It’s a mess out there

So far this year the ISS has had to move out of the way of debris twice. First on January 13th due to debris from the Iridium/Cosmos collision in 2009, and then again on January 28th due to Fengyun-1C debris. If it seems like this is happening more often, that’s because it is. I haven’t done enough research to confirm that twice in one month is a first, but twice in the first 4 weeks of the year is definitely a first. This is the first time two DAMs (debris avoidance maneuvers) have happened in such a short time. The highest density of DAMs before this year was in 2010 with DAMs in April, July, and October. Two DAMs in the first month of the year is a bit foreboding.

In case you forgot, Fengyun-1C is the satellite that China deliberately blew to smithereens in 2007. That satellite was at a high low earth orbit (yes, high low) above the ISS. That debris has been slowly “falling” back to Earth over the past 4 years (it’s really not falling but just losing orbital energy due to drag). The plot below, from NASA’s orbital debris office, shows just how much debris was added to Earth orbit from the two destructive events (one deliberate and one accidental) in the past few years.

Plot of orbital debris over time

In case you’re confused, it’s the two huge jumps at 2007 and 2009. Find them yet? Yeah, thought so.

At this point, there’s nothing we can do to help reduce this problem for the rest of ISS orbital life. The problem of space debris needs to be dealt with before launch of satellites with sound “cradle-to-grave” mission design as well as strong international policy that is enforced. Right now, there are no such policies, only “voluntary guidelines” created by the UN Committee on the Peaceful Uses of Outer Space. NASA is stuck with the constant close calls as long as we operate the ISS at its current orbit. Fortunately, we have well written Flight Rules and well trained trajectory officers to keep us on the straight and narrow – or threading the needle, if you prefer.

Tech writers love to report on new crazy ideas for orbital debris removal. These ideas include your standard “go grab it and bring it back”, your “ground laser broom”, your “giant space net”, your “inflatable balloon”, your “giant aerogel sticky ball”, and other wacky ideas. Thinking outside the box is good, but none of these would be cheap to implement. Who is going to spend the money on debris cleanup? There is no profit margin there. It would have to be a government funded project, but NASA doesn’t have billions of dollars to spare on a giant space net right now.

This problem has to be solved in international politics as well as in satellite mission design now, in the first half of the 21st century, so that later missions do not become too cumbersome to operate due to constant adjustments of orbital trajectory. The situation is by no means catastrophic, as some of the bee hive style graphics of Earth orbit would imply. But the problem does make it expensive and difficult to operate a mission in low Earth orbit.

A debris hit to the space station is one of the more common scenarios we run in ISS flight controller simulations. This is partly because with a piece of speeding orbital debris the training team can make anything break that they want. Need a specific water pump to fail at the same time as a certain computer? Send some debris on a straight line through both of them! But we also sim those cases so often because they are real and they are serious. We may train those cases to death, but the last thing I want to hear when I am on shift in the control room is that we are in a “rapid depress” emergency. If that day every comes, it will be a bad one.

February 2, 2012 10:25 pm

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