https://www.solarstratos.com/en/plane/
As they say “aim high and you get more”, but maybe they are aiming a little too high here?
They may also need this increase to 600 kg MTOM that is being discussed here in Europe.
Before I buy, maybe it’s a good idea to go for for the ‘buy a ticket’ option and pay according to actual altitude reached.
Wherever they end up, always good to see people trying to set new frontiers!
Oh and what a bunch of losers are you guys in that other thread on TB20 altitudes 
Really very nice. And so cheap! For only 55000 Euros you can book a single flight in it.
Electrical/solar propulsion is certainly the future. But why don’t these people develop a practical product for the end user? Why always “record breaking” stuff that is two orders of magnitude too expensive? And don’t tell me the technology they use will become available for the masses any time soon… a solar powered space suit? That’s just like the old lie that Formula One drives the development of street cars.
what_next wrote:
But why don’t these people develop a practical product for the end user?
Interested in rejoining the aero-engineering staff?
mh wrote:
Interested in rejoining the aero-engineering staff?
There are days when I am tempted…
what_next wrote:
Electrical/solar propulsion is certainly the future. But why don’t these people develop a practical product for the end user?
I agree. What a waste of time and resources, and for what? Gliders (with no engines whatsoever) routinely fly up o 30-40k. The world record is 50k.
To get that plane up there, you apparently need a team of 35 persons. 4 pilots and 8 persons in “communications” ?? You also need 10 “patrons” (whatever they are doing). This is just a media gimmick. A standard glider with a small engine (electric or not) will get up to 75k with no problems. If one person did this in his spare time, it would be great, but a whole “team”.
On the other hand, kind of cool aircraft
I’m going to ask Pipistrel at Aero when they expect to have the Alpha Electro with a 3-hour range. Should still be in my lifetime.
22 m2 solar cells at 24% efficiency produce around 5 kW if the sun is overhead.
They claim to climb to 75000 ft in two hours, so that’s 10 kWh. In addition, it has a 20 kWh battery, so in bright sunshine we have 30 kWh to play with – they will climb using an average of 15 kW of the 35 kW engine power available. I am ignoring take-off for the moment.
In any case, of the 30 kWh electrical energy not all will be useable = 30 × 90% engine efficiency x 85% propeller efficiency is around 23kWh.
That is 83 MJ (megajoule), you need 4.5 kJ to climb a metre assuming ZERO drag, so that would get them to 18.5 kilometres / 60,000ft, and only solar power to cruise.
They can only cruise for two hours, so clearly full sunshine can’t keep them up, so it looks like they need more than 5kW to overcome drag at cruise; assuming 5kW are needed that means 10kWh are lost in the climb to overcoming drag, and hence only 15 kWh are available, meaning a climb capability of around 40,000ft. The real result would be somewhere between the two. (BTW – 5kW for cruise is reasonably consistent with solar impulse, who could sustain a similar power level through a 24 hour cycle)
Given that these guys are no jokers, I guess that they will launch this with some sort of high-altitude tug to get it to 25,000-30,000 feet or higher, so it can achieve its “mission”.
That would be in line with their “solar impulse” feat, where the support crew of this environmently friendly aircraft did fly around in jets…
Thanks Cobalt for some solid calculating..
You are of course a little optimistic assuming the sun is overhead, on the other hand the intensity of the sunlight will be higher up there, so I suppose your 5 kW assumption makes sense.
But how about the effects of the density of the air up there that may preclude them from getting really high up? Of course the electric drive does not care, but the prop will be struggling to push enough molecules backwards, while the wings need a bigger angle of attack (increasing drag), but I’m no aero engineer so I may miss something..
While you’re at it, please calculate when Pipistrel will be able to give me that 3-hour Alpha Electro 
If I go by the rate that the range of electric cars increase could I count on giving myself a nice X-mas present next year? Please say yes, although the wife may say no.
aart wrote:
While you’re at it, please calculate when Pipistrel will be able to give me that 3-hour Alpha Electro
If I go by the rate that the range of electric cars increase could I count on giving myself a nice X-mas present next year? Please say yes, although the wife may say no.
Unless there’s some dramatic breakthrough in battery technology, I’m afraid your wife can sleep peacefully – you won’t have to ask her for quite some time yet
You will have the 3 hour electro once people realise that in weight limited applications, carrying the electricity in batteries is not the best way, and move to fuel cells or high-efficiency gas turbines for electricity generation, together with battery boost for take-off and climb.
Give it a decade or two.
