LONG MARCH 2 (CZ-2)
The Long March 2 was introduced with the recoverable satellite program (Chapter 4) and three versions are still in service:
1. Long March 2C, which introduced the FSW recoverable satelhte program in 1975;
2. Long March 2D, which introduced heavier, recoverable FSW satelhtes from 1992;
3. Long March 2F, used for Shenzhou and the Tiangong, also called Shenjian.
In addition, a heavy version, the Long March 2E, was used for Western communications satelhtes over 1990-95 (see Chapter 5). It flew seven times (with two failures) and is discontinued.
The Long March 2A made one flight in November 1974, the first attempt to put a recoverable satelhte into orbit. When it failed, the rocket was redesigned and called the Long March 2C. The Long March 2B was a canceled design for a version to carry a small payload to 24-hr orbit. The original role of the Long March 2C was to put recoverable satelhtes into orbit, the FSW series (see Chapter 4). As such, it put 14 satelhtes into orbit over 1975-93, all successfully (one was not recovered, but that was not the fault of the launcher). During a typical mission, the Long March 2C rocket begins to pitch over into its flight trajectory 10 sec after lift-off. Staging takes
Tractors pull the CZ-2C down to the pad – quite different from Soviet rail practice.
place at exactly 2 min: it is a hot staging, with explosive bolts detonating the now – expired first stage, which falls away a second later. Twenty explosive bolts fire to separate and release the fairing over the payload at 230 sec, the second-stage engine completes its burn, and the payload is released at 569 sec. Telemetry relays back as many as 300 different parameters during launch.
The Long March 2C series might have ended in 1993 had it not been for the American Motorola company, which booked the Long March 2C for 11 double launches of its Iridium global telecommunications satellite (22 satellites altogether). The 2C was adapted with a longer second stage (2 m longer) and what is called a “smart dispenser” (SD), designed to spring the small comsats into orbit. The Taiyuan site was used for these flights, which flew into a new, higher orbit of 700 km at 58°E. This launcher is referred to as the Long March 2C-SD. A test of the SD was made on 1st September 1997, following which seven successful launches took place before Iridium filed for bankruptcy. A further refinement, the CTS was used for the Chinese-European Doublestar project in 2003. The launcher continued to operate for some time, experiencing a rare failure on 18th August 2011 when attempting to put into orbit Shi Jian 11-4. It transpired that the connection between the servomechanism and the second-stage vernier engine §3 failed during the later stages of the ascent.
The Long March 2D was introduced in 1992 to carry the heavier, third generation of FSW recoverable spacecraft, the FSW 2. The payload of the Long March 2D was 600 kg more, at 3,400 kg. The launcher was heavier (237 tonnes), with improved performance in a number of areas. With FSW 3-1 in 2003, a stretched version with fins was introduced, sometimes called the 2D2, and it used the new manned launch pad.
For China’s manned spaceflight, the Long March 2 was adapted and upgraded. Fifty-five engineering changes were made to make it capable of manned flight. President Jiang Zemin bestowed on it his own name, the Shenjian, or “magic arrow”, in 2002, though this is rarely used. The principal difference – and most obvious visual change – was the addition of an escape tower based on the Russian design for the Soyuz spacecraft. In the event of a mishap either on the pad or in the first 160 sec of flight, the tower fires, pulling Shenzhou rapidly high and clear of the rogue rocket. Once the thrust is exhausted (after only a few seconds), the cabin drops out of the bottom of the tower. This is a tricky maneuver, for the three Shenzhou modules must then separate very quickly, giving the descent cabin time to get free, deploy its parachute, and fill it with air. Four retardant panels are deployed on the tower to slow its fall and avert the danger of its tangling with the cabin. All this must be done in seconds. Assuming all goes well, the normal trajectory of ascent to orbit is 586 sec, at which point mission control in Beijing assumes control. The tower is jettisoned at
130 sec, the strap-ons at 160 sec, the fairing at 200 sec. For the Tiangong, the 2F was adapted to carry 8.7 tonnes, requiring a new launch shroud, but without the escape tower and numerous less-visible modifications. Details of the CZ-2 are given in Table 3.4.