Could the Scarab UAV be turned into an effective land-attack cruise missile, as the NDIA once thought?

Near-term Stealth Option: Modified Scarab (Scarab-LACM)

Type: Land-Attack Cruise Missile version of Scarab



Powerplant: undetermined

Significant date: 1999

In the face of the rising threat posed by the proliferation of cruise missiles, conversion of the Teledyne Ryan Model 324 Scarab UAV to an offensive weapon has been considered. A study from the NDIA (National Defense Industrial Association) recognizes the role Land-Attack Cruise Missiles (LACM) developed by Third World countries will play in conjunction with other new weapons, for regional force projection. "LACMs are an 'emerging' threat with immediate and dire implications for U.S. freedom of action in many regions. The asymmetrical development of Third World threats favors indirect engagement and unconventional warfare. Unconventional cruise missile acquisition and design methods considered in the study support such asymmetrical threat development as a means Third World countries can significantly reduce the development time, cost, and risk."

For this study it was assumed that the LACM midcourse and terminal guidance system has the same weight and volume as the existing UAV guidance and control system. In addition, it was assumed that deletion of the reconnaissance payload and recovery system provided sufficient space for a small conventional payload. The Scarab UAV modified to a land-attack cruise missile (Option #1) could deliver a 200 kg conventional payload to a maximum range of 2,250 km flying the high altitude UAV flight profile. Flying a low altitude profile (less than 500 m altitude instead of 13,000 m) enables a range capability of approximately 1,800 km. Part of this performance loss (typically 15-20%) can be regained by reducing the wing size and shape and other changes to make the vehicle more efficient for low altitude operation.

If a larger payload is desired, the vehicle’s fuselage and tankage could be modified to accommodated a larger payload. This would result in a loss in fuel loading to maintain the same overall vehicle envelope. Option #2 incorporates the same Scarab-LACM conversion changes identified for Option #1, but further modifies the vehicle to accommodate a 500 kg conventional payload. The change results in a 237 kg loss in loaded fuel. The Option #2 Scarab-LACM is capable of delivering the 500 kg conventional payload to a maximum range of either 810 km or 650 km flying the high or low altitude flight profiles, respectively. Some of the range losses can be regained if selected aerodynamic changes are also made.

The modified Scarab-LACM range performance can be varied without altering the vehicle’s overall external geometry. The missile’s airframe/tankage can be revised to accommodate less fuel to increase volume for payload. As shown, a 300 kg increase in payload weight (200 to 500 kg) requires a 227 kg (206 versus 443 kg) reduction in loaded fuel weight. The HE payload is assumed to have a density ~ 30% greater that the JP-4 fuel (JP-4 weighs 0.78 kg/liter). By varying the payload weight and corresponding fuel loading, the Scarab-LACM can achieve a factor of three in range performance without changing the vehicle’s external geometry.

Population: not built (feasibility study only)

Specifications: see text

Crew/passengers: none

Main sources:
- "Feasibility of Third World advanced ballistic and cruise missile threat" study (NDIA)

Some feasible, near term modifications to convert a Scarab into an LACM include:
• Deletion of reconnaissance payload
• Deletion of UAV recovery system
• Replacing the existing guidance and control subsystem with an integrated inertial guidance/GPS subsystem
• Addition of an explosive warhead or Chem/Bio payload and dispenser.
And, if greater terminal precision is required:
• Addition if an accurate terminal guidance system (some type of terrain/target matching system based on available radar or electro-optic sensor)

There are a number of additional design modifications that a country could make to the Scarab UAV to increase its performance (range and payload) capabilities for the land-attack role. They include:
• Increasing the fuselage length to accommodate a larger payload
• Increasing the fuselage/tankage lengths to accommodate a greater fuel loading
• Replacing the existing Teledyne CAE 373-8C turbojet engine with a more fuel efficient low- altitude sustainer engine
• Reduce the vehicle’s RCS in the land-attack role by shaping critical surfaces or adding
radar absorbing materials (RAM)
• Employing a TERCOM type terminal guidance system