text:
Talk:C++ Programming/Programming Languages

Slight inaccuracy
Perhaps I am being a little pedantic but C++ is considered a middle-level language (as is C) because of the low-level functionality that is accessible to both. This is almost implied in the existing statement: "C++ is beginning to be grouped with lower level languages like C" but I feel more clarity is perhaps needed?

64ByteKiller (discuss • contribs) 13:04, 8 August 2012 (UTC)

 * It depends, the notion about how high or low a language isn't exact at all, it is best used as an indication in comparisons that to attempt to cram the language in a slot, X is higher or lower than Y makes more sense than strictly defining X as a low, meddle or high level language especially since these concept are always in flux. Add to that imprecision the use of virtual machines and bytecode it can get even more complicated.
 * In a world that where a large number of population (not strictly profession programmers, think as the target reader of the book) is more comfortable with languages like python or C# type languages (I said comfortable in terms of access, familiarity), that even Java seems to old new. Stating that they are increasingly seeing C and C++ at the equal level of capability is correct, even technically, since the thing that makes C++ specifically distinct from C is the inclusion on the OSs of the runtime library. The practical distinctions are becoming also eroded, today you can even have objects in C. Yet I would feel better mixing ASM and C than C and C++ (if attempting to cram them in a slot). --Panic (discuss • contribs) 23:48, 8 August 2012 (UTC)


text:
Hiking in the Canadian Rockies

Many books have been written about hiking in the Canadian Rockies, particularly in Alberta and eastern British Columbia (technically the "Rocky Mountains" don't extend that far). This book is an attempt to organize and describe hikes in and around the Canadian Rockies, using other books only for specific and non-copyrighted information (i.e. Trail length, altitude, etc.) It will be primarily organised by area and then difficulty, so that one who wants to find one's self a hike one can do so with ease.

Quick Reference

 * 1) /Day Hikes/
 * 2) /Overnight Hikes/
 * 3) /Hike Index/
 * 4) /Bibliography/

How to use this book
This book is for anyone wanting to hike in the Canadian Rockies. Use the list below to sort first by day hike and overnight, then by area, then difficulty. I will eventually make an index of all the hikes. Also, all hikes i have done personally will be marked at the beginning of the description with a PD (personal description)

Please bear in mind that all hikes will doable without climbing equipment. Some scrambling may be required at certain times for the more advanced hikes.

Rating Hikes
Hikes will be rated in 4 major categories:
 * Beginner - the mildest of hikes
 * Intermediate - not particularly difficult, but more than a walk in the park.
 * Advanced - These are the most difficult of hikes that don't include mountains.
 * Mountain - These all involve conquering mountains, but because some are easier than others, they will be sub-rated Beginner, intermediate and advanced. NOTE: a beginner mountain is NOT a beginner hike. The easiest mountain is at the least an intermediate hike.

Before Hiking
If you are a new hiker, and are unsure of what to do or take along, read on. If you have experience in hiking, and are using this book only for new hikes, then you can ignore this section. (NOTE: this applies mostly to day hiking. for overnight hiking, be sure you have all the proper gear.)

Weather
Weather can make or break a hike. Be sure to check local weather forecasts, and pack accordingly. Even if there is the slightest chance of rain, you should bring along rain gear, especially if you're planning a longer hike. Don't climb mountains in a thunderstorm, and be sure that you can get in and out of where you are going, especially in winter. Also, be aware that the higher you go, the colder it gets, no matter the temperature

Clothing
Clothing usually depends on the weather (see above) but a few staple items are key:
 * Sturdy hiking boots - are recommended for all but the easiest of hikes.
 * Warm jacket - usually a fleece jacket, cotton not recommended, but it's better than nothing.
 * Windbreaker - this is only really necessary if you are going up high where there is a lot of wind exposure.
 * Hat - sun hat for sun, toque or some other warm hat for winter and cold conditions (up high)
 * Sunglasses - even if it's overcast it's always good to have these along. Especially if there's snow around.
 * Gloves - only when it's cold, highly recommended in the winter.
 * Daypack - for all your stuff!

Food
It is always a wise idea to take along food to eat, just make sure you pack all garbage with you. Always, ALWAYS bring water along. Although some fresh springs and glacier runoff may be clean enough to drink, rivers can contain bacteria that can make you very sick. Some suggestions for food might include GORP (good old raisins and peanuts) and variations, chocolate, energy bars and fruit (all things with high energy, and relatively low fat).

Dangerous Wildlife
There is always a chance of meeting an unfriendly animal while hiking in the mountains. In most cases, the best way to prevent this is to stay away from areas marked for recent bear or cougar activity, and to travel in bigger groups (i.e. 6 or more people). Bear spray can be purchased at many stores. Most encounters can be avoided simply by making noise from time to time, calling out every minute or so.

What to do if you encounter a bear/cougar
If you encounter a grizzly bear (big, brown, with hump between the shoulders) stop where you are. Slowly walk backwards until out of sight, then turn and walk (don't run) back the way you came. Notify any hikers you pass of your encounter. If in the rare case that a bear is aggressive and runs at you, do not turn and run. If you don't have pepper spray, lie on your stomach and cover the back of your neck with your hands. The bear will eventually become uninterested and leave.

If you encounter a cougar while hiking, place your backpack or (if you are hiking with children) or your head or shoulders, and make yourself look big. Back away slowly and return the way you came, notifying other hikers you pass. Cougars are generally not aggressive towards humans, and if you make lots of noise they generally will stay away.

Non-Aggressive Wildlife
Deer, elk, mountain goats and many species of birds and rodent wildlife frequent the Rockies. Although normally docile, males can become aggressive in mating season, and females can become aggressive if you happen between her and her young. Be cautious, but not paranoid. Always give animals distance, and approach cautiously. If the animal refuses to yield to you, it's best to go around.

Pests
Insects are always a nuisance. Mosquito repellent is highly recommended (except in the winter months). If you are hiking in areas with ticks, make sure you check yourself after the hike, especially around the sock line, collar and waist. Bees, wasps, and hornets are also sometimes a problem, so be sure to check your sugary beverage before drinking.

Pets
If you are planning to bring your dog along, make sure your dog doesn't tend to run after things. There are lots of things to chase in the mountains, including bears. If you trust your dog, then by all means, bring it along, your dog will love the mountains just as much as you!

Hikes
Now that you are ready to hike, here is the list of hikes. They are organised by area, and then by difficulty. if you are looking for a specific hike, then use the index.
 * /Day Hikes/

 * /Overnight Hikes/

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Hiking in the Canadian Rockies


text:
Hiking in the Canadian Rockies/Day Hikes

Day Hike Areas

 * /Banff National Park/
 * /Crowsnest Pass/
 * /Jasper National Park/
 * /Kananaskis/
 * /Kootenay National Park/
 * /Yoho National Park/


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis

Kananaskis
The Kananaskis Country is a large area, and can be divided into 6 distinct regions

 * /Bragg Creek and Elbow River/
 * /Canmore/
 * /Elbow Sheep Wildland Provincial Park/
 * /North Eastern Kananaskis/
 * /Peter Lougheed Provincial Park/
 * /South Kananaskis/


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/North Eastern Kananaskis

North eastern Kanaskis counts for the part of Kanaskis north of the Elbow River and the Elbow-Sheep wildland provincial park, and east of Exshaw. It includes Bow Valley Provincial Park, Barrier Lake, and the Sibbald area. It also includes the section of Bow Valley Wildland Provincial Park directly north of Bow Valley Provincial Park.

Intermediate Hikes

 * /Barrier Lake and Prairie View Trail/

Advanced

 * /Black Rock Mountain/


text:
User talk:Gansch

Sweet, I didn't know about that error correction; thank you!

Mattb112885 21:04, 5 September 2006 (UTC)

title: User talk:Gansch


text:
Flute/Tonguing

Basic tonguing
Unless specified in music, notes should always be tongued. At this point you should know how to produce sound. If you do not, read the previous lesson. If you do, begin by producing sound a few times. As you begin to blow each note, move your tongue as if you were saying "tu" (pronounced "too") or "du" (pronounced "do"). Practice this until you have a smooth sound. After this, play several notes. This is done by blowing a single stream of air separated by the sylables of "tu". As you practice this remember a few things: When tonguing, use the tip of your tongue to produce a clearer sound, this also prevents the sound from sounding like "lu". Also listen to the sound, if the sound stops completely, you tonguing is too heavy. If this happens, just don't say the syllables as heavily.

The objective of basic tonguing is to produce notes with a clearer-sounding attack. The tongue should act like a pressure release valve, attacking each note with a strong stream of air.

Staccato (short) tonguing
From the basic tonguing, change the syllable to "ta" or "da", and cut the air stream off after half of the notes value. Do not, just lower the amount of air you use, or you will produce a marcato effect. Also, do not use too much air, or you will get a rinforzando or accented note.

Tonguings to avoid
Do not use "ba", "ma" or "pa". These start with the lips closed, and cause the sound to be ambiguous at the beginning of a note, which is for the most part a bad sound.

For now, do not use "ku" or "qu" (pronounced "Coo") or "Gu" (pronounced "Goo"). These tonguings will be used later with double tonguing, but get used to basic tonguing first.

Don't use "la", "ya", "sa" or "za". These produce a vibrato like sound. "Ha" is used to produce a vibrato, but don't worry about that now.

title: Flute/Tonguing


text: User:J Hill~enwikibooks/Sandbox

title: User:J Hill~enwikibooks/Sandbox


text: Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Peter Lougheed Provincial Park


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Canmore

Beginner Hikes

 * /Cougar Creek/
 * /Goat Creek/
 * /Stoneworks Canyon/

Intermediate Hikes

 * /Cougar Creek/

Intermediate

 * /Chinaman's Peak/


text:
Physics Exercises/Fundamental Constants

=Table of Constants=

 * 1 Atmosphere Pressure (1 atm) : 1.0 × 105 N/m2 = 1.0 × 105 Pa
 * 1 Electron Volt (1 eV) : 1.60 × 10−19 J
 * Bohr radius (a0)   : 5.292 × 10−11 m
 * Coulomb's Law Constant (k) : 1/(4 π ε0) = 9.0 × 109 N·m2/C2
 * Faraday constant (F)          : 96,485 C·mol−1
 * Gravitational accelaration (g) : 9.80665 m·s-2
 * Mass of a neutron (mn) : 1.67495 × 10−27 kg
 * Mass of Earth : 5.98 × 1024 kg
 * Mass of the Moon : 7.35 × 1022 kg
 * Mean radius of Earth : 6.37 × 106 m
 * Mean radius of the Moon : 1.74 × 106 m
 * Dirac's Constant ($$\hbar$$) : $$h/(2\pi)$$ = 1.05457148 × 10−34 J·s
 * Speed of sound in air at STP : 3.31 × 102 m/s
 * Unified Atomic Mass Unit (u) : 1.66 × 10−27 kg
 * Vacuum Permittivity (ε0) : 8.85 × 10−12 C2/(N·m2)

=See Also=

Wiki-links

 * Wikipedia Article

title: Physics Exercises/Fundamental Constants


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Bragg Creek and Elbow River

Bragg Creek and South of the elbow river encludes the Sheep River, Mclean Creek off road vehicle area, and the Elbow River Recreational Area.


text: Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Elbow Sheep Wildland Provincial Park


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/South Kananaskis

Beginner Hikes
/Ptarmigan Cirque/


text:
Transwiki:Labeling family photos

Labeling family photos is a process of identification of persons and objects captured on family pictures. Identification lets a family historian get to know ancestors’ faces and record information about family members for future generations.

Identification of paper photos can be relatively easy since identification notes can be written on the back side and therefore are an integrated part of picture content. On the other hand, writing names and additional information on the back side does not necessarily ensure identification clarity, and especially on group photos.

Now, in the information age, digital photography brings new challenges:
 * Digital photos do not have a back side. It is unlikely that someone would want to spoil paper family photos by writing identification notes directly on an image. Similarly, placing labels that cannot be hidden, if necessary, on digital pictures can be hardly a solution for a family historian.
 * Digital photos are shared through different means, including blogs and email, so identification labels should be distributed together with the pictures.
 * Growing number of digital photos requires search capabilities so a specific person can be found quickly.

There are a plenty of photo annotation software programs that enable users to place identification labels on digital photographs in a variety of ways. They can be divided into the following categories:

 * Tools that let a user locate and put on a photo identification labels that are “imprinted” into the image and therefore become an integrated part of the picture. The photos can be shared through various means, such as email or blogs, together the identification labels. On the other hand, since the labels are treated as a part of the image, they cannot be used for search purposes. In addition, there is no way to disjoint from the photo meaning the identification labels cannot be hidden so an original family picture view can be spoiled.

 * Tools that allow a user to place identification labels stored in an application’s internal database. Users can use search capabilities. However, when a picture is shared or published in the Web, identification labels are lost because they remain in the internal database and cannot be distributed with the photo.

 * Online tools that enable a user to upload an image and put identification labels online. They provide features for sharing through blogs and communities. However, if such picture is downloaded to a local computer, identification labels are lost and cannot be seen.

 * Desktop tools that store identification labels in the special metadata section of the same file. This ability enables distribution of the labels together with the file regardless of how exactly it is shared – email, blogs, or publishing on a Website – and search across them. On the other hand, the identification labels can be hidden in order to view an original pure photo. The main disadvantage is support for JPEG files only so identification labels cannot be placed on GIF, BMP, and PNG files.

title: Transwiki:Labeling family photos


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Canmore/Chinaman's Peak

Information
PD

Distance - 1.6km

Elevation Gain - 732m

Access
The trailhead can be accessed by driving up the Smith-Dorrien--Spray Trail (Hwy. 742), Parking in Whiteman's gap, at the Goat Creek parking lot.

The Hike
Cross the highway and walk up the road to the canal and across the bridge. The trail starts behind the hut.

An enjoyable stroll turns into a steep climb following a watercourse, with some switchbacks nearing the treeline. as you emerge onto the scree be sure to note the location of the trail exit. You can make your way up the mountain directly, or hook right and follow the easier ridge. The Carin at the top is perched right on the edge, beware.


text:
User talk:Qwilleranfan

Hi Qwilleranfan,

Great idea for a book! One thing: if you're taking the images (maps) from a government website, it's probably a good idea to leave a link to the site where it came from. I assume the Canadian government probably has public domain laws similar to those of the U.S., but I honestly don't know.

You've inspired me to try to write some for Pennsylvania some day... thanks! -- SB_Johnny | talk 22:34, 5 September 2006 (UTC)

Renaming pages
G'day, I notice you've been accidentally creating pages for your hiking book outside of the book. To bring them into the book, just click on the "move" tab at the top of the page, and add the chapter path in front, e.g. "Hiking in the Canadian Rockies/Day Hikes/Kananaskis/South Kananaskis/". This way, you don't have to copy all the text across. Later, if other people edit a page that needs renaming, you can preserve the edit history by moving the page, something you can't do (easily) with the copy-and-paste approach. cheers, Webaware talk 05:13, 23 July 2007 (UTC)

title: User talk:Qwilleranfan


text:
User:Qwilleranfan

Hey,

I am a high school student in Calgary, Canada. My main reason for joinin wikibooks was to write a book on Hiking around my area. Hopefully it is useful.

title: User:Qwilleranfan


text:
Cookbook:Teff

Teff, also known as lovegrass, is an important food grain in Ethiopia and Eritrea, where it is used to make injera. Teff is also grown on a small scale for human consumption in India, Australia, the Netherlands, and the United States, and as cattle feed in South Africa. Teff is believed to have originated in Ethiopia between 4000 BCE and 1000 BCE. Teff produces up to two-thirds of the total food provision of Ethiopia.

Teff is the world's smallest cereal, with each grain being less than 1/32 in (0.8 mm) in diameter. It takes 150 grains of teff to make up the mass of a single grain of wheat. Due to its small size, teff has a very large percentage of its mass made up of the bran and germ of the seed, with a relatively small endosperm. It is also difficult and expensive to remove the bran and germ of such a small grain, so almost all teff products and teff flour are made of whole grain teff.

The grain has a high concentration of different nutrients. This grain has a very high calcium content, and contains high levels of phosphorus, iron, copper, aluminum, barium, and thiamine. Teff is high in protein. It is considered to have an excellent amino acid composition (including all 8 essential amino acids for humans) and has lysine levels higher than wheat or barley. Teff is high in carbohydrates and fiber. It contains no gluten, so it is appropriate for those with gluten intolerance or Celiac disease.

 * This module is adapted from the Wikipedia article Teff. Please see the Wikipedia article for a list of authors.

title: Cookbook:Teff


text:
Hiking in the Canadian Rockies/Day Hikes/Kananaskis/Canmore/Goat Creek

Information
PD

Distance - approximately 5km

Elevation Loss, east to west - approximately 200m

Access
From the Canmore townsite, take the Smith-Dorrian/Spray Trail (Hwy. 742) up into Whiteman's Pass. Park in the Goat Creek parking lot.

The Hike
The hike starts right in the parking lot, and a wide defined path gently winds its way down the valley. Options to continue onto other lookouts and eventually Banff (approximately 18km). Allow 4 hours round trip.


text:
User:Tdush200

yak shimaesh

title: User:Tdush200


text:
User:Tcamp468

Hello world.

title: User:Tcamp468


text:
User:Areil123~enwikibooks

Type in what ever you'd like.

=Section 1= this is content just in section 1

section 1a

 * Introduction
 * Hardware
 * Software
 * Personal technology
 * Artificial Intelligence
 * Networks
 * Internet and WWW
 * Challenges (bugs and crime)
 * Databases

title: User:Areil123~enwikibooks


text:
User:Skrug352

Hi

title: User:Skrug352


text:
User:Cweiss

Business

Business affected by computers

title: User:Cweiss


text:
User:Msato613

Hello people

title: User:Msato613


text:
User:Gjanm752

yo

title: User:Gjanm752


text:
User:Clund776

I am very tired tonight.

title: User:Clund776


text:
User:Ckenn423

Hi

title: User:Ckenn423


text:
User:Michelle~enwikibooks

hello everyone

title: User:Michelle~enwikibooks


text:
User:Mkinn907

Welcome to Wikibooks.

title: User:Mkinn907


text:
User:Dgill222

Applications
Applications for computers are a necessity for everyone and even more important for those in academia. Computer application software is an interface between the user of the computer and the operating system of the computer. This software allows an infinite number of uses for a computer. Typical computer applications would include: word processors, spreadsheets, databases, media players, presentation software, and e-mail.

Word processors, next to e-mail, are likely the most used computer application by students. Word prcessors allow for assignments to be legible, formatted, spell-checked, and printed. It allows students to concentrate more on the content of their projects and focus less on the grammar and spelling.

Spreadsheets are a necessity for all business students. Spreadsheets are used to tabulate numbers and create graphs and charts. With the built-in calculation functionality it saves students the possible errors in manual calculations and a number changed on the sheet will change all the connected numbers in real time.

Many classes now also require Microsoft Powerpoint for in class presentations. Presentation applications like PowerPoint provide a relatively simple, professional format of project presentation. By creating individual slides, a student has full control over the visual and audio aspects of their presentation. Again this allows for more concentration on the content and less focus on the presentation display. It also allows for quick, easy, and possibly frequent changes to content.

Many educational institutions such as colleges and universities now use web portals for personalized access to course materials, grades, fees as well as other information.

The most ubiquitous application not only for students and academics, but for the world at large is E-mail or Electronic Mail. Though many primary and secondary schools frown on free mail services. Many of them have set their firewalls set to prevent access to these services. The schools have purchased their own domains and created their own E-mail services for their students and faculty. E-mail allows for near instant letter communication with their professors, other students, and the school administration.

Programming Languages History
The first programming language developed was FORTRAN in November 1954 which progressed to FORTRAN I in October of 1956, FORTRAN II in 1957 and a form of FORTRAN is still used today. There have been several programming languages that were created from scratch. Fortran was the first one, then there was: B-O in 1957 which transformed into the better known COBAL in 1958, LISP arrived in 1958, APL in 1960, Snobol in 1962, JOSS in 1964 which has morphed into M ANSI ISO, Forth in 1968, sh in 1969, Prolog in 1970, ML in 1973 and B in 1981. (ref#1). All other marketed languages can have their history traced back to one or more of these languages at some point in time.

HTML
HTML or "Hyper Text Markup Language" a programming language mostly used in the creation of Web Pages. A markup language simply denotes a form of programming in which there is text with extra information relating to that text. With HTML this is accomplished by using tags, which are commands in brackets like <>. Putting a B in the brackets before the text and a /b in brackets after the text will bold that text. HTML gained wide acceptance in the creation of web pages because it is simple to use and understand. Most of the web is primarily text based.

XML
XMLor "Extesible Markup Language" is an advancement over HTML. It has had a tremendous impact on the internet, surfing and the transmission of data. It allows two computers to communicate with each other. RSSor Really Simple Syndication allows for applications to update automatically when updated by the webmaster. This incredibly powerful feature has helped the expansion of blogs (web logs) which are frequently used as online diaries and vblogs (video web logs) which are blgs with a video component.

JAVA
Java is a programming language that allows interactive web pages. It is has its language taken from C and C++ but is much more simpler. With Java animation is also relatively easily done.

OS Classifications
There are several types of Operating Systems which can be catagorized. Multi-user operating systems two or more users to run programs at the same time. Mount Royal College uses a multi-user operating system for the school. It can handle hundreds, if not thousands of concurrent users. A Multiprocessing OS can allow a single program to run on more than one CPU. Multitasking OS's allows more than one program to be running at the same time. Multithreading allows for different parts of the same program to be running concurrently. And finally, Real Time operating systems have an instant response to input.

Current Implementation
Everyone is aware of operating systems and their function to translate applications into instructions that the computer can understand. However, operating systems are much more prevelant than most people suspect. They now persist not only in laptops or desktops, but in a wide variety of other devices. Operating systems have extreme versatility, especially with today's technologies. They also have large scaleability, which means that operating systems can be simplified greatly or have features even the programmers may not be aware of. Operating systems now are used on routers, PDAs (Personal Digital Assistants) and mobile phones as well as a multitude of other computers including laundry machines and refridgerators. This does make sense as the computer in a typical modern cell phone is now more powerful than a desktop computer from 20 years ago. It also allows for customization of cellphones such as individualized rings and wallpapers.

Security
Current operating systems have numerous 'holes' in their programming. These vulnerabilities make it possible for people to 'attack' and/or use your computer with, or more commonly without, your knowledge. Microsoft has well documented weaknesses, but that could have much to do with the number of users who are interested in the operating system, and the amount of attention it receives since it is the most common operating systemin the world. There are methods to close these holes. One of the newer abilities of well known operating systems is the ability to update the software either manually or automatically. These updates are normally downloaded to your computer from the internet and installed on your computer, basically changing the structure of the programming to make the operating system more secure. Another option is a program like Norton anti virus. It is one of the most common, but there are many other choices the consumer has the ability to choose from. Anti viruses protects your computer from outside dangers, such as hackers and scammers to viruses. A hacker can log onto your computer and see all your personal information, and possible have access to even your banking information. Viruses are common in today's world, they come from recieving files, downloading things off the internet, or even visiting certain sites. Virus programs work with your operating systems starting up when you start the computer and constantly check everything the computer does for anything that might be a threat.

Tape Drives
Tape drives research began in 1949 by IBM. The whole process was to find a suitable replacement for punch cards. The necessities being the replacement should be compact, faster, cheaper and reusable. The big difference between a tape drive and a audio cassette tape is in the machinery. The drives themselves are much quicker and more accurate than a home cassette player. The tapes store data in a continuous string of bits, also known as, sequential data, and the need to find a particular part of the information that is being searched for requires a mechanically efficient and accurate machine. They are able to fast-forward and rewind to a particular spot on the tape with high speed and accuracy. This is the image of the large reel-to-reel machines seen in old television and movies, and are still used today for their cost effectiveness for backups. Backups are the recording of data from a computer hard drive to another secondary storage device. Although compact discs are gaining in popularity, tape drives are still widely available. The improvement in tape drives has been dramatic since their inception. The original tape drive, IBM 701 Tape Drive, could store 100 bpi (bits per inch), run at a speed of 70 ips (inches per second) and could be as long as 1400 feet. Since then tapes have evolved to run 200, 556, 800, 1600, and even 6250 bpi. They run at greater speeds than original, and have lengths up to 3600 feet. Tape drives were at their prime up until the 1990's. Then the flexibility, speed, and storage abilities of hard drives overtook tape drives. As mentioned earlier, tape drives are still available, but are now relegated to inexpensive backups of vast amounts of data.

Wireless Mouse
The classical wired mouse, although it has changed connectors to the computer, is still the most used type of mouse. However, the new wireless technologies are allowing for wireless mice to become more prevelant.

Most wireless mice use radio frequency (RF) technologies to communicate information to your computer. The RF technology used is frequently the Bluetooth technology. It doesn't matter whether the mouse uses normal RF technology or the standards associated with Bluetooth. Each requires two main components: a transmitter and a receiver. Here's how they work:

1. The transmitter is housed in the mouse. It sends an electromagnetic (radio) signal that encodes the information (possibly by Bluetooth) about the mouse's movements and the buttons you click.

2. The receiver, which is connected to your computer, accepts the signal, decodes it and passes it on to the mouse driver software and your computer's operating system.

3. The receiver can be a separate device that plugs into your computer, a special card that you place in an expansion slot, or a built-in component. Many laptop computers now come with built-in Bluetooth capabilities.

One of the biggest advantages of radio frequency over another well tested technolgy for short distance wireless communications, infrared, is the lack of need for a line-of-site transmission. Radio frequencies work in a sphere from the transmitter.

An important note to wireless mice is the necessity of being "paired" with it's receiver. Pairing means that the devices are both operating on the same frequency, same channel, and use a common identification code. The reason pairing is so important is to filter out interference from RF devices and other sources.

Backbones
In 1987 the National Science Foundation (NSF) created the NSFNET (National Science Foundation NETwork)which was the first hight-speed network backbone in 1987. There were 170 smaller networks that were connected by a T1 line and was able to transmit at the incredible speed of 1.544 Mbps). This speed is fantastic due to the fact that most modems of the time operated at 300bps, if a computer had a modem. Although the National Science Foundation began the projoct it worked closely with IBM, MCI and Merit. In 1988, in cooperation, these companies developed a 45Mbps backbone. This is known as a T3 line.

Backbones are the basic infrastructure of the internet. They are high speed lines that directly connect large hubs, companies and academic institutes. Typically trunk line backbones are made of fibre optic cables. Many of these fibre optic cables are bundled together to increase capacity. The rating system for fibreobtic cables is designated with OC for optical carrier. For example an OC-3 has a transmitting capacity of 155Mbps whereas an OC-48 can transmit 2488Mbps (2.488Gbps). An OC-48 is about 44,430 times faster than a standard 56Kbps modem still available today. This huge network of backbones between countries governments, educational institutions, research institutions and companies operate their own backbones which interconnect. The entire network is a gigantic agreement between these institutions sprawling around the world allowing the freedom of intercommunication.

Diagnosis
A form of artificial intelligence is being used more and more frequently in diagnosis. There are all types of areas where A.I. can determine whether the behaviour of different systems is correct. Initially, the easiest systems for computer intelligence to calculate whether systems are being run to specifications is other computers. Automobiles are a prime example of this. There are increasing numbers of sensors for every new model year in automobiles. A computer can be plugged in and, after copying the information recorded by the sensors, make a determination as to any problems that fall outside the normal range of use. It is important for computer system algorithms to be able to determine which part of a system is failing, where that part is located, the type of fault in the part and many systems now provide the steps to fix the problems. All diagnosis is based on observations which are taken by different sensors.

A major determinant to the effectiveness of A.I. to accurately diagnose problems is the base of knowledge it works with. The number of variables involved in even simple diagnoses like an automobile are large. Then for each variable there is a different weight applied to each. Then each weight can change over time. These calculations become more and more complex the more variable the subject. The initial knowledge usually comes from people who are experts in a particular field. However one of the major tasks of the creation of A.I. is the development of intuition which mankind is able to utilize.

In time it is likely that artificial intelligence will be able to diagnoses with a high degree of accuracy, not only technical systems with the necessary number of sensors, but organic matter as well. Walk into a doctors office and let the wall know how you are feeling. Next thing you know the room speaks to you and tells you both your diagnosis, treatment, and prognosis.

Data Mining
Data Mining is a process that uses rules of association with the collection of vast amounts of data. It incorportates statistics, data collection and recognition of patterns and trends. The most common type of data mining today is the use of programs within programs that record computer habits, websites visited and much more information about both the user and computer. The analysis of the data provides profiles that are used by all kinds of organizations. Frequently the programs to do the data mining are included in purchased software and downloaded software. However it is also frequently installed on a computer through the use of a virus or worm or other such malicious tool.

There is no inherant danger to data mining. It is the use of the information that is most troubling. When such techniques can include information like credit card numbers and bank accounts there is an obvious troubling potential for the use of the date. What is meant by no inherant danger is the software data mining collection does not damage a computer, it just records what the computer is doing.

One of the major reasons for collecting such vast amounts of infomation is for resale. Different on-line merchants would like to know where and when each online shopper is spending their money. Then they can use that informatio to direct their marketing and timing to a more dedicated market.

The data that is mined, or collected, can come from a vast array of sources. As stated above, the most common form of data mining is the infection of a computer. It can also be extracted from POS (Point Of Sale) transactions, all kinds of data bases, online resources, articles, etc. Although this is an easy way to gather information there is also off-line sources and databases that can be included through the old-style manual data entry.

[edit] Fusion/cleaning

With all the information the recieve the company must filter through the information to find what the need

[edit] Data

Meta-Data is data about data; it describes how and when and by whom a particular set of data was collected and how it’s formatted. Meta-Data is essential for understanding information stored in data warehouse

[edit] Warehouse

Data warehouse is a special database of cleaned up data and Meta-data. Both the data and the Meta-Data are sent to the data warehouse.

Paypal
Paypal is a third party e-commerce company. They are capable of debiting and crediting credit cards and bank accounts for those with an account. Although credit card or banking information is not required for all services Paypal provides, they are required for many of them. Paypal is one of the world's primary methods of online payment with more than 100 million accounts worldwide.

Paypal allows for online payments for individuals and businesses to transfer funds electronically and securely. There is powerful encryption software that is used to allow people to make these financial transactions. The funds that are transferred by paypal are held in a Paypal account until the person with control of the account specifies what are to be done with the balance. They can be credited to the credit cards or bank accounts set up with the paypal account, or can be used for other puchases and transactions through the paypal system.

Paypal is especially good for use on online auctions, purchases of goods and services, or to make donations. It is a secure third party operator which limits the amount of personal information that must be passed around for normal internet transactions. The only information that is given is a paypal account number and all financial transactions are accomplished by paypal. It can even sent cash.

There is now some competition to Paypal such as "C2it" and "Certa Pay" (A canadian company).

Repetitive Strain Injury
Also commonly known by "RSI", Repetitive Strain Injuries are the result of repeated physical movements which can damage tendons, nerves, muscles and other soft body tissures. There is no limitation on the occupations which this sydrome is related to. It can be anybody form musicians, to computer techs, to factory workers.

When it comes to computers these injuries seem to be causing an epidemic directly related to the increase in computer use. Especially affecting the hands, arms, and shoulders. One of the main culprets of Repetitive Strain Injuries is the use of a mouse or trackballs. If there is an initial injury, draging the mouse slowly actually increases the damage. There is also a problem with the thousands of repeated keystrokes which work the same muscles in the same way over and over, causing the injury. The typing technique and body position is extremely important. Incorrect positioning leads to unnecessary stress on the tendons and nerves in the hand, wrist, arms, and even the shoulders and neck. Lack of adequate rest and breaks and using excessive force almost guarantee trouble.

What are the Symptoms? 1) Tightness, discomfort, stiffness, soreness or burning in the hands, wrists, fingers, forearms, or elbows

2) Tingling, coldness, or numbness in the hands

3) Clumsiness or loss of strength and coordination in the hands

4) Pain that wakes you up at night

5) Feeling a need to massage your hands, wrists, and arms

6) Pain in the upper back, shoulders, or neck associated with using the computer.

Object Oriented Programming
OOP (Object Oriented Programming)uses objects which are self-contained items that have a data type, a data structue, and can also have the data. For example an object might be road objects, vehicle objects, landscape objects which could be part of a driving simulation.

The object is self contained in that it only has necessary data sent to it, and the results are sent back. To change a current object takes a little more work. Especially if the source code is not available for the object, only the functionality. The objects have both functions and data and can be related to other objects.

One of the principal advantages of object-oriented programming techniques over procedural programming techniques is that they enable programmers to create modules that do not need to be changed when a new type of object is added. A programmer can simply create a new object that exhibits many of its features taken from existing objects. This makes object-oriented programs extremely easier to modify.

To perform object-oriented programming, one needs an object-oriented programming language (OOPL). Java, C++ and Smalltalk are three of the more popular languages, and there are also object-oriented versions of Pascal.

Refresh Rate
The refresh rate refers to monitors, televisions and other visual display devices. It is also known as: "vertical refresh rate", or "vertical scan rate for CRTs. It refers to the number of times in a second that a display is fully lit up. For a CRT (Cathode Ray Tube) this is the number of times the ray draws from the top corner of the screen to the opposite bottom corner, in one second. It is measured in hertz. It is this phenomenon that causes the bar on a screen that is seen on a television show as the refresh rate is not enough to compensate for the intermediate frames taken by the camera.

This is in contrast to a frame rate, which is the number of frames shown per second. Whereas if a monitor has a 48Hz refresh rate and the show is at a 24 frame rate, then the screen will be lit up twice for each frame that appears on the screen.

Sampling Rate
The sampling rate for audio is the equivilant to the refresh rate for video. There are instances that the refresh rate is called the sampling rate interchangeably. In audio, this is the number of times a second that the sound input is recorded and saved. The sample rate of an audio recording is a good indicator of the overall sound quality. With the same measurement unit as the refresh rate, it is a noticeably higher number for a sampling rate for audio. Here are some rates and what they are commonly used for:

 * 8,000 Hz - telephone, adequate for human speech
 * 11,025 Hz
 * 22,050 Hz - radio
 * 32,000 Hz - miniDV digital video camcorder, DAT (LP mode)

title: User:Dgill222


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User talk:Beauty5620

It's me, glad to meet you all ;)  Just testing stuff Testing again...

Operating Systems
 Boots up the comp organizes files preforms tasks (takes things out of the hards drive) operating system to log in (Novell) security (firewall)

Turning on
When booting up a computer there must be a basic operating system. There are multiple operating systems available for the consumers to choose from; starting with the most common windows, to server operating system, linux. Windows is made to be user friendly, even those who know little about computers can easily master the basic commands. Linux comes in many different forms, it is meant more for those who are already aware of how computers operate, with complex codes and hard to use commands.

Basic functions
Operating systems manage your files. They take your files and put them safely in your hard drive. It does the same function as you taking your papers and storing them in a filing cabinet till when you need them next.

security
Norton anti virus being the most common, but there are many other choices the consumer has the ability to choose from. Anti viruses protects your computer from outside dangers, such as hackers and scammers to viruses. A hacker can log onto your computer and see all your personal information, and possible have access to even your banking information. Viruses

turning off
When you turn off your computer it takes some time to file everything you have done since your last shut down. It will remember how your computer last looked.

title: User talk:Beauty5620


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User:Jeancheng

Happy day

title: User:Jeancheng


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User:Scote480

hello new world

title: User:Scote480


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User:T1la

Welcome to my Wikibooks page.

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User:Dpool688

Hello world

title: User:Dpool688


text:
Space Transport and Engineering Methods/Physics

 Space systems use advanced technology to operate in space and use the resources found there. A basic understanding of the sciences underlying the technology is important. This chapter is only a brief introduction. Links and references to more detailed sources are below.

 The key formulas from physics and other sciences are first presented in ideal terms. The real world is not as simple as that. Less than ideal behavior has to be accounted for, such as friction or perturbing additional forces. So do measurement uncertainties, environment variations, equipment wear, and other factors. These represent the difference between physical laws and practical engineering.

 Physical principles are usually expressed mathematically as algebraic formulas and geometric relationships, with supporting explanations to provide meaning and context. When known numerical values with proper units are inserted into these formulas, you can solve for an unknown value you wish to know. The ability to calculate unknown values is enormously useful when designing or operating any project. As noted in the introduction to Part 1, the reader should have enough understanding of mathematics to use these formulas.

1.0 - Science and its Branches

 Scientific knowledge is an undivided whole. For study and understanding we divide into branches, but they often overlap and share ideas. Physics is the study of how the Universe behaves in its component parts such as matter, energy, forces, motion, space, and time. Astronomy is the study of objects and phenomena in the Universe at large scales, and Planetary Science in particular studies objects orbiting stars. Chemistry studies the properties and changes of matter at smaller scales and lower energies than found in stars. The many branches of the Life Sciences matter for any space projects that involve living things, especially people.

 Knowledge is gained by the Scientific Method and ideas developed to explain what we see. There are many ideas, but only one reality. So experiment and observation are used to determine which ideas best match that reality. Ideas are loosely graded in quality; as hypotheses, theories, principles, and laws. These grades are based on how firmly and widely the ideas have been tested.

 In the sciences, no idea is considered final or absolute truth. They are always subject to revision or replacement when confronted by new observations and experiments. Each new observation increases our degree of confidence in successful ideas. Many of them have been tested for so long, and in so many ways, that we rely on them routinely, even in engineering projects whose failure would be catastrophic.

2.0 - Physics

 Most of the physics we use in engineering is well-grounded - based on things we can see, test, and use. For example, Quantum Mechanics is illustrated by spectral lines of gases, and the Theory of Relativity by observing bodies in motion through the solar system. These theories have engineering consequences in some applications, such as the design of lasers and the timing of satellite signals from the GPS Network.

 Other observations, like rotation curves and gravitational lensing of galaxies, don't yet have a good explanation or any practical use. We call what causes those observations Dark Matter, but we don't yet know what dark matter is. Physics and the other sciences are unfinished works in progress. Many parts are well understood and settled, and we can use that knowledge in projects. But around the edges are parts still being worked on, and beyond that the unknown.

 Some ideas in Theoretical Physics explore aspects of reality that are not easily observed. They need devices like large telescopes or particle accelerators to collect data, or nobody has figured out a way to test them yet. Theoretical ideas can be developed with nothing more than mathematics, a pencil, and pad of paper. So there are a lot more such ideas than firmly-tested theories.

 In some cases, it is possible to test an idea by looking for logical consequences which would not be true in competing ones. For example, measurements of the Cosmological Constant have helped narrow down theoretical ideas about the origins of the universe. We can exclude ideas that predict the wrong values.

 2.1 - Information Sources

 For more detail on physics in general, you can refer to any of the following sources:

 * Articles linked from Wikipedia's Outline of Physics and books in varying stages of completion in the Wikibooks Physics subject heading.
 * The many articles linked from Wikipedia's Index of Physics Articles,
 * The visually outdated but still useful HyperPhysics website.
 * Many short videos and tutorial materials from the Khan Academy.
 * Open-source online textbooks like Light and Matter and Motion Mountain, and the CK-12 Physics textbook previously noted in the Part 1 page, Section 3.0.
 * Used or new printed college physics textbooks, and digital ones from the Internet Archive.

3.0 - Units and Position

 3.1 - Units

 To get the correct results from a formula, it is necessary to use a consistent set of units, and accurate ways to measure physical quantities such as length in those units. For example, adding two feet to three meters to get five of something does not produce a meaningful result because the units are different. You can use anything from body parts of known size to laser Interferometry for length, depending on the accuracy needed.

 The International System of Units, abbreviated from the French to SI, is the preferred system of units for engineering and scientific work. It is also known as the Metric System because the base unit of length is the "Metre" (or meter). Physical quantities include both the numerical value and the units. Units must be handled mathematically the same way as the numbers are. So in the formula F = ma (force equals mass times acceleration), m is in kg, a is in m/s2, and F is then in kg-m/s2.

 For historical reasons, some values in space systems design are reported in US customary units, but these should be converted to SI values. There are also units of convenience, such as g-force being a multiple of Earth's surface gravity. This is useful to describe the relative effects on people and equipment compared to the normal value on Earth. But it should always be recognized as a convenience, and converted to SI units for other calculations. The standard value is 1 Earth gravity (g or gee) = 9.80665 m/s2. The actual value at any point on the Earth's surface varies by about 2% from this.

 The base SI units are the Metre ("meter" in the US) for length, Kilogram for mass, Second for time, Ampere for electric current, Kelvin for thermodynamic temperature, Mole for amount of substance, and Candela for luminous intensity. Their symbols are m, kg, s, A, K, mol, and cd respectively. They are not defined in terms of other units. Since 2019 the base units, and and other units derived from them, are determined from by declaring exact numerical values for seven constants of nature, then calculating the units from those constants.

 Derived SI units are the products of powers of the base units. For example, the unit of force, called the Newton, is 1 kilogram-meter divided by seconds squared (kg-m/s2). Many of the derived units are named after famous scientists, but these named units are identical in value to the form expressed in base units. Multiples and sub-multiples of units are indicated by prefixes which indicate integer powers of ten ranging from -30 to +30. Among the more common are kilo, indicating 103 or 1000, and milli- indicating 10-3 or 0.001.

 3.2 - Position

 In a universe of three physical dimensions, it takes three values to define a position uniquely, either distance in three axes, or a radius and two angles. These values are known as the object's Coordinates, and the types of values used make up a Coordinate System. In modern physics there is no absolute or preferred reference frame in the universe. So position is measured relative to a chosen starting point known as the Origin, which is assigned coordinate values of zero.

 For example, vertical position or Altitude on Earth is measured relative to sea level in the direction opposite the local gravity direction (up). On bodies without an ocean, an Ellipsoid based on the shape of the body is defined as zero altitude. On gas giants, which do not have a visible solid or liquid surface, altitude is referenced to pressure.

 For horizontal position Latitude and Longitude are measured relative to the points where the surface meets the axis of rotation, which are called the Poles, and a point assigned values of zero in both coordinates. On Earth, the zero point is where the Prime Meridian (zero longitude) crosses the Equator (zero latitude). This is in the Gulf of Guinea west of Africa.

 Units of Degrees, which are 1/360th of a circle, commonly measure the location relative to the zero point. This is useful for finding which parts of a body face the Sun (days and seasons), face their parent body in the case of moons, and when communications are possible. On other bodies the zero point is set arbitrarily. Very irregular smaller bodies may have multiple surfaces at a given latitude/longitude pair, in which case radius from the center of mass can be used rather than altitude. Horizontal position, or all three dimensions, can also be stated directly in meters relative to a zero point. Positive directions for each dimension define a Cartesian Coordinate System.

 Objects in space are generally moving in relation to each other on paths governed by gravitational forces. When the paths are purely the result of gravity and repeat they are called Orbits. They are defined by six parameters called Orbital Elements, from which you can calculate position at a given time. When position is more useful, it can be described in three dimensions relative to an origin, such as the center of the Sun, with axes defined relative to the stellar background. Alternately a radial distance and two angles relative to a reference plane can be used. For the Solar System, the reference plane is typically set by the Earth's orbit around the Sun, known as the Ecliptic.

4.0 - Motion

 Kinematics is the subject that covers the motions of objects. It is important for space systems because bodies in space, orbits around them, and getting to a desired location in space all involve motion. We cannot cover the whole subject here, but to learn more there are many sources of the types noted in Section 2.1 above. Here we will cover a few key terms and formulas.

 Displacement is the net change in position. It has both amount and direction, such as "three kilometers North". Velocity is the rate of change in position per unit time. When stated without a direction and purely as an amount it has a single value in units of meters per second. Where x is position in the direction of motion, t is time, and the Greek letter delta (which looks like a triangle in its capital form) indicates the change in those values, then velocity v is given by the formula:

 * $$\bar{v} = \frac{\Delta x}{\Delta t}$$

 Acceleration is the rate of change in velocity, for which the formulas are

 * $$ \bar{a} = \frac{\Delta v_x}{\Delta t} = \frac{d^2x}{dt^2}$$

 where acceleration a is the change in velocity divided by the change in time (duration), or the second derivative (change in the changes of) position x divided by the square of the time interval.

 The horizontal bar over v and a in the respective formulas indicate the velocity is directional. A value such as this with both an amount and direction is called a Vector, while a value without a direction is called a Scalar. The direction can be given in terms of two angles, or the velocity can be expressed as components in the three (x, y, z) axes of a reference system, but either way a total of three values are required to state a velocity vector. Linear Algebra is a method for doing calculations with vectors. It is somewhat different and more complex than simple algebra.

 In accelerated motion, the velocity at any given instant is changing. We can define an Instantaneous Velocity at a particular time, and an Average Velocity over an interval. In a closed orbit the moving object returns to its starting point. So for a full orbit, the net change in position is zero, and as a vector the average velocity is also zero. If you measure the total length of the orbital path and divide by the time one orbit takes, you can obtain an average orbital speed as a positive scalar value. This illustrates how different vector and scalar values can be.

 Acceleration can also change with time. For example, the accelerating force due to gravity changes as the inverse square of distance. So a falling object will increase in acceleration as it gets closer. Under constant acceleration a in a straight line over time t we can determine change in position or distance d from:

 * $$ d = \Delta x = 1/2 \times at^2$$

 In circular motion, where v is the velocity and r is the radius, we can find the acceleration a from the following formula:

 * $$ a = \frac{v^2}{r}$$

 One use for this formula is finding a required velocity for a circular orbit from the acceleration of gravity (see under Forces below) and the radial distance from the center of the body. Note there is no centrifugal force. Gravity or a rotating structure provide an inwardly directed force to maintain circular motion of the object, but there is no outward one.

5.0 - Forces

 The 20th century theories of General Relativity and Quantum Mechanics are more accurate predictors of how objects behave in the realms of the fast and the small, but in many cases the simpler formulas of Classical Mechanics are accurate enough to use. Examples where classical mechanics is not accurate enough include long term changes in the orbit of Mercury, which being the closest planet to the Sun, moves the fastest, and GPS navigation, which relies on extreme accuracy of the orbits of the satellites, and the effect of gravity on their signals, to determine user position. Isaac Newton formulated many of the basic ideas of classical mechanics in his Principia, published in 1687. These include his three laws of motion, conservation of momentum and angular momentum, and the law of universal gravitation.

 5.1 - Newton's Three Laws

 These are laws in the mathematical sense, which Newton deduced from experiments performed by others before him. They involve two opposing concepts: Forces which tend to create motion, and Mass which tends to oppose changes by the property of Inertia. The relationship of forces to the motion they create is the field of Dynamics.

 Forces are vectors, having an amount and a direction, and multiple forces act as the vector sum of the component forces. This also means single forces can be decomposed mathematically into components, such as vertical and horizontal components relative to an axis system, or perpendicular (normal) and parallel components relative to a surface. Decomposition is done when it is useful in solving a problem.

 The three laws are:

 First: Inertia - A body acted on by no net force moves with constant velocity (which may be zero) and zero acceleration:

 * $$\sum \vec F_i = 0 \Rightarrow a = 0$$

 Where the Greek letter Sigma (Σ) means "sum of" and and the right double arrow ⇒ means "implies", the formula reads "The vector sum of forces i, where i = 1 to n, adding up to zero implies the acceleration is also zero. Common experience on Earth is that moving objects decelerate to a stop.  This is because hidden friction forces act to stop them.  Objects moving freely in the vacuum of space demonstrate this Law more clearly because friction is nearly absent.

 An airplane in level flight has multiple forces acting on it (gravity, lift, thrust, and drag), but if the vector sum of all the forces is zero, it will continue moving at the same altitude and velocity in the same direction. From the fact that buildings are not typically accelerating we can deduce there is no net force acting on them, or the sum of the forces is zero. Since gravity acts to pull the building down, there must be an equal force from the ground acting to hold it up. Applying this idea to every structural part of a building is a powerful way to determine the necessary design of each - at each point where components connect, the forces must sum to zero, therefore you can calculate the forces which a particular component must withstand.

 Second: Force - When a net force does act on a body of mass m, the acceleration a is related to the magnitude of the force F by the formula

 * $$ \vec F = m \vec a $$

 The force and acceleration are vectors, so a force in a given direction produces an acceleration in the same direction. Manipulating this simple formula has many uses in space systems. Given any two of the values, we can find the third. Summing across time, we can find total velocity change. Mass has units of kilograms and acceleration has units of meters per second squared. So by the above formula force has units of kilogram-meters per second squared (Newtons in SI units). The force which the Earth exerts on a medium apple is coincidentally, given stories about Newton and falling apples, about 1 N.

 The product of mass times velocity is called Momentum. It is given the symbol p since mass already uses the letter m. Force also equals the change of momentum per time interval. Acceleration is the change in velocity per time so the following formula just adds the multiplier of mass to both sides of the equation:

 * $$ \vec F = \frac{d \vec p}{dt} $$.

 Third: Reaction - Single forces do not act in isolation. At the most fundamental level the particles which carry the four forces of nature act on both the emitter and absorber of the particles. At the macroscopic level we live in forces are the combined action of many particles. So we observe the dual action as "for every force there is an equal and opposite reaction force". Where the subscripts ab and ba indicate the force of object a on object b and object b on object a, and the minus sign indicates the second force is in the opposite direction:

 * $$\vec{F}_{\mathrm ab} = - \vec{F}_{\mathrm ba}$$

 An object can never move itself by applying forces only to itself, because the reaction force would cancel it out. You cannot hold yourself above the ground, no matter how hard you try, by applying forces to your own body. A pole vaulter, however, can raise their body a considerable distance by applying force to the ground. The reaction force of the ground through the pole then acts to raise their body. Of great interest for space systems is that expanding gases in a rocket engine apply a great deal of force to to the engine, and thus the rest of the rocket, while accelerating themselves to high velocity in the other direction.

 Multiplying both sides of the above formula by units of time, and subtracting the left side from the right side, we find that sum of momentum changes (mass times velocity) is always zero. This is known as the Law of Conservation of Momentum. It is referred to as a physical law because it has never been observed to be violated. Conservation in the physics sense means a value which does not change.

 Momentum is found to be conserved both for linear and rotational motion. The latter is referred to as Angular Momentum. So the Earth would continue to rotate forever unless acted on by outside forces. Such forces do in fact act, mainly tidal forces from the Moon. So the Earth's Rotation is slowing down measurably - the day is getting longer by a small amount each year on average. But since angular momentum is conserved, slowing the Earth's rotation means the Moon increases its orbital angular momentum. This increases the size of its orbit by a measurable amount (3.8 cm/year)

 5.2 - The Forces of Nature

 There are only four fundamental forces that we know of, responsible for all relative motion in the Universe. These are the gravitational, electromagnetic, weak nuclear, and strong nuclear forces. These forces act by their carriers, called gravitons, photons, W and Z bosons, and gluons respectively. For more detail see Fundamental Interaction. The latter two are short range forces which mostly occur within atomic nuclei, so the two that concern space projects the most are gravity and electromagnetism.

 5.2.1 - Gravity

 Gravitons are the hypothetical particles which should carry the gravitational force. They are hypothetical because they have not yet been observed. Because gravitons never decay, their range is infinite, and the Gravitational Field of any object in the Universe affects every other object in the Universe. In practice, Gravity is most accurately described by General Relativity which treats gravity as a geometric property of four-dimensional Spacetime. That theory is complicated, but for most engineering purposes we can use the simpler "Classical" formulas based on Newton's work.

 The total gravitational field surrounding an object remains the same at any distance. The area of a sphere surrounding an object is $4πr^{2}$, where π is the mathematical constant Pi and r is the radius. So the gravitational field per unit area decreases with the square of the radius. Between any two objects the total gravitational force F depends on the product of the two masses. The first object produces a field and each part of the second object is affected by it. The second object has the same effect on the first. Where M is the mass of the first object, m is the mass of the second, and G is a universal constant which applies to every object in the Universe (as far as we know):

 * $$G = 6.67 \times 10^{-11} Nm^2/kg^2$$

 * $$ F = -\frac{GMm}{r^2} $$

 Gravity always acts to attract two objects to each other, in other words reduce the distance, so the force is given a negative value. As a practical matter, since the field falls as the square of distance, objects sufficiently far away can be ignored to the extent you need to accurately calculate the total gravitational force on an object. The force acts on a line between each pair of objects and the total force is simply the sum of the individual forces accounting for the direction of each, and each is found by the above formula.

 Since force is also mass times acceleration, we can equate them and remove mass m from both sides of the equation, giving the acceleration a due to gravity of an object with mass M as

 * $$ \vec a = -\frac{GM}{r^2} $$

 The force of gravity on an object is referred to as Weight. Most people live where gravity is within 2% of the standard value, so we often confuse weight with mass. They are proportional, but they have different units. Your mass does not change according to what object you are standing on. The acceleration of gravity does due to the object's different mass and radius. So on another planet or body, you would have a different weight.

 Weight does not disappear when in orbit. Aboard a low orbit space station the force of the Earth's gravity is only 11% less than on the ground. So-called "zero gravity" is more properly described as Free Fall. The astronauts inside the Station and the Station itself are both affected by the same acceleration of gravity. So the difference between them is zero, and the astronauts do not feel their bodies pressed against anything. On Earth what you feel is parts of your body pressed against the ground or furniture, and internally pulling parts of your body down. This pressure is what you experience as "weight".

 Since the range of gravity is infinite, there is nowhere in the Universe that is truly zero gravity. There are places where the forces are balanced, and you are so far away from any massive body that your acceleration can be ignored for most, but not all purposes. Despite being 2.5 million Light Years apart, our own Milky Way Galaxy and the Andromeda Galaxy are still pulling on each other and will Collide in about 4.5 billion years. But for space systems engineering within our Solar System we can ignore anything beyond it most of the time.

 5.2.2 - Electromagnetism

 Photons are the particles which carry the electromagnetic force. Unlike gravitons, they are easily observed whenever your eyes are open, since photons are what make up Light. They also do not decay as they travel, and obey an inverse square law of intensity with distance. In a vacuum, they travel at the Speed of Light, one of the constants of nature, because they are light.

 Where gravity is the result of mass, electromagnetic force is the result of electric charge. Unlike gravity, charge comes in two types which we call positive and negative. The names are arbitrary, but Electrons have one unit of negative charge. Positive charges are the same size, and the Proton has one unit. Like electric charges repel each other, and unlike charges attract. So protons attract electrons to produce neutral Atoms. The electromagnetic force F is

 * $$F = k_\mathrm{e} \frac{q_1q_2}{r^2}$$

where k(e) is the Coulomb Constant, q1 and q2 are two Electric Charges in units of Coulombs (symbol C), and r is the distance between them. Note the form of this equation is similar to the one for gravitational force. When both of the charges are positive, or both negative, their product is positive, and so is the force. Positive forces act to increase the distance between charges. When the charges are unlike, one positive and one negative, the product is negative, and the force acts to decrease distance. The Coulomb constant is:

 * $$k_\mathrm{e} = 8.987552 \times 10^9 \ \mathrm{N \cdot m^2 / C^{2}} $$

 Electric charges are almost always observed as integer multiples of the electron and proton charges. The exception are Quarks which combine to form particles like protons. These are never observed in isolation, so they can be ignored for space systems work. Charges are additive by simple arithmetic, with negative charges canceling the fields of positive charges.

 Since unlike charges attract each other, they tend to annihilate (convert to pure energy) if they are antiparticles, or form neutral atoms if they are protons within atomic nuclei and electrons. So large quantities of matter tend to have low net charge. Since mass is always positive, large quantities of matter will have large amounts of gravity. Despite gravity being a much weaker force on an individual basis, it tends to dominate the actions of large bodies.

 Moving electric charges create a Magnetic Field. This includes the imputed spin of the charges of elementary particles. Materials with aligned atomic spins then have a static magnetic field. A steady flow of electric charges is called an Electric Current, and also creates a magnetic field. Magnetic fields in turn affect the motion of electric charges, creating a force F, where I is the current, ℓ is the length of the wire, and B is the strength of the magnetic field in units of tesla (symbol: T).

 * $$\mathbf{F} = I \boldsymbol{\ell} \times \mathbf{B} \,\!$$

 The bold face symbols indicate these are vector values, having directions. The force is perpendicular to both the direction of the wire/current and the magnetic field. Natural magnetic fields, such as the Earth's, are assumed to be caused by electric currents within the body.


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Space Transport and Engineering Methods/Combustion Engines

A. Air-Breathing Engines
The next group of methods normally involve using a planet's (usually the Earth's) atmosphere as a supply of oxygen to support combustion with a fuel carried on the vehicle. They differ in the details of how the incoming air flow and combustion is managed. It should be noted that some vehicle concepts, such as the National Aerospaceplane (NASP) of the 1990's, or the current British Skylon would integrate more than one method in a single engine. This is referred to as a Combined Cycle Engine. The same general engine concepts could be used in a reducing atmosphere, such as Hydrogen or Methane, with Oxygen as the carried fuel, or in a sufficiently powerful nuclear engine with any atmosphere. In the latter case the nuclear engine is used to drive a compressor or heat the incoming gas flow.

Fundamental to understanding the operation of air-breathing engines is the concept of mass conservation. The mass of incoming air at the Inlet does not change in total amount going through the engine, although pressure and temperature vary. The exception is the point where fuel is added, or in some types, where condensed air flow is removed. Heat can be added or removed by combustion or heat exchangers, but otherwise the mass flow stays the same. From that constant mass flow, changes in the other conditions of the gas flow can be calculated, and performance derived.

In practice, the flow through an engine can involve many fan blades and turbulence, so that computer simulations are not fully accurate. Real engines also operate at extremes of temperature and stress. Therefore engine development typically includes extensive testing on static test stands, in wind tunnels, and in flight attached to aircraft, to determine actual performance and durability.

25 Fanjet
Alternate Names:

Type: Gas Flow by Fuel-Atmosphere Combustion

Description: The fanjet is the standard type of jet engine found on passenger aircraft and military aircraft. The original form of the engine, the turbojet, has a series of turbine compressor stages to compress the incoming air flow. This is followed by a combustor where fuel is added and burned, creating a hot gas. The gas is then expanded through a turbine which is connected by a shaft to the compressor. The expanded gas emerges at high velocity from the back of the engine.

The modern fanjet adds a fan which is also driven by the turbine. All of the airflow goes through the fan, but only a part goes into the compressor. The air which does not go into the compressor is said to have 'bypassed' the compressor. The 'bypass ratio' is the ratio of bypass air to combustor air. Generally higher bypass ratio engines are more fuel efficient, in units of thrust divided by fuel consumption rate, because they increase the mass flowing through the engine. In general, engines that operate at higher speeds are designed with lower bypass ratios. This is due to more combustion needed to increase thrust against the higher inlet drag from the higher velocity.

Typical modern performance values are engine thrust-to weight ratios (T/W) of 6:1 for large subsonic engines, trending towards about 10:1 for high performance military jets. Fuel efficiency is measured in units of thrust divided by mass flow rate. In English units this is pounds divided by pounds per second, or just seconds, and is termed 'specific impulse'. In SI units this is Newtons per kilogram per second, which has the units of meters per second. In some propulsion systems, such as chemical rockets, the SI unit corresponds to the actual exhaust jet velocity. In the case of air- breathing propulsion it is not, the velocity result is just an indicator of engine efficiency. In English units the performance of subsonic engines is about 10,000 seconds, trending to about 7000 seconds for supersonic military engines. Fanjets and turbojets operate up to about 3.5 times the speed of sound (M=3.5). Extra thrust can be generated with an Afterburner, which burns more fuel after the turbine stage of the engine. This comes at the cost of lower fuel efficiency.

Although the maximum altitude and velocity of a fanjet is limited compared to Earth orbit velocity, the effect on payload can be much larger. This is because compared to a conventional rocket, it can avoid most of the drag, pressure, and gravity losses near the ground. Conventional rocket payload is typically a small fraction of total mass, so small reductions in losses can produce large relative increases in payload.

Status: In common use on aircraft for aircraft propulsion. For space launch, the B-52 bomber and L-1011 aircraft have been used to carry the Pegasus three stage solid rocket to 35,000 ft altitude. The B-52 uses 8 fanjet type engines for propulsion. The Stratolaunch system is under development, using parts from two 747 aircraft with 6 high bypass fanjet engines, and carrying a large rocket. Numerous paper studies have been made of using aircraft as carriers for rocket stages.

Variations:

 * Carrier Aircraft - A conventional jet aircraft is used to carry a separate rocket to an altitude of roughly 9000 meters and velocity of 240 m/s, after which the rocket ignites and finishes reaching orbit.

 * Booster Jets - A set of military fighter engines are attached to a rocket as separate strap-on boosters, or a connected booster ring. They can loft a rocket to about 15 km altitude and 480 m/s velocity, after which they either parachute land or do a powered vertical landing.

References:

26 Turbo-Ramjet
Alternate Names:

Type: Gas Flow by Fuel-Atmosphere Combustion

Description: In this method a multi-stage fan compresses the incoming air stream, which is then mixed with fuel, burned and exhausted. The compressor is driven by a gas generator/turbine. In a fanjet, the incoming air is compressed and heated by the compressor stages, then mixed with fuel and run through the turbine stages. At higher velocities the air gets hotter in compression since it has a higher incoming kinetic energy. This leads to a higher turbine temperature. Eventually a turbine temperature limit is reached based on the material used, which sets a limit to the speed of the engine. In the turbo-ramjet the compressor is driven by a gas generator/turbine set instead, which use on-board propellant for their operation. Since the gas generator is independent of the flight speed, it can operate over a wider range of Mach numbers than the fanjet ( to Mach 6 vs. to Mach 3).

Status:

Variations:

References:

27 Ramjet
Alternate Names:

Type:

Description: In this method, the incoming air stream is decelerated to subsonic velocity relative to the engine via a shaped inlet, mixed with fuel, then accelerated again out an exit nozzle. Conceptually it is the simplest form of jet engine, because it has no fans or turbines. The incoming air is moving at the vehicle velocity entering the engine. After burning the fuel, the air is hotter and can expand to a higher velocity out the nozzle. This sets up a pressure difference that leaves a net thrust. Ramjets cannot operate at zero speed, but they can reach somewhat higher limits than an engine with rotating machinery (range Mach 0.5 to about Mach 8).

Status:

Variations:

 * Air Augmented Rocket - This is a form of combined cycle engine. Since ramjets do not function at zero speed, an internal rocket chamber in the engine is used for initial thrust.  By entraining air flow, the thrust level can be augmented at lower speeds.  Once ramjet speeds are reached, the engine functions in ramjet mode, using the rocket chamber as a fuel injector.  At the upper end of ramjet function, the engine transitions back to pure rocket mode.

References:

 * Wikipedia article: Air-augmented Rocket

28 Scramjet
Alternate Names:

Type:

Description: This is similar to how a ramjet functions. The incoming air stream is compressed by shock waves, mixed with fuel, and expanded against the engine or vehicle body. The difference is the airstream remains supersonic relative to the vehicle. The ramjet requirement to slow the airstream to subsonic speed becomes inefficient at higher velocities. Even though the gas is moving supersonically relative to the vehicle, the sidewise expansion can act on the vehicle if the slope of the nozzle is low enough. Thus the vehicle can fly faster than the exhaust gas moves. Scramjets may provide useful thrust up to about Mach 15, or 60% of Earth orbital speed.

The very high velocities lead to extreme heating of vehicle parts. High compression and expansion efficiency is needed to get a positive net thrust, since the energy added by the fuel becomes small relative to the kinetic energy of the air flow. Thus development of working scramjets has proved difficult. Scramjets also do not function at zero velocity, so some other method is needed to get to their starting point. Therefore complete vehicles will need a combined engine system.

Status: Scramjet engine components and small scale versions have been tested with mixed success.

Variations:

References:

29 Inverted Scramjet
Alternate Names: Buoyant Scramjet

Type:

Description: Ramjet and scramjet vehicles would prefer Hydrogen as a fuel because it gives higher performance, and can be used for cooling vehicle parts heated by the high velocity in air. Unfortunately Hydrogen is also very low density, which leads to relatively heavy vehicle structure due to large tanks. This method inverts the problem by using a series of balloons or a lightweight pipe supported in the atmosphere. They contain Hydrogen, and the vehicle carries Oxygen in its tanks. Oxygen is about 16 times denser than Hydrogen, so the tank size is much reduced.

Status: This is only a concept at present.

Variations:

References:

30 Laser-Thermal Jet
Alternate Names:

Type:

Description: In this method a laser beam is focused on and absorbed by a heat exchanger on the vehicle, or creates a laser-sustained plasma. The hot gas is then exhausted for thrust. By not requiring fuel, it is potentially efficient. The drawback is it requires a very powerful laser to be feasible even for small vehicles. Powerful lasers are currently expensive. Another limitation is the distance over which the beam can maintain focus.

Status: Minimal experiments have been done in a laboratory.

Variations:

References:

 * Myrabo, L. N. "Concept for Light-Powered Flight", AIAA paper number 82-1214 presented at AIAA/SAE/ASME 18th Joint Propulsion Conference, Cleveland, Ohio, 21-23 June 1982.

B. Internally Fueled Engines (Rockets)
Conventional rockets function by expelling a gas at high velocity in a desired direction. By conservation of momentum (a physical law), the remainder of the vehicle will gain velocity in the opposite direction. Rockets have been the principal method of space transport to date because they only require internally stored fuel, and can thus operate in a vacuum. Since they propel the vehicle, the fuels are also called Propellants. Rockets can be sorted into types by how many propellants they have and what physical form the propellants are stored in. The former category includes single fuel Monopropellant, two fuel Bipropellant, and the rarely used three fuel Tripropellant types. The category includes gaseous, solid, liquid, and hybrid - part solid and part liquid.

Thrust is mass flow rate times exit or Exhaust Velocity. To get the most use from a finite amount of fuel, you want to minimize flow rate and maximize exit velocity. Therefore the gas should be as hot as possible and have low molecular weight. That in turn drives the choice of chemical reaction and fuels to use. There are numerous fuel combinations that are possible, but a relatively few that have a combination of high energy and other desirable characteristics such as density, safety, and low corrosion. There are several ways to get the gas hot: catalytic decomposition, combustion, or external heating. The first two are grouped under chemical rockets, and the latter are categorized by how the gas gets heated. Chemical rockets generally use a combination of combustion chamber and expansion nozzle, as that is a very efficient way to direct the gas flow at high velocity. Rocket engines will function with a surrounding atmosphere, but that impedes the gas flow, so they generate lower thrust. The lost thrust can be approximated by the local exterior pressure times the area of the nozzle exit.

Rockets are generally less efficient than air-breathing engines in terms of momentum per fuel mass, since the latter can use oxygen from the air as part of the fuel. This increases the combustion energy per carried fuel mass. Air breathing engines also increase the mass flowing through the engine via the Nitrogen component of air, and additional un-combusted air flow using engine-driven fans. Both rockets and air-breathing engines involve similar design principles, as they both use combustion and hot gas flow to get reaction forces.

History - The earliest reference to using expelled mass for reaction force is the Greek Archytus around 400 BC. This used external heating to generate steam. The first known use of internal chemical energy is in 1232 AD in China by fire arrows using gunpowder as fuel. The idea may have been transmitted to Europe by the Mongols, where experiments and use for fireworks occurred in the 13-15th centuries. Experiments began in the 18th century as a transport method rather than explosive device, although military use continued. Notably, rockets used in a battle in 1812 were recorded in the US national anthem.

The use of rockets to reach space was proposed by Konstantin Tsiolkovsky in 1898. Robert Goddard built experimental solid and liquid fuel rockets starting in 1915. A book published by Hermann Oberth in 1923 influenced the formation of rocket societies where groups pursued their development. The German government pursued the development of rockets to deliver explosives by sub-orbital trajectories from 1937 to 1945. Subsequently the scientists and their hardware and data went to the United States and the USSR, where they helped develop sub-orbital ballistic missiles and orbital transport, both first flying in 1957. The first orbital rockets were essentially identical to ballistic missiles, but have since diverged. By 1963 Liquid Hydrogen/Liquid Oxygen propellants were in use, which is still the highest energy fuel mix commonly used. Liquid and solid chemical rockets are by far the most common space transport method, and are now built in a number of countries by both governments and private companies.

Design - The non-fuel mass of a rocket stage can be grouped into engines, tanks, and "other". Rocket engines can produce 400-1000 N/kg of engine mass in thrust, which is many times larger than the 9.8 N/kg force of gravity. For liftoff from the Earth, you want approximately 1.2-1.5 times the vehicle takeoff weight in thrust, so the engine component then has a mass of about 1.3-3% of the total vehicle. A large tank, such as the Shuttle External Tank, can weigh 4% of the fuel weight, but other tanks can range up to 10% of the fuel weight. 'Other' includes plumbing, parachutes, landing gear, heat shields, guidance systems, and such non-propulsion parts. It can range from 1% up to 10% of the total weight.

Older materials and components required 15% of the total liftoff mass to be vehicle other than fuel, assuming a single flight operating life. Modern materials require about 10% of the total mass for a many flight operating life. Structures tend to get heavier at the rate of 10% for each factor of 10 in life. This comes from the fatigue life of materials under load cycles (flights) as a function of stress. Lower stress and longer life requires thicker and heavier structural parts to distribute the load over. So a 100-use structure will be about 20% heavier than a one-use structure.

31 Solid Rocket
Alternate Names:

Type:

Description: A solid rocket consists of a high-strength casing, a nozzle, and a precast solid propellant grain which burns at a pre-designed rate. The grain is a mixture of materials containing both fuel and oxidizer, so combustion can proceed without any external action once it is ignited. Modern solid propellants have a formulation close to the following: About 15% by weight organic fuel, usually a type of rubber, about 20% by weight aluminum powder (which acts as a metallic fuel), and about 65% ammonium perchlorate (NH3ClO4), which is the oxidizer. About 1-2% epoxy is added to the powders to hold them together. The epoxy, being an organic material, is also part of the fuel. Solid propellants burn from the surface of the precast grain. Therefore the shape of the grain at ignition, and shape as it burns away, determines the thrust level.

Advantages of solid rockets are short preparation time to launch and long term storage, compared to cryogenic fuels like liquid Oxygen. Disadvantages include relatively low exhaust velocity (2.6-3 km/s), and no easy way to turn it off or control it once ignited. They are often used as a booster first stage since the relatively dense fuel (1.35 g/cc) lowers the area of the vehicle. This is an advantage during the first two minutes of flight, where aerodynamic drag is important. When aluminum is used in the propellant, part of the end product is aluminum oxide, which is an excellent abrasive. Thus nozzle erosion is a significant effect that must be accounted for, in addition to the high temperatures.

Solid rockets are simpler in the sense of having few moving parts, but the entire motor casing that surrounds the fuel grain must withstand the operating pressure. In liquid rockets with fuel pumps, the propellant tanks see hydraulic and acceleration loads, which are typically lower, and only the pumps and combustion chamber see the full operating pressure.

Status: In common use for rocket stages, particularly the strap-on booster stage.

Variations:

References:

32 Hybrid Rocket
Alternate Names:

Type:

Description: The hybrid rocket consists of a solid fuel grain and a liquid oxidizer. One combination is rubber for the fuel and liquid oxygen for the oxidizer. The fuel is in the form of a hollow cylinder or perforated block. The oxidizer is sprayed onto the fuel and the material is ignited. By not being self-supporting in combustion, the fuel part can be treated as non- hazardous when being made and shipped. Only when on the launch pad and the oxidizer tank is filled is there a hazardous combination. With only a single liquid to handle, the hardware is relatively simple in design. Hybrid rockets are intermediate in performance compared to solid and full liquid engines.

Status:

Variations:

References:

33 Liquid Rocket

Alternate Names:

Type: Fuel/Oxidizer Combustion by Combustion Gas exhaust

Description: In a liquid rocket, the propellant ingredients are forced into a combustion chamber, where they burn, and which leads to a converging-diverging nozzle. The flow becomes sonic at the narrow part of the nozzle, then continues to accelerate in the diverging part of the nozzle, reaching about 1.5-2 times the speed of sound by converting temperature and pressure via expansion into a directed flow. A variety of propellant combinations have been used, including mono- bi-, and even tri-propellants. Monopropellants typically use catalytic decomposition for heating. The most common form of liquid rocket uses a separate fuel and oxidizer, which are mixed and burned in the combustion chamber. Many bipropellant mixtures are possible, but the highest energy-to-mass ratio mix in common use is from 1 part Hydrogen to 6 parts Oxygen. This produces mostly steam with a little leftover Hydrogen, which lowers the average molecular weight and thus increases the average molecule velocity. This propellant mix can reach about 4.7 km/s exhaust velocity under the best conditions.

Some propellant mixes will burn on contact, and so do not require an ignition source. These are called Hypergolic propellants. Some liquid propellants are liquid at room temperature and can be stored for long periods in a tank. These are referred to as Storable. Others, including Hydrogen, Methane, and Oxygen, are only liquid at very low temperatures. These are referred to as Cryogenic.

Status: This is the most common form of launch propulsion used to date to put things into Earth orbit.

Variations: There are multiple combinations of liquid engine types that are possible and have been used. They can be sorted by what propellant combination is used, how the propellants are delivered into the combustion chamber, and how the resulting hot gas is expanded out of it.

 * Variations by composition - The following tables list some oxidizers and fuels, and combinations thereof. It is not an exhaustive list, and some ingredients have practical issues such as storage temperature, human toxicity, corrosiveness, or chemical instability.  Rocket propellants by their nature contain a lot of chemical energy, and that energy can cause unintended reactions.  Actual engine performance depends on factors such as chamber and exit pressures, so the table values should only be used for general comparisons. Kerosine is a mixture of compounds derived from petroleum, and Rocket Propellant 1 (RP-1) is a standardized type of Kerosine specified as a rocket fuel.  Therefore it does not have an exact formula, and it is given as an approximate average value.  It also does not have a well defined melting and boiling point, which is given as a range defined by distillation of its components.

Oxidizers

Fuels

Propellant Combinations

Exhaust Velocities assume chamber pressure of 6.9 MPa and exit pressure of 0.1 MPa (Earth sea level) with optimum nozzle expansion.

 * Variations by fuel feed - Some engine designs use a pump to feed the propellants into the combustion chamber, others use a pressurized tank. Large engines may use a combination of tank pressurization to prevent cavitation of the pump inlet and pumps to reach chamber inlet pressure.  The fuel must enter the chamber at a higher pressure than the combustion pressure in a steady state engine.  Non-steady state pulsed ignition engines are possible, but not generally used.  Steady state engined deliver more continuous thrust. Pumps require a lot of power to operate, and generally use the same fuel as the rocket.  In Gas Generator systems a portion of the fuel flow is used to create hot gas which drives a turbine to run the pump.  The hot gas is then vented.  In Staged Combustion systems, the hot gas is not completely burned, and is fed into the combustion chamber.  This is more efficient but also more complex.

 * Variation by nozzle type - Most rocket engines to date use a bell-shaped nozzle, where the gas flow is on the inside, surrounded by structure which directs the flow. An alternate design called an Aerospike nozzle inverts this arrangement, with the structure on the inside in the form of a wedge or cone, and the gas flow surrounding it.  The outer edge of the gas flow is contained by the surrounding atmosphere.  Since that automatically adjust for pressure differences, it is a type of altitude compensating nozzle. The benefit to compensation is that nozzle exit area in an atmosphere represents a thrust loss.  A truncated cone can integrate better with some vehicle shapes, and the larger chamber and nozzle area can lower heat flux.

 * Variation by cooling type - The high energy combustion in liquid rocket engines can exceed the melting point of most structural materials. Therefore methods to prevent this are needed in all but the smallest engines, which simply use high temperature alloys and radiate the heat away.   In one method, the fuel is run through channels in the rocket engine walls to keep it from overheating.  This also recovers some of the energy that would otherwise be lost. A method in recent development by Orbitec injects a counterflow vortex of one propellant ingredient along the inside of the engine walls, which is mixed with the other ingredient at the back and the hot gases then flow in the forward direction down the core of the chamber.  The unburned ingredient protects the structure with a layer of cool gas.

References:

 * Cooper, Larry P. "Status of Advanced Orbital Transfer Propulsion", Space Technology (Oxford), v 7 no 3 pp 205-16, 1987.
 * Godai, Tomifumi "H-II Rocket: New Japanese Launch VehicleÊ in the 1990s", Endeavour, v 11 no 3 pp 116-21, 1987.
 * Wilhite, A. W. "Advanced Rocket Propulsion Technology Assessment for Future Space Transportation", Journal of Spacecraft and Rockets, v 19 no 4 pp 314-19, 1982.

34 Gaseous Thruster
Alternate Names:

Type:

Description: In this method the propellant is introduced in gas form to the chamber. It may be a mono-propellant (a single gas) or a bi-propellant combination. Due to high tank mass this is usually used for small auxiliary thrusters. By using direct pressure from the tank to make the propellant flow, it can be very simple.

Status:

Variations:

References:

35 Mechanically Augmented Thruster
Alternate Names:

Type:

Description: The velocity of the exhaust gases are increased by placing the thrusters on the end of rotating arms. This can add 2-3 km/s to the exhaust velocity based on structural limits. It requires some external energy input to maintain the rotation of the arms, since the thrust opposes their rotation. Full electric thrusters generally have higher performance than this method, so they are preferred.

Status: Concept only, since there are better options.

Variations:

References: