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Space Qualified Thread Lock

11/12/2020 8:08 AM

Does anyone know of any space qualified thread locking adhesives? I've asked Henkel about their Loctite products but they say none are space qualified. I'm hoping there are some other manufacturers with something suitable.

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#1

Re: Space Qualified Thread Lock

11/12/2020 9:11 AM

Space agencies, such as the USA's NASA, must surely have gone down this route before, perhaps?

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#2
In reply to #1

Re: Space Qualified Thread Lock

11/12/2020 9:15 AM

Yes, I've been looking in their public technical documents. There's various tests of thread locking adhesives but nothing that says any particular product is approved.

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#3

Re: Space Qualified Thread Lock

11/12/2020 10:37 AM

You might try NASA-STD-8739.1B, Workmanship Standard for Polymeric Application on Electronic Assemblies.

The trouble is that requirements can be different from one program to the next, so it is difficult to specify an adhesive that is "universally approved" for space use.

From Paragraph 4.3.1 Selection and Approval Requirements for Polymeric Materials

"g. Selected to enable the finished assembly to meet all mechanical, thermal, electrical, and optical requirements associated with test and mission use, with consideration given to the following characteristics: dielectric constant, permittivity, dielectric withstanding voltage, tensile modulus over temperature range, coefficient of thermal expansion (CTE), glass transition temperature (Tg), viscosity and transmissivity, and Project-specific requirements."

So in other words, you can use whatever you want as long as it meets all the requirements for your job. And that's also why you received a non-answer from Henkel.

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#4
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Re: Space Qualified Thread Lock

11/12/2020 10:42 AM

Thanks for that. It may be that we will have to choose something & as long as it survives the environmental, thermal, shock and vibration testing, it will be OK.

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#5

Re: Space Qualified Thread Lock

11/12/2020 10:45 AM

You can also refer to NASA Reference Publication 1228, "Fastener Design Manual".

https://ntrs.nasa.gov/citations/19900009424

(for some reason CR4 isn't permitting 'live' links to be pasted into posts)

See Page 9 for a short paragraph on threadlocking adhesives.

Good luck with your quest !!

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#6
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Re: Space Qualified Thread Lock

11/12/2020 10:49 AM

That is a very short paragraph.

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#8
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Re: Space Qualified Thread Lock

11/12/2020 11:04 AM

If outgassing is a concern in your application, you also might want to noodle around in this database:

https://outgassing.nasa.gov/

Cheers !!

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#24
In reply to #5

Re: Space Qualified Thread Lock

11/13/2020 12:12 PM

That thirty year old NASA article only briefly identifies epoxy based chemical thread lockers. Many of today's thread locks (the two identified in the posted more recent NASA publication) work by oxygen being the depolymerizing catalyst preventing the plastic from solidifying.

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#7

Re: Space Qualified Thread Lock

11/12/2020 10:56 AM

I suspect you won't find a singular "space" qualified thread lock for the environmental conditions will vary greatly depending on what part of space and how long your machine will operate in space. For instance, a polar orbiting Low Earth Orbit satellite that regularly transitions into and out of the Van Allen belts will experience vastly different radiation levels than a geosynchronous one will. Then there is also the collection of deep space probes with their extreme cold concerns.

A trusted machinist once told me that all thread locks are temporary bonding agents that should not be relied upon in the long run.

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#9

Re: Space Qualified Thread Lock

11/12/2020 2:45 PM

I would stick with a mechanical method of securing connections....

"When the Cassini-Huygens spacecraft entered Saturn’s orbit this summer, it had to be able to handle the vibration, shock, and temperature extremes of a rocket launch. In addition, the Huygens probe has to dive into the atmosphere of Titan, Saturn’s largest moon, to measure atmospheric composition all the way down to the frigid surface. For the Cassini orbiter and Huygens probe to be successful, several hundred bolts must maintain vacuum-tight sealed cavities for the entire seven-year mission, with no thread loosening or stripping.

Madison Heights, Mich.-based Spiralock Corp. had the answer: A new thread form with a 30° “wedge” ramp cut at the root of the female thread. Under clamp load, the crests of the threads on any standard bolt are drawn tightly against the wedge ramp. Thread contact forces are therefore applied at approximately 60° from the bolt axis, rather than 30° as in a standard thread form. The angular relationship between the wedge ramp and the male thread restricts bolt or screw movement. The wedge ramp not only eliminates the transverse motion that causes loosening under vibration but also distributes the loads of the threaded joint throughout the engaged threads.

The wedge ramp lets the fastener spin freely until clamp load is applied. At that point, the crests of the standard male thread form are drawn tightly against the wedge ramp, eliminating radial clearances and creating a continuous spiral line of contact along the entire length of thread engagement. This spreads the clamp force more evenly over all engaged threads, reducing fatigue failure and increasing the integrity of the threaded joint.

For atmospheric measurement of Saturn and Titan on the Cassini-Huygens mission, NASA used the Spiralock internal thread form to resist vibration and temperature-induced thread loosening on mass spectrometer instrumentation.

“To survive the vibration and high temperatures of launch, we needed the most reliable locking engagement thread,” said Dan Harpold, a NASA scientist who worked on the project. “Screws had to remain tight because there is no opportunity for retightening. With conventional threading, however, screws loosened up and backed out under testing.”

Among the tests carried out were a series of about 12 high-temperature “bake outs,” in which screws and their matching internal thread forms were heated from room temperature to 300°C to simulate temperature-induced thread loosening.

“The Spiralock thread form retained a tight seal,” says Harpold. “Once torqued down properly, the screws stayed put in the threads.” "

https://www.stanleyengineeredfastening.com/brands/optia/spiralock

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#14
In reply to #9

Re: Space Qualified Thread Lock

11/13/2020 4:06 AM

That might have been an option if we had considered it early in the project but parts have been made & time constraints prevent re-manufacture.

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#16
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Re: Space Qualified Thread Lock

11/13/2020 4:36 AM
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#17
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Re: Space Qualified Thread Lock

11/13/2020 4:48 AM

These are screws into threaded holes, M2.5 & M3.

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#18
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Re: Space Qualified Thread Lock

11/13/2020 5:24 AM
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#19
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Re: Space Qualified Thread Lock

11/13/2020 5:43 AM

I don't think that would suit this application but searching on the ASTM spec. they refer to found me this which looks like it might work.

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#20
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Re: Space Qualified Thread Lock

11/13/2020 6:12 AM

I don't think so, the temperature range is lacking, it also is likely to be high outgassing, and must also work in a vacuum....It should be certified to work at 4°K(-452°F) to several hundred degrees...

"Satellites and spacecraft must survive and operate in an environment entirely different from that on Earth. There is no atmosphere to protect them from radiation or provide a blanket of warmth. Instead, they must put up with extreme hot and cold temperatures, exotic forms of some common materials and elements, and high vacuum conditions. For some space-bound components, such as propulsion subsystems and certain experimental devices on the International Space Station, they must withstand exposure to cryogenic temperatures as low as 4°K. These factors impose a strict set of constraints on spacecraft equipment and materials."

"It’s worth noting that even within a given family of adhesives, outgassing can vary substantially. For example, the more-flexible epoxies are more prone to outgassing due to their lower cross-link density than their more-rigid counterparts. So adhesives should be evaluated for outgassing individually rather than as families. And the only way to know for certain whether a specific adhesive meets the low outgassing criteria spelled out in ASTM E595 is to test it."

https://www.machinedesign.com/fastening-joining/article/21832856/epoxies-and-adhesives-fit-for-space

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#21
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Re: Space Qualified Thread Lock

11/13/2020 6:29 AM

It will work in the thermal test range specified for our device.

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#10

Re: Space Qualified Thread Lock

11/12/2020 6:26 PM

Full text of " Outgassing Data for Selecting Spacecraft Materials"

At one time, this was the bible. Tests were done at GSFC for us.

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#11
In reply to #10

Re: Space Qualified Thread Lock

11/12/2020 8:00 PM

Could you point out the thread lock? I don't see it....

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#12
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Re: Space Qualified Thread Lock

11/12/2020 9:50 PM

Could you point out the relevance of your "book" on "mechanical fasteners as an answer to, "Does anyone know of any space qualified thread locking adhesives?" I don't see it.

You go first.

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#13
In reply to #12

Re: Space Qualified Thread Lock

11/13/2020 2:32 AM

The point is there aren't any known thread locking adhesives for space(here's where you say there is, if you can)...The thread design used on the Cassini-Huygens mission is proven to work...I think I made that clear enough for most....

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#15
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Re: Space Qualified Thread Lock

11/13/2020 4:07 AM

The formatting seems to have fallen apart in that document.

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#22

Re: Space Qualified Thread Lock

11/13/2020 8:25 AM

Here is a NASA report on the use of Loctite 242 and 271 for the International Space Station. I believe that clearly qualifies these thread locks as being used in space. The lengthy report goes deep into many of the critical details of application technique, thread pattern, vibration loads, temperature, surface materials, etc. that these tests were performed along with their results. Clearly there are space related scenarios where these products can be reliably used and scenarios where they shouldn't be used.

https://ntrs.nasa.gov/api/citations/20110011064/downloads/20110011064.pdf

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#23
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Re: Space Qualified Thread Lock

11/13/2020 8:48 AM

Thanks for that, I'll have a read.

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#25

Re: Space Qualified Thread Lock

11/21/2020 7:14 PM
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