rocket

All About Rocket Engines

Return to contents Previous Section Next Section There are essentially two different types of commercial model rocket engines, black powder and composite. One new type of engine uses a combination of liquid nitro (racing car stuff) and cellulose as the rocket fuel. This combination engine is being designed to overcome the problems with shipping larger engines containing flamable fuel. Black Powder Engines The most commonly used small model rocket engines are the black powder engines such as the one shown below. These are the "traditional" model rocket engines that have been in production since the 50's. Black powder model rocket engines are made of a paper tube with a clay nozzle, a solid pellet of black powder propellant, a smoke/delay charge, and an ejection charge as shown in this figure. Cut-away design of a model rocket engine. Booster engines are similar but lack the Smoke/Delay and ejection charge. A model rocket engine is ignited by inserting an igniter in the clay nozzle putting it in contact with the propellant. At launch, an electric current is driven through the igniter, causing it so explode, igniting the propellant. An engine with an igniter inserted in the engine nozzle. When the engine is ignited, the propellant burns, ejecting high-pressure gas out of the nozzle and producing thrust in the opposite direction. Thrust comes from burning the propellant. When the propellant is completely consumed, the smoke/timer charge burns producing a smoke trail. The timer charge performs two tasks. First, it provides a smoke trail to help you follow the flight. Second, it lets the rocket coast to its maximum height before activating the ejection charge. A smoke/delay charge burns after the propellant is consumed. When the smoke/timer charge is exhausted, the ejection charge fires, which pressurizes the rocket body and deploys a parachute or other recovery device. When the burn reaches the ejection charge, a small explosion deploys the recovery system. Return to contents. Composite Engines Composite model rocket engines are made from a high temperature plastic and the fuel is a pellet of a rubber like material similar to that used in the Space Shuttle booster engines. The fuel in a composite engine is about three times as powerful as black powder so engines of equivalent power can be made in a smaller size. A typical composite motor. The internals of the composite engines are much the same as the black powder motors except that the nozzle and body of the engine is molded from a high-temperature plastic. The engine body contains the fuel, a smoke/timer charge, and the ejection charge. Return to contents. Understanding Model Rocket Motor Codes Model rocket engines are marked with a three character code that specifies the approximate operating characteristics of the motor. The code consists of a letter and two numbers such as D12-5. A D12-5 model rocket motor. The letter is the total impulse, the first number is the average thrust in Newtons, and the second number is the time delay in seconds to the initiation of the recovery system. Hence, the motor in the figure is a class D total impulse engine with an average thrust of 12 Newtons and a time delay of 5 seconds. Return to contents. Total Impulse The letter indicates the total impulse class of the engine, which is effectively the amount of fuel in the engine. The total impulse is the total momentum change that an engine can impart to a rocket. Total impulse is measured in Newton-seconds (pound-seconds). The standard impulse class for each letter is shown in the following table. Class Total Impulse Newton-sec 1/4A 0.000 - 0.625 1/2A 0.626 - 1.25 A 1.260 - 2.50 B 2.510 - 5.00 C 5.010 - 10.0 D 10.01 - 20.0 E 20.01 - 40.0 F 40.01 - 80.0 G 80.01 - 160.0 H 160.01 - 320.0 Most commercial model rocket engines are built to operate at the top impulse level of their class, but this is not a requirement. An engine may actually operate anywhere in its impulse class range. Note: each engine class is double the impulse of the class below it, so as you increase the class of an engine, you effectively double the amount of fuel each contains and double the amount of momentum it can impart to a rocket. Return to contents. Average Thrust The number following the letter indicates the average thrust of the engine in Newtons (pounds). Because the amount of fuel in an engine is fixed by the class letter, an engine with higher average thrust burns up its fuel more quickly than one with lower average thrust. As a rule of thumb, the duration of a burn is roughly equal to the total impulse divided by the average thrust. Here is a typical thrust profile for an engine with an average thrust of about 6 Newtons. Typical engine thrust profile. A typical engine starts with an initial high thrust for a fraction of a second, which is useful for getting things moving. It then settles down and burns the remainder of the propellant at a relatively constant rate. Return to contents. Time Delay The last number on an engine is the time delay, in seconds, to activation of the recovery system. The propellant in a model rocket typically burns up in about 1 second. At that point, the rocket is still moving upward at a high rate of speed. If you were to activate the parachute at this point it would likely be shreaded. What you want to do is to let the rocket coast up to its highest point and then activate the parachute. The time delay charge is the mechanism for delaying activation of the recovery system until the rocket reaches its highest point. The time delay charge also emits smoke to make the rocket easier to track. When the smoke charge burns out, it ignites an ejection charge that activates the recovery system. Note: Some larger models use altimeters to sense when a rocket is at its highest point and electrically fire the ejection charge. The Engine's ejection charge also fires a little bit later as a backup to the altimeter. Time delays are typically 3 to 8 seconds, with short time delays needed for larger heavier rockets and longer delays needed for lighter ones. Do not use too long of a time delay as it may allow your rocket to impact the ground before activating the recovery system. Such impacts endanger the spectators and are really hard on your rockets. Rocket motors marked with a time delay of 0 seconds are booster engines. A booster engine is used in the lower stages of a multi-stage rocket and has no time delay and no ejection charge. When the fuel finishes burning there is a flash of flame out the back of the engine that is used to light the next engine in a multi-staged rocket. Only the top stage in a multi-staged rocket needs an engine with a time delay and an ejection charge. Rocket motors marked with a P instead of a number for the delay charge are "plugged" engines. A plugged engine is similar to a booster but the forward end is plugged so no fire comes out the front when the fuel finishes burning. These are used in some gliders and in situations where you do not want a blast out the front. Return to contents. Engine Sizes Model rocket engines come in several standard sizes so that whenever possible, engines of different total impulse and from different manufacturers may be used in the same rocket. The more common engine sizes are in gray. Size Available Impulse Classes Diameter mm (in) Length mm (in) 10.5 x 38 1/4A, 1/2A 10.5 (0.41) 38 (1.50) 10.5 x 47 A 10.5 (0.41) 47 (1.85) 10.5 x 89 B 10.5 (0.41) 89 (3.50) 13 x 45 (T mini engines) 1/2A, A 13 (0.5) 45 (1.75) 13 x 50 B 13 (0.5) 50 (1.97) 18 x 50 C 18 (0.69) 50 (1.97) 18 x 70 Standard A, B, C, D, E 18 (0.69) 70 (2.75) 18 x 77 D 18 (0.69) 77 (3.03) 21 x 95 D, E 21 (0.83) 95 (3.74) 24 x 101 F 24 (0.94) 101 (3.98) 24 x 124 F 24 (0.94) 124 (4.88) 24 x 144 G 24 (0.94) 144 (5.67) 24 x 177 G 24 (0.94) 177 (6.97) 24 x 70 D, E, F 24 (0.94) 70 (2.75) 24 x 89 E 24 (0.94) 89 (3.50) 27 x 114 E 27 (1.06) 114 (4.49) 27 x 152 F 27 (1.06) 152 (5.98) 29 x 124 E, F, G 29 (1.14) 124 (4.88) 29 x 152 F 29 (1.14) 152 (5.98) 29 x 206 G 29 (1.14) 206 (8.11) 29 x 238 H 29 (1.14) 238 (9.37) 29 x 291 H 29 (1.14) 291 (11.46) 29 x 85 F 29 (1.14) 85 (3.35) 29 x 95 F 29 (1.14) 95 (3.74) 29 x 98 F 29 (1.14) 98 (3.86) 32 x 107 F, G 32 (1.26) 107 (4.21) 38 x 250 I 38 (1.50) 250 (9.84) 38 x 258 I 38 (1.50) 258 (10.16) 38 x 314 I 38 (1.50) 314 (12.36) 38 x 370 I 38 (1.50) 370 (14.56) 54 x 250 I 54 (2.13) 250 (9.84) 54 x 326 J 54 (2.13) 326 (12.83) 54 x 403 K 54 (2.13) 403 (15.87) Return to contents. NAR Certified Engines In California, only engines certified by the National Association of Rocketry (NAR) can be flown. They must also be certified by the State of California but NAR certification is needed first. The current list of certified engines is available on the NAR website. List of NAR certified engines Return to contents. Reloadable Engines Aerotech and Kodson, in an attempt to reduce the cost of a launch have instituted a line of reloadable rocket motors. The motors consist of an aluminum body and end caps. A reload kit obtained from the manufacturer contains a thin cardboard liner, propellant pellets, delay pellet, ejection charge, nozzle and seals. By assembling all these parts, you create a new engine at slightly less cost than a single shot engine. Reloadable engines are not for beginners, but experienced rocketers may find the reduced cost advantageous. Return to contents. Installing An Engine How you install a rocket engine in a rocket depends on the particular rocket. The simplest installation has a wrap of tape placed around the nozzle end of the engine and then the engine is forced into the engine mount. The tape provides a tight fit so the engine won't pop out when the ejection charge fires. A problem with this type of engine mount is that the engines can be difficult to remove after a flight. It is useful to have a three foot piece of hardwood dowel that can be slid down the rocket tube from the front to push the engine out the back. Another simple installation, is to tape the engine in place. This installation only works if a sufficient amount of the engine mount is accessible so that you can tape to both it and the engine. This method does have the advantage that it is easier to remove an engine after a flight. Many models have a metal clip that holds the engine in. The clip is pushed to the side, the engine is inserted into its mount and the clip snaps back when the engine is fully inserted. This type of mount also allows easy removal of an engine after a flight. For some models you do not want the engine to stay with the model but you want it to be ejected when the ejection charge fires. Models of this type include those that employ tumble recovery and those that change to a glider. Return to contents. Using Igniters The simplest igniter consists of a short wire with a high resistivity section in the center that is coated with some explosive. The igniter is inserted in the back of an engine and held in place with a plastic plug or with a small ball of recovery wadding held in with tape. An Estes style igniter. To launch the rocket, it is placed on the launch wire and the launch controller is attached to the igniter wires with two alligator clips. To fire the rocket, a current is pushed through the wire causing it to heat up and ignite the explosive. The explosive then ignites the engine. Note how the igniter wires are bent into an arc so that the alligator clips can get a better grip on it. Attaching alligator clips to the igniter. A different type of igniter is the copperhead. This igniter consists of a strip of plastic with copper on both sides. A small ball of conductive explosive is placed on one end. It is also inserted into an engine, but a special clip is used to attach it to the launch controller. The clip has two wires attached to the two sides of the clip. When the clip is placed on the end of the igniter, the two wires attach to the two copper films. The rocket is fired in the same way, with a current driven through the copper strips that ignites the explosive. We have had a lot of misfires using copperhead igniters. The problem is usually a short across the plastic strip caused by bending or twisting the igniter such that the two copper strips come into contact. Copperhead igniter system Igniterman style igniters are made by stripping the insulation off of a quarter inch of two wires and then twisting all but the end of the wires so that the stripped ends are close (about the thickness of a thick sheet of paper) but not touching. This end is then dipped in a flammable conductor that creates a thin film between the two wires. Running a current through the wires and the film causes the film to ignite. After the film dries, the igniter is dipped in a pyrogen mixture. This mixture causes a small explosion that ignites the rocket fuel. An Igniterman style igniter. Return to contents. Two-Stage Rockets In most two state rockets, a booster engine is taped to an upper stage engine. The booster engine has no smoke/delay charge or ejection charge so when the propellant is consumed, the burn blows out the back of the engine, which ignites the second engine and burns through the tape, separating the booster from the upper stage. Note that taping only works for black powder motors. A booster engine taped to an upper stage engine for a two-stage rocket. More complicated rockets and rockets that have a composite engine as the upper stage use a timer and an electrical igniter to fire the upper stage. Return to contents Previous Section Next Section

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rocket

This article is about vehicles powered by rocket engines. For other uses, see Rocket (disambiguation).

A Soyuz-U, at Baikonur Site 1/5.

Launch of Apollo 15 Saturn V rocket: T-30s through T+40s.

A rocket or rocket vehicle is a missile, spacecraft, aircraft or other vehicle which obtains thrust by ejecting a jet of fast moving fluid from a rocket engine. The action of the fluid against the inside ofcombustion chambers and expansion nozzles is able to accelerate the fluid to extremely high speed, and this exerts a large reactive thrust on the rocket (an equal and opposite reaction according to Newton's third law).

Rockets, in military and recreational uses, date back to at least the 13th century.^[1] Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology of the Space Age, including setting foot on the moon.

Rockets are used for fireworks weaponry, ejection seats, launch vehicles for artificial satellites,human spaceflight and exploration of other planets. While comparatively inefficient for low speed use, they are very lightweight and powerful, capable of generating large accelerations and of attainingextremely high speeds with reasonable efficiency.

Chemical rockets are the most common type of rocket and they typically create their exhaust by the combustion of rocket propellant. Chemical rockets store a large amount of energy in an easily-released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks.

CULTURE

Responsible for leading Rocket Communications corporate culture Michal Anne has striven for a balance of Professionalism and fun. Rocket is proud of being known throughout the industry as being a friendly, approachable and highly respected company to work with. Sixteen years of Experience has taught us that the best possible result is obtained by simply connecting with and being responsive to our clients. Our recipe of experience + talent + technical savvy + humor + humility allows us to consistently surpass our clients expectations from concept to completion. As a small company where everyone has a “Hands-on” approach we are able to deftly change direction and scope as our clients needs and expectations change. We save our clients time and money. Establishing a creative alliance with the already established marketing and engineering teams within the companies we work for, we are able to harness our combined skill and knowledge base to create compelling solutions for our projects whether they are for emerging or conventional technologies.

Phase One | Investigation and Analysis

Knowledge & Understanding

• It is essential that our team has a strong foundation of knowledge and understanding about a particular product or engagement before beginning to design. We quickly gather information and requirements about the current version of the product, past product iterations, the user’s needs, client business objectives, marketing objectives, and technical requirements. Our designers create informed and intelligent designs.

Phase Two | Strategy

The 50,000 foot view of the new product

• We take what we learned during Investigation & Analysis phase and design the high level product paradigm. During the Strategy phase we create things like new work flow diagrams and task flow diagrams. We also design concept wire-frames based on the task flows that include product navigation, high-level content groupings, and general page layouts.

Phase Three | Design

When the magic starts to happen

• USER INTERFACE DESIGN: The User Interface Design team will create the final UI wire-frames. UI wire-frames are grey-scale representations of the final product screens. They include all the interaction behaviours, final screen content, major layouts, navigation, widgets & controls, final naming, and data display.
• VISUAL DESIGN: Once the UI wire-frames are finalized the Visual Design team will create a Visual Language for the product. Visual Language establishes the user’s emotional bond with a product and represents the brand identity. A successful Visual Language will enhance the product usability via size, color, style, organization, layout, and metaphor.

Phase Four | Production & Implementation

When all the pieces come together

• USER INTERFACE DESIGN: UI wire-frames are designed for all the key areas of the application. Rocket designs all the areas of the product that are needed to communicate clearly to our clients and their engineering team a concise overview of the features and functionality for the product.
• VISUAL DESIGN: Rocket’s Visual Designers apply the product Visual Language to all the necessary screens to clearly communicate to our clients and their engineering team a concise overview of how to build the entire application. Rocket then creates all the necessary graphic assets and exports them into the appropriate file formats needed by engineering for inclusion into the product.

Phase Five | Final Delivery

All wrapped up with a bow

• Rocket ensures our clients have a seamless integration of our designs into their product by providing concise engineering specifications for both the User Interface behaviour and the Visual Design layout. We have hand-off meetings to go over any questions from engineering and are available by phone for any unforeseen needs after project conclusion.

sign

this is the sign of Mohandas Karamchand Gandhi

cites

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This site provides educators and specialists in Japan Studies a space for sharing, discussing

WELCOME.

This site provides educators and specialists in Japan Studies a space for sharing, discussing and developing teaching ideas and resources about Japan, especially as they relate to K-12 classrooms. The site features thought-provoking essays; classroom-ready lesson plans; an area for asking and answering questions; resources including historical documents, maps and images; and member profiles. In addition to user-generated content, the editorial team will develop original materials organized around different themes. We invite you to contribute materials of your own and join the discussion.

developing teaching ideas and resources about Japan, especially as they relate to K-12 classrooms. The site features thought-provoking essays; classroom-ready lesson plans; an area for asking and answering questions; resources including historical documents, maps and images; and member profiles. In addition to user-generated content, the editorial team will develop original materials organized around different themes. We invite you to contribute materials of your own and join the discussion.

short stories --the story of a rice cooker

the story of a rice cooker

Once upon a time, there was a little rice cooker. His name was Hiro. He lived in a dusty box in the "Super Oriental Big Super Store," in Elizabeth, New Jersey. He was a rather expensive rice cooker, and his box was on a high shelf. No one ever seemed to notice him there. Fortunately, Hiro was not an ambitous rice cooker. He was the sort of person who would be content no matter what happened to him.

He liked to do mental arithmetic, and he found his box a pleasant home. The styrofoam was custom-made to fit around the contours of his sides, which was cozy. In sum, he was satisfied with his lot in life.

But one day, unbeknownst to Hiro, a new model of rice cooker was released by the company who had made him. It was known as the ADVANCED Fuzzy Logic Easy-Select Many Menu Option Rice Cooker Model. Hiro was a Fuzzy Logic Easy-Select Many Menu Option Rice Cooker. He was not ADVANCED.

The owner of the Super Oriental Big Super Store decided that now was the time to clear some space on the rice cooker shelf. So, naturally enough, she put Hiro on sale. She moved him to a new spot on the clearance table. He did not notice the change, because he was inside his box, and engrossed in working out the cube root of 97336.

The very next day, a weedy young man with a small, tidy Afro came into the Super Oriental Big Super Store. He selected a few blocks of fresh tofu, a package of dried shiitake mushrooms, some pak choi, a few flavors of rice seasoning, and a large bottle of dark soy sauce. He browsed among the teapots but decided that he already owned enough teapots. Then he came to the clearance table. Well, you know what happened next, because I would not have mentioned this young man if he were not going to have an important effect on the life of Hiro the rice cooker.

This young man (whose name was Franklin Holmes) could not really afford Hiro, even at his greatly reduced price. But he could not resist the bargain. And he did, after all, eat a great deal of rice. So Franklin Holmes bought Hiro, along with his tofu and his mushrooms and his furikake and his soy sauce.

This time Hiro noticed that something was up. He was jostled and jumbled, and despite his custom styrofoam, he was quite shaken up. He became carsick, in an electronic sort of way. None of this was pleasing to our friend the rice cooker. He felt out of sorts. He was far too rattled to do any mental arithmetic. This was definitely a bad day. Hiro could not remember the last time he had had a bad day.

Eventually Franklin Holmes arrived at his little apartment. He put his groceries away and then removed Hiro from his box. Hiro was aghast. His custom styrofoam!

And then Franklin Holmes threw Hiro's box away.

Hiro hated Franklin Holmes.

Franklin Holmes made many batches of rice. If he could, Hiro would have made the rice soggy or burnt, but he was not made that way. Every time he turned out another pot of perfect rice, Hiro's irritation grew. He reckoned that it was exponential in its growth, but he could not tell for sure, because it had been a long time since he had had the peace of mind to engage in any mental arithmetic.

Hiro hated Franklin Holmes with every circuit in his body. But eventually, after even more nights of perfect batch after perfect batch of rice, Hiro got tired. His hate was getting a little stale. He discovered that he was more bored than angry, these days. So, out of desperate tedium, he began to pay attention to Franklin Holmes and his habits.

It appeared that Franklin Holmes did other things with his time than forcing Hiro to make rice, be it white or brown or mixed with other grains. He spent a lot of time writing and chewing on a pencil and squinting into space. Despite himself, Hiro was becoming curious about the nature of the endeavors of Franklin Holmes.

While Hiro tried to decipher these activites, he noticed that Franklin also played the violin. And much as Hiro wanted to be able to think that Franklin was not good, he had to admit that he enjoyed the music. It facilitated the doing of mental arithmetic. And it was also true that Franklin Holmes seemed to appreciate the rice that Hiro made. Sometimes he would even invite other people to his apartment and make a special point of showing Hiro off to them.

The next time Franklin had guests, Hiro listened very carefully. At first, everyone just talked about how tasty the food was. Hiro felt this was sensible and appropriate, though he was impatient to learn something new. Finally, someone said to Franklin, "How is the work?"

And they cleared off the table and sat down to look at some of the pieces of paper. Everyone talked at once. They were talking about exponents! And factorials! Hiro began to look at Franklin in a different light. He was really a very good looking fellow, especially now that he had been fattening up on so much good rice.

And the equations they were talking about were strangely familar to Hiro. Slowly he realized that they were talking about him! Franklin Holmes was writing a paper about fuzzy logic, and he had been working on it all this time, even as Hiro had been burning with fuzzy, logical hate.

Hiro was filled with remorse. He had been unjust.

In the months that followed, Hiro's respect for Franklin grew and grew. Eventually, the paper was published, and they celebrated together over an enormous pilaf. Hiro wished that he could apologize for the injustice that he had done. He wished that he could express the deep affection that he now felt for Franklin. But there were only four spaces on his display, and all he could say was d0nE.

The End.