has anyone heard of

[belovelife]

10million Newton-sec. total impulse
wow.
http://www.grc.nasa.gov/WWW/ion/docs/NEXT%20nr.doc

[jab2]

Originally Posted by CraigD

I’m a aerospace vehicle enthusiast,

Slightly OT, but since the OP asked about intakes, I think my question has slight relevance.

I'm a great enthusiast of the SR-71/Oxcart program and have on more than one occasion read that at normal cruise speed more than, I think it's about 70%, of the thrust is generated by the intake cone of the engine. There has been some declassification of data and documents on the program the last couple of years, but I still fail to find any explanation of this intake cone statement, thus am at a loss to understand how it is possible.

So Craig can you explain, or better have links to some info?

[CraigD]

Originally Posted by jab2

I'm a great enthusiast of the SR-71/Oxcart program and have on more than one occasion read that at normal cruise speed more than, I think it's about 70%, of the thrust is generated by the intake cone of the engine.

What that statement actually means is that, at the SR-71’s design cruise speed of about mach 3.1, about 70% of its thrust is produced by afterburner combustion of fuel using air diverted around its J58 engines’ compressor sections. Another way of putting this would be to say that at mach 31., the SR-71 is about 70% a ramjet.

Since, along with its controllable bleed ducts, its movable intake spike is key to controlling how much air is diverted around the compressor section, it’s reasonable to say that 70% of its thrust is generated by the spike, though technically, the spike is source of drag, not thrust.

The primary purpose of the spike is to slow air to subsonic speed before it enters the compressor and compressor bypass. Note that even the bypass air in the J58 is subsonic – if it weren’t, it would technically be a scramjet, like the X-43’s.

The control system for all this is amazingly complicated, using a custom-built analog computer. All this was designed and built, in a hurry, from 1957 to 1963!

The J58 is IMHO better shown in pictures than described in words. From the linked wikipedia article:

[jab2]

Thanks Craig. Been to the wiki page but cannot remember seeing that diagram, even though it was added Feb 07 already.

Make fully sense now. I'm just wondering why they did not just say that the bypass air in AB mode produces the thrust. Maybe to confuse the former USSR spies, but then looking at the Manhattan project their best spies were inside the project so accurate data would have been in Moscow 2 weeks after design.

Do you have any book recommendations on the SR71? I have two of the earlier works (can't remember names now) but that was written before the planes were withdrawn from service and classified data was released. Amazon about 4 months ago recommended a book written by a former pilot to me, but I'm more interested in the systems than flying experiences over Russian.

[CraigD]

Originally Posted by jab2

Do you have any book recommendations on the SR71? I have two of the earlier works (can't remember names now) but that was written before the planes were withdrawn from service and classified data was released. Amazon about 4 months ago recommended a book written by a former pilot to me, but I'm more interested in the systems than flying experiences over Russian.

I’ve never read anything longer than an article on the SR-71, often in a story about the U-2, Lockheed’s Skunk Works and Kelly Johnson, or a couple of chapters in a book about the history of Lockheed, all work more focused on the human history around these aircraft than their engineering.

Unfortunately, I think, despite being subject to state secrecy, the engineering of the SR-71’s Blackbird family of airplanes is likely to remain and even become more mysterious. Its actual manufacturing tools were intentionally destroyed in the late 1960s, and few people with knowledge of its design and building remain alive. With increasingly thorough and side-looking capable satellite reconnaissance, and a lack of military parity between the US and the former USSR, need for Mach 3+ reconnaissance planes, high-speed interceptors, super-fast transports, suborbital transports, etc, is at or near an all-time low. It’s fortunate, I think, that enough interest in scramjets remains to support even the current scaled-back X-43 program, and surprising, given diminishing interest in reusable launch vehicles, which it the main role an eventual X-43 program aircraft is envisioned to fill.

It’s rather a rough, or at lease an unglamorous time to be an aerospace engineer, I think.

I wonder, what sort of strategic direction might improve things?

[gregdevid]

hi,
X-43A rode on the first stage of an Orbital Sciences Corp. booster rocket on March 27, 2004. It was launched by NASA Dryden's B-52 at about 40,000 feet.