Solar-powered plane to make round-the-world trip

[Faqa]

Link

Round-the-world solar plane debut

By Jonathan Amos
Science reporter, BBC News


Bertrand Piccard unveils his solar plane

Swiss adventurer Bertrand Piccard has unveiled a prototype of the solar-powered plane he hopes eventually to fly around the world.
The vehicle, spanning 61m but weighing just 1,500kg, will undergo trials to prove it can fly through the night.
Dr Piccard, who made history in 1999 by circling the globe non-stop in a balloon, says he wants to demonstrate the potential of renewable energies.
The final version of the plane will try first to cross the Atlantic in 2012.

It will be a risky endeavour. Only now is solar and battery technology becoming mature enough to sustain flight through the night - and then only in unmanned planes.
But Dr Piccard's Solar Impulse team has invested tremendous energy - and no little money - in trying to find what they believe is a breakthrough design.
"I love this type of vision where you set the goal and then you try to find a way to reach it, because this is challenging," he told BBC News.


The HB-SIA has the look of a glider but is on the scale - in terms of its width - of a modern airliner.
The aeroplane incorporates composite materials to keep it extremely light and uses super-efficient solar cells, batteries, motors and propellers to get it through the dark hours.

Dr Piccard will begin testing with short runway flights in which the plane lifts just a few metres into the air.
As confidence in the machine develops, the team will move to a day-night circle. This has never been done before in a piloted solar-powered plane.
HB-SIA should be succeeded by HB-SIB. It is likely to be bigger, and will incorporate a pressurised capsule and better avionics. It is this vehicle which will attempt to circle the Earth (after first making an Atlantic crossing).
It is probable that Dr Piccard will follow a route similar to the one he took in the record-breaking Breitling Orbiter 3 balloon - travelling at a low latitude in the Northern Hemisphere. The flight could go from the United Arab Emirates, to China, to Hawaii, across the southern US, southern Europe, and back to the UAE.
Measuring success
Although the vehicle is expected to be capable of flying non-stop around the globe, Dr Piccard will in fact make five long hops, sharing flying duties with project partner Andre Borschberg.
"The aeroplane could do it theoretically non-stop - but not the pilot," said Dr Piccard.
"We should fly at roughly 25 knots and that would make it between 20 and 25 days to go around the world, which is too much for a pilot who has to steer the plane.
"In a balloon you can sleep, because it stays in the air even if you sleep. We believe the maximum for one pilot is five days."
The public unveiling on Friday of the HB-SIA took place at Dubendorf airfield near Zürich.
"The real success for Solar Impulse would be to have enough millions of people following the project, being enthusiastic about it, and saying 'if they managed to do it around the world with renewable energies and energy savings, then we should be able to do it in our daily life'."

It's not exactly practical, but it's pretty cool if it works, as a proof-of-concept if nothing else.

[Sea Skimmer]

If it works it will open the door to a range of very practical devices. That kind of range has more use then flying around the world, it would also allow for orbiting communications relays and observation UAVs that can stay on station for three weeks (or longer, if the machine is reliable enough) rather then one or two days as current hydrocarbon powered UAVs are limited too. All that weight and power margin used to support two pilots would be space for an awful lot of computer and radio hardware. Currently we could do this, but only by using a solar powered blimp. Blimps are somewhat undesirable because of how much high altitude winds affect them and some other factors.

Batteries that can last a whole night of flying, while also being able to recharge in a single day are going to be a pain, but we do have way better solar cells now then when NASA built Helios.

[Broomstick]

There are also applications where a solar powered flying machine would be handy and wouldn't be required to fly at night, which may make for a smaller, more robust structure (as you could devote all power to flight instead of needing to store some) and eliminate some of the downsides of powered flight, such as the weight and flammability of fuel, not to mention, once past the initial cost of the structure, the energy would be supplied free by the sun.

As an example, the small planes I used to fly would typically carry roughly 100 liters of fuel weighing about 80 kg (much averaging and rounding in that number, as I flew many different models of different capability). With some of those aircraft having an available payload capacity of about 225 kg (or less!) that 80 kg makes a substantial difference in performance - so much so that on very hot days, or with every seat filled, I had to refrain from filling the fuel tanks to the top. Saving 80 kg in weight markedly improves performance at that level of aviation. If the price wasn't too excessive there would definitely be a market for this.

If this could be applied to say, banner towing airplanes - which are flown almost entirely in good weather in daylight - then you'd eliminate both the possibility of running out of fuel and elminate yet another source of engine exhaust in urban areas.

Pipeline patrol is also a typically daylight activity in small airplanes - again, a solar powered aircraft could well fit into that niche.

This might also be useful for search and rescue aircraft, particularly as a slow moving aircraft are ideal for that activity.

Aerial photographers might also be interested in these.

Solar powered airplanes won't replace petroleum powered aircraft entirely any time soon, but given rising petrol fuel prices where solar power is practical it may well find a niche. I'd really like to see solar powered aircraft become practical. As a further advantage they're also going to be a LOT quieter running on solar rather than petroleum fuels as the latter requires noisy, detonating combustion and solar would drive an essentially electrical motor, which is much less noisy.

The other big obstacle, of course, is the cost of the solar power system - if the cost is too high the technology will remain in the category of "stunt". If the price can be brought down to reasonable levels, though I could see it being adopted. I could also see it being applied to other vehicle types where appropriate. Consider, for example, golf carts. Would this work for lawn mowers? (A lawn mower blade being not much different than a propeller). Other applications?

[Starglider]

It will be a risky endeavour. Only now is solar and battery technology becoming mature enough to sustain flight through the night - and then only in unmanned planes.

Argh. This is factually incorrect; the Helios (HP01) experimental solar UAV was capable (in principle) of indefinite sustained flight in 2001. However the test program was incremental and the longest actual flight was 40 hours, prior to being lost in an accident in 2003. The concept of a solar-powered indefinite-loiter UAV for comms and surveillance purposes has been around since the early 80s, but solar cell efficiency and battery energy density didn't cross the minimum feasibility threshold until the late 90s.

[dragon]

Is this the same group that tried a few years back but it only made it around half the world. If so good to see them not giving up.

[Sea Skimmer]

Argh. This is factually incorrect; the Helios (HP01) experimental solar UAV was capable (in principle) of indefinite sustained flight in 2001. However the test program was incremental and the longest actual flight was 40 hours, prior to being lost in an accident in 2003. The concept of a solar-powered indefinite-loiter UAV for comms and surveillance purposes has been around since the early 80s, but solar cell efficiency and battery energy density didn't cross the minimum feasibility threshold until the late 90s.

So my facts are incorrect, and yet you don’t even know which UAV crashed. Sure wasn't HP01. None of them ever flew 40 hours. The longest flight was about 15.2 hours by HP03 the day before it crashed. It would have flown longer that day but the fuel cell system had trouble.

Helios is two UAVs, HP01 and HP03, the latter built out of the former with some new pieces added and four engines removed. HP03 had the fuel cell system and was the one that crashed. If HP01 could sustain indefinite flight, then why the hell was it then modified into HP03 with an onboard fuel cell system then? The point of HP01 was actually high altitude flight, not long endurance.

In fact HP01 cannot fly indefinitely unless you take it near the North Pole in summer; it could not fly longer then 5 hours on battery power. While the craft had surplus power batteries to store it were just too heavy, leading to the fuel cell addition in HP03. A newer UAV should be able to solve this through lighter, more powerful and less numerous solar panels, using the saved weight for a larger load of improved batteries.

The recharging system, cracking water vapor from the air, for the fuel cells was taking a long time to develop meanwhile, so HP03 actually only flew with a fixed fuel load that should have allowed 7-14 days of operations once it was working. It was hoped if this capability could be demonstrated, then NASA could get more funding to fit the recharge system in an extension of the program. At that point then near indefinite flight would become possible.

An explanation of all this can be found in the following NASA report among other places. Please do point out the sections that say ‘pure solar/battery power could have done it all, but we decided to waste time with fuel cells’
http://www.nasa.gov/pdf/64317main_helios.pdf

So yeah maybe in principal HP03 could have flown indefinitly, but it did not even come close to demonstrating this and it had to be way more complex then just solar + batteries. Not good for long flight reliability.

[Starglider]

So my facts are incorrect, and yet you don’t even know which UAV crashed. Sure wasn't HP01. None of them ever flew 40 hours. The longest flight was about 15.2 hours by HP03 the day before it crashed. It would have flown longer that day but the fuel cell system had trouble.

You're quite correct, I thought I remembered that the flight immediately prior to the one that ended in a crash lasted for 40 hours, but looking it up now it was actually a later flight in that HP03 test series that had a planned duration of 40 hours. I'm sorry, I should have checked that recollection before posting.