> >
>

# Curvature of horizon?

Military Aviation A forum for the professionals who fly military hardware. Also for the backroom boys and girls who support the flying and maintain the equipment, and without whom nothing would ever leave the ground. All armies, navies and air forces of the world equally welcome here.

# Curvature of horizon?

13th Nov 2004, 05:31

Join Date: Apr 2001
Location: surfing, watching for sharks
Posts: 3,515
FL510 and flat as Kansas. Newspaper was blocking the way however.

13th Nov 2004, 17:18

Join Date: Dec 2003
Location: Green Side
Posts: 24
Been to FL 000.5 but the trees got in the way.

13th Nov 2004, 20:30
ScienceDoc
Guest

Posts: n/a
Or try to look above a long wall running along the seaside. You will definitely see the curvature then.

13th Nov 2004, 22:17

Join Date: May 2004
Location: Up North
Posts: 802
Try a round-the-world cruise. You'll end up where you started, so it must be round!

On a serious note, I think our ancestors worked out the Earth's curvature before it was circumnavigated - perhaps by the shadow of the Earth cast on the Moon. Any thoughts???

14th Nov 2004, 00:45

Join Date: Nov 2000
Location: Far far away
Age: 49
Posts: 715
Try here:

http://mintaka.sdsu.edu/GF/explain/atmos_refr/dip.html

Makes perfect sense to me....

Turns out that I am 1.5 meters tall, I have 6.4 eyes and Vr is 106Kts. A square 3/6.4 x 106 is about 0.00068 times the spped of light and Adrian is 0.039°.

Hey, if that's what the Eng gets then who am I to argue.

14th Nov 2004, 09:12

Join Date: Sep 2000
Location: Over there, behind that tree.
Posts: 581
Curvature of the horizon is an optical illusion caused by the fact that the Mk 1 eyeball is itself spherical. Therefore it stands to reason that you will see any sufficiently long straight edge as a curve. I mean, all the maps I've ever seen have straight edges so the horizon must be straight . . . innit!

14th Nov 2004, 11:28

Join Date: May 1999
Location: Quite near 'An aerodrome somewhere in England'
Posts: 25,573
E pur si muove!

.

14th Nov 2004, 14:42

Join Date: Sep 2000
Location: Over there, behind that tree.
Posts: 581
You've got a mauve cat?

14th Nov 2004, 15:58

Join Date: May 1999
Location: Quite near 'An aerodrome somewhere in England'
Posts: 25,573
No purple pussy - it's what Galileo is alleged to have muttered sutto voce when forced to agree that the Sun rotated around the Earth and renounce his theory that it was the Earth which rotated around the Sun!

"It does move, all the same!"

A motto I've often though of adopting when faced with senior idiots who won't accept clear facts, prferring to stick with their established dogma!

14th Nov 2004, 17:26

Join Date: Sep 2000
Location: Over there, behind that tree.
Posts: 581
Aha! Mr Galilei of Florence - who didn't get an apology for 359 years!

Without established dogma we'd all have to make it up as we went along. Wouldn't that be fun?

14th Nov 2004, 17:33
I don't own this space under my name. I should have leased it while I still could

Join Date: Dec 2002
Location: Lincolnshire
Age: 76
Posts: 16,648
I think I might be able to get a photo of the earth curve. How would I get it on the forum?

14th Nov 2004, 18:40

Join Date: Sep 2000
Location: Over there, behind that tree.
Posts: 581

15th Nov 2004, 19:19

Join Date: Jan 2004
Location: A Barren Featureless Wasteland
Posts: 106
FL 650 (and geometric hight ++) pan as a flatcake.

Perhaps it's a perception thing? Some people are saying they can see it at sea level others are in the flat brigade all the way up?

I have some pictures that 'show' the curvature of the earth (the SOP bolt the camera to the glareshield 'over the shoulder' jobs), one was taken at 370 - It certainly didn't look curved at the time though.

"Fascanating.........."

MT

16th Nov 2004, 00:03

Join Date: Mar 2003
Location: EGOS Field 24
Posts: 1,025
Very many thanks to all those who replied; it's been extremely interesting. Sounds as though the consensus is that there's no consensus!

John

16th Nov 2004, 10:04

Join Date: May 2004
Location: Up North
Posts: 802
It appears you have to be very high indeed to see the whole of the UK!

From BBC news website

British engineers are preparing to push the limits of aeroplane technology.

Boxed and set: Zephyr sits in its packing case ready for despatch
Zephyr 3, a solar-powered propeller-driven vehicle, is set to fly to 132,000 feet (40 kilometres) in the next few months.

Only experimental rocket planes and the space shuttle will have gone higher.

It will rise into the stratosphere to take pictures of a giant helium balloon that will attempt to break the world altitude record for a manned envelope.

But Zephyr - built by QinetiQ, a commercial offshoot of the UK's Ministry of Defence - is more than just a flying camera gantry. The prototype vehicle, and others like it, may soon lead to a cheap alternative to space satellites.

Squadrons of these high-flying solar planes could be stationed permanently in the sky, for use in environmental monitoring or to supply immediate mobile phone coverage in remote areas, perhaps in a disaster zone.

The military, too, believes such platforms will have applications above the battlefield.

Zephyr's chief designer, Chris Kelleher, told BBC News Online: "You can communicate over long distances; at the altitude we are going to, you can see the whole UK, so you can see a very long way.

"You are operating in the sort of region that currently relies on low-Earth orbit satellites but these make perhaps two passes in a 24-hour period, one of which is in the dark.

"These aircraft, if we meet the night-storage of power issues, would operate continuously and indefinitely over a city or battle theatre."

The US space agency (Nasa) has developed a solar-powered plane, Helios, which has already gone to 96,000 feet (29 km). But Zephyr's smaller size will allow it to go higher still.

The British vehicle has a 12-metre wingspan and weighs little more than 12 kilograms. Its Mylar skin covers a carbon composite frame; the solar cells on the top of the wing provide 1 kW of power to five motors.

The model plane motors have been adapted for use at high altitude
Its intended operating altitude has presented engineers with unique problems.

Zephyr will have to cope with extremes of temperature. Sun-facing surfaces will get very hot; shaded regions of the airframe will experience cooling down to about minus 50 Celsius.

A special "space grease" is needed to protect motor bearings. Consideration has also been given to the performance of batteries and electronics to ensure they continue to perform efficiently throughout the flight.

Zephyr is actually quite fragile; it has to be picked up in several places at once or it will snap.

For the ballooning record attempt, Zephyr will be tethered to the envelope's gondola on a 450-metre line. The tether will attach to the end of the wing.

At launch, the plane will be raised on a special beam with its wing in a vertical position. For the first 30,000 feet (9 km), Zephyr will be a passenger under the gondola.

Then its motors will be opened up by one of the balloon's pilots, Colin Prescot, and the vehicle will slowly circle and raise itself into a position to take pictures of the giant balloon.

A high-resolution camera will feed images direct to Earth; a broadband video camera will send moving pictures via microwave link, first to the gondola and then down to Earth.

"Zephyr is stunning - very ambitious," said Prescot, who will control the plane through most of the balloon journey.

"I have a control box with large buttons to direct the trim and yaw of Zephyr by radio link. The buttons have to be big because my fingers inside the space suit I'll be wearing will be very podgy.

"I have a video screen in front of me to keep track of it and I will be able to see it out of the corner of my visor."

At the peak altitude, Zephyr should be making three circuits every two minutes, travelling at a speed of 70 metres per second (155 mph).

Even if Zephyr reaches the intended altitude it will not actually set any official records. The rules for its particular class of aircraft demand vehicles take off from the ground.

All testing points to an attempt on the balloon record in the next three months
"This flight is about validating the assumptions we have made about operating unmanned aerial vehicles (UAV) at high altitude," Paul Brooks, the QinetiQ manager in charge of the Zephyr project, said.

"For future applications, we don't think you'll need to go so high but we're going there because it will be very demanding and will prove the concept."

Colin Prescot and co-pilot Andy Elson plan to make their balloon journey some time in the next three months. As tall as the Empire State Building, their manned envelope will be the biggest ever flown.

The balloon will be launched from a ship off southwest England and will travel out into the Atlantic, taking perhaps 11 hours to get up and down.

British Airways has agreed to move the flight path of high-flying supersonic Concorde further to the south to take it away from the balloon.

16th Nov 2004, 10:56

Join Date: Jun 2003
Location: Back in Blighty...
Posts: 51
Sorry to be picky;

"British Airways has agreed to move the flight path of high-flying supersonic Concorde further to the south to take it away from the balloon.

So Zeyphr's a bit behind schedule, eh?

16th Nov 2004, 17:23

Join Date: May 2004
Location: Up North
Posts: 802
Excellent spot!!!

Sorry to be picky;

"British Airways has agreed to move the flight path of high-flying supersonic Concorde further to the south to take it away from the balloon.

So Zeyphr's a bit behind schedule, eh?
It was a QinetiQ project, after all!!!

17th Nov 2004, 20:39
I don't own this space under my name. I should have leased it while I still could

Join Date: Dec 2002
Location: Lincolnshire
Age: 76
Posts: 16,648
Had a look at my polar photo, unfortunately what the camera saw did not accord with my memory. It was a cheap camera anyway and shot through a small cabin window didn't get much horizon in.

17th Nov 2004, 21:32
Drain Bamaged

Join Date: Mar 2000
Location: Earth
Age: 52
Posts: 427
You guys doesn't know where to look!!!!

Spotted nice topless "curvatures" once at FL001....along a beach....

Sooooo, not high & fast but low & slow

Last edited by ehwatezedoing; 17th Nov 2004 at 23:41.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off