external aeroshell configuration. The central theme of this advanced propulsion research was to pick a known excellent working fluid (i.e., air or LN sub 2), and then to design a combined-cycle engine concept around it. Also, a structural vibration analysis was performed on the annular shroud pulsejet engine. Finally, the sensor satellite mission was examined to identify the requisite subsystem hardware: e.g., electrical power supply, optics and sensors, communications and attitude control systems

Electron Weibel instability induced magnetic fields in optical-field ionized plasmas

Generation and amplification of magnetic fields in plasmas is a long-standing topic that is of great interest to both plasma and space physics. The electron Weibel instability is a well-known mechanism responsible for self-generating magnetic fields in plasmas with temperature anisotropy and has been extensively investigated in both theory and simulations, yet experimental verification of this instability has been challenging. Recently, we demonstrated a new experimental platform that enables the controlled initialization of highly nonthermal and/or anisotropic plasma electron velocity distributions via optical-field ionization. Using an external electron probe bunch from a linear accelerator, the onset, saturation and decay of the self-generated magnetic fields due to electron Weibel instability were measured for the first time to our knowledge. In this paper, we will first present experimental results on time-resolved measurements of the Weibel magnetic fields in non-relativistic plasmas produced by Ti:Sapphire laser pulses (0.8 $\mu m$) and then discuss the feasibility of extending the study to quasi-relativistic regime by using intense $\rm CO_2$ (e.g., 9.2 $\mu m$) lasers to produce much hotter plasmas.Comment: 22 pages, 10 figure

Mapping the self-generated magnetic fields due to thermal Weibel instability

Weibel-type instability can self-generate and amplify magnetic fields in both space and laboratory plasmas with temperature anisotropy. The electron Weibel instability has generally proven more challenging to measure than its ion counterpart owing to the much smaller inertia of electrons, resulting in a faster growth rate and smaller characteristic wavelength. Here, we have probed the evolution of the two-dimensional distribution of the magnetic field components and the current density due to electron Weibel instability, in $\rm CO_2$-ionized hydrogen gas (plasma) with picosecond resolution using a relativistic electron beam. We find that the wavenumber spectra of the magnetic fields are initially broad but eventually shrink to a narrow spectrum representing the dominant quasi-single mode. The measured $k$-resolved growth rates of the instability validate kinetic theory. Concurrently, self-organization of microscopic plasma currents is observed to amplify the current modulation magnitude that converts up to $\sim 1\%$ of the plasma thermal energy into magnetic energy.Comment: 24 pages, 4 figure

How important is the dynamical information in determination of LEO orbits

The interest in a precise orbit determination of Low Earth Orbiters (LEOs) using GNSS observations to recover of the Earth's gravity field has been grown rapidly. With the advent of precise orbit and clock products at centimeter level accuracy provided by the IGS analysis centers and the geometrical connections between GNSS satellites and LEOs, the orbit of LEOs can be estimated based on only a single GNSS receiver onboard LEOs. The determined LEO orbit is based on only geometrical configuration between GNSS and LEO. This procedure is known as Geometrical Precise Orbit Determination (GPOD). The ephemerides of point-wise LEO positions can be derived by this method at every observation epochs. Kinematical Precise Orbit Determination (KPOD) is another estimation procedure, which is based on the geometrical information too. Based on a new proposed method, the kinematical orbit is represented by a sufficient number of approximation parameters, including boundary values of the LEO arc. This kind of orbit representation not only allows to determine arbitrary functional (e.g. velocity and acceleration) of the satellite arc's, but it is also possible to use dynamical observations for the determination of orbit parameters. It should be mentioned that in the geometrical and kinematical orbit determination procedures, no dynamical (force) information is used at all. Because of the close relation of the estimated kinematical parameters with the force function model, the orbit determination can be designed as a pure kinematical orbit determination on the one hand, and a pure dynamical orbit determination on the other hand. In other words, this formulation of the orbit determination allows a smooth transition from a kinematical to dynamical orbit determination. At the one end, the orbit parameters are determined without any force (dynamical) information at all, and the other extreme end, all orbit representing parameters are functions of the force model. If only weak dynamical restrictions are introduced to the estimation procedure, then a reduced-kinematical orbit results. In this poster, the new proposed orbit determination concept will be introduced and the effect of the dynamical information in the orbit determination procedures will be presented for the GOCE mission as a case study based on the simulated data. The various possibilities with the corresponding results of GOCE based on GNSS observations will be presented

The importance of antepartum cardiotocography

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Mapping the self-generated magnetic fields due to thermal Weibel instability

The origin of the seed magnetic field that is amplified by the galactic dynamo is an open question in plasma astrophysics. Aside from primordial sources and the Biermann battery mechanism, plasma instabilities have also been proposed as a possible source of seed magnetic fields. Among them, thermal Weibel instability driven by temperature anisotropy has attracted broad interests due to its ubiquity in both laboratory and astrophysical plasmas. However, this instability has been challenging to measure in a stationary terrestrial plasma because of the difficulty in preparing such a velocity distribution. Here, we use picosecond laser ionization of hydrogen gas to initialize such an electron distribution function. We record the 2D evolution of the magnetic field associated with the Weibel instability by imaging the deflections of a relativistic electron beam with a picosecond temporal duration and show that the measured [Formula: see text]-resolved growth rates of the instability validate kinetic theory. Concurrently, self-organization of microscopic plasma currents is observed to amplify the current modulation magnitude that converts up to ~1% of the plasma thermal energy into magnetic energy, thus supporting the notion that the magnetic field induced by the Weibel instability may be able to provide a seed for the galactic dynamo