Reviews

The Millionaire Academy Review

The Millionaire Academy Review

EMP Protocol Review

EMP Protocol Review

Articles

Propellant Processing And Manufacture

Casting Molds For Double Base Propellant

The manufacture of solid propellant involves complex physical and chemical processes. In the past, propellant has been produced by several different processes, including the compaction or pressing of powder charges, extrusion of propellant through dies under pressure using heavy presses, and mixing with a solvent which is later evaporated. Even for the same type of propellant e.g., double-base, composite, or composite double-base the fabrication processes are usually not identical for different...

Propellant Grain And Grain Configuration

Solid Propellant Grain Configuraton

The grain is the shaped mass of processed solid propellant inside the rocket motor. The propellant material and geometrical configuration of the grain determine the motor performance characteristics. The propellant grain is a cast, molded, or extruded body and its appearance and feel is similar to that of hard rubber or plastic. Once ignited, it will burn on all its exposed surfaces to form hot gases that are then exhausted through a nozzle. A few rocket motors have more than one grain inside a...

Es Reids Solar Observato

Spectrohelioscope Spherical

In solar work, there is a less-frequently used alternative to the conventional large telescope on an equatorial mounting in a dome, as exemplified by Dave Tyler's setup. Es Reid's setup, based on a heliostat and fixed spectrohelioscope, is a good example of this. This arrangement follows the example of professional astronomers, who often use such complicated and extensive equipment to analyse the light of celestial objects that it cannot be carried on a moving telescope. The solution, then, is...

Plato And Saving The Appearances

The guiding themata or paradigm of Greek planetary astronomy is attributed to Plato by the philosopher Simplicius of Athens in his commentary on Aristotle's book On the Heavens. Around a.d. 500 Simplicius wrote that Plato had set as a task for astronomers to explain the apparently irregular motions of the planets, the Sun, and the Moon as a combination of circular motions with constant speeds of rotation. To save the appearances with a system of uniform circular motions is, in the context of...

Orion Optics Uk Omc 140 200 250 300 and 350 Maksutov Cassegrains

Orion optics in the United Kingdom (no relation to the U.S. company) has been turning out excellent Maksutov Cassegrains for quite a while. The company tested the waters 10 years ago with a 5 -inch model, the OMC140 (Plate 32) and then expanded MCT production to offer a whole line of Maks in apertures of 8-, 10-, 12-, Plate 32. (Orion UK OMC140 MCT) Orion Optics UK's upscale but reasonably priced MCT, the 140mm OMC 140. Credit Image courtesy of Orion Optics U.K. and 14-inches the OMC 200, 250,...

Spherical Aberration N Telescope

Spharical Aberration Caustic Horn

Focused patterns for 0, 1 8, 1 4,1 3,1 2, and 1.7 wavelengths of lower-order spherical aberration. The aperture is unobstructed. a) normal, OB 33 b) SA -1 8 7 a) normal, OB 33 b) SA -1 8 7 Fig. 10-8. In-focus patterns for a) 0, b) 1 8, c) 1 4, d) 1 3, e) 1 2, and f) 1.7 wavelengths of lower-order spherical aberration. Aperture has a 33 centered circular obstruction. Fig. 10-8. In-focus patterns for a) 0, b) 1 8, c) 1 4, d) 1 3, e) 1 2, and f) 1.7 wavelengths of lower-order spherical...

The Egyptian Constellations

Bedford Star Constellations

Considering the way that the Egyptian astronomers have been treated by the academic world until recently, it is not surprising that the problem of the Egyptian constellations is still far from being solved. Two historical figures who are often the subject of disputable speculations are the female pharaoh Hatschepsut and her architect Semnut. Many historians believe that they had a romantic affair, but more importantly their names are linked for eternity because we owe to them one of the most...

Egyptian constellations

Southern Circumpolar Constellations

The Egyptians developed their own constellation system based on important gods and animals in their mythology, although it was not as extensive as in other cultures. For example, historian and mathematician Hugh Thurston (1996) mentions an Egyptian catalog of the universe dating to about 1100 bc that lists only five constellations, two of which are similar to our Orion and Ursa Major. Of course, if one includes the decan star groups, then this number jumps by 36. Figure 2.6. A pull-out plate of...

Eudoxus And Concentric Spheres

Concentric Spheres Aristotle

Plato encouraged a new approach to astronomy to devise a combination of uniform circular motions to reproduce the observed motions in the heavens. Whether the Platonic paradigm would die in infancy or grow in strength depended, in part, on the support it received. Greek society supported playwrights when the citizens of Athens paid to see the productions of Aeschylus, Sophocles, and Euripides and prizes were awarded at festivals to poets and musicians. No city held geometry in high regard,...

Reflective Telescopes

Active Optical System Astronomy

Nicolas Zucchi 132, 170 made the first attempt to build a reflecting telescope in 1616, i.e. soon after Galileo developed the refractor. He states that he procured a bronze concave mirror executed by an experienced and careful artist in the trade and used it directly with a Galilean eyepiece. In order to avoid obstruction by the observer's head, his design introduced a significant beam deviation at the mirror, similarly to the front-view type later introduced by W. Herschel. Depending on the...

Propellant Grain Stress And Strain

Propellant Dewetting

The objective of stress analysis of rocket motors is to design the configuration of the grain, the liners, or the grain support in such a way that excessive stresses or excessive strains will not occur and so that there will be no failure. Static and dynamic loads and stresses are imposed on the propellant grains during manufacture, transportation, storage, and operation. Structurally, a rocket motor is a thin shell of revolution (motor case) almost completely filled with a vis- coelastic...

Astro Webcam Manufacturers

In the last few years a number of custom companies have sprung up in response to the need for affordable CCD imaging for those amateur astronomers with a tight budget. In many cases the products offered have simply been modified webcams, altered by a few wiring changes such that long, if noisy, exposures are possible, making webcams suitable for deep sky imaging. By stacking hundreds of frames, the noise has been reduced to acceptable levels for exposures of 30 seconds or so often the unguided...

Solid angle on the celestial sphere

Solid Angle

The concept of solid angle Q is fundamental to all of astronomy. It is simply an angular area on the sky, or equivalently, on the celestial sphere. This area can be expressed as square degrees or square radians the latter unit is called the The solid angle is expressed in terms of two angular displacements, e.g., d9 and d0 in Fig. 7. The beam of an antenna, e.g., 1 x 1 , or 1x 2, or a fan beam of 1 x 100 can be characterized by its solid angle, approximately 1 deg2, 2 arcsec2, and 100 deg2 for...

Planetary Imagers Worldwide

Grafton Planet Images

Despite the ease with which excellent planetary images can now be obtained, planetary imagers are rather thin on the ground among the population. Across the world there are only a few dozen regular planetary imagers whose results are good enough to be used by professional astronomers. Undoubtedly the main reason for this is simply the rarity of good, stable, atmospheric seeing coupled with clear skies, along with the dedication and knowledge required to get world-class results. However, a few...

Pinched and Deformed Optics

Monta Pasa Nadrynnowego Podrynnowego

At the start of each observing session, you should star test for problems that may change with transport of the telescope or a remounting of the optics after maintenance. This chapter will discuss the star-test pattern characteristic of one such warping and will present ways to relieve unusual stresses on the optics. Beyond the image improvements derived by giving careful attention to the deformations, you may be able to avoid catastrophic damage. Edge fractures are common among mirrors with...

Turbopump Feed Systems And Engine Cycles

Flight Arc

The principal components of a rocket engine with one type of turbopump system are shown in the simplified diagram of Fig. 1-4. Here the propellants are pressurized by means of pumps, which in turn are driven by turbines. These turbines derive their power from the expansion of hot gases. Engines with turbopumps are preferred for booster and sustainer stages of space launch vehicles, long-range missiles, and in the past also for aircraft performance augmentation. They are usually lighter than...

Chemical Rocket Propulsion

Rocket Propulsion Flow Scheme

The energy from a high-pressure combustion reaction of propellant chemicals, usually a fuel and an oxidizing chemical, permits the heating of reaction product gases to very high temperatures 2500 to 4100 C or 4500 to 7400 F . These gases subsequently are expanded in a nozzle and accelerated to high velocities 1800 to 4300 m sec or 5900 to 14,100 ft sec . Since these gas temperatures are about twice the melting point of steel, it is necessary to cool or insulate all the surfaces that are exposed...

The Selenelion Or Horizontal Lunar Eclipse

Selenelion

If you are interested in experiencing something that very few other eclipse watchers have seen, this event in 2003 may provide you with an opportunity. If you were in one of those zones where the eclipse is in progress at moonrise or moonset you have the peculiar chance to be able to see both the Sun and the eclipsed Moon in the sky at the same time, with a quick twist of the head. An eclipse occurs when the two celestial orbs are 180 degrees apart, with the Earth in between. The refraction (or...

Explaining the rainbow

How Does Plane Wing Flap Engineering

A complete explanation of the rainbow, couched in the mathematics of the wave theory of light, is not for the fainthearted. Fortunately, it is possible to account for most of its principal features in terms of reflection and refraction of light, without invoking the wave nature of light. People realised long ago that, since rainbows are always seen on the opposite side of the sky from the Sun, they are due to reflected sunlight. But if raindrops reflected light as efficiently as mirrors,...

Circular Zones and Turned Edges

This chapter discusses zonal defects and a common type of zonal error, a turned edge. It will make four chief points 1 On mirrors of amateur size, interior zones are seldom large enough to be troublesome. 2. Zonal defects can be detected by defocusing a larger amount than is usual. 3 Turned edge is a persistent problem that yields contrasts worse than the smaller aperture inside the turned annulus. 4. Narrow turned edges can be treated by masking or painting the edge. Zones are slight circular...

Conditions For 5000n Thrust

Thrust Stage Diagram

What is the ratio of the burning area to the nozzle area for a solid propellant motor with these characteristics Propellant specific gravity 1.71 Temperature sensitivity ap 0.007 (K)1 2. Plot the burning rate against chamber pressure for the motor in Problem 1 using Eq. 11-3 between chamber pressures of 11 and 20 MPa. 3. What would the area ratio Ab At in Problem 1 be if the pressure were increased by 10 (Use curve from Problem 2.) 4. Design a simple rocket motor for the conditions given in...

Architecture of CMOS Image Sensors

Mono Cmos Sensor Read Out Diagram

In addition to the basic concept of active pixels, a number of common features can be found in most CMOS-based imagers. As shown in Fig. 2, two different scanners surround the actual pixel array a vertical scanner to control the row selection, and a horizontal scanner to amplify and multiplex the analog pixel signals. While most CMOS imagers include comparable vertical scanners, they differ quite substantially in the architecture of the horizontal scanner. Low-speed astronomy detectors...

Determining a Centroid

The centroid of a physical object is its barycenter, or center of gravity. It is the point at which the object suspended from a thread or teetering on a fulcrum-balances. In an image, the centroid is the point at which the values of all surrounding pixels are balanced. What makes the centroid interesting is that even though light from a star is spread over many pixels, the distribution of light among them enables us to recover the exact center of the star image within a small fraction of a...

Patrick Moores Observatory in Selsey England

Green Fibre Glass Shed

As I am essentially an observer of the Moon and planets, it may be said that my observatory is of the old-fashioned type, and this is no doubt true enough There are four main telescopes 15 in (380mm), 12.5in (317mm) and 8.5in (216mm) reflectors, and a 5 in (127 mm) refractor. The 15 in reflector has a wooden octagonal tube, partly enclosed, and is on a massive fork mounting there is a revolving head, so that the eyepiece can always be kept in a convenient position, and there are Figure 15.1 The...

Spherical Trigonometry

Spherical Triangle And Great Circle

For the coordinate transformations of spherical astronomy, we need some mathematical tools, which we present now. If a plane passes through the centre of a sphere, it will split the sphere into two identical hemispheres along a circle called a great circle (Fig. 2.1). A line perpendicular to the plane and passing through the centre of the sphere intersects the sphere at the poles P and P'. If a sphere is intersected by a plane not containing the centre, the intersection curve is a small circle....

Big Gun Number 3 Image Intensifiers

Magnetic Focused Image Intensifier

The third and most important weapon in my city viewing arsenal, after the telescope itself, was the purchase of a modern third generation image intensifier, especially made for astronomy the remarkable I3 Piece by Collins Electro Optics . The beauty of the Collins device is that you use it just as you would a conventional eyepiece. Image intensifiers require no image processing, monitors or separate controls. Image intensifiers per se are hardly new to astronomy, and have been written about...

The Pogson Method of Estimating Brightness

Norman Pogson is a well-known variable-star observer from the nineteenth century. He developed a procedure that differs from Argelander's method in that each step is determined to be precisely OTl. This method requires you to compare a variable star with a single comparison star using a previously memorized interval of O'Vl. You then observe the variable again, using a different comparison star. The variable's magnitude is deduced later. Your first observation might be recorded as A - 5,...

Illuminated Reticle Eyepieces

Celestron Micro Guide Reticle

There are now readily available a number of proprietary eyepieces which are supplied by their manufacturers with illuminated reticle systems. They have completely transformed amateur double-star astrome-try.2 The Celestron Micro Guide eyepiece provides a typical example, but other makes are essentially similar this section refers specifically to the Celestron version . Reticle eyepieces of this type require the use of a motor-driven equatorial mount, with remote slow-motion controls to both...

Chinese constellations

Tang Chinese Constellation Map

The Chinese oriented themselves to the north celestial pole, around which all the stars revolved. Our current pole star, Alpha Ursae Minoris (i.e., the brightest star in the constellation of Ursa Minor, in which the Little Dipper is located) was not the pole star to the ancient Chinese due to precession, but other stars received this honor. For example, in the 2nd Millennium bc, Alpha Draconis was the pole star, and Ho et al. (2000) has calculated that a faint star in our constellation of...

Saturn through the Webcam

Saturn Images Taken Philips Webcam

Saturn is the most challenging and, arguably, the most rewarding target for the webcam imager. The biggest problem posed by the ringed planet is simply its low surface brightness. Saturn's globe is 16 times fainter than the globe of Mars and a third as bright as Jupiter. With the maximum available AVI video exposure being 1 5th of a second (5 frames per second at, confusingly, the 1 25th setting on the Philips driver settings) and 1 10th being more desirable (to freeze the seeing) the raw...

Accumulated Optical Problems

Spherical Aberration Central Obstruction

What you have been shown thus far is how the individual aberrations and transmission variations can affect the image. More important, however, is the way minor problems add up. The wobbly stack of Fig. 3-1 shows how many errors accumulate as a collection of filters. Even if each filter is relatively unimportant, the total filtration could render the image fuzzy and indistinct. The concept of modulation transfer outlined in Chapter 3 presented a single standard around which we could rally. By...

The Lunar Roving Vehicle Wins The Mobility Debate

Moon Rover

As late as mid-1968, numerous contractors still held the view of using dual Saturn V launches to support extensive Apollo missions and their considerable hardware requirements. For example, in May 1968 GMDRL became AC-Electronics Defense Research Laboratories and published a presentation titled Roving Vehicles for Apollo Lunar Exploration Program. The presentation discussed the work the General Motors division had conducted and its relevant experience in the development of lunar surface...

Potential Field Source Surface PFSS Models

PFSS models are perhaps the most useful Sun-heliosphere connection models to date and have many applications (Arge et al., 2002 Luhmann et al., 2002 DeRosa and Schrijver, 2002). They use the potential field assumption mentioned above and hence decouple the coronal heating problem and the open-flux connection problem by making the inner corona exclusively magnetically dominated and time-independent. For a given choice of source surface radius, rs , the magnetic field potential then can be...

Combinations of Ducted Jet Engines and Rocket Engines

Rocket Engine Fuel Tank

The Tomahawk surface-to-surface missile uses two stages of propulsion in sequence. The solid propellant rocket booster lifts the missile away from its launch platform and is discarded after its operation. A small turbojet engine sustains the low level flight at nearly constant speed toward the target. A ducted rocket, sometimes called an air-augmented rocket, combines the principles of rocket and ramjet engines it gives higher performance specific impulse than a chemical rocket engine, while...

TEL10 Edgar O Smith Observatory

Razdow Telescope

The housing that shelters the telescope slides off on rails. Photo courtesy of Adeline Caulet. The newest general-purpose telescope on the mountain is the 1.2-meter Calypso telescope, which is clearly visible from the road to the summit, but difficult to spot from the top. It is located below the WIYN telescope, and the access road is marked Private. However, any visitor wishing to learn more about the telescope can leave a message for the resident astronomer at the front...

Example The YoYo Despin Mechanism

Both in orbit and during orbit insertion, spacecraft and upper stage vehicles are frequently provided with spin to ensure attitude stability. At other times it may be necessary to terminate the spin permanently or at least temporarily, for example, to reorient the vehicle prior to a propellant burn. Despinn-ing can be accomplished by firing small retro-rockets mounted on the vehicle such as to produce a torque counter to the direction of spin. Alternatively, despin can be obtained by initiating...

Gas Scintillation Proportional Counters

Gas Proportional Scintillation Counter

Gas scintillation proportional counters (GSPC), developed in 1972 20 , offer the advantage of an enhanced energy resolution when compared with proportional counters. In conventional proportional counters, the charge generated by an ionizing event is multiplied in a high electrical field. The amplification grows exponentially with the number of ionizing collisions of an electron in the high field region. Only 14 ionizing collisions result in a charge multiplication of four orders of magnitude....

C72 Histogram Shaping

The previous tool, Brightness Scaling, operates on an image by examining the range of pixels in it and assigning new pixel values based on where each lies in the range between the values selected for black and white. Histogram Shaping, while looking superficially similar, works in an entirely different way. While both tools reassign each pixel value in the original image to a new value, Histogram Shaping does it by trying to force the histogram of the image, as a whole, to a new shape. While we...

Morphological Operators

Isophotes Photoshop

Morphology deals with form and shape in image processing, morphological operators are tools that aid the observer in defining, extracting, and manipulating the Figure 15.9 Isophote contour lines encircle a region having pixel values greater than the isophote pixel value. This highly enlarged section of the M101 image shows a knot in the spiral arm, an isophote contour line drawn around that knot, and the same isophote line superimposed on the image. Figure 15.9 Isophote contour lines encircle a...

Juvat ire jugis qua nulla priorum Castaliam molli devertitur orbita clivo

The lines are from Virgil, and freely translated read as follows Joyous it is to cross mountain ridges where there are no wheels ruts of earlier comers, and follow the gentle slope to Castalia. Niepce-Daguerre and Talbot had indeed walked along roads where no wheels before had gone, using entirely different methods. To Talbot belongs the distinction of being the first person to publish a workable photographic system which could be adopted worldwide. One of Talbot's early photographs is...

B31 Astrometry Books and Articles

Guide to Minor Body Astrometry, Internet article at Description of how to carry out measurements and report observations of asteroids This guide is intended for those observers interested in undertaking an astrometric CCD-observing program of minor planets and or comets. Everhart, Edgar. Constructing a Measuring Engine. Sky and Telescope September 1982 279. Describes building a two-axis precision engine for measuring positions from photographs great insight into state of the art of amateur astrometry before CCDs. Konig, A. Astrometry with Astrographs. In Astronomical Techniques. Ed. W.A. Hiltner. Chicago University of Chicago Press, 1962. Quite possibly the clearest exposition of astrometry available appears in a short chapter of an impeccable source book on astronomy. March , Jordan D., II. Measuring Positions on a Photograph. Sky and Telescope July 1990 71. Instructions for doing astrometry from photographic prints includes program in line-numbered Basic for reducing x, y data using...

Observing Project 8C Looking for Deimos and Phobos

Mars' two tiny moons, Deimos and Phobos, circle the planet with blistering speed and never stay very far from it. When Phobos is at its greatest elongation from Mars, it is never more than three planetary radii from the planet. Since the moon circles Mars in just over seven hours, the window of opportunity to see it while it is away from the planet is only about an hour long. It is critically important therefore to know when the moon is at that point of greatest elongation and have a plan. Use...

History of Double Star Observation

In 1610 the invention of the telescope by Galileo gradually led to the discovery of telescopic double stars but these were noted merely by the way. In 1617 Castelli found that Mizar was itself double4 and he later added a few more pairs. In 1664 Robert Hooke was observing the comet discovered by Hevelius when he came across Y Arietis, a pair of pure-white stars of 4th magnitude separated by some 8''. Over the next hundred years or so a few more double stars were noted but not catalogued in any...