Electric Altitude; And Then We'll Take It Higher!
The Airbus Zephyr has now cemented its place as a technological breakthrough, having just completed its second 18-day long stratospheric flight powered solely by solar power and two small propellers. Cruising at an altitude of over 75,000 feet, weighing less than 75kg and with a wingspan of 82 feet, the Zephyr is something of a marvel to behold. I suppose the questions many of you will be asking now are how have they managed it and why has it been made in the first place? What possible need is there for such an aircraft?
To be able to unpack all of these questions and even being to answer them, we must consider what technology we currently have and what their limitations are. Firstly, traditional aircraft (say, a commercial airliner) would ordinarily have a much reduced altitude limit, hence why when you go on holiday and can read the altitude on your seatback screens it will say anything in the 30-40,000 ft range (with many factors determining the precise altitude). There are some exceptions to this rule, such as Concorde with a 60,000 ft 'ceiling'/limit (this being the highest commercial airliner altitude), a smattering of business jets, and by the end of the decade we are told that the Boom Overture will take this crown, being able to fly even faster and higher than Concorde ever could. Now we enter into rocket-powered military craft with the next few, such as the MiG-31 at 82,000 ft, the Lockheed SR-71 at around 90,000 ft and so the list grows all the way up to the truly magnificant North American X-15 which had an operational ceiling of a truly mind-boggling 354,330 ft! Now, there are a few things which all of these aircraft have in common which go some way to explaining the need for the Zephyr. Firstly, they are all hugely expensive, not only to buy but also to run and maintain (not to mention just how expensive the development programmes for these aircraft were). Secondly, all of these aicraft fly too fast. The basic concept of flight denotes that your lift (that being the air making you 'buoyant' in the sky) must be greater than the effects of drag and gravity, otherwise you're not flying for very long! Why this is a problem for the previously mentioned aircraft is that the speed at which they 'stall' (meaning they aren't able to maintain lift, so start to head rather quickly back to the ground) is far too fast for the Zephyr's purpose. Thirdly, and this is kind of away from the main purpose of the Zephyr but is still an important distinction given the ever increasing importance of tackling climate change, aircraft up to this point have been awfully bad for the environment. For example, just a simple flight from City Airport in London to Dublin in a BAe 146/Avro RJ will produce more than 16 tonnes of CO2 emissions. Granted, the BAe 146 is a rather old aircraft, but the point is still valid as we tend to fly much further for our holidays, so being in more efficient aircraft negates the difference. So, having established that other aircraft aren't able to do the Zephyr's job, the next question may be well, what exactly IS its job?
The thinking behind the Zephyr is relatively simple and gloriously humanitarian; there are still many parts of the world without internet, TV, navigation aids or access to other things which we in the developed countries have used to further ourselves, so why not make it available to those less fortunate as well? According to the head of unmanned aerial systems at Airbus, Jana Rosenmannm, they have ambitions for the Zephyr to be able fly 'for periods of months, up to six months' at a time, which would make it even more viable as an option. Let us not forget that the only way currently for such technology to be available to us is to send a satellite into space. This is a complex, very expensive and very polluting activity, so being able to achieve a similar result with a 'high altitude pseudo-satellite' (HAPS) is a very appealing option. Airbus are also pitching the Zephyr for disaster management use, as well as for environmental landscape monitoring and surveillance in conflict zones, enabling communication with the 'most unconnected parts of the world' in times of disasters. The Zephyr is also able to provide the same coverage as 250 cell towers, meaning that people in poorer regions would be able to connect to the world without the need for the expensive and bulky infrastructure traditionally associated with signal towers. Now that we know why there is a need and a market for the Zephyr, we must turn our attention to how they have managed to create such a beautiful machine.
Inerestingly, this unmanned aircraft can be launched by just four military personnel, carrying it on their shoulders as they jog with a light breeze, as the vast wings and low weight mean that this creates sufficient lift for the craft to take off. It is then powered solely by the Sun during the day, with the extra energy being used to recharge its lithium-sulphur batteries, before switching to being battery powered at night time. On the subject of its weight and dimensions, the Zephyr weighs the same as two airplane seats and has a wingspan which is only a third of that of the Airbus A380. These dimensions ultimately will result in a cheaper build for Airbus, meaning a cheaper price for clients, and a craft which is easier to control, land and repurpose than a traditional satellite. Controlling and successfully re-entering a satellite is indeed a very complex and difficult job (I would suggest reading over my dissertation, found on the bar at the top of this page, if you would like to know more about this), so revolutionising the way we control and monitor situations is really a spark of genius by Airbus and their space engineers.
Having previously not had much luck with this project, with one flight ended earlier than expected due to poor weather and another due to turbulence and high airspeed causing wing fractures which ultimately caused it to crash, I am extremely happy for the team at Airbus that the Zephyr project is finally going well for them. Only time will tell if their hopes for its use and abilities are realised, but for now at least it can be said to have pathed the way for the operationalisation of pseudo satellites, and that, I suspect you'd agree with me, is a ruddy good achievement in itself!