Post 9: The Soviet Shuttle
Akin’s Law of Spacecraft Design
#39. (alternate formulation):
The three keys to keeping a new human space program affordable and on schedule:
1) No new launch vehicles.
2) No new launch vehicles.
3) Whatever you do, don't develop any new launch vehicles.
Following the publication of the Joint Decree establishing the Soviet shuttle project, this immediately became the main focus of efforts at TsKBEM as system lead, and at the newly-formed NPO Molniya, a spin-off from the Mikoyan-Gurevich (MiG) Design Bureau, which was to deliver the spaceplane. Mishin placed Konstantin Bushyev, TsKBEM’s chief of piloted space vehicle design, in overall charge of development of the launcher-plus-orbiter system, with Molniya’s Gleb Lozino-Lozinskiy leading the orbiter design effort.
Whilst the L3M lunar landing project had the support of the Academy of Sciences, the shuttle was now seen as a priority for the military, and under Brezhnev it was the military that held the most sway. Mishin was frustrated by this, still seeing the lunar mission as his main objective, but he could hardly turn down the opportunity to lead the nation’s flagship space programme for the next decade, especially after having lost the space station project to Glushko. So Mishin accepted the assignment, and worked to shape the shuttle into something that would minimise the disruption to L3M, and perhaps even advance and secure the lunar launch infrastructure.
Central to this was the use of Groza as the launch vehicle for the Soviet spaceplane. Although there were voices within both the Air Force and TsKBEM itself calling for a clone of the US shuttle design (“The Americans aren’t dumber, do it the way they do!”), there were other compelling reasons to avoid simply duplicating the US shuttle, even apart from Mishin’s desire to maximise re-use of the existing N-1 infrastructure. For one, although Soviet experience with hydrolox propellants was improving with the development of the Blok-Sr upper stage, the creation of large, high-thrust, reusable
hydrogen-oxygen engines like those of the shuttle would have been a daunting task. Similarly, the large solid rocket boosters employed by the Americans were well beyond the scope of anything that had been built in the USSR to that point. The industrial base to build such motors did not exist, and transporting the heavy SRB segments to the Baikonur cosmodrome for each launch would be a considerable challenge. Once launched, these boosters would not have the option of splashing down for recovery, but would instead either need to touchdown on land, or be simply left to crash as expendable stages. Developing all these systems would add years and billions of rubles to the project, assuming it would be possible to develop at all.
Despite this decision to follow the N-1 derived path, the Draft Plan delivered in December 1976, providing the overall design specification for the system, made some significant changes to the vertical-landing lifting body proposed in earlier TsKBEM studies. The most visible of these was the inclusion of wings on the orbiter.
In the original concept, the shuttle spaceplane was to be a wingless, roughly cylindrical craft 34m long, with a pair of small wings at the rear of the vehicle to control re-entry, which would be folded against the side of the plane on launch. After slowing in the upper atmosphere, the shuttle would descend vertically under parachutes before making a final rocket-assisted soft landing in the Kazakh steppe. This reduced aerodynamic loads on the launch vehicle, and avoided the need for expensive runway facilities at Baikonur, but it suffered from a low cross-range capability - just 800km - and presented some significant logistical challenges in returning the vehicle and its payload to the launch site. The cross-range capability was particularly important due to the Soviets lacking the variety of emergency landing sites made available to the Americans by their allies.
To address these shortcomings, the 1976 design added a pair of straight-edged deployable wings to the orbiter. These would be stowed beneath the payload bay during launch, orbit and re-entry, before swinging out to provide lift and control for the descent through the atmosphere. Small jet engines would provide thrust to guide the vehicle to a landing at a runway at Baikonur, or any suitable military runway in case of emergency. These would dramatically improve the orbiter’s subsonic lift/drag ratio, allowing a cross-range of almost 2700km.
The inclusion of variable-geometry wings - only recently introduced into the Soviet Air Force with the MiG-23 in 1974 - was controversial from the point of view of both the additional weight of the swing wing mechanisms, and the complexity and associated opportunities for failures it introduced to the system. For the weight issue, this was seen as an inevitable consequence of providing a reasonable cross-range capability without imposing undue loads on the launcher, while stowing the wings for re-entry at least minimised the impact by removing the need to provide them with additional thermal protection. The added complexity was a concern, however, and became a significant driver for the other major change in the design; the emergency escape system.
For their shuttle, NASA were assuming that, once the first few test flights were completed, regular operations would be so routine and safe that no emergency escape system would be needed. With the recent experience of the N-1 launch failures and the Soyuz 1 disaster in mind, the engineers at TsKBEM and NPO Molniya did not share this confidence, and were determined to include a robust escape system for their shuttle. This took the form of a separable nose section, containing the crew cabin and nose RCS thrusters. Upon launch, an escape rocket would be attached to the nose, allowing the capsule to be pulled clear in the event of a launcher failure, just as on crewed Soyuz or Groza launches. Once the high acceleration portion of the launch was over, this escape rocket would be jettisoned, but the cabin would retain the ability to split from the main body of the orbiter using its own small, internal solid rockets. In case of a failure on-orbit, the nose RCS units would be used to brake the capsule for re-entry, with small body flaps used to control the descent. The final landing would be either under parachutes with solid braking rockets, or the crew would eject and come down under their own parachutes.
Although offering a robust set of options for escaping disaster, these emergency systems added considerable mass to the orbiter. Together with the swing wings and the usual growth in mass as the design was detailed, this threatened to push the orbiter beyond the 105 tonne maximum payload of the basic N-1F Groza launch vehicle. After their experience in paring mass budgets to the bone on the N1-L3 programme, the team at TsKBEM were reluctant to repeat the experience with the shuttle. It was possible that they could remain within budget by sacrificing payload mass, but Mishin saw another opportunity present itself to use the shuttle programme to enhance his lunar ambitions.
In 1965 a study had been conducted to investigate replacing the Blok-V 3rd stage of the N-1 with a large hydrolox stage, the Blok-V-III. This study was later superseded by plans to develop the Blok-S and Blok-R upper stages, which were then consolidated into Blok-Sr, but with the experience gained in the intervening decade, a large hydrolox upper stage could be within striking distance. The introduction of Blok-V-III would boost Groza’s payload to LEO up to 125 tonnes. This would instantly solve the shuttle’s weight problems, while giving Mishin a powerfully uprated launcher for the lunar base being designed by Barmin’s bureau. The Draft Plan therefore included specifications of the development of the N-1FV-III and associated test and ground support equipment.
Although the inclusion of a hydrolox third stage removed concerns over the orbiter’s mass from the launch side of operations, the growth in weight was posing considerable problems for the re-entry phase, and in particular with respect to thermal protection. Keeping the wings stowed during re-entry saved the mass of having to protect them from aerodynamic heating, but it also reduced the cross-sectional area the spacecraft could use to slow itself in the atmosphere. This, together with this increased mass of the orbiter, meant that the orbiter would experience higher temperatures on re-entry, to the point where it wasn’t clear if a US-style thermal protection system based on silica tiles would be up to the job. In addition, there were concerns that the quartz sand needed to manufacture such tiles was simply not available in the USSR, and may have to be imported from Brazil.
In response to these concerns, the designers at Molniya and TsKBEM investigated alternatives for protecting the shuttle during re-entry. They considered the use of exotic superalloys, similar to those developed in the US for the cancelled Dyna-Soar project, but this technology was considered too immature to be integrated into an operational vehicle in the near term. Another option, based on work done previously by the Myasishchev Design Bureau for the “Project 48” spaceplane study, was foamed ceramic tiles. These would be lighter than quartz-fibre based tiles, while offering a similar performance, with the weight saved allowing for the inclusion of an active cooling for critical areas.
All of these issues, though challenging, appeared to be soluble, and by the end of 1976 Mishin and his deputies were confident they would be able to deliver the vehicle the military were asking for, but there was a significant price to pay. In order to advance work on the shuttle, budget allocations to the L3M programme, and to the crewed LEK vehicle in particular, had been reduced, and engineers previously focussed on the moon landing were switched to working on the detailed schematics for shuttle sub-systems. A major upgrade of the Site 110 launch facilities would be needed to adapt the rotating service towers to the shuttle’s needs, as well as the hydrogen-fueled Blok-V-III, which was significantly larger than the Blok-Sr upper stage. This would further delay the dual-launch capability needed for L3M. True, the new capabilities enabled by the shuttle related upgrades would allow for a far more robust and ambitious programme once completed, but this was scant comfort for many of those who had spent the last decade chasing the Moon, and now yet again saw their target receding into the distance.
In spite of these concerns, the engineers at TsKBEM and Molniya continued to prove their dedication, and the Draft Project was presented to an expert commission for review in December 1976. This review was completed in July 1977, and was followed by a formal government approval for the development plan in November 1977, shortly after the American Shuttle Enterprise completed its Approach and Landing Test series.
As well as an approved design and a clear development path ahead, it was at this point that the Soviet shuttle programme also acquired a name: Baikal.
 This is the original cross-range capability of the OTL MTKVP design, as stated in “Energiya-Buran
”, Bart Hendrickx and Bert Vis.
 This is very similar to the Convair T-18 and FL-3
designs developed in the 1960s/70s as part of their shuttle studies.
 This is based upon the 1500 nautical mile cross range for the Convair T-18, as stated in “Space Shuttle: Developing an Icon
, Vol. I” by Dennis R. Jenkins.
 This was a real concern on the OTL Buran programme, but in the end a suitable domestic source was found.