Vertical and Short Takeoff and Landing Aircraft V/STOL
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USAF / Army
1962 Joint |
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Hiller VZ-1 / HO-1 Pawnee / YHO-1E Flying Platform
In early 1950s, the NACA engineers proposed a concept that placing the rotors on a bottom of the aircraft, a pilot could steer it by shifting his weight, called "Kinesthetic" control. The deLackner Aerocycle was an early, 1950s design that used 15 ft counter-rotating coaxial propellers driven by a 25 HP outboard motor. Later versions used a 40 HP motor when the vehicle proved underpowered in early tests. Kinesthetic control limited top speed to alxmt 20 mph.
In 1953, the Office of Naval Research (ONR) awarded Hiller Helicopter a contract for the development of a VTOL research-flying platform as a tactical reconnaissance and transport aircraft. Hiller used two engines, each driving one of the rotors inside the 5' diameter duct and the aluminum tube platform fixed atop the duct. The 1st prototype was given the Navy designation YHO-1E. After a year of flight tests, the U.S. Army was also interested in its performance, and ordered a modified vehicle for service testing and operational evaluation.
This 2nd prototype was re-designated VZ-1 in 1956 [earlier Army designation: HO-1]. For improvement to produce enough thrust to climb out of ground-effect, it was designed with a larger 8' diameter duct. Hiller's successor was a larger version designed to overcome the design deficiencies of the earlier model. The second platform used a 8 ft diameter ducts with propellers driven by three interconnected engines. The vehicle proved to bt too big, too heavy to control kinesthetically, and had a lower top speed than the VZ-1. The added weight affected the pilot's ability to use kinesthetic control. The unsolved control problems caused it retired in 1959.
Vertol VZ-2
Vertol, Canadair, and Fairchild all built tilt-wing prototypes, the Vertol Model 76 and VZ-2 flying first in 1957 followed by the much larger Hiller X-18 and Fairchild/Vought/Hiller XC-142A in 1959. Canadair built its CL-84 in 1965. All prototypes proved the efficacy of tilt-wings but none were carried into production.
The Vertol Model 76 and its Successor, the VZ-2, were the first Tilt-Wing demonstrators. The small VZ-2 demonstrator of 1957 may be of sufficient size for some personal air vehicles [PAVs]. The program was funded by the Army Transportation Corps and the aircraft was built under the cognizance of the Office of Naval Research. It was a 3,200 pound TOGW aircraft using one Lycoming T53 turboshaft to drive two 3-blade propellers and two tail fans. It was tested at NASA/Langley Research Center in the late '50s with disappointing results. The wing exhibited stall problems at 25° to 30° incidence which were aggravated during partial power descents. It also exhibited poor ground effect interactions at altitudes below 15 feet.
Ryan VZ-3
NASA Ames' experience with V/STOL configurations in the late 1950s came from flying the VZ-3, X-14, and XV-3, along with the VZ-2 and VZ-4, and formed the basis for early attempts to define flying qualities criteria and to gain an understanding of operational techniques for these aircraft.
Turning propeller thrust through large angles proved a tempting idea to achieve VTOL flight, or at least STOL or super-STOL flight. Both Ryan and Fairchild built prototypes. The Ryan VZ-3RY Vertiplane of 1959 was a high wing aircraft using a single T53 turboshaft engine driving two 9 ft diameter propellers in underslung nacelles blowing large-chord flaps to redirect propeller and wing flow vertically. Residual jet thrust provided attitude control. The VZ-3RY used deflected propeller slipstream to augment wing lift, and a form of engine exhaust gas reaction control for low-speed pitch and yaw control. Ames added full-span slats to the wing to increase its lift.
Tests were carried out in the 40- by 80-foot wind tunnel to define its performance, stability and control, and handling characteristics. With any wind, the aircraft could nearly hover out of ground effect, but it was ungainly and difficult to control in the presence of gusts. Howard Turner led the project and Glen Stinnett and Fred Drinkwater did most of the flying. The aircraft was lost when Stinnett ran out of nose-down control at low power and the aircraft pitched inverted and crashed into San Francisco Bay. He was able to eject and survived to continue his career in Ames flight test. During flight tests at NASA/Ames Research Center, the aircraft suffered from a thrust deficiency in ground effect but could hover out of ground effect. The aircraft was subsequently rebuilt to complete the test program.
Doak VZ-4
Tilting engine exhaust flow is one way to achieve vertical flight, as just discussed; another is to tilt the entire engine, or possibly even the entire aircraft or tilt ducted fans, or even jet engines. The Doak VZ-4 of 1958 had a 3,000 # TOGW and used on Lycoming T53 turboshaft engine driving two 4 ft diameter ducted fans which could tilt through 90°. The overall approach proved promising but was very noisy, the ducted fans at full power sounding like sirens.
Fairchild VZ-5
Turning propeller thrust through large angles proved a tempting idea to achieve VTOL flight, or at least STOL or super-STOL flight. Both Ryan and Fairchild built prototypes. The Fairchild VZ-5 was a similar layout except that a single T58 drove four propellers. The wing had 50% chord, full-span articulated flaps turning the flow 60 ° . The remaining 30 ° required for vertical takeoff was provided by rotating the air,:raft to that ground attitude. Both aircraft demonstrated the feasibility' of this approach but it had narrow operating margins which could be made worse by poor piloting technique.
Chrysler VZ-6
The U.S.Army conducted research and development programs in the 1950s and '60s to examine the feasibility of augmenting groundborne jeeps with aerial counterparts. In 1969, Chrysler developed the VZ-6 which used two 8.5 ft diameter ducted fans driven by a single 500 HP reciprocating engine It had a 2300# TOGW with a crew of one and turned over on its first flight. The Army terminated the project because of control problems.
Curtiss-Wright VZ-7 Aerial Jeep
Tilting engine exhaust flow is one way to achieve vertical flight, as just discussed; another is to tilt the entire engine, or possibly even the entire aircraft or tilt ducted fans, or even jet engines. Of particular note was the Curtiss-Wright VZ-7 which was developed in the 1950s as a prototype flying jeep, and entered flight test in 1957. The VZ-7 used four 80 inch diameter propellers driven by a 425 HP Turbomeca Artouste II. During flight test it flew as long as 25 minutes at a time, but top speed was under 50 mph. The program was terminated in 1960.
Piasecki VZ-8 Flying Jeep
In 1958, Frank Piasecki built the VZ-8 for the U.S.Army which was a single place demonstrator. It used two 7.5 ft diameter ducted fans driven by two 180 HP Lycoming reciprocating engines. Fan blades used cyclic control, but the vehicle proved underpowered. It did exhibit excellent operation in ground effect. however, but needed artificial stabilization for flight. The powerplants were later replaced with two 425 HP Turbomeca Artouste turboshafts and performance improved.
Avro VZ-9 Avro Car
Lockheed VZ-10 (XV-4A) Hummingbird
The U.S.Army began funding several theoretically promisinF, V/STOL approaches in 1961. Lockheed won a contract with its Model 330 as the VZ-10, which was redesignated XV-4A in 1962.
Ryan VZ-11 (XV-5A) Vertifan
Hawker Siddeley VZ-12 (XV-6A) Kestrel
Progress in the development of a practical and capable vertical takeoff and landing (VTOL) fighter has been exceedingly slow over the years, largely due to propulsion limitations and related problems. In more general terms, the VTOL is thought of as a conventional type of aircraft with special features added to enable it to rise vertically during takeoff and to land from a vertical descent. The successful and imaginative employment by the military of the first VTOL type, the helicopter, is now part of aviation history. Currently, the military focus of attention is on a new VTOL type, the VTOL tactical fighter aircraft.By the mid-1960s resurgent interest in the VTOL fighter was in evidence. The aircraft industries of some six or more major countries were currently active in the testing, development, or production of VTOL aircraft. In Great Britain, the Hawker Siddeley Company designed, developed, and placed into service the world's first production VTOL strike fighter, the P.1l27 Kestrel. The real breakthrough in jet VTOL operations came, however, with the development of the vectored-thrust turbojet designed specifically for VTOL aircraft installation. The vectored thrust principle was originated by the French designer, Michel Wibault, who conceived the idea of deflecting the thrust from centrifugal compressors, driven by the Bristol Orion engine. This idea was further developed by Dr. Stanley Hooker and resulted in the first vectored-thrust turbofan, the Bristol Siddeley 53 Pegasus 5. This engine is basically a turbojet driving a ducted fan. A part of the relatively cool compressed air of the ducted fan is expelled through the front pair of cascaded nozzles; the rest of the air is passed on to the compressor of the turbine. After combustion the exhaust gases are expelled through the aft pair of nozzles.
The British-built Kestrel was designed with vertical/short takeoff and landing capabilities, making it possible to operate from grass or semi-prepared surfaces offering great operational flexibility. Four adjustable exhaust nozzles beneath the wing roots could be rotated to provide thrust for vertical, backward or hovering flight as well as conventional forward movement.
The first Kestrel began conventional flight trials on March 13, 1961, in Britain. In 1962 the governments of the United States, Britain and the Federal Republic of Germany ordered nine aircraft for combined testing by those countries' representatives. They formed an evaluation squadron that conducted Kestrel trials between April and September 1965. Six of these trial aircraft were later delivered to the United States where, as XV-6As, they underwent additional testing of V/STOL fighter techniques.
The Hawker-Siddeley Kestrel (XV-6A) is a single-place, prototype, vectored-thrust, V/STOL strikereconnaissance aircraft. A single Rolls Royce Pegasus Mark 5 engine powers the Kestrel. The Pegasus is an axial-flow vectored-thrust turbofan engine with an uninstalled sea-level static thrust rating of 69 000 newtons (15 500 Ib). Thrust is vectored through two pairs of controllable engine exhaust nozzles and is equally distributed between the forward nozzles which exhaust cool air from the fan and the aft nozzles which exhaust turbine air. The nozzles are mechanically interconnected and can be rotated, at rates up to 90°/sec, to any position from fully aft (O: = 0°) to 5° forward of vertically downward (9* = 95° Y Nozzle angle is controlled by a single lever located inboard on the throttle quadrant which is the only additional control required for thrust vectoring in the Kestrel.
Control moments during nonvectored flight are provided by conventional aerodynamic surfaces. The ailerons and tail plane are powered by tandem hydraulic systems; the rudder is unpowered. Lateral control forces are provided by a nonlinear spring unit and longitudinal forces by a q-feel unit supplemented with a feel spring. A bobweight in the control run increases longitudinal maneuvering forces by 8.9 N/g (2 Ib/g), and 4.9 N/rad/sec2 (1.1 Ib/rad/sec2) for pitch acceleration.
During vectored flight, reaction control moments are added to those produced by the normal aerodynamic surfaces. Reaction control shutter valves, located at the nose, tail, and wing tips, are mechanically connected to their corresponding aerodynamic control surface and receive high-pressure engine bleed air as a function of engine nozzle angle. Full reaction control is provided at engine nozzle angles greater than 300. No stability augmentation system (SAS) is provided. However, during flight at low dynamic pressures where the pilot does not get feedback to the control stick from forces on the control surfaces, an artificial-feel system is provided. Lateral feel is provided by a nonlinear spring unit and longitudinal forces are provided by a g-feel unit supplemented with a feel spring.
Analytical and simulator studies of the flight and handling qualities of aircraft require that accurate estimates of the aerodynamic parameters be used if the results are to be valid. One of the more accurate methods of obtaining aerodynamic parameters is from data obtained during flight tests. To provide aerodynamics for analytical and simulator studies, and also to provide numerical values for comparison with wind-tunnel data and theoretical estimates, parameters have been extracted from flight data for many years. Flight-test data were used to extract the longitudinal aerodynamic parameters of the Kestrel aircraft. The aircraft configurations included thrust-jet angles of 0°, 15°, and 30°, and Mach numbers of 0.43, 0.62, and 0.82. The results show that deflecting the thrust past 15° has an effect on the pitching-moment derivatives. Deflecting the thrust downward decreases the longitudinal static stability parameter -Cm and generally decreases the damping-in-pitch parameter -(Cm + Cm .\ for trim normal-force coefficient -Cz 0 values greater than 0.2. The trend toward reduction in the longitudinal stability parameter also had been noted by the pilots during flights of the Kestrel.
An improved version, known as the Harrier, became the world's first operational V/STOL fighter when it entered Royal Air Force service in 1969. However clean the Harrier's lines may be, the tracing of its lineage is a remarkably complex business. During its life span, the Harrier's parent company has changed names from Hawker to Hawker-Siddeley to British Aerospace, with McDonnell Douglas recently acquiring stepparent status for the coproduced American AV-8B derivative. The Harrier and its immediate predecessors, the P-1127 and Kestrel, have been known by no less than six names: The concept that led to the Harrier was initially assigned the Hawker project designation P- 1127, under which it flew as a prototype and concept demonstration vehicle. The Kestrel, the ensuing service test version, was named for a species of small European falcon noted for its habit of turning into the wind and hovering over a fixed spot while looking for its prey. The Kestrel also received the United States military designation XV-6A. The definitive Royal Air Force production derivative was named Harrier after a genus of highly maneuverable, low-flying hawks that build their nests on the ground. Sea Harrier was subsequently-and logically-applied to the navalized version. The initial Marine Corps variant was assigned the colorless AV-8A designation.
Shortly after the airplane was invented, its disadvantage of requirement of a significant runway for takeoff and landing was quickly noticed, which significantly limit the airplane's utility. The operational benefits of an ability to takeoff and land vertically are self evident. Conventional aircraft must operate from a relatively small number of airports or airbases with long paved runways. For commercial transportation, the airport is rarely where you actually wish to go, and is usually crowded causing delays in the air and on the ground. For military aircraft the airbase is vulnerable to attack, and the time expended crusing to and from the in-the-rear airbase increases the necessary range of the aircraft increases the response time.
Like most technical subjects, the area of vertical flight has spawned its own arcane terminology. VTOL refers to a capability for Vertical TakeOff and Landing, as opposed to Conventional TakeOff and Landing (CTOL). VTOL is the broadest terminology and can be applied equally well to a helicopter or an Apollo space capableaircraft which has the flexibility to perform either vertical or short takeoffs and landings is said to have VSTOL capability (Vertical or Short TakeOff and Landing). An aircraft which has insufficient lift for vertical flight at takeoff weight but which can land vertically at a reduced weight is called a STOVL (Short TakeOff and Vertical Land).
The helicopter was introduced in order to overcome the limitation of the airplane. However, the helicopter has not received wide spread use but only in special roles that strictly require VTOL capability, and the helicopter numbers is but {fraction (1/10)} that of the airplane. The helicopter flies too slowly and too inefficiently, with speed and range 1/2 to 1/3 that of the airplane, with 2 to 3 times the fuel consumption and cost of operation per passenger-mile.
The helicopter is less safe per passenger-mile basis. According to NTSB statistics, the fatality rates for piston helicopters is 3-4/100,000 hrs and for light turbine helicopters 2-3/100,000 hrs where as the rates for a typical high wing airplane such Cessna 172 is 0.5 and Cessna 182 is 0.7/100,000 hrs. Light turbine helicopters have purchasing cost 2-4 times that of comparable piston airplane, but recently, the Robinson piston helicopters with their simplified rotor head design has brought down their purchasing cost to a level comparable with piston airplane.
In order to maintain the VTOL advantage of the helicopter while overcoming the helicopter's inefficiency and slow speed, there have been at least 50 different projects experimenting with high-speed VTOL aircraft by a large numbers of well known aerospace companies, proposing at least 12 different configurations in the last five decades. Today, there are only two VTOL transport airplanes that have sufficient merits to achieve production status, the military tilt-rotor Bell-Boeing V-22, and the civilian tilt-rotor Bell-Agusta BA-609. Rotary wing aircraft, such as helicopters, have had more commercial success than the military designs, but still rely predominately on turbojet engines to provide the power for vertical lift. Their advantage in vertical lift capability is offset by their poor flight stability characteristics, and very high initial and maintenance costs.
Helicopter designs fall into two broad categories; a single lift rotor with a tail rotor to control yaw, and two lift rotors rotating in opposite directions to control yaw. The single lift rotor is much more popular since it is simpler, but it yields roughly 30% less direct vertical lift for a given horsepower than the dual rotor system. Typically, helicopter rotor systems provide a lifting capability of 10-15 pounds per horsepower, with top speeds in horizontal flight of less than 200 miles per hour. The flight and maintenance problems associated with helicopters are well known and bear no repeating.
The history of non-rotary wing V/STOL (vertical/short takeoff and landing) aircraft development has generally proceeded along two separate paths. STOL (short takeoff and landing) aircraft development has centered on conventional aircraft operation, using enhanced lifting devices to shorten takeoff and landing runs. VTOL aircraft development has centered on the use of powerful jet engines to provide the required vertical thrust, and as such has focused on military applications. Latest developments, such as the Osprey aircraft being procured by the US Marines, use two widely spaced proprotors, similar to large propellers, but without shrouds or ducts. These proprotors rotate during flight approximately 90 degrees, from a horizontal to a vertical position to transition from vertical lift to horizontal thrust. The prop-rotors are too large in diameter for the plane of the rotors to be rotated to a vertical position when sitting on the ground.
STOL designs reduce the takeoff and landing runs for aircraft by primarily reducing the stall speed of the aircraft. This is accomplished by increasing either the available wing lifting area or increasing the lift coefficient the wing is capable of producing, by means well known to practitioners of the art. Regardless of the design. STOL aircraft must provide forward movement of the aircraft in order to produce lift, with the notable exception of the Custer channelwing aircraft, which could lift vertically while tethered. STOL aircraft have the potential to be particularly safe aircraft, since there is a direct relationship between the severity of injuries sustained in crashes and the speed at impact. With a lower potential impact speed due to lower stall speeds, STOL aircraft can be designed to provide complete protection from injury in most crash landing situations.
Autogyros provide for lift using an unpowered overhead rotor system similar to the helicopter, with auxiliary wings to provide supplemental lift. Gyrocopters do not have auxiliary wings. Most designs provide pusher propellers as the primary means of propulsion. The Cartercopter is a recent example.
Current gyrocopters provide prerotors to spin up the main rotor system to high speed, and then use a "jump" takeoff to lift almost vertically. The gyroscopic inertia of the main rotor is used to lift the aircraft into the air, where it then accelerates forward using the pusher propeller. Once moving forward, the rotor speed is maintained by contact with the moving air. Gyrocopters with prerotors do not have hovering capability in a loitering mode.
Tilt Rotor (Prop-rotor) aircraft provide two or more very large propellers mounted on wingtips or wing pylons. The propellers rotate through over 90 degrees of angle, from a horizontal axis for forward flight, through to a vertical axis for vertical lift thrust. Due to the need for redundancy in case of a single engine failure, complex crossover shafting is required. Current aircraft of this type are military, with smaller civilian versions in the planning stages. These aircraft have lower thrust output for a given horsepower than helicopters, but have the capability to exceed 300 miles per hours in horizontal flight.
Ducted rotors, also known as ducted fans, are more efficient and quieter than exposed propellers of the same diameters. They are also safer than exposed propellers on the ground. VTOL aircraft using ducted fans have been the most commonly developed prototype, but with little success. While the ducted fan provides greater lift than a simple unducted propeller, the drag produced by the duct shroud in forward flight at speeds over 150 mph has greatly limited the success of this type of VTOL aircraft.
There are numerous fan-in-wing configurations, which have been patented, but none has proved to be successful. The primary problem has been the high required disc loading causing high exhaust velocities. A good example is where fans are located in each wing, with the wings having a retracting feature to cover the fans in forward flight.
The greatest military success in VTOL aircraft has come with the alternate, in the form of the Marine Corps Harrier. Other aircraft, including the Moller SkyCar and Soltrek XFV, are in flight testing. The Skycar uses eight separate engines in four deflected thrust lift pods to provide both vertical and horizontal thrust. Many of the VTOL designs have the capability of STOL operation. In particular, the Harrier is used by the British with a jump takeoff ramp on aircraft carriers to enhance range and payload.
In the field of vertical and short take-off and landing aircraft gas turbines are often adapted to provide thrust for both normal wing-borne flight and for lift. This is achieved using vectorable nozzles for changing the direction of the engine thrust. For stability and ease of aircraft control an existing engine of this type employs an arrangement which uses four side mounted nozzles which can be rotated on simple bearings through an angle of over ninety degrees. Two of the nozzles are located forward of the aircraft centre of gravity on port and starboard sides and receive air from the engine compressor. The other two nozzles are located rearward of the centre of gravity on port and starboard sides and receive exhaust gas from the turbine section.
The absence of a conventional axial jet pipe in the basic arrangement enables the rear structure of the engine to incorporate a permanent transverse portion which acts as a gas deflector and strengthens the structure with respect to torsional loads. The rearward pair of nozzles can then be carried by the engine casing which greatly eases problems of sealing the nozzles against hot gas leakage. In a development of this type of arrangement which incorporates an axial jet pipe the transverse portion of the rear structure no longer exists and the torsional loading of the rear nozzles can no longer be tolerated. The nozzles can be carried by the airframe in which case a solution must be found to the difficulty of controlling hot gas leakage from means connecting the engine to the nozzles.
Typical VSTOL aircraft, particularly those capable of attaining high speeds, use a combustion engine which acts as a pressurized gas generator which generates pressurized gas for propelling the aircraft. A problem faced by VSTOL aircraft is that the temperature of the pressurized gas is quite high, typically in the range of 1,000.degree. F. and higher, and the pressure is also considerable. When the pressurized gas is directed downwardly, the high temperature and pressure tends to melt tarmac, erode concrete and even heat metal plates below the aircraft to unacceptably high temperatures. The result is that operation of VSTOL aircraft is restricted, and take-off or landing must often be performed with some forward movement to reduce the damage.
In the area of propeller-powered aircraft, the tilt-rotor concept, as tested in the Bell XV-15, seems to offer the best compromise between helicopter-like vertical flight and efficient wing-borne cruise. The tilt-rotor concept is the basis of the V-22 Osprey which is currently under development.
To date, there have only been a few operational jet VTOL designs, the British Harrier and the Russian YAK-36, both of which are subsonic aircraft. While at least one supersonic VTOL design has flown, the Mach 2 Mirage III-V back in 1966, there has yet to be an operational supersonic VTOL aircraft.
This is largely due to the need for increased internal volume for the vertical lift apparatus and fuel capacity. Also, most concepts for vertical lift tend to increase the aircraft's cross-sectional area near the aircraft's center of gravity, increasing the supersonic wave drag. Finally, the state of the art in engine thrust-to-weight ratio has imposed an excessive weight penalty on VTOL designs. It has simply been impossible, up to now, to provide an operational aircraft having both vertical and supersonic forward flight with any practical range.
Modern supersonic jet fighters have a thrust-to-weight ratio exceeding one, so it would seem fairly easy to point the jet exhaust downward and, therefore, attain vertical flight at "no cost". Unfortunately, this is complicated by the balance problem. Many subsonic jets and virtually all supersonic jets are designed with the engine at the rear, the cockpit and avionics at the nose and the payload and fuel near the center of the aircraft. This traditional layout places the expendables at the center of gravity, co-locates the parts of the aircraft requiring cooling (crew and avionics), and keeps the avionics away from the hot and vibrating engine.
If the thrust exceeds the weight, vertical flight could be obtained simply by deflecting the thrust downwards. However, some vertical upward force is required forward of the aircraft's center of gravity. In order to balance the vertical thrust force at the tail. This balance problem is possibly the single most important problem encountered in the design of a VTOL jet fighter.
There are two conceptual approaches to solving the balance problem. Either the thrust location must be moved to the center of gravity, or an additional thrust force has to be applied near the nose. Both of these approaches will tend to move the design of the aircraft away from the optimal layout. Generally, jet VTOL concepts can be divided into those which utilize fairly conventional engines and those which use modified engines so that the fan and core air are split, with the fan air ducted and exhausted from some location separate from the core air.
The conventional engine VTOL concepts which do not use additional lift engines for vertical flight must have a net takeoff thrust-to-weight ratio in excess of one. If the jet exhaust is not diverted to some other location for vertical flight, the aircraft must either be a tail sitter (VATOL), or it must have the engine exhaust located at the aircraft center of gravity and capable of vectoring downward for vertical flight. This can be accomplished by using a vectoring nozzle or nacelles which tilt.
The X-14 research aircraft had vectoring nozzles at the center of gravity, with the engines out in front. This is probably not a good arrangement for most applications because the cockpit winds up in the rear for balance, which does not provide acceptable visibility for the pilot. Also, in forward flight, the jet exhaust scrubs alongside the fuselage which causes thermal and acoustic problems. Tilt nacelles are heavy, but may be the best compromise for some applications. Grumman Aircraft Corporation has been pursuing a tilt-nacelle concept for Naval applications for a number of years.
Some VTOL concepts provide a means of diverting the exhaust flow to provide vertical lift. This is generally done by a retracting blocker device in the engine which shuts off the flow through the rearward-facing nozzle. The flow is then diverted forward through internal ducting. All of these VSTOL approaches, however, exact significant penalties in weight, cost, and completely when compared to a conventional jet aircraft design.
XV-11A Marvel
The Mississippi State University Parsons XV-11A Marvel was a boundary layer control research aircraft designed for the US Army. Operations of single engine, boundary layer control, STOL aircraft since 1958 included the high lift super cub L-21, the modified Cessna L-19 the XAZ-1, and the XV-11A, with wing loadings ranging from 13 lb/sq h to 28 lb/sq ft. All of these aircraft had a distributed suction boundary layer control system for lift augmentation. The XAZ-1 and the XV-11A also had shrouded propellers for static thrust augmentation. The performance stability and control and handling qualities of these aircraft were evaluated and considerable experience gained in the operational aspects of such STOL aircraft with regard fo the handling qualities required for safe operation in the STOL mode.
The boundary layer is a thin film that forms on the surface of a solid body moving through a viscous fluid, like the wing of an airplane moving through the air. Within the film, velocity increases parabolic ally, from zero at the solid surface up to the free-stream velocity at the outer edge of the boundary layer. The depth of the layer varies with the smoothness of the surface, the viscosity of the fluid, and the speed of the flow, but it is never very large. The boundary layer was first identified and labeled by Ludwig Prandtl in 1904 in a classic paper that revolutionized this branch of fluid mechanics.
The flying qualities of wings can be enhanced in two ways, and boundary-layer control can help in both. The first is to decrease drag; the second is to increase lift. The most desirable way to decrease drag is to maintain laminar flow within the boundary layer and prevent a transition to turbulent flow. Laminar flow occurs when successive layers of air within the boundary layer slide smoothly over one another, from the stationary film at the surface up to the free-stream velocity of the outside air. Turbulent flow within the boundary layer occurs when these "streamlines break up and a fluid element moves in a random, irregular, and tortuous fashion," as when the smoke rising from a cigarette in a still room ceases to travel smoothly up but tumbles instead in eddies and curls. Over a normal wing, the boundary layer remains laminar over only a small portion of the wing chord before breaking up into turbulent flow. The area of turbulent flow experiences significantly greater skin-friction drag than the laminar flow.
The second way to improve the flying qualities of a wing through boundary-layer control is to increase the lift, especially the maximum lift, of the wing. Maximum lift can be increased by delaying the onset of separation of the boundary layer. As a wing's angle of incidence increases-as its leading edge is tipped up above the plane of flow of the free-stream air-its lift also increases, up to a point. Finally, however, the boundary layer on the upper surface breaks free of the wing altogether, reducing lift drastically. This is known as stalling. If the boundary layer can be kept from separating, the maximum lift of the aircraft can be increased, an important consideration in increasing takeoff-weight capacity and reducing landing speed.
The XV-11A the Mississippi Aerophysics Research Vehicle Extended Latitude (MARVEL) was a single-engined pusher monoplane fitted with a boundary layer control system. Parts were constructed by the Parsons Corp. The aircraft carried s/n 65-13070 and the first flight took place on December 1, 1965. It carried out its initial program of research on behalf of the US Army in the late 1960s. On completion of the flight program in April 1967, comprising 35 hours over 49 separate flights. Although the aircraft is still in flying condition, failing interest in STOL aircraft of this type by the Department of Defense has curtailed research activities. The aircraft was put in storage to be revived in 1981 with civil registration N2768Q. It was rebuilt in the 1980s as a proof-of-concept for a utility aircraft.
Historic Aviation Volume XII http://www.angelfire.com/ks2/janowski/other_aircraft/AG14/Marvelette.html Anderson Greenwood AG-14 and the MARVEL program by Paul R. Matt Bell, having considerable experience in rotary-wing and tilt-rotor aircraft, was selected in 1973 as a prime contractor for a research program to prove the operational practicality of the tilt-rotor concept. The program was launched by the US Army's Air Mobility Research and Development Laboratory and NASA. Drawing on their experience with the Bell Model 200, the Model 301 was developed. In May 1973, the U.S. Army and NASA requested an MDS designation for the forthcoming Bell Model 301 tilt-rotor demonstrator aircraft. On 30 May 1973, the designation XV-14 was allocated. However, on 7 August 1973, a change of this designation was requested to avoid confusion with the Bell X-14B VTOL aircraft. The V-13 designation was not used for superstitious reasons.
http://www.aiaa.org/tc/vstol/VSTOL.html">V/STOL: The First Half-Century http://www.aiaa.org/tc/vstol/unbuilt/index.htm">Unbuilt V/STOL Concepts http://www.aiaa.org/tc/vstol/unbuilt/bell_tlt/index2.html">V/STOL Aircraft | Bell Tiltrotor "http://www.amazon.com/13-Story-Worlds-Popular-Superstition/dp/1568583060/ref=sr_1_1?s=books&ie=UTF8&qid=1279665238&sr=1-1">13: The Story of the World's Most Popular Superstition by Nathaniel Lachenmeyer (Hardcover - Oct 5, 2004) "http://books.google.com/books?id=C6c1A1ifF3IC">Friday the 13th: a novel By Thomas William Lawson http://www.fantastic-plastic.com/1980s_concept_air.htm US Army XV-8A Flexible Wing Aerial Utility Vehicle (FLEEP)
The XV-8A aircraft (designated FLEEP) resulted from Ryan Aeronautical Company design studies of the application of the Rogallo flexible-wing concept to a manned aircraft. This aircraft is an improved version of the origional Ryan flexible-wing manned test vehicle. The aircraft was designed as a single-place, lightweight utility vehicle, capableof carrying a 1000-pound payload and having short-field take-off and landing characteristics.
The US Army Precision Drop Glider was designed and constructed by the Ryan Aeronautical Co. This cargo delivery system was designed for a payload of 300 pounds which is contained in a rectangular box attached to the bottom of the wing control platform. Four riser straps are attached to the sides of the control platform and the suspension lines from the wing are attached to the risers.
The wing had 6-inch-diameter inflated-tube leading edges and keel, which are 22 feet long_ and a cloth lifting surface. Air for inflating the leading edges and keel is supplied by a high-pressure storage bottle in the rear of the keel. Directional control is achieved by pulling on the suspension line on either wing tip and is actuated by a motor in the control platform. The control system was designed for steering by radio command from a ground or air controller, or by an automatic homing system that seeks a radio beacon located on the ground in the target drop area.
The wing is folded in a compact package similar to a parachute pack and was located in the control platform before deployment. The cargo box and packaged wing are discharged from an aircraft3 and wing deployment is initiated by a static line. Deployment loads are attenuated by use of an initial parachutelike phase. After the tubes have been inflated the reefing lines are cut, and the wing completes deployment and then makes a transition from vertical flight to gliding flight.
This program was successful in demonstrating the feasibility of aerial delivery of cargo by means of a deployable parawing. It was anticipated that development of this use for a parawing would continue and additional controls can be included to provide flare capability for reduction of landing speeds.
The paraglider, or "Rogallo Wing", invented by Francis M. Rogallo in the late 1940s, used flexible fabric airfoils arranged in a V-shape. Flexible wings are wings made of very loose or slack cloth whose configuration in flight is maintained by the combination of the aerodynamic forces and the reactions from the load suspension system. Such wings can be completely flexible_ or they may be stiffened in several ways to meet the requirements of particular applications. The flexible wing could be guided more precisely than a parachute. The flexible wings of most immediate interest were those with no structural stiffening because they have weight, volume, packing, and deployment characteristics potentially as good as those of conventional parachutes, but provide a stable and controllable glide with performance adequate for aerial delivery of cargo and personnel.
After the usual dreaming about flexible wings since childhood, in 1945 at the close of World War II Francis M. Rogallo decided to undertake a serious study of the subject. It was decided to undertake it at hom% jointly with Mrs. Rogallo and later including other members of the family and friends. U.S. Patent No. 2,546,078 filed in November 1948 and issued in March 1951 to Gertrude and Francis Rogallo is entitled "Flexible Kite" even though it proposes applicability of the concept to all heavier than air flying machines. This private endeavor covered the 13 years from 1945 until late in 1958, when America's entry into the exploration of space brought about government consideration of this and other unconventional ideas.
Early flight tests at the Langley Research Center on inflated-tube configurations indicated a possible design approach for the recovery of spacecraft and for aerial delivery of cargo. The need for research information on conical parawings for support of the Gemini parawing and the Army cargo-drop glider prompted extensive wind-tunnel research on inflated-tubetype of wing configurations (see refs. 19, 28, and 24). Other work on wings having small leading edges and a rigid frame led to the construction of flight vehicles such as the Paraglider Research Vehicle and the Ryan Flex-wing.
In the early 1960s the Rogallo wing seemed an excellent means of returning a spacecraft to Earth. The delta wing design was patented by NACA Langley engineer Francis M. Rogallo. In May 1961, Robert R. Gilruth, director NASA's Space Task Group, requested studies of an inflatable Rogallo-type Parawing for spacecraft. Several companies responded; North American Aviation produced the most acceptable concept and development was contracted to that company. In November 1961 NASA Headquarters launched a paraglider development program, with Langely doing wind-tunnel studies and the NASA Flight Research Center supporting the North American test program.
The North American concept was a capsule type vehicle with a stowed parawing that could be deployed and controlled from within for a landing more like an airplane instead of a splash down in the ocean as was the practice in the Mercury and later the Gemini and Apollo programs. The logistics became enormous and the price exorbitant, besides which, NASA pilots and engineers felt some baseline experience like building a vehicle and flying a Parawing should be accomplished first.
The wing was attached to steel tubing to create a flying machine. It ended up looking like an oversized tricycle with a mast. The pilot sat strapped in the seat without any kind of cockpit enclosure. He could fly higher or lower by tilting the wing from side to side with a control stick. This craft, called the Parasev, was one of NASA's first research airplanes. NASA registered the Paresev, the first NASA research airplane to be constructed totally in-house, with the Federal Aviation Administration on February 12, 1962.
Flight testing of the Paresev (Paraglider Rescue Vehicle) started immediately, and proved the wing to be too flexible with it flapping and bulging in alarming ways. The poor membrane design led to trailing edge flutter, with longitudinal and lateral stick forces being severe. A number of different rigging modifications to improve the flying characteristics were tried, but very few were successful and none were predictable. Everything seemed to affect stick forces in the worst way.
The Paresev completed nearly 350 flights during a research program from 1962 until 1964. Pilots flying the Paresev included NASA pilots Milton Thompson, Bruce Peterson, and Neil Armstrong from Dryden, Robert Champine from Langley, and astronaut Gus Grissom, plus North American test pilot E.P. Hetzel. Engineers tested the Rogallo wing for several years in NASA's wind tunnels at Langley Research Center. They decided to stick with the original parachute plan instead of using the paraglider. But, that wasn't the end of the Rogallo wing.
The Paresev was legally transferred to the National Air and Space Museum of the Smithsonian Institute, Washington, DC. Despite its looks, the Paresev was a useful research aircraft that helped develop a new way to fly.
Today, the Rogallo wing is used by the recreational sporting goods industry. Hang gliders soaring from a hillside or cliff are the commercial adaptation of Francis Rogallo's invention to help the space program land its vehicles. It's come a long way. Hang gliders are now used for fun and exploration. Although the Rogallo wing was never used on a spacecraft, it revolutionized the sport of hang gliding, and a different but related kind of wing was tested on the X-38 technology demonstrator. Rogallo first thought of using the flexible wing for recreation. He only presented it to the space industry after deciding that there was nowhere to sell his idea for public use.
The U.S. Army Flexible Wing Aerial Utility Aircraft was designed to carry out the functions of a light utility aircraft. The vehicle is essentially a self-propelled flying cargo platform supported from a Rogallo type flexible wing. A pilot's seat and the necessary flight controls are provided at the forward end of the plat-form. An engine, pusher propeller, and a V-tail are mounted at the rear of the platform. Provision is made for manually folding the wingand tail surfaces.
The basic body structure was in the form of a flat deck. A raised platform at the forward end supports the pilot's seat, nose wheel, control mechanism, instrument panel, and nose fairing. Fittings on the pilot's seat back and at the sides of the platform attach the wing supportstruts. Other fittings at the aft end of the platform provide attachment for the engine mount truss and tail surfaces. The useable cargo area, 64 inches wide and 80 inches long, is fitted with twelve standard flush-type cargo tie-down rings. Because of the open-deck design, long slender cargo items may extend both forward and aft of the normal cargo area. Riveted aluminum alloy sheet and extruded sections are utilized in fabricating the platform structure. Jacking pads are provided on the lower surface of the platform atthe main landing gear and at the forward end of the cargo area. The forward end of the pilot's cockpit is a removable fiberglas fairing. Thefairing support framework also supports the instrument panel and the transparent plastic windshield. The pilot's seat, an integral part of the vehicle structure, is equipped with a standard seat belt and shoulder harness. Space has been provided to accommodate a back-pack typeparachute.
The landing gear is of the tricycle type. The nose andmain tires and wheels are the same size and type to minimize spare part requirements. The main landing gear tread is 9.0 feet, and the wheel-base is 10.63 feet. Large, low-pressure type III tires aid operation from soft ground or rough fields. Landing loads at the main wheels are absorbed by cantilever Fiberglas springs extending from both sides of the platform structure. Heat treated steel axles which mount the aluminum alloy wheels are bolted and clamped to the outboard ends of the springs. Single disc type hydraulic brakes incorporated in the main wheels are hydraulically actuated by a master cylinder in the pilot's cockpit. Pressurized hydraulic fluid is supplied to the brakes through flexible hoses encasedin wire braid. An oleo strut type shock absorber is incorporated in the nose landing gear. The nose landing gear assembly attaches to the forward end of the sheet metal platform by a tubular tripod type structure. The nose wheel which can be steered through an angle of 25 degrees either side of center by operating foot pedals in the pilot'scockpit produces a turning radius of 27.83 feet. The foot pedals are connected to arms extending from the sides of the shock absorber pistontube by a simple cable and pulley system. The nose wheel is aligned ina fore and aft position in flight by a centering cam.
The wing is composed of throe main structural members: a rigid center keel,and rigid right and left leading edges. The two leading edges join the keel atthe apex and form a near-triangular wing planform. The keel runs longitudinally aft from the apex along the center line of the wing. The flexible membrane, made of Dacron with a polyester coating, is continuously attached to the leading edges and keel. The leading edges have a 50-degree sweep angle. The totalwing area in flat planform is 450 square feet.
The wing is of the foldable flexible type made up of a rigid keel, two rigid leading edges, a rigid spreader bar, flexible membrane, fittings, and attaching hardware. The forward ends of the leading edges attach to the forward end of the keel to form an apex which sweepsback at a 50 degree angle. The spreader bar which attaches to the keel at about midway, supports the leading edges to produce the proper sweepangle, and transmits the leading edge lift loads to the keel. The wing keel is a tapered sheet aluminum alloy boxtype structure. A fitting at its forward end supports the leading edge members. The keel attaches to the spreader bar by a hinge fitting at thekeel 46 percent station. Fittings are provided forward and aft of the mainhinge to attach the pitch trim control cables. The leading edges are hollow aluminum alloy spars which have a symmetrical streamlined cross section, and taper from a maximum cross section near the spreader bar attachment toward both ends. An aluminum alloy channel at the maximum cross section serves as a shear web. The attachment at the spreader bar is a swivel fitting with one axis lying along a chord-line and the other axis forward of and parallel to the leading edge. The attachment at the keel is aspherical rod end type fitting. Since the spar is free to align itself to the load, and the wing membrane is attached along the trailing edge, membrane tension is always applied to the plane of maximum spar stiffness. The aft 13-1/2 percent of the leading edge is hinged to permit a 5 degree motion in a chordwise direction to provide additional lateral control. The hinge mechanism incorporates linkage to multiply the mechanical advantage of the actuating cable used to control the position of thehinged leading edge portion in flight.
The wing membrane fabric is square weave Dacron cloth coated on both sides with olive drab polyester resin. The coated material is flexible and extremely weather resistant. Total weight of the coated fabric is 8 ounces per square yard. The coated fabric has a tensile strength of not less than 200 pounds per inch in the warp direction, and not less than 120 pounds per inch in the fill direction. The membrane is attached along the keel and leading edges with machine screws. Metal reinforcing strips are bonded into the reinforced, bonded,and sewn edges of the membrane. To prevent trailing edge flutter, the aft edge of the membrane is scalloped, and thin wooden battens (3 perlobe) are retained in pockets sewn in the trailing edge membrane. A reinforcing cable, the length of which is adjustable on the ground for rolltrim, is sewn into a hem along the aft edge of the membrane.
The propulsion system consisted of a six cylinder, aircraft reciprocating engine equipped with a fixed-pitch propeller employed as a pusher, and an exhaust-driven ejector cooling system. A steel tube truss supported the engine near the aft end of the platform structure. Four flexible rubber mounts are used to attach the engine tothe truss. The propeller thrust line is inclined 3 degrees up at the rear with respect to the platform surface. The exhaust driven ejector cooling system is self-regulating, and requires no action on the part of the pilot. Sheet aluminum baffles direct the cooling air through cooling fins on the engine cylinders and heads.
The performance capabilities of the airplane were all within predicted values. The cruise capability was such that a 100-mile mission can be flown at maximum gross weight. Take-off and landing performance proved the STOL capability of the airplane. At maximum gross weight, the take-off distance over a 50-foot obstacle is 1,000 feet. Landing distance to clear a 50-foot obstacle is 400 feet. During the course of the test program, the airplane proved to be a reliable and easy aircraft to maintain and service. Some test operations were conducted from unprepared desert surfaces, establishing the capability for operation from areas other than regular airfields. The operational and flying techniques are basically similar to those of lightweight conventional aircraft. The two-control system lends itself to simplicity and provides adequate control power to permit a fixed wing incidence trim setting for the entire flight including take-off, climb, cruise, descent, and landing.
The handling characteristics of the aircraft were good. Control harmony between the longitudinal and lateral control systems was excellent, enabling the aircraft to be flown with one hand. Stability in all cases was positive with only light forces required. The flight characteristics of this airplane were similar in most respects to those found in a conventional airplane with a comparable light wing loading
The aircraft was safe and pleasant to fly for an Army pilot of average skill. Data available indicated that, with improvements, the concept can be developed into a flying truck with reduced experience and skill requirements for tho operator. Helicopter and light plane experience aids intransition to this aircraft, although such experience was by no means necessary. The aircraft is capable of rough field operation with certain advantagesover fixed-wing aircraft or helicopters.
Safe landing characteristics with engine power at idle were demonstrated. The system was highly sensitive to turbulence and rough air which is uncomfortable, but is self-damping to a high degree. The wing appeared to lose lift in some conditions of turbulence, causing some degradation of climb and descent performance. Crosswind operation investigations were continuously conducted. The results suggested that limitations will eventually be established that were quite compatible with light aircraft of about the same weight.
The idea of a primitive, low-cost, low-maintenance, limited-performance but useful acrial device was clearly demonstrated. For example, only one operation out of 47 was delayed due to aircraft maintenance. This program did not represent an operational evaluation environment; however, the low maintenance and support required was very unusual for an experimental aircraft. The aircraft met or exceeded all predicted performance goals and demonstrated its ability to haul bulky cargo shapes and a useful load almost equal to its empty weight. The ability of the aircraft to operate as a light STOL utility vehicle with a 100-mile range was established.
Dimensions. The principal dimensions of the vehicle are: Length26 feet Wing Span (spread)33.4 feet Width (wing folded)10 feet Height (wing at zero incidence)14. 5 feet Wing Area (flat plan form)450 square feet Wing Sweep (leading edge)50 degrees Wing Keel Length26. 0 feet Length of Platform (cargo area) 80 inches Width of Platform64 inchesWheel Base10. 6 feet Wheel Tread9 feet Propeller Diameter7 feet Weights. The principal weights of the vehicle are: Weight Empty 1,115 pounds Engine Oil15 pounds Fuel150 pounds Pilot170 pounds Flying Weight Without Cargo1,450 pounds Cargo Payload 850 pounds Design Gross Weight 2,300 pounds
Convair Model 48 "Charger"
The first flying prototype COIN (for Counter INsurgency), the Convair Model 48 "Charger," was designed according to a Marine Corps specific operating requirement (SOR) that specified a take-off and landing distance of 500 feet over a 50-foot obstacle and included a requirement for "single-engine survivability." Designed for reconnaissance, close support and paratroop ferrying missions, the counter-insurgency (COIN) Charger lost its Marine contract bid to the similar, but more powerful, OV-10 Bronco.
Requests tor COIN proposals were issued to 22 manufacturers in October 1963. Responses were received from nine companies: Beech, Douglas, Convair. Goodyear, Helio, Hiller, Lockheed, Martin and North American. The Beach design was designated PD-183 and was to be equipped with the same two engines as the Charger, Canadian T74/PT-6A Turbo-props. The Douglas design designated D-855 was a single fuselage design characterized by a T-shaped tail unit, and a rear loading door. It was drafted to utilize either United Aircraft of Canada T74/PT6-As or Garret AiResearch T76 turboprops. The most interesting, yet somewhat similar design to the Convair Charger and North American OV-10 Bronco was the Martin entrant. It was designed around two T74/PT6-As in twin booms, but instead of a T-tail as used by Convair and North American, the Martin design utilized an inverted V empennage with boundary layer controls.
The Convair Model 48 "Charger" COIN type STOL aircraft had two propellers driven by turbine engines, and double-hinged, single-slotted flaps to deflect the slipstream on the largely immersed wing. It was capable of good low-speed performance and had acceptable handling qualities in the STOL regime (with landing and take-off distances consistently less than 800 feet over a 50-foot obstacle), provided the possibility of engine failure was ignored. This performance was achieved, despite flaps with only medium effectiveness, because the aircraft had a low aspect ratio, a high power loading, and a "no-flare" landing gear design. The performance of the aircraft compared favorably with that of a large four-engined STOL aircraft, which was much more sophisticated (it included a fail-safe propulsion system). If flown above above the minimum single-engine control speed, however, in compliance with the normal safety restrictions for twin-engine airplanes, major aspects of the performance of the aircraft were no better than that obtainable with many small "twins" then in current production and most of the original objectives of the COIN concept are compromised.
The aircraft had two 650 SHP engines driving opposite rotation, 9-foot-diameter propellers; the tips rotated upward in the center. Retractable Krueger flaps were used on the inboard leading edges of the wing which was largely immersed in the propeller slipstream. The 44-percent chord trailing-edge flap was single slotted and double hinged, and was deflected 60°/30 for the landing approach and 2Oo/O0 for take-off. The control system was entirely mechanical; lateral control was obtained with circular-arc spoilers only and longitudinal control with a free-floating, single-hinged (geared, camber-changing) horizontal tail (called a stabilator). The twin rudders were conventional.
To meet the "single-engine survivability" requirement, Convair engineers incorporated a "torque-equalizer" device to reduce the power on one engine automatically in the event the other failed, thereby allowing the pilot to hold the wings near-level long enough to eject safely; this device was operable during all the NASA flight tests in the STOL regime (with the exception, of course, of the single engine investigations). The high-speed performance of the airplane did not meet the original expectations, but comparison with other aircraft indicates that careful attention to detailed improvements would probably net a reasonable cruise performance with no appreciable penalty in the low-speed regime.
For more than two years prior to the Navy issuing RFP (Request for Proposal) in 1964, Convair engineers had been evaluating designs for use in the limited war and counter-insurgency arenas. These designs were evaluated by many military and civilian representatives of the armed forces and Department of Defense. Shortly after the Navy issued a procurement invitation on 28 October 1963, the design was formalized. Once approved, it only took 40 weeks from go-ahead until first flight on 29 November 1964. Even though a prototype was flying shortly after the requirement was published, North American won the contract with a paper airplane, the OV-10 Bronco.
convair-48-line1.gif"> http://www.transchool.eustis.army.mil/museum/transportation%20museum/avrocar.htm VZ-8P AirGeep / Model 59K Sky Car
In 1957, Piasecki Aircraft was awarded an Army Transportation Command contract to develop a "flying jeep." It was to be a VTOL (Vertical Take-Off and Landing) vehicle capable of operating at low altitudes at speeds up to 70 mph to deliver atomic weapons. The first model was the Model 59K Sky Car, built around two tandem, three-bladed, ducted rotors driven by two 180 hp Lycoming piston engines. It had fairly conventional helicopter-type controls that provided directional stability. The landing gear was a fixed tricycle wheel, and the vehicle accommodated a single pilot and one passenger in seats located between two rotor ducts. The first Model 59K Sky Car ordered by the Army made its initial free flight in October 1958. Piasecki renamed it the Airgeep, and turned it over to the Army shortly thereafter, and the Army designated it the VZ-8P. The Army upgraded the engine to a more powerful turbine engine, and test flew it in June 1959.
Piasecki wanted to build a more efficient Airgeep, and the Army Transportation Research Command agreed to issue them another contract. The result was the VZ-8P (B) Airgeep II. The Airgeep II made its first non-tethered flight in the summer of 1962. It was similar in design to the first Airgeep, except that it was bent in the middle so the rotors were tilted, reducing drag in forward flight.
The Airgeep II used twin 400-hp Turbomeca Artouste IIC turbo-shaft engines that were linked, so if one failed the other would drive both rotors. One engine was linked to the landing wheels to move the machine around on the ground. The second model also had ejection seats for both pilot and co-pilot/gunner, and there was additional seating for three passengers.
Neither version of the VZ-8P was dependent upon the surface underneath for flight. Despite the fact that the Airgeeps were intended to operate within a few feet of the ground, both were capable of flying at altitudes of several thousand feet. They were stable and able to hover or fly beneath trees or between buildings. In addition, the Airgeep was surprisingly effective as a weapons platform.
Despite its many positive qualities, the Airgeep, like other ground effects machines developed during this period, was ultimately judged by the Army to be mechanically ill-suited to the rigors of field operations. The "flying jeep" concept was eventually abandoned in favor of further development of conventional battlefield helicopters.
Airships ceased operation in the Navy in 1962 for reasons that continued to arouse controversy. The recognition of an energy shortage in 1974 and the since escalating cost of petroleum resulted in a series of studies hypothesizing second generation airships with "precision hover capability" performing missions which emphasize endurance over speed. When it is assumed that the inherent fuel economy of an airship is not defeated by the implementation of an as yet undefined hoverable propulsive lift system, such vehicles take on high stature as candidate patrol/surveillance platforms. Limited conceptual design studies were conducted by industry under NASA and Navy contracts and suggested, without a great deal of analvtical substantiation, several propulsive lift systems on a conventional non-rigid airship hull.
In the patrol class of mission, long duration on station in a loiter mode drives the design toward a fully buoyant conventional airship, as opposed to a hybrid with aerodynamic lift from a shaped body supplementing the buoyant lift. Ordinarily, the installed power would solely be determined by drag at a transitor dash speed. By stipulating a true VTOL capability at takeoff, the propulsion may be sized by the degree of heaviness that exists at takeoff with full fuel, which in turn is a function of specific fuel consumption, range to station, time on station, and ground rules concerning mid-mission refueling and ballasting.
Typically, the buoyancy ratio (0) at takeoff is abouL 0.85. A propulsive lift system must then provide thrust slightly greater than 15% of the takeoff gross weight, as a minimum. The number and placement of propulsive lift devices is determined by the desire to provide controllability in hover.
Several companies espoused their own preferred configurations. The quadrotor originated by the Piaseeki Aircraft Company, mounted four fixed helicopter rotors for lift, attitude control, and translational thrust. Forward thrust can be augmented by adding propellers which also augments yawing moment control in hover.
Textron, where two diagonally opposed rotors carry a steady DOWN load while the others produce an equal upward force. In this way, significant rotor liftforces are available for cyclic deflection to produce translational forces andyawing moments in a neutrally buoyant state.
The trirotor proposed by the Goodyear Aerospace Corporation has two tilting propellers mounted forward on the hull and a third at the stern. Movable surfaces on an inverted "V" tail supporting the stern propeller,and on the wings supporting the main propellers, provide forces and momentsin the horizontal plane during hover. Hover control diminishes as the buoyancy ratio approaches unity. A notable advantage in the trirotor concept is the low speed cruise efficiency of a stern propeller. To take full advantage of this aspect of the design, the main propellers could be stopped and folded against the nacelles to reduce drag.
One Navy model was initially tested as a twin rotor configuration, using a proportionately scaled propulsion system representing that of the NASA/Bell XV-15 tilt rotor research aircraft. The total static thrust of the XV-15 rotor system is in close proximity to that required for the 0.8-1.1 million cubic foot airships which match proposed maritime ptrol mission profiles. The development of a new engine/rotor for full scale prototyping of an airship was unlikely. The load distribution on the twin-rotor hull is similar to that ofpast conventional airships. Simplicity of the classic airship is least compromised, (fewest added moving parts). All engines and rotors sit relatively low and lend themselves to simplework stands and mobile hoists for maintenance.
Hull Volume 875,000 cu ft Fineness Ratio4.37 Length 321.0 ft Maximum Diameter 74.7 ft Rotor Diameter 25 ft Gross Static Lift 57,500 lbs Empty WeighL 56,800 lbs The increasing number and use of military airships in Germany, France, England, Italy and Russia prompted the US military to take a look at their potential use. In 1908, the Signal Corps contracted for "dirigible number one" which it took possession of in August 1908 at Fort Myer, VA. For the rest of that year and most of the next, the U.S. Army trained several pilots,including Lt. Richard B. Creecy, a U.S. Marine, to fly this, the first US Military airship.
Both the Army and Navy developed viable missions for airships and balloons and by WWI, LTA craft played significant roles at home and abroad. The Army took the lead from France and Britain on the employment of spotter balloons (a tethered free balloon) used to track enemy movements, adjust artillery fire and assess battle damage, among other missions.
The Army also used a floet of airships for the U.S. coastal defense mission. The most notable U.S. Army airship was the non-rigid "TC-13." The TC-13 had every up-to-date feature, including a sub-cloud observation car, fuel and water ballast tanks (either of which could be refilled during flight) and an enclosed gondola. The TC-13 could cover a distance of 1,000 miles at a speed of 65m.p.h., 1,800 miles at 50 mph, and remain in the air forabout 100 hours at a speed of 25 mph.
YEZ-2A Operational Development Model (ODM) Sentinel 1000
During the 1980's, the U.S. Navy conducted in-house analysis and, as a result, let contracts totaling $600,000 for design feasibility studies of airships and $300,000 for large airborne radar systems. The goal was to develop a multi-functioned airship capable of AAW, AEW, ASUW, ASW, ECM, ESM, EW, JSTARS and C3I missions and capable of carrying AAAM missiles to interdictthe cruise missiles in flight and kill air and surface hostile delivery platforms. Additionally, torpedoes would be carried to kill hostile subsurface missile launchers. The confidence of the U.S. Navy, in both the possibility and practicality of such an airship, was demonstrated when they initiated a $200 million program dubbed the Operational Development Model (ODM) Airship Program. On 5 June 1987, NAVAIR awarded the Westinghouse / Airship Industries consortium a $168.9 million firm fixed price contract to build and supply the ODM airship for evaluation by the U.S. Navy." The consortium built an ODM prototype, the "Sentinel 1000," which is a 353,100 ft3 envelope airship. In 1991, Westinghouse Airships launched the 220-foot (68-meter)-long Sentinel 1000, the first in a projected series of blimps intended for use by the U. S. Navy for a range of surveillance, communications, and patrol duties. The envelope of the Sentinel 1000 was made of a mix of synthetic fibers that was impervious to weather and almost invisible to radar. This was to be used in the development of a much larger Sentinel 5000. Disaster struck in 1995 at the Weeksville NC hanger where the ship had been constructed. In the early morning hours of 03 August 1995, Airdock #2 was destroyed by fire during reconstruction of the door supports, causing $100 million in damage. The WAI Sentinel 1000 (largest airship in the world at the time) was destroyed in the hangar at 12:55 AM, and not reconstructed. The airship Hangar at Weeksville, NC was the largest wood construction building in the world, measuring half a mile long by 298' wide by 192' high with 180 ton doors mounted on railroad tracks. Constructed in 1942, it had housed US Navy Airship Squadron ZP-14, which protected Hampton Roads and Outer Banks shipping lanes from German U-Boats. In 1966, the decommissioned facility was sold to Westinghouse. In 1989 Westinghouse moved the aerostat operation to TCOM, LP. Commercial Skyships seen in the U.S.A. such as "Bud One", "Fuji", and "Met Life" were built there. Length 222ft Diameter 54.7 ft Speed 70 mph Volume 353,146 cft YEZ-2A Modern Airship Vehicle (MAV) Sentinel 5000
The YEZ-2A designation was established on 15 December 1987 and assigned to the Navy's operational development model (ODM) airship. Potential use for the YEZ-2A airship was as an organic asset of surface action groups to serve as a fuel-efficient, long-endurance airborne platform for area surveillance and communications, command and control.
The goal of the US Navy "Sentinel 5000" was twice the length and seven times the volume of the Sentinel 1000. Projected performance characteristics and dimensions of the Sentinel 5000 ware a 2.5 million ft3 envelope, with a length of 425 ft, a height of 152 ft, a cruise speed of 88 knots (101 mph), an operating altitude of up to 14,000 ft and an endurance of up to 60 hours. This airship would have a Maximum Structural Disposable Load (MSDL) of 65,000 lbs. The MSDL is the difference between the maximum gross weight and the 'greenship' weight (empty weight ready to fly without mission equipment, usable fuel, furnishings or crew)." Other keyfeatures of this Modern Airship Vehicle (MAV) are the use of modern avionics and computer technology, non-metallic, radar transparent materials, a vectored thrust propulsion system and a fly-by-light control system that will not be affected by the high-energy radar pulses discharged by the ship's radar system. It would be able to carry a crew of 15 in a triple-decked, pressurized gondola.
In 1991, Westinghouse Airships launched the 220-foot (68-meter)-long Sentinel 1000, the first in a projected series of blimps intended for use by the U. S. Navy for a range of surveillance, communications, and patrol duties. The envelope of the Sentinel 1000 was made of a mix of synthetic fibers that was impervious to weather and almost invisible to radar. This was to be used in the development of a much larger Sentinel 5000. However, the prototype was destroyed in a hangar fire in 1995, effectively ending the program. Global Skyship Industries, which purchased Westinghouse Airships in 1996, owns and operates airships for commercial advertising, military, and government applications in a number of locations worldwide.
The difficulty in modeling airships arises from the different geometries, compositions, and projected flightpatterns that are not native to conventional aircraft. Airships are lighter-than-air aerial vehicles having uniqueproperties that affect their dynamics including the effects of buoyant forces and the virtual mass and inertias.Additionally, the center of volume is far from the center of mass causing the system to act as a pendulum, oscillating unnecessarily if the system is not controlled properly. The variety of operations that the airship must perform alsopresents difficulties in creating a dynamic model of the ship, since it must be able to hover, take off/land, ascend/descend, perform high and low speed travel, and traverse long distances. There is a history of research that addresses the problem of airship dynamic modeling to determine its stability. Stability derivatives were used to create linear equations to analyze the ZR-1 and ZR-4 heavy lifting airships, in both linear and nonlinear operating regimes. In the nonlinear realm, a comprehensive study on stability in airships wasperformed on the YEZ-2A airship for set trim conditions.
Length 423ft Diameter 105ft Height 150ft Speed 70mph (est.) Volume 2,500,000cft
During the late 1940's and 1950's, a characteristic associated with the large, newly invented, polyethylene balloons, was that they were often misidentified as flying saucers. During this period, polyethylene balloons launched from Holloman AFB, generated flying saucer reports on nearly every flight. There were so many reports that police, broadcast radio, and newspaper accounts of these sightings were used by Holloman technicians to supplement early balloon tracking techniques. Balloons launched at Holloman AFB generated an especially high number of reports due to the excellent visibility in the New Mexico region. Also, the balloons, flown at altitudes of approximately 100,000 feet, were illuminated before the earth during the periods just after sunset and just before sunrise. In this instance, receiving sunlight before the earth, the plastic balloons appeared as large bright objects against a dark sky. Also, with the refractive and translucent qualities of polyethylene, the balloons appeared to change color, size, and shape.
The large balloons generated UFO reports based on their radar tracks." This was due to large metallic payloads that weighed up to several tons and echoed radar returns not usually associated with balloons. In later years, balloons were equipped with altitude and position reporting transponders and strobe lights that greatly diminished the numbers of both visual and radar UFO sightings.
Over the years, payloads transported by high altitude polyethylene balloons ranged from simple radio transmitters to anthropomorphic dummies to sophisticated satellite components and NASA interplanetary space probes. Many of these payloads, some of which weighed many tons, were not what someone would typically envision as being associated with a balloon.
Research projects of the late 1940's and 19.50's conducted at Holloman AFB which began with the Project MOGUL flights in June 1947, covered a wide spectrum of scientific research. One important experiment in space biology measured the effects of exposure to cosmic ray particles on living tissues. Other projects gathered meteorological data and collected air samples to determine the composition of the atmosphere. The first high altitude photographic reconnaissance project, a forerunner to today's reconnaissance satellites, Project Il9L, also used high altitude balloons launched at Holloman AFB.
As early as May 1948, polyethylene balloons coated or laminated with aluminum were flown from Holloman AFB and the surrounding arcxni Beginning in August 1955, large numbers of these balloons were flown as targets in the development of radar guided air to air missiles. In 1958 the first manned stratospheric balloon flights were made from Holloman AFB. In 1960, balloon tests of components of the first LJ. S. reconnaissance satellite were also flown at Holloman AFB. In the 1960's, 70's, and 80's high altitude balloons were used in support of Air Force, and other U.S. Government and university sponsored research projects.
http://sites.wff.nasa.gov/code820/balloonsizes.html The scientific balloon program uses helium-filled polyethylene balloons of large volume, typically between about 0.3 and 1.1 million cubic meters (10-40 million cubic feet). The balloons are launched by crews of the National Scientific Balloon Facility (NSBF) from various sites around the world. They float in the stratosphere for periods ranging from about a day to over a month, following trajectories imposed by the wind at the float altitude. On radio command, the flights are terminated over an appropriate location, and the instruments parachute to the ground and are recovered for possible future flight.
"Conventional" balloon flights have durations on the order of a day, and the balloon support system is based on line-of-sight communications. These balloons are launched from the NSBF home base in Palestine, TX; from Ft. Sumner, NM; Lynn Lake, Canada; or Alice Springs, Australia; and their payloads are recovered typically within several hundred miles of the launch site. "Long-Duration Balloon" (LDB) flights have durations from about a week to a month. They use the same balloons employed for conventional flights, but a more sophisticated over-the-horizon balloon support system. They may be launched in Sweden for recovery in northern Canada or Alaska, or from the McMurdo base in Antarctica and recovered within a few hundred miles of McMurdo after traveling around the South Pole once, twice, or even three times. Pending approval for overflight, the flights launched from Sweden could continue over Russia, or flights could be launched from Fairbanks, AK, and recovered in northern Canada after flying westward around the world. These balloons may also be launched in Australia for recovery in South America
Balloons that have been used to date for both conventional and LDB flights are "zero-pressure," meaning that they are vented near the bottom to the outside, so the balloon pressure is in equilibrium with the atmospheric pressure at that point (zero differential pressure). Only a small fraction of the balloon's volume is filled with helium on the ground, and the helium expands as the balloon rises. Excess helium flows out the vents as the balloon reaches its fully inflated float altitude. To avoid serious loss of altitude at sunset, the payload must carry ballast (fine steel or sand grains that can be released by radio command). At night without the solar input, there is a cooling of the helium and consequent shrinking of the balloon volume, which causes the balloon to sink to a very much lower altitude. To reduce the altitude variation at sunset, ballast is dropped. Limitations on the amount of ballast that can be carried limit the number of sunsets a balloon can survive and the extent to which the diurnal altitude variation can be reduced. The longestduration LDB flights are flown during local summer over Antarctica or in the Arctic, where continuous sunlight permits the balloon to keep altitude without need to drop ballast.
Currently under development are "super-pressure balloons," designed to maintain essentially constant volume-day and night-and thus to float at nearly constant altitude without need for dropping ballast at sunset. These balloons are sealed and designed to withstand substantial internal over-pressure. They are inflated with enough helium to fill the volume at the coldest temperatures, and they have enough strength to hold that helium when sunlight heats it. Super-pressure balloons will have two advantages. First, they will permit ULDB flights circumnavigating the globe at any latitude and lasting of the order of a hundred days. Second, they will permit flights of 1-2 week durations at any latitude-say from Australia to South America-without diurnal altitude variation.
The Balloon Program Office (BPO) at the Wallops Flight Facility of Goddard Space Flight Center manages the balloon flight operations. The BPO contracts with NSBF, which carries out the launches and flight operations, including flights launched both at the NSBF home in Palestine, TX, and at remote sites. The BPO also carries out a research and development program to advance the capabilities of scientific ballooning. With its current annual budget of approximately $25M, the BPO supports about 15 conventional flights, 2 polar LDB campaigns (one Antarctic and one Arctic), and 1 midlatitude LDB campaign (flights between Alice Springs, Australia and South America). Each of these LDB campaigns has the capability for two balloon flights (however, at least through FY07, one of these foreign campaigns will be cancelled to pay off a 2004 advance for costs associated with upgrades of Antarctic facilities).
The InFOCmS payload at float altitude over Arizona. The six tubes hanging down from the balloon are vent tubes, through which excess helium vents to the air.
Typically, stratospheric scientific balloons have floated at altitudes of about 36.5-39.5 km, where the residual atmospheric pressure is in the range of approximately 4.5-3 millibars (mbar). (Sea level pressure is approximately 1 bar, i.e., 1000 mbar.) Recently a 200-kg instrument was successfully flown on a 1.7 million cubic meter (60 million cubic foot) balloon to an altitude of 49 km, where the residual atmosphere is less than 1 mbar. The The ability to fly 1-ton instruments at less than 1 mbar residual atmosphere would enable a wide range of ultraviolet observations, including solar studies of the magnetic transition zone and improved measurements of solar irradiance. This high-altitude capability would enable much improved x-ray, gamma-ray, and cosmicray studies. The Raven Industries 40 million cubic foot balloon is 450 ft in diameter at 130,000 feet. The largest balloon ever used in x-ray astronomy experiments, a 34 million ft3 Skyhook balloon, carried a new payload to altitudes over 45 kilometers. Carrying a Japanese-built instrument, NASA's largest balloon -- 39 million cubic feet (1.1 million cubic meters) in volume and 60 stories high -- lifted off Aug. 16, 1999 from Lynn Lake, Manitoba, Canada, at 9:22 a.m. EDT Aug. 11 for a 38-hour flight more than 20 miles above Earth. The 5,000-pound instrument was recovered Aug. 12 and was prepared for another flight the following year. The BESS project (Balloon-borne Experiment with a Superconducting Solenoidal magnet), led by Prof. Shuji Orito of the University of Tokyo, was sponsored in the U.S. by NASA and by Monbusho in Japan. A highly successful first flight of the Isotope Magnet Experiment (ISOMAX) was launched from Lynn Lake, Manitoba, Canada. ISOMAX flew near the topof the Earth's atmosphere, at an altitude of 38 km (126,000ft), carried by a huge 1.1 million m3 (39 million ft3) heliumballoon. At full expansion, this balloon was about 64 m (210ft) in diameter and at launch the balloon system is taller than an 80 story building.
The National Scientific Balloon Facility, managed for NASA by New Mexico State University's Physical Science Laboratory, has successfully completed the flight of the largest balloon ever launched. The balloon, which carried a 1,500-pound payload of scientific equipment, was launched by the NSBF Sunday, Aug. 25, 2002 from Lynn Lake, Manitoba, Canada, and landed at 4 p.m. Monday, Aug. 26, about 20 miles southeast of Fort McMurray, Alberta, Canada. Its payload was in excellent condition and was being recovered by the facility's staff Tuesday afternoon. The balloon is 750 feet tall, uninflated, and has a volume of 60 million cubic feet. NASA's largest standard balloon has a volume of 40 million cubic feet. This record-setting balloon reached a peak altitude of 161,000 thousand feet, compared to the standard balloon's peak altitude of 130,000 feet. At 160,000 feet, 99.999 percent of the atmosphere is below. That can have serious benefits for x-ray astronomy and high energy astrophysics. There's no degradation of data from looking through the atmosphere and there's an unobstructed view of the universe. The new balloon has an ultra-thin polyethylene shell that is filled with helium. The polyethylene material that composes its shell is twice as thin as that on standard balloons. Where the polyethylene shell on standard balloons is eight-tenths of a mil, the skin of the new balloon is four-tenths of a mil. A mil is one-thousandth of an inch.
Polyethylene balloons flown by the U.S. Air Force have reached altitudes of 170,000 feet and lifted payloads of 15,000 pounds.
"http://www.tx.ncsu.edu/jtatm/volume3issue4/Articles/Seyam/seyam_full_80_03.pdf">Giant Vehicles Journal of Textile and Apparel, Technology and Management Modem scientific ballooning began in the late 1940's. Developments in the past twenty years have brought about significant increases in the reliability of scientific balloon vehicles and operations. Important discoveries in the atmospheric science, space science, and astronomy.
http ://lheawww.asfc.nasa. ,gov/docs/balloon/balloon tophtml (NASA Scientific Ballooninghomepage) http ://www.wff.nasa. gov/-code820/ (NASAScientific Ballooning Info Page) http ://www.nsbf.nasa. gov/index.html (WSBFhomepage) http ://topweb. psfc nasa. govlballoodindex.htm1 http ://www.ess.washine;ton.edu/Space/SpaceExp/Balloon/ hm ://www. isas. ac. i p/e/enterp/ball/index. shtml http://www,centennialofflight.gov/essay/Lightetrhan aidearly scientific balloonsLTA7.htm h Q ://www.centennialofflight .gov/essay/Dictionaryiscientific Balloons/DI72.htin(balloon types) http ://www.gaerospace.codproj ects/S tratocodstratcon presentations.htm1 (Trajectory control) http ://www.gaerospace.com/proi ects/ULBDS tratoSailiIJLDB balloon trai ectow.htm1 (Trajectorycontrol http://www.dod.gov/pubs/foi/ufo/ http://muller.lbl.gov/teaching/Physics10/old%20physics%2010/chapters%20(old)/9-SecretsofUFOs.html "http://muller.lbl.gov/teaching/physics10/roswell/usmogulreport.html">Report on Project Mogul Synopsis of Balloon Research Findings http://contrails.iit.edu/history/roswell/
Project Mogul
The concept of Project Mogul was to explore the feasibility of using balloon-borne acoustic sensors for long-range detection of potential Soviet missile launches and atomic tests. Project Mogul was a then-sensitive, classified project, whose purpose was to determine the state of Soviet nuclear weapons research. This was the early Cold War period and there was serious concern within the US government about the Soviets developing a weaponized atomic device. Because the Soviet Union's borders were closed, the US Government sought to develop a long range nuclear explosion detection capability.
Project Mogul derived from a suggestion of Professor Maurice Ewing of Columbia University that one might find acoustic ducts in the atmosphere analogous to deep sound channels underwater. Project Mogul was managed out of the AAF's Watson Laboratories and headed by Capt Albert Trakowski. B-29 bombers, balloons and ground sites at the White Sands Proving Ground in New Mexico detonated high explosives in sound-monitoring experiments. The project also monitored American nuclear tests in the Pacific, including the Sandstone series of 1948. When the Soviets detonated their first atomic bomb in August 1949. Mogul detected it.
But overall, this approach did not prove fruitful. High-level winds often pushed the balloons out of range of radio communications with the ground. Government research showed that sound waves from distant blasts could be monitored on the ground. The United States ran such a system around the globe.
Since 1947, U.S. Air Force research organizations at Holloman AFB, N.M., launched and recovered approximately 2,500 high altitude balloons. The Air Force organization that conducted most of these activities, the Holloman Balloon Branch, launched a wide range of sophisticated, and from most perspectives, odd looking equipment into the stratosphere above New Mexico. In fact, the veryfirst high altitude data gathering balloon flight launched from Alamogordo Army Airfield (now Holloman AFB), NM., on June 4, 1947, was found by the rancher and was the first of many unrelated events now collectively known as the "Roswell Incident."
On July 7, 1947, W.W. (Mac) Brazel, a rancher from approximately 75 miles northwest of Roswell, NM, contacted the local sheriff and reported that some metallic debris had come to rest on the ranch on which he worked near the town of Corona, NM. This was during the "UFO Wave of 1947," and he told the sheriff that he thought this debris may be part of a "flying disc." The following day, the Public Information Office released a statement saying that the Army Air Forces had recovered a flying disc. This press release was provided to local newspapers who sent it out to wire services.
Brig Gen Roger Ramey, Eighth Air Force Commander, ordered that the debris be flown to Eighth Air Force Headquarters at Fort Worth AAF, TX, for his personal inspection. Upon viewing the debris, he and his staff recognized parts which looked similar to a weather balloon. He then summoned the base weather officer, who identified the debris as the remnants of a weather balloon and its attached metallic radar target. General Ramey then invited the local press to view and take photographs of the materials and he declared the episode to be a misunderstanding.
On December 17, 1969, the Secretary of the Air Force announced the termination of Project BLUE BOOK, the Air Force program for the investigation of UFOS. From 1947 to 1969, a total of 12,618 sightings were reported to Project BLUE BOOK. Of these 701 remained "Unidentified." The decision to discontinue UFO investigations was based on an evaluation of a report prepared by the University of Colorado entitled, "Scientific Study of Unidentified Flying Objects;" a review of the University of Colorado's report by the National Academy of Sciences; past UFO studies and Air Force experience investigating UFO reports during the 40s, '50s, and '60s.
From the rather benign description of the "event" and the recovery of some material as described in the original newspaper accounts, the "Roswell Incident" has since grown to mythical (if not mystical) proportions in the eyes and minds of some researchers, portions of the media and at least part of the American public. UFOlogists had long argued that, following a flying saucer crash in New Mexico in 1947, the government not only recovered debris from the crashed saucer but also four or five alien bodies. According to some UFOlogists, the government clamped tight security around the project and has refused to divulge its investigation results and research ever since. In 1978, the UFO researcher Stanton Friedman met with Major Jesse A. Marcel, who had recovered the "flying disc", and began investigating the claims that the material Marcel handled was from a crashed UFO. Similarly, two authors, William L. Moore and Charles Berlitz, also engaged in research which led them to publish a book, The Roswell Incident, in 1980.
Around 1984, a series of documents surfaced which some UFOlogists said proved that President Truman created a top secret committee in 1947, Majestic-12, to secure the recovery of UFO wreckage from Roswell and any other UFO crash sight for scientific study and to examine any alien bodies recovered from such sites. Most if not all of these documents have proved to be fabrications. There are also now several major variations of the "Roswell story." Most versions now claim that there were two crash sites where debris was recovered; and at the second site, alleged bodies of extraterrestrial aliens were supposedly retrieved [and transported to Area 51, as related in the movie Independence Day].
The major works regarding the "Roswell Incident" include: The Roswell Incident, (1980) by William Moore and Charles Berlitz; "Crashed Saucers: Evidence in Search of Proof," (1985) by Moore; The UFO Crash at Roswell, (I 99 1) by Kevin Randle and Donald Schmitt; The Truth About the UFO Crash at Roswell, (1994) also by Randle and Schmitt; The Roswell Report: A Historical Perspective, (1991), George M. Eberhart, Editor; "The Roswell Events," (1993) compiled by Fred Whiting- Crash at Corona (1992) by Stanton T. Friedman and Don Berliner.
Dr. Maurice Ewing of Columbia University, NY, and Woods Hole Oceanographic Institution, MA had conducted considerable research for the Navy during World War II, studying, among other things, the "sound channel" in the ocean. He proved that explosions could be heard thousands of miles away with underwater microphones placed at a predetermined depth within the sound channel. He theorized that since sound waves generated by explosions could be carried by currents deep within the ocean, they might be similarly transmitted within a sound channel in the upper atmosphere. The military application of this theory was the long-range detection of sound waves generated by Soviet nuclear detonations and the acoustical signatures of ballistic missiles as they traversed the upper atmosphere.
Project MOGUL branched out into many areas related to the geophysical properties of the upper atmosphere, including radiowave propagation, radar propagation, ionospheric physics, solar physics, terrestrial magnetism, meteorological physics, and weather forecasting. Considerable resources were devoted to Project MOGUL which included numerous bomber and transport aircraft and two oceangoing vessels. At one point the staff, exclusive of contractors, numbered over 100 persons.
The NYU group was responsible for developing constant level balloons and telemetering equipment that would remain at specified altitudes (within the acoustic duct) while a group from Columbia was to develop acoustic sensors. The NYU constant altitude balloon Director of Research was Dr. Athelstan F. Spilhaus; the Project Engineer, Professor Charles B. Moore; and the military Project Officer, Colonel Albert C. Trakowski. From September 30, 1946, until December 31, 1950, the Research Division of the College of Engineering of NYU conducted research under contract for the Army Air Forces, in conjunction with Project MOGUL. Research flights tested balloon controls and telemetering systems and were fully reported in the unclassified NYU reports. A total of 110 research flights were flown during the contract. Service flights were flown at the direction of Watson Laboratory personnel, but the military purpose was Top Secret.
Ewing's idea was to string the microphones under a high-altitude balloon, have them pick up the sounds in the sound channel, and radio them back to the ground. The disk microphones were called "flying disks." The word flying was not confined to airplanes; it was equally used by ballooners when they went up. The balloons were huge, and the string of microphones was 657 feet long, longer than the Washington Monument is high.
Neoprene balloons used initially were susceptible to degradation in the sunlight, turning from a milky white to a dark brown. Balloons most suitable for this type of work were made of polyethylene, a very thin, translucent plastic. These balloons, however, had just been developed by 1947. In 1946, as a result of research conducted for project MOGUL, Charles B. Moore, a New York University graduate student working under contract for the U.S. Army Air Forces, made a significant technological discovery: the use of polyethylene for high altitude balloon construction. Polyethylene is a lightweight plastic that can withstand stresses of a high altitude environment that differed drastically from, and greatly exceeded, the capabilities of standard rubber weather balloons used previously.
Moore's discovery was a breakthrough in technology. For the first time, scientists were able to make detailed, sustained studies of the upper atmosphere. Polyethylene balloons, first produced in 1947 for Project MOGUL, are still widely used today for a host of scientific applications. High altitude polyethylene balloons and standard rubber weather balloons differ greatly in size, construction, and utility. The difference between these two types of balloons historically has been the subject of misunderstandings in that the term "weather balloon" is often used to describe both types of balloons.
The newly developed polyethylene balloons replaced the neoprene meteorological balloons. The debris found by the rancher and was subsequently identified as a "flying disc" by personnel from Roswell AAF was, with a great degree of certainty, MOGUL flight no. 4, launched on June 4, 1947. This was not an ordinary "weather balloon." Typical weather balloons employed a single, 350-gram neoprene balloon and a radiosonde for measuring temperature, atmospheric pressure, and humidity, housed in a cardboard box.
The balloon that was found on the Foster Ranch consisted of as many as 23 350-gram balloons spaced at 20 foot intervals, several radar targets (3 to 5), plastic ballast tubes, parchment parachutes, a black "cutoff" box containing portions of a weather instrument, and a sonabuoy. After striking the ground, the radar reflectors, constructed of very light materials for minimum weight, would tear and break apart, spreading out over a large area when pulled across the ground by balloons that still possessed some buoyancy. It should also be understood that the term "flying disc" was not at this time synonymous with "space ship," It denoted a disc-shaped flying object of unknown (or suspected Soviet) origin.
By December 1948, serious concerns had arisen regarding the feasibility of the project as first conceived. Even though the principle on which the project was based was determined to be sound, questions concerning cost, security, and practicality were discussed-that ultimately led to the disbandment of the project, and Project MOGUL as first conceived was never put into operational use. However, MOGUL did serve as the foundation for a comprehensive program in geophysical research from which the USAF and the scientific community have benefited to the present time.
In July 1994, the Office of the Secretary of the Air Force concluded an exhaustive search for records in response to a General Accounting Office (GAO) inquiry of an event popularly known as the "Roswell Incident." The focus of the GAO probe, initiated at the request of New Mexico Congressman Steven Schiff, was to determine if the U.S. Air Force, or any other U.S. government agency, possessed information on the alleged crash and recovery of an extraterrestrial vehicle and its alien occupants near Roswell, N.M. in July 1947. Reports of flying saucers and alien bodies allegedly sighted in the Roswell area in 1947, have been the subject of intense domestic and international media attention.
The July 1994 Air Force report concluded that the predecessor to the U.S. Air Force, the U.S. Army Air Forces, did indeed recover material near Roswell in July 1947. This 1,000-page report methodically explains that what was recovered by the Army Air Forces was not the remnants of an extraterrestrial spacecraft and its alien crew, but debris from an Army Air Forces balloon-borne research project code named MoGUL. Records located describing research carried out under the MoGUL project, most of which were never classified (and publicly available) were collected, provided to GAO, and published in one volume for ease of access for the general public.
On 24 June 1997, as the 50th anniversary of the alleged alien sighting neared, the U. S. Air Force released a 231 page report entitled The Roswell Report: Case Closed. The report explained that the U.S. Air Force had recovered test dummies from the Roswell, New Mexico, crash site in 1947, rather than the bodies of aliens. The U.S. Air Force had issued a report on the Roswell matter in 1994, in which researchers argued that the presumed spacecraft that had crashed in 1947 was actually an Air Force balloon used in a top-secret program called Project Mogul. When officials discovered evidence that the tests had used parachute dummies, however, the U.S. Air Force compiled an additional report with the new information. Military officials hoped that the Air Force's explanation for the supposed UFO reported in 1994, as well as for the supposed bodies of aliens discovered in the crash, would temper the controversy surrounding the issue.
U.S. Air Force Colonel John Haynes, presiding over the Pentagon news conference at the release of the report, showed reporters footage of a NASA test craft that, indeed, resembled a flying saucer. Colonel Haynes explained that during testing in the 1950s, Air Force balloons had transported dummies to altitudes of 98,000 feet (29,900 meters), releasing them to fall to the ground. Since the testing was secret, the sight of falling dummies "easily could have been mistaken for something they were not."
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