7. X-43A Hyperplane (Seminar Hyperplanes)

Three views diagram of X-43A Hyperplane

It will be the first time that a non-rocket propelled; air-breathing engine has powered a vehicle in flight at hypersonic speeds, or more than five times the speed of sound. An aircraft moving at Mach 5 would travel about one mile per second or about 3,600 mph at sea level, far faster than any air-breathing aircraft has ever flown.

Unlike a rocket that carries its own oxygen for combustion, the X-43A's scramjet-short for supersonic-combustion ramjet-scoops air from the atmosphere, making the aircraft lighter, which enables it to carry heavier payloads. The hydrogen-fueled aircraft has a wingspan of approximately five feet, measures 12 feet long and weighs about 2,800 pounds. The first unpiloted X-43A and its Pegasus booster rocket will be air-launched from a B-52 from NASA's Dryden Flight Research Center at Edwards, Calif. The booster will accelerate the X-43A to Mach 7 at approximately 95,000 feet. At booster burnout, the X-43 will separate from the booster and fly under its own power on a pre-programmed flight path. The NASA Hyper-X Program's development and flight testing of the X-43 vehicle is conducted jointly by Dryden and the Langley Research Center, Hampton, Va.

"The Hyper-X Program and the X-43A Flight Project have forged a very fruitful partnership and national asset," said Joel Sitz, Dryden's X-43 project manager. "What the country is witnessing is the re-birth of hypersonics. "After a successful X-43A mission, the 'brain trust' will exist to move forward with future propulsion- research vehicles that will ultimately result in more efficient space access vehicles," Sitz added.

"The Hyper-X program takes what we've been doing for the last 40 years in wind tunnel research to flight. Flight is reality," said Vince Rausch, Hyper-X program manager at Langley. "The program is structured around the scramjet engine and should be a major leap forward in the national capability for access to space. The country is looking for safer, more flexible, less expensive ways to get to space, and that's what the scramjet engine would bring us."

Scramjet technology could also allow more traditional aircraft-like operations of launch vehicles, with horizontal take-off, landing and servicing, which could greatly reduce operational cost and time between flights. Three X-43A flights are planned; the first two will fly at Mach 7 and the third at Mach 10. Valuable performance data will be relayed electronically to Dryden and Langley. Each experimental aircraft will fly once in the Naval Air Warfare Center Weapons Division Sea Range off the southern coast of California and impact into the Pacific Ocean.

Like the comparatively slower ramjet counterpart, the scramjet has a simple mechanical design with no moving parts. However, scramjet combustion occurs at supersonic air speeds in the engine. Rather than using a rotating compressor like a turbojet engine, the forward velocity and vehicle aerodynamic design compress air into the engine. There, fuel, usually hydrogen, is injected and the expanding hot gases from combustion accelerate the exhaust air and create thrust. In the case of X-43, the thrust will propel the vehicle at hypersonic speeds up to Mach 10. The first free-flight test will be approximately three weeks after an upcoming captive-carry flight, where the B-52 flies with the X-43A "stack" to the test range for a series of flight systems tests. Following the first series of X-43A hypersonic flights, the next step is an expanded hypersonics research ground and flight program currently in place as part of the Advanced Space Transportation Program, which is led by the Marshall Space Flight Center in Huntsville, Ala.

6.THE WORKING OF A HYPERPLANE (Seminar Hyperplanes)

B-52 Bomber carrying X-43 Hyperplane for experiments

The aircraft is first propelled by jet engines to the required height. Other method is to take the aircraft to required altitude by another plane. Because neither scramjets nor ramjets can operate efficiently when they are traveling below Mach 2 or 3, a third type of propulsion (perhaps turbojet or rocket) is required for takeoff. So-called rocket-based combined-cycle engines, which could be used in a space vehicle, rely on a rocket that is integrated within the scramjet combustor to provide thrust from takeoff through subsonic, low-supersonic and then ramjet speeds. Ramjet operation is then followed by scramjet propulsion to at least Mach 10 or 12, after which the rocket is utilized again to supplement the scramjet thrust. Above Mach 18, the rocket by itself propels the vehicle into orbit and enables it to maneuver in space. NASA is currently testing several variations of such a system.

Any aircraft faster than the speed of sound creates a shock wave, as air "piles up" in front of the vehicle. Faster the aircraft, more severe the shock wave. Most hypersonic designs intend to confine the most of the high pressure airflow from the shock wave beneath the vehicle, so that it appears to be 'riding' the top of the wave. This results in lower drag to lift ratios than other hypersonic designs. In the process also giving them all a characteristic look.

The landing procedures begin by the switching off of the scramjet engines. Then the horizontal flight is done using normal jet engines and lands like a normal aircraft. Unlike a rocket that carries its own oxygen for combustion, the X-43A's scramjet-short for supersonic-combustion ramjet-scoops air from the atmosphere, making the aircraft lighter, which enables it to carry heavier payloads. The hydrogen-fuelled aircraft has a wingspan of approximately five feet, measures 12 feet long and weighs about 2,800 pounds.

THERMAL PROTECTION SYSTEM FOR HYPERPLANES (Seminar Hyperplanes)

New materials offer good insulation at high temperature, but they often sacrifice themselves in the process. Therefore studies often plan on "active cooling", where coolant circulating throughout the vehicle skin prevents it from disintegrating. Often the coolant is the fuel itself, much in the same way that modern rockets use their own fuel and oxidizer as coolant for their engines. All cooling systems add weight and complexity to a launch system and reduce its efficiency. The increased cooling requirements of scramjet engines result in lower efficiency. Heat resistant materials like insulating tiles and materials made of Titanium and its alloys can be used as passive cooling methods. Active cooling methods (by coolants or fuel itself) can also be employed which is widely used in space crafts.A combination of this two methods can also be tried.The real challenge lies in the development of composite materials which are light weight and also a better thermal insulator.

ADVANTAGES AND DISADVANTAGES OF SCRAMJET ENGINES (Seminar Hyperplanes)

Unlike a rocket that quickly passes mostly vertically through the atmosphere or a turbojet or ramjet that flies at much lower speeds, a hypersonic air breathing vehicle optimally flies a "depressed trajectory", staying within the atmosphere at hypersonic speeds. Because scramjets have only mediocre thrust-to-weight ratios, acceleration would be limited. Therefore time in the atmosphere at hypersonic speed would be considerable, possibly 15-30 minutes. Similar to a re-entering space vehicle, heat insulation would be a formidable task. The time in the atmosphere would be greater than that for a typical space capsule, but less than that of the space shuttle.

New materials offer good insulation at high temperature, but they often sacrifice themselves in the process. Therefore studies often plan on "active cooling", where coolant circulating throughout the vehicle skin prevents it from disintegrating. Often the coolant is the fuel itself, much in the same way that modern rockets use their own fuel and oxidizer as coolant for their engines. All cooling systems add weight and complexity to a launch system and reduce its efficiency. The increased cooling requirements of scramjet engines result in lower efficiency.
The efficiency of a launch vehicle depends greatly on its weight. Calculating the efficiency of an engine system is mathematically complex, and involves trade offs between the efficiency of the engine (takeoff fuel weight) and the complexity of the engine (takeoff dry weight)

Scramjets have few to no moving parts. Most of their body consists of continuous surfaces. With simple fuel pumps, reduced total components, and the re-entry system being the craft itself, scramjet development tends to be more of a materials and modeling problem than anything else.

A scramjet cannot produce efficient thrust unless boosted to high speed, around Mach 5, depending on design, although, as mentioned earlier, it could act as a ramjet at low speeds. A horizontal take-off aircraft would need conventional turbofan or rocket engines to take off, sufficiently large to move a heavy craft. Also needed would be fuel for those engines, plus all engine associated mounting structure and control systems. Turbofan engines are heavy and cannot easily exceed about Mach 2-3, so another propulsion method would be needed to reach scramjet operating speed. That could be ramjets or rockets. Those would also need their own separate fuel supply, structure, and systems. Many proposals instead call for a first stage of droppable solid rocket boosters, which greatly simplifies the design.

Unlike jet or rocket propulsion systems facilities which can be tested on the ground, testing scramjet designs use extremely expensive hypersonic test chambers or expensive launch vehicles, both of which lead to high instrumentation costs. Launched test vehicles very typically end with destruction of the test item and instrumentation.

There is no published way to make a scramjet powered vehicle (or any other hypersonic vehicle) stealthy- since the vehicle would be very hot due to its high speed within the atmosphere it should be easy to detect with infrared sensors. However, any aggressive act against a scramjet vehicle would be difficult because of its high speed.

DIFFERENCE BETWEEN SCRAMJET AND JET ENGINES ( Seminar Hyperplanes)

Difference between scramjet and jet engine.

The main difference is that the scramjet does not contain any moving parts like compressor blades, turbine blades etc. Also in scramjet there is no compression to subsonic velocities.In a jet engine compression and combustion process occurs at subsonic velocities.Thus combustion efficiency will be better in jet engines.In a jet engine a compressor for compression,combustion chambers for compression and turbines to run the compressors.The main difference is that in a scramjet engine all the processes like compression,combustion and exhaust takes place at supersonic velocities.But there are no moving parts in a scramjet engine.A scramjet engine consisted of only a constricted tube.Thus chances for mechanical failures due to moving parts are avoided.The differences are clearly shown in the diagram released by NASA.

WORKING OF A SCRAMJET ENGINE (Seminar Hyperplanes)

Scramjet engine working

Scramjet operation simple diagram

Like a ramjet, a scramjet essentially consists of a constricted tube through which inlet air is compressed by the high speed of the vehicle, a combustion chamber where fuel is combusted, and a nozzle through which the exhaust jet leaves at higher speed than the inlet air. Also like a ramjet, there are few or no moving parts. In particular, there is no high-speed turbine, as in a turbofan or turbojet engine, that is expensive to produce and can be a major point of failure.Also there is no compressor for air compression.Thus it compress air by shock or by the shape of the inlet and fuel is injected and combustion occurs and air is expanded at higher velocities and is exhausted through the nozzle. Inlet, combustion and exit are at supersonic velocities.Thus scramjet is supersonic combustion ramjet engines.

5. BASIC REQUIREMENTS FOR A HYPERPLANE(Seminar Hyperplane)

The hyperplanes have lot of differences in its design and working, therefore some basic requirements have to be met .They are,

JET ENGINES
Jet engines are required if horizontal take off is needed ( take off like other planes). Normal jet engines can be used for this purpose which will power the air craft to the height required for the working of ramjet engines and rocket engines. The main need for this arises since a scramjet engine cannot be started from zero velocity.

BOOSTER ROCKET ENGINE
rocket-based combined-cycle engines, which could be used in a space vehicle, rely on a rocket that is integrated within the scramjet combustor to provide thrust from takeoff through subsonic, low-supersonic and then ramjet speeds. Ramjet operation is then followed by scramjet propulsion to at least Mach 10 or 12, after which the rocket is utilized again to supplement the scramjet thrust. Above Mach 18, the rocket by itself propels the vehicle into orbit and enables it to maneuver in space. NASA is currently testing several variations of such a system. Hyper-X uses only the first stage of Orbital's Pegasus rocket . For a typical space launch, the Pegasus features three stages. The Pegasus stage has some alterations just for X-43 launches, but it is basically the same booster used to deliver small satellite payloads into Earth orbit.

SCRAMJET AIR BREATHING ENGINE
A scramjet (supersonic combustion ramjet) is a variation of a ramjet with the distinction being that some or all of the combustion process takes place supersonically. At higher speeds, it is necessary to combust supersonically to maximize the efficiency of the combustion process. Projections for the top speed of a scramjet engine (without additional oxidiser input) vary between Mach 12 and Mach 24 (orbital velocity). A scramjet is a type of jet engine designed to operate at the high speeds typically associated with rockets. Its main difference from a rocket is that it collects air from the atmosphere to burn its fuel, rather than carrying an oxidizing substance on board. More conventional jets (turbojets, turbofans and ramjets) share this characteristic but are unsuitable for the high speeds at which scramjets can operate.