Posts Tagged‘aeroplane’

The Human Powered Helicopter.

We humans aren’t great power sources, despite what The Matrix might have you believe, with our sustained output being roughly equivalent to about one quarter of a horsepower (maybe half if you’re an endurance runner or cyclist). This works pretty well for our natural form of locomotion as we don’t need that much to move ourselves around but it becomes something of an issue when we start using more exotic forms of transportation. Cycling and rowing can be fairly efficient forms of transportation when all you have is human power however once you want to take to the skies things start to get a little hairy as the power required for sustained flight is usually well above what your typical human can provide.

That’s not to say we haven’t tried, far from it. Attempts to create a purely human powered craft go as far back as 1923, a mere 20 years after the first powered, heavier than air flight took place at Kitty Hawk. Most of these experiments could only be considered experimental in nature as the distances they could cover were rarely more than a few meters and most of them required a powered assist in order to take off, thereby invalidating them as being truly human powered. The late 1970s however saw the creation of the Gossamer Condor and Albatross, both fully human powered craft that took the Kremer Prize. However probably the most famous of all the human powered craft comes in the form of the MIT’s Daedalus a human powered craft that flew from the Isle of Crete to Santorini, a distance of 115KMs that was completed in just under 4 hours.

You’d then think that a human powered helicopter wouldn’t be too far behind however the design principles behind a helicopter present a much larger challenge than those of a traditional aeroplane. Instead of pushing the aerofoil via the use of a propeller to generate lift a helicopter instead whips the aerofoil itself through the air. This, traditionally, requires a lot more effort in order to generate the same amount of lift and the tricks used for the current generation of human powered craft (light materials and giant wings) present even greater challenges when those wings need to be under rotational stress. We do have several decades of aeronautical engineering advances since then however and one team has finally managed to create a human powered helicopter, one that can fly for just over a minute:

It’s an incredible device sporting 4 rotors that each have a diameter of 20m, each of which is larger than the individual rotors of the mighty Boeing Chinook. That incredible size is also coupled with a weight that seems almost impossible for a craft of that size, weighing in at a paltry 55kg. One thing to note however is that whilst this does count as a human powered helicopter the height it attained, some 3 meters or so, means that this craft was still operating well within the ground effect which means that it’s effectively working with a much better lift profile than would be expected once it reached a higher altitude. Some would then not classify this as a helicopter and instead call it a ground effect craft, which I’d agree with in some sense, but it’s still a pretty amazing feat of engineering despite the fact that it hasn’t left ground effect yet.

It’s really quite amazing to see how a combination of engineering and human power can create things like this which were the stuff of fantasy not too long ago. Sure it might not have any practical uses right now but the technology they developed will definitely flow down to other lightweight craft, further improving their flight capabilities and characteristics. We might never all have our own pedal powered aircraft but it still remains a valuable engineering challenge, much like the solar car races held here in Australia. I can’t wait to see what they develop next as there’s already been implementations of other exotic aircraft like the human powered ornithopter so others can’t be that far behind.

Made In The USA: Flying Saucers.

Even though I don’t get suckered into conspiracy theories since I’m usually only a couple Google searches away from finding the facts I do find the dissection of them quite interesting. One of my favourites are Unidentified Flying Objects as for the most part they’re easily explained by natural phenomena or people mistaking things like illumination flares used in night training for various jet craft. What always fascinated me though was the idea of flying saucers as once I understood the idea of an aerofoil I was always fascinated by how one would actually work and if would even be feasible.

As it so happens it is and the USA put a lot of effort into developing one:

The aircraft, which had the code name Project 1794, was developed by the USAF and Avro Canada in the 1950s. One declassified memo, which seems to be the conclusion of initial research and prototyping, says that Project 1794 is a flying saucer capable of “between Mach 3 and Mach 4,” (2,300-3,000 mph) a service ceiling of over 100,000 feet (30,500m), and a range of around 1,000 nautical miles (1,150mi, 1850km).

As far as we can tell, the supersonic flying saucer would propel itself by rotating an outer disk at very high speed, taking advantage of the Coandă effect. Maneuvering would be accomplished by using small shutters on the edge of the disc (similar to ailerons on a winged aircraft). Power would be provided by jet turbines. According to the cutaway diagrams, the entire thing would even be capable of vertical takeoff and landing (VTOL).

The Coandă Effect is an interesting phenomenon and its likely that you’ve encountered it before. In essence the effect is the tendency of a fluid jet, which is anything with a nozzle that has a medium shooting out of it, to be attracted to surfaces that it passes by. If you’ve ever been to Questacon or similar places you’ve probably seen the ball that hovers in mid air which seems counter-intuitive because the air is blowing out at an angle. This same effect is what can be used to make a flying saucer fly and according to the declassified documents the performance of such a craft would have been fairly impressive for the time.

To put those numbers in perspective one of the most iconic craft, the SR-71 Blackbird, was introduced nearly a decade after this project apparently begun and whilst it might have a range that’s 3 times greater than this theoretical craft the rest of the specifications are either on par or lower than it. Just the service ceiling on it alone would make it a highly valuable strategic craft but the ability to move at up to Mach 4 speeds would have made it immune to nearly all forms of anti-aircraft weaponry available at the time. Whether or not one of these craft was actually built is a question that has not yet been answered but considering that all the documents haven’t been released yet its possible we’ll know more as time goes on.

What I find really fascinating though is whilst the Coandă effect can be used for such exotic craft like the one pictured above it also has many uses in traditional aircraft, helicopters and even in air conditioning. Many large short take-off and landing aircraft make use of the effect to provide a smooth ride at low flying speeds. NOTAR style helicopters use the effect in place of a tail rotor to provide the counter rotational force required to stop them from spinning on the spot. When I started writing this I thought it was some kind of esoteric effect that didn’t have many practical uses but as it turns out it’s pretty much a very well understood and useful phenomenon.

Whilst I know this won’t stop the UFO enthusiasts from saying that the really truly saw one for me the simple fact that the USA was working on such a craft is enough to chalk up any sightings of it to a possible prototype of a craft like this, It might not have gotten past the planning stage but since there are other known craft like this out there (like the VZ-9 Avrocar mentioned in the article I linked earlier) you really have to be a special kind of crazy to keep on thinking that we’re being visited by extraterrestrials travelling in Coandă effect planes.