Real question… how do you “ground” electrical in a space craft? There’s no earth. Large capacitors or something? Or do you just have to live with a floating ground (literally)?
The latter, much the same as the "ground" in an automobile or airplane (or even just any old battery-operated device).
"Ground" is an arbitrarily-chosen voltage convention. In space the floating ground won't cause a fault because there's never an electrical circuit with both the floating ground and the 'real' ground.
Indeed cars, airplanes, boats, all have “grounds” that are not “earthed” in any way.
Fun tidbit, old English cars (and the original Ford Model A!) used to tie positive DC to the frame rail as a “ground” or “common” instead of the negative DC. They are referred to as positive ground cars (and tractors!)
Which modern cars, for example? As far as I know the era of positive ground vehicles ended roughly during the fifties, and very much by the sixties at the latest.
Airplanes do have static wicks [0] which could be seen as a form of local ground. I love these as an example of the adjacent engineering challenges that arise.
Busses also (used to?) have ground straps that you may see dragging. Apparently this was somewhat common on cars as well. "bus ground strap" is unsurprisingly difficult to search for, but I did find a discussion on Quora [1] that claims rubber formulations were responsible for vehicles picking up a static charge.
All of this is interesting once seen as an attempt to remove the potential difference between local "ground" and ambient environment.
Apparently you attach all grounds to some common component, like the chassis and then you have a zero volt reference. As long as it is stable and the relative voltages to it are consistent, that should suffice for electrical systems. Handling overall charge of the craft might be a bigger challenge, but no idea how that would be handled.
Protective actions are required by the docking standard so it’s taken care of at docking but I find it very hard to find detailed information about implementations. It’s either very niche or considered sensitive enough to not be published widely.
I guess they use the same solution than during EVA which is running the Plasma Contactor Units to dissipate any buildup.
The docking spacecraft must follow a NASA standard[1] to avoid building up electrostatic charge.
From the Commercial Crew requirements document[2]:
3.9.3.13 Integrated Space Vehicle Electrostatic Charge Control
3.9.3.13.1 LEO Charging Design Standard
The spacecraft shall meet the intent of the requirements contained in NASA-STD-4005, Low
Earth Orbit Spacecraft Charging Design Standard. [R.CTS.285]
How the contractors achieve that might be proprietary. It looks like (at one time) SpaceX used electrically conductive paint[3] as part of their mitigations.
You missed this one: "International Docking System Standard
(IDSS)" [0] which I actually read that before answering hence my "required by the docking standard".
You will see that it says: "IDSS compliant mechanisms protect against electrostatic discharge through the soft capture system" which is to say not much.
That’s still more than the previous standard for which the paragraph on ESD just says "RESERVED".
TL;DR they dissipate charge using three Plasma Contactor Units (PCUs) on the Z1 truss, and measure it using the Floating Potential Measurement Unit (FPMU) on the S1 truss. This clamps the ISS to within 20 volts of the local plasma.
At least it's not there's no Earth. I think we've seen that movie where Earth disappears from the space station.
I would assume everything on ISS and capsules are running DC. Does DC need a ground? Every electronic circuit I've built just uses ground as the common leg to battery or power.
Fun fact: it's very difficult to get rid of built-up charge in space. And guess what incident EM radiation does to your electronics: that's right, it can build up charge! To my understanding, this is especially a problem when charge is built up in specific dielectrics/insulators or the very delicate structures of modern transistors and other semiconductor devices. This so-called "total ionizing dose" [1] can lead to "leakage currents, degrade the gain of a device, affect timing characteristics, and, in some cases, result in complete functional failure" [2].
Any RF or EMC engineer will tell you that ground is a dirty word, especially in extreme conditions. There's no one-size-fits-all approach, since so much depends on the physical context.
Thats no loonger the standard since many have done that by now. The standard is now manned cost to orbit. The race to the bottom in cost to orbit will inspire the next round of awe inducing spin off whose race to the bottom will then do the same for the next round... we are capturing the ripplesin the pond of capability improvement right now that has been held up for fifty years by space trvel being stuck in the realm of government (computing advancements held us back too so maybe only the last twenty years is attributable to the gocernment).
Getting things into orbit is table stakes. Boeing needed to prove that they could build a reliable crew vehicle on a reasonable budget, and by that measure they have failed.
The point of Starliner is not simply to get a manned crew to space, it is to implement a reusable ship. People forget that Starliner lands in the desert and is reusable.
That is a far more complicated job than sending a manned crew to space, which is, as other have indicated, table stakes at this point. Coming down safely and going back up with the same hardware is the required part of Starliner that massively failed.
There was a report from China's first manned mission of a sound like "knocking an iron bucket with a wooden hammer", which was eventually determined to be air pressure changes[0].
But the fact that this sound is coming through the speaker, and the way it restarts around 1:10 (unless that's just a comms hiccup), makes this seem like some kind of electronics issue. Sounds a bit like an alarm/warning, even.
That's funny. The astronauts call first line tech support, and get a useless answer while the problem is passed to a higher level of tech support.
The astronaut on the line didn't get a support ticket number, though.
That very much sounds like those aliens from that book by Carl Sagan made into a movie starring Jodie Foster, "Contact". In the book and movie they needed the VLA radio telescope to pick up the signal but modern technology has made it possible for an enlarged Apollo clone to receive it on the entertainment system.
If you don't understand it just watch the movie and listen to the signal picked up from the region around the star Vega, then you will understand.
> NASA issued the following explanation on Monday for the strange noises: "A pulsing sound from a speaker in Boeing’s Starliner spacecraft heard by NASA astronaut Butch Wilmore aboard the International Space Station has stopped. The feedback from the speaker was the result of an audio configuration between the space station and Starliner. The space station audio system is complex, allowing multiple spacecraft and modules to be interconnected, and it is common to experience noise and feedback."
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[ 4.4 ms ] story [ 162 ms ] threadEdit: I somehow wrote SpaceX even though I knew Starliner is made by Boeing. The news related to X being blocked in Brazil confused me probably…
"Ground" is an arbitrarily-chosen voltage convention. In space the floating ground won't cause a fault because there's never an electrical circuit with both the floating ground and the 'real' ground.
EDIT: turns out the ISS is a bit more complicated than that, and it also has a "grounding strap" that connects to the local plasma. https://news.ycombinator.com/item?id=41417136
Fun tidbit, old English cars (and the original Ford Model A!) used to tie positive DC to the frame rail as a “ground” or “common” instead of the negative DC. They are referred to as positive ground cars (and tractors!)
https://www.restore-an-old-car.com/positive-ground-cars.html
Busses also (used to?) have ground straps that you may see dragging. Apparently this was somewhat common on cars as well. "bus ground strap" is unsurprisingly difficult to search for, but I did find a discussion on Quora [1] that claims rubber formulations were responsible for vehicles picking up a static charge.
All of this is interesting once seen as an attempt to remove the potential difference between local "ground" and ambient environment.
[0] https://en.wikipedia.org/wiki/Static_wick
[1] https://www.quora.com/Cars-used-to-have-grounding-straps-han...
https://s3vi.ndc.nasa.gov/ssri-kb/static/resources/NASA-HDBK...
Apparently you attach all grounds to some common component, like the chassis and then you have a zero volt reference. As long as it is stable and the relative voltages to it are consistent, that should suffice for electrical systems. Handling overall charge of the craft might be a bigger challenge, but no idea how that would be handled.
I guess they use the same solution than during EVA which is running the Plasma Contactor Units to dissipate any buildup.
From the Commercial Crew requirements document[2]:
How the contractors achieve that might be proprietary. It looks like (at one time) SpaceX used electrically conductive paint[3] as part of their mitigations.[1] https://standards.nasa.gov/standard/NASA/NASA-STD-4005
[2] https://ntrs.nasa.gov/api/citations/20150010757/downloads/20...
[3] https://phys.org/news/2013-03-white-coating-spacex-dragon-tr...
You will see that it says: "IDSS compliant mechanisms protect against electrostatic discharge through the soft capture system" which is to say not much.
That’s still more than the previous standard for which the paragraph on ESD just says "RESERVED".
[0] https://ntrs.nasa.gov/api/citations/20170001546/downloads/20...
https://ntrs.nasa.gov/api/citations/20110014828/downloads/20...
TL;DR they dissipate charge using three Plasma Contactor Units (PCUs) on the Z1 truss, and measure it using the Floating Potential Measurement Unit (FPMU) on the S1 truss. This clamps the ISS to within 20 volts of the local plasma.
https://en.wikipedia.org/wiki/Plasma_contactor
https://web.archive.org/web/20060929171819/http://space-powe...
https://www.nasa.gov/image-article/floating-potential-measur...
I would assume everything on ISS and capsules are running DC. Does DC need a ground? Every electronic circuit I've built just uses ground as the common leg to battery or power.
Any RF or EMC engineer will tell you that ground is a dirty word, especially in extreme conditions. There's no one-size-fits-all approach, since so much depends on the physical context.
[1] https://radhome.gsfc.nasa.gov/radhome/tid.htm
[2] https://www.analog.com/en/signals/thought-leadership/challen...
SpaceX has nothing to do with it
https://www.boeing.com/space/starliner
Them astronauts have nerves of steel.
(Wooden hammer on a steel bucket!)
Yet
That is a far more complicated job than sending a manned crew to space, which is, as other have indicated, table stakes at this point. Coming down safely and going back up with the same hardware is the required part of Starliner that massively failed.
Watch the crew entering ISS. Williams is very, very, very happy to have survived the ascent. <https://www.youtube.com/watch?v=zsURePrNTx0>
The last two decades of progress has come almost exclusively from “new space”.
Not for lack of trying
But the fact that this sound is coming through the speaker, and the way it restarts around 1:10 (unless that's just a comms hiccup), makes this seem like some kind of electronics issue. Sounds a bit like an alarm/warning, even.
[0]: https://usa.chinadaily.com.cn/china/2016-12/02/content_27545...
Think about the fullness of the waveform to make a sonar ping like that (like in a synth or something). Really weird!
My bet is that the new wiring wasn’t properly RF shielded.
https://www.youtube.com/watch?v=PIKDRS5K2uo
https://news.ycombinator.com/item?id=32958319
has this been solved?
If you don't understand it just watch the movie and listen to the signal picked up from the region around the star Vega, then you will understand.
> NASA issued the following explanation on Monday for the strange noises: "A pulsing sound from a speaker in Boeing’s Starliner spacecraft heard by NASA astronaut Butch Wilmore aboard the International Space Station has stopped. The feedback from the speaker was the result of an audio configuration between the space station and Starliner. The space station audio system is complex, allowing multiple spacecraft and modules to be interconnected, and it is common to experience noise and feedback."