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Mir Hardware Heritage {|cellspacing=10 cellpadding="15" width="100%" border="0"
 * width="33.3%" align="left" rowspan="1" colspan="1"|The repeated failure of the N-1 rocket administered the coup degrace, however. The first N-1 test flight occurred on February 20, 1969. It ended in first stage failure. First stage malfunctions also ended the second (July 3, 1969), third (June 27, 1971), and fourth (November 23, 1972) N-1 test flights. A fifth N-1 test was scheduled for August 1974, and a sixth for late 1974. In May 1974, the August test was postponed, though research funding for the N-1 continued. The N-1 program was finally cancelled in February 1976.

1.2.5 Salyut 1 (1970-1971)
The Original Soyuz survived the Moon program to become the ancestor of all subsequent Soyuz and Soyuz-derived craft. Spacecraft designer Konstantin Feoktistov stated that the Original Soyuz missions in 1966-1970 provided engineering data for its conversion into a space station transport. Plans for the conversion were drawn up in the first half of 1970.

Soyuz 10 and Soyuz 11 carried docking systems permitting internal crew transfer. In this work these vehicles are called the Salyut 1-type Soyuz. Apart from their docking systems, they differed only slightly from the Original Soyuz. The three Soyuz 10 cosmonauts became the first people to dock with a space station, but were unable to enter Salyut 1. This was blamed on a “weak” docking unit. The Soyuz 11 crew occupied Salyut 1 in June 1971. Because Soyuz cosmonauts wore pressure suits only for EVAs, the Soyuz 11 crew perished during reentry when pyro shock jarred open a 1-mm pressure equalization valve, allowing the Soyuz 11 descent module to vent its atmosphere into space.
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1.2.6 Early Soyuz Ferry (1973-1977)
The Soyuz spacecraft underwent further redesign in the aftermath of the Soyuz 11 accident. Putting the cosmonauts in pressure suits during “dynamic operations” (such as liftoff, docking, reentry, and landing) forced Soviet engineers to pull one crew couch. The solar arrays were replaced by chemical batteries to save weight, restricting Soyuz to 2 days of autonomous flight. Removing the arrays also improved the spacecraft’s maneuverability. In addition, the Soviets modified the Soyuz orbital module to improve its ability to carry cargo to Salyut stations. These modifications produced the Soyuz Ferry.

1.2.7 Apollo-Soyuz Test Project (1973-1976)
The Apollo-Soyuz Test Project (ASTP) sprang directly from letters exchanged between NASA Administrator Thomas O. Paine and Soviet Academy of Sciences President Mstislav Keldysh in 1969 and 1970. (Of course, U.S.-Soviet space cooperation dates from nearly the beginning of spaceflight—see Portree, David S. F., “Thirty Years Together: A Chronology of U.S.- Soviet Cooperation”, NASA Contractor Report 185707, February 1993.) Several proposals for a joint manned mission were floated. For a time, an Apollo CSM docking with a Salyut space station held center stage. In April 1972, the sides met in Moscow to finalize the agreement for an Apollo-Salyut docking. The Soviets surprised the Americans by announcing that modifying a Salyut to include a second docking port for Apollo was neither technically nor economically feasible. They offered a Soyuz docking with Apollo instead. The Soyuz Ferry needed substantial modifications to fulfill its new role as international ambassador. These included restoration of solar arrays to permit a 5-day stay in orbit, deletion of the Igla (“needle”) approach system boom and transponders, addition of Apollo-compatible ranging and communications gear, and substitution of the Soyuz Ferry probe and drogue docking system with the APAS-75 (androgynous peripheral assembly system) (see figure 1-22). The Soviet Union built five ASTP Soyuz. Three flew as precursors (two unmanned and one manned), and one backed up the prime ASTP Soyuz, Soyuz 19. In the event, Soyuz 19 performed well. Its backup flew as Soyuz 22 on an Earth observation mission (1976). It was the last manned Soyuz flown without the intention of docking with a space station.
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1.2.8 Progress and Soyuz (1977-Present)
Since 1977, Soyuz and its derivatives linked with the manned space program have had one function—to support manned space stations. Since the launch of Salyut 6 in 1977, the Soviet/Russian station programs have had the following attributes with implications for Soyuz evolution:


 * Multiple docking ports
 * Design lifetimes of more than 1 year, with the option to remain in orbit for several years through onorbit repairs, upgrades, and refurbishment
 * Extended-duration stays by teams of two or three cosmonauts

Extended-duration stays called for resupply, which in turn called for a specialized resupply spacecraft. This drove development of the Progress freighter, design of which began in 1973—the same year work began on
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