* Posts by mahonj

3 posts • joined 24 Aug 2009

Giant solar-powered aircraft takes to the skies

mahonj

The problem is holding position, not endurance

It seems obvious that this is a test for a long endurance UAV where they put in a pilot during the test phase as they need the flexibility that a pilot gives during development.

This I buy.

However, I am not sure it will be able to remain circling around one point for a long time if the wind gets up. If you can only go 44mph, and the wind is > 44mph, you will start to drift off.

What they need is more power, and hence solar cells that are more efficient for the same mass (check out their website). They would also like better batteries (as would the whole EV world).

They may be in luck with the batteries as loads of people are working on this, it is likely to happen sooner or later. The solar cells are another matter. Lots of people are working on solar cells, but I have not heard of anyone working on very LIGHT ones. This they will have to pioneer themselves.

Then there is the ultimate efficiency of solar cells. These seem to top out at about 38% at present for very expensive ones. They are using 12% ones (for lightness), and we could imagine they could get to say 18% with a little work.

This is still only 50% more power, which might allow them fly 25% faster - say 55mph - this is still too slow to hold position in many stratospheric zones.

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mahonj
WTF?

What is the point of this vehicle?

I don't get the point of it - if it is for a persistent surveillance platform, it will need to be faster to be able to maintain position against winds > 50 mph, which you certainly get at 30K feet.

So it would be unmanned - no problem, but if it can't maintain position, it won't be much use, unless you had a series of them being blown around on the trade winds, and using their power for data transmission.

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Canon slashes megapixels from next-gen PowerShot

mahonj

Image quality, not pixel count is what matters

Finally, common sense has broken out.

Cameras had FAR too many pixels for their sensor size and had become noisy in anything but bright sunlight of flash.

Following the lead of the Panasonic LX3, Canon have topped out the pixels at 10 MP and got the pixel size up a bit.

dpreview.com has a lot to answer for as they publish resolution measurements on perfectly lit targets, but at least some common sense has prevailed here.

Educating the "rest of the world" that pixel size is more important than excessive pixel count will be a tall order - people (especially men) like simple numeric variables to judge by.

Maybe, you just specify the pixel area in square microns (bigger is better).

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