OT: 787 jet liners approach 800 mph, break records

That makes no sense at all.

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Yer an idiot.

They were talking about NORMAL aircraft nearing the sound barrier.

Bringing in the Concorde is about as stupid as it gets because anyone with even the brains of an abject idiot like Donald J. Trump already knows the Concorde is supersonic.

So, spouting off about it in a thread about craft that are NOT supersonic is superstupid.

You page on page one yet, dipshit?

Den onsdag den 24. januar 2018 kl. 02.54.00 UTC+1 skrev snipped-for-privacy@notreal.com:

unless they were using the trainer model, I find that hard to believe since the pilot cannot navigate the SR71 and the navigator cannot fly the SR71

Bush Sr. was a pilot. He very well could have done the navigation in the back.

Probably could have done the flyin' in the front as well. But yeah... he could have easily managed a trip with only a few waypoints.

Den onsdag den 24. januar 2018 kl. 19.12.41 UTC+1 skrev tom:

it is one thing to be a pilot and know how navigate, that doesn't mean he has a clue on how to run the systems on an SR71

It depends on how you look at it. Records are almost always categorised. Concorde is/was in a different category. You can't really compare a station wagon doing 120 mph to an F1 going at over 200. Or an SR-71 to an X-15.

It would only require a briefing on how to enter the data. Navigation is still the same. Enter a few waypoints and go. Also, there was a qualified pilot driving the plane.

If I ever had the chance, I would do it in a heartbeat.

Thanks for catching that slip. CO2 (straight with mass three points on a line) and water (boomerang shaped) molecules are oddball too, quite different from monatomic and biatomic gases.

Boyles law only applies if the gas mix is kept constant. Also, at the edge of the atmosphere, the temperature rises rapidly to above a thousand degrees. Not enough density for the SoS to be often relevant there though.

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** The speed of a sound wave through air depends almost entirely on the temperature of that air. High altitude air is rarefied for sure, but it is also very cold.

..... Phil

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** Ground based radar systems supply an aircraft's *ground speed* - that is the speed relative to the radar itself adjusted for the actual flight direction.

FL24 uses GPS location data ( transmitted from each plane) and time intervals between changes in that location to compute ground speed. Ground speed is interesting to passengers as it affects their estimated arrival times.

OTOH, pilots are vastly more interested in *air speed" as this determines what they can and cannot allow the plane to safely do. Air speed is found using on board equipment like "pitot" tubes.

.... Phil

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** Whatever the category, the measured *air speed* was the thing.

The effect of wind had to be removed somehow, by flying in both directions along a one mile course for example.

.... Phil

You can't

"They" can do anything.

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** Problem is, pilots deal with air pressure and density all the time.

Air pressure is the primary guide to altitude, something a pilot must know at all times along with air speed in order to fly safely.

** But you have to know the air temp to make any use of it.

** The percentage composition of air hardly varies for aircraft that rely on oxygen content to operate its engines. The usual 21% percentage only begins to drop above ** 100kms ** altitude.

OTOH, the actual amount of oxygen available from a given volume of air falls to half at 18,000 feet and half again at 40,000.

..... Phil

low density increases the speed of sound, inhale some helium and try it out. (actually low mean molecular mass)

pressure doesn't effect the speed of sound much, temperature does.

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It doesn't. Boyle's law describes one of the mechanisms the keeps the upper atmosphere cold. it's also closer to space.

not hydrogen, helium.

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** The speed of sound in any gas is proportional to the square root of its absolute temperature - which is worth remembering.

The actual speed of wave propagation is slightly less than the average molecular speed of the random motion of its molecules - it is impossible for it to be any more.

.... Phil

I suppose these days there's a possibility of an answer from the space station :)

IIRC, that was the end of a dick-swinging contest between a bunch of pilots. Started with a guy in a Cessna asking for a ground speed check. Then a business jet. Next, a fighter. Nobody followed the SR-71's request.

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Paul Hovnanian     mailto:Paul@Hovnanian.com 
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