The Almaz Space Station Program

Sven Grahn

Origins of the Almaz concept

The military space station project Almaz was conceived in 1964 by Vladimir Chelomey's "firm" (currently NPO Mashinostroyeniya [Machine Building Scientific Production Association]) in the Moscow suburb Reutov. It was indeed a grandiose concept that impresses even today. A twenty ton spacecraft (OPS) was to have operated for a couple of years to provide photographic and radar reconnaissance images. A special supply transport spacecraft, the TKS would arrive at the spacecraft with cargo and cosmonauts. Its reusable crew capsules were intended to be reusable up to ten times. Almaz, as originally conceived can be seen in the sketch on the right.

The plan for launching cosmonauts to the station changed during the conception of Almaz. The original concept indeed included the transport craft (TKS), but for a brief period in 1966-67 a variant of the Soyuz would have been the ferry to bring cosmonauts station (5). Instead Chelomey proposed to let cosmonauts go into space directly with the station by adding a large return capsule to the station. each station would be discarded after the return of the crew. Later, the TKS would be used to resupply the station with crews. As it turned out, delays in developing the TKS, led to the decision in 1970 to use a version of the Soyuz 7K-T ferry to deliver crews to Almaz. This was seen as an interim stage until the TKS would be ready.

(The design of TKS and the history of its flight will be the subject of a separate article under preparation. However, an description of how the Kettering Group tracked the TKS flights can be found in two articles: "Radio Observations of TKS and Related Flights", and "Tracking satellites with a solar radiospectrograph")

The Almaz program was approved in 1967. However, Chelomey regarded the first launch date in 1970 (on Lenin's 100th birthday) given in the approval decree as unrealistic and argued that development would require much longer time. In 1969 the requirement for a prompt "reply" to Apollo prompted the Soviet leadership to give the Korolev Design Bureau (nowadays Energiya NPO [Scientific Production Association]) the task of launching a space station (17K [DOS]) using some elements from the Almaz design. Chelomey was ordered to transfer Almaz drawings to Korolev's Design Bureau. By 1970 eight ground test articles and two flight-rated Almaz (OPS) "spaceframes" were manufactured by Chelomey's Khrunichev Plant. However, by the order of MOM these frameworks were passed to Korolev's Design bureau for implementation of their 17K (DOS) project. In addition, Chelomey was directed to use Korolev's 7K (Soyuz) spaceships instead of TKS during flight testing of OPS. The stations developed by Korolev's bureau based on Almaz used subsystems derived from Korolev's Soyuz spacecraft and flew first in space starting in 1971 under the name Salyut-1.

The transfer of know-how to Korolev's bureau delayed the Almaz program for two years. Howeveer, this was at the height of the arms race and the Salyut design of Korolev's design bureau did not have the reconnaisance capabilities of the Almaz concept. Russian journalists have written (1) that the Central Committe were taken in by Almaz' as a "space fortress" which was seen as "a response to Chamberlain" (2). So the Almaz project continued. The amazing situation developed: Two Soviet manned station programs were running at the same time. This confounded Western observers - and indeed myself and the members of the Kettering group of satellite radio trackers (see separate article)

That Almaz was seen indeed a military spacecraft - a "fortress in space" can be inferred from the persistent reports that these stations were equipped with weapons:

"Almaz was protected against interceptor and tow satellites, been developed back then in the USA. OPS [Orbital Piloted Station] was equipped with high speed aviation 23 mm cannon by A.Nudelmann KB. The gun was pointed to the target by revolving the whole station. This weapon proved to work in space environment. In one of flights, just before the braking impulse to the station, flying automatically, the gun ammo was shot out. The cannon fired accurately, and all the constructions appeared reliable and rigid. " (3)

"I was told by a friend, that he was told by cosmonaut Popovich (commander of Soyuz 14 aboard Salyut 3) that the cannon did exist on his flight, but very fortunately he was not forced to use it. Obviously, the cannon was not present aboard Salyut 5. In N. Kidger: Almaz - A Diamond out of Darkness, Spaceflight, March 1994, pp. 86 - 89, cosmonaut Lisun (back-up flight engineer for Salyut 5) is cited definitely denying the existence of such a cannon aboard the Almaz stations in space. " (4)

Almaz design features

Dimensions and mass

The basic space station block was shaped like a cylinder with two two different diameters, 4.15 m and 2.9 m. Its total length was about 11 meters. (See sketch above (10)). Its mass was about 15 tons. In the original version, foreseen to be launched after the initial stations, the Return Apparatus (VA) re-entry vehicle would be connected to the smaller diameter section of the station. A docking unit was mounted at the rear of the station along the axis of the station. The docking unit was connected to an airlock for extra-vehicular activity and for ejecting the so-called Information Return Capsule (KSI).

Power and propulsion

Two solar panels were mounted at the rear of station generating 3.1 kW, having a span of 23 meters and an area of 52 square meters. At the rear of the station there were two orbit correction engines with a thrust of about 4000 N each. These engines were mounted on each side of the docking unit. (See an aft view of the docking unit and orbit correction engines).

The Information return capsule

The Information return capsule (KSI) could return film from the main reconnaissance camera (Agat-1). The capsule had a mass of about 360 kg and a diameter of 0.85 m. After ejection from the space station it was spun up by a small solid rocket motor. Then the main retro rocket fired and after burnout another small solid rocket fired to de-spin the capsule. The rocket motor pack was jettisoned before reentry. Before landing the drogue cute pulled the capsule out of the heat shield. An airbag was inflated to cushion the landing.

The Agat-1 reconnaissance camera and its radio link

A colossal telescope, the Agat-1, approximately one meter in diameter and with a focal length of 6.4 meters, was mounted in the station's "floor". The crew could photograph targets such as airfields and missile complexes using the telescope. An optical sight permitted them to "come to a standstill" over a facility. Furthermore, there was a device for taking pictures in the near infrared range and a topographical camera. The film frames were quite large, 50 x 50 cm and according to U.S. estimates would have had a resolution of less than 50 cm. We can check this estimate of the capability of the camera by assuming that the film used was as good as that used by early version of the the U.S. CORONA satellite,. i.e. the film was capable of resolving 100 line pairs per millimeter (8).

The formula below is a very simple relationship between orbital altitude (h), ground resolution (r), focal length (f), and film resolution (p).

p/f=r/h or r= h × p/f

For Almaz h = 270 000 m and f = 6.3 m. So, let us assume that the film used in the Agat-1 camera had the same resolution as the used in early CORONA flights, i.e. 100 line pairs per millimeter. This means that two dark lines 1/100 mm apart with a lighter area in between can be resolved by the film if properly exposed and if proper ground motion compensation was implemented. The film resolution p can the be written: p = (1/1000) × (1/100) and the ground resolution becomes:

r = (270000/(100000 × 6.3)) = 27/63 = 3/7 = 0.43 m

Later CORONA flights had a resolution of 160 line pairs per millimeter, which would have corresponded to a ground resolution of 0.27 m..

The minimum aperture diameter (D) required to satisfy the diffraction limit criterion for the Agat-1 telescope can be estimated by the following formula:

D = 1.22 × L × f/p

where L is the average wavelength of the film sensitivity, here assumed to 0.5 micrometer.

D = 1.22 ×0.5 × 10-6 × 6.3 × 105 = 0.4 m

We know that the aperture diameter was five times large about 2 meters, which was probably dictated by the required signal to noise ratio and the chosen exposure time.

Data from this reconnaissance payload on Almaz could be returned not only via the KSI, but also through a radio link to the ground. It seems that film from the reconnaissance cameras would be developed on board, scanned and transmitted to the ground - all within 30 minutes (5). Considering the secret nature of the Almaz program and the Soviet obsession with secrecy the downlink for the reconnaissance pictures the downlink must have been designed to be secure. In addition to encryption it seems natural that some kind of directional antenna would have been used. When I looked through pictures of Almaz that I had downloaded to my computer I kept an eye out for such an antenna. I think I have been able to identify a good candidate for the antenna system of the secure data link called "Avrora"(5).

The picture on the right shows two independent views of the Almaz base block and there is a small dish antenna, with a diameter of about 0.7 meters, near the rear part of the 4.15 m cylindrical section. If the frequency 10 GHz was used the beamwidth of this antenna would have been about 3 degrees, which would have resulted in a coverage are on the ground of about 15 × 30 km at 30 degrees elevation. Clearly, this was a small enough area to avoid eavesdropping. However, the dish antenna had to be steered to point at the ground station.



Radio systems

As described elsewhere the Kettering Group was ale to distinguish between Almaz and DOS stations by observing radio signals from the various flights in the Salyut program. Just like the DOS station's developed by "OKB-1" Almaz had a short-wave telemetry transmitter, called "support" telemetry by the Russians (see below). Just like DOS Almaz had a VHF transmitter for the main telemetry system. However, the command uplink and command verification downlink systems were completely different. DOS used the command system on Soyuz, similar to the "Kvant" system nowadays used on the ISS (Zvezda), while Almaz probably used the Komparus system used by military spacecraft and also the FGB (Zarya) on the ISS. The FM voice downlink turned out to be different for the two stations, but frequencies used were among those used for Russian manned spaceflight over four decades. The table below summarizes the frequencies used by Almaz (OPS) and DOS.

Function OPS (Almaz) DOS Support telemetry 19.944 MHz (FSK-PDM)

19.992 MHz (?) 15.008 MHz (CW-PDM) (Sal. 1,4,6,7)

20.008 MHz (CW-PDM) (Sal. 1,4,6,7) Main telemetry 181.0/180.0 MHz (PPM-AM) 192.0 MHz (PPM-AM) (Sal. 4,6,7)

166.0 MHz (PPM-AM) (Sal. 7) Main voice link 143.625 MHz 121.75 MHz Salyut 4,6

142.417 MHz Salyut 7 Command system 2365-2375 MHz down?

7190-7210 MHz up? 922.754 MHz down

768.96 MHz up Radar transponder ? 2802 - 2860 MHz down

2725 MHz up

The 180 MHz telemetry antennas can easily be located on the Almaz base block. Four folded dipoles are located on the VA capsule adapter section at the front of the station as shown in the picture on the right side of the table. The shortwave "support" telemetry antennas can be found on the cone connection the main 4.15 m diameter cylinder and the smaller diameter section of the station.



Scaled back Almaz for flight testing

To be able to test Almaz without either the TKS or the VA ready, the Almaz base block was launched without the VA and the Soyuz ferry was used to transfer cosmonauts to the station. The scaled-back Almaz probably did not carry the side-looking radar of the full-scale station, even though strange white wedges on the smaller diameter part of the base block resemble antenna structures (see below). This scaled-back version of the station was launched three times; OPS-1, No. 101 as Salyut-2 on 3 April 1973, OPS-2, No. 101-2 as Salyut-3 on 24 June 1974 Jun 24, and OPS-3 No. 103 as Salyut-5 on 22 June 1976. In 1978 flight testing of OPS was completed and the Ministry of Defense decided not to accept it for operational service (as inferior to automatic reconnaissance satellites).

The first launch of Almaz - Salyut-2

The first Almaz that was launched was called Salyut-2 was launched into orbit at 0900 UT on 3 April 1973. It maneuverd to an orbit with a 63-rev repeating apttern within five days of the launch. Clearly, the orbit established at 89.8 minutes was stable enough to let the space station wait in orbit until the Soyuz was ready to launch. The Soyuz craft to be used for ferrying cosmonauts to the station was still undergoing parachute tests and the sattion had been launched so that it would be in the right position to received a crew about a month after launch (5). While the crew was preparing to launch to it a disaster occurred at some time between 0930 UT on 14 April and 0016 UT on 15 April, when the station was out of line-of-sight touch with Soviet ground stations. According to (5) there was no main telemetry (presumably the 181 MHz link, see below) from the station when it appeared over Ussuriysk at 0016 UT on 15 April and "support" telemetry (presumably the 19.944 MHz shortwave transmitter, see below) indicated that the pressure had dropped to half inside the station. Soviet tracking data also showed a slight increase in the orbital period. In the figure "Salyut-2 maneuvers below" there is a slight increase in the period on day 105 and the rate of decay suddenly increased, indicating that the spacecraft had started to tumble instead of being oriented "nose first". Reports in Western media indicated the station tumbled at a rate of 30 rpm.(6)

The offcial reason for the failure seems to put the blame on the propulsion system causing the rupture of the hull, even though the explanation provided is somewhat difficult to interpret. It seems to indicate a "stuck thruster" (5): "...led to a continuous working of the low-thrust stabilization engines and significantly increased its temperature, that caused overheating..." This explanation is also cited by a a Western source at the time (6). Another theory advanced by engineers in Chelomey's organisation was that a fragment of the exploded Proton's third stage penetrated the skin of the space station.

If one examines the first twenty days in orbit one can see that maneuvers ceased after day 105, i.e. 15 April. The station decayed from orbit on 28 May 1973.

Phillip Clark has developed a method for predicting "landing windows" from early Salyut stations (11). The method uses the number of hours before local sunset at the landing point that the northbound equator crossing that put the spacecraft nearest the landing zone occurs. The diagram below uses data from Soyuz 14 and 24 because these missions flew the entire planned duration. A "landing window" for descent from the station opened around day 143, i.e. 23 May, when the equator crossing occurred about 3.8 hours before local sunset in the recovery zone. (this calculation assumes an orbit with the decay rate that Salyut-2 had before the catastrophe on 14 April). So a if 14-day flight had been planned would have meant a launch around 7-9 May. It seems that the flight was actually planned for 8 May (5).

The first succesful Almaz - Salyut-3

Salyut-3, another Almaz (OPS No 0102), was launched into space from launch site 81L at Baikonur at 2238 UT on 24 June 1974. The picture on the right shows Salyut-3 in the checkout shop (at Baikonur?) (9). Interestingly it is labeled "Salyut" at the base. As can be seen in the graph of nodal period as a function of date for Salyut-3 during 1974 the Soyuz-14 ferry with cosmonauts Popovich and Artyukhin was launched when the space station had set up on orbit that almost exactly repeated every four days. In this way, launch opportunities to rendezvous and dock withn the station occured every four days. It took the station 9 days to reach this orbital altitude.

An additional factor important for launching a ferry to Almaz was the equator crossing longitude for the space station revolution passing nearest the launch site. If a direct ascent (within a few revolutions) is made to the space station, the longitude of the station equator crossing should be very close to that of a Soyuz launched form Baikonur. Soyuz ferries to early space stations used about one day to reach the station. The altitude of the ferry would be gradually raised to coincide with that of the station. The higher up the station is the larger is the average is the difference in orbital altutde during the rendezvous phase between the ferry and the station. Thus, to reach the station after 24 hours, the initial phase difference along the orbit between the ferry and the station need to be larger the higher up the station is. But to let the orbital planes coincide at launch the equator crossing longitude of the station at the revolution passing closest to the launch site on the day of the launch of the ferry needs to be further east the higher the station is. In that way the proper orbital phasing is achieved when the station's orbital plane drifts westward until the time the ferry is launched. A graph showing this relationship can be seen in a separate article.

Thus, when Soyuz-14 was launched at 1851:08 UT on 3 July 1974 (Day nr: 184), the equator crossing for the Salyut-3 station was 345.15 degrees west. The crew came down on 19 July 1974 (Day nr: 200) which was according to plan if one considers the "landing window" criterion developed by Phillip Clark. Thus, the first visit on board Almaz lasted 14 days. Radio tracking efforts by the Kettering Group during the flight of Soyuz-14 is covered in a special article at this web site.

Soyuz-15 was launched at 1958:08 UT on 26 August 1974 (Day nr: 238). The orbital period of the space station had again been brought up close to the period which yields a ground track that repeats every 63 revolutions, i.e. every four days (see figure showing the "orbital history" below). The Soyuz failed to dock with Salyut-3 and was recovered on 28 August 1974 (Day nr: 240). The IGLA system malfunctioned and the two craft missed each other by a mere 7 meters on the first attempt and 30-50 meters on the second. If one applies the same "landing window" analysis as for Salyut-2 it seems that the flight could have ended around day 261 (18 Sept 1974) which would have meant a 20-21 day stay on Salyut-3. Indeed, in (5) Soviet sources are quoted as indicating that a 25-day flight was planned.

In the figure below the time when the film capsule (KSI) was ejected from Salyut-3 (19 September). It turns out that the recovery of the KSI also satisfies Phillip Clarke's "landing window" criterion. In the diagram below the maneuver to a 63-rev repeating pattern has been indictaed. This could have been in anticipation of another Soyuz launch attempt, but it was probably done to keep the station from decaying and to permit further testst in the unmmaned mode. Salyut-3 was de-orbited intentionally over the Pacific on 24 January 1975. The first Almaz mission was over.

The final Almaz station - Salyut-5

Salyut-5 was launched at 1804 UT on 22 June 1976. It quickly maneuvered to the 63-rev repeating pattern orbit of its predecessor Salyut-3. In a similar fashion a ferry with cosmonauts, Soyuz-21, was launched as soon as that orbit was reached. So, Soyuz-21 was launched on 1208:45 UT on 6 July 1976 (Day nr: 188). By again using the "landing windows" analysis developed by Phillip Clark it seems that landing was planned around day 245, i.e. 1 September 1976. The flight actually ended on day 237, i.e. 24 August 1976 when the Boris Volynov and Vitali Zholobov touched down at 1832:17 UT. There have been reports (12) that the flight ended early due to crew psychological problems ("interpersonal issues"), but transcripts of the voice signals from the station show no such signs. Indeed, the flight seems to have ended a little early, and perhaps crew status could have been a factor in this decision. Absence of evidence is not the same as evidence of absence! Other sources (11) have indicated that the cabin atmosphere was contaminated.

Soyuz-23 launched at 1738:18 UT on 14 October 1976 (Day nr: 288) with V Zudov and V Rozdestvensky was launched. This was at a time when Salyut-5 was in an orbit whose ground track repeated every 9 days (142 revs)! The docking failed and the crew landed at1745:13 UT on 16 October 1976 (Day nr 290). Clark writes (11) that a flight duration of 17-24 days is possible based on "landing window" analysis.

Regular telemetry from the Salyut-5 space station on 180 MHz resumed on 2 February 2, 1977 indicating that a Soyuz launch might be imminent. Soyuz-24 was launched at 1611:50 UT on 7 February 1977 (Day nr: 38). The crew (Viktor Gorbatko and Yuri Glazkov) was supposed to have been wearing breathing masks upon entry into the station (11). This could be an indication that the reports about a foul cabin atmosphere were true. However, the flight proceeded for 18 days and ended at 0936 UT on 25 February 1977(Day nr: 56 ).

The film return capsule (KSI) from Salyut-5 was recovered on 26 February 1977, directly after the return of the Soyuz 24 crew. Salyut-5, the last Almaz space station, burned up in the Earth's atmosphere on August 8, 1977 as can be seen in the graph below where the orbital period plunges towards oblivion requiring only a small rocket nudge to bring it do de-orbit.





References