1. Out of stock on the ISS! :(
2. The emu vs. the eagle
3. Almost squashed by a collapsing rocket

Earlier this month, NASA announced that the first all-female spacewalk ever was supposed to be conducted on March 29 by Anne McClain and Christina Koch. Unfortunately, they've had to backtrack - it turns out there aren't enough correctly sized spacesuits for both women on the ISS! Definitely a goof on NASA's end, but it's more complicated than the headlines make it sound.

Anne McClain via Twitter: "A million dreams is all it's gonna take..."

Spacesuit sizing is actually quite tricky - the suits fit differently in zero-G, and astronauts grow taller in space without gravity (McClain herself has grown 2 inches since arriving). She trained in both the medium and large suits and wore the large on her spacewalk last week, but ultimately she decided the medium fit better. Of the two medium sized spacesuits on the ISS, only one of them is ready for flight, and Koch needs it. It's very important that spacesuits fit correctly; spacewalks are exhausting activities that go on for hours, and a misfitting spacesuit can be detrimental and dangerous. The spacewalk will still go on as scheduled, but Nick Hague will take her place. Not to worry though - 12 of NASA's 38 active astronauts are women; it's only a matter of time before an all-female spacewalk happens!

Today I learned

No, this isn't about a battle between two large birds. Given the recent spacewalk news, I figured it'd be useful to talk about the two operational spacesuits on the ISS, the American Extravehicular Mobility Unit (EMU) and the Russian Orlan (which means sea eagle)

The best comparison I can find is from this Quora page, but I'll summarize here. Both suits are functionally similar, but one interesting difference is how they're worn: the EMU is modular, with the torso, legs, arms, and helmet all attached as separate pieces (usually with the help of another astronaut), while the Orlan is entered in one piece from the back. This difference is what allows the EMU to come in more sizes (although clearly not enough, based on the above!). And in case you were wondering, yes, the spacesuits are very expensive. The unit cost of an EMU is reportedly $12 million! (I'm not sure about the Orlan)

Both spacesuit designs are actually quite old, dating back to the late 70s and early 80s. NASA is working on a next generation of spacesuits with SpaceX and Boeing. 

This week in space history

On March 27, 1969, Mariner 7 was launched from Cape Canaveral on a trajectory to Mars, following its sister probe Mariner 6 (launched one month prior) on the first dual mission to Mars. The probes performed flybys over the equator and polar regions, scanning the Martian surface in unison.

The interesting story here is that 10 days before the scheduled launch of Mariner 6, a faulty switch opened the pressurized helium valves of the Atlas rocket's first stage, causing the rocket to crumple over. However, two pad technicians (Bill McClure and Jack Beverlin) quickly activated a manual override to close the valves, at the risk of being crushed under the 12 story rocket. Their heroic efforts saved the Mariner 6 probe (although a new booster stage had to be used), and NASA awarded them an Exceptional Medal of Bravery for their actions. In 2014, a recently discovered escarpment on Mars was named the McClure-Beverlin Ridge in their honor