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A Place in Space: Marking Emptiness
Published in Jai Galliott, Commercial Space Exploration, 2016
How does a satellite reach and keep its place in the GEO? We know that satellites are launched using shuttles and are undocked in their slots. Using tiny movements to control them, they are placed in their positions and at angles of the right inclination. Though a satellite in its geostationary orbit continues to rotate around the Earth, it tends to wobble and slowly be drawn towards the Earth’s surface little by little (it may take years). This is called orbital decay. If the satellite comes close enough to the Earth, it may re-enter the Earth’s atmosphere and burn up or crash into the surface of the Earth. Orbital decay can be measured and calculated, so tiny rockets are fired regularly to keep the satellites at the right distance from the Earth and maintain its place in the slot for coverage and non-interference from adjoining satellites. The wobbling and orbital decay of satellites becomes a significant form of displacement. As long as the satellite is functioning, the countries are bound to restore the satellites back to their orbits. But once the satellites cease functioning, they are to be placed permanently in a safe high Earth orbit (HEO) according to international regulations. Another kind of place in space is created by HEO called junkyard orbital or ‘graveyard orbit’. Unlike the strict requirements of distances between the satellites in the slots of GEO, the main requirement is that the satellite be moved about 300 kms beyond GEO (Jehn et al. 2005, p. 37).
Batteries and alternative sources of energy
Published in John Bird, Science and Mathematics for Engineering, 2019
(viii) Solar Power Satellite: A solar power satellite (SPS) is a proposed satellite built in high Earth orbit that uses microwave power transmission to beam solar power to a very large antenna on Earth where it can be used in place of conventional power sources. The advantage of placing the solar collectors in space is the unobstructed view of the sun, unaffected by the day/night cycle, weather or seasons. However, the costs of construction are very high, and SPSs will not be able to compete with conventional sources unless low launch costs can be achieved or unless a space-based manufacturing industry develops and they can be built in orbit from off-earth materials.
Batteries and alternative sources of energy
Published in John Bird, Electrical and Electronic Principles and Technology, 2017
Solar Power Satellite: A solar power satellite (SPS) is a proposed satellite built in high Earth orbit that uses microwave power transmission to beam solar power to a very large antenna on Earth where it can be used in place of conventional power sources. The advantage of placing the solar collectors in space is the unobstructed view of the sun, unaffected by the day/night cycle, weather or seasons. However, the costs of construction are very high, and SPSs will not be able to compete with conventional sources unless low launch costs can be achieved or unless a space-based manufacturing industry develops and they can be built in orbit from off-earth materials.
Preliminary Results for In-Situ Alternative Propellants for Nuclear Thermal Propulsion
Published in Nuclear Technology, 2022
Dennis Nikitaev, L. Dale Thomas
A code was constructed that utilized the Ideal Rocket Equation and was used to analyze the required travel time to and from Mars using the AR Mars conjunction class mission architecture.40Figure 6 shows the concept of operations (CONOPS) of AR’s conjunction class Mars Transfer Vehicle (MTV) mission architecture. Aerojet Rocketdyne currently models the conjunction class MTV stages to be injected into the highly elliptical Lunar Distant High Earth Orbit (LDHEO) and be transferred via reaction control systems to the Near Rectilinear Halo Orbit (NRHO). The launch vehicle of choice is the Space Launch System (SLS). The conjunction class MTV consists of a core stage with three H-NTP engines and some propellant, three inline stages with propellant and maneuvering systems, and a habitat. The analysis on this model has yielded transfer times to and from Mars of 160 days each way. However, these transfer times do not incorporate orbit insertion and parking orbit arrivals. The sum of all these transfer times yields around 356 days. Figure 7 shows the burn schedule and baseline vehicle architecture with a breakdown of the masses, propellant mass allocations, and burn schedule that is used for analysis.41
Connected Geomatics in the big data era
Published in International Journal of Digital Earth, 2018
A precise and unique spatial datum system provides the foundation for geospatial data processing and information services. The ideal implementation of the spatial datum system is the terrestrial reference frame (TRF), which consists of a series of fixed reference stations on the surface of the earth that are expressed as the coordinates and velocity fields of these reference stations at an epoch. At present, the TRF usually only considers the linear velocities of these reference stations (Song, Zhu, and Xiong 2009). In fact, the motion of a reference station includes both linear and non-linear components. A reference frame that only considers the linear velocity of the reference station gives only centimeter-precision. In the big data era, Geomatics should provide a precise TRF to massive data derived from ubiquitous sensors for subsequent processing and analysis. Technologies for establishment and maintenance of a TRF considering non-linear variation should be developed. By combining the data from various high earth orbit, medium earth orbit, and LEO satellites, with the observation data from the static ground tracking station, non-linear TRF works can be developed and maintained. Three problems still remain to be addressed in order to construct this framework: Theories and methods to establish a global unified epoch TRF work based on comprehensive multi-source observation techniques;Analysis of time-varying characteristics of earth structural and non-structural influencing factors involved in a non-linear TRF work;Theoretical methods and implementation techniques for non-linear motion prediction models of a global dynamic terrestrial framework.
Using spatial radio wave field processing for diagnostics of inhomogeneous plasma
Published in Waves in Random and Complex Media, 2021
To obtain physical characteristics of the inhomogeneous structure, when calculating the time of synthesis of the transmitting antenna array in the satellite radio tomography we should take into account the relaxation time and the drift velocity of the inhomogeneous structure considered, which can be as high as 270 m/s [1,21,22]. In this case, low earth orbit satellite systems are more preferable than high earth orbit navigation systems due to the higher speed of the satellites.