The Space Reviewin association with SpaceNews

NSRC 2020

New Horizons
While NASA’s New Horizons mission is headed to Pluto, it may be possible to develop a mission that can probe even deeper into the outer solar system. (credit: JHUAPL/SwRI)

Hitching a ride to the Oort Cloud

We’ve just received a bit of interesting news from the Oort Cloud, that region of our solar system where, according to the theories of the late Dutch astronomer, Jan Oort, comets are born our of the debris left over from the birth of our little speck of the galaxy. According to a report released today by a team led by Andrew Becker of the University of Washington, an Oort Cloud object named 2006 SQ372 (SQ372 for short) has been detected a little over three billion kilometers from Earth, a bit closer to us than Neptune.

Now that SQ372 has been detected it’s on its way back out to its usual stomping grounds over 200 billion kilometers away, and it will not be back our way for another 22,500 years. It’s much too late to even think about sending a mission to examine it, but that should not stop the space scientists and NASA from thinking about a possible hitchhiking mission to the Oort Cloud. Think of it as the ultimate flagship mission.

A hitchhiking mission to the Oort Cloud would be the ultimate flagship mission for NASA.

Imagine how such a mission might work. An incoming Oort cloud object is detected beyond the orbit of Pluto. A nuclear-propelled probe has been prepared and is ready to launch. Ten years or so after launch, the probe rendezvous with the object and either lands on it or sends down a lander with a large radioisotope thermoelectric generator (RTG) and together they fly out beyond our solar system.

The size of the probe would be large, since it would need lots of fuel and redundant communications systems and instruments. It is probably an ideal candidate for launching on an Ares 5. NASA would have to prepare a complex scheduling contingency plan to be able to launch the mission in the rather narrow window between the moment the target object is discovered and the time when it moves out of range. The agency would only have a few months to calculate the orbit, prepare the probe, mate it with the launcher, and send it on its way. This would probably conflict with whatever plans they had for a Moon mission or whatever other use they had planned for that particular rocket.

With fairly large antennas and a very long-lived RTG, the package of instruments could, if all goes well, be sending back data decades after the object has moved beyond the heliopause. It would, in effect, act as an observatory stationed tens of billions of miles beyond Pluto. This would not just be a decades-long mission, like Voyager, but one that could last for a half-century or more. It would imply not just an upgrade of the existing Deep Space Network for communications, but would require a whole new set of coordinated antennas on Earth, on the Moon, and in space. Obviously this would have implications well beyond the Oort Cloud mission.

Such a mission would build on NASA’s experience with expensive long-range “Flagship” missions such as the Galileo mission to Jupiter and the ongoing spectacularly successful Cassini probe, now orbiting Saturn. It would be led by NASA, but would be open to scientists from all over the world. Indeed, because it would be such a long-lasting mission, the world astrophysical community would have to prepare a plan to train several generations of scientists to manage the operation. This will force governments and universities to think about education on a much longer time scale than they are used to.

In any case this mission would only be launched sometime between, say, 2025 and 2035: far enough in the future for careful planning and for a solid international research consortium to be put in place. Politically this would be the opposite of the usual problem when leaders want to see a payoff for their investments before the next election, or at least before they leave office. For this project most of the politicians in the US who would vote for the initial, and fairly modest, funds would be dead by the time the mission reached its full potential. They would at least have the satisfaction of knowing that even if they will not be alive to reap any political rewards for having supported such a farsighted mission, their rivals would not be able to take any bows either.

Politically this would be the opposite of the usual problem when leaders want to see a payoff for their investments before the next election, or at least before they leave office.

Ever since the days in the early 1970s when the “Grand Tour” proposal, that later turned into the Voyager probes, was being debated, the US has led the way in launching missions to explore the far reaches of the solar system. Europe’s Rosetta is the only non-US deep space probe that is headed out there. If it works as planned, ESA will have demonstrated that it has the capability to act as a responsible senior partner in this effort.

The Oort Cloud awaits.