NASA Edwards Flight Research Center Hypersonic Studies of 1964

[hesham]

Hi,

from NASA archive;
http://www.nasa.gov/centers/dryden/pdf/87708main_H-361.pdf

 

[KJ_Lesnick]

How did they plan to manage hypersonic performance with takeoff speeds of 175 to 200 kts with landing speeds on par with a modern subsonic aircraft? Either they overestimated their abilities, or later hypersonic aircraft designers didn't do their job all that well.

KJ

 

[avatar]

exactly , that means that they were relying on some still not mentioned aero-braking concept

 

[Lee]

KJ_Lesnick, quoted: "How did they plan to manage hypersonic performance with takeoff speeds of 175 to 200 kts with landing speeds on par with a modern subsonic aircraft?

I make a supposition: The consensus amongst SST design teams in the 60's was that the plane would be designed with engines sized for cruise speeds only. Until then, subsonic jets had engines sized for takeoff and then the throttle was lowered to conserve fuel at ~35,000 ft.
See what I mean? One only needs modest engines and a slower rate of climb to get to 55,000-75,000 ft with an SST. High pressure ratio engines will allow Mach 2 speeds and conserve fuel as well. www.globalsecurity.org indicated in an entry for the SST that the plane would cruise at Mach 2.7 without afterburner!

http://www.globalsecurity.org/military/systems/aircraft/b2707-design.htm
(about halfway down the page)

This would have given the SST military-rated "supercruise" ability in a civilian aircraft(!) U.S. military and intelligence agencies would be squirming about such a feat today, to be sure!

 

[KJ_Lesnick]

I make a supposition: The consensus amongst SST design teams in the 60's was that the plane would be designed with engines sized for cruise speeds only. Until then, subsonic jets had engines sized for takeoff and then the throttle was lowered to conserve fuel at ~35,000 ft.

With the B-2707 (MTOW: 675,000 lbs initial) you're actually correct. It's T:W ratios for the early GE-4 models (40,000 dry/52,000 wet) when operating at dry power would have only been better than a turbojet powered B-707, heavy B-720's, and DC-8's. With afterburners though, it's takeoff performance would be on par with a modern-day light/medium airliner.

Drag levels at 35,000 feet though would be improved as it could vary it's wingsweep (30-deg for takeoff, low to medium subsonic / 42-deg for transonic speed, supersonic-penetration / 72.5-deg for supersonic flight) and with afterburners it's T:W would be good at that altitude (Turbojets lose less thrust at altitude than turbofans -- the only jets that had the T:W ratios that the B-2707 had back then were turbofans) compared to most airliners, it's engines provide a good thrust with small engine-diameter, and the exhaust velocity is nice and high which is good for penetrating the sound barrier.

The L-2000-7 depended on which engine powered it to an extent, although I guess it wouldn't be considered all that impressive for most jets but I doubt it would be considered bad even dry as it's T:W ratio would not be much different than an early model Boeing 727-100 at sea-level. With afterburner it's thrust to weight ratio would probably be in excess of virtually any commercial jet (Concorde with contingency-power on afterburner would beat it -- however that's an emergency setting, I don't know about the A-318 or A-319; I did see a chart of the T:W ratios for modern airliners and it was very high, more than 1 lb of thrust per 3 lbs weight... but I don't recall the exact number).

See what I mean? One only needs modest engines and a slower rate of climb to get to 55,000-75,000 ft with an SST.

Actually... the climb-rates are probably pretty good for an SST. It's not just pitch angle that determines climb, it's also speed. The faster the speed, you can climb much faster without having to raise the nose a lot.

High pressure ratio engines will allow Mach 2 speeds and conserve fuel as well. www.globalsecurity.org indicated in an entry for the SST that the plane would cruise at Mach 2.7 without afterburner!

Later models of the SST did have the ability to cruise-with afterburner, the B-2707-300. They ditched the swing-wing by that point and went with a tailed double-delta. The plane was a lot lighter, and carried a significantly less passenger load. The later GE-4's were also more powerful: Dry power settings exceeding 50,000 lbs, with afterburner figures going almost to 70,000 lbs. Eventually, GE began persuing even more advanced designs that didn't have an afterburner at all with thrust ratings going all the way up to 85,000 lbs.

To the best of my knowledge the earlier B-2707's required some degree of continuous afterburn for cruise, though I could be wrong.

This would have given the SST military-rated "supercruise" ability in a civilian aircraft(!) U.S. military and intelligence agencies would be squirming about such a feat today, to be sure!

Why would they squirm about it... the Concorde could fly supersonic continuously for a long time and it didn't seem to bother the Brits too much.

Plus it would be a logical conclusion that if the US built a Mach 2.7 airliner, they'd be working on bombers, fighters and such that could go faster.


Kendra

 

[Lee]

KJ, quoted: "With the B-2707 (MTOW: 675,000 lbs initial) you're actually correct."

That was the one I referred to. That's the way it was designed.





KJ: "...-- the only jets that had the T:W ratios that the B-2707 had back then were turbofans)[/i] compared to most airliners, it's engines provide a good thrust with small engine-diameter, and the exhaust velocity is nice and high which is good for penetrating the sound barrier."

Absolutely right. The B2707 with turbofans would have had more of a problem unless the pressure ratio was increased.





KJ: "...I did see a chart of the T:W ratios for modern airliners and it was very high, more than 1 lb of thrust per 3 lbs weight... but I don't recall the exact number)[/i]."

I've seen more than one Gov't report that said the T/W for SST was also best at about .3-.4 for most economy. (1 lb thrust/3-4 lbs of takeoff weight.)





KJ: "Actually... the climb-rates are probably pretty good for an SST."

I saw in Jane's All the World's Aircraft for the Concorde and TU-144: Concorde climbed at about 9,800 ft/min and TU-144 did about 5,000 ft/min. A little faster than a 747, right?





KJ: "It's not just pitch angle that determines climb, it's also speed. The faster the speed, you can climb much faster without having to raise the nose a lot."

Oh, yeah! Civilian pilots need to balance speed and climb angle carefully. Same with all planes, really.





KJ: "Later models of the SST did have the ability to cruise-with afterburner, the B-2707-300. They ditched the swing-wing by that point and went with a tailed double-delta. The plane was a lot lighter, and carried a significantly less passenger load. The later GE-4's were also more powerful: Dry power settings exceeding 50,000 lbs, with afterburner figures going almost to 70,000 lbs. Eventually, GE began persuing even more advanced designs that didn't have an afterburner at all with thrust ratings going all the way up to 85,000 lbs."

I agree. I hadn't heard of the 85,000 lbs thrust engines, though.





KJ: "To the best of my knowledge the earlier B-2707's required some degree of continuous afterburn for cruise, though I could be wrong."

And I agree. T/W wasn't high enough to do without A/B's.





KJ: "Why would they squirm about it... the Concorde could fly supersonic continuously for a long time and it didn't seem to bother the Brits too much."

I meant today after 9/11. The American military is on edge nowadays for that reason.




KJ: "Plus it would be a logical conclusion that if the US built a Mach 2.7 airliner, they'd be working on bombers, fighters and such that could go faster."

Sure, at that time you'd be right. But even the civilian who built a surplus F-104 may not have been seen as a 'patriot' by the today's military brass. A plane like that, even only at Mach one might be seen as a threat to national security. And, I rather believe Sir Richard Branson and his SpaceShipTwo are being watched closely by the authorities. Since I'm a veteran, I know how the military thinks. Viet Nam War era.

 

[KJ_Lesnick]

That was the one I referred to. That's the way it was designed.

And I guess that's why the afterburners were used for takeoff.

Absolutely right. The B2707 with turbofans would have had more of a problem unless the pressure ratio was increased.

The JTF-17A did have a higher pressure ratio than the GE-4 actually. However it also had a bypass ratio of about 1.3:1

I've seen more than one Gov't report that said the T/W for SST was also best at about .3-.4 for most economy. (1 lb thrust/3-4 lbs of takeoff weight.)

You sure you got that figure right? Because 0.3 : 1 = 30% 0.4 : 1 = 40%

I saw in Jane's All the World's Aircraft for the Concorde and TU-144: Concorde climbed at about 9,800 ft/min and TU-144 did about 5,000 ft/min. A little faster than a 747, right?

From what I remember, a Boeing 747 can do about 2,000 fpm when moderately loaded if I recall.

Oh, yeah! Civilian pilots need to balance speed and climb angle carefully. Same with all planes, really.

And high-speed planes. The XB-70's climb rate could adjust by several thousand feet a minute by as little as one degree of pitch. It made it very difficult to fly it at exactly one altitude. The A-12/SR-71, oddly despite flying much faster didn't seem to have this problem!

I agree. I hadn't heard of the 85,000 lbs thrust engines, though.

I did a lot of research on the SST. They were both such fascinating designs. But since neither flew there was virtually no information to find on them even in the early days of the internet.

And I agree. T/W wasn't high enough to do without A/B's.

To the best of my knowledge they were definetly doing non-afterburning supersonic cruise by the time the B-2707-300 came around. The B-2707-200 was almost certainly too heavy and overweight, and I'm not sure if the more powerful GE-4 models were available by the time the B-2707-100 won the contract (Even then, Boeing made some modifications to it's winning designs which included widening the fuselage, adding extra fuel, and making aerodynamic revisions which added some weight -- it was deemed acceptable but I'm not sure if it was acceptable because of the new engines or acceptable with the old ones)

I meant today after 9/11. The American military is on edge nowadays for that reason.

Okay, I understand.

Sure, at that time you'd be right. But even the civilian who built a surplus F-104 may not have been seen as a 'patriot' by the today's military brass. A plane like that, even only at Mach one might be seen as a threat to national security. And, I rather believe Sir Richard Branson and his SpaceShipTwo are being watched closely by the authorities. Since I'm a veteran, I know how the military thinks. Viet Nam War era.

Would make sense.

 

[hesham]

Hi,

also NASA hypersonic transport aircraft.
http://history.nasa.gov/SP-367/chapt7.htm

 

[flateric]

Nope. This is Convair 1966 stuff http://www.secretprojects.co.uk/forum/index.php/topic,323.msg1949.html#msg1949