• January 16, 2013
• By Shawn Wright

Much like on Earth, waste is a problem in space.

But unlike life on the blue planet, humans floating above don't have a curb, bin or dumpster for their refuse.

Astronauts on the International Space Station store their trash until other space vehicles bring supplies. The supplies are unloaded and the waste, wrapped in the shape of a little football in transparent plastic with silver duct tape, is then placed on the supply vehicle and brought back to Earth. The waste is also sometimes burned up during re-entry.

This conundrum for dealing with space waste is one reason for NASA's Logistics Reduction and Repurposing (LRR) project, which began in late 2011. The project's aim is to improve space missions by reducing the mass and volume of consumable items, finding ways to repurpose waste and reducing trash created during the mission.

Prior to the project, NASA hadn't dealt with handling its waste in an all-encompassing platform.

"There wasn't a big emphasis on what went up because we had the capability to bring it down," said James Broyan, Advanced Exploration Systems logistics reduction project manager at NASA's Johnson Space Center in Houston. "As we were looking for missions we might supply and they go somewhere, then how do you reuse things? As the mission progresses, you need more space for that vehicle. If you can reuse things over time, we may be able to increase the volume of the vehicle by repurposing items."

Broyan has co-authored a report detailing four waste reduction projects. It involves six NASA space centers and has four major tasks to develop different technologies to fulfill the Advanced Exploration Systems' LRR goals and will result in engineering units or prototypic hardware.

In particular, the project is being used to determine the most effective use of waste to support the International Space Station for 10 more years in low-Earth orbit.

"When people design long-term space missions, they want to be able to do something with the trash. They don't want to have to use up volume for storing trash," said NASA chemist Paul Hintze. "Second thing: Trash can smell. The third thing is if you have microbiological activity in the trash, you really want to minimize that. One advantage, in addition to producing something, is just getting rid of the trash."

In a study on the waste stream from four shuttle missions, NASA found personal hygiene waste accounted for 50% of total trash and 69% of the total water; drink items were 16% of total weight and 16% water; food wastes were 22% of total weight and 15% water; and office waste and plastic film were 2% and 11%, respectively, with no water.

Shrinking waste and reducing the water is one important component of the LRR project.

Extreme compaction

On a one-year mission with four crew members, the estimated total food-related waste would be more than 8,600 pounds. Total accommodations, such as disposable clothing, paper and body towels, would account for about 5,200 pounds. That's a lot of weight to launch and store in a spacecraft.

To help process both wet and dry waste, NASA created the Heat Melt Compactor. In the machine, waste is heated to 320 degrees Fahrenheit and can be compacted into discs that are roughly eight inches in diameter and about one inch thick.

The compactor also heats trash to dry it, sterilize it and melt any plastic. If the refuse placed inside contains more than 20% plastic, the machine will compact and melt it to form a solid rigid tile that does not expand.

The compressed trash is then cooled and the waste tile is removed. Besides shrinking trash's volume, the trash tile has a dual purpose: a shield that may protect astronauts from solar flares and radiation.

NASA is working on a next generation design that will turn the trash disc into a 9-by-9-inch square with some rounded corners.

"There's some discussion of would you have something that's just deployable in case you have a solar event or would you shield some portions of the spacecraft they spend a lot of time in, like the crew quarters?" Broyan said. "That's what we do on the [International] Space Station is we have dedicated shielding in the four U.S. crew quarters."

The tiles would have multiple layers that are offset. Even if the tiles still had rounded corners, the next set of tiles would cover it. The whole spacecraft wouldn't be shielded with tiles, Broyan said, only a portion to protect the astronauts.

The tiles would evolve over the course of a space mission. Early on, there wouldn't be any. But as the mission progresses, the accumulating waste would be converted into tiles.

"Initially, you have all supplies, maybe not much dedicated shielding, and then the heat melt compactor helps convert some of those supplies to dedicated shielding," Broyan said.

The LRR project is considering reusing the spacecraft's cargo transfer bags to hold the tiles. The bags' first use is to keep items organized during orbit. The bags are then used to store and transfer dry trash. Often, the bags themselves become trash if they do not have a second purpose.

NASA also is determining how these bags can be reused for possible crew items such as habitation partitions, acoustical liners, furniture or a placeholder for the radiation shielding tiles.

"If you make one to three tiles per day, you would fill up the pockets," Broyan said. "Then you would deploy that as a radiation-shielding partition. Whether you put that against the [space craft] shell, in front of a cargo rack or inside your crew quarters is yet to be determined."

Space waste-to-energy

For the last year, Hintze and his crew at the Kennedy Space Center in Orlando, Fla., have been working on NASA's Trash to Supply Gas project, another piece of the LRR.

During the project planning phase, Hintze and his staff identified a few trash-processing technologies already used at Kennedy Space Center, Glenn Research Center and Ames Research Center, deciding on the ones they wanted to pursue.

Six waste-conversion technologies were selected — pyrolysis, gasification, combustion, ozonation, catalytic reduction and steam cracking. Hintze said they will eventually select one or two of the technologies to develop further, with the ultimate goal of having a flight unit out in space in the near future.

"They all have their advantages and disadvantages," Hintze said. "What we've been kind of focusing on is methane production. You can get other things out of the trash like water, oxygen and other products. One technology may be the best for methane production, while another technology may be better for something else."

He hopes to have a suite of technologies available.

"If somebody came in and said they wanted water, we could give them water. If they wanted methane, we could give them methane," Hintze said. "It'd be great if it was just one thing that could do everything, but it may not be."

Technologies such as pyrolosis, gasification and combustion being considered for the trash to supply gas project are already used on Earth. But what works on the third rock from the sun doesn't necessarily translate to the confines of a space station or shuttle.

"You have to make sure that because it's going to be operated in a closed system, anything toxic, hazardous or really unpleasant does not get out," Hintze said. "You can't have the astronauts be around even something that smells bad. They live in a closed system, so if the technology releases noxious odors, you just can't have that."

The long-term goal is closing the life-support loop.

"Anything in the trash, you can use those elements, the atoms in it, and make new molecules that are useful for something else," Hintze said. "When it comes to rocket propellant, if you estimate how much methane you can produce in a year from a crew of four if you were on a lunar base, the methane produced from the trash could supply one lunar ascent vehicle per year."

A lunar ascent vehicle is the rocket that would leave the moon and take people or items back to Earth, which would make launching anything from Earth easier and less expensive.

But ease of use must be considered.

"We have to think about how much effort it's going to take for an astronaut to operate the technology," Hintze said. "Is it the same as throwing trash into the trash bin or will they have to do many kinds of hands-on things? Those are things we really have to think about because the astronauts' time is very valuable."

The technological problem comes from something more commonly and easily done on Earth — separation of the waste stream such as food, plastic and paper, human waste and clothing.

"Unlike some of the terrestrial technologies, where they take one feedstock, we're looking at all the waste going in the there," Hintze said. "That's a challenge."

Space clothes

Reuse is another facet of improving waste in space. The LRR's Advanced Clothing System project looks at ways to create astronauts' clothes from polymers instead of cotton-based materials. Clothing accounts for a significant portion of the weight launched on space missions. And when clothing gets too dirty to wear, it is discarded because there is no space laundry or dry cleaning available.

There are a couple advantages to having clothes made of polymer rather than cotton-based fabrics. First, antimicrobial coatings combined with high-wicking and low-moisture retention should allow the clothes to remain odor-free longer.

The other upside is it will decrease the weight on shuttles and reduce the disposal burden. Fewer clothes per mission mean more room for other items.

"If the crew can wear it longer, then you need to fly less clothing for a mission," Broyan said. "The other benefit is if we're looking at advanced clothing, a lot of them are polymer based, those work well with the heat melt compactor or with the trash to supply gas technologies."

Use on Earth

NASA technology has a history of deviating from its intended purposes and spinning off into Earth's orbital market.

Items we use every day, such as invisible braces, scratch-resistant lenses, memory foam, ear thermometers, shoe insoles and water filters, spawned from NASA inventions. In fact, NASA has filed more than 6,300 patents with the U.S. government, according to NASA Scientific and Technical Information.

The LRR project could have many implications on how we handle waste on Earth. For example, the Heat Melt Compactor could make sense for municipalities.

"Transportation costs are a large portion of recycling here on the ground," Broyan said. "Plastic bottles and stuff aren't very compact. I know they do mechanical compaction, but if you had a waste heat source you could soften and make more compact trash, that might be advantageous to municipal sources as well."

The U.S. military also is interested in the trash-to-supply-gas technology because troops are often on remote bases and always need fuel. If trash can be converted into fuel or electricity, it would be beneficial.

"The same thing goes for any remote location or underdeveloped country; you can process waste products and get something useful from them," Hintze said. "That is definitely something that will affect us here on Earth."

Packaging materials also could gain from the LRR's project, taking a page from the cargo transfer bags that can be repurposed into partitions for walls or other items.

"There's been a push toward minimizing packaging material and having green packaging," Broyan said. "Packaging materials could be something people could use afterward, and certain products are moving along in those directions. [It's about] getting people to consider [reuse] at the beginning of the product, think about what you do after it's served one purpose."

 

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