Ракета-носитель Titan IIIB: Модификации и запуски.

Titan IIIB was the collective name for a number of derivatives of the Titan II ICBM and Titan III launch vehicle, modified by the addition of an Agena upper stage. It consisted of four separate rockets. The Titan 23B was a basic Titan II with an Agena upper stage, and the Titan 24B was the same concept, but using the slightly enlarged Titan IIIM rocket as the base. The Titan 33B was a Titan 23B with the Agena (which had a smaller diameter than the Titan) enclosed in an enlarged fairing, in order to allow larger payloads to be launched. The final member of the Titan IIIB family was the Titan 34B which was a Titan 24B with the larger fairing used on the Titan 33B.

Part of the Titan rocket family, the Titan 23B space launch vehicle was a three stage liquid fueled booster, designed to provide a small to medium weight class capability. It was able to lift approximately into a polar low Earth circular orbit. The first stage consisted of a ground ignited Aerojet LR 87 liquid propellant rocket, while the second stage consisted of an LR91 liquid propellant rocket. The third stage was an Agena D XLR81 BA 9 liquid propellant rocket. Various models of this Titan/Agena D rocket were called, "Titan 23B", "Titan 24B", "Titan 33B" and "Titan 34B".

Titan 23B used the basic Titan 3A core (including its Transtage) with an Agena D upper stage, though without the all inertial guidance system, malfunction detection equipment, and redundant systems required for man rating the 3A. The Titan 23B was launched from SLC 4W at Vandenberg AFB, Calif. Its main payload was the GAMBIT (KH 8 reconnaissance) satellites, in 9 flights from 1969 through 1971.

The Titan 24B differed from the Titan 23B in that the Titan IIIM core with extended propellant tanks was used in place of the original Titan II core. The payload remained attached to the Agena stage. 23 flights took place from 1971 to 1984, with two failures.

The Titan 33B was a Titan 23B with the entire Agena and payload completely enclosed in a shroud. It flew only three times (1971–73) with one failure and was used to launch Jumpseat satellites.

The Titan 34B was a Titan 24B, modified by the addition of the larger fairing used on the Titan 33B. 23 were launched in 1971–87 with two failures. All launches consisted of KH 8 satellites.

Titan IIIB rockets suffered four outright failures, and two partial failures. The first failure occurred on 26 April 1967 during the launch of a Gambit 3 satellite when the second stage suffered a sudden thrust decay which left it unable to achieve orbital velocity, sending the Agena and GAMBIT into the Pacific Ocean some 400 miles (644 km) downrange. It was not possible to determine the cause of the malfunction with certainty, but a fuel line obstruction was believed to be the most likely explanation. Martin Marietta had no answers except to suggest implementing better quality control measures during assembly of the Titan vehicles. The next launch, on 20 June 1967 was a partial failure; due to a problem with the protective skirt on the second stage, a lower than planned orbit was achieved. On 24 October 1969 OPS 8455 was placed into a higher than planned orbit by another 23B due to an engine failing to cut off after completing its planned burn, however the payload was able to correct its own orbit. On 16 February 1972, a Titan 33B failed to achieve orbit carrying a Jumpseat satellite. Another failure occurred later the same year, when on 20 May a Titan 24B malfunctioned during the launch of KH 8 #35. The Agena suffered a failure of a pneumatic regulator during ascent and reentered the atmosphere. Although it had been assumed debris would land near South Africa, pieces turned up in faraway Great Britain a few months later. The launch of KH 8 #39 on 26 June 1973 also failed to orbit when the Agena had a fuel valve failure, preventing engine start. A launch of a Jumpseat satellite on 24 April 1981 was a partial failure when the Agena failed to separate.