Space debris impacts on the X-37B

Roamy here.  XBradTC shared this article with me, which, in turn, points to this Defense News article.  Money quote is

The only physical damage seen so far has been seven areas where space debris collided with the aircraft. It also blew out a tire upon landing.

My gut feeling on this is that the seven impact areas are of the type easily seen with the naked eye.  It’s hard to guess how many impacts are probably on the X-37B, not knowing what the orbit(s) was, but after 244 days in space, there should be dozens of very small impacts on the millimeter scale.  Some of these would be hard to see without a microscope, others would be hard to see in the tile material used for thermal protection.

Nick Johnson, the space debris expert at JSC said here that the Hubble Space Telescope gets around 5 impacts per square meter per year, and that was back when the space debris levels were less than half of what they are today.  The original solar arrays for Hubble had 3,600 impacts after 3 years in space.  The Long Duration Exposure Facility (LDEF), which flew in a lower orbit than Hubble, had 34,000 impacts after 5.7 years in space.

Every one of those black dots on that 3′ x 4′ rectangular silver/Teflon blanket is an impact, and there’s about 300 of them.  You might say, Roamy, what’s the big deal?  Those are little!  You’d be right in that those aren’t going to cause major structural damage, but that one in the upper right was nasty, and they do add up.  Remember, this was flying at a time when the Space Shuttle was grounded after the Challenger accident and the orbital debris environment was much less severe than it is now.  Think about an astronaut that could get hit, a window that could crack (the International Space Station has triple-pane windows for that reason, and the Cupola has window covers), a telescope mirror, a reconnaissance sensor, a CCD camera.  This is a photo of the hole made in the composite high-gain antenna on Hubble.

That’s about three-quarters of an inch in diameter, in a quarter-inch thick honeycomb composite.  Not the same as a car-door ding in the parking lot.

2 thoughts on “Space debris impacts on the X-37B”

  1. I’m sure there is plenty of junk we have left in orbit, but I doubt what you are seeing is just from debris left from out activities. Our leavings should not have the relative velocities needed to produce that kind of damage.

    There is stuff coming from deeper in space that would have the kind of energy needed to produce that kind off damage. Frankly, it calls into question the future of long term space travel without some form of energy shield that would act as Start Trek’s navigational shields do.

  2. Quartermaster, they find aluminum, chromium, copper, and titanium dioxide (paint pigment) in impact residues much more often than meteoroid elements like iron or nickel. If it were all coming from deep space, a gravity-gradient stabilized spacecraft like LDEF would have been uniformly peppered on every side except the end pointed towards Earth. Instead, the number of impacts on the leading edge (facing the velocity vector) was ten times that on the trailing edge.
    As for relative velocities, anything in low Earth orbit is traveling ~8 km/sec anyway, and it’s not all in the same inclination, apogee, and perigee.

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