Inflatable space technology definitely passes the pub test - that is, it's interesting enough that you can get away with telling your friends in the pub about it, without losing all your friends. In fact, whenever I mention inflatable technology to the general public, they tend to react in the same way:
And it's probably to be expected, as the vision of floating around deep space in a giant party balloon is perhaps an interesting, albeit terrifying, one. However, inflatable technology may be a very real part of the future of spaceflight, both for deep space craft and preliminary colonies on other bodies like the Moon and Mars.
The problem, in general, in human spaceflight is that engineers like small and light spacecraft that can be launched easily and cheaply. Astronauts, on the other hand, prefer room to move, breathe and sometimes even windows to see out of their ship.
All this extra space requires extra structure, most commonly aluminium, which is heavy and therefore extremely costly to launch. To give this idea some perspective, the estimated cost to launch material to Low Earth Orbit (a mere 400km away) can be anywhere from $5,000 to $20,000 per kg depending on if you choose to use a SpaceX Falcon 9 or ULA launch, respectively. It is easy to understand how quickly these costs can mount when engineers are forced to accommodate the fact that astronauts have to move and exercise in space. And as we venture further into space, towards Mars or beyond, the journeys get much longer (approximately 6 months for a typical chemically-driven mission to Mars) and so astronauts require more room to function.
Not only this, there is also a firm limit of the size of traditional module we can launch into space, which is set by the fairing of the launcher selected.
Inflatable technology solves many of these issues and many more by allowing engineers to launch a compacted structure through our thick atmosphere in a traditional rocket before inflating in the vacuum of space to provide additional volume with huge mass- ,and therefore cost-, saving benefits.
Are inflatables safe?
It may seem counter intuitive but inflatable technology can actually be safer than regular, aluminium modules.
One of the most severe dangers for a crewed orbiting spacecraft are micrometeorite and space debris impacts.
Micrometeorites are minuscule particles which fly through space at phenomenal speeds. Due to the vast velocities involved in orbit, (the International Space Station (ISS) travels at an astonishing speed of 28,000 km/hr) even the tiniest fleck of paint can become a devastating projectile in orbit.
Fortunately, the ISS is heavily shielded by to prevent catastrophic collisions that would lead to rapid de-pressurisation and death to all on-board. You may think the best way to shield against a fleck of paint or a lump of metal hurtling through the vacuum of space is to put a giant lump of solid material in between you and the debris. Well, actually that's not the case.
Check out this lump of solid alumnium (left) that was destroyed by a penny-sized projectile travelling at orbital velocities! The problem with this idea is that the entire force of the impact is concentrated on one spot, and as you can see, this can easily cause some serious damage.
A much better tactic is to use Whipple Shielding. There's no need to delve into details here but it should suffice to say that whipple shielding is generally formed from layers of metal plates stuffed with kevlar and minuscule gaps between, in order to spread the initial impact over a larger surface area and thus reduce impact energy. You can read more about these here.
Now, inflatable space habitats also just happen to made up of many (often upwards of 36) layers of kevlar, nextel which makes them great at absorbing micrometeorite impacts. Inflatables also have the added advantage that they are cross-weaved, which means that in the very unlikely event that the inflatable is punctured, the spacecraft will maintain its integrity and allow astronauts to perform a plugging maneuver from the inside! Exactly like patching a puncture on your bike tire.
Where will we use inflatable technology?
I'm glad you asked! There are many locations where the use of space inflatables has been widely studied. In fact, I predict they will be used in almost every aspect of our deep space human exploration.
Deep Space Tourism
Robert Bigelow, founder of Bigelow Aerospace, is perhaps one of the less known of the eccentric space billionaires. But nevertheless his company has been making leaps and bounds in the future of space tourism - thanks in part to a clever list of exclusive patents they have held on certain space technologies since the early 2000s.
Mr Bigelow made his fortune as a Nevada hotel tycoon and now wants to expand his empire into Earth orbit and beyond. That's right, he plans to open the world's (or Solar System's?) first space hotel and he plans to utilise the benefits of space inflatables to do so.
These ideas are no longer confined to the realms of science fiction. The company has already space-tested a module named BEAM (Bigelow Expandable Activity Module); an experimental inflatable module with dimensions of approximately 4.0 m by 3.2 m.
BEAM arrived at the International Space Station (ISS) on the 16th of April 2016, and was expanded and pressurized on May 28th, 2016. Below is a timelapse that shows the expansion of this module on the side of the ISS.
BEAM is an incredible achievement and in my opinion, is likely the start of a new era of spaceflight. However, there's no getting around the fact that BEAM is quite a small module.
The scale of an empty BEAM is seen on the left, as NASA astronauts perform a checkout. And this is before any of the fittings have been added - i.e a completely empty module. So just how big can these things be? Well, according to Bigelow Aerospace, pretty enormous.
Yeah, enormous. The BA-2100 is still just a conceptual design right now but sits at around 70 tons, and holds a 2,250 cubic metres of pressurised atmosphere - that's more than double that of the entire International Space Station!
Needless to say, this concept is likely a few years off - at least because it's so big that it will need to use SpaceX's Super Heavy Rocket (previously BFR) or NASA's Space Launch System Block 2, neither of which will be ready for launch for several years.
Either way, the power of inflatable space technology is seemingly limited only by our ability to fold the thing small enough to launch!
Due to it's vast distance (385,000km) and the associated costs of landing multiple heavy payloads there, the Moon is an obvious destination for the future of inflatable technology. In 2012, architectural firm Foster & Partners entered into a partnership with ESA to design an inflatable habitat for the use of the Moon. You can read the full design here.