[en] This paper presents catalyst development for Sabatier and RWGS reactions

[en] The status of some exotic physical phenomena and unconventional spacecraft concepts that might produce breakthroughs in power and propulsion in the 21st Century are reviewed. The subjects covered include: electric, nuclear fission, nuclear fusion, antimatter, high energy density materials, metallic hydrogen, laser thermal, solar thermal, solar sail, magnetic sail, and tether propulsion

[en] Due to electric propulsion's inherent propellant mass savings over chemical propulsion, electric propulsion orbit transfer vehicles (EPOTVs) are a highly efficient mode of orbit transfer. When selecting an electric propulsion device (ion, MPD, or arcjet) and propellant for a particular mission, it is preferable to use quick, analytical system optimization methods instead of time intensive numerical integration methods. It is also of interest to determine each thruster's optimal operating characteristics for a specific mission. Analytical expressions are derived which determine the optimal specific impulse (Isp) for each type of electric thruster to maximize payload fraction for a desired thrusting time. These expressions take into account the variation of thruster efficiency with specific impulse. Verification of the method is made with representative electric propulsion values on a LEO-to-GEO mission. Application of the method to specific missions is discussed

[en] We present two objections to Redzic conclusion that in the 'tough variant' of Bell's thread-between-spaceships problem (the ships' acceleration is constant) the stretch of the thread remains finite. First, we show that because of the existence of the horizon for the accelerated observer Redzic drops out an essential part of the thread's history. Second, we show that there is no simple relation between the distance between the spaceship and the physical (leading to strain) stretch of the thread. We also present the correct estimate for the stretch, which shows that the stretch increases infinitely. (letters and comments)

[en] The effect of the velocity program and duty cycle (St_L) on the propulsive efficiency of pulsed-jet propulsion was studied experimentally on a self-propelled, pulsed-jet underwater vehicle, dubbed Robosquid due to the similarity of essential elements of its propulsion system with squid jet propulsion. Robosquid was tested for jet slug length-to-diameter ratios (L/D) in the range 2-6 and St_L in the range 0.2-0.6 with jet velocity programs commanded to be triangular or trapezoidal. Digital particle image velocimetry was used for measuring the impulse and energy of jet pulses to calculate the pulsed-jet propulsive efficiency and compare it with an equivalent steady jet system. Robosquid's Reynolds number (Re) based on average vehicle velocity and vehicle diameter ranged between 1300 and 2700 for the conditions tested. The results indicated better propulsive efficiency of the trapezoidal velocity program (up to 20% higher) compared to the triangular velocity program. Also, an increase in the ratio of the pulsed-jet propulsive efficiency to the equivalent steady jet propulsive efficiency (η_P/η_P,ss) was observed as St_L increased and L/D decreased. For cases of short L/D and high St_L, η_P/η_P,ss was found to be as high as 1.2, indicating better performance of pulsed jets. This result demonstrates a case where propulsion using essential elements of a biological locomotion system can outperform the traditional mechanical system equivalent in terms of efficiency. It was also found that changes in St_L had a proportionately larger effect on propulsive efficiency compared to changes in L/D. A simple model is presented to explain the results in terms of the contribution of over-pressure at the nozzle exit plane associated with the formation of vortex rings with each jet pulse.

[en] During the 20th century, the world Navies has seen an evaluation of the capital ship concept, moving from the battleship to the aircraft carrier and from this last one to the submarine. We have no doubts that this three warship classes are the most sophisticated and complex products of Naval Engineering. Submarine supremacy, today a clear trend, will be completely consolidated during the 21st century. Naval Engineering would be prepared to cope, on technological aspects, with the growing operational performance demands for this warship class along next decades. This work aims to introduce and discuss that demands and identify, through a analysis of trends, the technical solutions, in design and construction fields, will satisfy the future requirements. (author)

[en] Possible mission scenarios for a 30 kWe reactor demonstration are considered. An NEP arcjet spacecaft design utilizing state of the art technology is outlined, and mission performance with launches from Kennedy Space Center using Titan 4, Titan 3, and Atlas 2AS ELVs is described. Performance data are represented parametrically with payload mass and trip time presented as a function of maneuver velocity increment delta-V. The latter is also presented as a function of final altitude and inclination change so that specific mission maneuvers can be examined. 13 refs

[en] It is shown that a starprobe could be built to perform a flyby mission to Proxima Centauri in approximately 400 years. This vehicle would use familiar fission nuclear reactor and ion propulsion system technologies to achieve a burn-out velocity of 0.0122c. Fine engineering and progressive technology refinements are shown to be the key to operating, and further improving, the capability of this long burn time propulsion system. 12 references

[en] An overview is presented of special propulsion research carried out in Beijing University of Aeronautics and Astronautics of China. The research activities are supported by NSFC (National Natural Science Foundation of China), other governmental agencies and industrial partners, which include experimental, analytical and numerical work related to arcjet thrusters, ion thrusters, plasma sail and other new concept propulsions

[en] In this investigation, five potential manned Mars transportation systems are compared. These options include: (1) a single vehicle, chemically propelled (CHEM) option, (2) a single vehicle, nuclear thermal propulsion (NTP) option, (3) a single vehicle solar electric propulsion (SEP) option, (4) a single vehicle hybrid nuclear electric propulsion (NEP)/CHEM option, and (5) a dual vehicle option (NEP cargo spacecraft and CHEM manned vehicle). In addition to utilizing the initial vehicle weight in low-earth orbit as a measure of mission feasibility, this study addresses the major technological barriers each propulsive scenario must surpass. It is shown that instead of a single clearly superior propulsion system, each means of propulsion may be favored depending upon the specified program policy and the extent of the desired manned flight time. Furthermore, the effect which aerobraking and multiple transfer cycles have upon mission feasibility is considered. 18 refs