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National Advisory Committee for Aeronautics, Research Memorandum - An Investigation of Several Supersonic Missile Configurations Directed Toward Minimizing Center of Pressure Travel

An investigation was made in the Langley 9-inch supersonic tunnel
of several missiles having low—aspect-ratio, cruciform, tandem lifting
surfaces with a view toward developing a missile with small variations
of center—of—pressure location at various angles of attack and roll.‘
The investigation centered about a basic configuration having equal-2
span wings and tails.- Modifications were introduced in an attempt to
determine the magnitude of the wing-tail interference and to minimize
the undesirable effects of this interference. !

Presented are summaries of the lift, drag, and pitching-moment i _
results and analyses of these results in the form of tail efficiencies
or center—of-pressure shifts or both of the missile configurations and
various components and combinations of components tested. The angle-
of-attack range was from -5° to 15°. The Mach number range was from
1. 62 to 2. ho, most of the data being obtained at a Mach number of 1.

A method of calculating the effects of wing-tail interference upon
the lift and pitching moments of missiles is presented and the calculated
results are generally in good agreement with the experimental results.

One of the problems encountered in the development of supersonic
air—to-air missiles with low-aspect-ratio; cruciform, tandem lifting
surfaces is the effects of wing-tail interference upon the static longi-
tudinal stability Of the missile. The predominant interference effect
is associated with the changes in the induced flow field at the tail
with angle of attack which cause nonlinear changes in the resultant;
downwash over the tail surfaces._ These nonlinearitiestresult in shifts
in the location of the missile center of pressure which, in the case of
a guided missile, can add prohibitive complications to the control
systems.

An experimental investigation has been made in-th§:Iangley 9-inch
supersonic tunnel to.determine the effects of win -tail interference _
upon the static longitudinal stability of various missile c onfigurations
in the Mach number range of l. 62 and 2. ho at corresponding Reynolds
numbers of .O. 362 x 106 to 0.262 x 106 per inch. The tests were made in
mattempt to develop a missile with little center— of-pressure travel
due to changes in angle of attack, roll, andlMach number starting with
a basic configuration having equal-span wings and tails_and modifying
this configuration in order to reduce the interference effects.