[en] Advancement of U.S. scientific, security, and economic interests through a robust space exploration program requires high performance propulsion systems to support a variety of robotic and crewed missions beyond low Earth orbit. In NASA's recent Mars Design Reference Architecture (DRA) 5.0 study (NASA-SP-2009-566, July 2009), nuclear thermal propulsion (NTP) was again selected over chemical propulsion as the preferred in-space transportation system option because of its high thrust and high specific impulse (-900 s) capability, increased tolerance to payload mass growth and architecture changes, and lower total initial mass in low Earth orbit. An extensive nuclear thermal rocket technology development effort was conducted from 1955-1973 under the Rover/NERVA Program. The Small Nuclear Rocket Engine (SNRE) was the last engine design studied by the Los Alamos National Laboratory during the program. At the time, this engine was a state-of-the-art design incorporating lessons learned from the very successful technology development program. Past activities at the NASA Glenn Research Center have included development of highly detailed MCNP Monte Carlo transport models of the SNRE and other small engine designs. Preliminary core configurations typically employ fuel elements with fixed fuel composition and fissile material enrichment. Uniform fuel loadings result in undesirable radial power and temperature profiles in the engines. Engine performance can be improved by some combination of propellant flow control at the fuel element level and by varying the fuel composition. Enrichment zoning at the fuel element level with lower enrichments in the higher power elements at the core center and on the core periphery is particularly effective. Power flattening by enrichment zoning typically results in more uniform propellant exit temperatures and improved engine performance. For the SNRE, element enrichment zoning provided very flat radial power profiles with 551 of the 564 fuel elements within 1% of the average element power. Results for this and alternate enrichment zoning options for the SNRE are compared.

[en] A simple new technique for quantitative reduction of water to hydrogen gas for isotopic analysis is described. Individual pyrex glass tubes are used as both reaction vessels (for the reaction of zinc shot with water to give hydrogen), and sample bottles (to transfer hydrogen to the mass spectrometer for analysis). The technique is based on that reported by Coleman et al. (1982), but we have added an additional step, in which the zinc shot and tube is heated to the reaction temperature and the resultant gases are pumped away before the water sample is admitted. Results show good precision and memory effects are almost eliminated

[en] The nuclear thermal rocket (NTR) is one of the leading propulsion options for future human exploration missions because of its high specific impulse (Isp ∼ 850 to 1000 s) and attractive engine thrust-to-weight ratio (∼ 3 to 10). Because only a minuscule amount of enriched ²³⁵U fuel is consumed in an NRT during the primary propulsion maneuvers of a typical Mars mission, engines configured both for propulsive thrust and modest power generation (referred to as 'bimodal' operation) provide the basis for a robust, power-rich stage with efficient propulsive capture capability at the moon and near-earth asteroids (NEAs), where aerobraking cannot be utilized. A family of modular bimodal NTR (BNTR) space transfer vehicles utilize a common core stage powered by three ∼15-klb_f engines that produce 50 kW(electric) of total electrical power for crew life support, high data rate communications with Earth, and an active refrigeration system for long-term, zero-boiloff liquid hydrogen (LH₂) storage. This paper describes details of BNTR engines and designs of vehicles using them for various missions

[en] An analysis of intrathoracic tumor control was carried out in 378 patients with histologically proven unresectable non-oat cell carcinoma of the lung treated with definitive radiotherapy, randomized to one of four treatment regimens: 4000 rad split course (2000 rad in five fractions in one week, two weeks rest and additional 2000 rad in five fractions in one week) or 4000, 5000 or 6000 rad continuous courses, five fractions per week. Between 85 and 101 patients are analyzed in each treatment group. The complete plus partial response was 46-51% in the 4000 rad groups in contrast to 61-66% in the 5000 to 6000 rad groups (P = 0.008). The overall two year survival rate was 10-11% for the patients treated with 4000 rad split or continuous course, and 19% in the patients treated with 5000 to 6000 rad. The complete response in patients with tumors 3 cm or less in diameter was 16% when treated with 4000 rad in contrast to 20-31% in those treated with 5000-6000 rad. In the patients with lesions from 4 to 6 cm in diameter, complete and partial tumor regression was 48% in the 4000 rad group, 67% with 5000 rad, and 71% with 6000 rad. Strict quality assurance criteria in radiotherapy are necessary to achieve optimal treatment results and a careful program to evaluate techniques of irradiation and protocol compliance should be maintained in cooperative group studies in order to enhance the validity of clinical trials

[en] A conceptual vehicle design enabling fast outer solar system travel was produced predicated on a small aspect ratio spherical torus nuclear fusion reactor. Analysis revealed that the vehicle could deliver a 108 mt crew habitat payload to Saturn rendezvous in 204 days, with an initial mass in low Earth orbit of 1630 mt. Engineering conceptual design, analysis, and assessment were performed on all major systems including nuclear fusion reactor, magnetic nozzle, power conversion, fast wave plasma heating, fuel pellet injector, startup/re-start fission reactor and battery, and other systems. Detailed fusion reactor design included analysis of plasma characteristics, power balance and utilization, first wall, toroidal field coils, heat transfer, and neutron/X-ray radiation

[en] The performance of Nuclear Electric Propulsion (NEP) in transporting cargo and propellant from Low Earth Orbit (LEO) to the first Earth-Moon Lagrange point (EML1) is examined. The baseline NEP vehicle utilizes a fission reactor system with Brayton power conversion for electric power generation to power multiple liquid hydrogen magnetoplasmadynamic (MPD) thrusters. Vehicle characteristics and performance levels are based on technology availability in a fifteen to twenty year timeframe. Results of numerical trajectory analyses are also provided

[en] Requirements for propulsion and power systems capable of achieving a safe, reliable, robust and affordable human Mars exploration mission have been identified. Nuclear systems have been identified that can meet the challenges of short trip times, reduced number of launch vehicles, potential for ''all propulsive'' maneuvers, abundant in-space power and low mass, volume and deployed area, and energy rich surface power. Reduced total systems cost will also be mandatory to achieve affordable human exploration of Mars. Hence, it is desirable to design a space propulsion and surface power reactor with the greatest degree of commonality as possible with the goal of reducing total system costs

[en] Portable methanol micro fuel cell systems are becoming promising candidates due to their high energy density. The relevant micro fluid control components must be small to reduce the impact of balance of plant of micro fuel cell energy density. The piezoelectric actuation of microvalve structures is attractive due to the relative simplicity of the actuator design, very little power in static operations, rapid response, and high work energy density. We report on the development of a micro-electro-mechanical systems (MEMS) valve that is designed to meet the planar structure requirement of micro fuel cells. The optimized actuating diaphragm and the valve seat are etched in silicon wafers. A piezoelectric bimorph disc is used to drive the actuating diaphragm and open the outlet of the valve. The pressure differential between the valve chamber and the outlet and the initial pressure are employed to reduce the leak rates. The dimension of the valve is 20mm in diameter and 2mm in thickness. The effective opening force of 2.19N and the maximum effective displacement of 10μm can be produced. The design, simulation, fabrication and performance are presented. (author)

[en] Preliminary analysis was carried out on a prospective randomized cooperative group study involving 375 patients with histologically proven unresectable non-oat cell carcinoma of the lung who were treated with definitive radiotherapy. The patients were randomized to one of four treatment regimens: 4000 rad split course (2000 rad in five fractions one week, two weeks rest and an additional 2000 rad, five fractions in one week) or 4000, 5000 or 6000 rad continuous courses, five fractions per week. The patients who were treated with the split course had the lowest survival compared with the other groups. Complete and partial local tumor regression was 48% in patients who were treated with 4000 rad, 65% in the 5000 rad and 61% in the 6000 rad group. The rate of initial intrathoracic recurrence was 38% in patients who were treated with 6000 rad; 45% in those who received 5000 rad, 51% and 64% with 4000 rad split or continuous course, respectively. Distant metastases concurrent with or prior to intrathoracic failure were significantly higher in the patients with adenocarcinoma or large cell adenocarcinoma (63%) than in epidermoid carcinoma (33%). The present data strongly suggest that patients who were treated with 5000 or 6000 rad had a better response, tumor control and survival than those who were treated with lower doses

[en] Analysis is presented of a prospective randomized study involving 365 patients with histologically proven unresectable non-oat-cell carcinoma of the lung treated with deffinitive radiotherapy. The patients were radomized to one of four treatment regimens: 4000 rad split course, or 4000, 5000, or 6000-rad continuous courses in five fractions per week. Ninety to 100 patients were accessioned to each group. The one-year survival rate is 50% and the two-year survival rate, 25%. The patients treated with the split course have the lowest survival rate in comparison with the other groups. The complete and partial local regression of tumor was 49% in patients treated with 4000 rad and 55% in the groups treated with 5000 and 6000 rad. For patients who achieved complete regression of the tumor following irradiation, the two-year survival rate is 40%, in contrast to 20% for those with partial regression, and no survivors among the patients with stable or progressive disease. The incidence of intrathoracic recurrence was 33% for patients treated with 6000 rad, 39% for those receiving 5000 rad, and 44 to 49% for those treated with a 4000-rad split or continuous course. At present, the data stongly suggest that patients treated with 5000 or 6000 rad have a better response, tumor control, and survival rate than those receiving lower doses. Patients with high performance status or with tumors in earlier stages have a two-year survival rate of approx. 40%, in comparison with 20% for other patients. The various irradiation regimens have been well tolerated, with complications being slightly higher in the 4000-rad split course group and in the 6000-rad continuous course group. The most frequent complications have been pneumonitis, pulmonary fibrosis, and dyspagia due to transient esophagitis. Further investigation will be necessary before the optimal management of patients with bronchogenic carcinoma by irradiation is established