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in diameter and14 in. long with a star perforation.‡‡, §§, ¶¶Table 2. CMDB formulations.Content (percent by weight)40-percentbinder50-percentbinderPyro nitrocellulose2025Nitroglycerin1417.5Dibutyl phthate67.5Ammonium perchlorate32.825.45Aluminum powder27.224.55Calculated specificimpulse (lbf-sec/lbm)at 1000 psi to 1 atm261262IngredientsHenderson, after consulting with Rumbel, alsoprovided a description of Atlantic Research’sdevelopment of composite-modified double-base(CMDB) propellants,## which later became important inrocketry. Although Henderson’s short narrative does notanswer precisely how the discovery occurred, it doesprovide many of the details. He says the developmentbegan at Atlantic Research with a laboratory process forthe preparation of plastisol-grade nitrocellulose.

Theindividuals responsible for that process were ArthurSloan and D. Mann, who, Henderson says, patented itwith the rights assigned to Atlantic Research.Nitrocellulose was not suitable in its manufactured stateas an unmodified additive to other propellant ingredientsbeing mixed together because of its fibrous nature.Sloan’s process consisted of dissolving thenitrocellulose in nitrobenzine and then separating the##nitrocellulose out again using water under high shear.This process resulted, Henderson adds, in a compact andspherical product with a particle diameter in the range ofapproximately 1 to 20 microns.

In this form, thenitrocellulose could readily be combined with liquidnitroplasticizers and crystalline additives and then beHenderson remembers casting the propellant grainsand doing static firing, but because his records do notinclude the dates, he guesses the work occurred in 1957.Henderson says that as Atlantic Research’s activitiesgrew, its pilot plant became too small for its needs andthe Naval Proving Ground at Indian Head, Maryland,began to produce CMDB at some point.

AtlanticResearch and other firms in the rocket industry obtainedthe product from the U. S. Navy. Because the AtlanticResearch plastisol process was much simpler, safer, andcheaper than other processes being used, the HerculesPowder Company and other facilities using double-basepropellants adopted it.##From the examples of discoveries by Klager andAtlantic Research, the conditions necessary forinnovation in rocket technology would seem to includeproper education and skills, an exposure tocontemporary problems, awareness of theory but awillingness not to let it dictate empirical investigations,and proper empirical techniques. Another conditionwould seem to be adequate funding and exchange ofinformation such as has been provided by the Joint‡‡Letter from Karl Klager to J. D. Hunley, Oct.

7, 1997.Letter from Charles B. Henderson to J. D. Hunley, Oct 16, 1997.¶¶Telephonic interview of Charles Henderson by J. D. Hunley,Oct. 15, 1997.##Narrative by Charles Henderson and Keith Rumbel dated Sept.30, 1998, sent to J. D. Hunley as an enclosure to a letter from CharlesHenderson dated Oct. 8, 1998.§§8American Institute of Aeronautics and Astronauticstechnical direction of Harold W. Ritchie, a chemisttrained at Purdue University (Lafayette, Indiana).Army Navy NASA Air Force (JANNAF) InteragencyPropulsion Committee and its predecessors, which dateback to the Rocket Propellant Information Agencywithin the Applied Physics Laboratory at Johns HopkinsUniversity (Baltimore, Maryland) in 1946.15, 16Sutton also quotes Ritchie himself with regard tothe Falcon missile: “[Liquid polysulfide]-bondedpropellants gave me one of my greatest lifetimeheadaches because of the cure exotherm and resultantshrinkage on curing—just before [the propellant grain]became solid.

Propellant voids from shrinkage and from(air) bubbles were at first two of our greatest problems. Iinitiated the temperature-programmed cure cycle andalso the slit-plate casting system to remove mixingbubbles.”# Sutton adds, “Later on, pressurized curingwas introduced to allow propellant to flow back into themotor from the head cap area.”#In addition to propellants themselves, other issuesexist, such as testing the propellant grain, materialsresearch for motor cases and nozzles, techniques forignition of the grain, grain configurations, thrust-vectorcontrol and thrust termination, mixing techniques,liners, bonding agents, stabilizers, catalysts, andguidance and control, that still need to be researched.

Ihave read a lot of the literature on research into theissue, but still don’t have a crystal-clear notion ofexactly what combustion instability has contributed tosolid-propellantrocketrybeyondagreaterunderstanding of internal ballistics.These points by Sutton address the quality control andaging issues raised by Hall, and no doubt the design datafor case-bonded grains resulted from this work byThiokol not only on the Falcon missile but also on thejet-assisted takeoff motor. However, the developmentsclearly resulted in some degree from interactionsbetween JPL and Thiokol, not strictly from internalThiokol discoveries.#, 10, 14 A great deal more researchis needed to clarify and provide the details of thedevelopment process outlined by Hall and Sutton.As mentioned above, one other area needing muchmore extensive research is the contribution of work ontactical missiles to solid-propellant technology.

Thispaper mainly concentrates on large rockets and missiles,but Edward Price has stressed that smaller missiles havemade many important contributions. I have not had timeto pursue some leads Price has given me regarding hisown work outside the general area of combustioninstability, but some suggestions are in more readilyavailable literature.Sutton does discuss an improvement in grain designthat Thiokol provided.

JPL had been working on aSergeant sounding rocket but had cancelled itsdevelopment in 1950 because cracks in the star-shapedinternal cavity had resulted in explosions.9 Thiokolovercame this problem as a result of photoelastic grainstudies performed by the Armour Institute, later knownas the Illinois Institute of Technology (Chicago,Illinois). These studies led Thiokol to round the starpoints on the RV-A-10 missile to prevent cracks fromforming during sub- and full-scale motor firings.#, ***For example, Edward Hall has written that by 1950,the Falcon missile had contributed “quality controltechniques for rubber-base propellants, design data forcase-bonded grains, [and] aging characteristics ofrubber-base propellants.”17 Exactly how the Falconmissile contributed these techniques and data, however,Hall does not say.

We do know that although the Falconmissile was built by Hughes Aircraft Company (CulverCity, California), Thiokol developed its motors.10, 18Concluding RemarksThese details constitute some aspects of rocketdevelopment that I have been able to find out fromexisting literature and the comparatively small numberof interviews that I have found time to conduct. But avast amount of research is still needed, much more thanI ever expect to have time to do—especially as I amresearching liquid- as well as solid-propellant rocketry,and liquids have their own separate issues andcomplexities.Some information exists in Sutton’s history ofThiokol about the processes that Hall mentions. At thetime that Thiokol was working on the Falcon missile,the company was also working on a jet-assisted takeoffmotor designated T-40, which used a JPL propellantformulation, and the RV-A-10 missile.

Withoutexplaining how the development occurred, Suttonquotes an early Thiokol employee, Jack Buchanan, asstating, “The T-40 was probably the first successfuldemonstration that internal-burning, case-bonded motordesigns using polysulfide propellants could besuccessfully scaled up to larger diameters.”# Suttonreveals that the development occurred in 1949 under the***Telephoneinterview of Lawrence Thackwell (who worked insuccession for JPL on the Sergeant sounding rocket, for Grand CentralRocket Company, and then for Thiokol on the RV-A-10 missile) byJ.D.

Hunley, Dec. 17, 1995.9American Institute of Aeronautics and Astronautics7Consequently, I solicit your suggestions and evenyour assistance. Assembling a group of people who arealready experts in specific areas of solid-propellantrocketry and are willing to write chapters on the historyof their areas of expertise should be possible. The groupcould address the major innovations in their area;attempt to find out where, when, and how theinnovations occurred; and discuss which rockets andmissiles have employed those innovations.