Soviet/Russian Spaceplane Concepts

During the Cold War, both the US and Soviet Union developed numerous concepts for reusable spaceplanes. Many of these concepts, such as the X-20, MiG-105, STS, and Buran, are well known. While flipping through my copy of Unflown Wings, I happened across a couple of other, lesser known spaceplane concepts developed in the Soviet Union and Russia during the past few decades. To my knowledge, none of these ever flew, but there's some interesting designs that were drawn up.

(credit for all pictures goes to Yefim Gordon and Sergey Komissarov)

 The first of these is the Tu-136, also known as Zvezda, which was developed during the late 1960s. As is apparent from the picture, it appears to be roughly analogous to the X-20, although there are some notable design differences. Like the X-20 it would have been vertically launched on top of an expendable launch vehicle, most likely an existing Soviet booster. Based on the weight given for the vehicle (7-9 tons), it is likely that an early version of the Proton rocket would have been the launch vehicle for the Tu-136. Like the X-20, the Tu-136 would have been intended for military usage in LEO, although the exact nature of these missions is unknown.
 Interestingly, it appears that this design was intended to be able to operate in both manned and unmanned modes.

 

The next design was the Tu-2000. This was not a single design, but rather a series of several conceptual spaceplane designs.  Unlike the Tu-136, they would have been launched horizontally, either from a runway or a purpose built (and truly mammoth) carrier aircraft. Given that the Tu-2000 was to function as an SSTO spaceplane, massive amounts of LH2/LOX fuel would have been needed. Some of the concepts would have had takeoff weights of almost 300 tons. Total orbital payload was projected to be in the 5-10 ton range.

In Unflown Wings, it is mentioned that the Tu-2000 would have featured up to six turbojet engines (in addition to liquid fuel rocket engines), in order to improve in-atmosphere performance. Interestingly, it is also mentioned that use of a nuclear rocket engine was considered, due to its higher specific impulse compared to chemical engines. This is probably the first time I have heard of a nuclear engine being proposed for such an application.

The MiG AKS (AKS roughly translates as 'aerospace system') was a proposal for a reusable spaceplane dating to the 1980s/1990s. As can be seen from the picture, it would have been launched from a high speed 'mothership' aircraft, likely travelling at hypersonic speeds. The mothership was planned to operate on conventional jet fuel at low speeds, and LH2 at hypersonic speeds. While this would have complicated logistics greatly, it was believed that the benefits of an air launch (reduced delta-v, more flexibile launch site) would have been worth the disadvantages.
There is also brief mention in Unflown Wings of a MiG designed spaceplane named 'Oryol'. This was intended to be ground launched, with one proposal having it launched by an electromagnetic mass driver. However, it was seen as less technically feasible than the AKS, and was not developed as far.

 One interesting design from the 1990s is the S-XXI, developed by the Myasishchev design bureau. Unlike most other Soviet/Russian concepts, which were intended to be fully capable of reaching orbit, and used for military missions, the S-XXI would have been suborbital, and used for space tourism. Launched from the back of a modified M-55 carrier aircraft, the S-XXI would have reached an altitude of just over 100 km on a ballistic trajectory, allowing the passengers to briefly experience weightlessness. Though it was intended to have flown in 2005, it was ultimately cancelled due to lack of funding.