Tuesday, December 21, 2021

A Special Day In Different Ways

To begin with, it's winter solstice.  Solstice comes from words meaning "sun" and "standing still" and marks the time when the sun's position stops moving south (today) or north (the June summer solstice).  To be precise, the moment of the solstice was this morning at 1559 Universal Time  which was 10:59 AM here on EST.  It's the shortest day of the year but neither the latest sunrise or the earliest sunset.  The earliest sunset was in early December; the latest sunrise will be in early January.  

For me, what both the summer and winter solstices have in common is that I'm hoping for cooler weather.

The motion of the sun north and south over the course of the year traces out a curve called an analemma, which you usually see printed on globes.  You can photograph one of these yourself if you care to dedicate a camera to doing nothing else for a year.  One of my favorite analemma photographs is this one from Romanian photographer István Mátis who captured the view from a window in his apartment.

Technically, this isn't hard.  You point a camera so that the winter sunrise is at the bottom right of the frame and it helps to have an idea of how big a field you need to capture and choose the right lens.  It doesn't need to be the moment of sunrise, just the same time every day.  A special aspect about today's solstice is that it's the last 21st day of a month in 2021, the 21st year in the 21st century. 

Another special part of the day was this morning's SpaceX launch of Cargo Resupply Service (CRS) 24 mission to the Space Station.  I would have bet money that they wouldn't launch the mission this morning - and lost.  There was a 70% chance of rain in the Cape Canaveral forecast - and it was raining - but they launched right on time anyway.  Rain is really only useful in telling you something about the air mass the rocket is going to go through; hail, cross winds or wind shear are what matter in terms of damaging the vehicle.  

Since the weather was either going to scrub the mission or was going to make it too cloudy to see anything, we didn't get out of bed and found the video to watch when we got up.  This was the last Falcon 9 launch of the year, the 31st launch for the year (last year was 26), and just under nine minutes after liftoff, the 100th time they successfully landed the booster.  To add just a little more coolness, today was exactly six years since the first successful landing of a Falcon booster was achieved on December 21, 2015. That was a landing on land, not a drone ship, which didn't happen for another four months: April 8, 2016.

In the six years since December 2015, Falcon booster landings have become not just routine but expected.  The factory in California that builds Falcon 9s almost builds nothing but second stages.  Four boosters have launched nine or more missions.  In addition to those 100 landings, there have been only four other Falcon boosters that have not been recovered: one was intentionally ditched because it was carrying a payload so heavy that to get it to orbit required all the fuel used for the landing, and three were lost due to hardware failures. 

I still get a kick out of watching it.  I practically have a deck of cards to score the landing like an Olympic gymnastics judge.  When any other launch vehicle takes off from the "Rocket Ranch Up The Road" I'll watch it, but it's just a let down to not come in and watch them land the booster. 

And I got a kick out of this video, going back to that first booster recovery of that Dec. 21, 2015 mission.  The pure emotion is awesome to see. 



  1. With all of the political crap, pandemic crap and general negative vibes going on the last few years, it is immensely satisfying to watch SpaceX accomplish so much, in such a seemingly smooth manner. It's a powerful example of actual competence in an endeavor.

  2. A number of years ago, they launched an Atlas in a rain storm. Lightning struck the vehicle during ascent, and it went explodey!

    1. That was in the days my wife was working the unmanned side and watched it happen.