A method of approximating propellant requirements of low-thrust trajectories

Method of approximating propellant requirements of low thrust trajectorie

Single thrust period missions to Uranus for unmanned nuclear-electric propulsion systems

The effects of trip time, propulsion time, and specific powerplant mass are studied for optimized unmanned probe spacecraft on missions to Uranus with nuclear-electric propulsion systems. Electric propulsion is confined to a single thrust period at the beginning of each mission. Mission profiles include both high-thrust and electric-propulsion Earth-departure modes for planet flyby and orbital capture. Effects of propulsion time and propulsion system parameters are evaluated, and typical design features of the nuclear-electric spacecraft are outlined. Payload capability comparisons are made with systems employing ballistic transfer and solar-electric propulsion

Solar-Electric Propulsion Probes for Exploring the Solar System

Payload capability of unmanned interplanetary probes using solar electric propulsio

An Improved Prediction Method for Noise Generated by Conventional Profile Coaxial Jets

A semiempirical model for predicting the noise generated by conventional velocity profile jets exhausting from coaxial nozzles is presented and compared with small scale static and simulated flight data. Improvements to the basic circular jet noise prediction are developed which improve the accuracy, especially at high jet velocity and near the jet axis

Manned Mars landing missions using electric propulsion

Manned Mars landing missions using electric propulsion - evaluation of various mission profile

Preliminary study of propulsion systems and airplane wing parameters for a US Navy subsonic V/STOL aircraft

Two V/STOL propulsion concepts were evaluated in a common aircraft configuration. One propulsion system consists of cross coupled turboshaft engines driving variable pitch fans. The other system is a gas coupled combination of turbojet gas generators and tip turbine fixed pitch fans. Evaluations were made of endurance at low altitude, low speed loiter with equal takeoff fuel loads. Effects of propulsion system sizing, bypass ratio, and aircraft wing planform parameters were investigated and compared. Shaft driven propulsion systems appear to result in better overall performance, although at higher installed weight, than gas systems

The Role of HE4 in Ovarian Cancer Follow-up: A Review.

Objective: The aim of this review was to analyze the state of the art about HE4 and follow-up in patients treated for ovarian cancer. Methods: A literature search was conducted in the MEDLINE database using the key words "HE4" and "ovarian cancer" and "recurrence" or "relapse" or "follow up." Results: Seven of 28 clinical studies were selected. Four studies were prospective, and all of them were based on a small number of patients (8Y73 women). A failure of HE4 levels to normalize at completion of standard therapy may indicate a poor prognosis, thus suggesting the need of a closer follow-up. Moreover, HE4 showed better sensibility and specificity in the diagnosis of ovarian cancer recurrence with respect to CA-125, being also an earlier indicator of the relapse with a lead time of 5 to 8 months. HE4 showed a better performance in this setting if performed in association with other markers (CA-125, CA-72.4). HE4 seems to be an independent predictive factor for the surgical outcome at secondary cytoreductive surgery and to maintain its prognostic role even after the recurrence. Conclusions: These preliminary data start to suggest a superiority of HE4 over CA-125 in the detection of ovarian cancer recurrence. Moreover, the prognostic role of HE4 could help clinicians to personalize the follow-up program, whereas its predictive role could be useful to plan the treatment of the relapse. The role of HE4 in ovarian cancer follow-up deserves to be further investigated in prospective randomized multicentric studies

An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star

We describe optical photometric and spectroscopic observations of the bright variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a period of 91.645 days. A deep primary eclipse is visible for wavelengths < 4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse timings and the radial velocity curve of the K0 secondary star indicate an interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The primary star is either an early B-type star or a black hole. If it did contain a black hole, BG Gem would be the longest period black hole binary known by a factor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A

Follow-up observations of pulsating subdwarf B stars: Multisite campaigns on PG 1618+563B and PG 0048+091

We present follow-up observations of pulsating subdwarf B (sdB) stars as part of our efforts to resolve the pulsation spectra for use in asteroseismological analyses. This paper reports on multisite campaigns of the pulsating sdB stars PG 1618+563B and PG 0048+091. Data were obtained from observatories placed around the globe for coverage from all longitudes. For PG 1618+563B, our five-site campaign uncovered a dichotomy of pulsation states: Early during the campaign the amplitudes and phases (and perhaps frequencies) were quite variable while data obtained late in the campaign were able to fully resolve five stable pulsation frequencies. For PG 0048+091, our five-site campaign uncovered a plethora of frequencies with short pulsation lifetimes. We find them to have observed properties consistent with stochastically excited oscillations, an unexpected result for subdwarf B stars. We discuss our findings and their impact on subdwarf B asteroseismology.Comment: 50 pages including 17 figures and 10 tables. Accepted for publication in the Astrophysical Journa