As we took the time to explore in depth recently, the U.S. government has long been interested in the potential applications of a reusable manned and unmanned spacecraft, as well as a mothership aircraft to help loft them into orbit. Now, Russia is reportedly developing its own new unmanned spacecraft that will hitch a ride into the upper atmosphere on the back of a modified high-altitude research plane before blasting into space. Russia's state-run media outlet RIA Novosti published concept art of the spacecraft, known by the acronym MLD, and an infographic showing a typical mission on Feb. 4, 2019. The story does not say what MLD stands for and does not mention the Myasishchev M-55 Geophysica research plane, also known by the NATO reporting name Mystic-B, by name, though the infographic clearly depicts it as the mothership.

The International Scientific Optical Network (ISON), which the Russian Academy of Sciences manages through the Keldysh Institute of Applied Mathematics, is reportedly leading the development of the MLD, on behalf of Russia's space agency Roscosmos. RIA Novosti did not say what the specific mission or missions for the spacecraft might be or why ISON, which is responsible at present for around 30 terrestrial telescopes at 20 observatories in 10 countries, was in charge of the project. The MLD concept art shows a rocket-like central fuselage with a delta wing configuration. There are two vertical stabilizers pointing up from the edge of each wingtip. The spacecraft is supposed to be reusable, according to RIA Novosti, but there is no obvious internal payload bay for releasing objects into orbit.

ISON A cutaway artist's conception of the MLD reusable spacecraft.

The spacecraft will use old Russian-made components, including the same 14D30 rocket booster found in the upper stage of a Briz-M space launch vehicle as its primary means of propulsion, Yuri Bakhvalov, ISON's director, told RIA Novosti. Based on the dimensions of the Briz-M, the MLD is a diminutive craft that is significantly smaller than the U.S. Air Force's secretive X-37B unmanned space shuttle and is downright tiny compared to the U.S. Defense Advanced Research Projects Agency's (DARPA) in-development XS-1 reusable spacecraft. The infographic shows that the mothership will be based on the M-55 and carry the spacecraft on top of its fuselage. This aircraft would carry it to an appropriate altitude, possibly between 80,000 and 100,000 feet based on other known two-stage-to-orbit concepts. The Geophysica's normal service ceiling is 70,500 feet. Once there, the MLD's rocket motor would fire and it could either travel at hypersonic speeds of around Mach 7 in the upper atmosphere at altitudes of more than 500,000 feet or actually fly into space and enter a shallow, rapidly degrading orbit, according to RIA Novosti. At the conclusion of its flight, the MLD would re-enter the atmosphere if it had gone into space or otherwise begin gliding closer to the ground. At a certain altitude, it would deploy parachutes and drift the rest of the way down to the ground where personnel could recover the unmanned spacecraft. ISON claims the design would be reusable for up to 50 flights.

ISON An infographic showing the proposed flight profile for the two-stage-to-orbit system consisting of a modified M-55 mothership and the MLD spacecraft.

There is no information on what modifications this 1980s aircraft might need to perform this mission. A mothership configuration with smaller craft mounted on top of the fuselage is notoriously complex and potentially dangerous, with a significant risk that the vehicle on top will crash into the launching aircraft, destroying them both. The small size of the MLD could help mitigate any potential hazards. It's also not clear whether the plan might call for restarting production of the Geophysica or another similar aircraft. Myasishchev only ever built five of these slender-wing, twin-boom aircraft, including a two-seat M-55UTS trainer version. Since the end of the Cold War, the Russian Air Force has used these planes officially for high-altitude research purposes, including flights over the Arctic and Antarctic regions. The M-55 is roughly analogous in its basic mission to NASA's ER-2 and WB-57F aircraft, which are derived from the U-2 and RB-57F high-altitude spy planes, respectively.

Leonid Faerberg via Wikimedia A Myasishchev M-55 Geophysica.