Everything You Wanted to Know About BEAM but Were Afraid to Ask

8 04 2016

Humanity’s first human-habitable inflatable spaceship, (or as those in the industry prefer to call it, “expandable” spacecraft), is soon to launch off-world.  Tucked inside a Dragon cargo transport‘s “trunk” and perched atop a SpaceX Falcon 9 rocket, this momentous departure targets the International Space Station (ISS) and is slated to occur today.

The precious expandable cargo is itself a simple test article, (or as those in the industry are keen to refer to it, a “pathfinder technology demonstrator”), which was manufactured by Bigelow Aerospace right here in Las Vegas, Nevada.  Aptly titled the Bigelow Expandable Activity Module, or BEAM, the craft is designed to attach to the ISS and stay put for at least two years to see how it behaves.

Now, media outlets large and small, having caught wind of this impending technological departure from the streampunk-like status quo, (where hulking, submarine-like cylindrical pressure vessels serve as our spacecraft shells), are repeating the same, few details with great enthusiasm.  However, general curiosity about BEAM’s design, structural elements, and expected performance is going generally unanswered.

Well, no more.  There’s no question too big or too small to answer, here!  So, for the intrepid of spirit, I hereby present the following 5-point breakdown of Everything You Wanted to Know About BEAM but Were Afraid to Ask… (using public-domain material, of course.)

 

1]  What are BEAM’s pair of small, antennae-like protrusions for, anyway?

BEAM FRGFs

BEAM’s aft bulkhead antennae? (Original credit: Bigelow Aerospace)

While they might look like tiny, satellite-TV-style dishes, these circular devices serve a radically different function.  Known as standard Flight-Releasable Grapple Fixtures, or FRGFs, they’re the means by which the ISS’s robotic arm will snare BEAM, yank it out of Dragon’s trunk, and plug it on to the ISS’s Node 3 module.

FRGF_on_Cupola

A Flight-Releasable Grapple Fixture, or FRGF, a necessary grip point for the International Space Station’s robotic arm. (Credit: NASA)

NASA provided Bigelow Aerospace with two FRGFs to install on BEAM as part of their contract.  Think of them as the receiving half of an enormous robotic handshake upon BEAM’s arrival at the ISS.

 

2]  What about the sleek, wavy metal collar on the ‘hatch’ side of BEAM?

BEAM PCBM

Sleek style or something more? (Original credit: SpaceX)

As it turns out, this eye-catching part of BEAM’s exterior was manufactured by the Sierra Nevada Corporation and is known as a Passive Common Berthing Mechanism, or (you guessed it), a PCBM.  This is a standard mechanism for unpowered craft that can’t dock to the ISS using their own thrusters and must therefore be snatched up by the ISS’s robotic arm and manually ‘plugged in’ to one of the station’s active ports.

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A Passive Common Berthing Mechanism, necessary for forming a tight seal with the International Space Station. (Credit: Sierra Nevada Corporation)

The PCBM was supplied to Bigelow Aerospace by the Sierra Nevada Corporation as part of the NASA BEAM contract, and it was integrated into BEAM’s structure at Bigelow’s large North Las Vegas facility.

 

3]  So, what are BEAM’s walls actually made of?

BEAM softgoods

What makes sturdy spacecraft skin that can also crumple and fold for launch? (Original credit: Bigelow Aerospace)

Bigelow hasn’t released the specifics of the makeup of BEAM’s fabric walls, known as “softgoods.”  (Holding this extremely proprietary information close to the vest is unsurprising.)  However, despair not, curiosity-fueled space enthusiasts, for it turns out that much basic information about the Bigelow expandable spacecraft approach was published in a 2005 article in Popular Science, entitled, “The Five-Billion-Star Hotel.”

In the article, the walls of the expandable Bigelow “Nautilus” module under development at the time (later to be rechristened the B330 spacecraft) were described as having the following basic structure:

  1. “Five outer layers of graphite-fiber composites separated by foam spacers” that function as a micrometeorite and orbital debris (MMOD) shield.
  2. Moving inward, this is followed by a critical, intermediate layer known as the “restraint layer,” which serves as the load-bearing portion of the structure.  This layer is described as “a web of interwoven straps made of high-strength fiber.”
  3. Finally, the innermost layer, called the “air bladder,” is a “plastic film” that “keeps the internal atmosphere from escaping into space.”

Admittedly, it has been some time since the article was written, and details may have shifted somewhat in the intervening years.  -But, in a general sense, BEAM could be reasonably expected to follow the same sort of structural format.

For something a little more recent, one can also argue for a fairly close approximation of BEAM’s softgoods in another, modern inflatable spacecraft design.  European aerospace titan Thales Alenia Space (TAS), (responsible for the design and manufacture of the rigid shell backbones of the European Space Agency’s Automated Transfer Vehicle supply ships as well as the Cygnus cargo freighters, and others), has its own inflatable spacecraft design known as REMSIM.

REMSIM

A 2005 rendering of a REMSIM inflatable module, envisioned as a lunar habitat. (Credit: Thales Alenia Space)

Just as BEAM could be considered offspring of the cancelled NASA TransHab program, from which it inherited much of its technology and approach, so too does REMSIM descend from TransHab, making it a sort of European cousin to BEAM.   Standing for “Radiation Exposure and Mission Strategies for Interplanetary (Manned) Mission,” REMSIM was effectively the European Space Agency’s push (like Bigelow) to carry the TransHab torch into the 21st Century.  (REMSIM research and development is ongoing to this day.)

In landmark 2009 research presented at the International Symposium on Materials in a Space Environment, led by TAS researcher Roberto Destefanis, the REMSIM layers are revealed (and put through their paces).

Screen Shot 2016-04-08 at 7.15.18 AM

Softgoods layering details of the inflatable REMSIM spacecraft, a European cousin to Bigelow Aerospace’s BEAM. (Credit: Destefanis et al., 2009)

In the above diagram, MLI stands for Multi-Layer Insulation (think heat shield), BS stands for Ballistic Shield layer, and the rest are as described.  As can be seen, they generally agree with the Popular Science description of the Bigelow approach.

So, odds are, if you want to know what’s inside BEAM’s collapsible/expandable spacecraft skin, the REMSIM “stack” isn’t a bad place to start.

 

4]  Can BEAM really shield well against micrometeorite and orbital debris strikes?

BEAM MMOD

Will BEAM’s soft sides stand up to space impacts? (Original credit: NASA JSC)

When many are introduced to the concept of an inflatable spacecraft, a natural first reaction is alarm.  On Earth, most inflatable objects are very vulnerable to punctures and ruptures (e.g., party balloons).  Wouldn’t an inflatable spacecraft be far more vulnerable than rigid aluminum modules to micrometeorites and bits of space junk zipping around at mind-bending orbital speeds?

Well, much like a Kevlar vest has no problem stopping a bullet, it turns out that expandable spacecraft have no problem holding their own against impinging space chunks.  While specific information on how well BEAM’s softgoods hold up under punishment is proprietary, we can return once again to REMSIM for a good example.

IMG_2980

The aftermath of a micrometeorite impact test on a BEAM-similar expandable spacecraft design known as REMSIM, demonstrating that the inner layer remains unscathed. (Credit: Thales Alenia Space)

The Bigelow debris shielding approach, like REMSIM, uses what is called a Multi-Shock strategy.  Here, multiple thin, ballistic shield layers separated by some distance act to “shock” the incoming projectile and disperse its energy before it strikes (and potentially breaches) the pressure containment layer.

So, again returning to the 2009 Destefanis paper, REMSIM softgoods test articles boasted surviving getting blasted with half-inch aluminum spheres at speeds exceeding 15,000 miles per hour.  (This agrees with claims made in the aforementioned 2005 Popular Science article, which reports that Bigelow softgoods withstood a half-inch aluminum sphere impacting at better than 14,000 miles per hour.)  Not too shabby at all, and according to the research, meets or exceeds the debris protection performance of rigid ISS modules using traditional “stuffed” Whipple Shields.

This implies that BEAM’s protection factor against micrometeorites and debris is just fine, if not outright superior to rigid modules.

 

5]  What sort of radiation protection should we expect from BEAM?

BEAM Rad

This has been a big question, and one NASA has expressed particular interest in.  In fact, it’s one of the primary functions of BEAM to determine just how favorable the radiation protection qualities of a softgoods spacecraft are.

The problem with space radiation is that it is generally more massive and highly energetic compared to ionizing radiation encountered on Earth’s surface, which makes it difficult to shield.

The problem with talking about space radiation shielding is that it depends on a boatload of variables — the more active our Sun, the more it deflects even more damaging radiation from exploding stars in our own Galaxy (and beyond) but trades it for an increased risk of being hit with lower-energy but overwhelming solar storms.

tumblr_o53txgrsvO1tnfmy1o1_1280

Artist’s depiction of solar and cosmic radiation at the fringe of Earth’s magnetic field. (Uncredited)

Blanket statements about how anything shields radiation in space are therefore difficult to reliably make, requiring multiple models and depending strongly on orbit altitude, timing, and precise material breakdown.  As a result, experts tend to either sound uncertain or evasive.

Keeping all of this in mind, if we return to the 2009 Destefanis study one final time, we find it has something to say about this as well.

By placing test articles meant to represent different types of spacecraft and spacecraft materials in front of particle accelerators powerful enough to fling atoms as large and fast as those fired into the cosmos by exploding stars, researchers can reliably predict how materials will shield against space radiation.  This is exactly what the Destefanis study reports, using an iron-atom slinging accelerator at Brookhaven National Lab.

Screen Shot 2016-04-08 at 10.01.10 AM

Expected shielding performance of BEAM-like REMSIM compared with varying thicknesses of different materials and ISS module compositions. (Credit: Destefanis et al., 2009)

The results of the Destefanis work reveal that against the most damaging type of radiation experienced at the ISS (heavy Galactic Cosmic Rays), REMSIM shields nearly half as well (3%) as an empty ISS module (8.2%).  It achieves this with less than a third of the equivalent mass, demonstrating a pound-for-pound benefit in REMSIM’s favor, not to mention the unprecedented capability of squeezing into a tiny payload space during launch.

In a big-picture sense, the chart also reveals that REMSIM shields only 10% as well against heavy GCR as a fully-outfitted ISS module (3% versus 28.7%).  While this might sound terrible at first glance, this is due largely to the fact that Columbus is currently far from empty, ringed with equipment racks, piping, tubing, cabling, and supplies.  All of this extra material serves as supplemental shielding for astronauts located within.

By contrast, the basic REMSIM in this study is (like BEAM) completely empty, making the “10%” claim a somewhat unfair apples-to-oranges comparison.  However, numbers like these more closely match the current situation between BEAM and the rest of ISS.

So, ultimately, if the REMSIM-BEAM comparison holds, one might expect a similar ratio between GCR-radiation shielding measurements made in BEAM and parallel readings taken across the rest of the ISS.  And while the numbers might sound grim to the uninitiated, numbers like these are going to be exactly what NASA is looking for.

_________

I hope the information compiled in this post has been helpful at least to some, and as always, feedback is welcome.

Semper Exploro!

 


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11 04 2016
Everything You Wanted to Know About BEAM but Were Afraid to Ask — Astrowright | robert's space

[…] via Everything You Wanted to Know About BEAM but Were Afraid to Ask — Astrowright […]

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