The phone call Elkins-Tanton received was the culmination of a process that officially started in November 2014, when NASA announced it was accepting proposals for its next Discovery mission.

Discovery missions are cost-capped at about $500 million, not including launch and operations costs. There is also a second competitively selected mission type called New Frontiers, which gives winning missions a budget of around $800 million, including the price tag of a rocket.

Right now, NASA is accepting proposals for its next New Frontiers mission. They're due in April, and in November, three winners will get funded for further studies. NASA plans to make a final decision on which mission will fly in mid-2019.

The process is not for the faint of heart. Scientists and engineers can spend years toiling over a proposal, only to have their hopes dashed by the selection process.

I wanted to learn more about why some missions succeed and some don't, so I asked two recent winners how they pulled it off. It turns out that while both missions had slightly different recipes for success, there were a lot of similarities: intangible assets like good team chemistry and a knack for navigating the science community landscape can be just as important as the nuts and bolts that make up a spacecraft.

Third time's a charm for OSIRIS-REx

The last New Frontiers mission to launch was OSIRIS-REx, which blasted off in September to collect a sample from asteroid Bennu.

It would actually be more accurate to say the journey of OSIRIS-REx began 13 years ago. In 2004, Michael Drake, the former head of the University of Arizona Lunar and Planetary Laboratory in Tucson, wanted to propose an asteroid sample return mission. Drake asked LPL colleague Dante Lauretta, who was an untenured, assistant professor at the time, to become his deputy principal investigator.

Drake and Lauretta pitched the mission to NASA's Discovery program. They weren't selected, and NASA gave the proposal the lowest possible grade: category four.

"Category four means you're rejected and they shouldn't even need to tell you why," Lauretta said during a recent phone interview. "We were pretty naive back then, I'll admit."

The mission science, he said, was compelling. "But the technical management and cost needed a lot of work."

Ultimately, NASA didn't select any Discovery missions that time around. When the agency asked for new proposals a year later, Drake and Lauretta decided to try again.

This time, Lauretta worked closely with engineers at Lockheed Martin, in an attempt to better synchronize the mission's science and engineering aspects. He wanted to understand every aspect of the spacecraft, and ensure the Lockheed team understood every part of the mission science.

"I really learned how spacecraft are put together," Lauretta said. "But, most importantly, I learned how you translate science into engineering-speak, because they really are different languages."

Drake and Lauretta made it to the final round, but ultimately lost to GRAIL, a pair of lunar gravity mapping probes that launched in 2011. On the bright side, NASA said the asteroid mission's science and engineering was solid—the problem was that it was getting too expensive.

In 2008, the National Academy of Sciences prepared to release an interim update to their 10-year Decadal Survey, which lays out acceptable mission themes for the mid-cost New Frontiers program. An asteroid sample return mission had not been prioritized in the last Decadal Survey, so Drake and Lauretta's team started pitching the benefits of such a mission to the science community. They also demonstrated how they could overcome any potential engineering challenges.

The Academy was convinced. When the interim report was released, "Asteroid Rover/Sample Return" was listed as a mission theme. The next New Frontiers proposal was due in 2009, so Drake and Lauretta tweaked their proposal and applied. This time, they won, beating out a lunar sample return and a Venus mission.