Category Archives: Current Events

Earlier in the week, North Korea performed a missile test that successfully put a payload in orbit.  Just one problem: the orbit isn’t exactly stable.  Here’s why it’s bad news:

The most obvious bad news is that this is quite dangerous, as this object has now become a collision risk to other satellites.

The first collision between two satellites happened in 2009, when an American 1,235-pound Iridium communications satellite—launched in 1997—collided with a dead 1-ton Russian satellite launched in 1993. At the time, NASA blamed the Russians.

The collision wasn’t only bad for the functioning Iridium, but also to everyone else. Space is a big place, but it’s full of trash. And like that accident proved, collisions happen.

We can track small pieces of debris, but space crashes generate particles that we can’t monitor. The thousands of objects that may result from such an accident put other satellites, spaceships and the lives of astronauts at risk.

There’s probably several of you wondering how a small piece of space debris can be so deadly, and the answer is a simple one: the speeds involved.  Earth’s escape velocity is 11 km/s, so that’s kind of a minimum speed limit for anything wishing to escape the planet’s gravitational influence.  In practice, satellites will be moving slower than that, since they don’t need to escape Earth’s gravitational influence; they need only to obtain balance between Earth’s gravitational pull and the inertia of the satellite’s motion.

But that’s still fast.  The closer the object is to Earth, the faster it needs to be moving to obtain that balance, since the gravitational influence is stronger.  I spend a bit of time tinkering with NASA’s orbital velocity calculator, and discovered the following:

• The International Space Station, which is maintained at an orbital altitude of between 330 km and 410 km (if Wikipedia is to be believed), has an average orbital velocity of 7.706 km/s.
• Geosynchronous satellites, at an altitude of 35,786 km above the equator, requires an orbital velocity of 3.07 km/s.
• The Moon, which is around 380,000 km away, has an average orbital velocity of 1.022 km/s.

For comparison, a bullet fired from an AK-47 assault rifle has a muzzle velocity of 0.715 km/s.  (Once again, if Wikipedia is to be believed.)  Imagine something the size of a bullet colliding with your spacecraft at 10 times that speed — the consequences of an almost-certain uncontrolled depressurization would not be pretty.

Then, when one considers the North Korean political situation, other concerns pop up:

The other bad news is that, while nobody really knows if this is a satellite or not, all countries are assuming it has been an attempt to disguise the test of a three-stage intercontinental ballistic missile. One that can easily reach the United States or Russia. And it worked.

The only bit of good news is that the lack of precision that probably led to a spinning satellite is proof of North Koreans’ ineptitude when it comes to design and control these long-range weapons. Putting an ICBM in space is not all you need to, say, drop a couple of nuclear warheads over Los Angeles. You need precision guiding systems for that, something that Kim Jong-Un’s boffins don’t seem to have mastered quite yet.

But then again, a nuclear warhead falling anywhere will definitely be very bad news anyway, no matter how precise it is.

While the rest of the world worries about that, I’m more interested in where the satellite will potentially come down after an almost-certain uncontrolled re-entry.  The satellite’s position can be tracked here: rather disturbingly, it passed almost directly over Cape Town as I was typing this post up.

So, lesson of the day — if you’re going to put something in orbit, make sure you do it properly.  Otherwise, you are having a bad problem and you will not go to space today.