SR-71 Fuel Tank Question

[Jane-DoH]

Assuming it's not classified, does the SR-71 have trim-tanks, or was center of pressure managed aerodynamically only?

[Just This Once...]

Yes it did use fuel to improve trim drag and the lateral limits were extended during the life of the SR-71 to improve high-mach cruise performance, albeit at the loss of some longitudinal stability. Testing these reduced stability limits contributed to the loss of an SR-71 and one of its crew.

[Molemot]

Most things seem to be available on the web, these days....

SR-71 Online - SR-71 Flight Manual (http://www.sr-71.org/blackbird/manual/)

[18greens]

Fascinating.

Page 1-4. The fuel is not only a source of energy but is also used in the engine hydraulic system.

[5 Forward 6 Back]

18greens, lots of aircraft use fuel in the hyd system as a coolant. Even the Tornado!

[HTB]

Ah, yes. Those well known tongue-twisters: air cooled fuel cooler and fuel cooled oil cooler.

[Old Fella]

The SR-71 also utilised fuel to act as a heat sink during High Mach Numer flight to protect against overheating aircraft and engine components.

[jamesdevice]

I've seen stated several times (though I don't know how accurately) that at one point it was intended that the A-11/YF-12/SR-71 would burn boron hydride fuel (like the XB-70 was planned to do...)
Given the leakiness of the tanks and the pyrophoric nature of boranes I think the results would have been interesting to say the least! Dumping heat into a borane could only result in one thing

[sturb199]

Ah, yes. Those well known tongue-twisters: air cooled fuel cooler and fuel cooled oil cooler.

And never forget those bypass mounted air cooled air coolers!! :E

[Jane-DoH]

Molemot

Most things seem to be available on the web, these days....

The article seems to suggest that the fuel in the forward tank drains and that shifts the CG aft; not fuel being moved into tanks (that are empty when subsonic) like on the B-58 and Concorde.

I suppose if it works, it works though.


jamesdevice

I've seen stated several times (though I don't know how accurately) that at one point it was intended that the A-11/YF-12/SR-71 would burn boron hydride fuel (like the XB-70 was planned to do...)

I do know that the Lockheed A-2 (Angel-2), which was one of the early concepts for what would eventually become the A-12 (Archangel 12). It had J-58's mounted mid-span and large afterburners mounted on the wingtips. The ramjets burned Pentaborane. This was eventually done away (I don't know the exact reason, but Pentaborane is 2,000 times more deadly than cyanide, I think it's pyrophoric, and probably corrosive; it also leaves white smoke behind it as the byproducts cool off, which would make the plane easy to spot) with and other designs were pursued.

Interestingly, I don't know if the Angel, Arrow, Archangel series (A-1 and A-2 were Angel, and A-11 and A-12 were Archangel) were connected together (like Angel 1,2, Arrow 3,4, Archangel 5-12) or separate designation lists (Angel 1-6, Arrow 1,3, Archangel 1-12)

[jamesdevice]

Comments like "Pentaborane is 2,000 times more deadly than cyanide" are just nonsense. You'd just about get away with sniffing Pentaborane (as long as it didn't explode in your face), but I wouldn't like to try that again with cyanide. Did it once, nearly got killed.
There are some major handling problems with it though -the wiki entry should give some pointers
https://secure.wikimedia.org/wikipedia/en/wiki/Pentaborane
Not something to be sitting on top of.

I'll always regret not taking up the offer I was given in 1985 of buying part of Russia's excess stocks after they binned their boron fuels program. An Academician from Perm called me out of the blue with a business proposal, but the political logistics at the time simply would have been too difficult. They had a wide range of different borane chemicals available - more than Callery in the USA were offering

There would probably have been more success with an organoborane (e.g. Methylborane) dissolved in a synthetic hydrocarbon, but they don't seem to have explored that very far.

[Jane-DoH]

jamesdevice

Comments like "Pentaborane is 2,000 times more deadly than cyanide" are just nonsense.

I was told one of the boranes were 2,000 times more deadly than HCN. Diborane?

You'd just about get away with sniffing Pentaborane (as long as it didn't explode in your face), but I wouldn't like to try that again with cyanide. Did it once, nearly got killed.

I guess you're right.

There would probably have been more success with an organoborane (e.g. Methylborane) dissolved in a synthetic hydrocarbon, but they don't seem to have explored that very far.

Why haven't they assuming it's not classified?

[jamesdevice]

"I was told one of the boranes were 2,000 times more deadly than HCN. Diborane"
I assume you mean 2000x more toxic? if so, you're way off. Boranes aren't toxic - just flammable / pyrophoric with a tendency to form unstable explosive impurities.

"Why haven't they assuming it's not classified? "
from the materials the Russian had available I think they probably tried it, but my guess is they didn't have the technical expertise to scale it up. Both handling the borane, and large scale production of the synthetic hydrocarbon was probably beyond their materials handling skills.
As to the USA -sorry, don't know: its a technology the guys at Callery don't like talking about, even now. However the synthetic hydrocarbon manufacturing technology would have been available: that was all sorted during WWII by Henry Channon in his researches into synthetic fuels. But maybe they simply found that the synthetic fuels were good enough without needing the borane

[Jane-DoH]

sturb199

And never forget those bypass mounted air cooled air coolers!! :E

A bypass mounted air-cooled air-cooler?

[sqanze]

Anybody know if the follwing is correct... the SR-71 was originally called the RS-71 but on the rollout day the President named it SR and nobody wanted to embarras him with an awkward correction.:oh:

[hval]

Sqanze,

I read and heard the same story. Years later I as told a different story.

General Curtis LeMay preferred the SR (Strategic Reconnaissance) designation and wanted the RS-71 to be named SR-71. Before the July speech, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the story that the president had misread the aircraft's designation

[jamesdevice]

According to Non-Standard DOD Aircraft Designations (http://www.designation-systems.net/usmilav/nonstandard-mds.html) the number is a continuation of the B- bomber series

Quote:
"The SR-71 designator is actually a continuation of the pre-1962 bomber series, which ended with the B-70 Valkyrie. Late in its career, the B-70 was proposed for the reconnaissance/strike role, with an RS-70 designation. The "RS" prefix (sometimes written as "R/S") was actually allowed as an explicit "special case" in the orignal 1962 issue of the designation regulations. When it was clear that Lockheed's A-12 aircraft (then used by the CIA) had much greater performance potential, it was decided to "push" a USAF version of that one instead of the RS-70. This USAF version was to become the RS-71. "Conventional" wisdom now says that then president Lyndon B. Johnson messed up the designation in his public announcement and called it the SR-71 - and nobody wanted to correct the president. Because the strike mission had been cancelled anyway, "SR" was quickly reinterpreted as "Strategic Reconnaissance". However, a first-hand witness of those events recently revealed in Aviation Week & Space Technology, that LBJ did not misread anything. In fact, then USAF Chief of Staff LeMay simply didn't like the "RS" designator - he already objected it when the RS-70 was discussed, preferring "SR-70". When the RS-71 was to be announced, he wanted to make sure it would be called SR-71 instead. He managed to have LBJ's speech script altered to show "SR-71" in all places. Using archived copies of LBJ's speech, it can actually be verified that it reads SR-71 both in the script and on the tape recording. However, the official transcript of the speech, created from the stenographic records and handed to the press afterwards, shows "RS-71" in three places. It seems that not the president but a stenographer did accidentally switch the letters, and thus create a famous aviation "urban legend".
Anyway, the correct designation for the SR-71 would have been simply R-1A. There is an R-for-Reconnaissance mission letter in the designation system and it doesn't make any distinction between strategic, tactical or other reconnaissance."

[Mechta]

A bypass mounted air-cooled air-cooler? Just a guess, but if such a thing exists it could be for cooling pressurised, and therefore hot, bleed air?