In responding to the president’s desire to return Americans to the moon within his planned term of office, NASA Administrator Jim Bridenstine faces several challenges, perhaps insurmountable ones. Ignoring the political and budgetary constraints under which he must plan such a technical accomplishment, he is hampered by tired thinking going back to Apollo.

Fifty-eight years ago, almost to the day, President Kennedy declared what was, at the time, a bold national goal: To send a man to the moon within a decade, and “return him safely to Earth.” The greatest challenge of Apollo was not the former, but the latter.

Simply getting someone to the moon was relatively easy, even then: Launch a rocket with a crew and a lander, and land the latter on the lunar surface. It could be done with a much smaller rocket than the Saturn V.

But in order to return, another vehicle would be required to first get back into orbit, and then additional propellant to get it all the way back to Earth, and that vehicle would have to be capable of entry into the atmosphere and recovery on the planet’s surface. As it turned out, two more vehicles were deployed: A lunar ascent stage, and a capsule for recovery into the atmosphere. Because we had too little experience with space assembly, all this additional hardware, and the propellant needed to get it all the way there and back, had to be launched in a single flight from Florida. The capsule with its precious human cargo that sat on top of the huge Saturn V launcher, is all that came back from the moon.

While Kennedy’s goal was achieved, the science we got from the six lunar missions was limited by the necessarily short mission durations on the lunar surface. In particular, we continue to have no data on the long-term effects of partial gravity, including the ability to conceive and gestate healthy offspring of even rodents, let alone primates, including humans, knowledge critical to understanding the ability of humanity to thrive on the moon.

In the planning of the return to the moon, we seem to be attempting to simply repeat Apollo: Send a man (and woman) to the moon, and return them safely to Earth. But suppose we eliminate the latter requirement, at least initially?

If we don’t need to bring them back immediately, the 2024 mission gets much simpler, and affordable: Build a habitat capable of being resupplied, and land it on the moon. Then, after verifying that it’s functional, send its first crew. We know how to build space habitats from ISS experience, and lunar habitats are easier, because they have some gravity to work with. All the necessary major hardware that would be new is a lander. A few weeks in Washington, Jeff Bezos, richest man in the world and founder of the space company Blue Origin, unveiled a mock-up of one they plan to build. There is no reason to think that, given adequate funding (and it would surely be much less than one developed by NASA under a traditional cost-plus contract), it couldn’t be ready and tested in four years (and would be required even with a planned return, though the requirements might be different).

With no immediate need for lunar ascent, the mission could be done with existing launchers, such as the Falcon Heavy.

When would the crew return? Whenever we have developed the means for them to do so, an activity that could be done in parallel, but without the 2024 urgency. In the meantime, over months, or perhaps a year or three, they will be able to engage in long-term exploration of the moon and research into the effects of partial gravity, perhaps taking some rats along to attempt breeding. If they had the capability to do EVA (something necessary for proper exploration in any event), resupplying them indefinitely would be straightforward, with occasional deliveries of food, water, clothing, and lithium hydroxide to scrub the habitat atmosphere, just as we do with the CRS deliveries to ISS. It would be the very definition of “sustainable.”

In fact, the marginal cost of such a mission might be sufficiently low as to allow multiple habitats and crews in different locations, with regular crew rotations once a round-trip system has been developed over the next couple of years. And each base could grow as well with the delivery of additional habitats, allowing volume for experiments in lunar agriculture and perhaps aquaculture.

Is the plan risky? Of course it is. If there was a medical, or other emergency, there would be no immediate way to evacuate the crew. But for decades, we have accepted this risk at Amundsen/Scott Station, with no ability to evacuate researchers through the austral winter.

No frontier is opened without risk, and the space frontier is the harshest one humanity has ever faced. But with the acceptance of risk can come great reward, and the reward here is serious lunar research, within half a decade, far beyond the limited expeditions of half a century ago. Does anyone doubt that there are researchers, within or outside of the NASA astronaut office, willing to accept that risk? If so, perhaps we haven’t been doing a good job of selecting astronauts, but I don’t believe that is the case.

For decades, with each failed programmatic attempt at a lunar return, from President George H. W. Bush’s Space Exploration Initiative, to his son’s Vision for Space Exploration, the ostensible goal has been to “return to the moon, this time to stay.” Yet somehow, rather than being bold, the plans always start with a repeat of what we did in the 1960s.

It is now the 21stcentury. The best way to assure that when we go “back to the moon, this time to stay,” is to stay. Let us get on with it.

Rand Simberg is the author of “Safe Is Not an Option: Overcoming the Futile Obsession with ‘Getting Everyone Back Alive’ That Is Killing Our Expansion into Space.”