Feb 212012

The gallery above reproduces “Flash Performance of the P-51D Airplane Equipped with Acid Aniline Rocket Motor,” a test report of The Air Proving Ground Command at Eglin Field, Florida dated October 3, 1946. The object of the tests was to determine the operational suitability of the P-51D airplane equipped with an acid-aniline rocket motor. Two P-51D-25 airplanes, serial nos. 44-73099 and 44-74050, were used for this test. Both were standard production airplanes except for the rocket motor installation.

The rocket motor was located at the aft end of the coolant radiator exit duct. The rocket fuel was a mixture of 65% aniline and 35% furfuryl alcohol, by weight; the oxidizing agent was red fuming nitric acid containing 6½% excess nitrogen dioxide and 5% potassium nitrate by weight. These propellants, as well as compressed nitrogen to force the propellant through the system, were carried in specially designed, non-jettisonable external tanks suspended from the bomb racks. The left tank carried 330 lbs of acid; the right tank contained 125 lbs of the aniline-alcohol mixture, and 27 lbs of nitrogen at a pressure of 2000 psi. The total weight of the rocket system, including the propellants, was approximately 1,090 lbs.

The rocket motor could be used continuously or intermittently, but the combustion rate, and hence the thrust, could not be varied. The unit installed In airplane No. 44-73099 had a rated thrust of 1300 lbs, and the propellants carried were sufficient for approximately 1 minute of continuous operation; the unit installed in airplane no. 44-74050 was rated at 690 pounds thrust with a duration of approximately 2 minutes.

Development of the rocket-boosted Mustang was prompted by the appearance of significant numbers of German turbojet and rocket propelled fighters in late 1944, which caused considerable consternation among allied forces, which had no operational fighter of comparable performance. To meet the immediate and urgent needs of the European theatre, every effort was made to develop various devices, adaptable to fighter airplanes then in service, to provide “flash performance”—momentary performance greatly superior to that afforded by existing war emergency power ratings. Among the proposals that received active consideration were the application of nitrous oxide injection to internal combustion engines; the use of impulse jets, such as the Ford JB-2 engine; solid fuel rocket motors, of the type commonly used for JATO work; and liquid fuel rocket motors such as those described in the report above.

The acid-aniline rocket motor installation in the P-51D was developed in the spring of 1945 by North American Aviation, Inc., with the cooperation of the Aerojet Company, which manufactured the rocket motors. The first installation (airplane no. 44-73099) was ground-fired at Inglewood about a month before the end of the war with Germany; the second (airplane no. 44-74050) about two months later. Although the original need ceased to exist when Germany collapsed, this work was continued with a view of using jet-assisted fighters against the Japanese kamikaze, and in particular, against the rocket-propelled Baka.

The Pacific War came to an end, however, before rocket-on flights were made with these airplanes at The Air Proving Ground. The major portion of this project was thus conducted with the realization that the specific installation, as carried out in the prototype airplanes, would never be militarily employed; interest was focused on certain very general characteristics, knowledge of which would be useful in assessing the merits of future proposals for rocket assist in fighter airplanes.

Testing yielded the following conclusions:

  1. The jet-assisted P-51D airplanes equipped with acid-aniline rocket motors were not operationally suitable and were not useful for any military purpose.
  2. The dangers and difficulties inherent in the handling and use of nitric acid were excessive. It was extremely unlikely that it would ever be desirable to use rockets based on the acid-aniline combination in any aircraft applications.
  3. The drag caused by the external fuel and oxidizer tanks was not large enough to have important effects on the top speed of the airplane.
  4. The rearward CG shift caused by the rocket motor installation had a very serious and undesirable effect on the stability and handling characteristics of the airplane.

Staff at The Air Proving Ground recommended that no further attempts be made to develop acid-aniline rocket systems as auxiliary power for fighter airplanes.

To read the report in depth, please click through the gallery above; photo quality is not ideal but the best available at the time of writing.

All images from NARA Archives II, College Park, MD, RG 18

  4 Responses to “Rocket-Boosted North American P-51D Mustang (1945)”

  1. I do not know why not one of these article correctly mentions that yes, the aircraft were absolutely involved in successful aerial testing. There is extant, 16mm Kodachrome (color) footage of both the ground tests as well as air to air views clearly demonstrating the speed differential from the chase/camera P51 at full throttle to the test plane when the rocket is lit. I therefore must presume the conclusions here are as suspect as the lack of awareness of those successful aerial tests indicates.

    • The conclusions mentioned are from the personnel directly involved in the testing. The rocket propellant was highly volatile, extremely corrosive and toxic and German experience with it in the Me 163 was mixed at best, with a lot of casualties directly related to the use of this fuel.
      Additionally the C of G shift and control problems, while potentially soluble would have come at some cost and delayed the project beyond its use by date.
      It did fly, and yes, it added 100mph to the speed of the Mustang, but keep in mind also that the still faster P-80 had already gone through field trials in Europe before this thing flew, and would have entered widespread service shortly thereafter – the window in which this would have been useful was very small. Additionally the Meteor was already in service, and had the need been great enough, would have been transferred from V-1 interceptions to actual air-air combat. As it was, the problem was solved through tactics (attacking when they were taking off or landing) and destroying the German ability to refuel their jets. When you outnumber your opponent 100-1, it doesn’t really matter how good they are.

  2. Claims require proof.

    I’m from Missouri. Show me.

    Either post a link or an apology.

  3. The Judy radial had a kamikaze ventral triple rocket pack that helped it climb from small carriers as well as dive into ships.
    I imagine the heat on the tail underside could be a problem to both planes.
    The La-7R had the rocket tail pipe in the extreme tailend of the figher, but it was not mass produced.

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