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The interaction between a probe body and argon plasma flow is investigated to examine to what extent the probe head temperature and the bow shock distance can be influenced by applying a strong magnetic field. The experiments are performed using a strong permanent magnet installed inside a probe body with a spherical, coated probe head. Former investigations showed strong influence on the bow shock geometry but also on the inflow plasma jet. Several boundary conditions have been varied to evaluate their influence toward the experiment. For an uncoated probe head the measured MHD impact was found to be of the same order of magnitude as for the coated case. Electrical isolation of the probe toward the vacuum chamber yielded only slight influence. The variation of the field strength was realized by changing the amount of magnet segments installed. Pictures were analyzed to minute the MHD interaction for each test case. It was found that the bow shock distance increased and the temperature of the probe head decreased while increasing the magnetic field density. This analysis precedes a thorough characterization of the plasma condition.

Flight experiments with laser-propelled vehicles (lightcrafts) are often performed by wire-guidance or with spin-stabilization. Nevertheless, the specific geometry of the lightcraft’s optics and nozzle may provide for inherent beam-riding properties. These features are experimentally investigated in a hovering experiment at a small free fliight test range with an electron-beam sustained pulsed CO2 high energy laser. Laser bursts are adapted with a real-time control to lightcraft mass and impulse coupling for ascent and hovering in a quasi equilibrium of forces. The flight dynamics is analyzed with respect to the impulse coupling field vs. attitude, given by the lightcraft’s offset and its inclination angle against the beam propagation axis, which are derived from the 3Dreconstruction of the flight trajectory from highspeed recordings. The limitations of the experimental parameters’ reproducibility and its impact on flight stability are explored in terms of Julia sets. Solution statements for dynamic stabilization loops are presented and discussed.

We report on an international cooperation between Nagoya University (NU), Japan and DLR Stuttgart, Germany on scaling issues in laser ablative propulsion. Lessons learned from collaborative work in the laboratory will be summarized with respect to the comparability of experimental methods and corresponding standardization issues. With the background of previous experimental research at the University of Alabama in Huntsville (UAH), experimental work with CO2 lasers in a moderate (NU) and high (DLR) pulse energy range on laser ablation of POM is presented. Profilometry results of target surfaces are compared with fluence distributions from beam propagation modeling. Ablation from flat targets is reported with respect to energy and area scaling and compared with results from ablative propulsion employing parabolic nozzles.

It is a relevant issue in the research on laser propulsion that experimental results are treated seriously and that meaningful scientific comparison is possible between groups using different equipment and measurement techniques. However, critical aspects of experimental measurements are sparsely addressed in the literature. In addition, few studies so far have the benefit of independent confirmation by other laser propulsion groups. In this paper, we recommend several approaches towards standardization of published laser propulsion experiments. Such standards are particularly important for the measurement of laser ablation pulse energy, laser spot area, imparted impulse or thrust, and mass removal during ablation. Related examples are presented from experiences of an actual scientific cooperation between NU and DLR. On the basis of a given standardization, researchers may better understand and contribute their findings more clearly in the future, and compare those findings confidently with those already published in the laser propulsion literature. Relevant ISO standards are analyzed, and revised formats are recommended for application to laser propulsion studies.

Polyoxymethylene (POM) propellants have been studied since the 1970's, and perhaps represent the most promising match of a propellant to the CO2 laser for laser propulsion studies. Applications range from ground-launch of laser propulsion vehicles at atmospheric pressure to spacebased laser ablation propulsion microthrusters. In this paper we broadly update the state of understanding of CO2 laser ablation of POM based on new experiments conducted in Japan and Germany, with a focus on the basic physics of ablation of flat POM targets. Measurements using 10 J-class and 100 J-class lasers are compared to previous literature results for ablation of POM. Emphasis is placed on the influence of control parameters on ablation, especially the incident laser fluence and ambient pressure. New results highlight the influence of the ambient pressure on ablation physics from the vaporization threshold to the plasma regime, and clarify the role of the fluence in determining ablation behavior in air and vacuum environments. Imparted impulse and ablated mass were measured at the target using piezoelectric force sensors, impulse pendulums, and scientific balances. The new experimental investigations cover orders of magnitude in fluence (10E-2 to 10E3 J/cm2) and ambient pressure (10E-3 to 10E5 Pa).

One of the remaining subjects of interest for laser ablation propulsion study is whether special benefits or challenges exist when applying a particularly large or small laser spot area to a target. This subject is of high importance for topics including laser removal of space debris, micropropulsion, and design of laser propulsion vehicles. Analysis of spot area-dependent effects is complex since ablation phenomena differ between atmosphere and vacuum conditions. Progress has also been impeded by the difficulty of setting control parameters (particularly fluence) constant while the spot area is adjusted. It is virtually impossible for one group to address small- and large-area effects using a single high-power laser system. Recent collaborative experiments using 100-J class and 10-J class CO2 lasers have advanced the understanding of laser propulsion area scaling. Experiments were conducted below the threshold for plasma formation. The dependence of various laser propulsion parameters on the laser spot area has been investigated within areas covering approximately 0.5-50 cm2 on the target.

Wissensstand zu Lunar Libration Clouds, bzw. Kordylewski'sche Wolken durch bisherige Beobachtungen von der Erde, aus Flugzeugen und Raumsonden. Beobachtungsszenarien für Mondmission BW1 während der Cruise Phase.