In the '80s I worked on a classified project which collected a bunch of folk who had worked on unrelated projects. Some of the techies would tell tales, but not the special ops guys who would button their lips about their previous trips, such as to South America. One techie story was pretty far-fetched, but I have to relate it and see if it rings any bells.

[color=yellow]In 1985, one guy told me he came from a Darpa project for the SR-71 blackbird replacement. The replacement would fly much, much faster than the SR-71, which already barely could withstand the high temps of air friction. The titanium plane would leak fuel on the ground from gaps, and in flight would heat up and the gaps would close. So the Darpa scientists approached aliens (at this point I rolled my eyes), and asked for a material stronger than titanium. Aliens responded with a metallic ceramic formula (I didn't hear of metallic ceramics again until superconductors were discovered in the '90s). The Darpa scientists tried to make the material, and couldn't get the components to fuse, metal and ceramic ingredients were like oil and water. So Darpa scientists went back to these aliens and asked how to make this material. The instructions were to pour the molten material on a fast spinning platter surrounded by curtains of liquid helium/nitrogen (I forget) gas. Fine mixture droplets would fling off the platter, freeze in the curtain before the material could separate, and be collected as powder. The scientists asked, how to make the powder into a part, and they were told with a huge press. From that point large sections of airframe and skin could be manufactured, not cheaply though. [/color]

That's the end of the story. I blew it off as bull, but years later I heard of the discovery of thermal and electrical superconductivity of metallic ceramics by the Japanese in the mid '90s. A few years later (late '90s) and the SR-71 was announced retired, and I knew a replacement must already be flying for such a useful aircraft...

Anyway, judge away. Please let me know if this old story carries any weight or none at all.

Originally posted by Dbriefed
Anyway, judge away. Please let me know if this old story carries any weight or none at all.

Nah, don't believe it.


Why would they be willing to tell us about material science, but not things like nuclear fusion, gravimetric propulsion, quantum computing etc.

The aircraft had self sealing fuel tanks inside the hull. Tho the pannels did have a small gap to allow for the expansion when flying at mach speeds. But it did not pee all over the deck and runway when sitting. That is definately a myth. The refueling in the air was becasue they did not have the tanks 100 percent full at take off. The materials used for its construction, the massive engines all contributed to a weight issue if the tanks were filled, and would have requried a very lengthy runway to just be able to lift off.

Thus the refueling after take off. The missions were lengthy and those fuel tanks were considerably large. And when your zooming along above mach 2 for long durations, that sucks up quite a bit of fuel. So they filled up the tanks after the aircraft was airborne.

As to the alien material thing....well thats a nice little tech tabloid tale.



Cheers!!!!

I thought they used rubber fuel tanks to compensate for expansion. Like the Apache helicopter has.

Originally posted by RFBurns
You dont want a ridgid fuel tank that does not compress as it is emptied otherwise you end up with a huge chamber filled with vapors that can go BOOM, especially when your dealing with the heat at mach flight speeds.

[edit on 29-12-2008 by RFBurns]

Actually the SR-71 / A-12 had two dewars of nitrogen that would be added to the fuel tanks to compensate for the use of fuel to prevent the tanks from collapsing and to prevent vapor formation

Originally posted by RFBurns
The aircraft had self sealing fuel tanks inside the hull. Tho the pannels did have a small gap to allow for the expansion when flying at mach speeds. But it did not pee all over the deck and runway when sitting. That is definately a myth. The refueling in the air was becasue they did not have the tanks 100 percent full at take off. The materials used for its construction, the massive engines all contributed to a weight issue if the tanks were filled, and would have requried a very lengthy runway to just be able to lift off.

Actually, it DID leak all over the ramp when sitting on the ground. A crew chief in Okinawa used fuel that leaked out of the plane to put a small fire out once. Scared the bejeezus out of everyone in the hangar, because they thought it was going to catch fire. The flashpoint of the JP-7 was so high that it put the fire out.

As for the fuel at takeoff issue, as FredT said they put nitrogen into the tanks to keep them from collapsing, and to prevent fires or explosions. When they took off, they'd refuel and the fuel going in would force the nitrogen out.

Originally posted by RFBurns
The aircraft had self sealing fuel tanks inside the hull. Tho the pannels did have a small gap to allow for the expansion when flying at mach speeds. But it did not pee all over the deck and runway when sitting. That is definately a myth. The refueling in the air was becasue they did not have the tanks 100 percent full at take off. The materials used for its construction, the massive engines all contributed to a weight issue if the tanks were filled, and would have requried a very lengthy runway to just be able to lift off.

Thus the refueling after take off. The missions were lengthy and those fuel tanks were considerably large. And when your zooming along above mach 2 for long durations, that sucks up quite a bit of fuel. So they filled up the tanks after the aircraft was airborne.

There is some truth in what you have posted, but not entirely.

The SR-71 does leak like a bitch while on the ground, but the refueling after takeoff is not down to that - a lot of missions out of Kadena performed the entire mission on the fuel they had on board during takeoff, and several further missions were operated with full tanks on takeoff.

The reason the SR-71 did not routinely take off with full tanks is simple - the SR-71 had very very poor single engine handling at heavy weights and low speeds, so if it took off with full tanks, there was a risk that the aircraft could end up in a crater at the end of the runway if there was an emergency.

Secondly, the refueling performed a second task - it allowed the fuel tank nitrogen inerting system to operate as it requires a full tank to start with. This could be done on the ground through a process called 'Yo-Yo-ing', where the ground crew filled the tank to capacity and then used the nitrogen inerting system to push fuel out of the tanks until it reached the required mission level, but this process was extremely time inefficient, and increased maintenance requirements of the fuel system (as it used up hours on the airframe that would otherwise be used flying).

As for the tanks collapsing - the SR-71 had a very strict maximum rate of descent to allow the nitrogen system to pressurise the tanks correctly.

[edit on 29/12/2008 by RichardPrice]

Originally posted by Zaphod58

As for the fuel at takeoff issue, as FredT said they put nitrogen into the tanks to keep them from collapsing, and to prevent fires or explosions. When they took off, they'd refuel and the fuel going in would force the nitrogen out.

Close but no biscuit There was no nitrogen in the tanks after takeoff (unless they were doing a Kadena mission, where the yo-yo process was used) - the refueling was used to top the tanks off to the point where the nitrogen inerting system was able to operate.

Thanks for the feedback, I hope to put to rest this story rolling around in my memories. The leaks were mentioned to highlight (to me) one of the problems with Titanium, the strongest metal we knew of at the time. It was also mentioned that each flight would heat-treat the metal (and I believe he mentioned cracking). If Titanium was the strongest material we had and was used at it's application limit, and the goal was to fly a few times faster through the atmosphere, then something stronger was needed.

heres another one for you - the top of the hull tank would empty first , and as the fuel was used to cool the airframe with the tank emptying the top of the frame would heat slightly more than the bottom , leading the the frame bending into a very slight banana shape

Thanks Harlequin, that is interesting. I didn't know that.

MBF, thank you, that is pretty much exactly what was described to me! The difference was molten alloy was poured on a spinning platter rather than into a bowl.

Centrifugal disintegration of molten particles offers one way around these problems. Extensive experience is available with iron, steel, and aluminium. Metal to be powdered is formed into a rod which is introduced into a chamber through a rapidly rotating spindle. Opposite the spindle tip is an electrode from which an arc is established which heats the metal rod. As the tip material fuses, the rapid rod rotation throws off tiny melt droplets which solidify before hitting the chamber walls. A circulating gas sweeps particles from the chamber. Similar techniques could be employed in space or on the Moon. The chamber wall could be rotated to force new powders into remote collection vessels (DeCarmo, 1979), and the electrode could be replaced by a solar mirror focused at the end of the rod.
An alternative approach capable of producing a very narrow distribution of grain sizes but with low throughput consists of a rapidly spinning bowl heated to well above the melting point of the material to be powdered. Liquid metal, introduced onto the surface of the basin near the center at flow rates adjusted to permit a thin metal film to skim evenly up the walls and over the edge, breaks into droplets, each approximately the thickness of the film.

Ah, this is interesting...

Many special products are possible with powder metallurgy technology.... heat shields for spacecraft reentry into Earth's atmosphere...

[edit on 2-1-2009 by Dbriefed]

Originally posted by Dbriefed

MBF, thank you, that is pretty much exactly what was described to me! The difference was molten alloy was poured on a spinning platter rather than into a bowl.

That would be one way to make the powder. We were told that new alloys could be made this way that could never be made by other processes. It would be the only way to fuse materials uniformly that have huge differences in weight and melting temperatures.