September-December 1980:the Polyot satellites

In November 1963 and April 1964 the Soviet Union launched the two spacecraft in the Polyot programme. The two satellites tested a spacecraft manoeuvring system, although the subsequent use of the technology has not been identified with certainty. This article will review the known information about the Polyot craft and look at the various suggestions which have been made for the follow-on operational flights of the Polyot system.

Launch Announcements

Polyot 1 was launched on 1 November, 1963 and the Pravda article covering the launch said that space vehicles “were being developed in the Soviet Union which can be manoeuvred widely in all directions during orbital flights.” It would be impossible to give the full launch announcement here, but some extracts are given below:

(1) "Polyot 1 is equipped with special apparatus and a system of auxiliary motors which ensure that it is kept stable and enable it to be highly manoeuvrable in circumterrestrial space.”

(2) “The space vehicle has been put into an initial orbit having an apogee height of 592 km and a perigee height of 339 km.”

(3) "Polyot 1 has performed important lateral manoeuvres, varying the plane of the orbit, as well as manoeuvres in height, and has entered a final orbit having an inclination to the plane of the equator of 58° 55', with an apogee of 1437 km and a perigee of 343 km.”

It should be noted that the initial orbital inclination for Polyot 1 was not included in the launch announcement.

When Polyot 2 was launched on 12 April, 1964 no further details of the craft emerged, but the launch announcement gave the following information:

(1) "After separation from the carrier rocket, and ballistic flight, Polyot 2 was put into an initial orbit by means of a special motor, and in conformity with the predetermined programme carried out numerous manoeuvres in various directions. As a result of performing one of these manoeuvres in the region of the equator the space vehicle considerably changed the angle of inclination of the plane of the orbit.”

(2) "After performing the whole programme of manoeuvres, the final orbit of Polyot 2 has the following parameters:

angle of inclination to the plane of the equator 58.06°

apogee height 500 km

perigee height 310 km”

It should be noted that there was no initial orbit given for Polyot 2. If we work only on the Soviet-announced data it is impossible to calculate the actual delta-Vs involved in the flights. It should also be remembered that Polyot 2 (and, one assumes, Polyot 1) put itself into orbit after separating from the launch vehicle, and therefore some of the delta-V capacity is hidden in this unknown manoeuvre.

The Orbital Manoeuvres

The Polyot 2 launch announcement suggested that the orbital plane change was made near the equator, but in fact it seems that the burn was made near the apogee point at about 47°S. The RAE quotes no initial orbital inclination for Polyot 1, and for this I have assumed that the payload had the same inclination as the initial Polyot 2 orbit. It will be noted that the Polyot 1 in-orbit manoeuvre was 383 m/s and that for Polyot 2 was 480 m/s. However,it is possible that the two craft were identical and the difference of about 100 m/s delta-V was made up in the launch phase of the vehicles.

There is one confusing point in the RAE’s entry for Polyot 2. The launch announcement suggests that Polyot 2 only put itself into orbit, since all the launch vehicle stages were suborbital:, however, the RAE shows an object designated a "Rocket” (1964-19A) which decayed from orbit after 183 days. Since it decayed so quickly from what was a reasonably high orbit (236-465 km), this might simply be a small fragment thrown off by Polyot 2 soon after orbital injection.

Polyot 1 seems to have manoeuvred quickly from its initial orbit, while reference to the epochs of the RAE orbits shows that Polyot 2 remained in its initial orbit for a day or two after launch, the manoeuvres not coming until after 14 April 1964.

Possible Missions for Polyot

It was expected that there would be a series of Polyot flights,followed by an easily-identifiable operational use of the manoeuvring system. However, the flights ended after the second launch, and it is difficult to point with certainty at the operational use of the technology.

The launches came from Tyuratam, and the inclination used had not been used before and has not been used since. The closest inclination to 59.9° to be employed is 61°, used for the twin Elektron flights in 1964. The Elektron flights used the Standard Launch Vehicle, the “A-1” in Sheldon’s system of designations. Sheldon lists the Polyot launch vehicle as "A-m”, that is the basic SS-6/Sapwood booster without any upper stages: "m” refers to the manoeuvrable Polyot craft. Considering the programmes being undertaken at the time,there are.perhaps four missions which might be considered for the application of the Polyot experience:

(1) Testing the “e-stage” of the "A-2-e” deep space launch vehicle.

(2) Testing an up rated Vostok instrument module for possible use in the Voskhod programme.

(3) Testing the second generation Luna instrument module.

(4) Initial test flights of the Soyuz manoeuvring system.

These four ideas are more fully developed below.

An “e-Stage” Test?

It should be remembered that in the early 1960s the small escape stage added to the up rated Vostok launch vehicle ("A-2”) had proved very unreliable. In 1962 three Venus probes and two Mars probes were stranded in Earth parking orbits due to the failure of the “e-stage” to work properly. Out of six planetary shots, only Mars 1 got into a heliocentric orbit. At the beginning of 1963 the first of the second generation Luna probes was left in Earth orbit after a similar failure. Following the problems with Luna 4 in April 1963, the Soviets could have decided to halt flights of the “A-2-e” launch vehicle until the “bugs” had been sorted out of the fourth stage. In 1964 there were launch windows for both Venus (March-April) and Mars (November) and the Soviets wanted to launch probes if at all possible.

The RAE suggests that the Polyot craft was irregular, about 2 metres long and 1 metre in diameter: the mass is estimated to be about 600 kg. Full data is not available for the “e-stage”,but it seems to be generally 2.5 metres long and 2 metres in diameter, with a mass of around 1000 kg. This is not too far from the Polyot estimates. The fuelled mass of the “e-stage” is about 6?4 tonnes (Venera 8 was 1184 kg, and the fuelled parking orbit mass was about 7500 kg), so it could not be launched fully fueled into orbit by the Sapwood booster without an upper stage. The maximum payload orbited by the Sapwood alone was Sputnik 3 into a 65.2°, 220 by 1865 km orbit. The Sputnik had a mass of 1327 kg, which would scale with about 2600 kg to the initial Polyot 1 orbit. If the fully fuelled “e-stage” had been launched atop the Sapwood the launch delta-V obtained would have been in excess of 12 km/s, so if the “e-stage” had been flown it could not have been fully fuelled. However, one of the problems with the “e-stage” was that it was only making partial burns, if it ignited at all, so a test of a partially fueled version would simply have proved that the stage’s engine could ignite.

There is one other piece of evidence which would seem to rule out the use of the “e-stage” on a Sapwood. Polyot had a restart capability, as shown by its ability to enter an initial orbit and then about two days later manoeuvre to another orbit. The “e-stage” has not yet (to 1980) exhibited a re-start capacity and this would not be required on any of its missions which only need a single burn to be accomplished.

An up-rated Vostok Engine System?

When the modified Vostok was introduced into the manned programme as the Voskhod in October 1964, it was expected that the craft would have an orbital manoeuvre capacity which would allow later Voskhods to complete a rendezvous and docking. The Vostok instrument module had a fueled mass of about 2050 kg. The specific impulse of the TDU-1 engine was 266 sec and according to Vick this implied a fuel capacity of 155 kg.

The Vostok had a mass of about 4750 kg while Voskhod 2 had a mass of nearly 5700 kg. A possible rendezvous version of Voskhod might have had a mass of about 6,000 kg. An extra 100 m/s of manoeuvring fuel has been allowed for the rendezvous mission.

If Polyot was a test of the up-rated Vostok instrument unit for a Voskhod rendezvous mission, the new unit launched alone would have a delta-V capacity of 480 m/s which ties in very well with the Polyot 2 manoeuvres, so this is a possible contender.

A Luna Instrument Module Test?

Luna 4 was launched in April 1963 to the Moon, but it seems to have failed to make even the most minor mid-course correction,thus pointing to a possible failure of the KDTU-1 manoeuvring unit. It has been noted previously by the writer that the second generation Luna instrument/retro-fire stage had an empty mass of about 370 kg and carried up to 830 kg of fuel. If the unit were to be launched without the Luna capsule and navigation system it would have a delta-V capacity of 3200 m/s, which is rather high for a Polyot mission. Perhaps the unit was only partially fuelled. Even so, the mass would be too little for the Sapwood to place in the orbits which we have seen. Therefore, Polyot does not seem to be connected with the problems in the Luna programme.

A Soyuz Manoeuvring System Test?

Most observers of the Soviet space programme generally agree that the Voskhod programme conducted in 1964-6 (with the Voskhod known as Cosmos 110 carrying two dogs in 1966) was a stop-gap measure between the Vostok and impending Soyuz manned programmes. If Voskhod had not intervened it seems probable that Soyuz would have flown its initial manned missions in 1965,after unmanned test flights in 1964. If this timetable is near the truth, the initial testing of the Soyuz manoeuvring system would be expected after completion of the Vostok missions in 1963 and before the first fully-fledged unmanned Soyuz missions in 1964. This timing agrees with the launch dates of the Polyot craft.

It has been noted by Woods that Soyuz has had two propulsion systems. The first used a torus fuel tank,with additional fuel being carried in four spheres in the Soyuz instrument module. One has to ask which (if either) of these two systems would best fit the Polyot missions.

The Soyuz instrument module has an empty mass of 1860 kg, including the torus fuel tank, while 2965 kg of fuel (1150 kg in the spheres and 1815 kg in the torus) can be carried. The re-entry module for Soyuz/Zond is estimated to be about 2600 kg, although on a possible early propulsion test only a boiler-plate module needs to be carried, since a re-entry wasn’t to be attempted. Taking the instrument module as 4,825 kg, a payload shroud directly over the top of the Sapwood of 3,500 kg (for Soyuz this seems to be 4,500 kg), and a boilerplate re-entry module of 1,750 kg results in a delta-V of about 8400 m/s from launch to final orbital change, which is that found on Polyot 2. For Polyot 1 the launch delta-V was about 8300 m/s.

Cosmos 102 & 125: A Connection?

At the end of 1965 and in mid-1966 there were two flights in the Cosmos programme which are sometimes connected with the two Polyot flights: Cosmos 102 and Cosmos 125. The The RAE describes the payloads as possibly being 10 m long and 2 m in diameter: Cosmos 102 is described as being cylindrical, while Cosmos 125 is described as a cone-cylinder, with a mass of 4,000 kg.

The speculation about a Polyot connection with these flights stems from the two Cosmos orbits having perigees far in the southern hemisphere, as if an engine had ignited on its first pass through a southern hemisphere apogee to boost the former perigee to a new apogee. However, nowhere is there an indication of an orbit earlier than the one shown for each mission, so it is impossible to indicate the amount of the orbital burn. Sheldon lists the two Cosmos flights as using the Sapwood in an "A-1-m” version; that is the standard Vostok booster with an unknown manoeuvring unit added. Whether this “m” stage is the same as that found on the Polyot “A-m” flights cannot be decided finally as yet, although the present writer tends to think not. The implied orbital changes for the Cosmos missions are too small for a Polyot application, and the missions might be connected somehow with the development of hardware to be subsequently used by the military Scarp launch vehicle.

Conclusion: Voskhod or Soyuz/Zond?

Of the original four ideas for the application of Polyot technology, the only ones to have stood the test of analysis are the hypothetical Voskhod manoeuvring system and an early development version of the Soyuz vehicle. Faced with these two contenders the writer would certainly choose the latter. There is no proof that Voskhod was being readied for a rendezvous version, and with the spare retrorocket system being on top of the Voskhod, the geometry of an actual docking is difficult to visualise. Soviet plans for a docking after the Voskhod 2 flight most probably hinged on the new Soyuz being available for manned flight before the end of 1966. It seems probable that, although the main Soyuz programes was delayed due to the hastily-prepared Voskhod missions,some early Soyuz hardware would be in the pipe-line for flight testing in late 1963, if all-up unmanned flights were to take place in the latter half of 1964 (such flights would be like Cosmos 133 and 140 in late 1966 and early 1967 respectively).