The Problem with the Next Moon Mission

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Gotta love that “turd” instead of “third” Irish accent.

Transcript (YouTube will generate one if you ask nicely):

0:48
In 1968, astronauts on NASA’s Apollo 8 mission saw something that should have been impossible.
0:54
In the last moments before the lunar sunrise and sunset every day, they noticed a haze
1:00
developing on the horizon, and then in the final few seconds before the sun had risen
1:05
or fallen, they saw bright bands of light radiating out from the surface, sharply ascending
1:11
out into the darkness [1].
1:13
On Earth, we enjoy these dazzling rays twice a day as a result of our atmosphere scattering
1:18
sunlight
1:19
But the moon doesn’t have an atmosphere.
1:22
There are tiny amounts of some noble gases like helium and argon in the lunar exosphere,
1:28
but for all purposes, the space above the surface of the moon is a vacuum.
1:34
So, where did these bands of light come from?
1:38
The answer doesn’t lie with atmospheric gasses, but, instead, dust.
1:44
The phenomenon observed by Apollo astronauts was caused by light passing through and being
1:49
scattered by layers of microscopic lunar dust that had been kicked off the surface of the
1:54
moon.
1:55
For the astronauts of the Apollo missions, this would have been a beautiful thing to
1:59
witness, but lunar dust has a dark side.
2:03
After the end of the final Apollo mission, Gene Cernan - who was also the last person
2:08
to set foot on the moon - said the following: “I think dust is probably one of our greatest
2:13
inhibitors to a nominal operation on the Moon.
2:15
I think we can overcome other physiological or physical or mechanical problems except
2:21
dust.”
2:22
[2] From reports taken from the seventeen Apollo
2:24
missions as well as analysis of spacesuits, machinery and equipment after they had returned
2:29
to Earth, we now have a very clear picture of just how damaging lunar dust can be.
2:36
It significantly obscured the vision of astronauts during lunar landings; it caused damage to
2:41
pre-existing machinery and objects on the lunar surface when blown around by the blast
2:46
from landing spacecraft; it found its way into the lunar and command modules, not only
2:52
causing eye, nose and lung irritation for the astronauts, but also covering screens,
2:58
damaging electronic equipment and corroding mechanical switches; it affected and sometimes
3:03
complete broke watches, cameras, rovers and experimental equipment used on the surface
3:08
of the moon and found its way into every crevice in the astronauts spacesuits.
3:13
Hose locks and zippers became difficult to use, the mobility of the suit was reduced,
3:18
life-support system displays were difficult to see, visors were scratched, electronics
3:23
overheated, and leaks in the suits became more prevalent, leading to pressure losses.
3:27
And even when they tried to remove the dust with vacuums and brushes in the lunar module,
3:32
they were never able to completely get rid of it, causing the spacesuits to become gradually
3:36
worse over time [3].
3:38
The astronauts of Apollo 17 spent the longest amount of time outside of the lunar module,
3:43
but only managed 22 hours of Surface EVAs, during which almost irreparable damage was
3:49
done to the spacesuits - had they conducted more work on the lunar surface, the suits
3:54
would eventually have been rendered useless..
3:57
But 22 hours is only a fraction of what would be required for any future mission to the
4:03
moon.
4:04
In 2015, NASA laid out its Space Technology Roadmaps which identified one key and hugely
4:10
ambitious goal [4].
4:11
They wanted their spacesuits to be able to survive for 100 EVAs - a total of 800 hours
4:17
spent on the Lunar surface, almost 37 times the duration the Apollo 17 astronauts spent
4:23
outside.
4:24
More than any other problem facing NASA or any other space agency, this could be the
4:29
making or breaking of a long-term outpost on the surface of our moon.
4:34
But how do you begin to extend the life of a spacesuit by this much?
4:39
To get to an answer, we first need to understand how lunar dust is formed and why it sticks
4:43
to anything it comes in contact with.
4:46
Unlike the surface of the Earth, the surface of the moon is under almost constant bombardment
4:52
from small and large meteorites, some of them only micrometers in diameter.
4:57
This rain of debris causes parts of lunar rocks to break off, creating a layer of fine
5:02
dust on the lunar surface.
5:04
Occasionally, these micrometeorite impacts hit with such force that they melt the minerals
5:10
contained in the soil, turning them into glass.
5:13
Lunar dust is a mixture of super-fine particles and razor-sharp glass that’s also incredibly
5:19
dry - there’s no water in the soil or air to clump the particles together and no natural
5:25
erosion through wind to blunt the sharp edges [5].
5:28
So, this obviously does not mix well with the intricate mechanisms of the lunar spacesuits.
5:33
The dust is small enough to get into almost any gap, and, thanks to the shards of glass
5:38
in the dust, it can easily scratch glass or metallic surfaces.
5:42
But this is only the beginning of the problem.
5:45
Thanks to the lack of atmosphere or magnetic field on the moon, lunar dust is exposed to
5:50
every fraction of radiation that’s fired at it.
5:53
On the side of the moon exposed to the sun, particles in the dust are hit with X-ray and
5:58
ultraviolet radiation, causing electrons to be knocked off, creating positive charges
6:03
on the surface of the dust particles.
6:06
Then, on the side shielded from the sun, the opposite happens.
6:10
The particles pick up electrons from solar winds, causing them to become negatively charged.
6:16
These positive and negative charges on the particles create electrostatic potentials
6:21
on the surface of the moon, reaching up to 20 V on the day side, and an astonishing -3800
6:28
V on the night side.
6:30
When the Apollo 8 astronauts saw the beautiful bands of light at sunset and sunrise, they
6:36
weren’t seeing the scattering of radiation through atmospheric gasses, but instead light
6:41
passing through a column of fine dust fired up from the surface of the moon by electrostatic
6:46
levitation - dust particles of like charges repel each other, and are repelled by the
6:51
lunar surface, creating a fountain of sharp microdust that rises above the horizon.
6:57
This is the same dust that Apollo astronauts walked through and kicked up as they worked
7:02
outside the lunar module, sticking to their suits in the same way a statically-charged
7:07
balloon sticks to your clothes.
7:09
Charge is one of the main reasons the dust is so annoying, but it could also be the way
7:13
we get rid of it.
7:15
In 2021, as part of NASA’s Breakthrough, Innovative & Game-changing Idea Challenge,
7:20
they tasked university students from across the world to come up with novel ways of dealing
7:25
with the lunar dust problem [6].
7:27
Some of the winning solutions included conductive fibers inspired by chinchilla hair, an electrically
7:32
charged brush that could be powered by UV radiation, and a fabric for spacesuits that
7:37
mimicked the way certain insects use hair-like structures to collect and deposit pollen.
7:42
All these ideas use different ways to solve the same problem, but they share a common
7:47
approach - using charge to either passively or actively remove dust from spacesuits.
7:53
At its simplest, the problem comes down to this - how do you make the outer layer of
7:57
the spacesuit repel the charged dust instead of attracting it?
8:01
NASA came up with an elegant solution.Instead of trying to completely redesign the outer
8:05
layer of the suit, they decided to create a system that could be easily integrated into
8:11
the pre-existing layers of fabric and material found in the current generation of spacesuits.
8:17
Their idea was to create a suit that could make its own electrical current which would
8:22
actively eject dust, acting like some sort of energy shield.
8:26
And the first challenge was choosing the conductive material that the electrodes would be made
8:30
from.
8:31
This method of dust-ejection wasn’t new.
8:33
It was inspired by the Electrodynamic Dust Shield systems th at had been used by NASA
8:38
since the late 1960s, on things like solar panels, cameras and thermal radiators [7].
8:44
But in almost all of these cases, the electrodes - which were made out of silver, copper or
8:49
a compound of indium and tin - were placed on rigid, fixed bodies.
8:54
A spacesuit is designed to move - the outer layer is made up of segments of overlapping
9:00
fabric that roll over each other at the joints when the astronaut moves their arms or legs.
9:05
So, while the silver and copper electrodes used in the pre-existing EDS systems might
9:10
be excellent electrical conductors, with their low elasticity, they wouldn’t survive the
9:15
fatigue caused by the constant flexing of the joints.
9:18
So, a new conductor was needed, one that had a high electrical conductivity, but that was
9:24
flexible enough to withstand the significant forces exerted on it during extravehicular
9:29
activities.
9:30
And the answer was carbon nanotubes.
9:33
These are cylindrical tubes of carbon atoms stretching only a nanometer across, with walls
9:39
one atom thick - like a long, thin layer of graphene that’s been rolled into a tube.
9:44
Carbon nanotubes are incredibly strong, with a considerably higher tensile strength than
9:49
copper, silver or gold and they have a very high electrical conductivity.
9:53
\ Animation 9 continued…
9:54
CNTs are also very light.
9:56
If you compare the mass of different conductors required to create an Electrodynamic Dust
10:01
Shield on the knees, elbows and boot areas of a lunar spacesuit, around 101 g of copper
10:08
wire would be needed, but if you replace the copper with carbon nanotubes, you only need
10:13
about 16g:
10:15
Carbon nanotubes are an excellent choice, as they could provide high conductivity with
10:19
low mass, while also being able to withstand the 800 hours of EVAs required for future
10:25
lunar missions.
10:26
So, after settling on CNTs, it was then a matter of finding a way of integrating these
10:31
nanotubes into the outer layer of the spacesuit.
10:35
Lunar spacesuits are made up of up to 21 layers of material, with an outer orthofabric layer
10:40
composed of a mixture of fibers like GORE-TEX and Kevlar.
10:44
The carbon nanotube electrodes were made into yarns and then woven into this outer layer
10:50
in a longitudinal direction to limit the tensile force applied to the electrodes, and they
10:56
were also spaced out from each other to prevent electrical arcing.
11:00
The orthofabric in this outer layer acts as a natural insulator, but there is a chance
11:05
it could be broken down by high voltages.
11:08
Through testing, it was found that the orthofabric could withstand up to 1200 V, so the dust
11:14
removal system was capped at around 1000 V to prevent dielectric breakdown of the insulating
11:19
material.
11:20
So, how does the dust removal system actually work?
11:24
The carbon nanotube electrodes are first connected in parallel, and then activated by a multi-phase
11:29
alternating current at voltages between 600 and 1000 V and very low currents, at around
11:35
3 mA.
11:36
This sets up repeating waves of electrical fields which move across the outer surface
11:41
of the spacesuit.
11:42
As they interact with the charged dust particles, they add an additional repulsive force to
11:48
the particles based on coulomb interactions - repulsion due to the interaction of two
11:53
charged objects.
11:54
This repulsive force is, overall, greater than the gravitational and adhesive forces
11:59
which stick the particles to the suit, causing the particle to be ejected from the orthofabric.
12:05
But this also works for uncharged particles that are stuck to the suit.
12:09
When interacting with a non-uniform electric field, like in this system, uncharged dust
12:14
can be repelled through something called a dielectrophoretic force..
12:18
Overall, the electrical energy of the system is transformed into mechanical energy as the
12:24
dust is kicked off the suit.
12:26
To test the system, NASA constructed a prototype knee joint with carbon nanotubes woven into
12:32
an outer orthofabric layer, and used it to measure how much of a lunar dust simulant
12:37
was removed in different scenarios.
12:39
[8].
12:40
And what they found was remarkable.
12:42
Through analysis of high resolution images taken of the fabric before and after activation
12:47
of the electrodes, they saw, that up to 96% of the lunar dust simulant was removed by
12:53
the system (see here for video) This has enormous potential for use as part
12:57
of future moon missions.
12:58
The dust removal system could be on continuously during EVAs, preventing any dust from binding,
13:04
or it could be manually activated when an astronaut noticed a large build up of dust.
13:09
This dust prevention technology may seem trivial, but this razor sharp lunar dust is a life
13:14
limiting threat to any future moon colony.
13:17
This kind of simple environment effect, that requires a breakthrough material to overcome,
13:22
is the core of what makes engineering exciting for me.
13:25
A relatively simple solution that any new engineering graduate could have helped develop,
13:30
and go on to see their work land on the moon.
13:33
Seeing your work go from the lab, to the factory floor, to the real world is one of the most
13:37
satisfying creative processes in the world.
13:41
Engineering is a job for creatives, with a penchant for science and math, and many talented
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Did you do that transcription manually? Very helpful. Thank you.

On the YouTube screens, there's one of those icons (looks like horizontal bars stacked up I think) and there are two options in there, one of which is generate transcript. Found it not long ago, weird that it's not right out there. Anyway, comes in handy to head off the bitchy trolls who immediately post "summarize" crap.

And my pleasure.

Math be waycisssss?

Thank you! Much appreciated.

My pleasure.

Let me know when they solve the super abrasive moon dust problem.......

Giant hamster balls.

https://www.google.com/search?q=hamster+ball

S.C. Great notes! Thanks for providing. (I think we can dispense with that idea of a German dark side moon base once and for all! :)

Seeing your work go from the lab, to the factory floor, to the real world is one of the most satisfying creative processes in the world.

Just ask the biomeds in Wuhan.

Not so fast. Once the next gen astronerds visit the old landing site, they’ll see if some prankster drew “wash me” (in German) on the side of the LM.

I think we can dispense with that idea of a German dark side moon base once and for all!

Whew, that's a relief. Never mind, boys - it's just a natural formation!

Iron

Could the Moon be useful in our quest to know the Universe? Possibly but not any time soon. The fact is that until we achieve velocity in the 1000 of miles per second rate as opposed to the less than 10 we have now, we are going nowhere.

So in the world of disconnected events, there was a thread on FR not that long ago that talked about the mechanism of Boric Acid and Diatomaceous Earth in killing insects. It worked pretty much the same as moon dust, getting in the joints of the insect and tearing it apart.

I wonder how James Burke would treat this as an episode of Connections. /rhetorical

In my late parents’ youth, a mixture of powdered sugar and borax worked well for roaches and ants.

Here’s the topic you mentioned I think:

https://freerepublic.com/focus/bloggers/4070791/posts

Using a pellet (on the interstellar probe) and laser (from orbit) and making the probe large enough to be useful but light and durable, is our only shot right now.

Overly dramatic video title - its lunar dust short answer.