SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006

13 ASTRODYNAMICS
Includes powered and free flight trajectories; orbital and launching dynamics.

20060019537 Central Research Inst. of Machine Building, Korolev, Russian Federation

'High-Power Hall Devices: Status and Current Challenges'

Semenkin, Alexander V; Kim, V; Manzella, D; Murashko, V; Tverdokhlebov, S; Jun 25, 2004; 15 pp.; In English; Original contains color illustrations Report No.(s): AD-A446484; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446484; Avail.: CASI: A03, Hardcopy

Consideration of the high power electric propulsion (EP) orbit transfer vehicles, interplanetary robotic and manned missions from one side and successful application of Hall thrusters onboard of numerous GEO satellites (Russian EXPRESS and YAMAL series), European scientific mission SMART-I on the other side stimulate interest to high power Hall devices, suitable for the future applications. Current experience for the Hall flight thrusters is limited by 1-kW-class of propulsion systems. At the same time engineering thrusters have demonstrated power level about 25 kW (Fakel Design Bureau, Russia) and almost 100 kW (NASA GRC) with using xenon as a propellant, 150 kW for bismuth thruster (TSNIIMASH, Russia).

It is necessary to underline, that principal limits have not been identified for the further increasing of the thruster size and power. This makes the Hall devices at least very competitive for high power application as compared with other types of electric thrusters: MPD and ION thrusters. For high power EP systems two typical operation modes may be considered, namely 'high specific impulse (Isp)' and high thrust' modes. Correspondingly challenges to develop Hall EP system are different for each one. For high thrust' mode the development issues associate with increasing of propellant flow and thruster size. Discharge voltage to get 'high thrust' regime with best power-to-thrust ratio should be 150..300 V, and it is inside of well studied operation range of Hall thrusters. For 'high Isp' mode required discharge voltage in several times than one for flight qualified Hall EP systems, while mass flow does not essentially exceed already achieved level. DTIC

Electric Propulsion; Hall Effect; Hall Thrusters; Orbits; Robotics

20060019810 Knowledge Based Systems, Inc., College Station, TX USA

On-Line Adaptive Estimation and Trajectory Reshaping

Verma, Ajay; Oppenheimer, Michael W; Doman, David B; Sep 2005; 14 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): FA8650-04-M-3428 Report No.(s): AD-A446860; No Copyright; Avail.: CASI: A03, Hardcopy

An Adaptive Trajectory Reshaping and Control (ATRC) system is envisioned for RLVs to avoid catastrophic failure when subjected to performance restricting damages and failures. The ATRC is a response system that continuously reshapes and optimizes the reference RLV trajectory, such that, if physically possible, the feasibility constraints are satisfied. The focus of this paper is on two important features of the ATRC system that allow (a) estimation of a parameter functional over the RLV flight envelope to determine feasibility constraints, and (b) real time reshaping of the RLV trajectory for feasibility and optimization of end goals. The knowledge of the effects of a failure at future flight condition is required to design and reshape feasible trajectories. Our approach uses regularization of the ill-posed learning problem by using fusion of existing knowledge and geometric structure in the functional to reduce the uncertainties of future flight conditions. The paper also addresses the difficult problem of real time on-line trajectory generation based on an inverse dynamics principle. An acceptable trajectory is a solution of a two-point boundary value problem for a non-flat (under-actuated) non-linear differential equation of motion. The inverse dynamics approach solves a set of algebraic equations, which strictly satisfies the non-linear differential equations of a non-flat system. DTIC

Adaptation; Launch Vehicles; On-Line Systems; Trajectories

Source: NASA