With SpaceX garnering so much attention with the recent launch of their new flag ship Falcon Heavy, the first operational rocket powerful enough to take passengers to the moon since the retirement of the Saturn V, it would seem that the world is once again looking toward the possibility of manned space flight with destinations beyond low earth orbit in mind. Although NASA’s much touted SLS (Space Launch System) is expected to dethrone the Falcon Heavy as the most powerful rocket on the planet whenever it’s completed, repeated delays have sucked much of the wind from America’s deep space sails… but then, maybe NASA doesn’t need sails at all.

A manned mission to Mars would be an expensive endeavor, in large part because of how long the trip would take and all the variables to manage in the name of the crew’s safety. For instance, NASA’s two primarily spacecraft propulsion methodologies are effectively the same as everyone else’s: chemical and electrical (solar) propulsion. Each have their drawbacks. Chemical propulsion (think rocket engines) require a massive amount of fuel, creating a complex algebraic equation for each launch: the further you hope to go, the more fuel you need to carry, the more fuel you need to carry, the heavier the spacecraft, the heavier the spacecraft, the more fuel you need to carry… and so forth. Because of this, it’s likely that a manned mission to Mars would involve launching fuel storage at the planet in advance of the mission’s arrival, giving astronauts a chance to refuel before heading back home.

The massive orange fuel tank the Space Shuttle carried was used only to provide fuel to the Shuttle’s three chemical propellent engines through launch alone. (NASA)

The alternative, often used on satellites and unmanned spacecraft, is solar electrical power. The problem is, these spacecraft can travel far distances on extremely low levels of fuel, but they travel far too slowly to be a reasonable approach to manned space travel. The options, then, seem to be carrying tons of fuel for an inefficient power plant that can get humans to Mars fairly quickly, or carry tons of food and water to sustain a crew on an extremely long duration solar fueled trip.

A chemical system has tremendous thrust force, but low miles per gallon, and you can only carry enough propellant to thrust for minutes,” Jeff Sheehy, chief engineer of NASA’s Space Technology Mission Directorate, explained. “A solar electric system has very low thrust force, but very high miles per gallon, and you can carry enough fuel to thrust for years.”

There is, however, one more option… one that would require very little fuel compared to chemical rockets, but still reach the Red planet significantly faster than current projections. Where can one find this miraculous technology? Well, sitting on NASA’s shelf for the past forty or so years…

Back in the 50’s and 60’s, NASA devoted considerable resources to the development of a nuclear propulsion system that could be used in spacecraft. This nuclear thermal propulsion (NTP) proved possible, but at the time, there were a number of technological limits to what we were capable of managing in a safe way, and further, there didn’t seem to be sufficient interest in deep space exploration to warrant the continued effort. By the 1970s, when the NTP was being shelved, the American public had already lost interest in the Apollo missions. The space race was over, and America was just beginning to settle in for another fifty (plus) years of never venturing further than a few miles from our planet’s surface.

Now, though, many of those technological hurdles are no longer as daunting, and perhaps more importantly, public interest in manned space travel is once again beginning to grow.

I mean the desire has always been there,” Sheehy said, “but the push or the emphasis that NASA has had for the last few years about developing that capability—that has renewed the interest in NTP as an option.”