Imagine you're an astronaut exploring the surface of Mars, when suddenly you fall ill or injure yourself. As your team struggles to get you safely back to base, you become seriously dehydrated. With their trusty -- and ingenious -- kit, the medical officer hooks into the drinking water supply, using it to create a saline solution that they can inject directly into your blood stream for quick and safe rehydration.

That's the idea behind the Intravenous Fluid Generation for Exploration Missions, or IVGEN, investigation that was conducted on the space station over five days in the spring of 2010. Since standard IV fluid bags used in hospitals would be too costly to send and hard to keep from spoiling on long-duration space missions, the ability to make fresh saline right from the drinking water supply could save the day in emergency scenarios.

Using the station's current recycled drinking water, the IVGEN investigation demonstrated that it is possible to produce medical-grade saline in space. Now, the focus has turned to the longevity of the IVGEN hardware and the shelf life of the solution produced.

"Basically IVGEN was a project to verify that, somehow, we could take potable or drinking water, purify it, and mix it to make a normal, medical-grade saline solution that could be injected into astronauts if the need arose," said John McQuillen, IVGEN principal investigator at NASA's Glenn Research Center in Cleveland, Ohio.

The IVGEN experiment relied on U.S. Pharmacopeia, or USP, guidelines for producing purified water and medical-grade saline. USP is the authoritative source for medicine and healthcare product standards.

Water from the station's Water Processor Assembly was fed through IVGEN hardware, where a series of filters removed air, bacterial contaminates, particulates, and heavy metals upstream of the heart of the system. The water then continued on through an internal deionizing resin, similar to that used in home water purifiers, removing the bulk of the minerals and organics. The experiment produced six 1.5 liter bags, or about 2.5 gallons, of purified water.

Two of the six bags were used to produce medical-grade saline. To do that, the purified water was added to a bag containing a premeasured amount of salt and a magnetic stir bar for mixing. The resulting solution then was transferred to the final collection bag through a sterilizing filter, which removed any additional remaining air and bacteria.

Once back on Earth, the two bags of saline were shipped to a Food and Drug Administration-certified lab to test whether the contents complied with USP standards. In the meantime, the hardware was placed on the shelf to undergo lifetime testing and ground studies until needed for a future mission.

"We are now wrapping up testing of the post-flight hardware. This testing was performed to see what we can learn from the current state hardware, as opposed to when it was initially launched," said Terri McKay, IVGEN project scientist at Glenn. "We are also testing the filters to make sure they can satisfy missions of multiple year durations. The pharmaceutical product shelf life needs to be documented, as well."

IV fluids have a shelf life of 6 to 18 months. The concern is not just with the saline itself. Other issues need to be considered, such as the possibility during the manufacturing process of the introduction of germs into the saline. There also are potential concerns with the IV bag, such as a punctured seal that could allow germs to get into the solution. There's even the chance that the bags themselves may destabilize over time and begin leaching chemicals or plastic into the solution. Once in space, damaged IV bags and saline cannot be replaced with a simple phone call to a distributor.

"As far as I know, there has not been much need for saline in past missions. However, if there is a need for medical care on the space station, the astronaut can be back on Earth in 24 hours. But if you're halfway to Mars, you can't just turn around," said DeVon Griffin, IVGEN project manager at Glenn.

Astronauts, particularly those on missions to distant locations, need access to a medical kit that meets their immediate needs. That includes having good saline at the ready. Flight doctors produced a list of more than 400 medical conditions they are concerned about treating in space. Of that list, 115 require saline, including severe burns, acute anemia and broken bones.

To satisfy medical requirements for long-duration exploration missions, a spacecraft could be required to carry hundreds of liters of IV fluid. Spacecraft planners can ill afford to surrender the mass and volume needed to carry that much liquid, which weighs 2 pounds per liter, according to Griffin. One NASA estimate is that a mission to Mars may need to carry as much as 248 liters of IV fluids, or about 65 gallons of liquid that may not even be used. That equals nearly 500 pounds of liquid consuming precious room and weight: weight that costs approximately $10,000 a pound just to get into space.

With operational limitations, such as launch mass, storage, and tight legroom on spacecraft, exploration missions need to minimize the amount of IV fluid they transport. Either that, or the mission will need the capability to produce purified water and saline in space. IVGEN may provide the answer, using a single filtration system capable of producing many bags of IV fluid via a device that is smaller than a single bag of ready-to-use solution.

The proposed design of the IVGEN hardware for exploration missions is pretty compact. With the exception of the accumulator, which plugs into the potable water supply to get the source water, everything else could fit inside a small laptop computer. It would be about 1.5 inches thick with a footprint of around 8 by 11 inches, making it a real option for solving the problem of saline supplies in space.