A little more than a month ago, an interstellar visitor now known as ‘Oumuamua passed within 24 million kilometers of Earth. It is now moving rapidly away from the Sun at a velocity of approximately 26km/s. That is considerably faster than, say, the Voyager 1 spacecraft, which is hurtling beyond the Solar System at a velocity of 17km/s.
The first interstellar object is doubly intriguing because humans have never been able to study something from beyond the Solar System up close. Moreover, recent observations have shown that ‘Oumuamua has a reddish color, astronomers say, and unexpected oblong shape, like that of a giant, 400-meter-long cigar. Already, the object is fading from view, and we will never see it again as it zooms away.
But what if we could? NASA is building what will be the world’s most powerful rocket, the Space Launch System. Would it be capable of launching a small probe to catch ‘Oumuamua? Do we have any technology that can catch this interstellar interloper?
Catch me if you can
To find out, Ars turned to the Advance Concepts Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. The office’s manager, Mark Rogers, spoke to Ars, as did one of his mission planners, Larry Kos. It turns out they were curious, too, and had done some preliminary calculations on the possibility of intercepting ‘Oumuamua.
The short answer is, unfortunately, we are too late now with our existing technology. Although ‘Oumuamua is moving at a velocity of 26km/s, factoring in Earth’s velocity vector, the delta-v between a spacecraft in Earth orbit and the object is closer to 60km/s. “Chemical propulsion just doesn’t close the case in this scenario,” Rogers said. “It’s not feasible.”
But what if NASA had worked feverishly after detection of the object on October 19 and already sent a probe into space? The problem with our primary propulsion methods is that, while chemical rockets are very good at getting stuff out of Earth’s orbit, they’re gas guzzlers in space. Most of our existing in-space propulsion systems are based on chemicals, and they need a lot of fuel—often hydrogen—to move a spacecraft about. In this case, Kos calculated the specific impulse needed for chemical rocket engines to catch ‘Oumuamua at about 450 seconds.