At 17:21:50
Universal Time (or Greenwich Mean Time as it was more often called in
1969) the Service Module's 20,500-pound-thrust engine started firing to
slow Apollo 11's velocity enough to go into lunar orbit. In Eastern
Daylight Time that was 1:21:50 PM. The burn lasted just under six minutes
(5:57). The burn placed the the three modules into an elliptical-lunar
orbit of 69 by 190 miles. That was made more circular by a second, much shorter burn of 17
seconds. This placed the docked vehicles into a lunar orbit of 62
by 70.5 miles.
This took place on July 19, 1969; most of you will see this post on July 20. The burn necessarily took place with the spacecraft on the far side of the moon, so ground controllers - and the millions of us hanging on every word - wouldn't know if the burn was successful until the spacecraft came over the horizon and could re-establish radio contact with Earth. Not that mission control or we could have done anything for the crew if there was constant communications. It's a quarter million miles away; and light or radio takes over a second to go each way. Nobody could have done a thing for them.
An artist's concept from the Apollo days:
It's just over 24 hours until the landing. The crew is busy scouting their landing site, checking out the Lunar Module and preparing for tomorrow as they orbit the moon every two hours. They do a couple of video transmissions for those keeping track of the mission.
All done with less computing power than a flip phone, right?
ReplyDeleteLess electric/electronic computing power than a flip phone. But lots and lots and lots of organic computers working slide-rules and log charts like mad people on speed.
DeleteAnd... the radio linked the capsule and lander to earth-bound mainframes that were also burning some serious electricity all the time.
People forget that. That there was a legion of calculators calculating everything before, during and after the whole thing. Backed up by lots of mainframe time as mainframes became available.
And, really, as long as everything's working a-okay, no need to have some serious computing power. It was all preprogrammed responses. Turn this switch, turn that switch, fire motors, reaction thrusters and such.
Very evident in all the semi-disasters that started in Mercury all through Apollo. From heat shields not releasing, to reaction motors firing improperly, to the Apollo 13 disaster. All pretty much handled on-site by the astronaut pilots in the moment of the emergency, followed by lots of ground-based computing that told the astronaut pilots parameters they had to hand-pilot to fix the situations.
Modern 'the ship flies itself, people are just passengers' started with the Shuttle. Dragon is the perfect example of current 'computer controls everything.
I was in summer school. Teacher wheeled a TV into the classroom. We watched everything from launch to splashdown. Got credit for it.
ReplyDeleteI had already built the model of the launch facilities, including the miles of piping, that I bought by taping a dime to a postcard. In class, I started building a Saturn 5. Stood about 18" height.
Truly, The Golden Age of Spaceflight.
ReplyDeleteMUCH more common now, which is actually A Good Thing.