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Lockheed CL400 Suntan

CFE

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My biggest question regarding the Lockheed Suntan program is why they bothered investigating hydrogen turbojets in the first place. The best advantage I can think of was the ability to achieve the desired speed and range with an airframe that was much lighter than anything else in its size class (TOGW was less than half of the SR-71, and even 13,000# less than the much smaller F-111!) But from a development standpoint it made sense to investigate conventional turbojets, and the Blackbird series was the correct answer.

Still, Project Apollo, the space shuttle, Atlas and Delta owe much to the hydrogen breakthroughs that were initially made on Suntan. In that regard, the effort was a shining success.
 

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The USAF and USN had been looking at hydrogen fueled engines before 1950. The idea was to develop an engine capable of supporting high-speed flight. Eventually it was determined that hydrogen fuel was not a very smart way to go, as you'd need a massive jet to carry enough fuel to have any serious amount of range.
 

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..
 

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SOC

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Exactly. And when they started really fooling with it, they discovered that the amounts of fuel you'd have to carry would result in a 300 foot long aircraft.
 

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Suntan 304 engine
 

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sferrin

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SOC said:
Exactly. And when they started really fooling with it, they discovered that the amounts of fuel you'd have to carry would result in a 300 foot long aircraft.

Just look at the difference in size between a Titan IV and a Delta IV Heavy. The Delta dwarfs the Titan for roughly the same payload.
 

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It would seem like hydrogen would be of most benefit to aircraft traveling faster than Mach 2.5. Suntan's structure would have been able to take the aerodynamic heating without the need to use hydrogen for active airframe cooling.
 

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"LIQUID HYDROGEN AS A PROPULSION FUEL,1945-1959" [NASA SP-4404]

http://history.nasa.gov/SP-4404/contents.htm

SUNTAN section:

http://history.nasa.gov/SP-4404/ch8-1.htm
 

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I remember that much earlier (late 90s) chapter on Suntan had cool isometric views of Suntan iterations that now are gone...
 

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PlanesPictures

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some time ago I started work on CL-400's family visualization but I wasn't satisfied with my done 3D drawing of these next models. Do you know some other drawings of these beautiful projects?
 

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foiling

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I love these CL-400 designs. Does anyone know of good 3-views of them?
 

hesham

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Hi Foiling,


in the site itself,you can get good shots;


http://xplanes.free.fr/suntan/cl400-4.html
 

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LOCKHEED’S FADING SUNTAN
Between Kelly Johnson’s cutting-edge U-2 and SR-71 designs for Lockheed sits the outlandish hydrogen-fuelled CL-400 Suntan project; Dr David Baker tells the full story.


There is an interesting article of the CL-400 Suntan project published in newest issue of the magazine "The Aviation Historian - Issue 12 2015".
This article from page 68 to page 79 has two illustrations of the CL-400-10 and one graphic, how the P&W Model 304 engine would have worked.
These illustrations were done by Ian Bott and Neil Fraser. B)
One of them I have attached as an appetizer. ;)
 

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swampyankee

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CFE said:
My biggest question regarding the Lockheed Suntan program is why they bothered investigating hydrogen turbojets in the first place. The best advantage I can think of was the ability to achieve the desired speed and range with an airframe that was much lighter than anything else in its size class (TOGW was less than half of the SR-71, and even 13,000# less than the much smaller F-111!) But from a development standpoint it made sense to investigate conventional turbojets, and the Blackbird series was the correct answer.

Still, Project Apollo, the space shuttle, Atlas and Delta owe much to the hydrogen breakthroughs that were initially made on Suntan. In that regard, the effort was a shining success.

For a lot of reasons, hydrogen fuel is much better for turbojets than hydrocarbons. One is that a major portion of the heat load on the turbine blades and vanes is radiation from microscopic carbon particles in the exhaust stream. Another is it can be used to cool stuff more effectively than Jet-A, which may have chemical reactions in warm areas that can reduce heat transfer effectiveness.
 

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Hi guys,
during a research on the Lockheed CL-400 (Suntan) I found this small picture of what appears to be the mock-up of the airplane. I do not know the source. According to what AIR International wrote (December 1985, page 311): The first two CL-400s, of eight intended to be built, were reported to be “almost completed” when the decision was made to scrap the CL-400. No photographs have been released. – Ed.”
It's been more than 30 years. Since then has not appeared any picture of the complete mock-up or prototypes in construction? Yet the CL-400 seems to me a fascinating subject ...
Nico
 

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overscan (PaulMM)

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Its from Jay Miller's book "Lockheed Skunk Works" P.107. This book is your best bet for CL-400 information. Judging from what Miller says it seems unlikely the prototype was near completion, but Bill Slayton (unpublished) does repeat the 8 prototypes contracted and 'nearly complete prototypes' information - but I don't know his source.
 

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Given the size of the beast, I doubt that 8 airframe could have been completed without anyone finding a trace today. The Skunk work building was not that big. Birds would have had to be ferried away. it is doubtful that this had not drawn any attention.

Ben Rich who was working on assessing the viability of operating large amount of the H2 fuel at the time never mentioned such things.
 

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TomcatViP said:
Given the size of the beast, I doubt that 8 airframe could have been completed without anyone finding a trace today. The Skunk work building was not that big. Birds would have had to be ferried away. it is doubtful that this had not drawn any attention.

Ben Rich who was working on assessing the viability of operating large amount of the H2 fuel at the time never mentioned such things.

In his memoirs, Ben Rich writes that they had one prototype airframe and tanks under test at least. It sprung a leak and they called the fire brigade before realising that the aircraft was classified. The dilemma was solved by the supercool fuel chilling the air of the hangar so that it filled up with fog, hiding everything. There may be a bit of leg pulling going on with that story.
 

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Wow, never realized that the Suntan went that far - one mockup, one partially completed airframe. Very interesting.
 

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https://oac.cdlib.org/findaid/ark:/13030/c86d5rqx/entire_text/

Box 3
Projects

Folder 1
Engineering—CL-400

Folder 2
Engineering—CL-400 reports (1973)

Folder 3
Engineering—CL-400, Langley meeting (1973)
 

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http://www.codeonemagazine.com/images/media/2013_SW70_08_CL400_Suntan_1267828237_8352.jpg
 

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overscan (PaulMM)

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I believe that the various images Cl-400-11/12/13/14/15 stem not from the initial design phase but from additional studies done in 1957 when it was becoming clear the original CL-400 wouldn't reach range targets - Lockheed proposed an additional 14 configurations of increasing size and complexity.
 

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hesham

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PaulMM (Overscan) said:
http://www.codeonemagazine.com/images/media/2013_SW70_08_CL400_Suntan_1267828237_8352.jpg

Wow,nice find my dear Paul.
 

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Suntan refueling. The beautiful aerial depiction looks like Jozef Gatial's work!
 

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Archibald

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Aerial refueling of liquid hydrogen would have been one heck of a giant PITA.
 

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I recall that the first mentions of a Lockheed LH2-powered project surfaced when the company was proposing an experimental LH2-powered TriStar in the late 1970s. I think, too, that at one point one of the Lockheed leaders - may have been Ben Rich - casually tossed out a statement which sounded as if the aircraft was almost complete at the time of cancellation. However, Jay Miller's (later) book told a very different story, where the design never closed enough to start building an airplane.
 

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"Aerial refueling of liquid hydrogen would have been one heck of a giant PITA."

https://www.youtube.com/watch?v=RWDxxnl0lhw
 

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LowObservable said:
I recall that the first mentions of a Lockheed LH2-powered project surfaced when the company was proposing an experimental LH2-powered TriStar in the late 1970s. I think, too, that at one point one of the Lockheed leaders - may have been Ben Rich - casually tossed out a statement which sounded as if the aircraft was almost complete at the time of cancellation. However, Jay Miller's (later) book told a very different story, where the design never closed enough to start building an airplane.

According to NASA's document "Liquid Hydrogen as a Propulsion Fuel, 1945-1959," Ben Rich disclosed the details of Project Suntan in 1973. One of the biggest problems that surfaced was the issue of range. The USAF believed the aircraft could fly 2800 km, while Kelly Johnson thought the most they could do was 2000 km. Johnson thought that adding additional hydrogen would only grant them only a 3% increase in range. As time wore on and technical issues developed, support for the project waned. Gen. Curtis LeMay did not like the project thinking that his pilots were effectively flying a hydrogen bomb and he preferred the money on Suntan were spent elsewhere. At the programs end in Feb. 1959 the only hardware developed was the 304 engine, plants for liquid hydrogen production, and the tests apparatus used in the testing of LH fuel handling by Lockheed.
 

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The problem of keeping LH2 in cryogenic conditions while cruising at high speed was too hard to solve at the time (weight of the tanks - and remember that cruise speed was down to Mach 2). One just have to look at the size of the Saturn rockets to understand how much fuel was needed... for each pound of fuel lifted. Those were achieving their goals with minimal payload ratio. The main problem with aviation is that the plane is part of the payload. You don't discard one for each flight. This where the range goal pushed them toward enormous planes. Add to that the complexity of handling fuel while sustaining an operational tempo and the advantages with H2 were soon dwarfed with other design having more conventional forms of propulsion (A-11 design then A-12)).

@PanesPictures: Wonderful animation (and choice of music!). Wouldn't they need much more alpha both since I doubt that you'd have had boom refueling at Mach 2 (the design speed)?
 

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PaulMM (Overscan) said:
https://oac.cdlib.org/findaid/ark:/13030/c86d5rqx/entire_text/

Box 3
Projects

Folder 1
Engineering—CL-400

Folder 2
Engineering—CL-400 reports (1973)

Folder 3
Engineering—CL-400, Langley meeting (1973)


I fired off an email to the library inquiring about getting copies/scans of these materials. Here is the response:

Thanks for contacting The Huntington Library. We offer imaging services for most of our special collections material including the Ben Rich papers. Our most cost-efficient option are PDF scans for $1/image. I have provided instructions for requesting images at the end of this email.

That said, the folders you are interested in contain quite a bit of material. I glanced though the boxes and estimated folders 2-5 in Box 2 contain approximately 100 pages, and folders 1-3 and 5-6 in Box 2 contain 250 pages. Additionally, there are schematics in Box 2 folders 2 & 5 that would be considered oversize when laid flat, which adds a flat $50 special set-up fee to the cost. If you were request images of all the material in the folders, It would likely cost around $400.

Two alternative options: if you're looking for something specific, you might be able to describe it for me and I'll try to find it within the folders. There's also a lot of xeroxed publications among the material, so if you limited your requests to the schematics and unpublished portions of the folders, it would reduce the cost. Second, if you live locally, I can offer you a one-day pass to visit the library and look through the folders yourself. You would be able to photograph the material and/or subsequently order scans.

So.... anyone want to pool funds together on getting scans? I would suggest ditching photocopies of magazine articles and published books and whatnot and just asking for the Good Stuff. What I inquired about ( Box 2, Folders 2,3,4 and 5; Box 3, Folders 1,2,3,5,6) include:

Folder 2

Engineering A-12
Folder 3

Engineering—A-12 schematics
Folder 4

Engineering—F-12
Folder 5

Engineering—R-12 schematics
and

Folder 1

Engineering—CL-400
Folder 2

Engineering—CL-400 reports (1973)
Folder 3

Engineering—Sea Shadow (stealth ship)
Folder 5

Engineering—Senior Prom
Folder 6

Engineering—Aeroballistic rocket (low cost access to space, 1993)
 

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I'm going ahead with this. I've inquired back with the library about the cost of getting everything but magazine articles and pages from regular books scanned, this will drop the cost some unknown amount. I raised the issue at the APR Patreon and have 11 people signed up so far. So anyone else interested, let me know.
 

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Orionblamblam said:
I'm going ahead with this. I've inquired back with the library about the cost of getting everything but magazine articles and pages from regular books scanned, this will drop the cost some unknown amount. I raised the issue at the APR Patreon and have 11 people signed up so far. So anyone else interested, let me know.

I am very interested
 

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