"It's a magical place," Ferguson said of space, describing how a sunrise came every 90 minutes - the time it took to orbit the Earth - during his November trip to the International Space Station.
Among Ferguson's duties on his second shuttle mission was delivering lots of gear to the station, such as the urine processor, and the 16-day effort was deemed a success.
Yet it came as the space program is in transition, with the last shuttle flight now planned for next year.
In 2004, President George W. Bush called for a new mission to the moon, which would be used as a stepping stone for an eventual journey to Mars.
If that remains a goal for the Obama administration - and no change has been announced - there are technical challenges ahead.
Conventional engines would be hard-pressed to propel a rocket to the red planet because of the staggering amount of fuel required in proportion to the rocket's weight, Ferguson said.
"We're as good as we can get with an internal combustion engine, and it's not good enough," Ferguson said.
Afterward, he said one option is called VASMIR - Variable Specific Impulse Magnetoplasma Rocket - a technology developed by Ad Astra Rocket Co. of Webster, Texas.
In a telephone interview, company research director Jared Squires said the concept relies on radio-frequency power to expel superheated gas out of a magnetic nozzle. The company recently signed an agreement with NASA to test the technology aboard the space station in 2012.
Ferguson said if the goal was to reach Mars, it made sense to use the moon as a preliminary proving ground.
"If you have a problem on the moon, you can come home," he said. "If you have a problem on Mars, you're stuck."
Another puzzle in reaching Mars is predicting how the human body will react to such a long trip, especially to the harsh radiation in deep space. Better known are the effects on bones and muscles, which gradually weaken in a weightless environment.
Ferguson had a short-term experience with that phenomenon during his first shuttle mission, in September 2006. He was unable to exercise much during the 12-day trip, and upon return to Earth, his legs felt sore.
"It was like leading a sedentary lifestyle, and then conducting a very rigorous workout in the gym," he said.
This time, he had access to some older exercise equipment that was not being used by long-term residents of the space station, and felt fine after his return.
Among the deliveries that Ferguson's crew made to the station was the urine-recycling system, which will reduce the need to send up large amounts of fresh water. The technology involves a multi-step process, including vaporizing and then condensing the liquid.
Therein lies one problem of doing it in the weightless environment of space, Ferguson said. For the vapor molecules to condense, they must be spun at high speeds, in a device like a centrifuge. This device broke during his stay, but before that the crew was able to purify 14 liters a day, he said.
The crew did not drink the end-product during the mission, but brought it back to Earth for testing. The water is purified to a higher standard than municipal drinking water, Ferguson said after his lecture.
"Drinking yesterday's urine, it's kind of yucky," he said. "But it works."
Contact staff writer Tom Avril at 215-854-2430 or tavril@phillynews.com
