The Atacama Large Millimeter Array or ALMA is a radio telescope complex where signals from dozens of distributed dishes are routed to a single computer which performs interferometry and image processing computationally.

At about 5 kilometers altitude they are not in space yet, but traditional spinning magnetic hard drives were not used due to the altitude and solid state drives were selected.

The Event Horizon Telescope is a cardboard box flown around the world collecting stacks of hard drives, and okay, an array of radio telescopes, some at very high altitude. This comment links to the Western Digital post What Does Helium Have to Do with the Black Hole Image? where I see that special helium filled and sealed hard drives were used so that they would work reliably at the high altitudes of some of the observatories in the network.

Question: Have traditional spinning hard drives ever been used in space outside of pressurized crewed areas? Ever beyond LEO? I'm excluding things like laptops and other computers used in the pressurized crewed areas of space stations, and would like to focus instead on any use of a spinning disk of magnetic material addressed by a read-write head in any other type of location.

We know that spacecraft including the Voyagers had magnetic tape recorders, and early weather satellites had magnetic video tape recorders, but have spinning hard (or floppy for that matter!) disks of magnetic materials been used outside of pressurized crewed areas?

Digital tape recorder (DTR):

Video recorder:

For fun:

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    $\begingroup$ The ISS's distributed computing architecture has computers outside the pressurized hull called EXT MDMs. Some of the MDMs had hard drives early on, since replaced by SSDs, but it's not clear to me if the EXT MDMs did. $\endgroup$ – Organic Marble Nov 4 '20 at 1:15
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    $\begingroup$ @OrganicMarble those would definitely count! I've fined tuned the exclusion zone wording to "pressurized crewed areas". $\endgroup$ – uhoh Nov 4 '20 at 1:33
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    $\begingroup$ As far as I know these are the only HDDs that have ever been in space (excluding crewed areas), but not beyond LEO.digitalcommons.usu.edu/cgi/… $\endgroup$ – Roger Wood Nov 4 '20 at 2:22
  • $\begingroup$ @RogerWood Space SE is welcoming to multiple answers to a question as long as they are sourced and have relevance. You have both! Would you consider adding an answer with your link a short summary of its salient points (since links decay over time)? Thanks! $\endgroup$ – uhoh Nov 4 '20 at 2:38
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    $\begingroup$ While solid state solutions were preferred in space applications long before they were widespread in personal computers, I'm reasonably sure I've read about satellites housing computer systems including hard drives in a helium-filled pressure vessel. The obvious search terms give unusually terrible signal/noise ratios, though. $\endgroup$ – Christopher James Huff Nov 4 '20 at 4:05

As far as I know, the only HDDs that have ever been used in space (excluding crewed areas) are a pair of Conner Peripherals CP3540 500 MB HDDs on the MSTI-3 mission launched in May 1996. The mission lasted 18 months but did not go beyond low earth orbit. The two drives were mounted in a hermetically sealed enclosure. They were mounted back-to-back to avoid torque on the spacecraft during drive startup. There are a couple of very comprehensive reports from Scott Bussinger on the storage unit, one from 1993 before the mission and one from 1998 after the mission.

This slide is from a presentation at the AVS conference a couple of years ago:enter image description here


Conventional hard drives cannot be used in the absence of air (or at high altitudes where the air is thin). They rely on a moving layer of air at the surface of the disk that allows the heads to 'fly' quite close to the surface. There are newer drives that are filled with helium and are hermetically sealed, so these can function at altitudes that conventional hard drives cannot tolerate. As an example, Seagate says:

In general, most Seagate and Maxtor-brand drives are designed to work under the following specifications: Operating altitude (max): 3,048 meters (10,000 feet) Nonoperating altitude (max): 12,192 meters (40,000 feet)

A Dell support knowledgebase entry states something similar.

So, to answer your question in the general, no. Because they can not function at altitude or in (even higher altitude) space

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    $\begingroup$ Question asks "Have...ever...?" In this case "In general, no." only explains why occasional uses are so interesting to ask about. It doesn't answer the question as asked. Maybe you can adjust the wording saying that this is background information explaining why if they were used, it would be a rarity and a challenge? There are already comments referring to instances of use under the question, so "It doesn't happen" can not be a right answer. $\endgroup$ – uhoh Nov 4 '20 at 3:04
  • $\begingroup$ I meant that I haven't done an exhaustive search, but based on the general principal that hard drives operate under it would be impossible. The instances referred to would have had to have drives in 'conditioned' pressurized enclosures. I'll try to find some discussion on the subject... $\endgroup$ – BobT Nov 4 '20 at 3:07
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    $\begingroup$ Yes, and drives with sealed and pressurized enclosures have already been mentioned in those comments and in links in my question! So I don't think you've posted a correct Stack Exchange answer to the question as asked. "I don't think so but I'll have to do some research" is a comment, but not an answer. $\endgroup$ – uhoh Nov 4 '20 at 3:13

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