Science & Technology

Why the Apollo 11 Astronauts Almost Ran Out of Fuel During the Moon Landing

Here's a little-known fact about Apollo 11: The crew of that first moon landing arrived on the moon with less than 30 seconds of fuel left in the tanks. A new video shows us exactly why. It's a simulation of Neil Armstrong's view out the lander window when he was behind the controls. As he made his descent, he saw a big obstacle that was blocking the possibility of a safe landing — and he had to think fast.

Help From a NASA Spacecraft

Humanity's first moon landing was 50 years ago this week, on July 20, 1969. It was not an easy journey. Partway through the sequence, the astronauts battled a computer error. Once that was resolved, they faced another challenge closer to the surface.

The lunar module was on autopilot until Armstrong, an experienced test pilot, switched to manual control. The famous video that most have seen of the moon landing shows what his crewmate, Buzz Aldrin, could see out the window, but there was no camera available showing what Armstrong saw.

That is, until now. Scientists recreated Armstrong's view using data from NASA's Lunar Reconnaissance Orbiter Camera, which has been taking high-resolution pictures of the moon for 10 years. They reconstructed the landing trajectory by navigating via lunar landmarks and taking note of Aldrin's altitude callouts as the crew finished their touchdown.

The result is simply extraordinary.

Going to Manual

The fateful (and potentially fatal) obstacle to the astronauts shows up immediately in the video: The spacecraft was inadvertently steering the astronauts to a rocky side of West Crater, which is 625 feet (190 meters) wide. So Armstrong took over. He was way too busy to explain his actions to Mission Control, but in the video, you can see his careful steering around craters and other obstacles as he looks for a safe landing zone.

"Of course, during the landing he was able to lean forward and back and turn his head to gain a view that was better than the simple, fixed viewpoint presented here," said Mark Robinson, the principal investigator for the camera, in a statement. "However, our simulated movie lets you relive those dramatic moments."

The last crater you see under the lunar module is called Little West Crater, which Armstrong briefly visited during the two-hour moonwalk on the surface. Then you'll see a strange thing pop up in the camera view: the actual lunar lander, as photographed by LRO. Naturally, Armstrong was not looking at a spacecraft on the surface, but the flat lunar regolith or soil. The reason we see the spacecraft today is that the data is based on images taken decades after the landing when the lunar module was already on the moon.

Incidentally, the crew did have maps of the lunar landing zone to assist in their work. But these maps were low-resolution compared to what LRO is capable of today. NASA wants to land astronauts on the moon by 2024, and if that happens, LRO images will definitely be guiding them. Here's hoping there are fewer surprises for the next landing crew, whenever they touch down.

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Written by Elizabeth Howell July 18, 2019

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