At the beginning of this year, a group of NASA scientists agonized over which robotic missions they should choose to explore our Solar System. Researchers from around the United States had submitted more than 20 intriguing ideas, such as whizzing by asteroids, diving into lava tubes on the Moon, and hovering in the Venusian atmosphere.


Ultimately, NASA selected four of these Discovery-class missions for further study. In several months, the space agency will pick two of the four missions to fully fund, each with a cost cap of $450 million and a launch late within this decade. For the losing ideas, there may be more chances in future years - but until new opportunities arise, scientists can only plan, wait, and hope.


This is more or less how NASA has done planetary science for decades. Scientists come up with all manner of great ideas to answer questions about our Solar System; then, NASA announces an opportunity, a feeding frenzy ensues for those limited slots. Ultimately, one or two missions get picked and fly. The whole process often takes a couple of decades from the initial idea to getting data back to Earth.


This process has succeeded phenomenally. In the last half century, NASA has explored most of the large bodies in the Solar System, from the Sun and Mercury on one end to Pluto and the heliopause at the other. No other country or space agency has come close to NASA's planetary science achievements. And yet, as the abundance of Discovery-class mission proposals tells us, there is so much more we can learn about the Solar System.


Now, two emerging technologies may propel NASA and the rest of the world into an era of faster, low-cost exploration. Instead of spending a decade or longer planning and developing a mission, then spending hundreds of millions (to billions!) of dollars bringing it off, perhaps we can fly a mission within a couple of years for a few tens of millions of dollars. This would lead to more exploration and also democratize access to the Solar System.


In recent years, a new generation of companies is developing new rockets for small satellites that cost roughly $10 million for a launch. Already, Rocket Lab has announced a lunar program for its small Electron rocket. And Virgin Orbit has teamed up with a group of Polish universities to launch up to three missions to Mars with its LauncherOne vehicle.


At the same time, the various components of satellites, from propulsion to batteries to instruments, are being miniaturized. It's not quite like a mobile phone, which today has more computing power than a machine that filled a room a few decades ago. But small satellites are following the same basic trend line.


Moreover, the potential of tiny satellites is no longer theoretical. Two years ago, a pair of CubeSats built by NASA (and called MarCO-A and MarCO-B) launched along with the InSight mission. In space, the small satellites deployed their own solar arrays, stabilized themselves, pivoted toward the Sun, and then journeyed to Mars.


"We are at a time when there are really interesting opportunities for people to do missions much more quickly," said Elizabeth Frank, an Applied Planetary Scientist at First Mode, a Seattle-based technology company. "It doesn't have to take decades. It creates more opportunity. This is a very exciting time in planetary science."


Small sats


NASA had several goals with its MarCO spacecraft, said Andy Klesh, an engineer at the Jet Propulsion Laboratory who served as technical lead for the mission. CubeSats had never flown beyond low-Earth orbit before. So during their six-month transit to Mars, the MarCOs proved small satellites could thrive in deep space, control their attitudes and, upon reaching their destination, use a high-gain antenna to stream data back home at 8 kilobits per second.


But the briefcase-sized MarCO satellites were more than a mere technology demonstration. With the launch of its Mars InSight lander in 2018, NASA faced a communications blackout during the critical period when the spacecraft was due to enter the Martian atmosphere and touch down on the red planet.


To close the communications gap, NASA built the two MarCO 6U CubeSats for $18.5 million and used them to relay data back from InSight during the landing process. Had InSight failed to land, the MarCOs would have served as black box data recorders, Klesh told Ars.


The success of the MarCOs changed the perception of small satellites and planetary science. A few months after their mission ended, the European Space Agency announced that it would send two CubeSats on its "Hera" mission to a binary asteroid system. European engineers specifically cited the success of the MarCOs in their decision to send along CubeSats on the asteroid mission.


The concept of interplanetary small satellite missions also spurred interest in the emerging new space industry. "That mission got our attention at Virgin Orbit," said Will Pomerantz, director of special projects at the California-based launch company. "We were inspired by it, and we wondered what else we might be able to do."


After the MarCO missions, Pomerantz said, the company began to receive phone calls from research groups about LauncherOne, Virgin's small rocket that is dropped from a 747 aircraft before igniting its engine. How many kilograms could LauncherOne put into lunar orbit? Could the company add a highly energetic third stage? Ideas for missions to Venus, the asteroids, and Mars poured in.


Polish scientists believe they can build a spacecraft with a mass of 50kg or less (each of the MarCO spacecraft weighed 13.5kg) that can take high-quality images of Mars and its moon, Phobos. Such a spacecraft might also be able to study the Martian atmosphere or even find reservoirs of liquid water beneath the surface of Mars. Access to low-cost launch was a key enabler of the idea.


Absent this new mode of planetary exploration, Pomerantz noted, a country like Poland might only be able to participate as one of several secondary partners on a Mars mission. Now it can get full credit. "With even a modest mission like this, it could really put Poland on the map," Pomerantz said.


Small rockets


A few months before the MarCO satellites launched with the InSight lander on the large Atlas V rocket, the much smaller Electron rocket took flight for the first time. Developed and launched from New Zealand by Rocket Lab, Electron is the first of a new generation of commercial, small satellite rockets to reach orbit.


The small booster has a payload capacity of about 200kg to low-Earth orbit. But since Electron's debut, Rocket Lab has developed a Photon kick stage to provide additional performance.


In an interview, Rocket Lab's founder, Peter Beck, said the company believes it can deliver 25kg to Mars or Venus and up to 37kg to the Moon. Because the Photon stage provides many of the functions of a deep space vehicle, most of the mass can be used for sensors and scientific instruments.


"We're saying that for just $15 to $20 million you can go to the Moon," he said. "I think this is a huge, disruptive program for the scientific community."


Of the destinations Electron can reach, Beck is most interested in Venus. "I think it's the unsung hero of our Solar System," he said. "We can learn a tremendous amount about our own Earth from Venus. Mars gets all the press, but Venus is where it’s really happening. That’s a mission that we really, really want to do."


There are other, somewhat larger rockets coming along, too. Firefly's Alpha booster can put nearly 1 ton into low-Earth orbit, and Relativity Space is developing a Terran 1 rocket that can launch a little more than a ton. These vehicles probably could put CubeSats beyond the asteroid belt, toward Jupiter or beyond.


Finally, the low-cost launch revolution spurred by SpaceX with larger rockets may also help. The company's Falcon 9 rocket costs less than $60 million in reusable mode and could get larger spacecraft into deep space cheaply. Historically, NASA has paid triple this price, or more, for scientific launches.


Accepting failure


There will be some trade-offs, of course. One of the reasons NASA missions cost so much is that the agency takes extensive precautions to ensure that its vehicles will not fail in the unforgiving environment of space. And ultimately, most of NASA's missions - so complex and large and capable - do succeed wonderfully.


CubeSats will be riskier, with fewer redundancies. But that's okay, says Pomerantz. As an example, he cited NASA's Curiosity rover mission, launched in 2011 at a cost of $2.5 billion. Imagine sending 100 tiny robots into the Solar System for the price of one Curiosity, Pomerantz said. If just one quarter of the missions work, that's 25 mini Curiosities.


Frank agreed that NASA would have to learn to accept failure, taking chances on riskier technologies. Failure must be an option.


"You want to fail for the right reasons, because you took technical chances and not because you messed up," she said. "But I think you could create a new culture around failure, where you learn things and fix them and apply what you learn to new missions."


NASA seems open to this idea. Already, as it seeks to control costs and work with commercial partners for its new lunar science program, the space agency has said it will accept failure. The leader of NASA's scientific programs, Thomas Zurbuchen, said he would tolerate some misses as NASA takes "shots on goal" in attempting to land scientific experiments on the Moon. "We do not expect every launch and landing to be successful," he said last year.


At the Jet Propulsion Laboratory, too, planetary scientists and engineers are open-minded. John Baker, who leads "game-changing" technology development and missions at the lab, said no one wants to spend 20 years or longer going from mission concept to flying somewhere in the Solar System. "Now, people want to design and print their structure, add instruments and avionics, fuel it and launch it," he said. "That's the vision."


Spaceflight remains highly challenging, of course. Many technologies can be miniaturized, but propulsion and fuel remain difficult problems. However, a willingness to fail opens up a wealth of new possibilities. One of Baker's favorite designs is a "Cupid's Arrow" mission to Venus where a MarCO-like spacecraft is shot through Venus's atmosphere. An on-board mass spectrometer would analyze a sample of the atmosphere. It's the kind of mission that could launch as a secondary payload on a Moon mission and use a gravity assist to reach Venus.


"There’s so much of the Solar System that we have not explored," Baker said. "There are how many thousands of asteroids? And they’re completely different. Each one of them tells us a different story."


Democratizing space


One of the exciting aspects of bringing down the cost of interplanetary missions is that it increases access for new players - smaller countries like Poland as well as universities around the world.


"I think the best thing that can be done is to figure out how to lower the price and then make this technology publicly available to everyone," Baker said. "As more and more countries get engaged in Solar System exploration, we’re just going to learn so much more."


Already, organizations such as the Milo Institute at Arizona State University have started to foster collaborations between universities, emerging space agencies, private philanthropy, and small space companies.


Historically, there have been so few opportunities for planetary scientists to get involved in missions that it has been difficult for researchers to gain the necessary project management skills to lead large projects. With a larger number of smaller missions, Frank said she believes it will increase the diversity of the planetary science community.


In turn, she said, this will ultimately help NASA and other large space agencies by increasing and developing the global pool of talent for carrying out the biggest and most challenging planetary science missions that still require billions of dollars and big rockets. Because, while some things can be done on the cheap, really ambitious planetary science missions like plumbing the depths of Europa's oceans or orbiting Pluto will remain quite costly.


ERIC BERGER is the senior space editor at Ars Technica, covering everything from astronomy to private space to NASA. A certified meteorologist, Eric lives in Houston.