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Topic Review
Alternative Aviation Fuels/Pathways
The Paris Agreement’s objectives related to climate change put aviation under great pressure and environmental inspection. In particular, the aviation industry is committed to achieving a 50% reduction in CO2 emissions by 2050 compared to 2005 levels. A shift to alternative aviation fuels seems imperative. The International Air Transport Association (IATA) has identified the production of drop-in sustainable liquid fuels (SAFs) as the most promising strategy, at least short term, to reduce the environmental impact of the sector.
  • 2.8K
  • 03 Mar 2023
Topic Review
Propellant Depot
An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space. It is one of the types of space resource depots that have been proposed for enabling infrastructure-based space exploration. Many different depot concepts exist depending on the type of fuel to be supplied, location, or type of depot which may also include a propellant tanker that delivers a single load to a spacecraft at a specified orbital location and then departs. In-space fuel depots are not necessarily located near or at a space station. Potential users of in-orbit refueling and storage facilities include space agencies, defense ministries and communications satellite or other commercial companies. Satellite servicing depots would extend the lifetime of satellites that have nearly consumed all of their orbital maneuvering fuel and are likely placed in a geosynchronous orbit. The spacecraft would conduct a space rendezvous with the depot, or vice versa, and then transfer propellant to be used for subsequent orbital maneuvers. In 2011, Intelsat showed interest in an initial demonstration mission to refuel several satellites in geosynchronous orbit, but all plans have been since scrapped. A low earth orbit (LEO) depot's primary function would be to provide propellant to a transfer stage headed to the moon, Mars, or possibly a geosynchronous orbit. Since all or a fraction of the transfer stage propellant can be off-loaded, the separately launched spacecraft with payload and/or crew could have a larger mass or use a smaller launch vehicle. With a LEO depot or tanker fill, the size of the launch vehicle can be reduced and the flight rate increased—or, with a newer mission architecture where the beyond-Earth-orbit spacecraft also serves as the second stage, can facilitate much larger payloads—which may reduce the total launch costs since the fixed costs are spread over more flights and fixed costs are usually lower with smaller launch vehicles. A depot could also be placed at Earth-Moon Lagrange point 1 (EML-1) or behind the Moon at EML-2 to reduce costs to travel to the moon or Mars. Placing a depot in Mars orbit has also been suggested.
  • 2.7K
  • 22 Nov 2022
Topic Review
Unmanned NASA Missions
Following is a sampling of some of NASA's past and present programs excluding manned spacecraft. The years in brackets are for first and latest launching. A program is a number of flights or missions with the same kind of spacecraft, therefore the name of the program and the name of the spacecraft used will often be the same. In all, NASA have made more than 1,000 unmanned missions into Earth orbit or beyond.
  • 2.7K
  • 23 Oct 2022
Topic Review
Sonic Boom Prediction and Minimization
NASA describes the sonic boom as “thunder-like noise a person on the ground hears when an aircraft […] flies overhead faster than the speed of sound”. Sonic boom results from the coalescence of the shock waves generated by an aircraft flying supersonicly trough their propagation into the atmosphere to the ground.
  • 2.7K
  • 08 Nov 2023
Topic Review
Types of Artificial Neural Networks
The well-known artificial neural networks (ANNs) are nearly as old as Artificial Intelligence, and they represent a tool, or a model, rather than a method by which to implement AI in autonomous systems. The growing interest in Artificial Intelligence is pervading several domains of technology and robotics research. Only recently has the space community started to investigate deep learning methods and artificial neural networks for space systems. The applications of artificial neural networks to system identification, control synthesis and optical navigation are reviewed and compared using quantitative and qualitative metrics. 
  • 2.7K
  • 27 Sep 2022
Topic Review
Friction Stir Welding
Friction stir welding is a method of materials processing that enables the joining of similar and dissimilar materials. The process, as originally designed by The Welding Institute (TWI), provides a unique approach to manufacturing—where materials can be joined in many designs and still retain mechanical properties that are similar to, or greater than, other forms of welding. This process is not free of defects that can alter, limit, and occasionally render the resulting weld unusable. 
  • 2.6K
  • 17 Dec 2021
Topic Review
Ozone Depletion by Rocket Launches
Rocket launches used for space exploration continue to gain popularity as the human population grows and technology advances toward the future. Large increases in rocket launch demand could come about for a variety of reasons, including national decisions regarding security, space exploration, significant reductions in launch costs, or the emergence of new markets such as space tourism, manufacturing, or solar power. Rocket launches can affect the natural environment, most specifically the composition of the atmosphere as they travel through it. A major environmental problem faced today is the depletion of the ozone layer in the atmosphere by rockets and other molecular species such as chlorofluorocarbons. Up to forty percent of the total ozone present in the wake of a rocket is destroyed from rocket plumes. Ozone concentrations are calculated using ultraviolet and visible light radiometers attached to rockets. Calculations analyzed from these radiometers are where scientists first noticed the depletion of ozone caused by rockets.
  • 2.5K
  • 01 Nov 2022
Topic Review
Europa Lander (NASA)
The Europa Lander is a proposed astrobiology mission concept by NASA to Europa, an icy moon of Jupiter. If funded and developed as a Flagship mission, it would be launched in 2025 to complement the studies by the Europa Clipper orbiter mission and perform analyses on site. The objectives of the mission are to search for biosignatures at the subsurface ≈10 cm, to characterize the composition of non-ice near-subsurface material, and determine the proximity of liquid water and recently erupted material near the lander's location.
  • 2.5K
  • 28 Oct 2022
Topic Review
Gravity Recovery and Climate Experiment
File:15 Years of Freshwater Trends Seen by GRACE.webm The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center. Twin satellites took detailed measurements of Earth's gravity field anomalies from its launch in March 2002 to the end of its science mission in October 2017. By measuring gravity anomalies, GRACE showed how mass is distributed around the planet and how it varies over time. Data from the GRACE satellites is an important tool for studying Earth's ocean, geology, and climate. GRACE was a collaborative endeavor involving the Center for Space Research at the University of Texas at Austin, NASA's Jet Propulsion Laboratory, the German Aerospace Center and Germany's National Research Center for Geosciences, Potsdam. The Jet Propulsion Laboratory was responsible for the overall mission management under the NASA ESSP (Earth System Science Pathfinder) program. The principal investigator is Byron Tapley of the University of Texas Center for Space Research, and the co-principal investigator is Christoph Reigber of the GeoForschungsZentrum (GFZ) Potsdam. The two GRACE satellites (GRACE-1 and GRACE-2) were launched from Plesetsk Cosmodrome, Russia, on a Rockot (SS-19 + Breeze upper stage) launch vehicle on 17 March 2002. The spacecraft were launched to an initial altitude of approximately 500 km at a near-polar inclination of 89°. During normal operations, the satellites were separated by 220 km along their orbit track. This system was able to gather global coverage every 30 days. GRACE far exceeded its 5-year design lifespan, operating for 15 years until the decommissioning of GRACE-2 on 27 October 2017. Its successor, GRACE-FO, was successfully launched on 22 May 2018.
  • 2.4K
  • 06 Oct 2022
Topic Review
YOLO-Based Unmanned Aerial Vehicle Technology
YOLO-based unmanned aerial vehicle (UAV) technology is proposed in the context of interdisciplinary or multi-disciplinary collaborative research, by the cross-fertilization of You Only Look Once (YOLO) target detection algorithms and UAV technology. In this YOLO-based UAV technology, the UAV can provide more application scenarios for the YOLO algorithm, while the YOLO algorithm can assist the UAV with more novel tasks. The two can complement each other to further facilitate people's daily lives while contributing to the productivity of their respective industries.
  • 2.4K
  • 06 Apr 2023
Topic Review
Long-Term Space Nutrition
Nutrition has many important functions in space travel, from providing enough nutrients and meeting the metabolic needs of a healthy body to enhancing an individual’s emotional well-being. Nutrition also plays a key role in offsetting many negative effects of space travel, such as radiation exposure, immune deficiency, oxidative stress, and bone and muscle loss.
  • 2.3K
  • 30 Jan 2022
Topic Review
Developing a Finite Element Model through LS-DYNA
Robust finite element models are utilised for their ability to predict simple to complex mechanical behaviour under certain conditions at a very low cost compared to experimental studies, as this reduces the need for physical prototypes while allowing for the optimisation of components. 
  • 2.3K
  • 28 Mar 2022
Topic Review
Structural Health Monitoring Systems
Structural health monitoring (SHM) is a rapidly evolving field, and there is a vast literature covering several topics that are related to this field. This entry is focused on the analysis of the state of the art of sensors for guided ultrasonic waves for the detection and localization of impacts for structural health monitoring (SHM).
  • 2.3K
  • 06 May 2021
Topic Review
Speckle Imaging
Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("image stacking") method and the speckle interferometry methods. These techniques can dramatically increase the resolution of ground-based telescopes, but are limited to bright targets.
  • 2.3K
  • 22 Nov 2022
Topic Review
List of Soviet Manned Space Missions
This is a list of the manned space missions conducted by the Soviet space programme. These missions belong to the Vostok, Voskhod, and Soyuz space programs. Note: Soviet manned space missions had not any official patches before Apollo–Soyuz program. After that and until Soyuz TM-12 "Juno" flight mission patches had been designed only for international missions.
  • 2.3K
  • 06 Dec 2022
Topic Review
Advancements of Rim-Driven Fans in Aerial Vehicles
As the aviation industry seeks sustainable propulsion solutions, innovative technologies have emerged, among which rim-driven fan (RDF) systems hold notable promise. Amid escalating concerns about greenhouse gas emissions, the aviation sector’s shift towards electric propulsion has gained impetus. RDF technology has emerged as a beacon of optimism, heralding the prospect of energy-efficient and eco-conscious air travel. 
  • 2.2K
  • 22 Dec 2023
Topic Review
Satellite Navigation Signal Authentication Principles and Technical Architecture
As the Global Navigation Satellite System (GNSS) is widely used in all walks of life, the signal structure of satellite navigation is open, and the vulnerability to spoofing attacks is also becoming increasingly prominent, which will seriously affect the credibility of navigation, positioning, and timing (PNT) services. Satellite navigation signal authentication technology is an emerging technical means of improving civil signal anti-spoofing on the satellite navigation system side, and it is also an important development direction and research focus of the GNSS. 
  • 2.2K
  • 12 Apr 2023
Topic Review
Studied Space Shuttle Variations and Derivatives
During the lifetime of NASA's Space Shuttle, Rockwell International and many other organizations studied different Space Shuttle variations and derivatives. These studies included different ways to increase shuttle payload capability, crew capacity, and developing standalone reusable launch vehicles. A large focus of the program was towards new shuttle boosters and an upgrades to the external tank but also looked to expand NASA's ability to launch deep space missions and build large modular space stations. Many of these concepts and studies would shape the concepts and programs of the 2000s such as Constellation, Orbital Space Plane Program, and Artemis program.
  • 2.2K
  • 08 Oct 2022
Topic Review
Quadjet
A quadjet or four-engine jet is a jet aircraft powered by four engines. The presence of four engines offers increased power output and redundancy, allowing quadjets to be used as civilian airliners, freighters and military aircraft. Many of the first purpose-built jetliners were quadjets, among which stands the De Havilland Comet, the world's first commercial jetliner. In the past two decades, the use of quadjet airliners has gradually begun to decline due to a variety of factors, including the approval of twinjets to fly further from diversion airports and an increased emphasis on fuel efficiency.
  • 2.2K
  • 24 Nov 2022
Topic Review
Mohammed Bin Rashid Space Centre
The Mohammed Bin Rashid Space Centre (MBRSC) (Arabic: مركز محمد بن راشد للفضاء), is a Dubai government organisation working on the UAE space program, which includes various space satellite projects, the Emirates Mars Mission, and the UAE astronaut programme. The centre actively works to promote space science and research in the region. The centre encompasses the Emirates Institution for Advanced Science and Technology (EIAST).
  • 2.2K
  • 25 Oct 2022
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