Project Pluto

Back in the late 1950’s and early 1960’s, the military started looking towards the 'next' weapon. Intercontinental Ballistic Missiles (ICBM) were all well and good, but everyone was feverishly working on anti-missile systems and the first country to perfect them would render much of their opponents’ nuclear inventory obsolete at a stroke. Project Pluto was conceived as a hedge against that possibility, but has been nearly forgotten over the years and achieved near-mythical status.

So what exactly was Pluto? Simply put, Pluto was an atomic robotic aircraft, designed to fly faster than the Soviet defenses could react, dropping bombs and missiles at targets along the way as it went about its mission. Pluto would be powered by a ramjet, and fly just above treetop level at Mach 3+ (~2500mph).

From a Department of Energy document:

The principle behind the ramjet was relatively simple: air was drawn in at the front of the vehicle under ram (under great force) pressure, heated to make it expand, and then exhausted out the back, providing thrust.

The notion of using a nuclear reactor to heat the air was fundamentally new. Unlike commercial reactors, which are surrounded by concrete, the Pluto reactor had to be small and compact enough to fly, but durable enough to survive a 7,000 mile trip to a potential target.

The name of this experimental RamJet was Tory II-C, and a working model was actually built and successfully run for a few seconds in 1961.

This .pdf document contains a picture of the Tory II-C test engine, which was mounted on a railroad flatcar. The technician working on the engine gives an idea of the scale of the engine, and just how large Pluto would've been.

This site is a nice look at various types of ramjets and how they work.

From the Sci.Space.History newsgroup:

Much of Pluto's rationale was lost when effective ABM systems failed to appear. The concept always had problems with attack routing -- many of the approach routes to the Soviet Union are over friendly or neutral territory -- and with detectability -- it might be hard to catch, but it would be awfully easy to track, since a *less* stealthy aircraft is difficult to imagine. The deathblow was the problem of how to safely test an ultra-high-speed necessarily-unmanned aircraft with global range and a tendency to kill everything under its flight path. Sure, you can run the tests over the Pacific, but what happens when one has a navigation failure? And for that matter, assuming everything works and your test is a success, what do you *do* with the thing at the end of the test? It's intensely radioactive and has no landing gear...

There was also some debate about whether Pluto actually needed warheads. Once again from Sci.Space.History:

The reason why folks wondered whether the thing needed a warhead was the radiation emitted by the engine itself (a completely unshielded half-gigawatt reactor) plus the shockwave generated by a fairly large aircraft doing Mach 3 at treetop height.

Sometimes you have to wonder how we ever survived to see 2000.

You can find more historical context in this paper titled The Decay of the Atomic-Powered Aircraft Program. The paper "examines the technical and socio-political aspects of the United States Air Force's Aircraft Nuclear Propulsion (ANP) program and associated programs, including the reasons the ANP program was undertaken, and the reasons it was canceled after a decade of work."

Posted by Ted at January 13, 2004 07:56 AM | TrackBack