1,863 research outputs found
Space Transportation System/Cargo Mass Properties Calculation Using an Interactive System
The methodology used to perform STS cargo mass properties calculations using an interactive computer system is described
Space fusion energy conversion using a field reversed configuration reactor: A new technical approach for space propulsion and power
The fusion energy conversion design approach, the Field Reversed Configuration (FRC) - when burning deuterium and helium-3, offers a new method and concept for space transportation with high energy demanding programs, like the Manned Mars Mission and planetary science outpost missions require. FRC's will increase safety, reduce costs, and enable new missions by providing a high specific power propulsion system from a high performance fusion engine system that can be optimally designed. By using spacecraft powered by FRC's the space program can fulfill High Energy Space Missions (HESM) in a manner not otherwise possible. FRC's can potentially enable the attainment of high payload mass fractions while doing so within shorter flight times
Probing the Nature of Ultra-Steep Spectrum Radio Sources
Here we present, first results from e-VLBI observations at 18 cm on a small sample of ultra-steep spectrum sources (spectral index between 74 MHz and 325 MH
Deceleration of Relativistic Radio Components and the morphologies of Gigahertz Peaked Spectrum Sources
A relativistic radio component, which moves in a direction close to the sky
plane, will increase in flux density when it decelerates. This effect is the
basis for the qualitative model for GPS galaxies we present in this paper,
which can explain their low-variability convex spectrum, their compact double
or compact symmetric morphology, and the lack of GPS quasars at similar
redshifts. Components are expelled from the nucleus at relativistic speeds at a
large angle to the line of sight, and are decelerated (eg. by ram-pressure or
entrainment of the external gas) before contributing to a mini-lobe. The young
components are Doppler boosted in the direction of motion but appear fainter
for the observer. The non-relativistic mini-lobes dominate the structure and
are responsible for the low variability in flux density and the convex radio
spectrum as well as the compact double angular morphology. Had the same source
been orientated at a small angle to the line of sight, the young components
would be boosted in the observer's direction resulting in a flat and variable
radio spectrum at high frequencies. Hence the characteristic convex spectrum of
a GPS source would not be seen. These sources at small angles to the line of
sight are probably identified with quasars, and are not recognized as GPS
sources, but are embedded in the large population of flat spectrum variable
quasars and BL Lac objects. This leads to a deficiency in GPS/CSOs identified
with quasars.Comment: 11 pages, LaTeX, accepted by A&A 26/Jan/199
LOFAR: A new radio telescope for low frequency radio observations: Science and project status
LOFAR, the Low Frequency Array, is a large radio telescope consisting about
100 soccer field sized antenna stations spread over a region of 400 km in
diameter. It will operate in the frequency range from ~10 to 240 MHz, with a
resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will
allow for a broad range of astrophysical studies. In this contribution we first
discuss four major areas of astrophysical research in which LOFAR will
undoubtedly make important contributions: reionisation, distant galaxies and
AGNs, transient radio sources and cosmic rays. Subsequently, we will discuss
the technical concept of the instrument and the status of the LOFAR projectComment: 8 pages, 2 figures, to appear in the proceedings of the XXI Texas
Symposium on Relativistic Astrophysics held on December 9--13 2002, in
Florence, Ital
Inertial electrostatic confinement as a power source for electric propulsion
The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant. However, an alternate approach is considered, using the IEC to drive a 'conventional' electric thruster unit. This has the advantage of building on the rapidly developing technology for such thrusters, which operate at higher specific impulse. Key issues related to this approach include the continued successful development of the physics and engineering of the IEC unit, as well as the development of efficient step-down dc voltage transformers. The IEC operates by radial injection of energetic ions into a spherical vessel. A very high ion density is created in a small core region at the center of the vessel, resulting in extremely high fusion power density in the core. Experiments at the U. of Illinois in small IEC devices (is less than 60 cm. dia.) demonstrated much of the basic physics underlying this concept, e.g. producing 10(exp 6) D-D neutrons/sec steady-state with deuterium gas flow injection. The ultimate goal is to increase the power densities by several orders of magnitude and to convert to D-He-3 injection. If successful, such an experiment would represent a milestone proof-of-principle device for eventual space power use. Further discussion of IEC physics and status are presented with a description of the overall propulsion system and estimated performance
- …