Supersonic with a propeller plane !

[Jukka]

I have been thinking. If you had very big surface area plane with 240 ft span and had Solar cells on it and batteries...and unlike a Solar Impulse you would be using both sun and batteries to propel the craft on at very high altitude you brake the sound barrier just like Alan Eustace did at 120 000 ft. I am pretty sure it is doable.

What do you all think ?

[1:1 Scale]

Re: Supersonic with a propeller plane !

And what exactly would this airplane be flying through that had enough mass to keep it aloft and propel it to such speeds?

[Race5]

Re: Supersonic with a propeller plane !

And what exactly would this airplane be flying through that had enough mass to keep it aloft and propel it to such speeds?

Exactly! Felix and Alan went supersonic straight down. BIG difference.

[Jukka]

Re: Supersonic with a propeller plane !

Exactly! Felix and Alan went supersonic straight down. BIG difference.

Check NASA Helios speed at different altitudes. You ought to know better than this as x-15 hurdled at above 300 000 ft.

[Jukka]

Re: Supersonic with a propeller plane !

Paul. MC Cready craft used 13 % efficient Solar panels on an aircraft that weighed just 2000 lbs. Now the newest film thin panels at Nasa have 33% efficiency. MIT just released they have doubled the litium battery capasity. You get my point ?

[V1670]

Re: Supersonic with a propeller plane !

Exactly! Felix and Alan went supersonic straight down. BIG difference.

Just fer giggles: what if Eustace wore a propeller-beanie on the way down?

[N22252]

Re: Supersonic with a propeller plane !

Just fer giggles: what if Eustace wore a propeller-beanie on the way down?

...with a rope tried to his feet so he could pull the electric plane forward with the rope passing through a pulley anchored to the moon as he fell to Earth...

[Jukka]

Re: Supersonic with a propeller plane !

And what exactly would this airplane be flying through that had enough mass to keep it aloft and propel it to such speeds?

It is gas called air; http://www.engineeringtoolbox.com/st...ere-d_604.html

Above 60 km would be tricky if there was no chance to go beyond M1.

[Race5]

Re: Supersonic with a propeller plane !

Just fer giggles: what if Eustace wore a propeller-beanie on the way down?

World's fastest gyrocopter.

[Jukka]

Re: Supersonic with a propeller plane !

If the propeller beanie was large and lite enuf Alan could land on the Moon too smoothly..kilometer long grafeine blades. NASA has studied several concept to fly an aeroplane like system in Mars atmosphere perfect doable as the gaseous substance there is equivalent to Earth atmosphere at 29 km. Mars has 1/3 gravity compared to Earth.

[drgondog]

Re: Supersonic with a propeller plane !

There are so many 'problems to be solved' for a solar powered a/c to a.) generate the power to get to 100K+ feet, b.) have the structural integrity to overcome even the much lower Dynamic Pressure forces.

The first analogy to point to is the U2 with a 20:1 aspect ration and a Lot of thrust was treading lightly at 55-60K with a very small margin between cruise and stall speeds. What is your plan to convert solar energy to generate more Power Available, than Power required, necessary to even Climb to 100K+? Low wing loading is useful but Excess Power over Power Required is major factor for a.) ability to sustain level flight, b.) Climb in rarified altitudes, much less c.) drive the beast to supersonic speeds.

BTW M=1 at 672 mph at 100,000 feet. Are you planning for a prop driven power plant or somehow converting solar energy to pure jet thrust>

[Jukka]

Re: Supersonic with a propeller plane !

I have no spesific plane, but I am able to conceptualize a 80 m spanning lifting fuselage plane that produces 1000 kw of power using 33% efficient panels. Props are 9-10 m dia...in other words huge...but rotate very slowly 300 rpm. Plane is 40 times lighter than similar size airliner.

[440_Magnum]

Re: Supersonic with a propeller plane !

I have no spesific plane, but I am able to conceptualize a 80 m spanning lifting fuselage plane that produces 1000 kw of power using 33% efficient panels. Props are 9-10 m dia...in other words huge...but rotate very slowly 300 rpm. Plane is 40 times lighter than similar size airliner.

Solar flux at ground level is 1050 watts/sq. meter, above the atmosphere its 1350 watts/sq. meter. Lets assume you're above 80% of the atmosphere and call it 1200 watts/m2 available at altitude.

You want 1 megawatt of electric generation, which is 1300 horsepower, and you have 33% efficient cells. So you're getting 400 watts/m2 assuming the panels are perfectly perpendicular to the sun. You need 1.0e6/400 square meters of cells. That's 2500 square meters of cells... 27000 square FEET of cells. And that's at high noon. Solar cells weigh around 2 pounds per square foot at the low end... so your airplane has over 50,000 pounds of solar cells it has to carry, not even counting airframe, power systems, and the rest of the structure. Heck, lets say you get bare, conformal solar cells that only weigh 1 pound per square foot... 27,000 lbs in solar cells alone, nevermind wiring, airframe, skin, controls, motors, and you're going to lift it and make it supersonic with less than 1300 horsepower???

Wanna re-think this a bit maybe?

[Jukka]

Re: Supersonic with a propeller plane !

I am also counting reflections wing area is 1500 m2. Batteries are 2/3 so total is 3000 kW.

For time being I am making a 1/6 scale model of an electric twin which will be smallest twin and lightest motorized aeroplane ( ever ) in 1/1 scale..so this is POC.

[440_Magnum]

Re: Supersonic with a propeller plane !

I am also counting reflections wing area is 1500 m2. Batteries are 2/3 so total is 3000 kW.

For time being I am making a 1/6 scale model of an electric twin which will be smallest twin and lightest motorized aeroplane ( ever ) in 1/1 scale..so this is POC.

Batteries are even heavier than solar cells. I don't fault you for trying, but put pen to paper and do the math first.