Aerospace Engineering and Techniques

SPACEX - Founded by Elon Musk

2021-05-16T19:49:00.000+05:30

Space Exploration Technologies Corp. (SpaceX) is an American aerospace manufacturer and space transportation services company headquartered in Hawthorne, California. SpaceX was founded in 2002 by Elon Musk. SpaceX manufactures the Falcon 9 and Falcon Heavy launch vehicles, several rocket engines, Dragon cargo, crew spacecraft and Starlink communications satellites.

SpaceX's achievements include the first privately funded liquid-propellant rocket to reach orbit (Falcon 1 in 2008), the first private company to successfully launch, orbit, and recover a spacecraft (Dragon in 2010), the first private company to send a spacecraft to the International Space Station (Dragon in 2012), the first vertical take-off and vertical propulsive landing for an orbital rocket (Falcon 9 in 2015), the first reuse of an orbital rocket (Falcon 9 in 2017), and the first private company to send astronauts to orbit and to the International Space Station (SpaceX Crew Dragon Demo-2 in 2020). SpaceX has flown and reflown the Falcon 9 series of rockets over one hundred times.

Space tourism

In February 2020 Space Adventures announced plans to fly private citizens into orbit on Crew Dragon in late 2021 or 2022. The company would launch a Crew Dragon with up to four paying tourists on board, and spend up to five days in a low Earth orbit above the orbit of the International Space Station.

Combustion Area of Gas Turbine

2011-07-30T21:33:00.002+05:30

This high-pressure air then enters the combustion area, where a ring of fuel injectors injects a steady stream of fuel. The fuel is generally kerosene, jet fuel, propane or natural gas. If you think about how easy it is to blow a candle out, then you can see the design problem in the combustion area -- entering this area is high-pressure air moving at hundreds of miles per hour. You want to keep a flame burning continuously in that environment. The piece that solves this problem is called a "flame holder," or sometimes a "can." The can is a hollow, perforated piece of heavy metal. Half of the can in cross-section is shown below:

The injectors are at the right. Compressed air enters through the perforations. Exhaust gases exit at the left. You can see in the previous figure that a second set of cylinders wraps around the inside and the outside of this perforated can, guiding the compressed intake air into the perforations.

Advantages and Disadvantages of Jet Engines

2011-07-30T21:32:00.000+05:30

So why does the M-1 tank use a 1,500 horsepower gas turbine engine instead of a diesel engine? It turns out that there are two big advantages of the turbine over the diesel:

Gas turbine engines have a great power-to-weight ratio compared to reciprocating engines. That is, the amount of power you get out of the engine compared to the weight of the engine itself is very good.
Gas turbine engines are smaller than their reciprocating counterparts of the same power.

The main disadvantage of gas turbines is that, compared to a reciprocating engine of the same size, they areexpensive. Because they spin at such high speeds and because of the high operating temperatures, designing and manufacturing gas turbines is a tough problem from both the engineering and materials standpoint. Gas turbines also tend to use more fuel when they are idling, and they prefer a constant rather than a fluctuating load. That makes gas turbines great for things like transcontinental jet aircraft and power plants, but explains why you don't have one under the hood of your car.

Gas turbine

2011-07-30T21:30:00.001+05:30

At the left of the engine is the turbine section. In this figure there are two sets of turbines. The first set directly drives the compressor. The turbines, the shaft and the compressor all turn as a single unit:

At the far left is a final turbine stage, shown here with a single set of vanes. It drives the output shaft. This final turbine stage and the output shaft are a completely stand-alone, freewheeling unit. They spin freely without any connection to the rest of the engine. And that is the amazing part about a gas turbine engine -- there is enough energy in the hot gases blowing through the blades of that final output turbine to generate 1,500 horsepower and drive a 63-ton tank. A gas turbine engine really is that simple.

In the case of the turbine used in a POWER PLANT, there really is nothing to do with the exhaust gases but vent them through an exhaust pipe, as shown. Sometimes the exhaust will run through some sort of heat exchanger either to extract the heat for some other purpose or to preheat air before it enters the combustion chamber.

The discussion here is obviously simplified a bit. For example, we have not discussed the areas of bearings, oiling systems, internal support structures of the engine, stator vanes and so on. All of these areas become major engineering problems because of the tremendous temperatures, pressures and spin rates inside the engine. But the basic principles described here govern all gas turbine engines and help you to understand the basic layout and operation of the engine.

HOW GAS TURBINE ENGINE WORKS

2011-07-30T21:29:00.000+05:30

Gas turbine engines are, theoretically, extremely simple. They have three parts:

Compressor - Compresses the incoming air to high pressure
Combustion area - Burns the fuel and produces high-pressure, high-velocity gas
Turbine - Extracts the energy from the high-pressure, high-velocity gas flowing from the combustion chamber

The following figure shows the general layout of an axial-flow gas turbine -- the sort of engine you would find driving the rotor of a helicopter.

For E.G

In this engine, air is sucked in from the right by the compressor. The compressor is basically a cone-shaped cylinder with small fan blades attached in rows (eight rows of blades are represented here). Assuming the light blue represents air at normal air pressure, then as the air is forced through the compression stage its pressure rises significantly. In some engines, the pressure of the air can rise by a factor of 30. The high-pressure air produced by the compressor is shown in dark blue.

Interesting Facts about Aerospace Engineering!!!

2011-07-30T21:28:00.000+05:30

Interesting Facts about Aerospace Engineering!!!

Aerospace engineering is the branch of engineering behind the design, construction and science of aircraft and spacecraft
The energy released by the three Space Shuttle main engines is equivalent to the output of 23 Hoover Dams.
Participate in flight test programs to measure take-off distances, rate of climb, stall speeds, manoeuvrability and landing capacities

ROCKET PROPULSION

2010-01-26T02:35:00.002+05:30

ROCKET PROPULSION

Rocket propulsion systems can be classified according to the type of energy source (chemical, nuclear, or solar), the basic function (booster stage, sustainer, attitude control, orbit station keeping, etc.), the type of vehicle (aircraft, missile, assisted take-off, space vehicle, etc.), size, type of propellant, type of construction, or number of rocket propulsion units used in a given vehicle. Each is treated in more detail in subsequent chapters.Another way is to Classify by the method of producing thrust. A thermodynamic expansion of a gas is used in the majority of practical rocket propulsion concepts. The internal energy of the gas is converted into the kinetic
energy of the exhaust flow and the thrust is produced by the gas pressure on the surfaces exposed to the gas, as will be explained later.

rocket propulsion

2010-01-26T02:34:00.001+05:30

PROPULSION

Propulsion in a broad sense is the act of changing the motion of a body. Propulsion mechanisms provide a force that moves bodies that are initially at rest, changes a velocity, or overcomes retarding forces when a body is propelled through a medium. Jet propulsion is a means of locomotion whereby a reaction force is imparted to a device by the momentum of ejected matter. Rocket propulsion is a class of jet propulsion that produces thrust by ejecting stored matter, called the propellant. Duct propulsion is a class of jet propulsion and includes turbojets and ramjets; these engines are also commonly called airbreathing engines. Duct propulsion devices utilize mostly the surrounding medium as the "working fluid", together with some stored fuel. Combinations of rockets and duct propulsion devices are attractive for some
applications and are described in this chapter. The energy source most useful to rocket propulsion is chemical combustion. Energy can also be supplied by solar radiation and, in the past, also by nuclear reaction. Accordingly, the various propulsion devices can be divided
into chemical propulsion, nuclear propulsion, and solar propulsion. lists many of the important propulsion concepts according to their energy source and type of propellant or working fluid. Radiation energy can originate from sources other than the sun, and theoretically can cover the transmission of energy by microwave and laser beams, electromagnetic waves, and
electrons, protons, and other particle beams from a transmitter to a flying receiver. Nuclear energy is associated with the transformations of atomic particles within the nucleus of atoms and can be of several types, namely,fission, fusion, and decay of radioactive species. Other energy sources, both internal (in the vehicle) and external, can be considered.

INTRODUCTION TO SPACE SCIENCE.

2010-01-26T02:27:00.004+05:30

Around 350 BC,the planets for over two thousand years! Aristotle was of the opinion that all the heavenly bodies, including the sun, the wanderers (planets), and the stars, were in circular motion about a (planets), and the stars, were in circular motion about a fixed and unmoving
Earth. So authoritative was Aristotle that the Catholic church later accepted this view as its official doctrine on the matter and used its religious influence to enforce this position. As a direct result, Galileo was arrested for espousing views to the contrary in 1600 A.D.! However, a century before Galileo, the first serious questioning of Aristotle’s views ad already begun.
Astronomy (or rather astrology) was very popular at the time of Copernicus,around 1500 A.D., and the inability to accurately describe the motions of the heavenly bodies increased efforts to find a better explanation than Aristotle’s. Copernicus was both an astronomer and mathematician, and he used the observed angular positions of the planets and rigonometry to correctly place the solar system in its proper order, with the sun at the center and the earth as just another wanderer in motion about the sun like the other planets. However, the idea of a moving earth and similarity with the other planets was quite radical at the time and made his heliocentric (sun-centered) hypothesis hard to accept.For instance, Tycho Brahe, the late sixteenth-century astronomer, completely rejected the notion. Tycho, in the years prior to his death in 1601, conducted the most exhaustive and accurate recording of the movements of the planets to date. He was sure that his data held the secret to the mystery of planetary movements, but his mathematical ability was too poor to check out his theories. Therefore, Tycho solicited the assistance of mathematicianslike Johannes Kepler.after Tycho’s death, Kepler came into possession of most of the observational records kept over the many years. Kepler believed in the Coperni- 26

DESIGN OF ROCKET POWERED ORBITAL SPACECRAFT

2010-01-26T02:26:00.003+05:30

The feasibility of single-stage-suborbital (SSSO), single-stage-to-orbit (SSTO), and two-stage-to-orbit (TSTO) rocket-powered spacecraft is investigated using optimal control theory. Ascent trajectories are optimized for different combinations of spacecraft structural factor and engine specific impulse, the optimization criterion being the maximum payload weight. Normalized payload weights are computed and used to assess feasibility. the results show that SSSO feasibility does not necessarily imply SSTO feasibility: while SSSO feasibility is guaranteed for all the parameter combinations considered, SSTO feasibility is guaranteed for only certain parameter combinations, which might be beyond the present state of the art. On the other hand, not only TSTO feasibility is guaranteed for all the parameter combinations considered, but a TSTO spacecraft is considerably superior to a SSTO spacecraft in terms of payload weight.Three areas of potential improvements are discussed:

(i) use of lighter materials (lower structural factor) has a significant effect on payload weight and feasibility;

(ii) use of engines with higher ratio of thrust to propellant weight flow

universal space vheical design concept

2010-01-26T02:20:00.004+05:30

Theoretical and experimental estimations are given on the structure of a universal space interceptor designed on the modular principle. The interceptor comprising one command-impact module and a variable number of separable impact modules, each with propulsion and guidance systems, can be injected into a trajectory towards an Earth approaching space object by launch vehicles MOLNIYA, PROTON, TITAN-4, ARIANE-5, N-2, and ANGARA. The universal space interceptor is capable to attack Earth approaching asteroids and comets of up to 300 m in diameter and destroy them into a number of safe fragments. In this case objects with a diameter of up to 100-150 m are destroyed by non-nuclear kinetic module and to attack larger objects it is required to use a nuclear explosive device.

USI OPERATION PROCEDURE

On detection of an Earth approaching DSO ground data support facilities (first optical then radio telescopes) determine (adjust) its flight trajectory, size and class. In terms of the DSO-Earth impact point predicted and possible after-effects the necessity of DSO interception is determined and the DSO interception point and USI completeness are specified. After this the launch complex, launch vehicle, post boost stage and USI prelaunch preparation is performed, LV is launched and USI is injected into a trajectory to the USI-DSO impact point. The prelaunch procedures duration is minimized since the interception complex is kept on the alert. During USI independent radio-controlled flight the necessary USI trajectory adjustment is made. On DSO detection with USI on-board equipment the USI flight trajectory is adjusted (about 1000 s before impact). Impact modules are separated one-by-one (within every 100 s) and deployed as a sequence of modules at intervals of about 25 km. The command-impact module is behind the “chain” of impact modules.
On the basis of DSO final inspection with CIM on-board facilities the most appropriate KSP-DSO surface impact points are specified. At 7 000 - 10 000 km from DSO the impact modules self-guidance onto the points specified is performed. On the basis of IM-DSO impact monitoring and prediction of its own DSO impact accuracy the command-impact module generates a message on the successful DSO interception.Ground monitoring facilities confirm DSO disintegration into fragments and estimate the trajectories of the largest ones to make it possible to qualify the DSO material, structure and mechanical properties (predetermined by the remote monitoring data).

CONCLUSION:

1. By the analysis of the possible frequency of various-size space objects falls on
the Earth there are distinguished objects of 20-300 m in diameter the probability of
USI completeness USI-6 USI-5 USI-3 USI-1 USI-N
Number of IM 5 4 2 -
USI mass, kg 10054 8304 4891 1590 2757
USI length, m 10.05 8.5 5.4 2.3
USI diameter, m 3.0 1.8
KSP set mass, kg 7250 5950 3350 750
NED mass, kg - 1127
DSO intercepted diameter, m 40-150 20-70 100-300
Launch vehicle ANGARA PROTON ZENIT MOLNIYA

Note: Mass and dimension data are given for USI without adapter, aerodynamic fairing
and safety support system.collision with which is relatively high (several collisions during 20 years are possible), but which cannot be predetected with present-day monitoring facilities.
Such DSO may be intercepted at an altitude within 100 000 km with either a set of kinetic star-shaped penetrators (DSO diameter within 100-150 m) or a nuclear explosive device. In this case the interception complex must be always kept in operational conditions (prelaunch preparation lasts for about 1-2 days after DSO is detected).

2. A concept of a universal space interceptor designed on the modular principle is proposed. The universal space interceptor comprises a command-impact module and a variable number (from 0 to 5) of impact modules. Each module is provided with a kinetic star-shaped penetrator and DSO guidance system. In this case DSO long-range detection and final inspection, determination of appropriate DSO surface impact point, USI trajectory adjustment (in independent flight), USI
separation to modules, module-to-DSO approach arrangement required and USIground services communication is supported with the command-impact module systems.

3. The characteristics of present-day launch vehicles of different payload capacity (MOLNIYA, ZENIT, PROTON, ANGARA, et al.) and space monitoring facilities are sufficient to provide USI efficient application.

4. In the course of the universal space interceptor development the basic issues which arise during creation and operation of a dangerous space object protection system will be theoretically substantiated and tested.

foreign exhange

2009-09-13T13:50:00.001+05:30

exchange world
he Express FX Trading Course teaches you where to get in the market and why, and where to get out of the market and why. We have found that when a trader learns this simple concept, they are able to take advantage of the market instead of the market taking advantage of them. The Express FX Trading Course comes with 5 comprehensive CDs and a trader’s workbook. Each Lesson is a media CD that is approximately 1 hr. in length. They are easy-to-understand and viewed directly on your computer. You will be able to watch, hear and review the material as many times as you want and at your own pace.

forex secret:

Our currency trading forex courses are awesome and the hard work to come out these forex training course are proven logical, powerful, robust and well presented methodology. We have the great trader and mentor. The strategies that are being taught honestly in the course have paved & lighted the forex trading path & turned the dumb money into smart money. The pivot point trading method is analagous to precision guidance system. The signal analysis method gives high level of accuracy and most of the traders truly learn from the concise and useful technical information.

forex trading.

2009-09-13T13:49:00.000+05:30

The currency fluctuate continuously due to reasons such as political, economical reasons, sometimes the changes could be extremely great, therefore, the Forex traders also can have the opportunity in among which makes a profit. For example, the Japanese Yen daily fluctuation is probably between 0.7% to 1.5%, Forex traders may make profit through buying and selling. All trading could be completed in a short time, the trading strategy could be carry up according to the market conditions, it is extremely flexible, even if the direction looks wrong, the lost could be stop immediately, the lost could reduce but profit potential is still great. Therefore, the Foreign Exchange margin trading is the most flexible and the most reliable investment method.
Foreign Exchange Margin Trading elementary knowledge

learn forex trading

2009-09-13T13:46:00.001+05:30

FOREX (the Foreign Exchange market) is an international market where participants speculate on the value of different currencies, buying and selling dollars, pounds, euros, and other currencies.
There are only a few major currencies to follow, compared to hundreds of stocks in the equities market. In order to get started understanding Forex, sign up for a free practice account today and learn as you trade!

Trading risk free with a practice account is the best way to get familiar with this ever-growing market. And once you are signed up, CMS Forex will provide you with thorough educational resources to guide you along the way.

So don't wait, take this opportunity to get started trading Forex!

e-forex software.

2009-09-13T13:44:00.002+05:30

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e-forex software.

2009-09-13T13:44:00.001+05:30

e-forex software.

2009-09-13T13:44:00.000+05:30

FOREX MARKET EXISTENCE

2009-09-08T20:12:00.002+05:30

FOREX MARKET EXISTENSE:

Presently, there are various kinds of financial market, it is divided into: Stock market, interest market (including bond, commercial bill and so on), gold market (including gold, platinum, silver), futures market (including grain, cotton and kapok, oil and so on), option market and foreign exchange market or forex market and so on.The foreign exchange market is a place to trade foreign exchange currency, or it is also a place for the transaction of all foreign currency. The foreign exchange market therefore is existence, because of:
Trade and investmentImport and export business, people pays one kind of currency when doing business, but when earns another kind of currency when receive the commodity. This means that, when settling account, business people will pay and receive different currencies. Therefore, they must convert the currencies that they received into the currencies that they could buy commodities. With this similar, when buying a foreign property a company must use the concerned country's currency to make payment, therefore, it needs to convert the domestic currency is concerned country's currency.
Speculation Currencies exchange rates could fluctuate according to the demand and supply between two currencies. A Forex trader buys up one kind of currency in an exchange rate, but up casts this currency in another more advantageous exchange rate, he may gain. Speculation has occupied most of the Forex market.
Hedging Due to the fluctuation between two currencies, those companies who owns foreign asset (for example factory), when these companies convert these properties into cost country currencies, there consist of certain risks. When the value of a foreign asset which is estimated based on foreign currencies remained unchanged, if the exchange rate changes, when converting this property value according to the domestic currency, there could be profit and loss. The company may eliminate such hidden risk through hedging. This carries out a foreign currency trading, its transaction result just counterbalances the foreign currency property profit and loss which produces by the exchange rate change.
Forex Market Development The history of the Forex market as an international capital speculation market is much shorter compared the stock, the gold, the stock, the interest market, but it is developing in an astonishing speed. Today, the foreign exchange market daily trading volume has amounted to 150 billion US dollars, it’s scale has gone far beyond the stock, the stock and other finance commodity markets, it has became the world's most biggest sole finance market and the also the speculation market. Since the birth of the foreign exchange market, the fluctuation of the exchange rate of the Forex market is becoming bigger. In September 1985, 1 US dollar exchanged 220 Japanese Yen, but in May 1986, 1 US dollar only could exchange 160 Japanese Yen, in 8 months, the Japanese Yen has revalued 27%. In recent years, the foreign exchange market wave amplitude has been bigger, on September 8, 1992, 1 pound exchanged 2.0100 US dollars, on November 10, 1 pound exchanged 1.5080 US dollars, in the short two months, the pound exchanged US dollar exchange rate to fall more than 5,000, depreciated 25%. Not only that, presently, everyday the fluctuation of the exchange rate of the Forex market enlarges unceasingly, within a day the rise and drop 2% to 3% is commonly seen. On September 16, 1992, the pound exchanged US dollar from 1.8755 to fall to 1.7850, the pound on first lowers 5%. Due to the large fluctuation of the Forex market, it has created more opportunities for the investor, attracted more and more investors to join this ranks.

FOREX MARGIN TRADING:

2009-09-08T20:12:00.001+05:30

FOREX MARGIN TRADING:

Comparing to other investment, the Foreign Exchange margin trading is one of the fairest and the most attractive investment method.
The Foreign Exchange margin trading meaning the traders borrow loan from bank, finance organization or broker house to carry on the foreign currency trading. Generally, the financing proportion is above 20 times, which means the Forex traders
’ fund may enlarge to 20 times to carry on the trading. The bigger the financing proportion, means the Forex traders just need to pay very less fund, for example, the financing proportion provided by the financial organization is 400 times, namely the lowest margin request is 0.25%, the traders just need to pay 25 US dollars, then he or she could trade as high as 10,000 US dollars, fully using the contra method to make big profit by only paying a very less price.
Besides the fund enlargement, another attraction of the Forex margin trading method is that it can be traded in both ways, you can make profit by buying the currency when the currency rise (makes many), or to sell a currency when the currency is dropping to make profit (short-selling), thus does not need to be restricted by the restriction so-called bear market is unable to make money.
Making Profit in the Foreign Exchange Market
The currency fluctuate continuously due to reasons such as political, economical reasons, sometimes the changes could be extremely great, therefore, the Forex traders also can have the opportunity in among which makes a profit. For example, the Japanese Yen daily fluctuation is probably between 0.7% to 1.5%, Forex traders may make profit through buying and selling. All trading could be completed in a short time, the trading strategy could be carry up according to the market conditions, it is extremely flexible, even if the direction looks wrong, the lost could be stop immediately, the lost could reduce but profit potential is still great. Therefore, the Foreign Exchange margin trading is the most flexible and the most reliable investment method.Foreign Exchange Margin Trading elementary knowledge.

MILLION DOLLAR TRADE

2009-09-08T20:10:00.000+05:30

MILLION DOLLAR TRADE:

Million Dollar Traders was on BBC2 last night. What a great introduction to city traders and how unpredictable the Stock market can be! So thats why I trade the Forex and not the Stock Market then!
Some of the trainees have aspirations to trade full time including a retired man who was interviewed stating that he wanted to use his savings to trade from home after the series had finished. With the availability of great trading from home facilities avaialble to anyone, anywhere in the world and anytime day or night - trading from home, especially within the Forex market is a real possibility.

Well I guess it was pretty bad timing as the program was filmed last year when Freddie Mac and Fannie Mae announced financial meltdown in the US so the newbies couldn't be trading at a worse time! However the familiar 'frozen finger' inability to place a trade was prevalent so too was emotional attachment and emotional reactions, loss of confidence etc to trading which most newbies go through - including myself.......oh yes some good 'ol roller-coaster days but have managed to keep it together long enough to have learnt and come through the other side.

Having said that I haven't been able to do it trading the UK Stock market - Forex is where its at as far as I'm concerned so hats off to the guys in the program for trading the UK Stock market through one of the most difficult periods in a generation.

Trading psychology and risk management as emphaised in the program are essential key factors to get right when trading any market. Building this into your strategy, giving yourself targets such as the '3 srikes and your out' rule will make this easier to deal with. Don't allow yourself more than 3 trades to go against you in one trading period. If that happens finish for the day there.

Trading any market has the ability to wipe out your money, savings and future. As the Million Dollar Trader program is showing, trading without strategies is like playing with fire. Formulate a good solid trading strategy before you open any position - it will also make you more confident as knowing you have done your homework is good for your trading mindset.

JET ENGINE

2009-09-06T19:04:00.002+05:30

JET ENGINE:

A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's laws of motion.
This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets. In general, most jet engines
are internal combustion engines but non-combusting forms also exist.

In some common parlance, the term 'jet engine' is loosely referred to an internal combustion duct engine, which typically consists of an engine with a rotary (rotating)
air compressor powered by a turbine ("Brayton cycle"), with the leftover power providing thrust via a propelling nozzle. These types of jet engines are primarily used by jet aircraft for long distance travel. The early jet aircraft used turbojet engines which were relatively inefficient for subsonic flight. Modern subsonic jet aircraft usually use high-bypass turbofan engines which help give high speeds as well as, over long distances, giving better fuel efficiency than many other forms of transport.

HISTORY:

Jet engines can be dated back to the invention of the aeolipile before the first century AD. This device used steam power directed through two nozzles so as to cause a sphere to spin rapidly on its axis. So far as is known, it was not used for supplying mechanical power, and the potential practical applications of this invention were not recognized. It was simply considered a curiosity.

Jet propulsion only literally and figuratively took off with the invention of the rocket by the Chinese in the 13th century. Rocket exhaust was initially used in a modest way for fireworks but gradually progressed to propel formidable weaponry; and there the technology stalled for hundreds of years.

USES:

Jet engines are usually used as aircraft engines for jet aircraft. They are also used for cruise missiles and unmanned aerial vehicles.

In the form of rocket engines they are used for fireworks, model rocketry, spaceflight, and military missiles.

Jet engines have also been used to propel high speed cars, particularly drag racers, with the all-time record held by a rocket car. A turbofan powered car ThrustSSC currently holds the land speed record.

Jet engine designs are frequently modified to turn them into gas turbine engines which are used in a wide variety of industrial applications.
These include electrical power generation, powering water, natural gas, or oil pumps, and providing propulsion for ships and locomotives. Industrial gas turbine can create up to 50,000 shaft horsepower.
Many of these engines are derived from older military turbojets such as the Pratt & Whitney J57 and J75 models.
There is also a derivative of the P&W JT8D low-bypass turbofan that creates up to 35,000 HP.

COMPONENTS:

The major components of a jet engine are similar across the major different types of engines, although not all engine types have all components. The major parts include:

Cold Section:

Air intake (Inlet) — For subsonic aircraft, the air intake to a jet engine consists essentially of an opening which is designed to minimise drag. The air reaching the compressor of a normal jet engine must be travelling below the speed of sound, even for supersonic aircraft, to allow smooth flow through compressor and turbine blades. At supersonic flight speeds, shockwaves form in the intake system, these help compress the air, but also there is some inevitable reduction in the recovered pressure at inlet to the compressor. Some supersonic intakes use devices, such as a cone or a ramp, to increase pressure recovery.
Compressor or Fan — The compressor is made up of stages. Each stage consists of vanes which rotate, and stators which remain stationary. As air is drawn deeper through the compressor, its heat and pressure increases. Energy is derived from the turbine (see below), passed along the shaft.
Bypass ducts — Much of the thrust of essentially all modern jet engines comes from air from the front compressor that bypasses the combustion chamber and gas turbine section that leads directly to the nozzle or afterburner (where fitted).
Common:
Shaft — The shaft connects the turbine to the compressor, and runs most of the length of the engine. There may be as many as three concentric shafts, rotating at independent speeds, with as many sets of turbines and compressors. Other services, like a bleed of cool air, may also run down the shaft.
Diffuser section: - This section is a divergent duct that utilizes Bernoulli's principle to decrease the velocity of the compressed air to allow for easier ignition. And, at the same time, continuing to increase the air pressure before it enters the combustion chamber.
Hot section:
Combustor or Can or Flameholders or Combustion Chamber — This is a chamber where fuel is continuously burned in the compressed air.

A blade with internal cooling as applied in the high-pressure turbine
Turbine — The turbine is a series of bladed discs that act like a windmill, gaining energy from the hot gases leaving the combustor. Some of this energy is used to drive the compressor, and in some turbine engines (ie turboprop, turboshaft or turbofan engines), energy is extracted by additional turbine discs and used to drive devices such as propellers, bypass fans or helicopter rotors. One type, a free turbine, is configured such that the turbine disc driving the compressor rotates independently of the discs that power the external components. Relatively cool air, bled from the compressor, may be used to cool the turbine blades and vanes, to prevent them from melting.
Afterburner or reheat (chiefly UK) — (mainly military) Produces extra thrust by burning extra fuel, usually inefficiently, to significantly raise Nozzle Entry Temperature at the exhaust. Owing to a larger volume flow (i.e. lower density) at exit from the afterburner, an increased nozzle flow area is required, to maintain satisfactory engine matching, when the afterburner is alight.
Exhaust or Nozzle — Hot gases leaving the engine exhaust to atmospheric pressure via a nozzle, the objective being to produce a high velocity jet. In most cases, the nozzle is convergent and of fixed flow area.
Supersonic nozzle — If the Nozzle Pressure Ratio (Nozzle Entry Pressure/Ambient Pressure) is very high, to maximize thrust it may be worthwhile, despite the additional weight, to fit a convergent-divergent (de Laval) nozzle. As the name suggests, initially this type of nozzle is convergent, but beyond the throat (smallest flow area), the flow area starts to increase to form the divergent portion. The expansion to atmospheric pressure and supersonic gas velocity continues downstream of the throat, whereas in a convergent nozzle the expansion beyond sonic velocity occurs externally, in the exhaust plume. The former process is more efficient than the latter.

The various components named above have constraints on how they are put together to generate the most efficiency or performance. The performance and efficiency of an engine can never be taken in isolation; for example fuel/distance efficiency of a supersonic jet engine maximises at about mach 2, whereas the drag for the vehicle carrying it is increasing as a square law and has much extra drag in the transonic region. The highest fuel efficiency for the overall vehicle is thus typically at Mach ~0.85.

For the engine optimisation for its intended use, important here is air intake design, overall size, number of compressor stages (sets of blades), fuel type, number of exhaust stages, metallurgy of components, amount of bypass air used, where the bypass air is introduced, and many other factors. For instance, let us consider design of the air intak

WHO IS AN ASTRONAUT..??

2009-08-26T13:57:00.002+05:30

ASTRONAUT:

The term "astronaut" derives from the Greek words meaning "space sailor," and refers to all who have been launched as crew members aboard NASA spacecraft bound for orbit and beyond. Since the inception of NASA's human space flight program, we have also maintained the term "astronaut" as the title for those selected to join the NASA corps of astronauts who make "space sailing" their career profession. The term "cosmonaut" refers to those space sailors who are members of the Russian space program.

The crew of each launched spacecraft is made up of astronauts or cosmonauts drawn from the various categories described in these pages. The crew assignments and duties of commander, pilot, space shuttle mission specialist, or International Space Station flight engineer are drawn from the NASA professional career astronauts. A special category of astronauts typically titled "payload specialist" refers to individuals selected and trained by commercial or research organizations for flights of a specific payload on a space flight mission. At the present time, these payload specialists may be cosmonauts or astronauts designated by the international partners, individuals selected by the research community, or a company or consortia flying a commercial payload aboard the spacecraft.

SPACE PROPULSION 3- ADVANCES

2009-08-26T13:51:00.002+05:30

SPACE PROPULSION-3

Advanced Solid Rocket Booster

NASA was planning on replacing the post-Challenger SRBs with a new Advanced Solid Rocket Booster (ASRB) to be built by NASA itself at a new facility, on the location of a canceled Tennessee Valley Authority nuclear power plant, at Yellow Creek, Mississippi. The ASRB would have produced additional force in order to increase shuttle payload, so that it could carry modules and construction components to the ISS. After an expenditure of over $2 billion USD, the ASRBs were canceled in favor of the "Super Light-weight Tank" (SLWT) that is in use now, replacing the light-weight tank design that was used on earlier flights.

Two ASRB casings can be found on the Space Shuttle Pathfinder on display at the United States Space & Rocket Center in Huntsville, Alabama.

Filament-wound cases

In the need to provide the necessary thrust to launch polar-orbiting shuttles from the SLC-6 launch pad at Vandenberg Air Force Base in California, SRBs using filament-wound cases (FWC) were designed to be more lightweight than the steel cases used on KSC-launched SRBs.[7] Unlike the regular SRBs, which had the flawed field joint design that led to the Challenger Disaster in 1986, the FWC boosters had the "double tang" joint design (necessary to keep the boosters properly in alignment during the "twang" movement when the SSMEs are ignited prior to liftoff), but used the two O-ring seals. With the closure of SLC-6, the FWC boosters were scrapped by ATK and NASA, but their field joints, albeit modified to incorporate the current three O-ring seals and joint heaters, were later incorporated into the present-day field joints on the current SRMs.

Five-segment booster

Prior to the destruction of the Space Shuttle Columbia in 2003, NASA investigated the replacement of the current 4-segment RSRMs with either a 5-segment SRB design or replacing them altogether with liquid "flyback" boosters using either Atlas V or Delta IV EELV technologies. The 5-segment SRB, which would have required little change to the current shuttle infrastructure, would have allowed the space shuttle to carry an additional 20,000 lb (9,100 kg) of payload in an International Space Station-inclination orbit, eliminate the dangerous "Return-to-Launch Site" and "Trans-Oceanic Abort" modes, and even fly polar-orbiting missions from Kennedy Space Center using a so-called "dog-leg" maneuver over the Atlantic Ocean. With the destruction of the Columbia, NASA has shelved the 5-segment SRB for the shuttle program, but resurrected it for the Ares I and Ares V boosters for Project Constellation.

Future and proposed uses

NASA plans to reuse the SRB designs and infrastructure in several Ares rockets. In 2005, NASA announced the Shuttle-Derived Launch Vehicle slated to carry the Orion Crew Exploration Vehicle into low-Earth orbit and later to the Moon. The SRB-derived Crew Launch Vehicle (CLV), named Ares I, originally featured a modified 4-segment SRB for its first stage, while a liquid-fueled second stage, powered by a single main engine, would have propelled the Orion into orbit. Its current design, initially introduced in 2006, and since modified, is to feature the originally planned, but scrapped 5-segment SRB first-stage, with a second stage powered by an Apollo-derived J-2X rocket engine. In place of the standard SRB nosecone, Ares I will have a tapered interstage assembly connecting the booster proper with the second stage, an inflatable ring to counter the end-over-end spinning, and larger, heavier parachutes to lower the stage into the Atlantic Ocean for recovery.

Also introduced in 2005, was a heavy-lift Cargo Launch Vehicle (CaLV) named Ares V. Early designs of the Ares V utilized five SSMEs and a pair of 5-segment boosters like those planned for the pre-Columbia upgrades, but since then NASA had redesigned the vehicle using first five, and now six RS-68B rocket engines, with either the originally-planned 5-segment boosters or a pair of 5.5-segment boosters (similar to the 5.5-segment booster configuration on the now-retired Titan 34-D/Centaur rocket used to launch the Viking and Voyager spacecrafts in the mid-1970s).

The current redesign will make the booster taller and more powerful than the now-retired Saturn V, N-1, and Energia rockets, and will allow the Ares V to place both the Earth Departure Stage and Altair spacecraft into Low-Earth orbit for later on-orbit assembly. Unlike the 5-segment SRB for the Ares I, the 5 or 5.5-segment boosters for the Ares V are to be identical in design, construction, and function to the current SRBs except for the extra segments. Although there is no final decision on the recovery or reuse of this system, but it is most likely that the standard recovery process like that employed on the shuttle will be used. Like the current shuttle boosters, the Ares V boosters will fly an almost-identical flight trajectory from launch to splashdown.

The DIRECT proposal for a new, shuttle-derived launch vehicle, unlike the Ares I and Ares V boosters, uses a pair of classic 4-segment SRBs with the existing RS-68 engines used on the Delta IV EELV rocket.

SPACE PROPULSION-2

2009-08-26T13:45:00.004+05:30

SPACE PROPULSION-2:

FUNCTION:

1. Ignition

SRB ignition can occur only when a manual lock pin from each SRB safe and arm device has been removed. The ground crew removes the pin during prelaunch activities. At T minus five minutes, the SRB safe and arm device is rotated to the arm position. The solid rocket motor ignition commands are issued when the three Space Shuttle Main Engines (SSMEs) are at or above 90-percent rated thrust, no SSME fail and/or SRB ignition Pyrotechnic Initiator Controller (PIC) low voltage is indicated and there are no holds from the Launch Processing System (LPS).

The solid rocket motor ignition commands are sent by the orbiter computers through the Master Events Controllers (MECs) to the safe and arm device NSDs in each SRB. A PIC single-channel capacitor discharge device controls the firing of each pyrotechnic device. Three signals must be present simultaneously for the PIC to generate the pyro firing output. These signals — arm, fire 1 and fire 2 — originate in the orbiter general-purpose computers (GPCs) and are transmitted to the MECs. The MECs reformat them to 28 volt DC signals for the PICs. The arm signal charges the PIC capacitor to 40 volts DC (minimum of 20 volts DC).

The GPC launch sequence also controls certain critical main propulsion system valves and monitors the engine ready indications from the SSMEs. The MPS start commands are issued by the onboard computers at T minus 6.6 seconds (staggered start engine three, engine two, engine one all approximately within 0.25 of a second), and the sequence monitors the thrust buildup of each engine. All three SSMEs must reach the required 90% thrust within three seconds; otherwise, an orderly shutdown is commanded and safing functions are initiated.

Normal thrust buildup to the required 90% thrust level will result in the SSMEs being commanded to the lift off position at T minus three seconds as well as the fire 1 command being issued to arm the SRBs. At T minus three seconds, the vehicle base bending load modes are allowed to initialize (movement of approximately 25.5 in (650 mm) measured at the tip of the external tank, with movement towards the external tank).

The fire 2 commands cause the redundant NSDs to fire through a thin barrier seal down a flame tunnel. This ignites a pyro booster charge, which is retained in the safe and arm device behind a perforated plate. The booster charge ignites the propellant in the igniter initiator; and combustion products of this propellant ignite the solid rocket motor initiator, which fires down the entire vertical length of the solid rocket motor igniting the solid rocket motor propellant along its entire surface area instantaneously.

Range safety system

A range safety system (RSS) provides for destruction of a rocket or part of it with on-board explosives by remote command if the rocket is out of control, in order to limit the danger to people on the ground from crashing pieces, explosions, fire, poisonous substances, etc. To date, the RSS has only been activated once - during the Space Shuttle Challenger disaster (37 seconds after the breakup of the vehicle).

The shuttle vehicle has two RSSs, one in each SRB. Both are capable of receiving two command messages (arm and fire) transmitted from the ground station. The RSS is used only when the shuttle vehicle violates a launch trajectory red line.

An RSS consists of two antenna couplers, command receivers/decoders, a dual distributor, a safe and arm device with two NASA standard detonators (NSD), two confined detonating fuse manifolds (CDF), seven CDF assemblies and one linear-shaped charge (LSC).

The antenna couplers provide the proper impedance for radio frequency and ground support equipment commands. The command receivers are tuned to RSS command frequencies and provide the input signal to the distributors when an RSS command is sent. The command decoders use a code plug to prevent any command signal other than the proper command signal from getting into the distributors. The distributors contain the logic to supply valid destruct commands to the RSS pyrotechnics.

The NSDs provide the spark to ignite the CDF, which in turn ignites the LSC for shuttle vehicle destruction. The safe and arm device provides mechanical isolation between the NSDs and the CDF before launch and during the SRB separation sequence.

The first message, called arm, allows the onboard logic to enable a destruct and illuminates a light on the flight deck display and control panel at the commander and pilot station. The second message transmitted is the fire command.

The SRB distributors in the SRBs are cross-strapped together. Thus, if one SRB received an arm or destruct signal, the signal would also be sent to the other SRB.

A command is sent from the orbiter to the SRB just before separation to apply battery power to the recovery logic network. A second, simultaneous command arms the three nose cap thrusters (for deploying the pilot and drogue parachutes), the frustum ring detonator (for main parachute deployment), and the main parachute disconnect ordinance.

The recovery sequence begins with the operation of the high-altitude baroswitch, which triggers the pyrotechnic nose cap thrusters. This ejects the nose cap, which deploys the pilot parachute. Nose cap separation occurs at a nominal altitude of 15,704 ft (4,787 m), about 218 seconds after SRB separation. The 11.5 ft (3.5 m) diameter conical ribbon pilot parachute provides the force to pull lanyards attached to cut knives, which cut the loop securing the drogue retention straps. This allows the pilot chute to pull the drogue pack from the SRB, causing the drogue suspension lines to deploy from their stored position. At full extension of the twelve 105 ft (32 m) suspension lines, the drogue deployment bag is stripped away from the canopy, and the 54 ft (16 m) diameter conical ribbon drogue parachute inflates to its initial reefed condition. The drogue disreefs twice after specified time delays (using redundant 7 and 12-second reefing line cutters), and it reorients/stabilizes the SRB for main chute deployment. The drogue parachute has a design load of approximately 315,000 lb (143,000 kg) and weighs approximately 1,200 lb (540 kg).

After the drogue chute has stabilized the SRB in a tail-first attitude, the frustum is separated from the forward skirt by a pyrotechnic charge triggered by the low-altitude baroswitch at a nominal altitude of 5,500 ft (1,700 m) about 243 seconds after SRB separation. The frustum is then pulled away from the SRB by the drogue chute. The main chute suspension lines are pulled out from deployment bags that remain in the frustum. At full extension of the lines, which are 203 ft (62 m) long, the three main chutes are pulled from their deployment bags and inflate to their first reefed condition. The frustum and drogue parachute continue on a separate trajectory to splashdown. After specified time delays (using redundant 10 and 17-second reefing line cutters), the main chute reefing lines are cut and the chutes inflate to their second reefed and full open configurations. The main chute cluster decelerates the SRB to terminal conditions. Each of the 136 ft (41 m) diameter, 20-degree conical ribbon parachutes have a design load of approximately 195,000 lb (88,000 kg) and each weighs approximately 2,180 lb (990 kg). These chutes are the largest that have ever been used — both in deployed size and load weight. The RSRM nozzle extension is severed by a pyrotechnic charge about 20 seconds after frustum separation.

Water impact occurs about 279 seconds after SRB separation at a nominal velocity of 76 feet per second (23 m/s). The water impact range is approximately 130 nmi (240 km) off the eastern coast of Florida. Because the parachutes provide for a nozzle-first impact, air is trapped in the empty (burned out) motor casing, causing the booster to float with the forward end approximately 30 feet (9.1 m) out of the water.

Solid rocket booster of the STS-114 mission being recovered and transported to Cape Canaveral.

Formerly, the main chutes were released from the SRB at impact using a parachute release nut ordnance system (residual loads in the main chutes would deploy the parachute attach fittings with floats tethered to each fitting). The current design keeps the main chutes attached during water impact (initial impact and slapdown). Salt Water Activated Release (SWAR) devices are now incorporated into the main chute riser lines to simplify recovery efforts and reduce damage to the SRB.The drogue deployment bag/pilot parachutes, drogue parachutes and frustums, each main chute, and the SRBs are buoyant and are recovered.

CHALLENGER DISASTER:

The Challenger accident originated from one of the SRBs. The cause of the accident was found by the Rogers Commission Report to be due to faulty design of the SRB joints.

During the subsequent downtime, detailed structural analyses were performed on critical structural elements of the SRB. Analyses were primarily focused in areas where anomalies had been noted during postflight inspection of recovered hardware.

One of the areas was the attachment ring where the SRBs are connected to the external tank. Areas of distress were noted in some of the fasteners where the ring attaches to the SRB motor case. This situation was attributed to the high loads encountered during water impact. To correct the situation and ensure higher strength margins during ascent, the attach ring was redesigned to encircle the motor case completely (360 degrees). Previously, the attachment ring formed a 'C' shape and encircled the motor case just 270 degrees.

Additionally, special structural tests were performed on the aft skirt. During this test program, an anomaly occurred in a critical weld between the hold-down post and skin of the skirt. A redesign was implemented to add reinforcement brackets and fittings in the aft ring of the skirt.

These two modifications added approximately 450 lb (200 kg) to the weight of each SRB. The result is called a "Redesigned Solid Rocket Motor" (RSRM).

Space Shuttle Solid Rocket Booster

2009-08-26T11:26:00.003+05:30

Space Shuttle Solid Rocket Booster:
The Space Shuttle Solid Rocket Boosters (SRBs) are the pair of large solid rockets used by the space shuttle during the first two minutes of powered flight. Together they provide about 83% of liftoff thrust for the Space Shuttle. They are located on either side of the orange external propellant tank. Each SRB produces 80% more liftoff thrust than one F-1 engine, the most powerful single-chamber liquid-fueled rocket engine ever flown — 5 of which powered the Saturn V "moon rocket's" first stage. The SRBs are the largest solid-fuel rocket motors ever flown, and the first to be used for primary propulsion on human spaceflight missions.The spent SRBs are recovered from the ocean, refurbished, reloaded with propellant, and reused for several missions. The prime contractor for the SRBs and the manufacturer of the vital solid fuel rocket segments is the Thiokol Corporation of Brigham City, Utah. SRBs are reused many times, for example a SRB from STS-1 flew 48 times into space over 30 years, and in 2009 was used as an Ares I test engine.
The two reusable SRBs provide the main thrust to lift the shuttle off the launch pad and up to an altitude of about 150,000 ft (28 mi; 46 km). While on the pad, the two SRBs carry the entire weight of the external tank and orbiter and transmit the weight load through their structure to the mobile launch platform. Each booster has a liftoff thrust of approximately 2,800,000 pounds-force (12.5 MN) at sea level, increasing shortly after liftoff to about 3,100,000 lbf (13.8 MN). They are ignited after the three space shuttle main engines' thrust level is verified. Seventy five seconds after SRB separation, SRB apogee occurs at an altitude of approximately 220,000 ft (67 km); parachutes are then deployed and impact occurs in the ocean approximately 122 nautical miles (226 km) downrange, after which the two SRBs are recovered. The SRBs are the largest solid-propellant motors ever flown and the first of such large rockets designed for reuse. Each is 149.16 ft (45.46 m) long and 12.17 ft (3.71 m) in diameter. Each SRB weighs approximately 1,300,000 lb (590,000 kg) at launch. The two SRBs constitute about 60% of the total lift-off mass. The propellant for each solid rocket motor weighs approximately 1,100,000 lb (500,000 kg). The inert weight of each SRB is approximately 200,000 lb (91,000 kg).
COMPONENTS:
Hold-down posts Each solid rocket booster has four hold-down posts that fit into corresponding support posts on the mobile launcher platform. Hold-down bolts hold the SRB and launcher platform posts together. Each bolt has a nut at each end, the top one being a frangible nut. The top nut contains two NASA standard detonators (NSDs), which are ignited at solid rocket motor ignition commands. When the two NSDs are ignited at each hold down, the hold-down bolt travels downward because of the release of tension in the bolt (pretensioned before launch), NSD gas pressure and gravity. The bolt is stopped by the stud deceleration stand, which contains sand. The SRB bolt is 28 in (710 mm) long and is 3.5 in (89 mm) in diameter. The frangible nut is captured in a blast container. In the event of a hold down failure the thrust from SRB ignition is enough to break the bolts, freeing the vehicle. The solid rocket motor ignition commands are issued by the orbiter's computers through the master events controllers to the hold-down pyrotechnic initiator controllers (PICs) on the mobile launcher platform. They provide the ignition to the hold-down NSDs. The launch processing system monitors the SRB hold- down PICs for low voltage during the last 16 seconds before launch. PIC low voltage will initiate a launch hold. Electrical power distribution Electrical power distribution in each SRB consists of orbiter supplied main DC bus power to each SRB via SRB buses labeled A, B and C. orbiter main DC buses A, B and C supply main DC bus power to corresponding SRB buses A, B and C. In addition, orbiter main DC bus C supplies backup power to SRB buses A and B, and orbiter bus B supplies backup power to SRB bus C. This electrical power distribution arrangement allows all SRB buses to remain powered in the event one orbiter main bus fails. The nominal operating voltage is 28±4 volts DC
HYDRAULIC POWER UNITS:
There are two self-contained, independent Hydraulic Power Units (HPUs) on each SRB. Each HPU consists of an auxiliary power unit (APU), fuel supply module, hydraulic pump, hydraulic reservoir and hydraulic fluid manifold assembly. The APUs are fueled by hydrazine and generate mechanical shaft power to drive a hydraulic pump that produces hydraulic pressure for the SRB hydraulic system. The two separate HPUs and two hydraulic systems are located on the aft end of each SRB between the SRB nozzle and aft skirt. The HPU components are mounted on the aft skirt between the rock and tilt actuators. The two systems operate from T minus 28 seconds until SRB separation from the orbiter and external tank. The two independent hydraulic systems are connected to the rock and tilt servoactuators. The HPU controller electronics are located in the SRB aft integrated electronic assemblies on the aft external tank attach rings. The HPUs and their fuel systems are isolated from each other. Each fuel supply module (tank) contains 22 lb (10.0 kg) of hydrazine. The fuel tank is pressurized with gaseous nitrogen at 400 psi (2.8 MPa), which provides the force to expel (positive expulsion) the fuel from the tank to the fuel distribution line, maintaining a positive fuel supply to the APU throughout its operation. In the APU, a fuel pump boosts the hydrazine pressure and feeds it to a gas generator. The gas generator catalytically decomposes the hydrazine into hot, high-pressure gas; a two-stage turbine converts this into mechanical power, driving a gearbox. The waste gas, now cooler and at low pressure, is passed back over the gas generator housing to cool it before being dumped overboard. The gearbox drives the fuel pump, its own lubrication pump, and the HPU hydraulic pump. As described so far, the system could not self-start, since the fuel pump is driven by the turbine it supplies fuel to. Accordingly, a bypass line goes around the pump and feeds the gas generator using the nitrogen tank pressure until the APU speed is such that the fuel pump outlet pressure exceeds that of the bypass line, at which point all the fuel is supplied to the fuel pump.
THRUST VECTORING:
Each SRB has two hydraulic gimbal servoactuators: one for roll and one for tilt. The servoactuators provide the force and control to gimbal the nozzle for thrust vector control. The space shuttle ascent thrust vector control portion of the flight control system directs the thrust of the three shuttle main engines and the two SRB nozzles to control shuttle attitude and trajectory during lift- off and ascent. Commands from the guidance system are transmitted to the ATVC (Ascent Thrust Vector Control) drivers, which transmit signals proportional to the commands to each servoactuator of the main engines and SRBs. Four independent flight control system channels and four ATVC channels control six main engine and four SRB ATVC drivers, with each driver controlling one hydraulic port on each main and SRB servoactuator. Each SRB servoactuator consists of four independent, two- stage servovalves that receive signals from the drivers. Each servovalve controls one power spool in each actuator, which positions an actuator ram and the nozzle to control the direction of thrust. The four servovalves in each actuator provide a force summed majority voting arrangement to position the power spool. With four identical commands to the four servovalves, the actuator force-sum action prevents a single erroneous command from affecting power ram motion. If the erroneous command persists for more than a predetermined time, differential pressure sensing activates a selector valve to isolate and remove the defective servovalve hydraulic pressure, permitting the remaining channels and servovalves to control the actuator ram spool. Failure monitors are provided for each channel to indicate which channel has been bypassed. An isolation valve on each channel provides the capability of resetting a failed or bypassed channel.
Rate gyro assemblies Each SRB contains two Rate gyro assemblies (RGAs), with each RGA containing one pitch and one yaw gyro. These provide an output proportional to angular rates about the pitch and yaw axes to the orbiter computers and guidance, navigation and control system during first-stage ascent flight in conjunction with the orbiter roll rate gyros until SRB separation. At SRB separation, a switchover is made from the SRB RGAs to the orbiter RGAs. The SRB RGA rates pass through the orbiter flight aft multiplexers/demultiplexers to the orbiter GPCs. The RGA rates are then mid-value-selected in redundancy management to provide SRB pitch and yaw rates to the user software. The RGAs are designed for 20 missions. Propellant The propellant mixture in each SRB motor consists of ammonium perchlorate (oxidizer, 69.6% by weight), aluminum (fuel, 16%), iron oxide (a catalyst, 0.4%), a polymer (such as PBAN or HTPB, serving as a binder that holds the mixture together and acting as secondary fuel, 12.04%), and an epoxy curing agent (1.96%). This propellant is commonly referred to as Ammonium Perchlorate Composite Propellant, or simply APCP. This mixture develops a specific impulse of 242 seconds at sea level or 268 seconds in a vacuum. The main fuel, aluminum is used because it has a reasonable specific energy density of about 31.0MJ/kg, but having a high volumetric energy density, as well as being difficult to accidentally ignite. The propellant is an 11-point star-shaped perforation in the forward motor segment and a double-truncated-cone perforation in each of the aft segments and aft closure. This configuration provides high thrust at ignition and then reduces the thrust by approximately a third 50 seconds after lift-off to avoid overstressing the vehicle during maximum dynamic pressure