Science in, garbage out. Every time a Cygnus or Progress cargo spacecraft brings up tons of experiments and equipment to the International Space Station, it stays around long enough for the astronauts to unload the new supplies. Then the spacecraft is refilled with tons of trash for a suicidal trip back through Earth’s atmosphere, where spacecraft and trash both burn up.
The routine is costly in terms of both money and astronaut time; it takes hours to finish all the loading and unloading, since every item must be carefully tracked. By some estimates, plastics account for about 20 percent of what’s thrown out on a typical mission. NASA has found ways to reduce waste, such as having astronauts drink recycled urine, but it will need even better ideas for trash disposal if the agency wants to send humans on long missions into deep space.
That’s why it’s funding a couple of promising ideas for trash disposal under the NASA Small Business Innovation Research (SBIR) program, which awards contractors up to $750,000 each for a two-year study. If they still look promising, the projects would be fully commercialized.
One of the ideas is to turn packaging plastic into raw material for 3D printing. The technology, called ERASMUS, takes Ziploc bags or any other thermoplastic waste, and transforms it into filament. Developed by Tethers Unlimited, ERASMUS is intended to be fully plug-and-play, with astronauts simply loading the container with trash, then walking away while it does its thing.
ERASMUS can even turn waste plastic into food-safe utensils for astronauts to use. Space station crews now clean their utensils and plates with wet wipes, according to Rachel Muhlbarer, additive manufacturing program manager for Tethers Unlimited. “Over time…if all you’re doing is wet-wiping [utensils] every so often, it is gross,” she says.
ERASMUS is now in Phase 2 of NASA funding, and in addition to testing the basic technology, they’re looking at how plastics degrade in microgravity. It’s not clear whether degradation happens differently in microgravity than on Earth, or whether the material will “outgas” differently—a potential problem given the station’s carefully balanced atmosphere.
Another trash-y idea currently receiving Phase 2 SBIR funding is a heat melt compactor developed by NASA’s Ames Research Center, in partnership with Materials Modification of Fairfax, Virginia. Earlier versions of the HMC suffered because water vapor could not be easily removed from polyethylene bags, which plugged the vents from compacting chambers and stopped steam from escaping. The HMC now uses a membrane bag to allow water vapor to escape, while keeping the solid waste generated during the HMC process.
In a separate project, Materials Modification is looking to improve cleanup on board the ISS. “We have also developed an antimicrobial, self-cleaning coating on surfaces to keep the NASA crew compartments clean and reduce the logistical burden of carrying a lot of wipes and cleaning supplies onboard,” said Kris Rangan, chief chemist of the company, in an e-mail.
If successful, both of the SBIR contractors plan to test their proposed technology on the station in coming years. The long-range goal is to develop cleaning and trash disposal ideas for use on NASA’s Orion spacecraft in the 2020s. That vehicle is headed for deep space, where Earth’s atmosphere won’t be available for use as a convenient incinerator.