Future air transport

Little John · Post by **Little John** » 01 Oct 2017, 14:25

I think a quad copter arrangement holding up a vertical line might be a more plausible arrangement - especially given that the copter could be continuously powered from the ground up the line. This arrangement is actually used for surveillance copters already from what I have just read.

The question - in this instance - is how long a line, how much weight in the line and how big a copter would be required to hold the line taught?

Post by **kenneal - lagger** » 01 Oct 2017, 16:38

Little John wrote:...The question - in this instance - is how long a line, how much weight in the line and how big a copter would be required to hold the line taught?

And would you use as much power keeping the 'copter in the air as you would powering the take off of multiple aircraft?

fuzzy · Post by **fuzzy** » 01 Oct 2017, 19:51

This is where the hydrogen filled, remote controlled blimp comes in??

woodburner · Post by **woodburner** » 01 Oct 2017, 23:09

There are several examples in this topic which indicate a lack of understanding of details of gliding dynamics, beyond the simple concept.

Little John wrote:However, one point I would make about the size of the circle at ground level: I am wondering if it may not need to be as big as you suggest. That is to say, the arc of the circle at ground level may be relatively small, whilst the arc of the glider at the top, may be much larger depending on the length of the tow line.

LJ is not the only challenged poster, but this particular post shows no understanding of the practical side of towed flight. Towing in a circle would not work. In real life there is normally a flow of air over the ground. The speed and direction of the flow varies with height, with further variations superimposed if there are thermal effects. Towing with the wind coming slightly from the right gives the best starting conditions. The glider can then drift out to the left and alter direction to face into the wind. As the glider rises it will encounter increasing wind speed, and the direction of the wind shifts further to the right (veers). The wind will never move to the left with increasing height. This allows the glider to angle further to continue facing the wind. The towing vehicle can then slow as the wind increases with height, to prevent overstressing the glider. The glider may by now have changed direction by about 90Âº. This is about the practical limit. As the towing vehicle continues to turn, the glider cannot swing out to maintain a position behind the tow as the wind is continuing to drift the glider, and the towing vehicle would have to increase speed to the glider speed plus the wind speed. For a normal sport glider this could be 80knots, or more. It's surprising how fast the wind at 2000feet is blowing while there is just a gentle breeze on the ground.

woodburner · Post by **woodburner** » 01 Oct 2017, 23:11

fuzzy wrote:This is where the hydrogen filled, remote controlled blimp comes in??

Hydrogen???

woodburner · Post by **woodburner** » 01 Oct 2017, 23:13

kenneal - lagger wrote:
Little John wrote:...The question - in this instance - is how long a line, how much weight in the line and how big a copter would be required to hold the line taught?
And would you use as much power keeping the 'copter in the air as you would powering the take off of multiple aircraft?

You would use considerably more. Hovering is energy expensive.

Little John · Post by **Little John** » 02 Oct 2017, 01:48

woodburner wrote:
kenneal - lagger wrote:
Little John wrote:...The question - in this instance - is how long a line, how much weight in the line and how big a copter would be required to hold the line taught?
And would you use as much power keeping the 'copter in the air as you would powering the take off of multiple aircraft?
You would use considerably more. Hovering is energy expensive.

Ok, cool. Lets have the numbers.

Post by **kenneal - lagger** » 02 Oct 2017, 10:03

Little John wrote:
woodburner wrote:
kenneal - lagger wrote: And would you use as much power keeping the 'copter in the air as you would powering the take off of multiple aircraft?
You would use considerably more. Hovering is energy expensive.
Ok, cool. Lets have the numbers.

Sounds like Mr Hemming!!

Post by **adam2** » 02 Oct 2017, 10:39

An approximation could be obtained from the fuel consumption of a helicopter. Things that we know, or can find out.

Lifting capacity of a large helicopter.
Fuel consumption of same in kilos per hour, when hovering with a load.
Percentage efficiency of helicopter engine.
Efficiency of electric drive.
Therefore electrical loading required to replace the jet fuel consumption with electric power.

Weight of jet engine, half full fuel tank, and related equipment, and how this compares with weight of electric drive, and consequent modification of lifting capacity.

We do not know how much the cable would weigh, since AFAIK, no such product exists at present for comparison purposes.

I suspect that a battery might be needed as well, to permit of a controlled descent if the power failed.

Little John · Post by **Little John** » 02 Oct 2017, 10:47

I was thinking something along the lines of an electric copter, which could hover over a vertical line. Or, an electric plane, which would need to fly around in a circle at the top of a line, which would travel in a cone. Each of these could be powered directly up the line. So, the weight of the craft involved would be pretty much as light as it's possible to have such a craft.

It seems to me the significantly limiting factor in terms of available technologies would be the weight of the line

Little John · Post by **Little John** » 02 Oct 2017, 10:57

Another idea might be to have electric planes with that could ascend to a given height and then jettison the motor and batteries by parachute and glide down for the remainder of the flight?

Post by **adam2** » 02 Oct 2017, 11:05

Little John wrote:Another idea might be to have electric planes with that could ascend to a given height and then jettison the motor and batteries by parachute and glide down for the remainder of the flight?

Unlikely in practice as the batteries are hugely expensive and rather fragile and would be unlikely to survive the fall, even with a parachute.
And where are they to be dropped, I for one do not fancy a ton of lithium battery landing anywhere near me.

Post by **kenneal - lagger** » 02 Oct 2017, 11:05

Little John wrote:Another idea might be to have electric planes with that could ascend to a given height and then jettison the motor and batteries by parachute and glide down for the remainder of the flight?

You would want to be sure that there wasn't a queue to land or a change in the weather at the landing site if you were wholly reliant on gliding with a full load of passengers! I certainly wouldn't be flying on that basis.

Little John · Post by **Little John** » 02 Oct 2017, 23:07

Another option could be wireless power transmission to an electric plane/glider to allow it to get to the appropriate altitude. Then it could glide to it's destination or to the next point of wireless power transmission to allow it to regain altitude before the next leg of the glide-flight

https://en.wikipedia.org/wiki/Wireless_power_transfer

emordnilap · Post by **emordnilap** » 03 Oct 2017, 14:50

It occurred to me that, in looking at electric aircraft, hopefully the air industry is seeing the writing on the wall at last. Their best experts may well be telling them to get out of oil. Dunno, just maybe.

The lack of duty on fuel and VAT on flights may bite them in the bum soon. There's no 'buffer' of taxes which the government of the day can be ransomed or brown enveloped into reducing, hiding fuel cost increases.