NASA image of a sextant

NASA testing a cosmic compass so no one ever gets lost in space

Contributed by
Jun 21, 2018

Because even NASA astronauts have a fear of ending up stranded in that alien expanse of darkness, they need a navigation tool that will help them follow the stars back to their home planet.

The type of gadget that could pull this off, a sextant, has actually been around for hundreds of years. Sextants are the reason sailors were able to find land again after long and often perilous sea voyages. They figure out where you are by using optical sight (similar to a telescope’s) to precisely measure angles between stars, whether you’re earthbound or spacebound. Astronauts can line up a star with a landmark that stands out, input the readings into a computer, and find out their position in space.

Except you can’t exactly test a NASA sextant from the ground. You need microgravity for that, which is why a hand-held sextant is now being evaluated on the ISS.

“The basic concepts are very similar to how it would be used on Earth,” NASA principal investigator Greg Holt explained. “But particular challenges on a spacecraft are the logistics; you need to be able to take a stable sighting through a window.”

NASA has used sextants before, from having them built into the Apollo vehicles just in case navigation went bust to using them on its Gemini missions, which were the first spacecraft to conduct sextant sightings. There have also been astronaut-conducted experiments on Skylab.

How to not get stranded in space. Credit: NASA

The ISS investigation aims to level up the technology by focusing on specific techniques, which is why the space agency is relying on feedback and new ideas from astronauts conducting the investigation to develop the most accurate instrument possible.

“No need to reinvent the wheel when it comes to celestial navigation,” said Holt. “We want a robust, mechanical back-up with as few parts and as little need for power as possible to get you back home safely. Now that we plan to go farther into space than ever before, crews need the capability to navigate autonomously in the event of lost communication with the ground.”

Using a sextant for emergency spacecraft navigation means the instrument needs to be incredibly stable. How precise it is when determining angles between the planets, stars and moons is everything when communications and other tech break down, and could mean the difference between landing back on Earth and floating out there forever. Apollo 8 astronaut Jim Lovell was successfully able to prove that a sextant can guide a crew home in case of technical failure, so its evolution should only keep going to infinity and beyond from there.

Let’s hope this means Lost in Space stays in the realm of science fiction.

(via NASA)