The Past, Present, And Future Of Inflatable Space Habitats

Recently, a prototype inflatable space station module built by Sierra Space exploded violently on a test stand at NASA’s Marshall Space Flight Center in Alabama. Under normal circumstances, this would be a bad thing. But in this case, Sierra was looking forward to blowing up their handiwork. In fact, there was some disappointment when it failed to explode during a previous test run.

LIFE Module Burst Test

That’s because the team at Sierra was looking to find the ultimate bust pressure of their 8.2 meter (26.9 foot) diameter Large Integrated Flexible Environment (LIFE) module — a real-world demonstration of just how much air could be pumped into the expanding structure before it buckled. NASA recommended they shoot for just under 61 PSI, which would be four times the expected operational pressure for a crewed habitat module.

By the time the full-scale LIFE prototype ripped itself apart, it had an internal pressure of 77 PSI. The results so far seem extremely promising, but Sierra will need to repeat the test at least two more times to be sure their materials and construction techniques can withstand the rigors of spaceflight.

Sierra is a targeting no earlier than 2026 for an in-space test, but even if they nail the date (always a dubious prospect for cutting edge aerospace projects), they’ll still be about 20 years late to the party. Despite how futuristic the idea of inflatable space stations may seem, NASA first started experimenting with the concept of expandable habitat modules back in the 1990s, and there were practical examples being launched into orbit by the early 2000s.

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Space Shuttle Atlantis connected to Russia's Mir Space Station as photographed by the Mir-19 crew on July 4, 1995. (Credit: NASA)

The Soviet Space Station Program: From Military Satellites To The ISS

When the Space Race kicked off in earnest in the 1950s, in some ways it was hard to pin down where sci-fi began and reality ended. As the first artificial satellites began zipping around the Earth, this was soon followed by manned spaceflight, first in low Earth orbit, then to the Moon with manned spaceflights to Mars and Venus already in the planning. The first space stations were being launched following or alongside Kubrick’s 2001: A Space Odyssey, and countless other books and movies during the 1960s and 1970s such as Moonraker which portrayed people living (and fighting) out in space.

Perhaps ironically, considering the portrayal of space stations in Western media, virtually all of the space stations launched during the 20th century were Soviet, leaving Skylab as the sole US space station to this day. The Soviet Union established a near-permanent presence of cosmonauts in Earth orbit since the 1970s as part of the Salyut program. These Salyut space stations also served as cover for the military Almaz space stations that were intended to be used for reconnaissance as well as weapon platforms.

Although the US unquestionably won out on racing the USSR to the Moon, the latter nation’s achievements granted us invaluable knowledge on how to make space stations work, which benefits us all to this very day.

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The Forgotten Rescue Of The Salyut 7 Space Station

With only two space stations in orbit around Earth today in the form of the International Space Station and the Chinese Tiangong (‘Sky Palace’) station, it’s easy to forget how many space stations were launched in the previous century. And the Soviet Union launched by far the most, as part of the Salyut (Russian for ‘salute’ or ‘fireworks’) program. Although the program entailed both military (Orbital Piloted Station, or OPS) and civilian (Durable Orbital Station, or DOS) stations, it was the civilian stations that saw the most success, as well as the most daring rescue attempt with the recovering of the Salyut 7 space station.

Salyut 7 (DOS-6) was set to repeat Salyut 6’s success after its launch on April 19th 1982, until disaster struck in February 1985. Due to a series of electrical and other faults ground communication with the space station was cut off, and the at the time unmanned space station began to gradually tumble towards the Earth’s atmosphere. This left those in charge with two options: leave the station to burn up in the atmosphere, or stage a rescue mission.

Ultimately, on June 6th, 1985, Soyuz T-13 launched to rendezvous with Salyut 7. On board were cosmonauts Vladimir Dzhanibekov – who had previously manually docked with Salyut 7 – and Viktor Savinykh. Both men had done all they could to perform a manual docking and attempt to revive the stricken space station. Ultimately they managed to revive the station using what little charge was left in its batteries and the Soyuz’s thrusters, all the while braving freezing temperatures in the dead station’s interior.

Salyut 7 would continue to perform its duties until February 1991, with Mir (DOS-7, launched 1986) as the first modular space station taking over. The final DOS module (DOS-8) that directly traces its lineage to this era is still in orbit today as the ISS’ Zvezda module, keeping the Salyut legacy and the bravery of Dzhanibekov and Savinykh alive.

Look Out Below! China’s Heavy-Lift Rocket Due For Uncontrolled Reentry Within Days

On April 28th, China successfully put the core module of their Tianhe space station into orbit with the latest version of the Long March 5B heavy-lift booster. This rocket, designed for launching large objects into low Earth orbit, is unique in that the 33.16 m (108.8 ft) first stage carries the payload all the way to orbit rather than separating at a lower altitude. Unfortunately, despite an international effort to limit unnecessary space debris, the first stage of the Long March 5B booster is now tumbling through space and is expected to make an uncontrolled reentry sometime in the next few days.

The massive booster has been given the COSPAR ID 2021-035-B, and ground tracking stations are currently watching it closely to try and determine when and where it will reenter the Earth’s atmosphere. As of this writing it’s in a relatively low orbit of 169 x 363 km, which should decay rapidly given the object’s large surface area. Due to the variables involved it’s impossible to pinpoint where the booster will reenter this far out, but the concern is that should it happen over a populated area, debris from the 21 metric ton (46,000 pound) booster could hit the ground.

The Tianhe core module.

This is the second launch for the Long March 5B, the first taking place on May 5th of 2020. That booster was also left in a low orbit, and made an uncontrolled reentry six days later. During a meeting of the NASA Advisory Council’s Regulatory and Policy Committee, Administrator Jim Bridenstine claimed that had the rocket reentered just 30 minutes prior, debris could have come down over the continental United States. Objects which were suspected of being remnants of the Long March 5B were discovered in Africa, though no injuries were reported.

China’s first space station, Tiangong-1, made an uncontrolled reentry of its own back in 2018. It’s believed that most of the 8,500 kg (18,700 lb) burned up as it streaked through the atmosphere, and anything that was left fell harmlessly into the South Pacific Ocean. While small satellites are increasingly designed to safely disintegrate upon reentry, large objects such as these pose a more complex problem as we expand our presence in low Earth orbit.

ISS Ham Radio Repeater

There is a long history of spacecraft carrying ham radio gear, as the Space Shuttle, Mir, and the ISS have all had hams aboard with gear capable of talking to the Earth. However, this month, the ISS started operating an FM repeater that isn’t too dissimilar from a terrestrial repeater. You can see [TechMinds] video on the repeater, below.

The repeater has a 2 meter uplink and a 70 centimeter downlink. While you can use a garden variety dual-band ham transceiver to use the repeater, you’ll probably need a special antenna along with special operating techniques.

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Docking With ISS Isn’t As Easy As You Might Think

Complexity is a funny thing. In prehistoric times, a caveman might float across a lake on a log. That’s simple. But as you add a rudder, a sail, or even a motor, it gets more and more complex. But if you add enough complexity — a GPS and an autopilot, for example, it becomes simple again. The SpaceX Dragon capsule actually docks itself to the ISS. However, the crew on the station can take over manually if they need to. What would that be like? Try the simulation and find out. If you don’t make it on the first, try, [Scott Manley’s] video below might help you out.

This isn’t a flashy Star Wars-style simulator. Think more 2001. Movement is slow and it is easy to get out of control. The user interface is decidedly modern compared to the old Apollo era

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SpaceX Offers NASA A Custom Moon Freighter

Under the current Administration, NASA has been tasked with returning American astronauts to the Moon as quickly as possible. The Artemis program would launch a crewed mission to our nearest celestial neighbor as soon as 2024, and establish a system for sustainable exploration and habitation by 2028. It’s an extremely aggressive timeline, to put it mildly.

To have any chance of meeting these goals, NASA will have to enlist the help of not only its international partners, but private industry. There simply isn’t enough time for the agency to design, build, and test all of the hardware that will eventually be required for any sort of sustained presence on or around the Moon. By awarding a series of contracts, NASA plans to offload some of the logistical components of the Artemis program to qualified companies and agencies.

Artist’s Rendering of the Dragon XL

For anyone who’s been following the New Space race these last few years, it should come as no surprise to hear that SpaceX has already been awarded one of these lucrative logistics contracts. They’ve been selected as the first commercial provider for cargo deliveries to Gateway, a small space station that NASA intendeds to operate in lunar orbit. Considering SpaceX already has a contract to resupply the International Space Station, they were the ideal candidate to offer similar services for a future lunar outpost.

But that certainly doesn’t mean it will be easy. The so-called “Gateway Logistics Services” contract stipulates that providers must be able to deliver at least 3,400 kilograms (7,500 pounds) of pressurized cargo and 1,000 kilograms (2,200 pounds) of unpressurized cargo to lunar orbit. That’s beyond the capabilities of SpaceX’s Dragon spacecraft, which was only designed to service low Earth orbit.

To complete this new mission, the company is proposing a new vehicle they’re calling the Dragon XL that would ride to orbit on the Falcon Heavy booster. But even for this New Space darling, there’s not a lot of time to design, test, and build a brand-new spacecraft. To get the Dragon XL flying as quickly as possible, SpaceX is going to need to strip the craft down to the bare minimum.

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