Surviving Orbit the DIY Way by Sandy Antunes


6756d91791487ab.png Author Sandy Antunes
Isbn 9781449310622
File size 41 Mb
Year 2012
Pages 92
Language English
File format PDF
Category hobbies



 

Download from Wow! eBook Surviving Orbit the DIY Way Sandy Antunes Surviving Orbit the DIY Way by Sandy Antunes Copyright © 2012 Sandy Antunes. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: 800-998-9938 or corpo [email protected] Editor: Brian Jepson Production Editor: Melanie Yarbrough Cover Designer: Karen Montgomery Interior Designer: David Futato Illustrator: Rebecca Demarest August 2012: First Edition Revision History for the First Edition: 2012-08-23 First release See http://oreilly.com/catalog/errata.csp?isbn=9781449310622 for release details. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Surviving Orbit the DIY Way and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc., was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. ISBN: 978-1-449-31062-2 [LSI] Contents Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v 1/Life as a Satellite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Space Is…. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Launch Trouble. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 How High Is Space?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2/The Measure of Space. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Outgassing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Orbital Thermal Profiles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Magnetic Fields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Orbital Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Orbital Debris. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3/Space Radiation Environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Space Weather Events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Shielding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 History of Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Electronics Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4/Testing Formalism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 NASA CubeSat Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Sample Test Schedule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Solving Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Test Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Formal Risk Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5/Thermal Vacuum Chamber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Building and Using a Thermal Vacuum Chamber. . . . . . . . . . . . . . . . . . . . . . 38 The $100 Thermal Vacuum Chamber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Thermal/Vacuum Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 iii Heating Rates Due to Sunlight and Dark. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 6/Launch Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Vibration Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Vibration Spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Shaker Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Acoustic Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Drop Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Static Loading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 7/G-Force Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 G-Force Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Hand-Powered G-force Rig. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 The Drill-Powered G-force Rig. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 8/Good Test Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Flight Spares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Test Scheduling and Isolated Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Suggested Build-and-Test Schedule for a Typical Picosatellite. . . . . . . . . . . . 72 Defects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Frame Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Clean Rooms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 DIY Clean Room/Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 The Money Build. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 When to Commit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 iv Contents Preface Just how harsh is the space environment into which you thrust your DIY satellite? We look at what conditions your satellite must endure, how to test your satellite, and what launch, ground and orbit support you will need. In addition, we provide tips on making your overall plan and schedule, including the most important tests that will help your satellite survive and thrive in space. Chapter 1 gives you a quick primer on what space and Low Earth Orbit (LEO) actually is, while Chapter 2 goes deeper with actual numbers that describe the conditions your satellite will be facing in space. Having set the scope of what space conditions are, Chapter 3 goes into more into detail about the radiation environment you’ll be facing in the ionosphere and how to mitigate its risks. Chapter 4 provides you with a discussion of what testing is all about as well as offering some sample NASA CubeSat requirements and a smidgen of formal systems engineering. In Chapter 5, we get into building a thermal vacuum chamber for mimicking the space environment. Chapter 6 walks you through building and running a vibration shake test to mimic the difficulties of your anticipated rocket launch. Chapter 7 guides you through high G-force testing of your payload using a homebuilt centrifuge. Chapter 8 closes the book with a discussion on the usefulness of flight spares, guidelines on scheduling your tests, and help in choosing appropriate clean room or lab in which to test. In summary, the book tells you where your satellite is heading, what to test, and how and where to test it. We hope this book also serves you as a basic text on the Low Earth Orbit environment in general, so that you can design, build and test a spaceworthy picocraft. By the end of this book, you will be ready to prove your picosatellite has the right stuff to deploy via a fiery rocket launch into the harsh vacuum of space. We also recommend the other books in this series: our primer on designing and building your craft in DIY Satellite Platforms, crafting your mission’s science and technical goals in DIY Instruments for Amateur Space, and commanding, operating and downloading data from your satellite in DIY Data Communications for Amateur Spacecraft. But first, let’s really test the limits of the picosatellite you’ve built. v Conventions Used in This Book The following typographical conventions are used in this book: Italic Indicates new terms, URLs, email addresses, filenames, and file pass: [extensions]. Constant width Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords. Constant width bold Shows commands or other text that should be typed literally by the user. Constant width italic Shows text that should be replaced with user-supplied values or by values determined by context. This icon signifies a tip, suggestion, or general note. This icon indicates a warning or caution. Using Code Examples This book is here to help you get your job done. In general, you may use the code in this book in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission. We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Surviving Orbit the DIY Way by Sandy Antunes (O’Reilly). Copyright 2012 Sandy Antunes, 978-1-4493-1062-2.” vi Preface If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [email protected] Safari® Books Online Safari Books Online (www.safaribooksonline.com) is an on-demand digital library that delivers expert content in both book and video form from the world’s leading authors in technology and business. Technology professionals, software developers, web designers, and business and creative professionals use Safari Books Online as their primary resource for research, problem solving, learning, and certification training. Safari Books Online offers a range of product mixes and pricing programs for organizations, government agencies, and individuals. Subscribers have access to thousands of books, training videos, and prepublication manuscripts in one fully searchable database from publishers like O’Reilly Media, Prentice Hall Professional, Addison-Wesley Professional, Microsoft Press, Sams, Que, Peachpit Press, Focal Press, Cisco Press, John Wiley & Sons, Syngress, Morgan Kaufmann, IBM Redbooks, Packt, Adobe Press, FT Press, Apress, Manning, New Riders, McGraw-Hill, Jones & Bartlett, Course Technology, and dozens more. For more information about Safari Books Online, please visit us online. How to Contact Us Please address comments and questions concerning this book to the publisher: O’Reilly Media, Inc. 1005 Gravenstein Highway North Sebastopol, CA 95472 800-998-9938 (in the United States or Canada) 707-829-0515 (international or local) 707-829-0104 (fax) We have a web page for this book, where we list errata, examples, and any additional information. You can access this page at: We have a web page for this book, where we list errata, examples, and any additional information. You can access this page at http://oreil.ly/ surviving_orbit_DIY. To comment or ask technical questions about this book, send email to book [email protected] Preface vii For more information about our books, courses, conferences, and news, see our website at http://www.oreilly.com. Find us on Facebook: http://facebook.com/oreilly Follow us on Twitter: http://twitter.com/oreillymedia Watch us on YouTube: http://www.youtube.com/oreillymedia viii Preface Download from Wow! eBook 1/Life as a Satellite …we’ve got to go out to Asteroid HS-5388 and turn it into Space Station E-M3. She has no atmosphere at all, and only about two per cent Earthsurface gravity. We’ve got to play human fly on her for at least six months, no girls to date, no television, no recreation that you don’t devise yourselves, and hard work every day. You’ll get space sick, and so homesick you can taste it, and agoraphobia. If you aren’t careful you’ll get ray-burnt. Your stomach will act up, and you’ll wish to God you’d never enrolled. But if you behave yourself, and listen to the advice of the old spacemen, you’ll come out of it strong and healthy, with a little credit stored up in the bank, and a lot of knowledge and experience that you wouldn’t get in forty years on Earth. — ROBERT HEINLEIN "Misfit" What’s it like up there? Every 90 minutes, your satellite orbits the Earth. Each orbit passes high over a different geographic coordinate. The atmosphere you encounter is negligible, a residue of trace oxygen and other atoms with no real pressure to sustain you, just enough pressure to cause drag and (in months or years) reduce your orbit and cause reentry. The Sun bathes you in heat and ultraviolet (UV) and X-rays and all the other wavelengths of light. When in sunlight, your satellite heats up, perhaps uncontrollably. For half of each orbit, the Earth blocks the Sun and your satellite radiates out into that cold 3-degrees above absolute zero ambient temperature of space. High energy particles (protons and electrons) stream from the Sun and interact with the Earth’s magnetic field, creating beautiful aurora and potentially frying your electronics (see Figure 1-1). Very rarely, you might encounter space dust or tiny bits of orbital debris. 1 Figure 1-1. Space is beautiful, hostile, and survivable. Image of an aurora from the space shuttle, courtesy of NASA. All this assumes you survived the rocket launch. Space is a harsh and unforgiving environment. It is harsh because it has no pressure or outside forces to provide structure, just vacuum. There is no air or liquid to conduct heat or buffer temperatures. It is filled with electromagnetic and particle radiation. Worse, if something breaks, you can’t pop over to fix it. You get one shot and have to make that one shot work. Fortunately, through testing, you can practice your shots before the real event. Space Is… Space: • is airless • yet has atmospheric drag • is hot and cold • is insulating • has electric and magnetic fields (as well as field hot spots like the South Atlantic Anomaly, where the Van Allen belts dip close to Earth) • is influenced by solar weather • lets the spacecraft jitter in attitude, bounce, and overall momentum • requires orbital maneuvering rather than line-of-sight travel Space is the highest of the three final frontiers (see “Frontiers” (page 3)). It is an airless, inhospitable place where your three biggest problems are a lack 2 Surviving Orbit the DIY Way of air, extremes of hot and cold, and a surplus of electromagnetic energy. It also takes an enormous amount of fuel to get up there. To succeed in space, you must be lightweight, pack small, and be tough. This book tells you how to test whether your satellite will survive low earth orbit (LEO). The air pressure in LEO is effectively nil. There’s just enough air to provide atmospheric drag to de-orbit your satellite, but not nearly enough air to provide any structural or navigational assistance. In space, there is no thermal blanket of air or water to help you retain or dissipate heat. Therefore, when the sun shines, you heat up—rapidly. When you are in darkness, you cool through radiative heat, and can keep cooling (in theory) until you reach 3K, or about -270 C or -454 F (for this work we’ll be using Celsius). To this environment, we add a fourth challenge—the rumbles required to get there. A rocket launch will apply intense g-forces, where acceleration of the rocket presses your payload as if it were feeling strong gravity. The rocket will vibrate and shake at different rates as it goes through different stages. Finally you get a thump as your satellite is ejected from the final stage. Here is where your satellite may drop a few inches very quickly. In any part of this, there may be mechanical mishaps as well. Frontiers The frontiers of space, the deep oceans, and the mind compete for the title of final frontier, but space got the official nod from Star Trek. "Space, the final frontier" is an extremely famous line from the opening of the original "Star Trek". The brain is often called "the final frontier of science", and ocean documentaries often dub the deep sea "our final frontier" or, in a bit of oneupmanship from the magazine COSMOS, "the real final frontier". In a humorous twist, death gets called "the undiscovered country" by Shakespeare, then re-appropriated by Star Trek as peace being the undiscovered country. In this context, we could call DIY Space the first, best hope for exploring one of the final frontiers. Hopefully peacefully, or at least with as little death as possible. Launch Trouble Looking at what can go wrong with a rocket launch, we’re hard put to find something that can’t go awry. Here’s a short list of just some of the things that can go wrong during launch and early orbit checkout. You might have a launch vehicle problem and get into an improper orbit. Or, the forces of launch can damage your satellite from acoustics, g-forces, vibration, changes in atmospheric pressure, temperature changes, or outgassing. You may reach orbit but not have the right facing or spacecraft attitude (not an Life as a Satellite 3 emotion, just means facing and orientation), making it difficult to communicate or misaligning your solar panels to the sun so you can’t get power. Your satellite may underperform or overperform. You may miss detecting timecritical anomalies (satellite bits that go wrong) or situations (events that go wrong). Your team can make a hasty or incorrect decision. Your operating procedures may be incorrect. Your hardware or software may have bugs. (Thanks to Squibb, Boden and Larson, Cost-Effective Space Mission Operations, 2nd edition, pg 304, for this list.) If all this sounds pessimistic, remember this is the book on testing. Your plan is to perform reasonable tests to mimic the conditions the satellite will face when you deploy for real. Good testing reduces risk, though you can never eliminate it. In fact, you need to be sure you don’t get overzealous with your testing and actually break something for no other reason than testing it. For example, if you want to test whether your car door is closing properly, you may want to slam it closed two or three times. But slamming it fifty times won’t give you more information—and may break something that was working perfectly. So our mantra is to devise a thorough test plan, carry it out in a reasonable fashion, analyze your test data, then stop. Each of those four steps is important. How High Is Space? How high is space, how far can you fall with a parachute, where do Low Earth Orbit (LEO) satellites reside, and where does the hard radiation from the sun get nasty? Gathered for the first time in one place is our High Altitude Explorer’s Guide (Figure 1-2). A typical airplane cruises at 9 km (6 miles) up, around 30,000 feet. Military jets (from the SR-71 onward to modern planes) can hit over 30 km (19 miles) up, over 100,000 feet. You can parachute from that height. In 1960, Joseph Kittinger set the record at 31.3 km (19.5 miles), or 102,800 feet. Felix Baumgartner is planning to use a rocket to freefall from 36 km (over 22 miles)— an 118,000 feet fall—some time before 2015. But those aren’t space (Chapter 2). In the US, “space” begins at 80.4 km (50 miles), or 264,000 feet. General international consensus sets a similar limit for the start of space as 100 km (62 miles), or 380,000 feet. “Low Earth Orbit” (LEO), where many satellites live, goes from 160 km (100 miles, 525,000 feet) to 2,000 km (1,240 miles, 6.5 million feet). My own Project Calliope picosatellite will be 230 km up (143 miles, 755,000 feet). The International Space Station (ISS) cruises higher up, from 278 km (173 miles, 912,000 feet) to 460 km (286 miles, 1.5 million feet). 4 Surviving Orbit the DIY Way Figure 1-2. Layers of the Earth’s atmosphere (courtesy NASA/MSFC) Starting above the space limit but a bit before LEO, the inner Van Allen Belts, which magnetically shield the Earth’s surface from high energy particles, extend from 100 km (62 miles, 33,000 feet) up to 10,000 km (6,200 miles, 3.3 million feet). Finally, geostationary orbits are at 35,786 km (22,236 miles, 117.5 million feet). These geosynchronous orbits, lined up above the Earth’s equator, have an orbital period equal to one day, so they hover over the same spot of the Earth. Together, that’s “space”, with an emphasis in this book on LEO. We’ll walk through several bits of homemade gear to tackle these tests. For a vacuum test, you can make a simple chamber using a pressure cooker and an automotive brake vacuum pump. For thermal vacuum, you need to add an IR heat Life as a Satellite 5 source. For vibration and shake testing, you can modify power tools to do simple test scenarios. G-forces can be tested primitively using the centrifugal force provided by you swinging a rope, or with more technical elan using a power drill and a long pair of swing arms. As for the drop test, that’s both the simplest and most nerve-wracking, as you simply have to be willing to drop your work. But first, a deeper look at space. Let’s look at the hard numbers for where we’ll be sending our picosatellite. 6 Surviving Orbit the DIY Way 2/The Measure of Space By the numbers, we’re 1.496 x 108 km from the Sun, aka 1 Astronomical Unit (AU). It takes about 8 minutes for light or any kind of radiation from the Sun to reach the Earth. Some events—like plasma thrown off from the Sun —can take 1-4 days to reach us. The sun throws out light (radio through gamma) as well as energetic electrons and protons, and big wind-like streams of hot hydrogen gas (solar plasma), as shown in Figure 2-1. Figure 2-1. Yokkoh image of the Sun in UV showing its active nature (courtesy JAXA) 7 While Earth’s atmosphere is mostly nitrogen, up at Low Earth Orbit (LEO) has almost no atmosphere at all. We get the worst of both really—no air to use for breathing, but just enough molecules of air to cumulatively cause drag and eventually make our LEO satellites de-orbit. Our atmosphere blocks most of the harder radiation the Sun puts out— X-rays and UV (especially, for UV, the Ozone Layer). By definition what we see on Earth is visible light, plus a little light UV and a fair amount of invisible radio emission. All that blocked stuff is visible from orbit, however. In fact, that’s why we launch satellite telescopes—less atmosphere to block any kind of light. Note some plastics (polymers) are sensitive to UV—they break down in the presence of UV. Fine on Earth, but terrible for space-going hardware. ESA maintains a large list of materials and their responses to the space environment in their ESA materials database at http://esmat.esa.int/. In general, if it’s a material that has a strong smell or that oxidizes (rusts) easily, it’s a poor choice for space. At sea level, our atmosphere has a pressure of 1 x 105 Pascals (Pa), with a density of 1.225 kg/m3 (and 1024 molecules/m3, if you like counting molecules), assuming a moderate reference temperature temperature of 288 K (15 C). The US Standard Atmosphere model (Figure 2-2) illustrates the temperature, density and pressure variation as you increase in altitude. By 86 km up (which is where the US Standard Atmosphere model stops calculating), you are facing (at 187 K/14 C) pressure of 0.3 Pa (3x10-5 atmospheres) and only 0.000006 kg/m3 of air mass. At that height, you’re still not officially in space and would not count as an astronaut if you flew there. Space is typically defined as 100 km up and higher. Putting these together in comparison, 99.9% of the Earth’s atmosphere is in the layers below 50 km, while only 0.1% of the atmosphere in the 50 km to 400 km range. For LEO, in the range of 300-900 km, the atmosphere is thin (low density) but not zero. LEO is in the part of the atmosphere called the Thermosphere, and the Thermosphere contains the region called the Ionosphere. The Ionosphere is where auroras occur. By 400 km up, you have about 1014 molecules per cubic meter (10-10 kg/m3), with an equivalent pressure of, for all practical purposes, nil (10-5 Pa and lower). Pressure is hard to define in the ionosphere, since pressure is a measure of air molecules impacting a given object, and there just aren’t many molecules at that height. Put another way, any individual molecule will typically travel 1 km or so before colliding with another molecule. The ionosphere’s density also varies with solar activity and whether you are in sunlight or dark. As you will often read in this book, LEO is a vacuum in terms of harsh unsurvivability, with just enough gas molecules to cause oxidation and drag in the 8 Surviving Orbit the DIY Way Figure 2-2. US Standard Atmosphere (courtesy Wikimedia) long term. It’s the worst of both worlds: no air to use, just enough to eventually force reentry. Most of that is oxygen, which means you have oxidation (corrosion) to worry about. Atomic oxygen is the major component of the residual LEO atmosphere (Figure 2-3). By the time you reach geosynchronous height, 36,000 km up, the density is 10-20 kg/m3 and the pressure is 10 -15 Pa, and it pretty much stays at that low density as you travel within the solar system. You heat up due to absorbing solar radiation (1371+- 5 W/m2 or so, ref) as well as sunlight reflected off the Earth (Earth’s albedo) plus Earth black-body emission, totaling perhaps 200 W/m2. While the solar wind is at 2 x 105 K, it is so thin it provides no real heating. The ionosphere by definition is where ionization of plasma occurs, and is the region above 86 km. The incoming solar radiation (called incident solar UV, a fancy term for the sun’s ultraviolet light) disassociates the atmosphere into its individual elements, then disassociates the electrons from the nuclei. Its peak density is in the 300-400 km range, though the density of the plasma is still less than the density of the neutral molecules; both co-exist. The Measure of Space 9 Download from Wow! eBook Figure 2-3. What elements exist at different altitudes (courtesy NASA) Outgassing Back to the lack of air. Every get something wrapped in plastic and it smells all plastic-y? You’re sniffing some plastic molecules that outgassed from the wrapping material. Outgassing (also called sublimation) is the vaporization of a solid going to a gas state due to low pressure. At the typical 10-11 to 10-15 Pa of LEO, many materials stable in an Earth lab will outgas. Heating increases outgassing. Outgassing has two problems; it erodes the material that is outgassing, true —but more crucial, the outgassed material may condense on—and thus coat —other surfaces. This can change their conductance or, for optics and detectors, coat them so they no longer can see. For this reason, do not put lubricants into space. Ground-based lubricants have a high vapor pressure and outgas quickly. They therefore are terrible as lubricants, since they evaporate off your moving parts, and terrible as a contaminant, since they’ll coat random surfaces. 10 Surviving Orbit the DIY Way

Author Sandy Antunes Isbn 9781449310622 File size 41 Mb Year 2012 Pages 92 Language English File format PDF Category Hobbies Book Description: FacebookTwitterGoogle+TumblrDiggMySpaceShare Is your picosatellite ready for launch? Can it withstand rocket thrusts and the vacuum of space? This do-it-yourself guide helps you conduct a series of hands-on tests designed to check your satellite’s readiness. Learn precisely what the craft and its electronic components must endure if they’re to function properly in Low Earth Orbit. The perfect follow-up to DIY Satellite Platforms (our primer for designing and building a picosatellite), this book also provides an overview of what space is like and how orbits work, enabling you to set up the launch and orbit support you’ll need. Go deep into the numbers that describe conditions your satellite will face Learn how to mitigate the risks of radiation in the ionosphere Pick up enough formal systems engineering to understand what the tests are all about Build a thermal vacuum chamber for mimicking environment of space Simulate the rocket launch by building and running a vibration shake test Use a homebuilt centrifuge to conduct high G-force tests Get guidelines on scheduling tests and choosing an appropriate lab or clean room     Download (41 Mb) DIY Instruments for Amateur Space HomeSkills: Carpentry: An Introduction to Sawing, Drilling, Shaping & Joining Wood Make: Tech DIY: Easy Electronics Projects for Parents and Kids Fashioning Technology: A DIY Intro to Smart Crafting The Rocket Mass Heater Builder’s Guide Load more posts

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