There’s a fable that my fourth-grade teacher recounted to my class that tells of this family who lived in the forest in Germany. Their life was normal except for one thing. There was an axe stuck in the ceiling. The people of the house went about their lives knowing that the axe was there, perfectly aware of the danger it posed to them but doing nothing about it. And it would have stayed that way had it not been for a wise visitor—I don’t know who it was exactly, some guy—who witnessed the situation and gave them clear guidance. “Pull the axe out,” he said.
The meaning of the tale was clear. If you’re living with some clear and present danger, don’t just go about your day as if it wasn’t there. Do something about it!
The message wasn’t entirely lost on me, though I had some questions about how valid an example it was. “How’d the axe get there?” I asked. “Did it belong to someone?” And, “How well was it stuck in? Sounds like it had been there a while. Was it really such a danger?” And finally, “How much was it worth? Could they sell it and buy, I don’t know, a minibike or something?”
Mrs. McCarthy was a nice woman, and a great teacher, too, so she calmly explained to me that these tales weren’t intended to be true accounts but, rather, stories that illustrate an important lesson, and this one was, “Just take the axe out of the ceiling, you idiots.” Or something to that effect.
That made sense, but I still wanted to know “if it was one of those wicked-cool axes with two axe heads on it!”
“I think it was,” she said. She really got me.
The Global Positioning System, the trillion-dollar satellite locator system developed by the Department of Defense a few decades ago now, has revolutionized multiple segments of our lives. We think of it as being an aviation technology, but that’s a tiny slice of the benefits pie of GPS. From easy navigation right there on our cellphones to optimization of worldwide power grids, its reach is all encompassing. It’s transformed space, military logistics, trucking and shipping, mapping monitoring and hundreds of other applications. People often cite the United States Interstate Highway System, a program that dates back to the Eisenhower administration, as being the bringer of great wealth, and it did, connecting widely disconnected parts of America and creating a web of commerce that has had far-reaching salutary effects on the economy going on 70 years now. Its impact pales in comparison to GPS, I’d daresay.
That said, the power and ease of GPS have lulled us into a false sense of security, allowing us to forget that GPS is hardly robust. The satellites that compose the GPS constellation are susceptible to damage, accidental or otherwise, from space junk, and here on earth, their signals are frighteningly easy to jam.
Moreover, sun flares can disrupt GPS signals, as well, and scientists say that an extreme solar disruption could knock it out for an indefinite period. The Carrington Event of 1859 created a flare so powerful that it lit up the atmosphere in the Northern Hemisphere at night, causing miners to wake up many hours early and start making breakfast. Recent solar ejections in 2003 and 2007 were nowhere near as strong, but both disrupted GPS for a time. And even the powerful 1859 event was a blip compared to the flare emanating from Proxima Centauri that was so powerful, astrophysicists estimate it would have been enough to wipe out the atmosphere of a planet as far away from it as our home planet is to our sun. And while it would simply be game over in such an event, lesser flares are far more likely to happen, which we know from examining ancient tree rings and ice cores, could wreak havoc on GPS for who knows how long.
Indeed, GPS has become such a pillar of our National Airspace System that the United States has been decommissioning VOR radio navigation sites (which pilots can use to navigate to or from installed radio beacons) at a rapid clip. Five years ago, it announced its plan to decommission a lot of VORs—around 300 were on the chopping block. That’s a lot of VORs to turn off in a short period of time, but the FAA at the time pointed out that it was going to maintain a network of VORs around the country, which it calls the Minimum Operational Network, to use as backup. In our view, it’s a rudimentary, insufficient backup that will serve higher-flying commercial aircraft somewhat and lower-flying aircraft very poorly.
Despite its susceptibility to damage and disruption from forces natural and human-engineered, we have set up GPS as an irreplaceable part of our aviation infrastructure, with no fallback plan in place.
The good news is, there is a plan emerging. The Department of Transportation in January of 2021 invited 11 companies to present their entries to create backup systems to GPS. The technologies represented several different approaches to creating what the industry calls a “PNT” (position, navigation and timing) system to back up GPS.
Two of the systems were based on Loran, a long-range navigation system developed during World War II that was in active use up through the early ’90s and was in service in the United States until 2010, when the government turned it off in what was largely a budgetary move. Loran, which uses powerful and very low-frequency radio waves bounced off of the upper atmosphere to create guidance pathways, is hard to jam. And while its early versions gave rough navigational guidance, later iterations, Loran-C and e-Loran, which was in full development until the entire system was decommissioned, offer accuracy down to around 30 feet or better.
In addition to being based on a hard-to-jam or attack technology that is more robust to begin with than GPS, e-Loran provides performance similar to unenhanced GPS, allowing it to be leveraged for use in long-range (including great circle) navigation and for non-precision approaches to supplement existing instrument landing system installations. In addition to its native capabilities, e-Loran can act as a check of the integrity of GPS and vice versa.
Would an e-Loran system be expensive to design, install and maintain? Yes, it would be. But it would be easy for today’s users of GPS to adopt backup equipment, and, eventually, manufacturers would include e-Loran receivers in navigation systems, making the transition from GPS to e-Loran, whether the switch was made in a pinch or not, transparent to the end user. With the cost of losing GPS for an extended period so immense, we applaud the move to find a suitable backup system that will protect GPS’s vulnerabilities while offering additional benefits, some of which we might not be aware of yet.
