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Airlock Module: Future gateway for spacewalks
In the second half of the 2000s, while planning for the expansion of the Russian segment of the International Space Station, ISS, engineers at RKK Energia conceived a new Airlock Module, ShM, which would replace the Docking Compartment, SO, currently used for spacewalks. The new design later evolved to support plans for orbital assembly of deep-space vehicles.
An artist rendering of the Airlock Module, ShM, based on preliminary engineering designs.
New kind of airlock
Unlike the one-room SO module, serving as an airlock onboard the Russian segment of the ISS since 2001, the new module would feature an expanded two-section design. The main ball-shaped compartment, derived from the Node Module, UM, would feature egress and ingress hatches and would be depressurized during spacewalks. In the meantime a newly developed cylindrical section would contain all the support systems and would remain pressurized.
The initial concept of the module featured a single docking port on the cylindrical section, making it a "dead end" for the Russian segment in terms of access for incoming ships. However, the later incarnation of the design appearing around 2014, showed a second docking port on its outer end, which would open the module for arriving Soyuz and Progress vehicles.
As of 2011, the long-term plan for the development of the Russian segment called for the launch of the Airlock Module after the delivery of one or two Science and Power Modules, NEMs. The Airlock Module would be launched on the Soyuz-2 rocket along with the modified propulsion section of a Progress cargo ship, which would boost the vehicle to the station and dock it to the Node Module, UM. The Progress space tug would then be jettisoned from the airlock and sent on a controlled reentry over the Pacific to burn-up in the atmosphere.
By 2014, with the retirement of the ISS on the horizon, the launch of the new airlock to the ISS was no longer considered likely, leaving the role of exit point for Russian spacewalks to the Docking Compartments, as long as their safe operation could be certified during the entire lifetime of the outpost. However, the Airlock Module soon re-emerged in the plans for a new station.
On its exterior, the Airlock Module could carry various add-on payloads used during spacewalks, such as special rigs for assembling the truss structures of future large vehicles heading into deep space. This particular functionality apparently prompted further evolution of the Airlock Module concept into the so-called Module-Shipyard, or MS (for Module-Stapel in Russian). It would be dedicated to assembly operations on the post-ISS Russian orbital facility. Such vehicles as the proposed solar-powered and electrically propelled space tugs intended for the support of lunar expeditions could be first assembled and tested at the MS module.
In its new role, the MS module was also expected to feature a pair of newly developed robotic arms for servicing, assembly and cargo transfer, including such tasks as picking up and launching payloads. The 8.2-ton module would be designed to operate in space for at least 10 years.
The MS module was among six other components included in the so-called Prospective Piloted Orbital Infrastructure, PPOI, essentially, a new post-ISS space station which would be assembled in the low Earth orbit, should Russia choose this path for its future space program. In the first half of 2014, funding for the development of the MS module was a part of the budget request for the 10-year Russian space program, known as FKP-2025, which was expected to come into effect in 2016. However, according to the budget proposal, the active development of the MS module would not come until 2021. Even that would cover only the completion of the preliminary design during 2021, followed by the development of the design documentation a year later and the beginning of ground testing around 2023.
A budget request for the development of the Module-Shipyard, MS, (in millions of rubles, as of 2014):
The actual launch of the module would probably take place beyond the FKP-2025, unless the Russian government made the PPOI project a priority for the current Russian space program. The Russian Academy of Sciences, RAN, is expected to issue a formal technical assignment for all components of the future station, including the MS module. As other newer space station components, the basic structure of the MS module could serve as a basis for future deep-space vehicles comprising outposts in the Lagrangian points or in orbit around the Moon. At least one proposal for a commercial space station in the Earth orbit unveiled in 2011, also relied on the architecture of the Airlock Module.
An ISS flight manifest surfaced in April 2015 indicated the launch of the ShM module at the beginning of the second quarter of 2024.
Known specifications of the Airlock Module, ShM:
Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:
Initial concept of the Airlock module, ShM. Credit: RKK Energia
A concept of the Airlock Module, ShM. Credit: RKK Energia
The ShM/MS module could be used as basis for orbital assembly. Credit: RKK Energia
A circa 2011 concept of a mini-station based on the design of the Airlock Module. Click to enlarge. Copyright © 2011 Anatoly Zak