Weather or Not

So Emily Lakdawalla from The Planetary Society tweeted something the other day:

Simple enough. Surely that’s a statistic that NASA or the Air Force has lying around somewhere. So I do some digging and come up with…


Nothing.


Nada.


Zip.


Zilch.


Now maybe it was my Google-fu that failed me, and the data is sitting on a backwater server somewhere collecting dust. The best information I could find was the Spaceport Weather Data Archive which has, among other nifty things, a historical log of lightning strikes in the area of the shuttle pads. So I passed the link along and went on my merry way.


It bugged me though, that of all the data NASA tracks and distributes, historical launch probabilities are not among them. Even if the only use was to satisfy the curious, I’d pay 3 3/4 Empire State Buildings* for it. So I decided to do it myself.


I began with the most visible and most well attended launches out of the Eastern Range: the space shuttle. I started working backward through Wikipedia. I had seen that the entry for STS-135 included a launch attempt table. Unfortunately, in true Wikipedia fashion, there is no consistency among articles on similar topics. After a few missions, these handy tables petered out and I was down to digging scrub dates out of sparse paragraphs. Then I got lucky while double checking a reference: Bill Harwood at Spaceflightnow.com had compiled information for every launch up to the final flight of Columbia. It was all over but the number crunching.

The verdict? As I had expected, April is the worst month to launch a shuttle. The spring weather patterns in Florida are against it. The next worst was December. This surprised me. I had expected April and May to be close together. December, on the other hand, tends to be a fairly benign month for weather. So what’s going on?


First of all, despite there being 135 launches to work with, this isn’t actually a lot of data to try to see trends over a 30 year period. April is tied for the most launch attempts in a month at 29, while NASA only tried to launch a shuttle 13 times in May. Of the 29 April attempts, ten were scrubbed due to weather, but ten were outrightly successful on-time launches. December only had 6 weather scrubs, of 18 total attempts. Ideally, NASA would have attempted launches an equal number of times per month to make my math easy. This would have allowed a pattern to jump out. Reality, alas, is another matter.


Second, the rules governing a launch are ever-changing, and depend on what vehicle is flying and what its mission is. The shuttle had very stringent launch requirements. Not only did the weather at the pad have to be acceptable, the weather at the runway 7 miles away had to be good in case of an abort. Additionally, the weather at at least one of the Trans-Atlantic Landing sites had to be OK!** (Yes, the rain in Spain could ground the space plane.) Early in the shuttle program launch windows were typically long enough that a popup thunderstorm could be waited out, but as NASA focused on building the International Space Station those hours long windows dropped to ten minutes, increasing the likelihood of a scrub.


Increasing scientific knowledge has also changed the rules. It’s been known since Apollo 12 was struck twice during liftoff that lightning could be dangerous. The rule then simply became “don’t launch if bad weather is 10 miles away.” Finally, after a Navy satellite was lost after Atlas-Centaur 67 was struck and subsequently destroyed in 1987, major work went into understanding the interaction between lightning and rockets. This has let launches go ahead when, to a layman observer, the weather looked poor but was actually safe. Those in attendance for the final two shuttle launches and their attendant cloud decks understand this quite well.


In order to fully answer Emily’s question it would be helpful to add data from each launch, manned and unmanned, out of Cape Canaveral over the last 50-plus years. Unfortunately that data is scattered, if it even exists for some of the earlier launches. Now, at least, it’s tabulated for shuttle. 


I'm including the spreadsheet I used to generate the above results here. Have a look. Chew on it. And, hey, let me know if you happen to have any spark (heh heh) of insight you'd like to add!


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*Comparative size of the VAB. 
**In the data, I classified scrubs due to poor TAL site weather as “technical” since it’s a scrub due to an idiosyncrasy of the shuttle program, not a reflection of weather at the launch site interfering with an attempt.

Dragon's Breath

The dragon wakes, carefully prodded out of her slumber by her masters. They feed her a slow trickle of food: an appetizer for the feast to come. She lets it flow through her, letting its chill taste permeate her every pore. 

She stretches. She is fully awake now, and ravenously hungry. Her masters see this and are pleased. Far away, an alarm trills. They may control her, but yet they fear her, for they know what she will do with the bounty she is about to receive. 

Finally, the head master gives the word. The bounty is released! She drinks it in as fast as she can and belches out great gouts of fire! She strains against her chains. Freedom is in her reach! But no, the bonds are too strong. Her cage once contained the mighty ancients: dragons far more powerful than she. She will not fly away today. So she relaxes, content to prove her mettle to the masters. 

Far too soon, the meal is over. The food is withdrawn. The fire from her mouth abates to a wisp of smoke, and her cage is bathed in cooling water. The dragon returns to her slumber. She has served her masters well. When next she dines she will be free.

This was inspired by my work at Stennis Space Center, outside New Orleans. For the last 50 years rocket engines have been tested on Stennis’s stands. Yesterday, the folks at Stennis tested the new J-2X rocket engine on the same stand that hosted space shuttle engines and the full second stage of the Saturn V. Today, NASA tweeted the video. Enjoy!

On Atlantis, More Is Said

Ok, I’m back. I managed to upend my life a bit since my last post, but that hasn’t stopped my brain from working. 

A few weeks ago I received an email saying that employees could sign up to tour the crew module of one of the orbiters as it’s being processed for museum display. So I did what any red-blooded Rocket Nerd would do. I said, “OH HELL YES!”

My slot was scheduled for last Wednesday. I had successfully fended off all the meetings that had attempted to be scheduled over the time (not just out of greed: if I gave less than 48 hours notice, I’d forfeit the tour, period). As I drove up to the Orbiter Processing Facility I was nervous, almost like I was going out on a date. These craft are special, as I discussed in my first post, and having the opportunity to not only see one but step inside seemed too good to be true. 

Finally, the rest of the tour group showed up and our escort walked us inside and steered us toward High Bay 2, where Atlantis stood. 

OPF 2 Entrance

I had been on vacation when she landed, so I was glad to have another chance to see her. Our escort walked us past the ops desk and up the stairs that led to the platforms enveloping the nose. As I’d expected, the forward thruster module had been removed to be decontaminated, leaving a gaping hole in Atlantis’s nose. 

Atlantis's Nose, sans Forward RCS Module

We were then walked around to her starboard side and up to another platform. This revealed the payload bay. The doors themselves were hidden by structure, for good reason. Like the Canadarm, the doors cannot support their own weight in Earth’s gravity, so special equipment has to be used to open them. I was awed by the size of the bay. You always hear that it can contain something the size of a school bus, but seeing it firsthand truly drives that point home.

The Payload Bay

Our escort led us on. I looked down to see that I was walking OVER the flight deck windows. I only got to savor that thrill for a moment before we were prodded on. 

Looking down at windows that looked down on the world

Finally we stood at the air shower where the technicians would have any residual dust cleaned off their bunny suits before entering the orbiter. Those requirements had been lifted once the shuttles left flight status, so all we needed to wear were booties slipped over our shoes. After a few minutes we were signed in and led around the corner from the shower. Before us stood the hatch. The technician gestured us inside. 

The Hatch

Rocket Nerd added for scale

The hatch is not large, so we had to crawl through. But I was INSIDE. I stood up in the mid deck, barely clearing the ceiling, and looked around. The mid deck is small, about the size of a small bedroom, and according to the technician, completely gutted. All of the lockers, seats, and crew support equipment had been removed. Add all of that back in and two thirds of that space is full—before astronauts. I struggled to find an angle that would give anything resembling a sense of the size of the mid deck, but did not fare well. 

Mid Deck Forward Bulkhead

Mid Deck Aft, standing at forward bulkhead

The airlock hatches were open, so I could see into the payload bay. How many times had I seen the flag on the aft bulkhead growing up? 

View through the airlock

After a few minutes, we were led up the ladder to the flight deck, which makes the mid deck spacious in comparison. I could touch the pilot’s seat and the aft control panels without coming anywhere close to stretching my arms. The seats didn’t look all that comfortable either, with some wafer thin padding over steel plate. 

Flight Deck aft station. I am sitting between the Commander and Pilot Seats.

Pilot Seat. Cushy.

Commander's Seat

It also struck me that most of the instruments screamed ’70s technology, despite Atlantis being the first orbiter to fly with the “glass cockpit” upgrades that reduced the amount of mechanical instrumentation the crew had to deal with. One panel labeled “event timer” displayed numbers on individual dials showing through holes in the panel cover—something I last remembered seeing in Roger Moore-era Bond films. But as we were being ushered back down the ladder, something a little more modern caught my eye…

Dude...

We were led back out the mid deck hatch and down the platform stairs. We were shown the aft compartment and walked beneath her, where the small dings in the tiles from her final launch were evident. And then we were back outside. I walked back to my car with mixed feelings. As elated as I was to be able to board Atlantis, the reason the opportunity existed still stung.

(Apologies to Alanis Morissette. My pun habit is uncontrollable…)

The Clock Has Started

Randall Munroe posted this the other day on his webcomic xkcd.com. 

Today much of the country is celebrating a holiday based on a battle that is a historical footnote (and using it as an excuse to drink a beer that is a close cousin of Aquafina). But something else happened on May 5 that, while it may eventually become a historical footnote itself, still merits far more celebration than it gets. 50 years ago today, Alan Shepard became the first American (and second human) in space.

He also appears on the third step up in Randall's graph above. 

The statistic he graphs should not look like that. It should look more like this:

I am convinced that eventually it will. The only variable is time. In Shepard's words as he lifted off 50 years ago today, the clock has started. He and Gagarin demonstrated that we can leave Earth. We must leave Earth. Only when this:

becomes a meaningful statistic can we ignore the clock Shepard started.

Change Is Coming

I drove out to Pad B today.  I hadn't had a close up look at the pad since demolition began. The difference is amazing.


Today:

Versus October 2009, when Ares 1-X was on the pad:

I realize this is clearing the way for future use (first for Constellation, now as a "21st Century Launch Complex",) but after 30 years of seeing the pad configured for shuttle it's quite eerie. 

Not Because They Are Easy: STS-49

One of the things I absolutely love about being a space nerd that works where I do is that every time I turn around there's a tiny bit of history staring me in the face. This tends to have the unfortunate side effect of plunging me down the Wikipedia rabbit hole as I chase a juicy tidbit. Not only does this feed my geek, it serves to remind me that, despite 50 years of space travel, it is far from routine. Years of training cannot prepare astronauts and ground personnel for every situation, so improvisation and ingenuity abound. Yet very few of these occasions have entered the public consciousness. I'd like to change that. After all, we do these things because they are hard!

Around the corner from my office, this picture hangs on the wall. At first glance, it's one more shot of spacewalking astronauts doing their job in the shuttle payload bay. Except there are three of them, and I know spacewalks in the shuttle era are normally conducted in pairs. So what mission was this? What was going on? I had to go all the way back to the maiden flight of Endeavour to find out.

Endeavour rocketed into space for the first time on May 7, 1992. The mission was straightforward: a quick pit stop to rescue a communications satellite that had been stranded in a useless orbit by a launch failure, then a couple of days' worth of spacewalks to experiment with construction techniques for what would eventually grace our skies as the International Space Station. 

On May 10, Endeavour rendezvoused with the INTELSAT VI satellite. Mission Specialist Pierre Thuot rode to the satellite aboard the Canadarm (RMS in the lingo) to attach an adapter bar that would allow the RMS to handle the satellite and bring it into the payload bay, where Rick Hieb waited. There Thuot and Hieb would attach the rocket motor that would send the satellite on its merry way.  However, when Thuot tried to grab the satellite, it began to move away from him. Further attempts to capture it turned this movement into a severe wobble that made it too dangerous for the astronauts to continue.  

The next day, after ground controllers stopped the satellite's motion, they tried again with the same amount of success. The engineer who had designed the adapter blamed the satellite manufacturer for not providing NASA with correct data on the satellite. Thuot himself later described INTELSAT VI as "much more dynamic than our training had led us to believe."

The defeated astronauts returned to the shuttle cabin, where they joined their crewmates in pondering the situation. Finally, working with Mission Control, they hit upon a possible solution: by placing Thuot on the arm, Hieb on the starboard rim of the payload bay and a THIRD spacewalker, Tom Akers, on a platform fashioned from the space station assembly experiment, they could grab the errant satellite by hand and guide it into the payload bay. 

Given a go after a team of astronauts had rehearsed this procedure on the ground in Houston, Thuot, Hieb, and Akers exited the airlock on what was coincidentally the 100th spacewalk in world history. Shuttle commander Dan Brandenstein guided Endeavour within feet of the free flying satellite. Finally, after 15 minutes of watching the satellite slowly spin in front of them to time their grab, the three astronauts snagged the satellite and brought it in. 8 hours and 29 minutes after the spacewalk had started, the astronauts returned to the shuttle cabin having attached the rocket motor and completing their mission.  The duration of this EVA set a record unmatched until 2001. 

Endeavour flies a final time next week to deliver supplies and a potentially history making science experiment to the space station whose early development work gave the crew of her maiden voyage the tools they needed to complete their mission. It's good to see history come full orbit!

Sources:

http://en.wikipedia.org/wiki/STS_49 A good jumping off point.

http://science.ksc.nasa.gov/shuttle/missions/sts-49/sts-49-press-kit.txt What was supposed to happen.

http://articles.latimes.com/1992-05-13/news/mn-1687_1_rescue-attempt Thank you for having a free archive, LA Times.

http://uu.cx/flight/49/ Excellent detailed article about the mission.

http://spaceflight.nasa.gov/spacenews/factsheets/pdfs/EVACron.pdf Walking to Olympus. Chronology of Human EVAs. 

http://www.archive.org/details/postflight_press_conference_sts-49 The postflight video briefing. Can the crew get any drier describing their mission?

Edit 4-21-11: My mistake. My poor fried brain had the wrong picture. It has been corrected.

30th Anniversary of Shuttle

I saw a Marine general cry today. 

Let me back up. Today was the 30th anniversary of the launch of the space shuttle Columbia on STS-1, inaugurating the Space Shuttle program. This year that program comes to an end. Emotions are high. Many of the workers at KSC have worked closely with the orbiters--some from that first launch--and see them as their own. Many of these same people face an uncertain future and will likely lose their jobs, if they haven't already. 

Understandably, the astronauts who have flown aboard these vehicles feel a strong tie to them as well. These orbiters have been their home, their refuge from the harshness of space. So perhaps it's fitting that an astronaut was tasked to determine their ultimate fate, the aformentioned Marine general, Charlie Bolden. 

Today, standing in front of the hangar where Atlantis is being prepared for its final mission, Bolden announced where the orbiters would go after they retire. More than once he choked up as he spoke, the emotions of the day overwhelming him. And, sitting in the audience, I knew how he felt.

It's a big year for me. 30 years ago, my mom was 7 months pregnant with me. STS-1 is the only space shuttle flight I was not alive for. I was born too late for the moon landings, so the shuttle program WAS manned space flight as I grew up. I only vaguely remember watching Challenger as it happened, but was glued to the TV two years later when Discovery roared triumphantly off the pad. I remember the deployment of a magnificent new telescope, and then the flight to give it glasses. I watched the shuttle dock with Mir, then begin construction of the long-awaited International Space Station. 

I was always a space case. I devoured Star Trek and other science fiction growing up. But always there was the real thing, the pathway to those imagined futures. I longed to see a launch in person. I longed to work for NASA, to see the shuttles. I daresay this is a big part of why I'm an engineer today.

And I made it. I work for NASA at KSC. I have been spitting distance from each orbiter, enjoyed the view from the top of the pad structures, watched a close friend's 8 year old son goggle at the orbiter wing he was standing under during last year's Family Day in the same way I stared at the TV watching STS-26.

Tomorrow those onstage and in the audience will be back to our normal roles as managers and employees. But today, we were merely people who had been touched by five vehicles that changed our lives.