the spy plane Auora

[Gripen]

Isn't the height limit for a plane to fly with out leaving the atmosphere like 60,000 feet? Where the sky is black?

[shawn a]

Hey Gripen, I love OZ, and Opals.
I just had a real good reply dissolve into the internet, but,  sustained level flight is possible above 60,000 ft. I've been in a MIG-31E that got up to 67,000 ft without breathing hard. U-2s and Global hawks can get to 60,000 and higher. the issue I so wonderfully posed in  my deleted reply was - at what altitude does atmospheric friction heating and high altitude balance out? It seems to me that a very high mach aircraft would encounter less heating from friction at higher altitudes, but at some point there would not be enough "air" to support level flight. To me this means that any super high mach "aircraft" would either have to employ "skipping" (going super high to avoid heating, and then returning to the "air" to gain thrust and lift to employ a zoom climb back to an altitude where it could cool off and coast in a relatively friction free environment until it's suborbital velocity required another "skip") or carrying oxidizer, which would seem to reduce it's range considerably. To my simple brain, Aurora would have to either leave the air that causes skin heating, or carry oxidizer to allow it to "fly" at altitudes where there is not enough air to either heat the skin, or provide enough oxygen to burn fuel. What altitude, and what speed might that be?
(My first reply was so much more succinct)
Shawn A

[Raptor]

What about exiting and re-entering the atmosphere completely? Sounds crazy but heck it is possible. So it'll be a spacecraft. Yeah it's pricey. But if it existed it'd have a huge budget.

[Gripen]

If it was a space craft it'd be doing like mach 10+, like the space shuttle.

[shawn a]

I think orbital velocity (somewhere around 17,000 mph) is around mach 25. If Aurora exists, I think it will not be an orbital platform. I feel that there is something kept hidden at Groom Lake, what with the huge hanger that was constructed there with an earthen berm seemingly placed to prevent anyone at the closest legal vantage point from seeing into the hanger with super high-power optics.
Shawn A

[Raptor]

Groom Lake. Heck, everyone thinks there's something there. The Aurora could be in Vegas and we wouldn't even know it. 

[Stitch]

Hey Gripen, I love OZ, and Opals.
I just had a real good reply dissolve into the internet, but,  sustained level flight is possible above 60,000 ft. I've been in a MIG-31E that got up to 67,000 ft without breathing hard. U-2s and Global hawks can get to 60,000 and higher. the issue I so wonderfully posed in  my deleted reply was - at what altitude does atmospheric friction heating and high altitude balance out? It seems to me that a very high mach aircraft would encounter less heating from friction at higher altitudes, but at some point there would not be enough "air" to support level flight. To me this means that any super high mach "aircraft" would either have to employ "skipping" (going super high to avoid heating, and then returning to the "air" to gain thrust and lift to employ a zoom climb back to an altitude where it could cool off and coast in a relatively friction free environment until it's suborbital velocity required another "skip") or carrying oxidizer, which would seem to reduce it's range considerably. To my simple brain, Aurora would have to either leave the air that causes skin heating, or carry oxidizer to allow it to "fly" at altitudes where there is not enough air to either heat the skin, or provide enough oxygen to burn fuel. What altitude, and what speed might that be?
(My first reply was so much more succinct)
Shawn A

The SR-71/YF-12 series of aircraft regularly flew at 80,000-85,000' (25,000m); it could fly higher than that (some sources quoted figures as high as 100,000', but I find that hard to believe), but altitudes above 85,000' greatly increased the chances of a disastrous "unstart", or compressor stall. The J58 was most happy at about 80,000' & M3.2.

However, DARPA has already flown an a/c at speeds in excess of M6 & 95,000' (the X-43A); there are also hypersonic a/c in the works that will, hopefully, exceed M7 this year (the X-51). And, eventually, it is hoped a reusable M20 exo-atmospheric will be flying by 2025 (see picture below).




For a couple of good references, read these articles in the Smithsonian Air & Space Magazine:

http://www.airspacemag.com/flight-today/hyper.html?c=y&page=1

http://www.airspacemag.com/flight-today/hypersonics.html?c=y&page=1

[Raptor]

The difference is that the SR-71 is a line production aircraft, whereas all these others aren't. Small differences in life... 

[iluveagles]

Now, ok, problem with this is that the SR-71s speed is still classified. In fact, practically the only thing on the aircraft that is still classified is the airspeed indicator, the fastest posted speed I've found is Mach 3.5+, but generally, it is listed as Mach 3.2+, it is however, always listed with that plus after the speed. It's altitude is listed in between 85,000ft up to 100,000ft and the U-2 operates in excess of 90,000 in fact it has a 5 degree window, so to speak, where if the nose goes above that 5 degrees you exit the earth and fly into space and the if you do the opposite you end up ripping the wings off.

SR-71 wise, through a few different sources it is not at all unlikely that it has a top speed of above Mach 5. The fact that it's engines are ramjets only provides more in sight to the matter.

[tigershark]

Welcome back iluveagles

[iluveagles]

Thanks! 

[Raptor]

Ah i would agree on that "SR-71 over Mach 5" bit.. I mean, loads of Russian airframes are pushing mach 3 easy.. And the SR-71 still claims to be the fastest. 

Anyway, back on topic, any news on the Aurora?