Sciency Words: Safety Ellipse

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those wild and crazy words scientists use.  Today’s Sciency Word is:


I don’t know about you, but when I’m trying to dock my shuttle pod with another spaceship, I like to take a few long, leisurely loops around that other spaceship first.  You know, like this:

Spaceships are pretty!  Who wouldn’t want to get a good look at them from every conceivable angle before completing docking maneuvers?  But it turns out that circling round and round a spaceship like this is not just for admiring the view.  It’s also for safety!  As explained in this paper:

A “safety ellipse” is an out-of-plane elliptical periodic relative motion trajectory around the primary spacecraft such that the trajectory never crosses the velocity of the primary.

That clear things up?  No?  Okay, how about a quote from this paper instead:

This paper defines a safe trajectory as an approach path that guarantees collision avoidance in the presence of a class of anomalous system behaviors.

Still confused?  Here’s a short video demonstrating what a safety ellipse (a.k.a. a safe trajectory) looks like:

Basically, if your shuttle pod experiences engine failure or any other major malfunction, flying in a safety ellipse ensures that you will not collide with the ship you were trying to dock with.  At least not for a good, long while.

I first heard about this term the other day while watching the livestream of the SpaceX Dragon capsule approaching and docking with the International Space Station.  Several times, the livestream commentators mentioned that Dragon was utilizing a “24 hour safety ellipse” or “24 hour safe trajectory,” meaning that if anything went wrong, mission control would have at least 24 hours to fix it before Dragon and the I.S.S. collided.

So remember, friends: the next time you’re going to dock with another spacecraft, do that out-of-plane elliptical periodic relative motion thing.  In other words, circle around the other ship a few times before making your final approach to dock.  It’s for safety reasons.

P.S.: It’s also for enjoying the view.  Spaceships are pretty!

NASA’s Next Launch System: the Trampoline

Let’s say you don’t own a car, so you carpool to work.  You have a nice arrangement with a friend: he drives, you pitch in for gas, and everybody’s happy.  Then you and your friend get into a fight, and all of a sudden you can’t get a ride to work.  This is now the situation between the United States and Russia after our dispute over Ukraine.  The Russians are no longer willing to give American astronauts rides to the International Space Station.

Image courtesy of NASA
Image courtesy of NASA

Now I don’t write a blog about politics, and I don’t want to go into a discussion about the Ukrainian situation.  It sounds to me like there are good guys and bad guys on both sides, and the whole thing is a complicated mess.  But now this mess is affecting the one issue that I and my blog care about most: space.

The plan was that, following the termination of the space shuttle program, private companies like SpaceX or Virgin Galactic would pick up the slack.  After my initial skepticism, I came to see this as a good thing if only because it meant American space exploration would no longer be totally beholden to the whims of Congress.  But those private space companies aren’t ready yet.  They need at least a few more years before they can start launching astronauts into space.

One Russian official suggested that, in the meantime, NASA could try using trampolines to send its astronauts into space.  We can only hope this quarrel with Russia will provide the impetus private space companies need to prevent further delays and get their fleets into orbit.  Otherwise, the future of the International Space Station is in jeopardy.

Three Reasons NOT to be an Astronaut

Regular readers of my blog know how desperately I want to live on the Moon or Mars or at least get to go to space once in my lifetime.  It might even be fun to have a career in space exploration, but there are some things about being an astronaut that sound… less than dignified.  Here are a few reason not to be an astronaut.

  • No shower.  For decades, NASA and other space agencies have struggled to figure out how to build a shower that works in space.  In zero gravity, water likes to form big, liquid globs that drift aimlessly around the room.  Skylab had a shower of sorts, as did Russia’s Mir space station, but the current International Space Station has no shower, mainly because every drop of water on the ISS has to be strictly rationed.  The best astronauts can hope for is a kind of sponge bath using a washcloth and a tiny bag of soapy water.
  • No laundry.  This is similar to the no shower problem.  Water just doesn’t cooperate, and there isn’t enough of it anyway.  Most astronauts have to wear the same clothes and the same underwear for days on end.  All their dirty laundry is then dumped into space with the rest of the garbage (and incinerates when it hits the planet’s atmosphere), and fresh clothing is sent up from Earth.
  • The toilet.  I was once told astronauts have to wear diapers because there’s no toilet in space.  Fortunately, this isn’t true, but the toilet on the International Space Station is not what I’d call ideal, and apparently “mistakes” have been made.  Just watch the video.

All that being said, every great explorer has had to make some sacrifices and endure certain hardships.  I’m sure many suffered far worse things than dirty laundry and no working shower.  If I’m ever given the opportunity, I’d still go to space.  I think I’d rather be a space tourist than an actual astronaut, though.  To those astronauts who are not only boldly going where no one’s gone before but are bravely sacrificing many of the creature comforts we Earthlings take for granted… I salute you.

SpaceX Boldly Goes Where No Private Company Has Gone Before

Last week, SpaceX successfully launched its Dragon Capsule and docked it at the International Space Station.  They are the first private company to ever send a spacecraft to the ISS.  It’s a historic moment, a definite cause for celebration.  This marks the beginning of a new era of corporate space exploration.  But is the corporate take over of space a good thing?

Space exploration should be motivated by our sense of wonder.  We should do this not because of greed but because we want to learn more about the universe we live in, want to see it and experience it in all its beauty.  As humanity spreads across the stars, I hope we retain the romantic ideals espoused by science fiction like Star Trek.

Elon Musk, the CEO and Chief Designer at SpaceX, reportedly wants his company to someday take people to Mars and other planets in the Solar System.  I’d love nothing more than to see him succeed.  But I remember a science fiction movie where the first spaceship to land on Mars was plastered with ads like something out of NASCAR.  American commercialism has a way of cheapening things, and I worry about that.

Money is what makes our society work.  Maybe by turning space exploration over to the private sector, we can return to the Moon, go to Mars, and eventually leave our Solar System a little sooner.  After all, Congress has cut NASA’s budget so much they can’t even afford their own Space Shuttle.  If NASA can’t do this, someone else has to take their place.

What do you think?  Are you glad the private sector is taking over space exploration?

Baby Steps

With all of NASA’s budget cuts, it’s easy to lose sight of the big picture when it comes to space exploration.  Right now, we hear nothing but bad news.  But we have to remember the International Space Station is still up in the sky, astronomers are still finding lots of new planets, and private companies are very close to taking over where NASA left off.

At a conference for the advancement of science, Canadian Astronaut Chris Hadfield said humanity will look back on the 21st Century as a series of baby steps into space.  Yes, we’ll fall down a lot and get a few bruises, but we’re still learning, and we have to take those baby steps before we can go a lot further.

Diagram showing which countries contributed which parts to the International Space Station. Click picture to enlarge.

Hadfield is scheduled to go to the International Space Station in December.  During his time aboard the ISS, he says he will be trying to solve basic problems about human space travel, like blood chemistry, nutrition, and waste.  Astronauts aboard the ISS are working on approximately 100 different experiments to make it safer and easier for humans in the future to travel beyond Earth orbit.

For about two months, Hadfield will be in command of the space station.  He will be the first Canadian to have that honor.

For the original article on Chris Hadfield’s statements, click here.

Why Newt Gingrich’s Moon Base Matters

Newt Gingrich has been widely ridiculed by both the media and his fellow Republicans for wanting to return to the Moon and establish a lunar colony by 2020.  What hasn’t been discussed is that the Moon and the rest of the Solar System are packed full of untapped natural resources.  The Moon in particular has plentiful helium-3, which could be used as a carbon-free, radiation free fuel source.

Moon Base Alpha as seen in Space: 1999.

In the last decade, the Chinese government has engaged in an aggressive space program.  They’ve sent men into space, done spacewalks, and are now building their own space station to compete with the International Space Station (ISS).  At the rate they’re going, experts believe China could establish a permanent presence on the Moon as early as 2022 and claim it as their territory.

A new space race is on, whether the American public knows it or not, and I for one do not want China to call dibs on the Moon’s helium-3.  We should take Gingrich’s proposal seriously, not mock him (at least not for this).

The good news, especially for anyone who doesn’t want to vote for Gingrich, is that his proposal is not the only one.  According to a report from, the Russian space agency is talking to NASA and ESA (the European Space Agency) about building a Moon base as a project of international cooperation, just like the ISS.

I’d prefer to see an international Moon base rather than the Americans only one Gingrich proposes so that the Moon’s resources can be shared by all of humanity and not hoarded by one country.  The important thing right now is that we’re talking about it.  The more the public learns about this issue, the more they’ll understand it and the more they will want to see a permanent outpost on the Moon.