Last time we talked about using the Bigelow modules for our international space station replacement.
Today we are going to take a detailed look at the Bigelow modules specifically the Bigelow Expandable Activity Module (BEAM) which is scheduled to fly to the International Space Station (ISS) later this year with the SpaceX CRS-8 Dragon launch. Once it arrives at the station it will be removed from the trunk and attached to the station where it will be inflated to its operational size.
At present all the modules on the ISS are based on a fixed structure, on the US side of the station these were all launched in the cargo bay of the Space Shuttle and attached using a combination of the station and shuttles robot arms. As the name implies the new module is expandable, from it launch size of 5.7 feet long and diameter of 7.75 feet it will be filled with air and grow to 12 feet long with a diameter of 10.5 feet.
It is scheduled to spend two years attached to the station during which time tests will be performed to determine how it stands up to the rigors of space. Most of the time the hatch to the module will be closed, however the crew will access the module to perform additional tests. At the end of the two years the module will be detached and ejected into space where it will burn up in the atmosphere. Personally we would like it to stay on the station or be replaced by a bigger version at the end of the two years.
So why use an expandable module? The biggest advantage of an expandable module is the reduced size during launch, while launch vehicles are getting more powerful it still costs a lot of money to get vehicles into space, by reducing the size the costs go down too.
Why hasn’t this been done before? NASA originally planned to have an expandable habitat module, called TransHab, attached to the ISS. This was abandoned after congress banned NASA from continuing development due to raising costs. The technology was then purchased by Bigelow who have launched two independent un-crewed vehicles based on the design.
How does it work? Once the module is in space air will be used to inflate it to its full size, to allow this the outside of the module is made of a flexible material. The core systemsnneeded for the module are located in the middle with the rest of the expanded space available for the crew to work in.
But what about space debris and micro meteors? This is one of the biggest challenges faced by anything in space, to ensure the safety of the module and the crew inside the flexible material used for the outside of the module is made up of multiple layers. For the TransHab module the protection was designed with successive layers of Nextel, a material commonly used as insulation under the hoods of many cars, spaced between several-inches-thick layers of open cell foam, similar to foam used for chair cushions on Earth. The Nextel and foam layers cause a particle to shatter as it hits, losing more and more of its energy as it penetrates deeper. Many layers deep in the shell was a layer of super strong woven Kevlar to hold the module’s shape. The air was held inside by three bladders of Combitherm, a material commonly used in the food-packing industry. The innermost layer, forming the inside wall of the module, was Nomex cloth, a fireproof material that also protected the bladder from scuffs and scratches.
While we were not able to get too many details on the design on the Bigelow module we are assuming that most of these details are still accurate.
What next? While the BEAM module is only planned to be attached to the ISS for two years that isn’t the end of the story. Bigelow are already planning to launch there own modules some time after 2017 and we foresee this technology being used for more than just orbital stations. As we reach out further into the Solar System we are going to need vehicles that can provide adequate space for the crew to live as they travel.
These module are not just limited to space application either, there is no reason why it couldn’t be adapted for applications on the Moon, Mars and other destinations. The design would need to be slightly different as the fixed part of the structure would be placed on the ground and expanded above that. In addition as materials get stronger and stronger the structure of the modules will also get stronger and provide better protection to the crews as they travel.