It just so happens that many things that seemed ineffective in the past, turn out to be most appropriate today. NASA has revisited one of its old projects - to use a helicopter-like propeller for descent vehicles of manned spacecraft instead of the traditional parachute.
There is nothing more impressive than the launch of a modern space rocket. The landing looks absolutely ineffective: there is just a small capsule hanging on parachutes.
The parachute system, even the most efficient and reliable one, is the same as a balloon: it flies wherever the wind blows. There were incidents in the past when landing space vehicles would be swerved into the mountains or taiga. The problem of controlled descent from space still remains and will continue to be a serious problem for the designers of landing vehicles.
During the 1960s, NASA developed a project to use helicopter-like rotors for landing capsules. The rotor was supposed to be used instead of the parachute. The rotor would work on the base of the autogyro principle. The advantages of this technology are obvious: the air flow will rotate the rotor decreasing the speed of the capsule and create the climb power, which will allow to control the flight trajectory of the capsule.
There is also a downside, though. A parachute is much easier and cheaper. However, in spite of severe financial constraints, when the funding of NASA has dropped to historic lows, the agency is revisiting the old idea. During the 1960s, picking up a landing capsule anywhere in the world ocean seemed to be an easy option. The landing based on autorotation seemed too complex, and therefore expensive.
Spanish engineer Juan de la Cierva was nearly killed in a plane crash and decided to create a device that would be able to descend safely in case of engine failure. The scientist created the aircraft in 1919.
On January 9, 1923 his first gyro made its first flight. Afterwards, people began to build them around the world and. Gyros, in some respects, are superior to airplanes and helicopters in terms of flight safety. A loss of speed is lethal for an airplane, as it falls into a spin. A gyroplane begins to descend gradually.
In case of engine failure, a gyro begins to glide using the effect of autorotation. The pilot can control the direction of descent, and the gyro does not need a runway, which is also very important to ensure flight safety.
The gyro is much less expensive than many light aircraft and helicopters. It turns out that this is one of the safest aircraft that man has ever created.
Modern materials can produce durable folding rotors. More importantly, one will not have to drop the capsule into the ocean. It will be possible to set the landing site in advance and thus minimize the costs for retrieval and transportation. Technically, it is possible to integrate brake motors in the descent capsule to avoid those problems. This technology is already in use at Soyuz TM.
However, this option is harder and more expensive than rotors. It does not guarantee the proper control of the capsule during the flight.
The autorotation descent system was tested in the model dropped from the height of 165 meters in the "vertical assembly building" of American spacecraft. The scientists tested various angles of rotors to provide the maximum lift.
Should the developers succeed, the future of this system can be very promising. In the future, scientists can develop a fundamentally new landing vehicle that will be able to land on the roof of a building.
However, American engineers may come across a fundamental difficulty. The rotors will be released from the capsule after aerobraking. They will have to rotate at a very high speed - much faster than that of gyroplanes and helicopters. That is, the modes of rotors, as well as the probability for the air flow to come off the rotors, will be different than those we know today.
If the rotors are too short, then the speed of descent will be too high. If rotors are as long as those of a helicopter, designers will have to think of the way how to place them on board a capsule.
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