4 ms·

Any indication how many of those actuators they can lose and still maintain functionality (i.e., are any of those "spares")?

by jcadam 5y ago

chasil 5y ago
Good question. No idea.
skykooler 5y ago
None of them are spares per se; if any of them fail they will have to use the other four on that segment to point it away from the sensor and disable that segment.
oceanghost 5y ago
3 points in a plane, so maybe half?
- TomVDB 5y ago
  No, they require 7 axes of movement. See the video that somebody else linked to.
- TaylorAlexander 5y ago
  The actuators control the XYZ position and the pitch, yaw, and roll, plus curvature. There is no redundancy.
infogulch 5y ago
The actuator is a genius flexure design that is both mechanically simple and accurate. Breaking Taps 3d-prints a working replica and describes the design. I highly recommend: https://youtu.be/5MxH1sfJLBQ https://youtu.be/5MxH1sfJLBQ The actuator breaking wasn't as concerning after seeing the design.
- mywacaday 5y ago
  Thanks for that video and channel. See what you mean about simple and accurate, strongly agree with the presenter calling it genius. Can't help but feel there is a strong lesson in there for software people.
  - krisoft 5y ago
    > Can't help but feel there is a strong lesson in there for software people. Hmm, can you elaborate on that? What is the strong lesson for software people specifically? Don’t get me wrong it is a beautiful design, and I’m a big fan of flexure designes in general. There is this amazing open source project which uses similar flexure mechanisms for very accurate positioning of microscope samples: https://openflexure.org/ https://openflexure.org/ But I fail to see any obvious takeaways which would generalise to software development. Other than perhaps “Think and work on the same problem for a decade and more and you might find a compact and elegant solution.” Which is nice, when one has that luxury.
    - ChrisMarshallNY 5y ago
      We tend to make complex solutions to simple problems. The thing about any problem, is that "the devil is in the details." It may seem simple, from a high level, but, once we start to "drill down" into the issue, the "rough edges" appear. At that point, we start to break out the baling wire and bubblegum, to kludge our original "graceful" design to meet the facts on the ground. It doesn't just happen for software. Hardware suffers from the same issue, but software makes it easy to start coding before modeling the requirements and context completely. I actually leverage this, in my own work. I call it "Evolutionary Design"[0]. It's not for the faint of heart, because a big part of it is recognizing when I'm rabbitholing, and tossing out what may be weeks of code, wholesale. I'm actually going through that process right now, with the app I'm developing. I'm working on the final feature set. [0] https://littlegreenviper.com/miscellany/evolutionary-design-specification/ https://littlegreenviper.com/miscellany/evolutionary-design-... "There's always an easy solution to every human problem; Neat, plausible and wrong." "The fact that I have no remedy for all the sorrows of the world is no reason for my accepting yours. It simply supports the strong probability that yours is a fake." -- H. L. Mencken “When the map and the terrain disagree; believe the terrain.” -- Swiss Army Maxim
- tkluck 5y ago
  Thank you for the link, that was incredibly interesting. For other people following the link: don't miss out on going into the comment section and finding the original designer of the mechanism complimenting the video and then sharing his own original model - in Legos!
  - usrusr 5y ago
    Slightly exaggerated paraphrase: "You YouTube kids with your fancy 3D printers, here at Ball Aerospace & Technology we didn't need all that, we had Legos"
- binarycoffee 5y ago
  Thanks for the video, flexure-based designs can be so beautiful. It reminded me of a collaboration I had with a small Swiss company that did wonders with electro-discharge machining such as this flexure-based mechanism machined from a single block of aluminium: https://i.imgur.com/PDAVDmJ.jpg https://i.imgur.com/PDAVDmJ.jpg
  - arbitrage 5y ago
    That is gorgeous. Well done.
- jcadam 5y ago
  Very cool. I know nothing about these types of actuators but you're right that they seem pretty robust. When I heard actuators I was thinking of the common types that definitely don't last forever :) Unrelated: reaction wheel assemblies (used for attitude control) typically would have one extra wheel as a "spare." Redundancy is important enough on spacecraft you expect it wherever it is practicable. I used to work in aerospace - spent enough time coding spacecraft simulation tools that I had to develop at least a working familiarity with how some of the common satellite bus systems are supposed to work :)
dtgriscom 5y ago
My guess: any single one of the actuators could fail, and the other actuators could compensate by moving the plane of the mirror(s). The exception would be the curvature actuators. (IANAL, or the appropriate equivalent...)

Any indication how many of those actuators they can lose and still maintain functionality (i.e., are any of those "spares")?

by jcadam 5y ago

Any indication how many of those actuators they can lose and still maintain functionality (i.e., are any of those "spares")?

chasil 5y ago

Good question. No idea.

skykooler 5y ago

None of them are spares per se; if any of them fail they will have to use the other four on that segment to point it away from the sensor and disable that segment.

oceanghost 5y ago

3 points in a plane, so maybe half?

TomVDB 5y ago
No, they require 7 axes of movement. See the video that somebody else linked to.
TaylorAlexander 5y ago
The actuators control the XYZ position and the pitch, yaw, and roll, plus curvature. There is no redundancy.

infogulch 5y ago

The actuator is a genius flexure design that is both mechanically simple and accurate. Breaking Taps 3d-prints a working replica and describes the design. I highly recommend: https://youtu.be/5MxH1sfJLBQ https://youtu.be/5MxH1sfJLBQ The actuator breaking wasn't as concerning after seeing the design.

mywacaday 5y ago
Thanks for that video and channel. See what you mean about simple and accurate, strongly agree with the presenter calling it genius. Can't help but feel there is a strong lesson in there for software people.
- krisoft 5y ago
  > Can't help but feel there is a strong lesson in there for software people. Hmm, can you elaborate on that? What is the strong lesson for software people specifically? Don’t get me wrong it is a beautiful design, and I’m a big fan of flexure designes in general. There is this amazing open source project which uses similar flexure mechanisms for very accurate positioning of microscope samples: https://openflexure.org/ https://openflexure.org/ But I fail to see any obvious takeaways which would generalise to software development. Other than perhaps “Think and work on the same problem for a decade and more and you might find a compact and elegant solution.” Which is nice, when one has that luxury.
  - ChrisMarshallNY 5y ago
    We tend to make complex solutions to simple problems. The thing about any problem, is that "the devil is in the details." It may seem simple, from a high level, but, once we start to "drill down" into the issue, the "rough edges" appear. At that point, we start to break out the baling wire and bubblegum, to kludge our original "graceful" design to meet the facts on the ground. It doesn't just happen for software. Hardware suffers from the same issue, but software makes it easy to start coding before modeling the requirements and context completely. I actually leverage this, in my own work. I call it "Evolutionary Design"[0]. It's not for the faint of heart, because a big part of it is recognizing when I'm rabbitholing, and tossing out what may be weeks of code, wholesale. I'm actually going through that process right now, with the app I'm developing. I'm working on the final feature set. [0] https://littlegreenviper.com/miscellany/evolutionary-design-specification/ https://littlegreenviper.com/miscellany/evolutionary-design-... "There's always an easy solution to every human problem; Neat, plausible and wrong." "The fact that I have no remedy for all the sorrows of the world is no reason for my accepting yours. It simply supports the strong probability that yours is a fake." -- H. L. Mencken “When the map and the terrain disagree; believe the terrain.” -- Swiss Army Maxim
tkluck 5y ago
Thank you for the link, that was incredibly interesting. For other people following the link: don't miss out on going into the comment section and finding the original designer of the mechanism complimenting the video and then sharing his own original model - in Legos!
- usrusr 5y ago
  Slightly exaggerated paraphrase: "You YouTube kids with your fancy 3D printers, here at Ball Aerospace & Technology we didn't need all that, we had Legos"
binarycoffee 5y ago
Thanks for the video, flexure-based designs can be so beautiful. It reminded me of a collaboration I had with a small Swiss company that did wonders with electro-discharge machining such as this flexure-based mechanism machined from a single block of aluminium: https://i.imgur.com/PDAVDmJ.jpg https://i.imgur.com/PDAVDmJ.jpg
- arbitrage 5y ago
  That is gorgeous. Well done.
jcadam 5y ago
Very cool. I know nothing about these types of actuators but you're right that they seem pretty robust. When I heard actuators I was thinking of the common types that definitely don't last forever :) Unrelated: reaction wheel assemblies (used for attitude control) typically would have one extra wheel as a "spare." Redundancy is important enough on spacecraft you expect it wherever it is practicable. I used to work in aerospace - spent enough time coding spacecraft simulation tools that I had to develop at least a working familiarity with how some of the common satellite bus systems are supposed to work :)

dtgriscom 5y ago

My guess: any single one of the actuators could fail, and the other actuators could compensate by moving the plane of the mirror(s). The exception would be the curvature actuators. (IANAL, or the appropriate equivalent...)