Close Call: Astronauts Evacuate But Space Station Avoids Debris Hit

The three crew members on board the International Space Station were told to “evacuate” into the Soyuz spacecraft earlier today, when they were notified of possible debris hit to the station. However, thankfully, the debris passed by harmlessly. NASA and mission control in Moscow received a “RED threshold late notice conjunction threat alert” Thursday morning, confirming the object, cataloged as “25090 PAM-D” – said to be a piece of a spent satellite rocket motor –, would approach near the station at 16:39 GMT. Mission control radioed to the crew the possibility of impact to the station was low, but the piece of debris was large enough that if it hit the ISS, there would only be a 10 minute reserve time. NASA sources said the debris was estimated to be 0.009 meters (0.35 inches) wide, weighing less than 1 kg, (Update: NASA now says the object was about 5 inches (12.7 cm) and was expected to pass about 4.5 kilometers (2.8 miles) from the station. That is close enough for concern in space.

The crew responded quickly and professionally throughout the close-out procedures. ISS Commander Mike Fincke, US crew member Sandy Magnus and Russian Flight engineer Yury Lonchakov followed pre-prescribed procedures in closing hatches and window shutters before climbing into the Soyuz. The Soyuz hatch, however was left open. If the debris had hit the station, the crew could have quickly shut the Soyuz hatch and flew to Earth.

The three crewmembers currently on board the ISS. Credit: NASA
The three crewmembers currently on board the ISS. Credit: NASA

The object was initially classified as a low threat of collision with the ISS. However, tracking Thursday morning suggested a greater threat. Usually, when debris is seen as on a possible collision course with the ISS, the station is able to fire thrusters and maneuver out of danger. However, because of the late notice, there wasn’t time to perform the thruster maneuvers.

Afterward, Fincke radioed to mission control that they had kept an eye out for debris passing by while they were in the Soyuz, but they didn’t see anything. The crew quickly returned to the station, opening up hatches and other systems they had shut down, resuming their schedule. Magnus calmly said she was going to go running, part of the daily exercise routine astronauts must perform in space to maintain muscle mass and bone density. Events that were previously scheduled during the time of the evacuation procedures are being rescheduled.

See more info on the debris and evacuation procedures at

19 Replies to “Close Call: Astronauts Evacuate But Space Station Avoids Debris Hit”

  1. Picture a 1cm chunk of metal orbiting the earth at the same altitude as the ISS. In order to stay at that orbit, it has to be flying at 17500 mph. Now, if it is traveling in the same orbit as the ISS, there would be no issue, because they would be stationary with respect to each other. But as soon as their respective vectors start to diverge, their speed when they intersect will quickly rise. If they were to meet while traveling in complete opposition to one another, their combined speeds would push the apparent impact velocity to 35000 mph.

    Once you realize that, just picture *anything* 1 cm in size traveling at that speed hitting you. You’d never realize you’d been hit, because you’d be dead, instantly.

  2. Although the wording is factually correct, I expect a 1cm object to be MUCH less than 1 kg!
    A 1cm cube weighing 1 kg would have a density 1000 times that of water, so it’s probably more around 1 g.
    Unless it was a piece of a secret satellite gravity drive including a small black hole!

    More seriously, hasn’t this already happened before?

  3. I wonder what all the consequences are if the ISS got hit.

    If the station would be depressurized very fast through a medium-sized hole then a lot of stuff should be blown through the gap, resulting in a new cascade of space debris outside.

    Maybe the emersion point itself would operate like a nozzle, giving the ISS some thrust and in consequence disturbing the orientation of the whole complex, making the station gyrate or even leave the orbit?

  4. Anything blown outside would tend to be loose personal stuff. Papers, pens/pencils, utensils, etc. And it would tend to stay in much the same orbit as ISS, this isn’t the kind of violent ejection of particles we saw in the collision last month, or from an ASAT explosion.

    The venting could well act as a nozzle, but remember that ISS is a fairly massive object and only one module may depressurize. It might upset solar array and antenna tracking for a time (not a good thing in itself), but it’s not enough for any wild gyrations and definitely not sufficent to de-orbit the complex.

    As for the idea that you might be ‘killed instantly,’ that’s only if your body happened to be in the path of the penetrating debris. Your more likely problem, not unlike flooding compartments on a ship/submarine, is to get out of, and seal off that section before losing consciousness…

    We can take some of the lessons of the Progress/Mir collision as a guide, here.

  5. A few observations:

    1. I didn’t think they could track 1 cm objects and the mass doesn’t match (wait where/when did the update show up). So I guess I was right about that.

    2. It’s clear that different organizations have different tolerance with respect to close calls. Obviously you need to be more diligent with lives directly on the line. If I recall, the Cosmos/Iridium mashup was expected to be a close call at about 600m – far less than this one – and far more massive. I also recall that it was reported that that prediction wasn’t even in the top 10 for the day. Unless these were misreported or my memory is in error then there is a big disconnect in risk tolerance. A gap that shouldn’t be acceptable given that the debris from an unmanned collision could end up being a threat to a manned mission.

  6. … and of course it is still OK if pieces are to be dropped or lost from ISS in the first place!
    What is now coming the No.1 priority for the ISS is literally “Duck and cover” All this story shows is NASA and the other space agencies are all very hypocritical if you ask me.

    Do we REALLY need to have to wait until we see unrecoverable dead cosmonauts or astronauts in orbit before anything is actually done?

  7. Hi all.

    How will NASA and other space agencies solve this space debris problem. Its is becoming a bigger and bigger problem.

    Do they eventually, it time, enter earth’s atmosphere ? Are we producing more space debris that those falling into earth’s atmosphere ?

    I guess this can only get worst !

  8. Don’t know where the 1cm measurement came from…. this has been known to be about 5 inches, with a closing speed at the possible conjunction site of 22,000 relative to the ISS.

  9. Aodhhan Says:
    “…with a closing speed at the possible conjunction site of 22,000 relative to the ISS.”

    is that in km/h?
    If so, those 4.5 km translate into a gap of about two thirds of a second wide… if distances can be measured in seconds…. well, you know what I mean, “space junk seconds”, conceptually similar to “light years” for measuring distances…

    scary thought – no human can see anything that small, travelling at such a speed, coming at them!

  10. Sorry, that is 22,000mph.

    For those wondering why the ISS wasn’t just moved…
    ..not enough time to figure out another orbit. Would be pretty silly to move the ISS half-hazardly to another location which would put it in more danger.

  11. Hi,
    Is there a way to detect those incomming junk from the ISS itself ? Radar, Video survey ? or are they too fast to have time to astronaut be in safety place ?

  12. For 1 kilogram (2.2 pounds) of material moving at 35 400 kilometres per hour (20000 mph), the kinetic energy involved is 4834700 Joules or about 11.5 kilograms of TNT! For comparison, a car weighing 1814 kg (4000 lbs) moving with that same amount of kinetic energy is equal to the car moving at 270 km per hour or 163 miles per hour when it hits something. I.e. A person, let alone the IIS, would be a bit of a mess

  13. Okay, so now we have to come up with a plan for de-orbiting space junk.

    The only thing I can come up with would be to use ground based particle beams to knock objects out of orbit. THAT action would solve one problem but cause another with existing ASAT treaty’s… But given the high cost a possible collision could incur perhaps space fairing nations need to take another look at those agreements?

  14. Imagine if they lock down all the modules, hunker down in the Soyuz, and then the space junk takes out the capsule they’re hiding in.

  15. Countermeasures could be hardened Soyuzes or an armoured bunker attached with the ISS to house the docking ships. The latter would be the world’s first extramundane parking garage.

  16. And also dollhopf i love the way you put things. you are a true soldier to the space community. you brighten me up with your words of wisdom about space:) i love you man

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