Reasons of Agni Failure

After the failed first test of Agni-III, about nine months earlier, there had been a test flight of Agni-III, the first ever. However, the maiden flight encountered problems a minute after lift off and was not entirely successful in meeting the mission objectives. From whatever data was available, we were able to determine the reason for failure. It turns out from the CFD simulation that I have carried out during thepost flight analysis that during the initial ascent phase of themissile, the external freestream air interacts with the hot rocket exhaust of the first stage rocket motor and creates a pocket of recirculating hot gases just behind the vehicle. Agni-III uses a flexible nozzle for thrust vector control. In order to allow the nozzle to deflect, an annular gap was left between the nozzle and the

cylindrical shell of the missile instead of closing it entirely.

Basics of Rocket and missiles

n order for a satellite to go into orbit it must accomplish two major tasks. First, the satellite must rise above the atmosphere which surrounds the Earth's surface. The atmosphere contains enough particles which slow the spacecraft preventing it from orbiting the planet. A propulsion device must strain against gravity to rise above the atmosphere. Second, the satellite must also be provided with enough horizontal velocity above the atmosphere to at least equal the local circular speed upon orbital injection otherwise it will reenter the atmosphere and burn due to friction. Both of these jobs are done by rockets.

A simple rocket is usually a tall cylinder containing propellant. Propellant always contains two items: fuel and oxidizer. Fuel is the item which b urns to provide rocket thrust. In a simple liquid rocket it is stored in its own separate fuel supply tank. To support fuel combustion the rocket also contains a source of oxygen needed after the spacecraft passes above the atmosphere and cannot collect oxygen in any form. This oxygen is in the form of an oxidizer to aid in combustion; it is stored in a container which resembles the fuel supply tank.

Missile Grid Fins

Grid fins, sometimes also called lattice fins, are a relatively recent development in guided missile technology. Most guided weapons use planar control fins that are mounted parallel to the body axis. These fins rotate back and forth to generate forces in the horizontal and/or vertical planes that cause the vehicle to yaw right and left, pitch up and down, or roll as the missile maneuvers towards a target. These moving control fins are located forward of the weapon's center of gravity (CG) in a canard control layout, at the CG in a wing control format, or aft of the CG in a tail control design.

Control fin options for guided weapons

Missile Guidance part1

Many questioners often seem "concerned" about how missiles are able to seek out and accurately navigate their way to the correct target without assistance from a human operator. However, there is no need for alarm because a weapon very rarely makes a mistake unless it is misprogrammed by the human who launches it in the first place. In fact, many of the methods used for missile guidance are the same as those used to navigate manned planes like the commercial airliners you and I fly aboard.

The first topic we need to address is establishing some basic definitions. Missiles can be categorized in many different ways, such as by their mission or lauch platform. The two conventions we will follow in this article concern the missile's type of guidance and type of sensor or seeker. These two concepts are often used interchangeably, but it is important to understand their differences.

Missile Control Systems, part1

You are correct in pointing out that most missiles do not have conventional rudders, ailerons, or elevators like those used on typical airplanes. Nonetheless, missiles do employ similar aerodynamic control surfaces in order to maneuver the vehicle during flight. To begin our discussion, we need to introduce some terminology used to describe the major components of a missile.

The heart of a missile is the body, equivalent to the fuselage of an aircraft. The missile body contains the guidance and control system, warhead, and propulsion system. Some missiles may consist of only the body alone, but most have additional surfaces to generate lift and provide maneuverability. Depending on what source you look at, these surfaces can go by many names. In particular, many use the generic term "fin" to refer to any aerodynamic surface on a missile. Missile designers, however, are more precise in their naming methodology and generally consider these surfaces to fall into three major categories: canards, wings, and tail fins.

Ballistic missile

A ballistic missile works by burning propellant and ejecting the hot gases through a nozzle, typically at a velocity of around 2500 meters per second (m/sec). The thrust from the exhaust causes the missile to accelerate. A given thrust will cause progressively higher accelerations as the missile lightens due to the consumption of its propellant. All of the propellant is consumed in the first few minutes of flight, following which the missile coasts above the atmosphere at a speed of several kilometers per second to its target. In an idealized case, the burnout velocity would be equal to the exhaust velocity times the natural logarithm of the ratio of gross missile weight to the payload. In real life, the missile will need additional impulse to reach a given velocity. Account must be taken of: the structural weight of the missile (typically discarded in several stages during boost phase); air resistance during boost; and gravity during boost. Still, the idealized relationship is useful: it provides an optimistic upper bound on what can be achieved when parameters are varied. At short ranges, the range of the missile will go as the square of its burnout velocity. Due to the curvature of the earth, at longer ranges the range will increase more rapidly. Table 2 shows the burnout velocity needed to reach various ranges, together with the payload fractions associated with missiles that attain any given velocity.

Smallest aircraft in the World

We addressed the largest plane in the world in a previous article. The subject of the smallest plane is a bit more complex since one must ask what class of aircraft to consider. For example, the remote controlled planes that you and I can buy in a store are obviously smaller than anything a human could fly aboard. A paper airplane flown by a child is even smaller than that, and many researchers are currently working on Micro Air Vehicles (MAVs) that rival insects in size.
However, we will assume that this question is asking about the smallest manned plane in the world, or the smallest plane flown with a human pilot aboard. Even this category can be confusing since it could possibly include vehicles like hang gliders or ultralights, but we will limit our discussion to more conventional airplane types. This definition leaves us with three primary sets of aircraft designers who have competed against each other to build and fly the "world's smallest plane" since the end of World War II.

Largest Helicopters in the World

The article you mention discusses several of the largest planes in the world. It also describes how aircraft are typically ranked by weight rather than by physical dimensions like length or wingspan. The same holds true for helicopters. Although the diameter of the rotor is often a useful measure of a helicopter's size, these vehicles are most often ranked by maximum takeoff weight. As was also true of the largest planes, the ranks of largest helicopters are largely dominated by craft originally built in the Soviet Union. Perhaps that should be no surprise given the vast size of that nation and the need to transport large cargoes to distant and remote locations.

Largest Aircraft In the World

Aircraft records can indeed be confusing. If you need any reminder of that observation, try looking through the records on the FAI website. FAI, short for Fédération Aéronautique Internationale, is the international body that officially recognizes aviation and space records. However, most of the information on that site concerns aircraft performance, such as speed and altitude, rather than size.
Your question really comes down to how you decide to compare one plane to another. One of the measurements you mention is wingspan. While this dimension is often used to compare overall size, it is generally not the most accepted measure. Aircraft are usually ranked by weight, the maximum takeoff weight in particular. By this measure, the world's largest plane is the Antonov An-225 built in Ukraine when it was part of the Soviet Union.


An-225, largest plane in the world