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Supposing that washing dishes and sterilizing medical equipment could be expensive to do in space, would a viable option be to expose dishes, scalpels, silverwear etc to the vacuum of space? Would the combination of "vacuum" and radiation from the sun be enough to kill enough of the bacteria and other things? If not for medical equipment, perhaps enough for eating utensils? I know we don't really use those right now, but theoretically speaking could it be done?

I found this answer about micro-organisms tested in space, but I don't know if those are common or dangerous to our health.

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    $\begingroup$ Putting the stuff outside would not be enough. It might kill any bacteria, but wouldn't get rid of the debris (food particles on utensils, blood and gore on surgical instruments). So you can't avoid washing the stuff first. $\endgroup$ – Hobbes May 20 '18 at 19:07
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    $\begingroup$ In zero gravity you could not eat from dishes as used on Earth. If no dishes are used there is nothing to wash. Exposing to space would not remove the rest of food left on the dishes, it would only dry them. $\endgroup$ – Uwe May 20 '18 at 20:19
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    $\begingroup$ @Hobbes Interesting. Even if you sterilize the debris (eg, in an autoclave), as the blood/food heated up it would attract new bacteria and viruses that are already in the air. Assuming the process of sterilization didn't effectively destroy the food itself. $\endgroup$ – barrycarter May 20 '18 at 21:00
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    $\begingroup$ until the tardigrades get into the flux capacitors $\endgroup$ – uhoh Mar 24 at 6:20
  • $\begingroup$ There's a possibility that this experiment has alreay been tried: en.wikipedia.org/wiki/… $\endgroup$ – Dave Gremlin Mar 24 at 10:43
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Can the vacuum of space be used to sterilize equipment?

Supposing that washing dishes and sterilizing medical equipment could be expensive to do in space, would a viable option be to expose dishes, scalpels, silverwear etc to the vacuum of space? Would the combination of "vacuum" and radiation from the sun be enough to kill enough of the bacteria and other things? If not for medical equipment, perhaps enough for eating utensils?

No.

Simple washing and sterilization (almost always?) starts with a physical process to remove dirt and reduce the bioload. Anything caked-on protects anything underneath, in most cases.

Space is full of porous dust, it could be poisonous, radioactive, or even contain biomaterial. Cleaning and then exposing to unknown dust goes against the principles of cleaning.

In most cases heat is a necessary part of sterilization, though there are exceptions. Methods utilizing heat, such as the majority of loads sterilized in the laboratory setting, involves sterilization at 121.1°C/250°F for 30-90 minutes.

If your load contains items that are sensitive to heat the default cycle temperature of 121.1°C/250°F may be too hot and you might need to consider a lower temperature. Using lower sterilization temperatures will result in longer sterilization times. This can be calculated by using the F0 relationship: $Fo = time * 10^{(\text{Temp_Celcius} \, - \, 121.1)/10}$.

Operation of an airlock involves some costs: maintenance, risk, electricity, loss of a bit of oxygen, time. You'll need to use the airlock twice as often to put objects outside and retrieve them as opposed to simple ejection.

Sterilization for each type of object has what is called "cycle development", a procedure designed to reproduce a desired result, to clean to a specified level. See: "How to Validate an Autoclave: Sterilization Cycle Development". There is a recipe that must be followed, simply doing what amounts to 'hanging everything out on the clothesline' is a random method that would provide random results; better to simply dispose of things in most cases.

No doubt there are specific cases where sticking stuff outside would work, using search tools turns up nothing supporting the idea. NASA doesn't do it. Afterwards you would need to clean off the radioactive dust in a sterile manner. It's probably cheaper to litter and let it burn up in the atmosphere.

On a base (on the moon or a planet) cleaning and reuse becomes more cost effective. Cleaning with gravity is different than without. Similarly utensils and dishes are not usable in zero gravity.

Currently NASA is investigating using 'heating trash compactors' that make disks out of the trash which will be tested as additional radiation shielding.

See also:

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  • $\begingroup$ Not that it changes the final answer, but you can solve the "open the airlock twice as often" bit by rotating old objects out and "sterilized" objects back in in the same motion. Still an airlock operation, though. $\endgroup$ – Cort Ammon - Reinstate Monica Mar 28 at 18:37
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    $\begingroup$ I wouldn't say "space is full of porous dust". According to the linked Wikipedia page, there is only one dust particle in a (100 m) by (100 m) by (100 m) cube: space is mostly empty. It's unlikely that something exposed to vacuum for a short time will pick up a significant amount of dust. $\endgroup$ – WaterMolecule Mar 28 at 18:39
  • $\begingroup$ @Both Rereading the sentence and using context and what is being compared, the subject, is necessary and the way things work. You can't use a word or phrase in isolation as the basis for an argument without an understanding of context. $\endgroup$ – Rob Mar 29 at 12:14
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There's an interesting article on phys.org, today, about the BIOMEX experiment on the ISS.

The tests involved samples of different organisms such as bacteria, algae, lichens and fungi being exposed to vacuum, intense ultraviolet radiation and extreme temperature variations on the exterior of the ISS for a total of 533 days. Astrobiologist Jean-Pierre Paul de Vera from the DLR Institute of Planetary Research in Berlin-Adlershof, the person responsible for the scientific management of BIOMEX, was impressed. "Some of the organisms and biomolecules showed tremendous resistance to radiation in outer space and actually returned to Earth as 'survivors' from space,"

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    $\begingroup$ Why, oh why would you bring that stuff back to Earth? Hasn't anyone seen Andromeda Strain? $\endgroup$ – ShadoCat Mar 28 at 21:52
  • $\begingroup$ So thats a negative, then $\endgroup$ – Premier Bromanov Mar 29 at 0:31

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