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Archive for the Book Reviews category

December 20, 2010

How Easy is it to Measure the Universe?

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Credits: NASA/ESA/A.Zezas/JPL/Caltech/GALEX Team/J.Huchra et al.

 

One thing that I find fascinating about astronomy is the ingenious ways astronomers have come up with to solve the puzzles laid out in the skies. You cannot travel to distant stars and galaxies to study them… so what do you do? Well, you use all of the knowledge that mathematics and physics give you and find out anything you want to know (or pretty much everything) about them.

 

Eratosthenes (276-194 BC) was the chief librarian of the Library of Alexandria (the same library that Julius Caesar burned to the ground in 48 BC). He knew that every year on June 21 at noon the Sun was 7.2 degrees off the vertical in Alexandria, while in Syene the Sun stood directly overhead. Knowing the distance between the two locations and using basic geometry, he was able to determine the circumference of the Earth to be around 40,000 km. Pretty amazing for that time, don’t you think?

 

Closer to our time, the astronomer Edwin Hubble (1889-1953) has devised methods for finding distances to other galaxies. Hubble was also able to measure the radial velocities of galaxies using the redshift in their spectral lines. His findings proved not just that the Universe is expanding, but also determined that it all began about 13.7 billion years ago.

 

Have you ever been able to visualize in terms of relative size or scale the planets and the moons of our solar system? How big do you think the Earth is compared to Mercury or Mars? Which one do you think is a bigger moon, the Earth’s Moon or Saturn’s Titan? How many times do you think the Grand Canyon would fit inside the Valles Marineris on Mars? How big is, let us say, the asteroid Itokawa compared to the International Space Station? Is our own Milky Way galaxy bigger than Andromeda?

 

I found many other interesting stories and had the above questions answered in a new book, Sizing Up The Universe. I would say that the unifying theme of the book is size comparison. Numerous charts capture a fresh vision of the Universe, introducing an original way of comparing objects in the heavens.

 

 

Browsing through Sizing Up The Universe, I could not help thinking about my high school astronomy textbook. The author of the textbook was definitely not into visual arts, as the pages were flooded with math formulas and only a few sketches were present here and there. I did not mind it at that time, but I realize now that stunning images of planets, stars, and galaxies, such as those found in Sizing Up The Universe, would make the learning process much more enjoyable. Moreover, the real stories behind groundbreaking discoveries in astronomy that are sprinkled throughout the text make it captivating and easy to read.

 

The authors of Sizing Up The Universe are J. Richard Gott III and Robert J. Vanderbei. J. Richard Gott III is professor of astrophysics at Princeton University. He has written articles for Time, Scientific American, and New Scientist. He is also the author of Time Travel in Einstein’s Universe. Robert J. Vanderbei is professor and chair of the Department of Operations Research and Financial Engineering at Princeton University. He is an amateur astronomer and has taken from his own backyard many images of astronomical objects, some of which can be found in the book.

 

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September 7, 2010

How Tough is Life in LEO?

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Credits: NASA

 

In a nutshell, it is really tough! The higher you go, more bad things can happen to you… the increasingly rarefied air, freezing temperatures, ionized atoms, radiation, and space debris make life challenging. So, besides thinking of how to place spacecraft in orbit, engineers must consider all of the factors mentioned above (and much more) when designing a spacecraft.

 

 

The space environment (the vacuum, the radiation, the space debris, etc.) definitely poses big challenges to spacecraft design engineers. From 1971 to 1989, more than 2,700 spacecraft anomalies related to interactions with the space environment were recorded. These interactions with the space environment are called space environment effects and the changes in the space environment define what is called the space weather. Believe it or not, there are dedicated programs aimed at developing the ability to predict these changes in the same way the weather forecasting does for terrestrial weather. The Space Weather program was formed in the mid-1990s by the National Science Foundation (NSF). The Europeans developed a similar program under the umbrella of the European Space Agency (ESA).

 

The space environment effects can be grouped into several categories. Such categories include: vacuum, neutral, plasma, radiation, and micrometeorid/orbital debris. So, basically, we can discuss the effects of the vacuum environment, the neutral environment, etc. Each one of these environments interact with the subsystems that comprise a spacecraft: the propulsion system that provides the means of maintaining a certain orbit or attitude, the electrical power system that provides power to the rest of the subsystems onboard, the thermal control system, the attitude and orbital determination and control system, etc.

 

The vacuum environment imposes challenges when it comes to designing the structure, choosing the materials, and defining a strategy for thermal control. The pressure differential between the inside and the outside of a manned spacecraft is tremendous (around 350 km above the surface of the Earth, the pressure is ten orders of magnitude less). The lack of atmosphere translates into the fact that the spacecraft will have to deal with solar ultraviolet (UV) radiation (the UV radiation is energetic enough to degrade material properties). Also, the spacecraft can only cool itself by conduction or radiation.

 

Credits: NASA

 

Even if very rarefied, the neutral atmosphere in low Earth orbit is dense enough to cause a significant atmospheric drag force. The atoms can physically sputter material from surfaces and even cause erosion. All these mechanical and chemical interactions depend on the atmospheric density.

 

In low Earth orbit, the solar UV radiation ionizes the oxygen and nitrogen atoms. This environment, known as the plasma environment, can give rise to very interesting effects, like spacecraft charging and arcing between regions of differing potentials.

 

 

By far, the most dangerous environment in Earth orbit is the radiation environment. In the regions of charged particles, known as trapped radiation belts, particles with energy levels in the order of MeV pass through the surface layer and interact with the materials inside the spacecraft. Present shielding technology cannot protect living organisms inside a spacecraft in these regions.

 

Micrometeoroids and orbital debris are a cause of great concern to spacecraft design engineers and spacecraft operators as the kinetic energies associated with impacts at orbital velocities are very high. The main effect on spacecraft in this case is the physical damage upon impact. Other effects include surface erosion, ejecta resulted from impacts, changes in thermal control properties, and generation of electro-magnetic impulses (EMIs).

 

As most of the characteristics of the space environment were determined by remote observations or during short duration missions, one long duration mission was necessary to verify and validate these measurements.

 

In April 1984, the Space Shuttle Challenger placed into low Earth orbit (LEO) a spacecraft carrying a number of experiments for the purpose of characterizing the low Earth orbit environment. The spacecraft (known as the Long Duration Exposure Facility, or LDEF for short) was a twelve-sided cylindrical structure three-axis stabilized in order to ensure an accurate environmental exposure. The spacecraft was supposed to spend one year in orbit, but just before the planned retrieval, the Space Shuttle fleet was grounded as a result of the Challenger accident on January 28, 1986.

 

The spacecraft was returned to Earth by the Space Shuttle Columbia in January 1990. After almost six years in low Earth orbit, the results of the experiments onboard the facility contributed a great deal to the understanding of interactions between artificial objects and the environment in low Earth orbit.

 

You can find all the above in much more detail in Alan Tribble’s book The Space Environment – Implications for Spacecraft Design. Alan Tribble presents an excellent account of the effects the space environment can have on operational spacecraft. The book offers a unique perspective, as it combines the study of the space environment with spacecraft design engineering. .

 

Alan Tribble spent over ten years designing spacecraft. He is a technical project manager in the International Software Defined Radios group for Rockwell Collins.

 

 

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November 13, 2009

Programming Robot Controllers

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In a world dominated by personal computers, there is room left for applications running on microcontrollers. Beginning with home appliances and ending with robotic manipulators used in space missions, microcontrollers are still the optimal choice of many system designers. It seems that in computer-land you do not have to be big, strong, and/or fast in order to be smart… there are even examples of Kalman filter implementations running on microcontrollers.

 

 

Today I recommend you a book on programming microcontrollers – Programming Robot Controllers. The book focuses on using microcontrollers for robot control and has the declared goal to provide robot designers with the knowledge and the tools that will help guarantee that his/her robot will perform to expectation and specification and can be easily modified.

 

Myke Predko, the author, uses the Microchip PICmicro PIC16F627 chip for the example circuits presented in the book. Despite the modest performances of the microcontroller (PIC16F627 is a 18-pin device, providing 1K instruction space and 68 bytes of variable memory, two 8-bit timers, a 16-bit timer, serial communications, and a single-vector interrupt capability), it is very popular for robot applications. Assembly language enthusiasts might be a little bit disappointed because the code examples in the book are written in C. But there is an advantage to that… if you want to port the robot code, the compiler will do most of the work for you.

 

The author introduces three different spectrums in describing how software is written for robots. Depending on the requirements for the code response/execution speed, the code can be biologic, mechalogic, and elelogic. Don’t bother to look up the last two in the dictionary… they are new terms. In a nutshell, the biologic code makes the high-level decisions providing the high-level intelligence demonstrated by the robot, the mechalogic code controls the mechanical devices built into the robot, and the elelogic code provides intercomputer communications and some interface and output functions.

 

After an introduction focused on the specifics of software development for microcontrollers and a detailed description of the microcontroller itself, the book presents devices that are external to the microcontroller and how they can be integrated into a general robot architecture: RS-232 interfaces, LEDs, LCDs, IR sensors, sound sensors, motor controllers, odometers, and radio control servos. The author points out that it is easy to build a robot, but it is much more difficult to get it to work properly or as expected. The conclusion is that designing the robot system is an important step of the process.

 

If you plan to build your own exploration rover, design a micro-satellite bus, or put together a robot manipulator, Programming Robot Controllers is a good book to start with.

 

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September 28, 2009

Fly Me to the Moon

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In Fly Me to the Moon : An insider’s guide to the new science of space travel, Ed Belbruno explains in simple terms advanced mathematical techniques using a general subject called dynamical systems theory. He describes how we can use chaos to change the way we maneuver in space.

 

Ed Belbruno makes the important point that chaos can be used as a way to get a handle on the unpredictability in sensitive motions of a spacecraft.

 

 

The unpredictability results from the subtle combination of gravitational pulls and tugs on a spacecraft moving in space. An immediate application is low-energy transfer trajectories to lunar orbits.

 

Belbruno tells the stories of Hiten, the Japanese lunar mission rescued in 1991; HGS-1, a commercial Earth orbiting satellite that had strayed into an undesired orbit; LGAS, a low-budget NASA mission; and SMART-1, the ESA mission that tested low-energy lunar transfers in 2003.

 

The low-energy trajectories can be used for purposes other than sending automated cargo spacecrafts to permanent settlements on the Moon. Ballistic captures, as they are also called, could be used for a robotic mission in the Jovian system, to shed light on the apparently unpredictable trajectories of comets and other Kuiper Belt objects, and to explain the origin of our Moon or the Panspermia hypothesis.

 

While it is written for a non-technical audience, the book is grounded in solid theoretical research, and would be of interest to engineers and space enthusiasts alike.

 

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June 4, 2009

Imaging Space And Time With Hubble

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Credits: NASA/ESA

 

The Hubble Space Telescope (HST) is a joint creation of NASA, ESA, hundreds of industrial companies, government and university groups, and thousands of engineers and scientists. Since April 1990, when it was released into orbit from Discovery’s payload bay, Hubble has returned scientific data and stunning images of stars, nebulae, and distant galaxies.

 

The construction of the space telescope began in the 1980s, when the optics company Perkin-Elmer initiated the work on Hubble’s primary light-collecting mirror. The Hubble Space Telescope was completed in 1985, but was not deployed in Earth’s orbit for another five years.

 

In 1983, the Space Telescope Science Institute (STScI) was founded and it assumed from NASA the science management of the Hubble Space Telescope. STScI is located at Johns Hopkins University.

 

In its initial configuration, Hubble carried the Wide Field and Planetary Camera (WF/PC), the Goddard High Resolution Spectrograph (GHRS), the Faint Object Camera (FOC), and the Faint Object Spectrograph (FOS). It was soon to be discovered that the primary mirror had a flaw, and that the space telescope suffered from blurry vision.

 

 

The Hubble Servicing Mission 1 installed a corrective optics package, COSTAR, and replaced the original WF/PC with the Wide Field and Planetary Camera 2. Hubble Servicing Mission 2 replaced the GHRS and FOS with the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Servicing Mission 3A replaced all six gyroscopes, a Fine Guidance Sensor, and the onboard computer. Servicing Mission 3B saw the installation of the Advanced Camera for Surveys (ACS), which replaced the FOC, and the revival of NICMOS through the installation of a new cooling system.

 

 

All this, and the history of astronomic discoveries beginning with Galileo Galilei in 1609 and continued by William Herschel, William Huggins, George Ellery Hale, and Edwin Hubble, are presented in Hubble – Imaging Space And Time, a book authored by David DeVorkin and Robert W. Smith. The book is replete with spectacular images captured by the Hubble Space Telescope. Images of Carina Nebula, Eagle Nebula, Orion Nebula, and Swan Nebula, just to name a few, are a celebration of color and convey the majestic beauty of the Cosmos.

 

 

David DeVorkin is curator of the history of astronomy and the space sciences at the National Air and Space Museum, Smithsonian Institution. Among other books he has authored are Beyond Earth: Mapping the Universe and The Hubble Space Telescope: Imaging the Universe.

 

Robert W. Smith is a professor of history and Director of the Science, Technology and Society Program at the University of Alberta. He is also the author of The Space Telescope: A Study of NASA, Science, Technology and Politics, The Hubble Space Telescope: Imaging the Universe, and The Expanding Universe.

 

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September 8, 2008

The Space Elevator – from Fiction to Fact

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When I read The Fountains of Paradise a few years ago, I thought the space elevator was an interesting concept but that there was little chance of seeing it materialize like we saw the geostationary satellites become a reality after being depicted in a science fiction story by the same author, Arthur C. Clarke. And not just because some famous scientist said so, but because anchoring to the Earth a geostationary satellite with a cable measuring some 100,000 km is quite a technological challenge.

 

The first scientist to propose building a structure to reach space was Konstantin Tsiolkovski, who envisioned an orbital tower in 1895. In 1960, another Russian scientist, Yuri Artsutanov, developed this concept into an article called Into Space with the Help of an Electric Locomotive, which was published in Komsomolskaya Pravda. Artsutanov proposed linking of geosynchronous satellites to the ground using cables. It is interesting to mention here that Arthur C. Clarke and Yuri Artsutanov actually met years after the Fountains of Paradise was published.

 

Ok, so it is just science fiction, you might say. Well, not quite. There was a study ordered by NASA under the NASA Institute for Advanced Concepts (NIAC) program, which had as its object the investigation of all aspects of the construction and operation of a space elevator. The study was funded by NASA for more than two years and it was titled The Space Elevator.

 

A book was also published by the authors of the study, Bradley C. Edwards and Eric A. Westling. The book has the same title as the study. I found the book easy to read and really entertaining. Even if it becomes very technical in some parts, it is accessible to readers who do not have a technical background.

 

The book starts by presenting the main components of the design (the ribbon, the spacecraft, the climber, and the anchor), and the challenges that the space and the Earth’s atmosphere pose to the space elevator during the deployment phase and during the normal life of the program: lightings, meteors, and LEO objects, just to mention a few.

 

Being a feasibility study, the economic considerations had to be part of it. There are budget estimates that would draw the attention of potential investors, and even a realistic schedule for the development of not just one, but up to four ribbons.

 

While the space elevator is obviously a very cheap solution for deploying payloads in Earth’s orbit, it can also be used for opening Mars to human exploration and colonization. An Earth space elevator uploading materials in orbit working together with a space elevator downloading them on Mars would make possible the continuous flow of materials and colonists.

 

The later chapters of the book present the possible implications of the space elevator on the development of space travel and on the future of our technological society.

 

As the authors acknowledge, the book is not an exhaustive study of all aspects to be considered in the designing and building of the space elevator, but a good beginning. The proposed budget of 6 to 10 billion dollars for the project is not excessive considering the potential return of investment and that access to space is essential for the future development of our society.

 

Published in 2003, the book is a classic. I strongly recommend it.

 

In a follow up to The Space Elevator, Bradley C. Edwards and Philip Ragan wrote Leaving the Planet by Space Elevator, which was published in 2006.

 

For more information about the space elevator, including the 2008 Space Elevator Challenge and the Elevator: 2010 challenge, check out The Spaceward Foundation’s site.

 

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