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Friday, April 9, 2010


F-35B Joint Strike Fighter (JSF)

The F-35B for the US Marine Corps and the UK Royal Air Force and Royal Navy employs a short-takeoff/vertical-landing (STOVL) capability. This takeoff and landing operation succeeds through a very innovative technology known as the shaft-driven lift fan propulsion system. Besides the propulsion system, the STOVL variant differs only slightly from the US Air Force variant.

The short takeoff/vertical landing (STOVL) F-35B will replace the aging AV-8B Harrier STOVL attack jets (which have also proven increasingly difficult to support) of the US Marine Corps, as well as its F/A-18s. The F-35B will have a stealthy, belly-mounted 25 mm missionized gun pod and a combat radius of more than 450 NM- nearly two times that of legacy STOVL strike fighters. A shaft-driven lift fan, in combination with a vectoring rear exhaust nozzle, gives this fighter the ability to take off in short distances, accelerate to supersonic speeds in level flight, and land vertically. Thanks to the lift-fan system, the F-35B's total vertical lifting thrust is about 39,700 pounds (the aircraft weighs about 30,000 pounds)- more than 14,000 pounds greater than the engine alone would produce without the lift fan. The F-35B will be the world's first operational supersonic STOVL aircraft.

It carries a refueling probe fitted into the right side of the forward fuselage, rather than the U.S. Air Force standard refueling receptacle normally located on the top surface of the aircraft. The STOVL variant carries no internal gun, though a missionized external gun is an option. It shares all the electronic gear of the U.S. Air Force variant, and virtually an identical cockpit layout except for a lever to switch between wingborne and jetborne modes. Performance and stealth characteristics are also very similar. The STOVL variant, designed to replace the AV-8B Harrier, has more than twice the range on internal fuel, operates at supersonic conditions, and houses internal weapons.

The Marine variant distinguishes itself from the other variants with its short takeoff/vertical landing capability. As the first requirement for achieving this capability, the airplane must have more vertical lift than weight. While that requirement is obvious, it is sometimes difficult to meet. The airplane must be light and have a high thrust-to-weight ratio. Good controllability in every axis of the airplane at zero airspeed is a second requirement. The transition between up-and-away flight and hover must be carefully considered. The airplane's hover footprint, the propulsion system's impact on the ground surface or carrier deck, is just as critical.

The manner in which thrust is developed is the key to producing a benign footprint. Noise levels and heat effects on the deck and on the aircraft itself are factors that must be considered. Pointing engine thrust directly down produces a tremendous amount of reflected energy, which results in all kinds of effects that can shorten the life of structures. Acoustic considerations are material considerations. They affect material choices for the underside of the airplane as well as for structures and payloads attached to the airplane.

Internal weapon carriage and increased range requirements on internal fuel make the JSF somewhat bigger and heavier than a Harrier. Russia's Yakovlev Design Bureau worked on a similar-sized STOVL fighter in the 1980s. This aircraft, the Yak-141, followed the Russians' successful, Harrier-sized Yak-38 STOVL aircraft. For vertical lift, the Yak-141 used two RD-41 jet engines mounted in tandem behind the cockpit and a thrust-vectoring main engine. The aircraft first flew in 1989. According to published reports, the Yak-141 encountered problems with hot gas ingestion in the vertical mode. Although Yakovlev built several Yak-141 prototypes, the program was never funded through to the operational aircraft stage and was reportedly shelved in 1992.

The design provides extra thrust in the vertical mode with a shaft-driven lift fan produced by Rolls-Royce. This propulsion approach, which is patented by Dr. Paul Bevilaqua of the Skunk Works, circumvents the hover problems associated with high-temperature and high-velocity air by providing much of the downward thrust with cool air from the lift fan.

The Rolls Royce lift fan is driven by a drive shaft connected to the main engine. Doors open above and below the vertical fan as it spins up. The rest of the vertical thrust is provided by a three-bearing exhaust nozzle on the main engine and two roll posts on the wings. The exhaust nozzle, provided by Rolls-Royce, is used for lift and yaw control and can swivel 110 degrees downward from the horizontal. Thrust for the roll posts, used for roll control, is supplied from the main engine's fan section. This thrust comes from cooler air that normally bypasses the engine's turbine section. The lift-fan approach removes energy from the hot turbine section of the main engine, which, in turn, lowers the main engine's exhaust temperature, producing an even cooler footprint.

The powered model, which is 86 percent scale, was produced by the Skunk Works. The model was used in outdoor hover testing at NASA/Ames in California last year to verify the basic STOVL operational concept and confirm the expected performance of the lift-fan system. The model was then used in extensive testing in the NASA/Ames 80- by 120-foot wind tunnel earlier this year. No other JSF competitor has accomplished a comparable degree of concept demonstration or risk-reduction for their vertical lift systems. Other small-scale wind tunnel models of the Lockheed Martin aircraft have undergone testing in other facilities around the country and in the United Kingdom.

Aside from the shaft-driven lift fan, the Marine variant is much like the Air Force variant. The aircraft has slightly shorter range because the fan system consumes space used for some of the fuel in the Air Force variant. Still, the aircraft has more than twice the range of an AV-8B on internal fuel and can carry a bigger payload. The aircraft shares all of the electronic gear of the Air Force variant. Cockpit layout is also virtually identical, with the exception of a thrust-vector lever for the hover mode.

From October 2000 through August 2001, the JSF X-35 demonstrator aircraft established a number of flight-test standards. X-35B STOVL- first and only aircraft in history to achieve a short-takeoff, level supersonic dash and vertical landing in a single flight; first aircraft to integrate and fly a shaft-driven lift-fan propulsion system; logged 17 vertical takeoffs, 14 short takeoffs, 27 vertical landings, and five supersonic flights.

The LHA(R) will replace the LHA 1 class of amphibious assault ships, and will have the flexibility to operate in the traditional role as the fl agship for an Expeditionary Strike Group as well as potentially playing a key role in the maritime pre-positioning force future (MPF(F)). As the Navy's Seabasing plan matures, the flexibility to operate with the Expeditionary Strike Group and as part of the MPF(F) will make the LHA(R) a vital cog in the Sea Base. LHA(R) will be a variant of the gas turbine-powered LHD 8. The one key difference of LHA(R) from LHD 8 is that it will be an aviation-enhanced assault ship tailored for the US Marine Corps future Aviation Combat Element centered on the STOVL F-35B Joint Strike Fighter and the tilt-rotor V-22 Osprey.

LHA 6, the first ship of the LHA(R) program, will be able to operate and support a detachment of 20+ Joint Strike Fighters. LHA 6 features several aviation capabilities enhanced beyond previous amphibious assault ships. These include an enlarged hangar deck, realignment and expansion of the aviation maintenance facilities, a significant increase in available stowage for parts and support equipment, and increased aviation fuel capacity.

DoD working groups and conferences began to question community acceptance strategies for some new weapons systems. In particular, the Joint Strike Fighter may face a variety of challenges in several potential beddown locations. The aircraft generates an extraordinary amount of thrust from its single engine, and according to preliminary analyses, does so at some cost in noise and air quality. Preliminary analysis of the San Diego area revealed air quality limitations that may preclude unrestricted operation of the STOVL (Short Takeoff, Vertical Landing) version of the aircraft that will be procured by the USMC. The highest thrust settings for the aircraft's F-119 engine will occur during transition to and from vertical flight. Noise and emissions, especially of oxides of Nitrogen (NOx), may exceed those encountered in any equivalent engine.

Overall, the JSF Basing & Shipboard Suitability IPT is responsible for ensuring that the requirements are met. The JSF must be able to operate from US and allied shore-based facilities. The JSF STOVL aircraft must be able to operate from austere sites. The naval variant of the JSF must be compatible with and operationally supportable from CVN-68 (NIMITZ) class carriers.

The USMC STOVL aircraft must be compatible with and operationally supportable from CVN-68 (NIMITZ), LHA (TARAWA), and LHD (WASP) Class Ships. The UK STOVL aircraft must be compatible with the flight, ramp, and hangar deck layouts of CVS (INVINCIBLE) Class Ships.

The JSF B&SS IPT is also responsible for assisting international partners in incorporating the JSF into their basing options on land and at sea. For Italian partners, this means the JSF will be operating from their current aircraft carrier, the Garibaldi. In the near future, the JSF will be operating from their new carrier, the Andrea Doria.

As of 2002 the Marine Corps planned to deploy 609 F-35Bs. STOVL first flight was to be in early 2006, with firs delivery in 2008, and IOC 2010. The Marine Corps, with an IOC planned for 2010, would be the first of the military services to operate a fleet of F-35s.

By February 2004, dark clouds were gathering, and it was clear that the team was sailing into stormy technical waters. As detailed design progressed, weight estimates from early in the design phase were found to be overly optimistic. Program leadership was soon faced with the grim reality that the short takeoff/vertical landing (STOVL) variant would need to lose as much as 3,000 pounds to meet performance requirements. This was a sobering development, and there were more than a few who said that a fix was either impossible or too expensive and time-consuming.

The Joint Strike Fighter (JSF) program entered a re-plan phase as a result of a number of technical issues with aircraft design (principally with aircraft weight of the Short Take-Off and Vertical Landing (STOVL) variant). The STOVL aircraft is considered to be the linchpin to the program's success. These technical issues resulted in an acknowledged minimum slip to the IOC dates for the three aircraft variants of up to two years.

There is no weight requirement for the F-35 - only performance requirements. The CTOL and CV versions of the F-35 already met their performance requirements, and initiatives were taken to ensure that the STOVL version meets its performance requirements by the time it enters service. The contractors created a "SWAT" team. SWAT stands for STOVL Weight Attack Team. The team, comprising about 500 individuals, was dedicated solely to reducing weight, and identified and removed hundreds of pounds of unwanted weight from the aircraft in the process of maturing the airframe.

SWAT identified a design path to a STOVL F-35 that meets or exceeds its performance requirements. The team not only excised more than 3,000 pounds of unwanted estimated weight, but also improved structural integrity, optimized load paths and brought greater efficiencies to the overall aircraft. The internal bays of the F-35B STOVL variant were redesigned in late 2004 and are now shorter and reduced in width, compared to the F-35A CTOL model. This was done to reduce the weight of the F-35B to meet other more important performance goals. As a result, the F-35B is no longer compatible with JSOW and 2,000-lb JDAM weapons. The largest weapon this F-35 variant can carry internally is the GBU-32 1,000-lb version of JDAM.

Propulsion engineers, meanwhile, made adjustments to the F-35B's auxiliary engine inlet and exhaust nozzle to improve thrust by more than 600 pounds without making changes to the engine itself or the way it operates. All of this was accomplished in about six months - far shorter than anyone had predicted. Because of their shared basic architecture, all three F-35 variants will benefit from the SWAT-generated design enhancements.

In February 2006 BAE Systems started production of the first U.K. components for the Short Take-Off / Vertical Landing (STOVL) variant of the F-35 Joint Strike Fighter. BAE Systems' Advanced Machining Centre at Samlesbury, U.K. has started work on one of the major frames that form part of the aft fuselage. The aft fuselage and empennage for each F-35 JSF are being designed, engineered and built at the company's Samlesbury site, using the latest in advanced design and manufacturing technology.

As of early 2005 there was uncertainty about the number and mix of variants the services plan to purchase will also affect JSF's acquisition plans. While the Air Force had announced its intention to acquire the short takeoff and vertical landing variant, it had yet to announce when or how many it expects to buy or how this purchase will affect the quantity of the conventional takeoff and landing variant it plans to buy. In December 2004, Air Combat Command officials indicated that the Air Force was considering buying about 250 short takeoff and landing JSFs and about 1,300 conventional takeoff and landing JSFs. However, these numbers were not official.

The number and mix of JSF variants that the Navy and Marine Corps intend to purchase - and their related procurement costs - also remain undetermined. In 2002 the Navy - concerned that it could not afford the number of tactical aircraft it planned to purchase - reduced the number of JSF aircraft for joint Navy and Marine Corps operations from 1,089 to 680 by reducing the number of backup aircraft needed. News reports in 2002 indicated that the proposed reduction would cut 259 jets from the Marine Corps buy, and 50 from the Navy purchase, resulting in a total F-35B buy of 350. However, as of early 2005 the Navy had not indicated to the developer the exact mix of the carrier and short takeoff and vertical landing variants it intended to purchase.

The United Kingdom's Ministry of Defence has chosen the F-35B to replace its Harrier GR.7s and Sea Harriers for the Royal Air Force and Royal Navy. The United Kingdom's 2005 plans called for 150 aircraft: the Royal Air Force 90; and the Royal Navy 60.

June 10, 2009.                                                                                       mtb0minime

Real World Facts: Mountain Hydrology Edition!
In an effort to make this serious thread serious, I have uploaded a copy of a report I did last spring. Since it's much too long to post here, as well as containing pertinent pictures, graphs, and tables, you can click this link to download and view the report. I implore you not to call me a "noob" because I and several others did in fact "do a research" for nearly a week up in the mountains.

A fax (short for facsimile) is a document sent over a telephone line. Fax machines have existed, in various forms, since the 19th century (see "History" below), though modern fax machines became feasible only in the mid-1970s as the sophistication increased and cost of the three underlying technologies dropped. Digital fax machines first became popular in Japan, where they had a clear advantage over competing technologies like the teleprinter, since at the time (before the development of easy-to-use input method editors) it was faster to handwrite kanji than to type the characters. Over time, faxing gradually became affordable, and by the mid-1980s, fax machines were very popular around the world.

Although businesses usually maintain some kind of fax capability, the technology has faced increasing competition from Internet-based alternatives. However, fax machines still retain some advantages, particularly in the transmission of sensitive material which, if sent over the Internet unencrypted may be vulnerable to interception. In some countries, because electronic signatures on contracts are not recognized by law while faxed contracts with copies of signatures are, fax machines enjoy continuing support in business.[citation needed]

In many corporate environments, standalone fax machines have been replaced by "fax servers" and other computerized systems capable of receiving and storing incoming faxes electronically, and then routing them to users on paper or via an email (which may be secured). Such systems have the advantage of reducing costs by eliminating unnecessary printouts and reducing the number of inbound analog phone lines needed by an office.

how to build a skyscraper?

mtb0minime wrote:

eleven bravo wrote:

how to build a skyscraper?

Do a reaserch n00b, I can't do all the work around here

do a report on how to do a research n00b

mtb0minime wrote:

m3thod wrote:

tell me how to build a bridge noob

Here. You just got owned, noob.

al qaeda thanks you for your co-operation.

lexus nexus