In late March astronaut Scott Kelly and cosmonaut Mikhail Kornienko will take off in a Soyuz rocket from the steppes of Kazakhstan, heading to the International Space Station (ISS) for a yearlong stay. NASA bills their mission as a crucial stepping-stone toward sending humans on a multiyear trip to Mars. That interplanetary voyage, part of our human drive for new frontiers, is the greatest dream of the space age. Yet rather than making that dream a reality, this mission seems to be a distracting detour.
 
During their orbital sojourn Kelly and Kornienko will undergo rigorous medical testing designed to show researchers what long-term spaceflight does to human beings, particularly how prolonged weightlessness and radiation exposure cause harm. The results, NASA says, could lead to medical breakthroughs that make interplanetary hauls safer.
 
Could—but it likely won’t make them safe enough. More likely, Kelly’s and Kornienko’s tests will just confirm in greater detail what we already know from several previous long-duration missions: Our current space habitats are not adequate for voyages to other worlds. The lack of money to build these habitats, more than any lack of medical knowledge, is what keeps humans from Mars and other off-world destinations.
 
For instance, we already know that living without gravity is a problem. Long periods of weightlessness atrophy muscles, weaken bones and worsen vision. Vigorous exercise can minimize some of these effects, so astronauts on the ISS spend hours each day working out. Even so, no matter how much they sweat in space, when Kelly and Kornienko return to Earth they will almost certainly be weaker than when they left.
 
Investigators have known how to solve this problem since 1903, when Russian scientist Konstantin Tsiolkovsky described a spinning space habitat that would generate a force pulling away from the structure’s center and toward the outer edges, thereby mimicking gravity. This effect varies with the structure’s spin rate, creating any gravitational strength the structure can withstand, whether the comfortable one g of Earth or the languorous 0.38 g of Mars. (No one yet knows the optimum g-levels for healthy, affordable long-duration spaceflight, and Kelly’s and Kornienko’s mission won’t tell us.)
 
Why doesn’t NASA avail itself of this solution? Because it costs a lot, and the agency has already spent more than $75 billion on the weightless ISS. A rotating habitat would be more costly and complex than a weightless one (although it need not be a prohibitively pricey behemoth like the doughnut-shaped space station from 2001: A Space Odyssey). Two modules connected by a long spoke, set spinning by modest bursts from thruster rockets, could create artificial gravity at a more reasonable price, although this solution would still be more expensive than simply performing more medical tests in weightlessness.
 
What NASA should be testing is how to build such a craft, and how to live and work within it without becoming disoriented and dizzy. As a starting point, a scaled-down centrifuge could be installed on the ISS to test how lab animals respond to varying levels of artificial gravity. The station was originally designed to include such a facility, the Centrifuge Accommodation Module. NASA, however, scuttled the project by removing it from ISS assembly flights during the shuttle era, in part due to budgetary concerns.
 
Radiation, the other health threat in space, is a more pernicious danger. Showers of solar protons and galactic cosmic rays can rip through cells, wreaking biological havoc. The current remedy is to clad living quarters in layers of dense material, which adds weight and increases the amount of fuel needed to get off the ground. It doesn’t have to be this way. Advanced space propulsion systems paired with cheaper rocket launches could allow properly shielded craft to make faster interplanetary trips, decreasing a crew’s overall radiation exposure. Such protection will be possible only if NASA rekindles and follows through on developing advanced solar- and nuclear-electric propulsion, efforts which have been started and canceled several times over the past half century.
 
It would be unfair to blame NASA alone for this shortsightedness. Integrating artificial gravity and better propulsion into its human spaceflight program would require many billions of dollars, and that money is not forthcoming from Congress. So NASA has struck a pragmatic course, tinkering with well-worn technologies instead of spending the financial and political capital to develop new ones.
 
This path of least resistance is not going to take us to Mars—or on long-duration trips to the moon, asteroids or other deep-space destinations. NASA leadership should take a page from the playbook of Elon Musk and SpaceX and be bolder, pushing technologies for future exploration rather than relying on those from the past. If the American people do not feel that it is worth the money to take these next steps, the nation should face facts and abandon this dream of sending space travelers to worlds beyond our own.