Bigelow’s Bulletproof BEAM – NASA’s Bet Against Space Debris
North Las Vegas, NV. — It was only a matter of time before Bigelow Aerospace won its NASA contract. The North Las Vegas, NV-based company has enjoyed great, but under-reported success with its Genesis I and II Transhabs, which have been orbiting the Earth, unoccupied, since 2006 and 2007. Since then, both have logged years of smooth, well-monitored spaceflight. Yesterday President Robert Bigelow and NASA Deputy Director Lori Garver announced that Bigelow’s BEAM (Bigelow Expandable Activity Module) module will launch on a SpaceX Falcon in 2015 to become the first fabric-skinned module to be attached to the International Space Station – unless you count space-walking astronauts.
Garver and Bigelow had met just ten months earlier to sketch out the idea. That ink is now put to the $17.8 million contract represents relatively swift action on NASA’s part, indicating increasing cooperation between the space agency and private space companies like SpaceX and Bigelow. The module will remain attached to ISS for two years. It is not, like other modules, slated to house particular experiments, though with Genesis I and II Bigelow has experience providing microgravity science laboratory space.
Ultimately the crew will decide what to do with the extra space, but they’ll find it at once comfortable and, because it doesn’t vibrate like the aluminum-shelled exterior of the rest of the ISS, it will be the quietest part of the Station. Whatever else it houses, BEAM seems destined to be the preferred makeout spot on ISS; maybe the first true makeout spot in space, though one is always suspicious about Mir.
NASA’s swiftness was no doubt driven by another sort of urgency. The problem of space debris isn’t an abstract scenario for the ISS. Twice in recent years, in April 2011 and January 2012, the Station has had to maneuver out of the path of fragments closing on it at incredible speeds. There are some 9000 fragments of debris, ranging from entire discarded probes to small fragments, left over from thousands of launches since the beginning of the Space Age. The potential danger posed by these MMODs (Micro Meteroid Orbital Debris) is quite fluid, and can be made much worse by a single accident. Such was the case on February 10, 2009, when the 10 February that year, the Russian satellite Kosmos 2251 crashed into the American communication satellite Iridium 33’s solar panel. Kosmos 2251 completely disintegrated; Iridium 33’s panel shattered like a mirror.
Ten percent of all space debris derives from this one catastrophe, which smeared LEO with over 2,000 fragments larger than 10 centimeters, and likely over a hundred times as many smaller fragments that can’t now be tracked. A 2007 Chinese missile strike on one of its own satellites left an additional 3000 fragments.
The danger they pose is such that NASA has dedicated an office to the task of identifying and tracking each dangerous micro-meteroid.
Bigelow modules’ inflatability is not, in itself, a particular improvement over conventional aluminum skin. NASA and inflatable spacecraft go back together as far as Echo I and Echo II in 1960 and 1964. Though their skins were made for bouncing radio waves, not meteoroids, the Echoes were not simply passive targets. The gas that filled the “satelloons” was laced with just-evaporated liquid and just-sublimated crystals, so that it would coagulate around most tiny micro-meteoroid punctures. Still, Low Earth Orbit is much more abuzz with debris than the Low Earth Orbit of the early ‘60s. Asked why NASA ever gave up on inflatables in the first place, Ms. Garver – who wasn’t around at the time – thoughtfully speculated, “I would guess materials might have been the problem.”
The materials for BEAM resemble Kevlar, operating on the same general theory: a thatched interweaving of strong fibers, designed to wrap around an intruding projectile is, from an engineering standpoint, a much surer means of stopping that project than simply presuming to put up a wall strong enough to deflect the projectile. Further, Kevlar and its cousin depend upon layering, a lightweight technique used to stop projectiles at least since the Mongol warriors.
Robert Bigelow described the BEAM’s skin as several layers dedicated to debris resistance surrounded by a water layer on the inside and an outer-most, essentially thermal layer.
The water-filled layer is thought to be particularly radiation-resistant, lending resistance with somewhat less thickness required than with other, hard materials. The theory of water’s use against radiation particles is somewhat similar to that being used by Kevlar-type layered cross-thatching against fragments: it is most effective when there’s a degree of “give” when the projectile hits. The BEAM skin’s effectiveness against radiation will be carefully monitored throughout the two-year mission, but here it is useful to remember that Bigelow’s skins have already racked years of success from Genesis I and II.
Low Earth Orbit might be a thicket of fragments, but it is largely protected by the Earth’s magnetosphere against the worst of space radiation – cosmic rays from beyond the solar system, made of massive, highly charged particles. It is believed that no material shielding will be adequate protection against cosmic rays, especially over the long durations necessary for deep-space missions. Perhaps other measures ought be considered.
Article by Todd Jackson