Welcome to brain Stuff production of iHeart Radio. Hey, brain Stuff, Lauren vocal bomb here. It's hard to believe that as I'm saying these words, almost half a century has gone by since Neil Armstrong, Edwin buzz Aldrin, and Michael Collins blasted out of the Kennedy Space Center in Cape Canaveral, Florida with the presidential promise to fulfill. But here we are. The Apollo sixteen mission launched on July six, nine, sixty nine, at ninety two am Eastern Standard time, and NASA didn't
pick that start time at random. It was chosen because it checked off the right boxes on a long list of requirements. Crafting launch schedules has always been a rigorous science. Every mission has its goals. In Apollo eleven's case, the main objective was to put an American astronaut on the Moon, winning the space race for old Uncle Sam. To that end, NASA selected five potential landing sites just above the lunar equator,
since nobody likes a bumpy landing zone. The candidate sites were geographically flat, but the astronauts couldn't just head out at their earliest convenience, a lunar day lasts for twenty nine point five Earth days, so if you were to stand at given point on the Moon's surface for that amount of time, you'd experience about fourteen straight days of NonStop sunlight, followed by roughly fourteen uninterrupted days of darkness.
For Apollo eleven, NASA went full Goldilocks. The agency decided that the cruise now famous Eagle module needed to land at lunar dawn, when the sun is low but still visible. Shadows became a topic of discussion. If the ground level shadows were too long or too short when Armstrong and company first arrived, they'd cause visibility problems. Therefore, the Eagle would have to touch down while the sun was between fifteen and forty five degrees above the lunar horizon. These
factors helped give NASA a set of launch windows. A launch window is the time frame in which a spacecraft can leave the Earth. They're often quite narrow, especially when complex maneuvering is involved. With the Apollo eleven, the crew had to blast off, position themselves over a specific corner of the Earth, shoot toward the Moon, and then land the Eagle at a pre approved site during lu or dawn when the sun was fifteen to forty five degrees overhead.
Of the five possible landing areas, NASA ultimately chose the Sea of Tranquility. They wanted to put Armstrong and Aldrin up there late in the summer of nineteen sixty nine. The lunar orbit meant that NASA would only get two chances to hit its moving target. In order to reach the Sea of Tranquility under the perfect set of conditions, Apollo eleven had to take off on either July six
or August fourteen. NASA picked the former date. The July sixteenth launch window was open from ninety two am to one pm to buy the cruise of extra time in case they needed it later. Apollo eleven was set to head skyward at the earliest possible opportunity, which is to say, right when the window opened. Within four days, Armstrong and Aldrin were doing the moonwalk. The astronauts returned to Earth on July. Fifty years later. Launch schedules are still notoriously
hard to plan. As NASA's official website dryly notes, this is not a job for someone who slept through physics class. Launch windows are inevitably shaped by mission objectives want to send her over up to Mars. Your best bet might be to wait until Mars and Earth find themselves in opposition, a point when the gap between the two planets is fairly short and they're both on the same side of the Sun. That opportunity only comes along once every twenty
six months. When a spacecraft is supposed to visit another heavenly body like Mars or the Moon, its travel plans will be dictated by the other body's orbital pathway and Earth's own trajectory. And that's not all. The gravitational influence of other bodies such as the Sun must also be considered. Plus, man made devices always encounter friction and wind when they
pass through Earth's atmosphere. That interference is guaranteed to affect launch trajectories and by extension, launch windows, and of course, atmospheric pushback isn't just a problem for deep space missions. Even crafts that were built to orbit the Earth and
go no further have to deal with this issue. One such object is the International Space Station, aboard a crude laboratory, the i S s orbits roughly two and twenty miles above the Earth or about three D fifty KOs and completes about six teen revolutions around the planet every day. NASA used to send astronauts up to the I S S in reusable space shuttles every day. The I S S would pass over or near the launching site at
Cape Canaveral. For a successful rendezvous to occur, NASA's shuttles needed to take off within five minutes of that passage, and to avoid dumping fuel tanks onto populated areas, the ships had to follow a south to north trajectory over the Atlantic Ocean. You won't see any of those launches on NASA's twenty nineteen schedule. The American space shuttle program was retired in twenty eleven, and NASA no longer ferries astronauts to the I S S. At the moment, that's
Russia's job, regardless of the county. Space Center sees off loads of other missions every year, and by the way, NASA's got plenty of other launch sites at its disposal, including the Vandenburg Air Force Space in southern California. And wherever a launch is scheduled to begin, you can bet that meteorologists are paying close attention to the weather. Early in twenty nineteen, the much anticipated lift off of a space X Falcon heavy rocket at Cape Canaveral was delay
aid due to high winds. Back in nineteen seventy one, weather constraints forced NASA to postpone the Apollo forteen launched by forty minutes. These delays were imposed after a close call in November of nineteen sixty nine, when the Apollo twelve crew launched on a murky morning from Kennedy Space Center. Just thirty six and a half seconds later, when the crew was about a mile and a half or two and a half kilometers above the ground, the first of
two lightning bolts struck the vessel. Nobody panicked. Astronauts Charles Pete, Conrad, Alan Bean, and Richard Gordon followed mission controls instructions carefully, and within a week Apollo twelve made it to the Moon, but NASA set up strict launch standards that prevented this from ever happening again. But rain, lightning, and wind aren't the only things that could potentially interfere with the launch.
To avoid putting any passing airplanes in harm's way, NASA collaborates with the U. S Air Force and Federal Aviation Administration to close large squads of commercial airspace during launch windows. Today's episode was written by Mark Bancini and produced by tie Are Playing brain Stuff is a production of I Heart Radio's How Stuff Works. For more on this and lots of other carefully calculated topics, visit our home planet,
how stuff works dot com. And for more podcasts from my heart Radio, visit the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.