Directory of U.S. Military Rockets and Missiles
Appendix 4: Undesignated Vehicles
Copyright © 2004 Andreas Parsch

Republic SD-4 Swallow

The SD-4 Swallow supersonic reconnaissance drone was built in 1960 under a U.S. Army contract. The SD-4, which was to be part of the AN/USD-4 surveillance drone system, was a delta-wing design powered by a single Pratt & Whitney JT12A-3 turbojet. The Swallow was zero-length launched with the help of two solid-fueled rocket boosters, and could be recovered by parachute. Similar to Republic's earlier SD-3 Snooper drone, it had interchangeable nose sections for photographic, radar or infrared surveillance equipment.

Photo: Republic

The AN/USD-4 program was cancelled by the U.S. Army in January 1961, and it is not clear whether any SD-4 vehicles were actually test-flown.


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for SD-4:

Length9.27 m (30 ft 5 in)
Wingspan3.51 m (11 ft 6 in)
Weight1590 kg (3500 lb)
SpeedMach 1.5
Ceiling18300 m (60000 ft)
Range480 km (300 miles)
PropulsionPratt & Whitney JT12A-3 turbojet; 12.9 kN (2900 lb)

Main Sources

[1] Joshua Stoff: "The Thunder Factory", Motorbooks Intl., 1990
[2] Norman J. Bowman: "The Handbook of Rockets and Guided Missiles", Perastadion Press, 1963
[3] Frederick I. Ordway III, Ronald C. Wakeford: "International Missile and Spacecraft Guide", McGraw-Hill, 1960

Back to Directory of U.S. Military Rockets and Missiles, Appendix 4

Last Updated: 5 May 2004