Unidentified US 2-stage rocket

[Graham1973]

I was looking through various wind-tunnel test reports on the NTRS and stumbled across a two-stage rocket configuration I am unfamiliar with.

The document provides little clue as to the size of the rocket save this:

The National Aeronautics and Space Administration has designed a high-energy liquid-fuel rocket engine and, for development purposes, a vehicle in which to house this engine. this vehicle is used as the second stage of a two-stage rocket configuration. The aerodynamic characteristics of each configuration must be obtained in order to determine whether any corrective measures are necessary to insure positive stability of each configuration throughout the Mach number range. The separation characteristics should also be obtained in order to determine whether auxiliary separation devices are necessary.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890068098_1989068098.pdf

 

[cardonet]

The first stage of this rocket seems to be a Sergeant or a Castor boosted by a pair of Recruit.
This kind of configuration was used for several 2-stage rockets (Astrobee 1500, Shotput, Strypi 4 & 7, Swick,...). But I never heard about a liquid-fuelled second stage.

 

[Graham1973]

The first stage of this rocket seems to be a Sergeant or a Castor boosted by a pair of Recruit.
This kind of configuration was used for several 2-stage rockets (Astrobee 1500, Shotput, Strypi 4 & 7, Swick,...). But I never heard about a liquid-fuelled second stage.

Neither had I, most of my searching through the NTRS is for Apollo related material and I had thought that this might have been related in some way to Apollo development.

It is interesting to note that the liquid fueled engine is developed by NASA itself. I wonder if it would be still possible to identify the engine?