The rise of inflatable space structures

6 September 2010 | By Ellie Zolfagharifard

Lightweight inflatable structures are set to play a major role in future space exploration.

When holidays to the Moon become a reality, most tourists will probably hope that there will be something more than a soft, inflatable tent to come between them and the deadly vacuum of space. But that is exactly the vision the European Space Agency (ESA) and NASA have for space accommodation in the coming decades.

Their concept is to develop inflatable habitats that could allow people to live on the Moon by 2025. The inflatable modules could act as an outpost where supplies would be kept for research missions or they could be made into larger structures to house space tourists. If their plans are successful, inflatable habitats could open up a whole new world of exploration and, according to the ESA, make visiting distant planets a reality.

Gary Spexarth, manager of lunar surface systems design at NASA, believes that, despite their appearance, current inflatable habitats are far better suited than metal structures to the harsh environments of space. ’You could think of these inflatable modules as a big spacesuit,’ he said. ’The fabric is extremely tough and durable, but also designed to be as lightweight as possible. Unlike rigid metallic structures that can shatter or bend if hit by a micrometeorite, flexible material is able to recover to a certain extent.’

The idea of inflatable structures has been around since the early 1960s, when NASA commissioned tyre manufacturer Goodyear to build an inflatable space station. It hoped to solve the problem of sending large objects into space by creating a lightweight system that could be flown to the Moon and later inflated. Goodyear’s resulting prototype resembled a large inner tyre big enough to house two people, but owing to insufficient funding and a number of design flaws, the concept never got off the ground.

Instead, it lay dormant until the 1990s, when NASA started exploring how to build living quarters for human missions to Mars. An inflatable design by William Schneider, the then senior engineer at the Johnson Space Center, was proposed. Unlike Goodyear’s rubber design, Schneider used an airtight bladder surrounded by Kevlar straps that could absorb impact by micrometeorites. The design culminated in the Transhab project, aimed at providing living quarters on the International Space Station (ISS), but in 2000 the project was scrapped by Congress.

Doing the rounds: Goodyear tried to build an inflatable space station in the 1960s

Since then, NASA and ESA have both quietly been working on separate projects. Scott Hovland, head of human systems at ESA, claims that astronauts will soon need these structures if they are to carry out more distant missions. ’We’re keeping an eye on developments in space tourism, but as well as that we have a clear roadmap of sending humans to explore places that are currently being done by robots. We need to make sure all the technologies are available by that point. The problem we have is that we are still constrained by the weight our launch vehicles can carry up.’

According to NASA, for every pound of cargo that lands on the Moon, it will need to launch 125lb (57kg) from Earth to cover fuel, engines and systems for the journey. Launching folded fabric into space would provide more usable volume for the amount of mass compared with metallic structures. In theory it is an ideal solution, but it comes with its own challenges. ’Something that people don’t really think about is just the challenges in folding it,’ said Spexarth. ’It’s almost like a wet towel; it doesn’t always go the way you want it to go. And knowing the dynamics once it’s inflated in orbit is also very difficult to do with computers and to test on the ground.’

The question we’re struggling with is: should NASA develop one first or should we turn the development over to private enterprise?

Gary Spexarth, NASA

NASA has attempted to test some of the structure’s integrity using extreme environments on Earth. In 2007, it assessed how easy these inflatable habitats were to deploy and how durable they were in the harsh environment of Antarctica. While the results of these tests proved valuable, NASA admits that any space project that has a human element will carry extensive testing in space prior to launch. However, as the economic crisis lengthens, governments are finding it harder to fund space programmes. In response, NASA has turned to commercial enterprise to further develop its concept.

’Going commercial can definitely help with the funding issue,’ said Spexarth. ’But one thing that within NASA we’re trying to understand is: at what point does that make sense? The world has been launching rockets now for 50 years and we’re only just getting comfortable with turning that over to a commercial entity. With inflatables, it’s a completely new technology. The question we’re struggling with is: should NASA develop one first or should we turn the development over to private enterprise?’

A promising candidate is US company Bigelow Aerospace, which was founded by real-estate tycoon Bob Bigelow to develop inflatable extensions for the ISS. In 2004, Bigelow acquired the licences to NASA’s Transhab programme and has since successfully launched the Genesis I and II inflatable test craft. It now hopes to launch an 180m3 spacecraft called the Sundancer while looking at the possibilities of creating an inflatable Moon base. Bigelow’s work has far exceeded what others have been able to achieve in the field, largely thanks to the massive amounts of private funding. The company also recently announced that it is working with Boeing on the development of a commercial space-station system.

Creating the interfaces, such as the exits and entrances, will be quite a difficult engineering problem

Mark Butler, Aero Sekur

In comparison with the US, Europe is taking a more conservative approach. It has not yet launched an inflatable habitat into space or engaged as fully with the private sector. Despite this, work is progressing gradually, and one partnership that has proved successful is that between Anglo-Italian space material companies Aero Sekur and Thales Alenia Space Italia, which have conducted research into inflatable habitats for ESA. The collaboration has so far resulted in a basic inflatable module and the team is now working on the next stage of making it into a practical environment.

’It’s all very well producing an inflatable balloon but if people are going to live in it you have to start thinking about other issues - in particular that of interfaces such as the exits and the entrances - and that’s quite a difficult engineering problem,’ said Mark Butler, Aero Sekur’s chief executive. ’For instance, if you put them on the circumference, you have to start dealing with high hoop stresses and model those. We also need to look at how to inflate these modules and how to pack them and, where possible, use regenerative life-support systems. It’s a tough engineering problem, but we’re getting there.’

ESA is planning to call for ideas from industry and academia in September for the design of an inflatable habitat, which it expects to go into space between 2020 and 2025. President Barack Obama wants an inflatable module up in the ISS by 2015 and NASA expects this could be as soon as 2013 if funding is secured. Meanwhile, Bigelow is continuing to work and expects to launch the Sundancer into low Earth orbit by 2014 in order to test the concepts of launching, inflating and living in an inflatable habitat.

The timescales may seem ambitious, but with humankind’s insatiable desire to explore and commercial drive boosting efforts, the possibility of renting a place on the Moon may come sooner than we think.

Rice on Mars
A novel portable greenhouse tent could enable agriculture in space

Aero Sekur has developed a prototype inflatable habitat for space agriculture that could allow the first astronauts landing on Mars to grow their own food.

In March this year, the company announced its plans to grow mustard seeds on the Moon, riding aboard the Odyssey Moon Lander mission, a commercially led lunar mission aimed at winning the Lunar X-Prize, scheduled for launch in 2012. Mark Butler, chief executive of Aero Sekur, said: ’We’re going to be at least one greenhouse up on the next European mission and we’re working with astronauts to develop the right type of system.’

According to the company, space agriculture will be a vital part of colonising distant planets such as Mars. The portable greenhouse could augment astronauts’ diets on long missions or one day allow them to become self-sufficient.

http://www.theengineer.co.uk/the-rise-of-inflatable-space-structures/1004721.article

Дата добавления: 2015-08-03