Republic XF-103 Interceptor

Great video overscan!

The XF-103 was an incredible design for it's era, especially regarding it's propulsion system (it truly could make efficient use of the turbojet and the ramjet) and it's relatively early use of titanum alloys (Douglas to my knowledge ultimately developed the industry standard for titanium development -- but the design started prior to that point).

BTW: Out of curiousity, (not to drift off topic -- the plane's construction sort of IS related to topic) what kind of titanium did it use? Did it use beta-titanium like the A-12, or more conventional titanium alloys?


KJ Lesnick
 
Thanks Overscan. There was another video on US TV recently under the
title: "Secret Superpower Aircraft - Fighters", done by the History Channel.
The DVD set is offered for sale on the internet. Anyway, video of the
mockup's open engine bay being is shown and CGI video of the XF-103
in flight as well as the XF-108 is also shown. The is also a "Spy Planes"
episode that has CGI of Convair's KINGFISH. Not sure if this show has
already been discussed on this site.

KJ, XF-103 was spec'd to use (for the wings for example): "titanium alloys
AMS4809, AMS4925 or other titanium alloys of comparable properties. Sainless
Steels Series 300 and 400 type."

Not sure when the term "Beta" for titanium originated.

As far as the propulsion system being an incredible design. Yes it was.
Within 2 years of the cancellation, Kelly Johnson and Bob Widmer started
work on their M3 proposals. The J58 was really a bleed-bypass cycle and
not a turboramjet, that ended up being a workable substitute, along with
the duct magic, of coarse.

I often wonder about the XF-103 with P&W in the place of Curtis-Wright,
and the project managed as Kelly ran Oxcart, with nobody except him and
his customer knowing what is going on, and everyone else keeping their
noses out of it !

Or, letting Republic go for a turbojet/rocket combined cycle approach, ala
XF-91, like they were interested in at the beginning of the XF-103 program.

Ah! 20/20 hindsight!
 
Good entry point for Ti alloys is here
http://www.titaniuminfogroup.co.uk/datasheets.asp
http://www.titaniuminfogroup.co.uk/media/Data_sheet_11_Aerospace_alloys.pdf
If forum members are interested, I can post Lockheed Horizons article on titanium alloys usage in aerospace industry from from 60s era.

Beta Titanium Alloys

Beta or near beta alloys are:
· Fully heat treatable
· Generally weldable
· Capable of high strengths
· Possess good creep resistance up to intermediate temperatures
· Excellent formability can be expected in the beta alloys in the solution treated condition

Beta-type alloys have good combinations of properties in sheet, as fasteners and are ideal for sporing applications. Some alloys offer uniform property levels through heavy sections.

The higher alloy content of beta alloys increases the density of beta alloys typically by 7-10% compared to Ti6Al4V.

Typical beta alloys include:

Ti3Al8V6Cr4Mo4Zr ASTM Grade 19
Ti10V2Fe3Al AMS 4983, 4984, 4987
Ti15Mo3Nb3Al2Si ASTM Grade 21
Ti15V3Cr3Sn3Al AMS 4914

Correctly, it is only the metastable beta alloys which are heat treatable by solution treatment and ageing. Fully stable beta alloys can only be annealed.

Source: Titanium Information Group
 
rousseau,

You mean the engine pod? You have to keep in mind that in that pod is the inlet, the engine, an upward curved S-duct merging with a large ramjet that doubled as an afterburner. At around Mach 2.25 to 2.5, the engine is throttled down, I would assume the ramjet throttled up, and a pair of doors/ramps covering the inlet and exhaust of the jet-engine allowing the airflow to go straight from the inlet, directly to the ramjet, bypassing the turbojet entirely. From what I remember the transition time from turbojet, to ramjet mode takes roughly seven-seconds.


Kendra Lesnick
 
flateric said:
Good entry point for Ti alloys is here
...
If forum members are interested, I can post Lockheed Horizons article on titanium alloys usage in aerospace industry from from 60s era.

...

Correctly, it is only the metastable beta alloys which are heat treatable by solution treatment and ageing. Fully stable beta alloys can only be annealed.

Source: Titanium Information Group
Click to expand...

Thanks Flateric for the titanium info.
I would be interested in the Lockheed Horizons piece on titanium usage history.
Would it be better in aerospace tech pages or here?

By the way, from the DECLASSIFIED XF-103 Spec ES-336B (1 March 1955)
regarding your metastable beta Ti comment above and also for KJ because she
was interested in XF-103 Ti vs Beta Ti, which your comment seems to shed
light on above:
"All titanium alloy material used shall be in the stabilized condition. Titanium alloys
other than those specified shall be subject to the approval of the Procuring Agency."
 
I've never been able to get this question answered, and this one I have checked on the net, wikipedia, and on various books that mentioned the XF-103A: How did they plan to keep the pilot reasonably cool inside? Did they use a heat-shield, or did they just use the fuel as a heat-sink?

What kind of fuel did the plane use, also? JP-4 or some high-temperature stuff?


KJ_Lesnick
 
rousseau said:
What a long pylon that is! :eek:
Click to expand...

Yes. there are some interesting questions here.

Intended to position the cone shock off the store properly?

Or intended to place the store at the proper point in the fuselage/wing
flow, to enable it to be dropped easier?

Was it intended for M3.7 flight?

Would the pylon alone give any enhanced stability at high mach, therefore
size it for that.

At greater than mach 2.?, I wonder about the feasability of hanging
stuff off the wings like this due to the wave drag and the shock
interactions.

These M3 designs had internal weapons bays for a reason.

Some things to think about and play around with.
 
Are you guys sure that pylon can fly at the plane's full design speed?


KJ_Lesnick
 
KJ_Lesnick said:
Are you guys sure that pylon can fly at the plane's full design speed?


KJ_Lesnick
Click to expand...

Depends what it was made of. One other thing to keep in mind is this thing wouldn't be cruising there for extended periods like a Blackbird or Valkyrie so it wouldnt soak up as much heat (and it's unlikely those tanks would still be hanging under the wings by the time it got to top speed anyway.)
 
I'm kind of wondering if the aerodynamic requirements were so extreme that the plane couldn't even have a conventional canopy, that it could carry large external tanks and fly at full-speed with them hanging on sounds unusual...

I'm pretty sure if that design could operate in a pure ramjet mode that it wasn't designed for any brief amount of supersonic flight, but for sustained periods -- while the plane would not fly at cruise speed as long as an A-12 or an XB-70 would, the plane was less massive than both of them and as a result would heat up proportionately faster actually, right?


Kendra Lesnick
 
KJ_Lesnick the B-58 routinely flew with a large external fuel tank a more than Mach 2.0
 
One reason for the long pylons could be the fact that when you jettison the tanks you want to keep the horizontal stabilizers.
 
Loren said:
KJ_Lesnick the B-58 routinely flew with a large external fuel tank a more than Mach 2.0
Click to expand...

True, but the XF-103 was *way* faster than Mach 2...


Kendra J. Lesnick
 
KJ_Lesnick said:
Loren said:
KJ_Lesnick the B-58 routinely flew with a large external fuel tank a more than Mach 2.0
Click to expand...

True, but the XF-103 was *way* faster than Mach 2...


Kendra J. Lesnick
Click to expand...

but the B-58 stayed at high speed longer. The XF-103 would have been a sprinter something like a faster F-104. It wouldn't have been at high speed for long periods of time.
 
sferrin said:
but the B-58 stayed at high speed longer. The XF-103 would have been a sprinter something like a faster F-104. It wouldn't have been at high speed for long periods of time.
Click to expand...

You sure? Considering all the variable geometry in the design (variable incidence wings to allow the nose to be level with the horizon at all speeds in level flight), the obsessive need for clean lines even the removal of a canopy, and the fact that ramjets are quite efficient at Mach 3+ for endurance or for speed?

I kind of thought the XF-103 would have been an extended-dasher -- not quite a cruiser, but more than a dasher...


Kendra Lesnick
 
KJ_Lesnick said:
sferrin said:
but the B-58 stayed at high speed longer. The XF-103 would have been a sprinter something like a faster F-104. It wouldn't have been at high speed for long periods of time.
Click to expand...

You sure? Considering all the variable geometry in the design (variable incidence wings to allow the nose to be level with the horizon at all speeds in level flight), the obsessive need for clean lines even the removal of a canopy, and the fact that ramjets are quite efficient at Mach 3+ for endurance or for speed?

I kind of thought the XF-103 would have been an extended-dasher -- not quite a cruiser, but more than a dasher...


Kendra Lesnick
Click to expand...

Combat radius was only 450 miles and the ramjet actually sucked more fuel for less thrust than the turbojet. The main reason for the ramjet was because the turbojet couldn't handle the heat.
 
KJ_Lesnick said:
sferrin said:
but the B-58 stayed at high speed longer. The XF-103 would have been a sprinter something like a faster F-104. It wouldn't have been at high speed for long periods of time.
Click to expand...

You sure? Considering all the variable geometry in the design (variable incidence wings to allow the nose to be level with the horizon at all speeds in level flight), the obsessive need for clean lines even the removal of a canopy, and the fact that ramjets are quite efficient at Mach 3+ for endurance or for speed?

I kind of thought the XF-103 would have been an extended-dasher -- not quite a cruiser, but more than a dasher...
Click to expand...

I'm not sure they'd be capable of getting the warning necessary to get a intercept vector for an extended-dasher with 50's radar-warning technology. Anyone know for sure?

Starviking
 
Surely an "extended-dasher" means that it has a great deal more ability to change that vector if its wrong?
 
rickshaw said:
Surely an "extended-dasher" means that it has a great deal more ability to change that vector if its wrong?
Click to expand...

Perhaps I should have said 'detection range'.

If our "extended-dasher" can intercept a hostile out to 1000 miles, but our early warning radar detection limit is 700 miles, then the "extended-dasher" is carrying a lot more weight for its primary mission.

Starviking
 
And the XF-103....
 

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Mark, this is wonderful stuff, thanks again!
 
Courtesy to Richard Pugliese go these USAF SAC from January 1954. Bunch of thanks to him!
 

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XF-103 pics

http://www.nationalmuseum.af.mil
 

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What I'm wondering is how did that thing manage to perform missile releases?

KJ Lesnick
BTW: Did the later XF-103 variants which used the AN/ASG-18 radar with GAR-9/AIM-47 and GAR-1/GAR-3 aka AIM-4's use the SAGE system, or was it designed to work solo?
 
Last edited:
I curious what happens when you open the missile bay doors positioned right before the inlet at Mach 3. How does that affect the airflow at those high speeds.

Also, to prevent hot gas injection, the missile release mechanism would have to be similar to F-22, with the missile separating from the aircraft before igniting its engines. And all that at twice the cruising speeds of F-22 and 30 years prior to it. WOW!
I just see some big technical difficulties there.
 
lantinian said:
I curious what happens when you open the missile bay doors positioned right before the inlet at Mach 3. How does that affect the airflow at those high speeds.

Also, to prevent hot gas injection, the missile release mechanism would have to be similar to F-22, with the missile separating from the aircraft before igniting its engines. And all that at twice the cruising speeds of F-22 and 30 years prior to it. WOW!
I just see some big technical difficulties there.
Click to expand...
All the missile bay doors were positioned at the side of the airframe, so neither engine airflow nor hot gas injection would have been a problem. Give the guys who designed it some credit, will ya?
And FYI you can see those bays quite clearly on the large artists impression a few posts back.
 
I have found the attached drawings that may be of general interest
 

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I have found the attached drawings that may be of general interest (Post 2)
 

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I have found the attached pics that may be of general interest (Post 1)
 

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I have found the attached pics that may be of general interest (Post 2)
 

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I have found the attached pics that may be of general interest (Post 3)
 

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I have found the attached pics that may be of general interest (Post 4)
 

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All the missile bay doors were positioned at the side of the airframe
Click to expand...

Thanks, I just noticed from the scale model. Great engineering thinking. If those missiles follow the same flight profile of AIM-54 Phoenix the placement could't be better for flight performance.

Still, loading them will be kind of .... more problematic than usual.
 
Hi Justo Miranda!

If is and if it is possible show us pictures of following proposal:

Republic Model AP-44 (or pre-XF-103)

source: "Air enthusiast" SEVEN
 
The ‘Air Enthusiast’ article does not mention the AP-44 model, but there is a picture of the XF-91. I assume this is the airplane in which you are interested.


From AIR ENTHUSIAST/SEVEN pp.201
 

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