June 1980:letters

Sir, I have just read David Shayler’s Space Report item "NASA calls for Group 9 Astronauts” in which he writes: "The latest group of 35 astronauts selected in January 1978 are well advanced with their two-year training programme, which is due to be completed in July 1980.”

In fact, NASA announced on 31 August 1979 that the 35 had completed their training and were now eligible for selection as Space Shuttle crew members. The original two-year training programme had been cut in half. George W.Abbey, Director of Flight Operations at the Johnson Space Center, commented: "We are pleased with the newest group of astronauts’ performance and their adaptation to the Space Shuttle programme” and added that the Astronaut Corps now numbers 62, men and women, and that future astronaut candidate training will also be held to one year.

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In linking the reported failure of a Proton launch vehicle on 4 August 1977 with Cosmos 929, Nicholas Johnson has fallen into the trap of drawing a conclusion from too little information. There is more to an orbit than apogee, perigee and inclination. When two spacecraft are required to rendezvous without unnecessarily high fuel expenditure, they must both be orbiting in the same plane and in such a way that at the desired time they are at roughly the same location in space.

For example, manned Soyuz flights to Salyut space stations require the Soyuz orbit to be in the same plane as that of Salyut. After the normal Soyuz systems check, the initial low orbit is changed to one with its apogee at the same height as Salyut’s circular orbit. Choice of a suitable separation between the two craft at launch ensures that when Soyuz is at apogee on rev 17, it is close to Salyut. A firing of the Soyuz engine ensures that it enters the circular orbit alongside Salyut. It was the failure of this last manoeuvre to be completed by Soyuz 33 that forced cancellation of its docking with Salyut 6, as each successive return to apogee of the Soyuz increased the separation between the two vehicles by about 120 km.

A similar flight profile would be followed by an object launched to rendezvous with Cosmos 929, launch of the second vehicle occurring as the plane of the target’s orbit passed Tyuratam, due to the rotation of the Earth. On 4 August, Cosmos 929 itself was still in a relatively low orbit so very little separation would be required between it and a chasing vehicle. Launch for rendezvous therefore would take place on an orbit when Cosmos 929 crossed the equator,northbound, at a longitude of approximately 146 degrees west. In the case of Salyut in a 91.4 minute orbit, the Soyuz launch takes place when Salyut’s equator crossing is about 141 degrees west, the orbit plane passes Tyuratam about 25 minutes later when the Soyuz lifts off. The difference in time between Soyuz and Salyut is then reduced over the next 24 hours by virtue of Soyuz’ lower orbit.

If a rendezvous had been attempted about 4 August, the best date would have been 7 August in the very early hours of the morning (UT). Cosmos 929 crossed the equator at 146 degrees west at 2351 UT on 6 August, and lift off of a second craft would have occurred a few minutes after midnight.

I agree with the analysis of the Cosmos flights as elements of a programme leading to the construction of units larger than Salyut, but I do not feel that such a feat was planned for 1977. Cosmos 929, Cosmos 1001 and Cosmos 1074 may all represent steps along the road. If Cosmos 929 was the failure suggested by Nicholas Johnson I think we would have seen the attempt repeated before now.