Here is something a bit different - a quick review of the Solar Impulse project (http://www.solarimpulse.com/): a plan to build a single seat solar powered plane, which will take off autonomously and be capable of remaining airborne for several days. The plan is to use this as a springboard to develop a two seat version to circumnavigate the globe.
Solar Impulse
This is a particularly interesting project for many reasons, not least of all because air travel is a major concern for many environmental reasons, whilst it is regarded as contributing not all that much CO2 compared to other sources (power generation and sea freight) it does release emissions directly into the upper atmosphere, where it can have a damaging effect, thus to raise the profile of sustainable technology in this way is admirable, and not all that dissimilar to our aims with our solar powered car entry into the Global Green Challenge (http://www.globalgreenchallenge.com.au/).Furthermore, to an aerospace engineer such as me, this project has very many exciting challenges. For instance, the wingspan is quoted at around 61 metres in length, that is about the same as an Airbus A340! This is done for a very good reason, high aspect ratio wings (wingspan >> chord length) have a lower induced drag term, and so require much less power; this is why gliders have such long narrow wings (it is seen less on powered aircraft since the wings are used to store fuel and take much greater loads).The project seems to be advancing well, with the website stating that load testing on the main wing spars has been completed, this is very important, since with wings of this length the self weight of the wings will generate a significant moment, and once the wings are loaded there is the possibility of large tip deflections, leading to potential fatigue problems.The large wing area will provide the space for the solar array, although the plane will only be travelling at around 70 mph - not a lot faster than our car - so it will require considerably more energy (around 30kW compared to our 1kW). Batteries will also be a key part, as they will need to store enough energy for overnight, and will need to be as light as possible (the all up weight of the aircraft is meant to be below 1,500 kg), but I’ll leave discussion of solar cells and batteries for somebody better qualified than myself.It is also interesting to look at previous solar powered planes. NASA have built a variety of unmanned solar and fuel celled vehicles (check out the NASA Pathfinder Aircraft), as early as the mid 1980′s.NASA Pathfinder Plus
Once I’ve read more on this subject I hope to bring you some more details, for now I hope this has further whetted your appetite for the development of solar powered transport.
- Mike
