F-15 Eagle

Design

The McDonnell Douglas F-15 Eagle emerged from the complex and extensive set of requirements established by the USAF. Configuration of the twin-engine aircraft is characterized by a high-mounted wing, twin vertical tails mounted at the rear of the short fuselage, and large, horizontal-ramp variable- geometry external-compression inlets located on the sides of the fuselage ahead of the wing. The horizontal-tall surfaces are mounted in the low position on fuselage extensions on either side of the exhaust nozzles.

Propulsion of the F-15 is supplied by two Pratt & Whitney F100-PW-100 afterburning turbofan engines of 23,904/14,780 pounds thrust each. Developed especially for the F-15, these high-pressure-ratio engines are reported to have much improved efficiency over earlier engines for fighter aircraft.

The wing planform of the F-15 suggests a modified cropped delta shape with a leading-edge sweepback angle of 45°. Ailerons and a simple high-lift flap are located on the trailing edge. No leading-edge maneuvering flaps are utilized, although such flaps were extensively analyzed in the design of the wing. This complication was avoided, however, by the combination of low wing loading and fixed leading-edge camber that varies with spanwise position along the wing. Airfoil thickness ratios vary from 6 percent at the root to 3 percent at the tip.

To succeed in the air-to-air role, a plane needs the right airframe in combination with strong powerplant and avionics. The plane's designers understood this and stretched technology to the limits. It was determined that a very low wing loading combined with heavy thrust from the engines would be required. US fighter aircraft of the period were going faster (Mach 2 plus), but were heavy and lacked maneuverability compared to their Soviet counterparts. When combined with a capable airframe, better maneuverability can be achieved by maximizing thrust, thereby maximizing energy. The Pratt & Whitney F100 Turbofan engine provides the needed thrust. Each engine is capable of producing 15,000 pounds of thrust at maximum power, and 25,000 pounds of thrust in afterburner. This gives the Eagle a total of 50,000 pounds of thrust. In other words, a nominally loaded F-15 Eagle of 48,000 pounds has a thrust-to-weight ratio of 1.04 pounds of thrust to each pound of aircraft weight. Thrust of this caliber allows an F-15 to accelerate while going straight up! A specially modified F-15A Eagle known as the "Streak Eagle" was able to outclimb a Saturn V Moon Rocket to almost 60,000 feet. This same aircraft flew to 98,430 feet (30,000 meters) in 207.80 seconds (less than 3 minutes and 30 seconds).

The wing loading of the F-15 is significantly lower and the thrust loading much greater than corresponding values for earlier fighter aircraft. At the lower weights to be expected during combat, wing loadings as low as 55 pounds per square foot and static thrust-to-weight-ratios of as much as 1.35 might be expected. (As the Mach number increases at a given altitude, the thrust of the afterburning turbofan also increases. For example, the thrust of the F-15 engine at sea level and Mach 0.9 is nearly twice the sea-level static value.) The values of these parameters represent a significant departure from previous fighter design philosophy and resulted from the energy-maneuverability concepts employed in specifying the aircraft.

To understand the design of the F-15 and its unique capabilities, some insight into the meaning of maneuverability and its relation to several aircraft design parameters is necessary. The maneuvering capability of an aircraft has many facets, but one of the most important of these is its turning capability. In a combat situation between two opposing fighters flying at the same speed, the aircraft capable of turning with the shortest radius of turn without losing altitude usually has the advantage. This assumes equality of many other factors such as aircraft stability and control characteristics, armament, and, of course, pilot skill.

In steady, turning flight the lift developed by the wing must balance not only the weight of the aircraft but the centrifugal force generated by the turn. (The term "balance" is used here in a vector sense; that is, the lift vector must equal the sum of the weight and centrifugal force vectors.) The load factor is defined as the ratio of the lift in the turn to the weight of the aircraft and is usually expressed in g units, where g is the acceleration due to gravity. Thus, a 2-g turn is one in which the wing must develop a lift force twice the weight of the aircraft. The value of the load factor is uniquely defined by the aircraft angle of bank. For example, 2-g and 5-g turns require bank angles of 60 and 78.5 respectively. Finally, for a given bank angle and thus load factor, the turning radius varies as the square of the speed; for example, doubling the speed of the aircraft increases the turning radius by a factor of 4. It would then appear that two different aircraft flying at the same speed would have the same turning radius; however, this conclusion is not necessarily correct. The maximum load factor and associated turning radius may be limited by wing stalling. For a given speed and altitude, stalling occurs as a function of the wing maximum lift coefficient and the wing loading in straight and level flight. Clearly then, the turning capability of different aircraft types may vary widely.

Two other important aircraft physical parameters may also limit turning performance. First, at a given speed and altitude, the aircraft drag increases rapidly with lift coefficient; as a consequence, the available thrust may not be sufficient to balance the drag at some load factors that the wing can sustain. In this case the aircraft loses altitude in the turn, an undesirable situation in combat. As for maximum lift coefficient, the drag rise with increasing lift depends upon the wing design and Mach number, as well as upon the added drag required to trim the aircraft at high lift coefficients. Finally, the turning performance may be limited by the control power available in the horizontal tail for trimming the aircraft at the high maneuvering lift coefficients.

These ideas are embodied in a technique for describing and specifying fighter aircraft maneuverability. Known by the term "energy maneuverability," the technique involves the specification of desired aircraft climb and/or acceleration capability for various combinations of speed, altitude, and turning load factor. The quantity specified for each of these combinations is labeled "specific excess power" Ps and is simply the excess power available per unit aircraft weight as compared with the power required to maintain constant altitude in the turn.

The lightly loaded airframe is combined with an equally impressive flight control system. A hydraulically actuated, mechanically controlled flight control system is augmented by an electronic system known as the Control Augmentation System (CAS). This system takes the stick inputs from the pilot and deflects the flight controls in the proper direction at the proper rate for optimal aircraft handling. This system allows the pilot to fly the aircraft to the limits of its capabilities without losing control of the aircraft. The CAS can also actuate the flight controls via pilot input if the hydro-mechanical system is damaged.

In order to win air-to-air battles, the pilot must be able to see, shoot, evade, and destroy the adversary first. The Eagle has an impressive array of weapons and avionics which allow it to get the advantage. The APG-63 and 70 radars allow crews to see targets that are as far away as 100 miles. These "Eyes" are able to ferret out the targets even if the targets are flying at high speeds at low altitudes. A Tactical Electronic Warfare System (TEWS) lets the aircrew know if any threat is present. The Heads-up-Display (HUD), and the Hands on Throttle and Stick (HOTAS), allow the Pilot to select, track and shoot the adversary without having to look back into the cockpit.

The F-15's versatile pulse-Doppler radar system can look up at high-flying targets and down at low-flying targets without being confused by ground clutter. It can detect and track aircraft and small high-speed targets at distances beyond visual range down to close range, and at altitudes down to tree-top level. The radar feeds target information into the central computer for effective weapons delivery. For close-in dog fights, the radar automatically acquires enemy aircraft, and this information is projected on the head-up display.

In addition to the F-15C AESA, Raytheon is developing AESAs for the F/A-18E/F Super Hornet. The Boeing Phantom Works unit led a team that received a $250 million contract to install the AESA radar, upgrade the aircraft's environmental control systems and install an advanced identification friend or foe system. Honeywell Aerospace and BAE Systems, respectively, provided the latter systems. The Air Force F-15 System Program Office's Projects Team at Wright-Patterson Air Force Base, Ohio, managed the program for the U.S. government.

An inertial navigation system enables the Eagle to navigate anywhere in the world. It gives aircraft position at all times as well as pitch, roll, heading, acceleration and speed information.

The F-15's electronic warfare system provides both threat warning and automatic countermeasures against selected threats. The "identification friend or foe" system informs the pilot if an aircraft seen visually or on radar is friendly. It also informs U.S. or allied ground stations and other suitably equipped aircraft that the F-15 is a friendly aircraft.

The Fiber Optic Towed Decoy (FOTD) provides aircraft protection against modern radar-guided missiles to supplement traditional radar jamming equipment. The device is towed at varying distances behind the aircraft while transmitting a signal like that of a threat radar. The missile will detect and lock onto the decoy rather than on the aircraft. This is achieved by making the decoy's radiated signal stronger than that of the aircraft.

A variety of air-to-air weaponry can be carried by the F-15. An automated weapon system enables the pilot to perform aerial combat safely and effectively, using the head-up display and the avionics and weapons controls located on the engine throttles or control stick. When the pilot changes from one weapon system to another, visual guidance for the required weapon automatically appears on the head-up display.

The Eagle can be armed with combinations of four different air-to-air weapons: AIM-7F/M Sparrow missiles or AIM-120 Advanced Medium Range Air-to-Air Missiles on its lower fuselage corners, AIM-9L/M Sidewinder or AIM-120 missiles on two pylons under the wings, and an internal 20mm Gatling gun (with 940 rounds of ammunition) in the right wing root.

The current AIM-9 missile does not have the capabilities demonstrated by foreign technologies, giving the F-15 a distinct disadvantage during IR dogfight scenarios. AIM-9X integration will once again put the F-15 in the air superiority position in all arenas. The F-15/AIM-9X weapon system is to consist of F-15 carriage of the AIM-9X missile on a LAU-128 Air-to-Air (A/A) launcher from existing AIM-9 certified stations. The AIM-9X will be an upgrade to the AIM-9L/M, incorporating increased missile maneuverability and allowing a high off-boresight targeting capability.

Low-drag, conformal fuel tanks were especially developed for the F-15C and D models. Conformal fuel tanks can be attached to the sides of the engine air intake trunks under each wing and are designed to the same load factors and airspeed limits as the basic aircraft. Each conformal fuel tank contains about 114 cubic feet of usable space. These tanks reduce the need for in-flight refueling on global missions and increase time in the combat area. All external stations for munitions remain available with the tanks in use. AIM-7F/M Sparrow and AIM-120 missiles, moreover, can be attached to the corners of the conformal fuel tanks.

Conformal Fuel Tanks [CFT] are carried in pairs and fit closely to the side of the aircraft, with one CFT underneath each wing. By designing the CFT to minimize the effect on aircraft aerodynamics, much lower drag results than if a similar amount of fuel is carried in conventional external fuel tanks. This lower drag translate directly into longer aircraft ranges, a particularly desirable characteristic of a deep strike fighter like the F-15E.

As with any system, the use of CFTs on F-15s involves some compromise. The weight and drag of the CFTs (even when empty) degrades aircraft performance when compared to external fuel tanks, which can be jettisoned when needed (CFTs are not jettisonable and can only be downloaded by maintenance crews). As a result, CFTs are typically used in situations where increased range offsets any performance drawbacks; for example, F-15s flying alert missions out of Keflavik, Iceland often encounter unforseen weather changes forcing them to fly more than 500 miles to an alternate landing field in Scotland or Norway. In the case of the F-15E, CFTs allow air-to-ground munitions to be loaded on stations which would otherwise carry external fuel tanks. In general, CFT usage is the norm for F15Es and the exception for F-15C/D's.

Specifications
Variant	C/D models	E/F models
Primary Function	Tactical fighter.	Tactical Bomber
Contractor	Boeing (McDonnell Aircraft and Missiles Systems)	Boeing (McDonnell Aircraft and Missiles Systems)
Power Plant	Two Pratt & Whitney F100-PW-100 turbofan engines with afterburners, each rated at 25,000 pounds engine ( 11,250 kilograms)	two Pratt and Whitney FIOO-P-220 turbofans each rated at 14,670 lb st (65.26 kN) dry and 23,830 lb st (106.0 kN) with afterburning or, after August 1991, two FlOO-PW-229 each rated at 17,800 lb st (79.18 kN) dry and 29,100 lb st (129.45 kN) with afterburning;
Length	63 feet, 9 inches (19.43 meters).	63 ft 9 in (19.43 m)
Height	18 feet, 8 inches (5.69 meters).	18 ft 5.5 in (5.63 m)
Wingspan	42 feet, 10 inches (13.06 meters)	42ft 9.75 in (13.05 m)
Wing aspect ratio		3.01
Wing area		608.00 sq ft (56.48 m2)
Speed	1,875 mph (Mach 2.5-plus).	1,433 kt (1,650 mph; 2655 km/h) maximum level speed 'clean' at high altitude 495 kt (570 mph; 917 km/h) cruising speed at optimum altitude
Ceiling	65,000 feet (19,697 meters).	60,000 ft (18290 m);
Operating Empty Weight		31,700 lb (14379 kg)
Maximum Takeoff Weight	68,000 pounds (30,600 kilograms).	81,000 lb (36741 kg)
fuel		13,123 lb (5952 kg) internal 21,645 lb (9818 kg) in two CFTs up to three 610-US gal (2309-liter~ drop tanks;
Range	3,450 miles (3,000 nautical miles) ferry range with conformal fuel tanks and three external fuel tanks.	3,100 nm (3,570 miles; 5745 km) ferry range with CFTs and drop tanks 2,400 nm (2,765 miles; 4445 km) with drop tanks 1,000 nm (1,150 mi; 1,853 km) Max Combat Radius 685 nm (790 miles; 1270 km) combat radius
Systems	AN/APG-63 X-band pulsed-Doppler radar [Hughes] AN/APG-63 V2 AESA X-band pulsed-Doppler radar [Raytheon] [ on F-15C/D] AN/APG-63 V3 AESA X-band pulsed-Doppler radar [Raytheon] [ on F-15C/D, F-15SG] AN/APG-70 X-band pulsed-Doppler radar [Hughes] [ on F-15E, F-15C/D, F-15A/B MSIP] AN/APX-76 IFF interrogator [Hazeltine] AN/ALQ-135(V) internal countermeasures system AN/ALQ-128 radar warning[Magnavox] suite AN/ALR-56 radar warning receiver (RWR) [Loral] AN/ALE-45 chaff/flare dispensers[Tracor]	AN/APG-70 X-band pulsed-Doppler radar [Hughes] [ on F-15E, F-15C/D, F-15A/B MSIP] AN/APG-63 V3 AESA X-band pulsed-Doppler radar [Raytheon] [ on F-15C/D, F-15SG] AN/APG-82 AESA X-band pulsed-Doppler radar [Raytheon] [ on F-15E] AN/AVQ-26 Pave Tack AN/AXQ-14 Data Link System LANTIRN AN/APX-76 IFF interrogator [Hazeltine] AN/ALQ-135(V) internal countermeasures system AN/ALQ-128 radar warning [Magnavox] suite AN/ALR-56 radar warning receiver (RWR) [Loral] AN/ALE-45 chaff/flare dispensers[Tracor]
Crew	F-15A/C: one. F-15B/D: two.	two
Unit cost $FY98 [Total Program]	$43 million.	probably around $55 million for USAF close to $100 million (including spares and support) for export customers.
Date Deployed	July 1972	April 1988
Fuselage Lifetime	8,000 hours	16,000 hours
Key Maintenance Indicators	United States Air Forces standard 81 % - Mission Capapble - Percentage of aircraft readily available to do the mission. 15 % - Not Mission Capable for Maintenance - Percentage not mission capable for maintenance reasons. 9 % - Not Mission Capable for Supply - Percentage not mission capable for supply reasons. 6 % - Abort Rate - Rate of aircraft that cannot fly sorties due to ground or air abort. 19 % - Break Rate - Number of Code 3s divided by total number of sorties flown. Different aircraft codes indicate mission capability upon completion of a sortie: Code One is mission capable. Code 2 is an aircraft with a problem but is still mission capable. Code 3 is an aircraft not mission capable until problem is fixed. 75 % - Fix Rate - Percentage of Code 3 aircraft fixed in eight-hour period. 18 % - Cannibilization Rate - Percentage of cannibalizations (parts taken from one aircraft to fix another) divided by number of sorties. 9 % - Repeat/Recur Rate - Percentage of repeats or recurs divided by total of pilot-reported discrepancies. 95 % - Maintenance Scheduling Effectiveness Rate - Percentage of maintenance scheduling actions done on time. 88 % - Flying Scheduling Effectiveness Rate - Ability to fly selected aircraft without deviation

Armament
F-15C Weapon Loads 1 - M-61A1 20mm multibarrel internal gun, 940 rounds of ammunition 4 - AIM-9L/M Sidewinder and 4 - AIM-7F/M Sparrow missiles, or combination of AIM-9L/M, AIM-7-F/M and AIM-120 missiles. AIM AIM AIM AGM 20 7 9 120 88 MM 4 4 900 4 2 2 900 2 2 4 900 4 4 4 900 4 4 4 900 8 900
F-15E Weapon Loads 1 - M-61A1 20mm multibarrel internal gun, 512 rounds of ammunition 4 - AIM-9L/M Sidewinder on the underwing stations and 4 - AIM-7F/M Sparrow missiles conformal fuel tank up to eight AIM-120 AMRAAM missiles 12 CBU-52 (6 with wing tanks) 12 CBU-59 (6 with wing tanks) 12 CBU-71 (6 with wing tanks) 12 CBU-87 (6 with wing tanks) 12 CBU-89 (6 with wing tanks) 20 MK-20 (6 with wing tanks)

Lockheed SR-71 Blackbird

Lockheed SR-71 Blackbird

Stealth and threat avoidance    

Water vapor is condensed by the low-pressure vortices generated by the chines outboard of each engine inlet.

The first operational aircraft designed around a stealthy shape and materials, the SR-71 had several features designed to reduce its radar signature. The SR-71 had a radar cross section (RCS) of around 10 square meters, much greater than the later Lockheed F-117 Nighthawk, which had an RCS equivalent in size to a ball bearing.Drawing on the first studies in radar stealth technology, which indicated that a shape with flattened, tapering sides would reflect most radar energy away from the radar beams' place of origin, engineers added chines and canted the vertical control surfaces inward. Special radar-absorbing materials were incorporated into sawtooth-shaped sections of the aircraft's skin. Cesium-based substances were added to the fuel to somewhat reduce the visibility of the exhaust plumes to radar, although the large and hot exhaust stream produced at speed remained quite apparent. For all this effort, Kelly Johnson later conceded that Soviet radar technology advanced faster than the stealth technology employed against it.

The SR-71 carried electronic countermeasures, but its greatest protection was its high speed and cruising altitude that made it almost invulnerable to the weapons of its day. Merely accelerating would typically be enough to evade a surface-to-air missile, and the plane was faster than the Soviet Union's principal interceptor, the MiG-25. In its service life, no SR-71 was shot down, despite many attempts to do so.

Few weapon systems have ever entered the military arena with such blinding superiority as did the Lockheed SR-71 Blackbird. No weapon system has ever maintained that same degree of superiority over a period of four decades. Today, the Blackbird is still the fastest, highest-flying, most-effective reconnaissance aircraft in history, even though budgetary considerations have caused it to be withdrawn from active service.

Like the U-2, a product of the U.S. government's super-secret Skunk Works research & development center, the Lockheed SR-71 Blackbird is a perfect expression of Kelly Johnson's genius and his leadership of a brilliant team of fewer than 200 engineers.

The USAF's SR-71 was a two-seat development of the earlier A-12 aircraft used by the Central Intelligence Agency. The Lockheed SR-71 Blackbird first flew on December 22, 1964, and by December 1967, all 31 of the Blackbirds had been delivered to the USAF.

The Blackbird was both a miracle of design and of production, for its performance (speed of Mach 3.2, more than 90,000 feet of altitude, a 4,000-mile range) had to overcome not only the sound barrier, but also the heat barrier. Skin temperatures of the craft exceeded 1,050 degrees Fahrenheit. Special fuels, hydraulic fluids, electronics, and glass had to be developed to match the strength of the aircraft's titanium structure.

A Lockheed SR-71 Blackbird, flown invariably by a highly skilled crew, became an invulnerable, invaluable reconnaissance aircraft. Unlike satellites in fixed orbits, the SR-71 could be deployed within hours to anywhere in the world.

The usefulness of the Lockheed SR-71 Blackbird went beyond military applications to diplomatic roles. During the 1973 Middle East Yom Kippur War, reconnaissance photos taken by the SR-71 determined the positions of the advancing Israeli forces, and were used during subsequent peace negotiations. And as a research instrument, the SR-71 has few peers; although officially retired, Blackbirds are rumored to be occasionally flown -- "unofficially" -- in NASA research.

Blackbirds set many records for speed and altitude, the last one a transcontinental speed record of less than 68 minutes -- on the delivery flight of a retired SR-71 to the National Air and Space Museum in Washington, D.C.

LOCKHEED SR-71 BLACKBIRD SPECIFICATIONS

Wingspan: 55 ft. 7 in.

Length: 107 ft. 5 in.

Height: 18 ft. 6 in.

Empty Weight: 60,000 lbs

Gross Weight: 170,000 lbs

Top Speed: Mach 3.2-plus

Service Ceiling: 90,000 ft.-plus

Range: 2,600 miles

Engine/Thrust: Two Pratt & Whitney J58 turbojets/32,500 lbs each

Crew: 2

Equipment: Wide range of classified intelligence-gathering equipment

Alien Spaceship

Alien Spaceship

Looking to build the perfect classic alien spaceship, huh? Well you've come to the right place! My design firm has built thousands of these things, so I'll throw some ideas out and you can tell me what you think:

For the interior, first off, I'm thinking CATWALKS. We should have sterile, metal catwalks spiraling all over the damn place, and every inch of every wall should be covered in tubes. What kind of tubes? Insider Tip: It doesn't matter, they're just there for decoration, but if any of them get pulled out of the wall, they'll start shooting out dry-ice smoke for some reason. Sure, these smoke-shooting purposeless tubes will run you a few extra Rembulaxx (our form of money, as you already know), but it's the direction everyone's going in, and it'll definitely up the resale value.

For lighting, I'm thinking we go nice and traditional. Three words: Light Blue EVERYTHING. It'll mostly be pitch black, but then bathed in a really futuristic-seeming light blue, because MAN, do we love that color. Also we can coordinate the interior light-blue with the light-blue tractor beam, force field, and the lasers that we shoot. Also it's literally the only color of bulb available at Spaceship Depotblorff, so it's stylish and practical.

For the Medical Room, I'm thinking we paint everything SUPER white. Like, creepy-ass white, with an impossibly spotless glowing tile floor and one really ominous slab-shaped table in the very center. Then we surround the table with weird automated arms coming out of the ceiling with drills and stuff jutting out of them, which is partly aesthetic, but also useful for doing weird, scary operations. It's sleek, it's elegant, and Hyper-Scareminism is very in right now.

A couple other random design thoughts:

- The core should be a big pulsating aqua-colored thing that makes a low bass hum at all times and can easily be set to self-destruct. (It's not technically a Ranch unless you can bump a button and have it self destruct.)

- There should be one room with a bunch of glass pods containing a weird liquid and gross embryos. Can double-function as a breakfast nook.

- All the doors are slidey and automatic and make whooshing noises. Also they get dangerously sealed off anytime anything happens.

- The temperature is constantly super-hot or super-cold. Just something not normal, because we are aliens.

- Granite countertops and stainless steel appliances. Like, uhhhDUHHHH.

And finally, here's the kicker: the entire ship will be CIRCULAR. And the whole thing SPINS when it flies. And it emits a shrill, kinda Theremin-sounding "eeehooooeeehoooooeeehooo" noise whenever it's in the air, so it sounds like a loud, broken ray gun, but constantly.

What's that? You'll "be in touch?" Ok! Do you want to take my card? It's a clear blue microchip that plugs into a holo-puter that's different looking than computers now but will look crappy and dated in eleven years. No, you'll just call me? Oh, alright.

Well, I will talk to you soon then! And let me know ASAP so I can get started on pricing that purple embryo-preserving juice!

RC Rockets

A model rocket, also known as low power rocket, is a smallrocket designed to reach low altitudes (usually to around 100–500 m (300–1500 ft) for a 30 g (1 oz.) model) and recovered by a variety of means.

According to the United States National Association of Rocketry(NAR) Safety Code, model rockets are constructed of paper, wood, plastic and other lightweight materials. The code also provides guidelines for motor use, launch site selection, launch methods, launcher placement, recovery system design and deployment and more. Since the early 1960s, a copy of the Model Rocket Safety Code has been provided with most model rocket kits and motors. Despite its inherent association with extremely flammable substances and objects with a pointed tip traveling at high speeds, model rocketry historically has proven to be a very safe hobby and has been credited as a significant source of inspiration for children who eventually become scientists andengineers.

Model rocket motors

Anatomy of a basic model rocket engine. A typical engine is about 8cm long. 1. Nozzle; 2. Case; 3. Propellant; 4. Delay charge; 5. Ejection charge; 6. End cap

Most small model rocket motors are single-use engines, with cardboard bodies and lightweight molded clay nozzles, ranging inimpulse class from fractional A to G. Model rockets generally use commercially manufactured black-powder motors. These motors are tested and certified by the National Association of Rocketry, the Tripoli Rocketry Association (TRA) or the Canadian Association of Rocketry(CAR). Black-powder motors come in impulse ranges from 1/8A to E, although a few F black-powder motors have been made.

The physically largest black-powder model rocket motors are typically E-class, for black powder is very brittle. If a large black-powder motor is dropped, or is exposed to many heating/cooling cycles (for example, in a closed vehicle exposed to high heat), the propellant charge may develop hairline fractures. These fractures increase the surface area of the propellant, so that when the motor is ignited, the propellant burns much more quickly than it should, producing greater than normal internal chamber pressure inside the engine. This pressure may exceed the strength of the paper case, causing the motor to burst. A bursting motor can cause damage to the model rocket ranging from a simple ruptured motor tube or body tube to the violent ejection (and occasionally ignition) of the recovery system.

Rocket motors with power ratings higher than D to E, therefore, customarily use composite propellants made of ammonium perchlorate, potassium nitrate, aluminium powder, and a rubbery bindersubstance contained in a hard plastic case. This type of propellant is similar to that used in the solid rocket boosters of the space shuttle and is not as fragile as black powder, increasing motor reliability and resistance to fractures in the propellant. These motors range in impulse from size D to O. Composite motors produce more impulse per unit weight (specific impulse) than do black-powder motors.

The components of a motor made by Aerotech Consumer Aerospace for a 29/40-120 casing. 1. Motor Casing 2. Aft Closure 3. Forward Closure 4. Propellant Liner 5. Propellant Grains (C-Slot Geometry) 6. Delay Insulator 7. Delay Grain and Delay Spacer 8. Black Powder Ejection Charge 9. Delay O-Ring 10 & 11. Forward and Aft O-Rings 12. Forward Insulator 13. Nozzle 14. Electric Igniter

Reloadable composite-propellant motors are also available. These are commercially produced motors requiring the user to assemble propellant grains, o-ringsand washers (to contain the expanding gases), delay grains and ejection charges into special non-shattering aluminum motor casings with screw-on or snap-in ends (closures). The advantage of a reloadable motor is the cost: firstly, because the main casing is reusable, reloads cost significantly less than single-use motors of the same impulse. Secondly, assembly of larger composite engines is labor-intensive and difficult to automate; off-loading this task on the consumer results in a cost savings. Reloadable motors are available from D through O class.

Motors are electrically ignited with an electric matchconsisting of a short length of pyrogen-coated nichrome,copper, or aluminum bridgewire pushed into the nozzle and held in place with flameproof wadding, a rubber band, a plastic plug or masking tape. On top of the propellant is a tracking delay charge, which produces smoke but in essence no thrust, as the rocket slows down and arcs over. When the delay charge has burned through, it ignites an ejection charge, which is used to deploy the recovery system.

Performance

The impulse (area under the thrust-time curve) of a model motor is used to determine its class. Motors are divided into classes from 1/4A to O and beyond. Black powder rocket motors are only commonly produced up to Class E. Each classes upper limit is double the upper limit of the previous classes. Low power rockets only use motors that are G and below. Rockets using motors with a greater impulse are considered high power rockets.

Class	Total Impulse (Metric Standard)
1/4A	0.313-0.625 N·s
1/2A	0.626-1.25 N·s
A	1.26-2.50 N·s
B	2.51-5.0 N·s
C	5.01-10 N·s
D	10.01-20 N·s
E	20.01-40 N·s
F	40.01-80 N·s
G	80.01-160 N·s

Figures from tests of Estes rocket motors are used in the following examples of rocket motor performance.

For miniature black powder rocket motors (13 mm diameter), the maximum thrust is between 5 and 12 N, the total impulse is between .5 and 2.2 Ns, and the burn time is between .25 and 1 second. For Estes ‘regular size’ rocket motors (18 mm diameter), there are three classes: A, B, and C. The A class 18 mm motors have a maximum thrust between 9.5 and 9.75 N, a total impulse between 2.1 and 2.3 Ns, and a burn time between .5 and .75 seconds. The B class 18 mm motors have a maximum thrust between 12.15 and 12.75 N, a total impulse between 4.2 and 4.35 Ns, and a burn time between .85 and 1 second. The C class 18mm motors have a maximum thrust from 14 – 14.15 N, a total impulse between 8.8 and 9 Ns, and a burn time between 1.85 and 2 seconds.

There are also 3 classes included in Estes large (24 mm diameter) rocket motors: C, D, and E. The C class 24 mm motors have a maximum thrust between 21.6 and 21.75 N, a total impulse of between 8.8 and 9 Ns, and a burn time between .8 and .85 seconds. The D class 24 mm motors have a maximum thrust between 29.7 and 29.8 N, a total impulse between 16.7 and 16.85 Ns, and a burn time between 1.6 and 1.7 seconds. The E class 24 mm motors have a maximum thrust between 19.4 and 19.5 N, a total impulse between 28.45 and 28.6 Ns, and a burn time between 3 and 3.1 seconds.

Several independent sources have published measurements showing that Estes model rocket engines often fail to meet their published thrust specifications.

Motor nomenclature

Rocket motors. From left, 13mm A10-0T, 18mm C6-7, 24mm D12-5, 24mm E9-4, 29mm G40-10.

Model rocket motors produced by companies like Estes Industries andQuest Aerospace are stamped with a code (such as A10-3T or B6-4) that indicates several things about the motor.

The Quest Micro Maxx engines are the smallest at a diameter of 6mm. The company Apogee Components made 10.5mm micro motors, but those were discontinued in 2001. Estes manufactures size "T" (Tiny) motors that are 13 mm in diameter by 45 mm long, while standard A, B and C motors are 18 mm in diameter by 70 mm long. Larger C, D, and E class black-powder motors are also available; they are 24 mm in diameter and either 70 (C and D motors) or 95 mm long (E motors). Some motors, such as F and G single-use motors, are 29mm in diameter. High-power motors (usually reloadable) are available in 38mm, 54mm, 75mm, and 98mm diameters.

First letter

The letter at the beginning of the code indicates the motor's total impulse range (commonly measured in newton-seconds). Each letter in successive alphabetical order has up to twice the impulse of the letter preceding it. This does not mean that a given "C" motor has twice the total impulse of a given "B" motor, only that C motors are in the 5.01-10.0 N-s range while "B" motors are in the 2.51-5.0 N-s range. The designations "¼A" and "½A" are also used. For a more complete discussion of the letter codes, see Model rocket motor classification.

For instance, a B6-4 motor from Estes-Cox Corporation has a total impulse rating of 5.0 N-s. A C6-3 motor from Quest Aerospace has a total impulse of 8.5 N-s.

First number

The number that comes after the letter indicates the motor's average thrust, measured in newtons. A higher thrust will result in higher liftoff acceleration, and can be used to launch a heavier model. Within the same letter class, a higher average thrust also implies a shorter burn time (e.g., a B6 motor will not burn as long as - but will have more initial thrust than - a B4). Motors within the same letter class that have different first numbers are usually for rockets with different weights. For example, a heavier rocket would require an engine with more initial thrust to get it off of the launch pad, whereas a lighter rocket would need less initial thrust and would sustain a longer burn, reaching higher altitudes.

Last number

The last number is the delay in seconds between the end of the thrust phase and ignition of the ejection charge. Black Powder Motors that end in a zero have no delay or ejection charge. Such motors are typically used as first-stage motors in multistage rockets as the lack of delay element and cap permit burning material to burst forward and ignite an upper-stage motor.

A "P" indicates that the motor is "plugged". In this case, there is no ejection charge, but a cap is in place. A plugged motor is used in rockets that do not need to deploy a standard recovery system such as small rockets that tumble or R/C glider rockets. Plugged motors are also used in larger rockets, where electronic altimeters or timers are used to trigger the deployment of the recovery system.

Composite motors usually have a letter or combination of letters after the delay length, indicating which of the manufacturer's different propellant formulations is used in that particular motor.

Reloadable motors

Aerotech Reloadable motor cases. From left: 24/40, 29/40-120, 29/60, 29/100, 29/180, 29/240

Reloadable rocket motors are specified in the same manner as single-use model rocket motors as described above. However, they have an additional designation that specifies both the diameter and maximum total impulse of the motor casing in the form of diameter/impulse. After that, there is a series of letters indicating the propellant type. However, not all companies that produce reloadable motor systems use the same designations for their motors.

An Aerotech consumer aerospace reload designed for a 29-millimeter-diameter case with a maximum total impulse of 60 newton-seconds carries the designation 29/60 in addition to its impulse specification.

However, Cesaroni Technology Incorporated (CTI) motors use a different designation. They first have "Pro" followed by a number representing the diameter of the motor in milimeters, for example, a Pro38 motor is a 38mm diameter motor. After this, there is a new string of characters such that the impulse in newton-seconds is first, followed by the motor classification, the average thrust in newtons, followed by a dash, and the delay time in seconds. For example, a Pro29 110G250-14 is a G-motor with 110 Ns of impulse, 250 N of thrust, and a 14 second delay.

Model rocket recovery methods

Model and high-power rockets are designed to be safely recovered and flown repeatedly. The most common recovery methods are parachute and streamer. The parachute is usually blown out by the engine's ejection charge, which pops off the nose cone. The parachute is attached to the nose cone, making it pull the parachute out and make a soft landing.

Featherweight recovery

The simplest approach, which is appropriate only for the tiniest of rockets, is to let the rocket flutter back to earth after ejecting the motor. This is slightly different from tumble recovery, which relies on some system to destabilize the rocket to prevent it from entering a ballistic trajectory on its way back to earth.

Tumble recovery

Another simple approach appropriate for small rockets — or rockets with a large cross-sectional area — is to have the rocket tumble back to earth. Any rocket that will enter a stable, ballistic trajectory as it falls is not safe to use with tumble recovery. To prevent this, some such rockets use the ejection charge to slide the engine to the rear of the rocket, moving the center of mass behind the center of pressure and thus making the rocket unstable.

Nose-blow recovery

Another very simple recovery technique, used in very early models in the 1950s and occasionally in modern examples, is nose-blow recovery. This is where the ejection charge of the motor ejects the nose cone of the rocket (usually attached by a shock cord made of rubber, Kevlar string or another type of cord) from the body tube, destroying the rocket's aerodynamic profile, causing highly increased drag, and reducing the rocket's airspeed to a safe rate for landing. Nose-blow recovery is generally only suitable for very light rockets.

Parachute/Streamer

A typical problem with parachute recovery.

The parachute/streamer approach is used most often in small model rockets, but can be used with larger rocket models given the size of theparachute greatly increases with the size of the rocket. It uses the ejective force of the motor to deploy, or push out, the parachute or streamer. The parachute is attached to the body either directly, by means of a ripcord, or indirectly, when it is attached to the nose cone, which is in turn attached to the body by a ripcord. Typically, a ball or mass of fireproof paper or material is inserted into the body before the parachute or streamer. This allows the ejection charge to propel the fire-proof material, parachute, and nose cone without damaging the recovery equipment. Air resistance slows the rocket's fall, ending in a smooth, controlled and gentle landing.

Glide recovery

In glide recovery, the ejection charge either deploys an airfoil (wing) or separates a glider from the motor. If properly trimmed, the rocket/glider will enter a spiral glide and return safely. In some cases, radio-controlled rocket gliders are flown back to the earth by a pilot in much the way as R/C model airplanes are flown.

Some rockets (typically long thin rockets) are the proper proportions to safely glide to Earth tail-first. These are termed 'backsliders'.

Helicopter recovery

The ejection charge, through one of several methods, deploys helicopter-style blades and the rocket autorotatesback to earth. The helicopter recovery usually happens when the engine's recoil creates pressure, making the nose cone pop out. There are rubber bands connected to the nosecone and three or more blades. The rubber bands pull the blades out and they provide enough drag to soften the landing. In some rockets, the fins are used as the blades as well. In these, the ejection charge pushes a tube inside that has tabs sticking out of the rocket that hold the fins during launch. Then the tab releases the rubber band-pulled fins than pivot up into helicopter position.

Instrumentation

Aerial photography

Cameras and video cameras can be launched on model rockets to take photographs in-flight. Model rockets equipped with the Astrocam, Snapshot film camera or the Oracle or newer Astrovision digital cameras (all produced by Estes), or with homebuilt equivalents, can be used to take aerial photographs.

These aerial photographs can be taken in many ways. Mechanized timers can be used or passive methods may be employed, such as strings that are pulled by flaps that respond to wind resistance. Microprocessor controllers can also be used. However, the rocket's speed and motion can lead to blurry photographs, and quickly changing lighting conditions as the rocket points from ground to sky can have an impact on video quality. Video frames can also be stitched together to create panoramas. As parachute systems can be prone to failure or malfunction, model rocket cameras need to be protected from impact with the ground.

There are also rockets that record short digital videos. There are two widely used ones used on the market, both produced by Estes: the Astrovision and the Oracle. The Astrocam shoots 4 (advertised as 16, and shown when playing the video, but in real life 4) seconds of video, and can also take three consecutive digital still images in flight, with a higher resolution than the video. It takes from size B-6-3 to C-6-3 Engines. The Oracle is a more costly alternative, but is able to capture all or most of its flight and recovery. In general, it is used with "D" motors. The Oracle has been on the market longer than the Astrovision, and has a better general reputation. However, "keychain cameras" are also widely available and can be used on almost any rocket without significantly increasing drag.

There are also experimental homemade rockets that include onboard videocameras, with two methods for shooting the video. One is to radio the signal down to earth, like in the BoosterVision series of cameras. The second method for this is to record it on board and be downloaded after recovery, the method employed by the cameras above (some experimenters use the Aiptek PenCam Mega for this, the lowest power usable with this method is a C or D Motor).

Instrumentation and experimentation

Model rockets with electronic altimeters can report and or record electronic data such as maximum speed, acceleration, and altitude. Two methods of determining these quantities are to a) have an accelerometer and a timer and work backwards from the acceleration to the speed and then to the height and b) to have a barometer on board with a timer and to get the height (from the difference of the pressure on the ground to the pressure in the air) and to work forwards with the time of the measurements to the speed and acceleration.

Rocket modelers often experiment with rocket sizes, shapes, payloads, multistage rockets, and recovery methods. Some rocketeers build scale models of larger rockets, space launchers, or missiles.

High-power rocketry

As with low-power model rockets, high-power rockets are also constructed from lightweight materials. Unlike model rockets, high-power rockets often require stronger materials such as fiberglass, composite materials, and aluminum to withstand the higher stresses during flights that often exceed speeds of Mach 1 (340 m/s) and over 3,000 m (10,000 ft.) altitude.

High-power rockets are propelled by larger motors ranging from class H to class O, and/or weigh more than 1,500grams at liftoff. Their motors are almost always reloadable rather than single-use in order to reduce cost. Recovery and/or multi-stage ignition may be initiated by small on-board computers, which use an altimeter or accelerometer for detecting when to ignite engines or deploy parachutes.

High-power model rockets can carry large payloads, including cameras and instrumentation such as GPS units.

Differences from model rocketry

A high power rocket must meet at least one of the following criteria:

• The rocket weighs more than 1,500 grams
• The motor used contains more than 125 grams of propellant
• The motor used has an impulse of more than 320 Newton-seconds