Directory of U.S. Military Rockets and Missiles
Appendix 3: Space Vehicles
SSB-9
SSB-8
SSB-10
Copyright © 2003 Jos Heyman
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McDonnell Douglas SSB-9 PAM-D2

The Payload Assist Module (PAM) upper stage was developed by McDonnell Douglas as a higher altitude booster of satellites deployed in near Earth orbit but operationally destined for higher altitudes. It was initially known as the Spinning Solid Upper Stage (SSUS). It was initially intended to develop a PAM-A version for Atlas class payloads, and a PAM-D for Delta class payloads, however, the PAM-A never materialised.

Photo: Author's collection
PAM-D (launch with Anik C-1)


Stage Length Diameter Engine Fuel Thrust
12.28 m1.20 m1 Thiokol Star 48solid 58,000 N

Specifications for PAM-D


The PAM-D version was used with various Delta vehicles as well as with the Space Shuttle. The PAM-D had a capacity for 1250 kg.

Stage Length Diameter Engine Fuel Thrust
11.80 m1.60 m1 Thiokol Star 63Fsolid 107,200 N

Specifications for PAM-D2


The PAM-D2 was an improved version used with the Space Shuttle and the Titan II launch vehicles. It could handle satellites with a mass of up to 1890 kg. The version was also known by its military designation SSB-9A although this designation was probably restricted to military launches.

Between 15 November 1980 and 20 March 1987 there were 14 satellites that were placed into a geostationary orbit by a PAM-D upper stage. The launch vehicles used for these flights were of the Delta 3910 or Delta 3920, ie the PAM-D was not considered part of the launch vehicle. The same applied to the only use of a PAM-D with a Titan 3 launch vehicle, which took place on 1 January 1990. In addition, the PAM-D is also part (the third stage) of Delta 4925, Delta 6925, Delta 7025, Delta 7425 and Delta 7925 launch vehicles. Up to 31 December 2002 69 of these vehicles had been launched.

There was also a PAM-S version of the PAM-D which was used exclusively for the launch on 6 October 1990 of the Ulysses interplanetary spacecraft in combination with an IUS upper stage.

Stage Length Diameter Engine Fuel Thrust
12.00 m1.20 m1 Thiokol Star 48Bsolid 58,000 N

Specifications for PAM-S


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Last Updated: 17 March 2003