An aircraft's maximum altitude?

don't look at the wingspan, look at the total lifting area of the aircraft as a whole, you can see that from the tip of the nose to the tip of the tail much of the SR-71 can generate lift, especially at high speeds. Indeed, there is only a very narrow strip down the centre of the airframe (the tubular part of the fuselage) that does not act like a wing. This combines with the very powerful engines to give it its immense speed and altitude.

Originally posted by ShatteredSkies
Not really, considering that the Space Shuttle is an aerodynamic designed known as, a Wing Body aircraft.

Sure the Shuttle is made up of Ceramic bricks, and the rockets and main fuel tank might as well be a giant rectangular shape with alot of gas in it, but the shuttle is still aerodynamic.

I thought it was horrific at gliding and fell like a brick that's why the approach speed is so high. Just because it flies does not mean that it is naturally inclined to do so!

The Space Shuttle is more 'steerable' than 'flyable', which is all that is required of course.

A smaller wing makes up for loss of low-speed lift when it gets to the higher speeds, where that same wing has less drag and increased lift. A high performance wing shape.

Which is where adaptive wings get real interesting. Swing wings do the job well, but at the penalty of huge amounts of weight, to hold the two wing pivots together. A design that is still difficult to develop.

Adaptive wings that flex, and/or change shape, will be great. I'd like to see that happen.

SR-71's taking off. I've watched a few do that. After a 50% and a 100% thrust check at the end of the runway, it rolls forward. As soon as it's able, it lifts off, and raises it's landing gear. It then stays low to the runway, and builds up speed and lift. Once it's moving rather fast, it turns almost straight up, and climbs out of sight. I understand that it will climb to 30,000ft and level off, and refuel at that time. Wonderful to see, I will miss them.

Note to shatteredskies: I can believe a flight textbook left that traditional diagram out. I've reviewed many new textbooks that apparently have their own imaginary ideas of how things are. Oddly enough, in mathematics and engineering books, I find tons of errors. It's not right, but publishers have their own agendas. When in doubt, I look in old books from the 1950's and 1960's.

What about Vacuum villed Aerostats, does anybody know how high that can fly?

Originally posted by sardion2000
What about Vacuum villed Aerostats, does anybody know how high that can fly?

Never heard of those. How do you create a vacuum in an aerostat without is collapsing?

Originally posted by waynos

Originally posted by sardion2000
What about Vacuum villed Aerostats, does anybody know how high that can fly?

Never heard of those. How do you create a vacuum in an aerostat without is collapsing?

It would have to be a rigid shell of course, and there are designs in the works here is a good link.

www.gizmag.com...

Even better than Helium , according to Hunt, is the idea to use a vacuum-lift system in the hybrid aircraft. During normal operation of the aircraft, lift is provided by the vacuum contained within rigid cells. As a precautionary measure, the new hybrid aircraft will use a Dual-Aerostatic-Lift system that will include the use of vacuum-lift and the use of a lifting gas. The lifting gas is expanded into collapsible gas bags, in the event of rupture of the vacuum-lift cell wall.

[edit on 5-11-2005 by sardion2000]

Thanks, yes I figured that any such system would need to be rigid but I wondered how you would make it strong enough yet light enough to fly.

Originally posted by waynos
Thanks, yes I figured that any such system would need to be rigid but I wondered how you would make it strong enough yet light enough to fly.

Most likely it will be made of some sort of composit, they are doing some amazing things in Nano-Matrials lately, like certain textiles that can hypothetically be 1/10th the weight of steel yet can be hundreds of times stronger. Here are a few links for ya. Also since you're a Sci-Fi fan get this book, it's what turned me on to this possibility.

The Diamond Age by Neil Stephenson

www.abovetopsecret.com... - Buckypaper

www.abovetopsecret.com... - Diamond-Nanotube composite material.

Hmm, Some pilotes who have flown the Sr-71 have claimed that they have been up to 125 000 feet, you decide if they are telling the truth...

[edit on 12-11-2005 by Figher Master FIN]

Originally posted by veritas 7
Have been wondering for a while now, what exactly determines a planes maximum altitude?

Is it the power of the engines?

The shape of the wings?

Materials used etc?

Or just plain aerodynamics?

Done some research on the subject, but know real conclusive answer's!

Anyone help?

All of the above. The absolute ceiling of an aircraft is the altitude at which the power available from the engine(s) is equal to the power required to maintain the speed at the minimum drag point. In other words, there is no more power available to do anything other than just cruise. Rate of climb goes to zero (because there is no more power available) V(max)=V(minimum drag).

Because the ceiling is dependent on the thrust of the engine and on the drag of the plane all factors come into play.

Aerodynamics - the drag never changes for a plane no matter what altitude it is at. BUT, you have to go at a higher speed for a given point on the drag curve as your altitude increases. This, of course, is due to the thinning of the air as you get to higher altitudes. So if your minimum drag point is say at 100 knots at 5000 ft, then it will shift to say 150 knots at 10,000 ft (just randomly selecting numbers here). This is dependent on airfoil cross-section, wing root chord, sweep of wing, canards vs no canards, all the wing parameters, as well as the cross-sectional area of the entire plane (large cross-sectional fuselage, external fuel tanks vs internal fuels tanks, retractable landing gear versus fixed, etc.) and whether area smoothing has been utilized, etc. and much much more.

Engines - but also at the same time the amount of thrust (power) your engines can produce are decreasing with altitude - again because of the thinning of the air (and of course we are discussing air-breathing engines here).

So you have the two curves converging - the thrust required to maintain speed at a given point along the drag curve increasing (because you have to go faster to stay in the bucket) and the thrust available from the engines decreasing. Eventually they converge at drag minimum and you can't do anything but cruise.

[edit on 11-12-2005 by Valhall]

Originally posted by veritas 7
So how about this then!

If you had a plane that could go to 60,000 ft, because of the height it was designed for, and with the engine's that it had as standard, could you then change engine's, or increase thrust, to make the aircraft go higher? Obviously if the aircraft's frame/structure could withstand it!

Is it possible?

And the answer to this is yes. Pretending you had an engine that was exactly the same cross-sectional area, length, etc. (so you didn't change the drag of the plane) but created more thrust at any given altitude, you would increase the absolute ceiling (i.e. the altitude at which you ran out of excess available thrust).

[edit on 11-12-2005 by Valhall]

Mikoyan-Gurevich MiG-25

On July 28, 1976, an SR-71 set two world records for its class: an absolute speed record of 2,193.167 mph (3,529.56 km/h) and an US absolute altitude record of 85,068.997 feet (25,929 m). Only the Soviet high-altitude interceptor the MIG-25 reached a higher altitude of 37,650 m on August 31, 1977 (see SR-71 at Wiki)

Not sure where that 125,000' altitude is coming from on the SR-71, since the MiG-25 holds the record at 123,524 feet

[edit on 12-11-2005 by Regenmacher]

Originally posted by RegenmacherNot sure where that 125,000' altitude is coming from on the SR-71, since the MiG-25 holds the record at 123,524 feet

It comes from peoples imagination I suppose, the same way they think the SR71 goes much faster than the offical figures. The SR71 should have been tracked on radar fairly easily so if there was any discrepencies with the figures they would have come out by now. The reason everyone thought the MiG25 was a mach 3.2 aircraft was because it was tracked at mach 3.2 on radar, of course we all know now it cooked it's engines in the process. Like the quote below says, the Sr71 could probably make it that high but most of these high records are not for sustained level flight but for basically rocketing up in a sustained climb until the aircraft stalls. The SR71 could not risk doing this because if it did stall it would be extremely difficult to recover and would likely snap in half.

Here's a quote from this site with some clearing up of the myths that surround the MiG25
aeroweb.lucia.it...

Among other records, the Ye-266 set the world's absolute altitude record for a ground-launched aircraft at 118,867 ft. on 25 July 1973. After the Streak Eagle broke many of the Ye-266's time-to-climb records (but not its absolute or payload-to-altitude records), the modified Ye-266M reclaimed its records over a two year period starting in 1975. Some of the Ye-266M's records have since been broken by the Sukhoi P-42, but six still stand. Among these is the absolute altitude record of 123,492 ft. and the altitude record with a 2,000 kg payload, 121,622 ft.

"Ye-266" is actually a invented name. The designation was used to cover three aircraft, the Ye-155R-1, Ye-155R-3 and Ye-155P-1. The former two were modified prototypes of the MiG-25R while the latter was a modified prototype of the MiG-25P. The P-1 was powered by R-15B-300 engines while the R-1 and R-3 used the more powerful R-15BD-300s.

The "Ye-266M" was actually the Ye-155M, a technology demonstrator for the MiG-31. It retained the airframe of the MiG-25P but used the very powerful R-15BF2-300 engines.

It should be noted that the A-12, the F-12 or the SR-71 could all have easily broken the absolute altitude records set by the Ye-155 series, but any such record attempt would be a one-way trip in a Blackbird. The Blackbird has strict AoA limitations which would undoubtedly be exceeded during a zoom to an altitude in excess of 100,000 ft. If the AoA limits are exceeded, a pitch-up results, leading to a structural break-up at supersonic speeds.