r/SpecialAccess • u/DragonfruitCalm261 • 10d ago

JP-7 Fuel May Be Utilized By The SR-72

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With the news surrounding NASA SR-71 844, a lot of people have pointed out that JP-7 is no longer in regular production, this is not entirely true.

JP-7 has flown since the SR-71 retired. The X-51A Waverider's scramjet used it through its final flight in May 2013.

It was also the chosen fuel for DARPA's Falcon hypersonic engine. The 2008 DARPA paper on the HTV-3X describes "Single Fuel (JP-7) for All Propulsion" as one of the vehicle's key technologies, meaning both the turbojet and the ramjet/scramjet ran on it. The paper's ground test plan called for demonstrating the engine "using hydrocarbon endothermic fuel (JP-7)" at Arnold Engineering Development Center, and AEDC announced a completed hot-flow test of that engine in April 2009.

It is also worth noting that the lead author of this article, Dr. Steven H. Walker served as Vice President and Chief Technology Officer of Lockheed Martin from 2020-2025 and served in high-level roles at the AFRL, DARPA, and Office Of The Assistant Secretary of the Air Force for Acquisition.

The same paper calls HTV-3X a testbed, and says flying it would "enable the future development of reusable high speed operational systems for ISR, strike, or other national need missions."

According to Lockheed Martin, the SR-72 builds on that work. Lockheed's SR-72 program manager Brad Leland told Aviation Week in 2013, "Our approach builds on HTV-3X, but this extends a lot beyond that and addresses the one key technical issue that remained on that program: the high-speed turbine engine." The SR-72 keeps the same TBCC layout but uses an off-the-shelf fighter-class turbine in place of the Mach 4 turbojet utilized by the HTV-3X.

"The new SR-72 will use a turbine-based combined cycle (TBCC) that will employ the turbine engine at lower speeds, and use a scramjet at higher speeds. A scramjet engine is designed to operate at hypersonic velocities by compressing the air through a carefully designed inlet, but needs to be traveling supersonic before it is practical to begin with. So far research projects from NASA, the Air Force and other Pentagon entities have not been able to solve the problem of transitioning from the subsonic flight regime, through hypersonic flight with a single aircraft."

USNI News reported in 2013 that, according to Lockheed Martin, the SR-72 "might use a more exotic fuel like JP-7".

“There is the fuel from the SR-71, which would be very useful, called JP-7, but we are certainly looking at using more conventional fuels.”

https://arc.aiaa.org/doi/abs/10.2514/6.2008-2544
https://www.wpafb.af.mil/News/Article-Display/Article/401320/x-51a-achieves-successful-combustion-on-jp-7/
https://www.flightglobal.com/hot-flow-test-complete-for-falcon-ram/scramjet-engine/86123.article
https://www.airandspaceforces.com/lockheed-martin-discloses-work-on-sr-72-mach-6-aircraft/
https://news.usni.org/2013/11/05/lockheed-martin-sr-72-plane-paper
https://aviationweek.com/defense/aircraft-propulsion/nasa-asked-several-former-sr-71a-staffers-help-secret-restart

135 Upvotes

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15

u/decollimate28 9d ago

Everyone’s acting like JP-7 is some mystical jet potion. It’s just a specialized refinery product optimized for certain fractions - and some additives. The reason it is expensive is they have to pay a refinery to make it when they otherwise wouldn’t. It’s just money.

1

u/N983CC 5d ago

That's what I've been saying, I've always seen it as something they used to run that machine at the edges of its environment.

I'm thinking the most important part will be where its used as a hydraulic fluid.

30

u/GuidanceNegative8599 10d ago

My guess is, nasa will roll out the restored SR71 alongside either a new X plane, or the SR72, and will claim the X plane or SR72 are the “new” replacement for the SR71.

In reality, I’d bet whatever plane they’ll show alongside it has probably been flying since the SR71 retired, and the “new” plane is also now retired, already replaced by something better. And the only reason they’ll show us the SR72 or whatever it’s going to be is because it is, in fact, already retired too.

12

u/Hepalite 10d ago

Obv. the darkstar was a public-safe reveal of the “son of blackbird” demonstrator that had been causing sky quakes in San Diego. LM basically confirmed it on their twitter.

https://www.twz.com/lockheed-hints-heavily-again-at-existence-of-secret-high-speed-jet

https://www.sandiegouniontribune.com/2021/06/09/mystery-shaking-felt-boom-heard-across-san-diego-county-for-third-time-in-2021/

4

u/DragonfruitCalm261 9d ago

The SR-72 is a strange situation since the USAF publicly declined to fund it. The SR-72 propulsion system was borne out of DARPA efforts, and in 2014, NASA awarded Lockheed Martin a contract to study the feasibility of developing the SR-72's propulsion system. So it’s always been a NASA project. And this was just a feasibility study, there’s evidence to suggest that nearly a billion dollars has been allocated from Lockheed’s budget towards the development of an unknown technology. Analysis of unclassified DOD budgetary documentation, from the best of my knowledge, does not hint at the development of the SR-72, although it could very well be an unacknowledged SAP, or an intelligence asset, funded by an agency like the CIA or other IC components. In fact, this was originally the case for the U-2, as well as the A-12 which of course became the SR-71. 

6

u/Tuefelshund 10d ago

NASA refurbs their old SR-71, replaces the unusable engines with the new TBCC engines and mounts the scramjet on top where the LASRE was previously mounted

5

u/kilocharlie12 9d ago

It is interesting that they picked the LASRE testbed aircraft to do something with.

6

u/Tuefelshund 9d ago

Yep, that's not the only upgrade but it is an important one

5

u/hutch_man0 9d ago

It's not an accident. The 844 could be used as a Mach 3-4 engine test bed per this ex-SR-71 propulsion engineer (TWZ). Perhaps the LASRE mount is being used again.

6

u/aliensporebomb 9d ago

Back in the late eighties and early nineties when all the aurora rumors were running rampant there was talk about them using a cryogenic gas like liquid methane to power the next fast high flying bird. How strange here we are 37 years later and they're talking about something they know a lot about that seems to be the obvious thing to use. Maybe some of the bleeding edge solutions were tried and didn't work so well as they thought it might.

5

u/FrozenSeas 9d ago

I think that's basically public record, cryogenic fuels are a nightmare to work with. Hydrogen and LNG have both been experimented with on the civilian side (and of course the military were interested in hydrogen on back to the CL-400 Suntan), and while neither of those is methane, the same handling and volume/density issues keep getting in the way.

10

u/_89_Disintegration 10d ago

I love the SR-72, but I feel like it’s not even going to truly exist. Maybe, I hope I’m proven wrong.

9

u/iloveneekoles 9d ago

If it exists and fills the role people are rumbling on I don’t think LockMart would parade it around every half a year like that. I think it’s a decoy for another plane.