Little to add

If you’ve been paying close attention to the obscure sections of the media, you might already know that today is the 50th anniversary of the moon landing. You know, Earth’s moon, Luna, that big grey thing in the sky, just to clarify. And I’m vaguely curious to know how much attention this gets in other countries; I imagine it’s at least a tad less in Russia, for instance. Nationality is a stupid thing, and while we might credit any accomplishment to the country where most of the participants hail from, major endeavors such as going to the moon were not only built upon the efforts and expertise of people around the world, they relied on the scientific accomplishments from all of previous history. This is a human milestone, pure and simple.

My own perspective hasn’t really changed from when I covered the 40th anniversary, so I’ll refer you back to that one – it’s got a picture and all. [I know, I’ve barely been posting anything recently and with a topical subject at hand, I’m chickening out and using an old post. But we already know I suck. And worse, I’m about to do an outside link too.]

But for a newer perspective – well, okay, no, it’s also fifty years old, but it might be as new, i.e., previously unknown, to you as it was to me – we go to the Astronomy Picture of the Day from a few days back, and a composite video of the Apollo 11 lunar lander’s descent. Overlaid is the communications between Aldrin and Armstrong in the lander itself, as well as ground control in Houston and all of their monitoring and concerns. The targeted area for landing turned out to be too dangerous, strewn with boulders and debris, and beyond it was a crater with uneven slopes, so Armstrong had to take over and manually drift the lander to the side to avoid these – with fuel running dangerously low. Now, I knew about their fuel reserves long ago, but it’s quite another matter to be watching it, realtime as it were, as the lander drifts towards a safe spot while the clock is ticking. There’s little for us to compare it to, because most of us aren’t even airborne – um, uh, spaceborne, vacuum-borne, aloft, whatever – when we do anything, but the lander had to set down precisely and gently, and even a rougher landing could mean that they wouldn’t be able to leave again.

You see, there weren’t a lot of options. The little engine in the base of the escape module (the upper stage of the lander, that would detach and carry them back to orbit to rendezvous with Collins in the command module) was fixed-thrust and non-gimbaled, meaning it couldn’t be aimed, so any corrective aiming had to be done with the reaction control system, those little nozzles around the module that you see in all of the photos, which also had limited fuel. Set down at too steep an angle, and while the escape module might leave the moon’s surface, it wouldn’t be able to adequately correct its path and make rendezvous. So, descent and landing had to be pretty kosher. As it was, they touched down so gently that they didn’t even compress the landing struts, those legs of the lander, and their egress to the moon required a bigger jump off the ladder than anticipated.

One more silly bit, because it’s actually an interesting aspect of physics. It’s easy to think that the lander wasn’t too hard to handle because of the lower lunar gravity, which is true insofar as descent acceleration went. However, even in microgravity, objects still have their mass, which has inertia, and inertia still has to be overcome. A very large or dense object can take a lot to move, stop, or change direction, so while it might take less fuel, it’s not like tossing around an empty crate. It might be likened to heavy objects on a slick sheet of ice – starting their movement, or stopping them, still takes considerable effort.

Anyway, enjoy the celebrations (he says in order to post this before the day’s over.)