Solar thermal rocket

A solar thermal rocket is a theoretical spacecraft propulsion system that would make use of solar power to directly heat reaction mass, and therefore would not require an electrical generator, like most other forms of solar-powered propulsion do. The rocket would only have to carry the means of capturing solar energy, such as concentrators and mirrors. The heated propellant would be fed through a conventional rocket nozzle to produce thrust. Its engine thrust would be directly related to the surface area of the solar collector and to the local intensity of the solar radiation. In the shorter term, solar thermal propulsion has been proposed both for longer-life, lower-cost, more efficient use of the sun and more-flexible cryogenic upper stage launch vehicles and for on-orbit propellant depots. Solar thermal propulsion is also a good candidate for use in reusable inter-orbital tugs, as it is a high-efficiency low-thrust system that can be refuelled with relative ease. There are two solar thermal propulsion concepts, differing primarily in the method by which they use solar power to heat up the propellant: Indirect solar heating involves pumping the propellant through passages in a heat exchanger that is heated by solar radiation. The windowless heat exchanger cavity concept is a design taking this radiation absorption approach. Direct solar heating involves exposing the propellant directly to solar radiation. The rotating bed concept is one of the preferred concepts for direct solar radiation absorption; it offers higher specific impulse than other direct heating designs by using a retained seed (tantalum carbide or hafnium carbide) approach. The propellant flows through the porous walls of a rotating cylinder, picking up heat from the seeds, which are retained on the walls by the rotation. The carbides are stable at high temperatures and have excellent heat transfer properties. Due to limitations in the temperature that heat exchanger materials can withstand (approximately 2800 K), the indirect absorption designs cannot achieve specific impulses beyond 900 seconds (9 kN·s/kg = 9 km/s) (or up to 1000 seconds, see below).

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Rocket propellant

Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines. Rockets create thrust by expelling mass rear-ward, at high velocity. The thrust produced can be calculated by multiplying the mass flow rate of the propellants by their exhaust velocity relative to the rocket (specific impulse).

Rocket engine nozzle

A rocket engine nozzle is a propelling nozzle (usually of the de Laval type) used in a rocket engine to expand and accelerate combustion products to high supersonic velocities. Simply: propellants pressurized by either pumps or high pressure ullage gas to anywhere between two and several hundred atmospheres are injected into a combustion chamber to burn, and the combustion chamber leads into a nozzle which converts the energy contained in high pressure, high temperature combustion products into kinetic energy by accelerating the gas to high velocity and near-ambient pressure.

Orbital maneuver

In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth (for example those in orbits around the Sun) an orbital maneuver is called a deep-space maneuver (DSM). The rest of the flight, especially in a transfer orbit, is called coasting.

What Makes for Automatic Reconstruction of Pulmonary Segments

Jiancheng Yang, Li Zhang, Hongwei Li, Bo Du, Jingyu Li

3D reconstruction of pulmonary segments plays an important role in surgical treatment planning of lung cancer, which facilitates preservation of pulmonary function and helps ensure low recurrence rates. However, automatic reconstruction of pulmonary segmen ...

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Thermomechanical behavior of underground energy infrastructures

Jacopo Zannin

The employment of geostructures as structural supports and as heat exchangers represent an effective, renewable and sustainable way to satisfy thermal needs of the built environment. The structural support of conventional geotechnical structures is coupled ...

EPFL2020

Who's On Board? Probabilistic Membership for Real-Time Distributed Control Systems (Extended)

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To increase their dependability, distributed control systems (DCSs) need to agree in real time about which hosts have crashed, i.e., they need a real-time membership service. In this paper, we prove that such a service cannot be implemented deterministical ...

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Untitled ENG-510: Space propulsion

Slingshot Maneuver MOOC: Space Mission Design and Operations

Explores the slingshot maneuver in space mission design using real mission examples.

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Explores spacecraft propulsion principles, including thrust, acceleration, efficiency, and chemical propulsion in space mission design.