Dec 302012

No point in developing a nuclear powered turbojet if you don’t have some sort of idea what you’re going to put it in. In the case of the XNJ140E, three of them were to power the Convair NX2. The NX2 was a research aircraft based on prior design work for a subsonic nuclear powered missile carrier, the Model 54 (not a “bomber,” per se, as it had no internal bomb bay and carried powered missiles rather than gravity bombs).

Numerous variants of the NX2 were designed, taking advantage of different nuclear turbojets. The design shown below used three XNJ140E’s to provide cruise propulsion; but for takeoff, two additional chemically fueled turbojets were provided in underwing pods.

The configuration was an unconventional canard layout. This had the advantage of letting the engines occupy the tail of the aircraft, clear of entanglements with wings or stabilizers. After landings the engines could be relatively easily removed from the aircraft for servicing and storage.

 Posted by at 4:29 pm
Dec 292012

A few months ago some news sites went buggo with the declassification of several reports on the Avro-Canada Project 1794, a late 1950’s effort to develop a VTOL supersonic “flying saucer.” See, for example, Wired wildly inaccurately titled: “Declassified at Last: Air Force’s Supersonic Flying Saucer Schematics,” which ignores the fact that this design had been declassified fifteen or more years ago… I got a report from the NASM in the mid/late 1990’s, and have seen it online for *years.* Heck, a year or two back I made available some Avro documents on the topic (to thunderous silence, I’ll add).

While a technical masterpiece, it suffered from one minor flaw… it didn’t work. The “Avrocar” test vehicle proved wholly incapable of flight… it could hover in ground effect, and slowly wobble about, but could not generate enough vertical thrust to lurch clear of the ground.

Anyway, a few months back the National Archives declassified a box of reports, the tech blogosphere went nuts, and very little actually got posted online, just retreads of what the National Archives put in a single blog post. So, here’s some more Project 1794 stuff.


 Posted by at 8:49 pm
Dec 252012

The General Electric XNJ140E nuclear turbojet was proposed in March 1960 to meet then-current DoD guidelines for the nuclear aircraft program. It utilized a single X211 turbojet mated to a beryllium oxide reactor, a change from the prior XMA-1 engine standard which had one reactor powering two X211 turbojets. Ground test for the XNJ140E was scheduled for December 1962, with flight testing to begin in a Convair NX-2 in 1965.

The XNJ140E was designed for a lifespan of 1000 hours under power, at which point it was to be removed from the aircraft and overhauled. The XNJ140E-1 was to be the developmental model, and would have had an estimated dry weight of 60,600 pounds. Of that, 18,320 pounds were turbojet, while 42,230 pounds were reactor, shield and controls.

The reactor assembly was 33 inches long and 62 inches in diameter, formed from 25,000 hexagonal tubes made from yttria-stabilized beyllia containing uranium. Peak operating temperature was to be 2530 degrees F. The reactor was capable of at least 121 megawatts for a nuclear-only runway takeoff, providing 35,310 pounds of thrust at Mach 0 and at sea level. For cruise at 35,000 feet and Mach 0.8, 50.5 megawatts would provide 8,120 pounds of thrust.

 Posted by at 12:54 pm
Dec 242012

Not much info on this as yet. An early 1958 General Electric study to provide the Snark intercontinental cruise missile with a nuclear turbojet to give the craft 200 hours of Mach 0.9 performance at 30,000 feet. As the Snark had only a single warhead, it’s not at all clear what this performance was hoped to accomplish.

 Posted by at 12:47 pm
Dec 222012

Before the International Space Station was the International Space Station, it was originally Space Station Freedom. This was in the heady days of Reagan and anti-Soviet technological developments such as the Strategic Defense Initiative, the latter half of the 1980s. The Station as then envisioned would have been an all-American Station (although the Europeans and Japanese could tag along with modules of their own), designed to fulfill NASA and DoD requirements, rather than State Department requirements like the ISS. As with SDI, it was grandiose and of course not to be.

The Station as planned circa 1987 could be grown into a “dual keel” design quite a bit larger than the ISS as actually built. It would feature numerous solar power plants, both photovoltaic and solar dynamic. It was planned that a satellite servicing center would be fitted, allowing, as the name suggests, for the repair and refitting of satellites. In order to permit that, a space tug (OMV – Orbital Maneuvering Vehicle) would also need developing that could retrieve the satellites, then return them to their orbits.

Sadly, the Station was always a political football. The cost was immense, and with the collapse of the Soviet Union, the military applications of the Station (not least of which would have been the propaganda value of a Real American Space Station) ceased to seem relevant. Plans were scaled back, it was transformed into an International effort in order to spread cost  and curry political favor, and the ISS end result is but a shadow of what was originally planned.

 Posted by at 10:27 am
Dec 212012

“Code One” is the in-house magazine put out by Lockheed-Fort Worth. They have been adding a lot of good stuff regarding projects to their website over the years, and now have a page devoted specifically to diagrams of unbuilt aircraft:

Aviation Archeology

Only a few just now, but they say that there are a lot more coming.

 Posted by at 11:52 am
Dec 152012

In 1977, General Dynamics produced the “Sneaky Pete” design for a stealthy fighter or attack aircraft. The design was quite similar to that of the later McDonnell-Douglas A-12 Avenger II, a delta flying wing with underslung inlets and a straight trailing edge. There were notable differences: an additional inlet on the upper surface, the exhaust was on the upper surface and there was a single pilot. It also appears that the Sneaky Pete had vertical stabilizers on the upper surface that would fold flush during cruise. Performance, weights, dimensions are all sadly unavailable. Sneaky Pete was part of the design evolution leading to the ATF (eventually won by Lockheed and became the F-22), though it seems very unlikely that it would have been capable of supersonic flight, much less supercruise.

 Posted by at 1:14 pm
Dec 142012

Previously shown but not understood HERE, in 1961 GE proposed modifying a B-52G to serve as a testbed for a single XNJ140E-1 nuclear turbojet. The very large engine would be contained in a nacelle attached to the port rear fuselage. With eight conventional J57 chemical turbojets, the testbed aircraft would be capable of putting the engine through the altitude and airspeed paces that would be expected of it in the NX-2 nuclear powered bomber demonstrator (35,000 feet and Mach 0.8). This configuration would be capable of sustained nuclear flight.

Another configuration would have a second XNJ140E-1 nuclear turbojet on the other side of the fuselage, and only four J57’s. This aircraft would be capable of pure nuclear flight from takeoff to landing, with the J57’s as emergency backup.


Approximate isodose lines around the nuclear B-52G in powered flight

 Posted by at 2:48 am
Dec 112012

In 1954 General Electric studied a nuclear powered unmanned aircraft for a photo recon role. One design considered was the ACA-8, a fairly conventionally configured airbreathing supersonic configuration with small canards and unswept wings mounted well aft. For propulsion the ACA-8 was equipped with a single ACM-1C-Mk II nuclear turbojet with a chemical afterburner. With 9,000 pounds of chemical fuel, 3000 pounds of guidance and control equipment and 3000 pounds of photographic equipment, the gross weight was 50,000 pounds. While the design seems to have some similarity with the Pluto nuclear ramjet, it was a nuclear turbojet, and thus restricted to slower speeds. Maximum nuclear-powered speed at 35,000 feet was Mach 1.57; at design cruise altitude of 40,000 feet, speed was only Mach 1.40. By using the afterburner, at 45,000 fee the max speed was Mach 3.6; at 57,000 feet, Mach 2.5. This could only be maintained for a relatively brief period, however. Note that the design is equipped with landing gear, indicating that it was to be recovered and presumably reused.

At nuclear cruise speed, it was quite interceptable, but the opposing country would have to think long and hard about just how much they wanted to shoot a nuclear reactor out of the sky over their own territory. The best option would be to follow it out and down it over the ocean.


 Posted by at 9:41 pm