If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Performance envelope of the SR-71
As my news server doesn't let me post to a.b.p.aviation, this is the
next best place I can think of for this reply. In answer to a question about pictures of the SR-71 showing a shock wave, several people have responded saying that the SR-71 is not supersonic at low level. Looking for confirmation, I found this URL http://www.wvi.com/~lelandh/exec12.jpg - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. |
#2
|
|||
|
|||
OK! Where's the picture?
"Alan Dicey" wrote in message ... As my news server doesn't let me post to a.b.p.aviation, this is the next best place I can think of for this reply. In answer to a question about pictures of the SR-71 showing a shock wave, several people have responded saying that the SR-71 is not supersonic at low level. Looking for confirmation, I found this URL http://www.wvi.com/~lelandh/exec12.jpg - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. |
#3
|
|||
|
|||
begme wrote:
OK! Where's the picture? Er - I didn't make that as clear as I could have done, did I? I don't know of a picture that shows the SR-71 and its supersonic shock wave; but the performance figures indicate that you would need an exceptional camera to capture it from ground level, or another SR-71 to capture it from altitude... |
#4
|
|||
|
|||
On Sat, 19 Jul 2003 15:12:30 +0100, Alan Dicey
wrote: As my news server doesn't let me post to a.b.p.aviation, this is the next best place I can think of for this reply. In answer to a question about pictures of the SR-71 showing a shock wave, several people have responded saying that the SR-71 is not supersonic at low level. Looking for confirmation, I found this URL http://www.wvi.com/~lelandh/exec12.jpg - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. I hate to tell you this, but 20,000 ft isn't "low level". Low level is a couple of hundred feet off the deck. I suppose you could stretch it to 10,000 ft or so, but the SR is still subsonic at that altitude. Mary -- Mary Shafer Retired aerospace research engineer "A MiG at your six is better than no MiG at all." Anonymous US fighter pilot |
#5
|
|||
|
|||
Had a conversation with Daryl Greenameyer about the SR and he commented the
Q-limit (max permissible indicated airspeed) was 600 kts (IIRC). That would make is subsonic at sea level, supersonic @ 20K. R / John "Alan Dicey" wrote in message ... As my news server doesn't let me post to a.b.p.aviation, this is the next best place I can think of for this reply. In answer to a question about pictures of the SR-71 showing a shock wave, several people have responded saying that the SR-71 is not supersonic at low level. Looking for confirmation, I found this URL http://www.wvi.com/~lelandh/exec12.jpg - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. |
#6
|
|||
|
|||
Mary Shafer wrote:
I hate to tell you this, but 20,000 ft isn't "low level". Low level is a couple of hundred feet off the deck. I suppose you could stretch it to 10,000 ft or so, but the SR is still subsonic at that altitude. ????? Mary, given your past association with the Blackbird, I am perplexed that you choose to castigate my use of the English language rather than give us the benefit of your experience: the site I gave a link to says that the information is unclassified, and I had hoped that you could at least confirm that it was broadly correct. I can only read your response as telling me that I should have written "/relatively/ low level". Looking at the graph I linked to should make it clear that my whole point was that the SR-71 was subsonic at levels low enough to be seen and photographed from ground level, and indeed all the way up to 20,000 feet or so. I would say that you can't call it "low flying" until one or more of the crew, ground observers or wingmen are scared My father-in-law ended up as a specialist Navigator on Canberra PR9's after a career which included Vulcans and Phantoms; he reckoned you weren't into "low flying" until you got down to 50 feet. To get back to the original question: do you know of any photographs that show the shock-wave pattern generated by an SR-71? I can't imagine that any exist, other than of wind-tunnel models, but the original enquirer (on a.b.p.aviation) thinks so; what might he be thinking of? |
#7
|
|||
|
|||
Mary Shafer wrote in message . ..
On Sat, 19 Jul 2003 15:12:30 +0100, Alan Dicey wrote: As my news server doesn't let me post to a.b.p.aviation, this is the next best place I can think of for this reply. In answer to a question about pictures of the SR-71 showing a shock wave, several people have responded saying that the SR-71 is not supersonic at low level. Looking for confirmation, I found this URL http://www.wvi.com/~lelandh/exec12.jpg - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. I hate to tell you this, but 20,000 ft isn't "low level". Low level is a couple of hundred feet off the deck. I suppose you could stretch it to 10,000 ft or so, but the SR is still subsonic at that altitude. Mary Is there a physical reason why? Or is it because of rules/regulations? David. |
#8
|
|||
|
|||
David McArthur wrote:
Mary Shafer wrote in message . .. On Sat, 19 Jul 2003 15:12:30 +0100, Alan Dicey wrote: snip - a page from "The SR-71 Reconnaissance System Executive Handbook", written by Bill Majors (Lockheed ADP), which gives the performance envelope of the SR-71. And yes, it is subsonic to about 20,000 feet. I hate to tell you this, but 20,000 ft isn't "low level". Low level is a couple of hundred feet off the deck. I suppose you could stretch it to 10,000 ft or so, but the SR is still subsonic at that altitude. Mary Is there a physical reason why? Or is it because of rules/regulations? David. I believe someone mentioned that it's a Q limit (i.e. physical strength of the airframe), 600? KCAS in this case. Guy |
#9
|
|||
|
|||
Mary Shafer wrote:
OK, a guy at LaRC figured out a way to take Schlieren photos of the shock field using a modified camera, an airplane, and the sun. He took a photo of a T-38 at Wallops that ended up in AvLeak. Go to www.dfrc.nasa.gov and select the technical reports. Search for Ed Haering. One of his papers is about the two F-18s experiment and another is about mapping the SR-71 shock field. One or the other should have the Schlieren. If not, try the press releases. This is probably from about 1996. Thank you Mary, your pointers are exactly what I was hoping for. Searching the Dryden reports server gave me several hits for Ed Haering, but most of them were to do with sonic boom recording. I did find the following relevant links, though: - NASA Factsheet: Schlieren Photography - Ground to Air http://www.dfrc.nasa.gov/Newsroom/Fa...-033-DFRC.html Schlieren Photo Gallery Contact Sheet http://www.dfrc.nasa.gov/Gallery/Pho...TML/index.html Schlieren EC94-42528-1: Schlieren photograph of T-38 shock waves at Mach 1.1, 13,000 feet http://www.dfrc.nasa.gov/Gallery/Pho...94-42528-1.jpg Your confirmation that Schlieren photography was the technique in use was valuable in itself: I couldn't be sure that NASA hadn't found some other exotic way of photographing shock waves! A little more searching lets me find this report on the Langley server: "Visualization and Image Processing of Aircraft Shock Wave Structures" http://techreports.larc.nasa.gov/ltr...sfvip-lmw.html It contains Schlieren photos of T-38, F-18 and SR-71 shock waves: but, the SR-71 shock wave photo's do not include the image of the aircraft! |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Performance Comparison Sheet | Ed Baker | Home Built | 6 | December 2nd 04 02:14 AM |
A36 performance Figures | Anthony Acri | Instrument Flight Rules | 2 | December 1st 04 07:55 PM |
High performance homebuilt in the UK | NigelPocock | Home Built | 0 | August 18th 03 08:35 PM |
CUrtiss Hawk 75 performance debate | Jukka O. Kauppinen | Military Aviation | 3 | July 16th 03 10:45 AM |