Tuesday, 16 May 2017

Teacher's bits: Overview of the Space Race

My grade 9 history class is covering the Cold War this term, and one lesson needed to focus on the Space Race. This was a problem for me, because I simply have way too much of that inside my head. I love this stuff. I kept trying to think of ways to focus on only the key essentials, but I always slip into massive digressions that would easily fill a whole lesson on their own. Left unchecked, I'd happily discuss nothing else all year. And my grade 9s are especially chatty and unfocused, so they'd normally have a million questions, digressing totally off topic.

So, I needed to script an unusually tight lesson plan, forcing myself to stay on topic, with a set of pre-planned slides to illustrate what I was talking about, and specially asking the kids to write down any questions they had to ask me afterwards, rather than interrupting my flow. That's not my usual style at all, my normal teaching is very similar to my game mastering style (intentionally; it was the public speaking foundation I began with), with a very improvisation-friendly skeleton of key points to hit, however seems most appropriate to the audience of the moment. I've tried scripted, rehearsed lecturing before, and it didn't suit me very well. But for this topic, I felt I had no choice.

In practice, I felt it went fine. It wasn't nearly as deep as I would have enjoyed, but we weren't doing this for me.

So, for anyone else needing a lesson plan on the Space Race, here is my approx. 30 minute overview lesson, emphasizing the technological roots it had in World War II (the topic we covered in term 1), and mostly covering achievements in human spaceflight. I was especially glad I happen to have read Breaking the Chains of Gravity last year.

I've also freely thrown in a lot of technical names, especially of different rocket types, but that's not something the students need to worry about. Much more import is the general flow of broad trends and national goals.

Images are mostly taken from Wikipedia, though I've combined a few into collages.

(The format is slide image [click to embiggen], slide title as caption, and then the discussion points that go with that slide.)

Origin of rockets

  • Gunpowder rockets invented in 13th century China.
  • Used for centuries as entertainment and as a simple weapons.

Artillery example
  • After WW1, Treaty of Versailles included a specific rule against Germany owning any artillery guns.
  • Artillery was one of the most important types of weapons for killing at long distances (10+ kilometers; bombing Cresta from Concord).
  • But the Treaty of Versailles didn’t mention rockets at all, so the Nazi government hired a group of amateur rocket scientists to develop rocket artillery.
von Braun (suit)

  • Leader of the German rocket scientists was Wernher von Braun.
  • They were mostly interested in exploring space, but were happy to take the army’s money to build weapons instead.

  • In 1942, they finally had the V-2 rocket ready.
  • It could carry a bomb 300km away (more than halfway from Joburg to Durban).
  • Small number of scientists couldn’t make thousands of weapons needed for war, so concentration camp prisoners were used as slave labour to build V-2s.
  • Up 60 000 slaves worked in a hidden underground factory, called the Mittelwerk.
  • Around 9000 people were killed by V-2 attacks. 20 000 people died working at Mittelwerk.

first photo of Earth from space, 1946
  • V-2 was also the first human machine to go into space. A test launch in 1944 reached 176km above sea level.

Captured von Braun, Korolev, Bumper
  • During last months of WW2, Allies rushed to grab Nazi technological secrets, including von Braun’s scientists and rockets.
  • Von Braun chose to surrender most scientists to USA, moved there.
  • USSR only caught a few scientists, but got most of the rocket test facilities. Moved these to USSR.
  • USSR research headed by former political prisoner, Sergei Korolev
  • Both started trying to improve on German designs.

Basic rocket science jargon
[A technical interlude to clarify some very basic rocket science terms, without which, a lot of this discussion doesn't make much sense.]
  • Suborbital flight: Up, into space, and then down again. Relatively easy for smaller rockets.
  • Orbit: Go up, move sideways fast enough that you don’t come back down again. Much harder, needs much more powerful rockets.
  • V-2 could only do suborbital.
  • Rockets have at least two main parts to them: Launcher and payload.
  • Launcher is the flamey bit that moves the payload off the ground and into space.
  • Payload is the thing on top that will do the job you want it to do (could be bomb, communication satellite, observing (spy or science) satellite, crew capsule)
  • A human isn’t that heavy, but air, water, food, temperature control, radiation protection, control panels, seats, windows, etc., all add mass.
[Sub-interlude to explain why 1957 was an especially crucial year for spaceflight]
  • 1957 was declared the International Geophysical Year, when scientists from around the world would cooperate on major studies of the whole Earth. Leaders of the USA and USSR both saw this year as an important opportunity to get research satellites into orbit.
  • If the international community considered research satellites normal and legal, then it would be far easier to sneak some military spy satellites into orbit too.
Soviet headstart, Sputnik 1, Sputnik 2, Luna 1, Luna 2, Vostok 1
  •  Korolev developed V-2 technology into very powerful rocket called the R-7, much bigger than any Western rocket of the time.
  • R-7 could carry nuclear bombs hundreds of kilometers away.
  • Also powerful enough to put satellites in orbit. Science satellites could study the Earth and space, but could also be spy satellites to watch other countries’ militaries and find their secrets.
  • R-7 launched:
    • Oct 1957: Sputnik 1, first ever artificial satellite.
    • Nov 1957: Sputnik 2, first satellite to carry an animal, the dog Laika. Laika died within hours due to overheating.
    • 1959: Luna 1 and Luna 2, first successful probes to the Moon. Luna 1 flew past the Moon, Luna 2 was intentionally crashed into the surface of the Moon.
    • 12 April 1961: First human in space, Yuri Gagarin, on Vostok 1.
    • Several other “firsts”.
  • R-7s are still used today.
US headlines

  • Western reporting on Soviet launches was often ‘alarmist’ – very fearful, emphasizing lack of US ability to keep up, and implying huge risk of unstoppable Soviet nuclear attack, falling from the sky at any time.
  • Soviet media published less about their own setbacks.
US response, X-15, Mercury
  • US companies had already been working on spacecraft since von Braun and the V-2 were brought across, but American public and politicians suddenly demanded much faster results.
  • Research on the complicated X-15 rocket plane was largely ignored, in favour of the simpler, smaller, quicker to build Mercury capsule.
  • But early on, the US didn’t have a rocket powerful enough to put the Mercury capsule into orbit, so they just launched suborbitally on the weaker Redstone nuclear launcher, basically an enlarged V-2. The first US astronaut launched a month after Gagarin.
  • Even when they put Mercury capsules on bigger Atlas rockets the next year, and got Americans into orbit, it still wasn’t as much or as high as the Soviet R-7 could manage. Vostoks kept doing more than Mercuries could.
  • Americans remained fearful. President Kennedy declared the US would win the Space Race by putting humans on the Moon before 1970.
US progress, Gemini, Apollo-Saturn IB, Apollo-Saturn V
  • With the Moon target, US rockets and spacecraft kept getting bigger.
    • Mercury was upgraded to Gemini, and then the two-piece Apollo set.
    • Redstone and Atlas were replaced with the larger Titan II nuclear missile, and then the much larger Saturn IB. In the late 1960s, US launchers were finally bigger than the Soviet R-7.
  • For the Moon missions, Apollo needed the biggest launcher ever, the Saturn V.
  • Neil Armstrong became the first human to set foot on the Moon on 20 July 1969. 12 Americans on 6 Apollo missions until 1972, got to walk on the Moon.
  • ...and then US pretty much decided they had won the Space Race, and there was no longer any money to return humans to the Moon, let alone any deeper to Mars, Venus, or other planets.
Soviet N1, Salyut 6 station and a Soyuz
  • The Soviet Moon launcher, the N1, equivalent to the American Saturn V, was a failure. It crashed and exploded on every test launch. With no huge launcher, the Soviets couldn’t send any people to the Moon.
  • The new Soviet Soyuz spacecraft was also too unreliable for the first few years to be sent to the Moon (though it was later fixed and is still in use today).
  • Without the technology to reach the Moon, the USSR changed its goal from Moon landings to long-term space stations in Earth orbit. The first space station, Salyut 1, was occupied for 2 weeks in 1967. More space stations followed, and today’s International Space Station still uses some of the same components as the original Salyut stations.
  • Arguably, the sustained Soviet/Russian station operations have achieved more in the long run than the quicker US burst to reach the Moon and then stop.
  • After the Moon Race ended, both sides felt less sense of competition, and were finally able cooperate. First ever international docking, in 1975, between Soyuz 19 and Apollo 18.
  • After the Cold War ended, cooperation increased, with US space shuttles visiting the Russian Mir station during the 1990s.
  • US, Russia, Europe, Japan and Canada cooperated in assembling the enormous structure of the International Space Station, starting in 1998.
Proposed Deep Space Gateway lunar station

  • Plans for international Moon station, Mars missions? 
Chinese, Indian 21st century spacecraft
  • Several other countries have developed launch capabilities (SA sub-orbital launches in 1989/1990), but the only other launches of humans so far are by China, starting with Shenzhou 5, in 2003.
  • USA refuses to do space missions with China, so China built its own stations.
  • India also has partly developed crew capsule that could carry people a few years from now.

Sunday, 23 April 2017

Happy 50th, Soyuz!

23 April 1967, 50 years ago today, the first crewed Soyuz spacecraft launched. Three days ago, the latest crewed Soyuz spacecraft launched and docked with the ISS. We've been flying to space in this same design for a full 50 years now, and more of them have been built than any other type of spacecraft by a huge margin - it's the VW Beetle of human spaceflight. Uncrewed test launches of Soyuzes had begun in November 1966, so by that measure, Soyuz already passed its 50th anniversary last year. But I'm more inclined to measure crewed spacecraft by when they're actually inhabited in space.

The closest any other crewed spacecraft comes to that longevity is the DOS space station core module (reaching its 46th crew-carrying anniversary this June), which featured in most of the Salyut space stations and the Mir space station, and is currently part of the ISS. Soyuz and DOS were designed to work together, so it's appropriate but remarkable that they're still doing so today. You'll see in the visual history below how much the two vessel types have been connected.

By coincidence, today is also the 46th anniversary of Soyuz 10's unsuccessful docking attempt with Salyut 1, the first Soyuz-DOS meetup in orbit. Later this year we'll see the 60th anniversary of the R-7 family of rockets, the oldest orbital launcher there is, variants of which have launched all crewed Soyuzes and most uncrewed Soyuzes, plus all sorts of other things.

The longest serving US spacecraft, the Space Shuttle Orbiter, lasted 30 years, and the 5 of those that were built got into space 134 times, accruing a total spaceflight time of just under 1 331 days. Flying only once each, 132 Soyuzes have gotten their crews into space 132 times so far, adding up to 14 956 days of human spaceflight time, and counting. Nine more Soyuzes are scheduled to launch, keeping them in use until 2020. Adding in all the uncrewed Soyuz and Soyuz-variant launches more than doubles the number of times the Soyuz family has flown; there were no uncrewed Space Shuttle flights. So, it's not the simplest comparison.

The second most numerous spacecraft design was the Apollo CSM, of which a mere 15 were launched into space with humans on board.

And while the latest version of Soyuz is definitely modernised and digital, it's also still clearly very close to its original 1960s form; consider below the full evolution of the Soyuz:
(Click to embiggen.)
Top row: Crewed variants of Soyuz.
Bottom row, left group: Major uncrewed variants of Soyuz.
Bottom row, right group: Crewed variants of Tiangong.
(Image credit mostly goes to historicspacecraft.com, with a couple bits from elsewhere and/or modified by me.)

Note that I've included more than just the crewed versions. Soyuz has been around so long, it's been mutated into a few different forms - most import of all is undeniably the Progress cargo vessel. I've also included China's larger Tiangong spacecraft, which was intentionally based on the Soyuz layout, and operates in a very similar way. It is arguably part of the Soyuz family.

One weird thing going through all of the Soyuz missions brings up is how openly sexist the Soviet and Russian space programs have been. Hundreds of people have travelled on Soyuzes, but only 3 of them were Russian women (less than 1 per decade!), and no Soyuz has ever had a woman commander. There are plenty of stories floating about of nasty sexism in Soviet/Russian spaceflight, and they even chose to put it in some of their public relations videos. One case leapt out at me from the Soyuz TMA-11 near-disaster, discussed towards the end of this post. The Roscosmos general director at the time publicly blamed the fact that the vessel concerned had too many women onboard (one American, one South Korean), and said he'd work to prevent this from happening again. You don't joke about crap like that, but I suspect he wasn't kidding.

Because Soyuz has been around for so long, it's hard to discuss absolutely every flight and every crew. At the same time, one of its virtues has been how uneventful and routine most of its operations have become. I think the best way to celebrate this 50th anniversary is a simple visual history of some of the major Soyuz moments. Even condensed this way, it's still a lot.

1966-11-26 (no image available): Kosmos 133, the first uncrewed Soyuz test vehicle, launches. It malfunctioned in orbit and was intentionally destroyed before it could crash. Two further uncrewed test launches followed, both with serious systems failures.

1967-04-23: Soyuz 1 launches, with a single pilot, Vladimir Komarov. Space Race pressure had rushed a premature launch, and the flight was a complete disaster, with several technical failures forcing an early landing. But the parachute failed too, and Komarov simply fell straight from orbit to the ground, the first fatal spaceflight.
1968-10-30: Soyuz 3 lands safely, the first successful crewed Soyuz landing. Soyuz 3 had met up with the uncrewed Soyuz 2 in orbit, but failed to dock with it. Soyuz was the first Soviet spacecraft designed for orbital docking, so many of its early flights were focused around docking experiments.
1969-01-16: Soyuz 4 and Soyuz 5 dock in orbit, allowing the first crew transfer from one spacecraft to another, and therefore also the first time that cosmonauts had landed in a different vessel from the one they launched in. They had to spacewalk along the outside of the spacecraft to get from one to the other, as there was no internal hatch between the two yet.
1971-04-23: Soyuz 10 attempts to dock with Salyut 1, the first ever space station, but fails to completely do so. Then they had trouble getting completely loose from the station's docking equipment again, but eventually got home.
1971-06-30: Ground crews perform CPR on the already dead crew of Soyuz 11, shortly after it landed. Soyuz 11 successfully docked with Salyut 1, making it the first occupied space station in history. The crew of Georgy Dobrovolsky, Vladislav Volkov and Viktor Patsayev spent 22 successful days working on the station, but after they undocked Soyuz 11 to go home again, their spacecraft began to rapidly depressurize, asphyxiating the crew in seconds. They are the only humans to have died in space, and while there have been further Soyuz accidents, this was the last fatal one.

1974-07-03: Soyuz 14 launches, docking with the Salyut 3 space station, probably the only crewed spacecraft to be armed.

1975-01-12: Soyuz 17 docks with the Salyut 4 space station for a month. A little over 3 months later, Soyuz 18 docks with Salyut 4 (pictured), making it the first Salyut to receive more than one crew. They were followed in November that year by Soyuz 20, which I believe was the only conventional* Soyuz ever with a fully non-human crew: Tortoises and fruit flies were kept inside as part of a biology research project, while the Soyuz was given a long-duration (90 day) engineering test by remote control. Since the non-human animals never entered Salyut 4, it's a matter of precise definition whether they were its 3rd group of visitors or not.

(*By conventional, I mean the Earth-orbit crew ferry sort of Soyuz, normally used by human crews. In 1968 there were two variant Soyuzes of the Zond lunar program that also carried non-human animals. Zond 5 successfully carried tortoises, wine flies and meal worms around the Moon and safely landed back on Earth. Zond 6 also flew around the Moon with similar passengers, but on return to Earth, it suddenly depressurized, killing everything inside, and then also suffered a prachute failure. If Zond 6 hadn't failed, and if Apollo 8 hadn't beaten them to it, the next Soyuz 7K-L1 might have been allowed to launch humans around the Moon. There may have been animals on one or more Progresses too, but I haven't dug that up yet.)

1975-04-05: The crew of what is now officially only called Soyuz 7K-T #39, but also variously known as Soyuz 18a, Soyuz 18-1, or the 5 April Anomaly, and what had orginally been launched as Soyuz 18 (for a few minutes, anyway). Due to a mechanical failure and subsequent launch abort, just after it reached space, this accidentally became the only crewed suborbital Soyuz launch. The re-entry module landed on a snowy slope and rolled down it for a while, but the crew survived.

1975-07-17: Soyuz 19 and Apollo 18 dock in orbit, the first international spacecraft docking. They didn't do much up there, but their long-term influence has been enormous.
1976-07-07: Soyuz 21 becomes first spacecraft to dock with the Salyut 5 space station. Soyuz 23 failed to become second to dock there, and on landing accidentally became trapped under the ice of Lake Tengiz, the only crewed Soyuz water landing. It took 9 cold hours to safely get the crew out. Soyuz 24 later made the actual second (and final) successful docking with Salyut 5.
1977-12-11: Following the failure of Soyuz 25 to dock with Salyut 6, Soyuz 26 becomes first to dock with the new space station. In total, 17 Soyuzes successfully docked with Salyut 6, as well as one more failed docking by Soyuz 33. Soyuz T-4 (pictured) was the last to undock from the station, on 1981-05-26. Salyut 6 was the first space station to allow multiple simultaneous dockings, so that Progress supply ships could make deliveries to crews, and multiple crews could board the station at the same time, without having to leave the station unoccupied. This was first demonstrated when Soyuz 27 arrived a week before Soyuz 26 departed. Salyut 6 was also notable for beginning the Interkosmos program of various international guest cosmonauts joining the Soyuz/Salyut crews on a regular basis.
1982-05-15: Soyuz T-5 is first to dock with the Salyut 7 space station. In total, 10 Soyuz spacecraft successfully docked with Salyut 7, with only Soyuz T-8 failing to. Salyut 7 had fewer Soyuzes visit it than Salyut 6, but longer visits meant that Salyut 7 lasted for longer than its predecessor. Soyuz T-14 is pictured docked to it here.
1983-09-26: People watch the critical escape of what is now officially only called Soyuz 7K-ST #16L, but also variously known as Soyuz T-10a or Soyuz T-10-1, and what had been 90 seconds short of launching as the original Soyuz T-10. This Soyuz was the only case of its launch escape system saving a crew, when the launch rocket exploded underneath it. The crew were flung away and landed unharmed, and their spacecraft's orbital module was even recycled for use on Soyuz T-15.
1986-03-13: Soyuz T-15 launches (with its recycled orbital module) and becomes first to dock with the Mir space station. They then left Mir's lights on, flew the Soyuz to Salyut 7 to dock with it for the final time, stole a bunch of useful equipment for Mir, and then flew their Soyuz back to dock with Mir again. This makes Soyuz T-15 the only spacecraft so far to fly back and forth between different space stations.
Following Soyuz T-15, another 29 Soyuzes visited Mir. During the same period, three of the US shuttles made 9 dockings with Mir, the first international dockings since 1975's Soyuz-Apollo meeting. Soyuz TM-30 was the last to undock from Mir, on 2000-06-15. Lots of interesting things happened on Mir, but the fact that there's not much more to add about Soyuz specifically is an indication of how reliable and routine Soyuz operations had become by this point.
2000-11-02: Soyuz TM-31 is the first Soyuz to dock with the International Space Station, carrying the crew known as Expedition 1. Three US shuttles had preceded it since December 1998, making 5 dockings before Soyuz TM-31 arrived. However, that Soyuz visit marks the start of the station's continuous occupation (over 16 years without being empty once), as shuttle visits could only be a couple weeks long before returning to Earth, while Soyuz had been made suitable over the Salyut/Mir years to remain docked at the station for 6 or 7 months at a time.
Today, 2017-04-23, there are two Soyuzes docked at the ISS (Soyuz MS-03 and Soyuz MS-04), and their combined crews are its Expedition 51. The three US shuttles visited the ISS 37 times altogether, while 50 Soyuzes have so far docked there, along with a whole lot of different uncrewed cargo vessels. Since the shuttles retired in 2011, Soyuz has been the only way to get people to and from the ISS (apart from making a deal with China to use Tiangongs, maybe). In the next few years, Crew Dragons and Starliners are due to start bringing crews there too, and possibly also Federatsias.
One worrying but luckily never disastrous malfunction struck both early and late Soyuzes in similar ways during their re-entries. Soyuz 5, back in 1969, and then both Soyuz TMA-10 and Soyuz TMA-11 in 2007/2008, all had their service modules fail to separate from their re-entry modules (step 3 in the diagram), causing them to fall uncontrolled, with their heat shields facing the wrong way. Happily, in all three cases, the heat of re-entry was enough to melt through the last connections to the service module, breaking it free in time for the re-entry module to swing back around to face the correct direction, before the weaker top end of the re-entry module also melted through. Crews suffered injuries and landed well off target, but survived.
Several Soyuz replacements have been proposed over the years, but it looks like Russia is finally really going to switch to a new spacecraft. The larger Federatsia spacecraft is not expected to carry humans until 2024, at the earliest, leaving a four year gap after the last Soyuz lands. Federatsia won't launch on a Soyuz rocket (nor any member of the R-7 rocket family), and it will launch from the new Vostochny Cosmodrome in eastern Russia, rather than the Baikonur Cosmodrome in Kazakhstan that every crewed Soviet/Russian launch to date has started from, so it'll see a lot of changes beyond the spacecraft itself.
What strikes me in all of this is that Soyuz is almost never the hero of the story, especially when it's working properly. Early on, it's not really doing too much very groundbreaking, compared with the drama of the first few years of the Space Race, or the ostentatious Apollo Moon missions. Soyuz was originally conceived for Moon missions too, and then had that taken away. And later on, when Soyuz starts servicing space stations, the stations are most often the center of attention, not their little support craft. The little bit of limelight Soyuz has had since 2011 often comes from (or draws in) angry Americans, raging that they're now forced to hitch rides. They don't seem grateful that old Soyuz is still keeping things moving forwards. But that's the main accomplishment of Soyuz: In a series of tortoise-vs.-hare contests, it's been the sure and steady tortoise.

Friday, 14 April 2017

The unclear meaning of WMD

I wrote an essay back in varsity that led to me co-authoring my one and only published journal article. The essay and article weren't that similar, with the article focused on socially constructed meanings given to nuclear weapons, while my essay had been about weapons of mass destruction in general, and had taken a more elementary look at what these weapons physically do and what this meant they had in common (or not).

A quick look at the standard legal definitions of WMD explicitly holds them to the level of destruction of a nuclear bomb, and yet biological and chemical weapons employed in reality just don't get that destructive. No single device built so far gets as destructive as a nuke (causing somewhere close to hundreds of thousands of casualties from one explosion in a population center, possibly more; the definition will vary with location and situation). That's why they're so scary. In comparison, individual chemical weapons have never caused comparable harm, and even sets of them used together have still fallen orders of magnitude short of nukes. Biological weapons remain mostly useless (compared with both nukes or chemical weapons), a dangerous concept to prepare for in future, rather than a practical reality today.

This doesn't diminish the destruction caused by smaller devices. It also doesn't diminish the cumulative destructive potential of large numbers of small devices (if we're not strictly talking about the effects of a single device, then any army, collectively, is automatically a WMD too). It just means the legal definition is very fuzzy or very stretched.

One possibility this fuzziness opens up is that some very large conventional explosives might legally be classed as WMD. They still won't reach the level of even very small nukes, but they can easily exceed the damage done by the chemical weapons that are already classed as WMD. That, to my non-lawyer mind, would seem to imply that large non-nuclear bombs ought to be considered WMD too (or that the definition needs a major rebuild).

These thoughts came back to me this week, as Syria appears to have made another chemical weapon attack, and the US has dropped its very largest non-nuclear bomb. I can already see the media (and thus the wider public too) getting mixed up about the nature of WMD, and what to do about them. This sort of confusion only makes it harder to discuss intelligent de-escalation or the hypocrisy of violent "peacekeeping". Whether the formal legal definition of weapons of mass destruction changes or not, it may be wise to push the term out of widespread use. It doesn't seem to serve a useful conversational function, and it invites a lot of misleading double meaning.

Wednesday, 12 April 2017

A quick gender analysis of TableTop

I've been slowly catching up on season 4 of TableTop, now that I have a little free time, and I got as far as the episode on Dragon Farkle. What leapt out at me about it was the all-male cast, and this got me thinking that I'd been seeing very few women in season 4. That would be disappointingly unrepresentative, especially for a show that's so far done a great job of showing varied men and women enjoying boardgames together. And among the guys in early season 4 are Tim Schafer and Andy Weir, which was an absolutely fantastic surprise combo for me. But I also wouldn't want to ignore a problematic change in the show, if it was a real change. But how to be sure? Maths!

It was 5 minutes' work to scan through the episode list on Wikipedia, which conveniently lists each episode's guest players. I made a little spreadsheet, sorting the players per episode by apparent gender (which at this distance looks like simply Boys and Girls; a more thorough analysis might split those numbers up further). And that very rushed spreadsheet yielded this graph of gender representation per episode:
Click to embiggen.

Note that the host, Wil Wheaton, is counted as a player in all of these episodes, giving an automatic +1 to the boys (hence the solid blue bottom of the graph); more on this below. Note also that series co-creator Felicia Day also steps in as a guest player occasionally, and I've marked all of her appearances with the symbol F. The standard show format features Wil plus three guest players, and exceptions to this are rare (about once per season). Two-parter episodes come up once or twice per season, but I've counted each of these as two separate episodes here. If the point is to test representation, then getting twice as many appearances as in a single episode should be counted as such.

So, what does it mean? To draw some useful conclusions from the constantly shifting graph, I've drawn out three things:
1. The average number of boys and girls per season. (Includes Wil Wheaton.)
2. The average number of non-Wil Wheaton boys per season.
3. The number of episodes per season that have an exact 50/50 gender split. (Includes Wil Wheaton.)

It would be fruitless to look for the 50/50 gender split without including Wil Wheaton, because of the standard four-player format.

I definitely wasn't crazy to notice a shift away from women guests in the early part of season 4. Episode 4-3 is a brief exception, and then there's a string of mostly-men episodes for a while. But the good news is, season 4 over all is much better.

The Wil-inclusive average gender split for each season is:
S1: 2,9 boys, 1,2 girls
S2: 2,6 boys, 1,5 girls
S3: 2,5 boys, 1,5 girls
S4: 2,5 boys, 1,6 girls
Which looks like it's tending towards equality.

It's even clearer with the Wil-exclusive average gender split per season:
S1: 1,9 boys, 1,2 girls
S2: 1,6 boys, 1,5 girls
S3: 1,5 boys, 1,5 girls
S4: 1,5 boys, 1,6 girls
Unsurprisingly, the boys lose their +1, and viewed this way, only season 1 is particularly unequal.

There are arguments in favour of either including or excluding Wil Wheaton from our count. But either way, the trend is headed in the same direction.

And finally, the number of perfectly equal episodes per season are also tending upwards:
S1: 5 episodes
S2: 7 episodes
S3: 9 episodes
S4: 11 episodes

I have no idea if this is intentional on their part or not, but at least it satisfies my initial concern. Things look sane and reasonable.

One final observation: Appearances by Felica Day seem to be less common over time. That's a pity, because I always enjoy her participation, but I suppose this means they're finding it easier to find new people to fill out their casts.