Spacesuits

[RCgothic]

This "reveal" seems like a load of nothing to me, given that they're using a cover layer on the space suit to conceal the actual details.

 

 

Edited March 15, 2023 by RCgothic

[tater]

1 minute ago, RCgothic said:

This "reveal" seems like a load of nothing to me, given that they're covering the actual space suit to conceal the actual details.

They made it pre-dirty I see.

[AckSed]

4 minutes ago, RCgothic said:

This "reveal" seems like a load of nothing to me, given that they're using a cover layer on the space suit to conceal the actual details.

And not because it looks cooler.

All right let's see what we can work out here. Rotation on the hands, shoulders, hip joints... boots? Unless it's just detatchable, which I approve: a quick way to swap out a part that sees the most wear, at the cost of another seal.

[tater]

 

[tater]

 

 

Showing the whole suit live. The teasers were hiding it on purpose I guess.

Moon suit will be white.

Unsure why they did dark right now

[sevenperforce]

Looks like a pretty normal rear entry suit with a hard torso, limited shoulder mobility, and standard legs and gloves. 

[nascarlaser1]

31 minutes ago, tater said:

Moon suit will be white.

Unsure why they did dark right now

From a Safety perspective: understandable

From an aesthetic perspective: BOOOOO (My fav color is black so I'm biased XD)

Now whos going to mod this into KSP 1?

[kerbiloid]

The wand is meh.

A halberd is true.

[darthgently]

It is for the polar area so black would be fine down in a perma-dark crater I suppose.  But yeah, black was probably more about a temp measure of revealing little as possible, not just to possible commercial competitors, but state competitors perhaps also

[kerbiloid]

1 hour ago, darthgently said:

It is for the polar area so black would be fine down in a perma-dark crater I suppose.

+1

The Axiom-1 lunar mission.

Spoiler

Do they realize that a dirty lunar suit looks crappish-brown rather than gray?

[DDE]

14 hours ago, tater said:

 

Michail Kotov over here is convinced that this is just a very expensive repaint of the NASA xEMU with none of the potential issues rectified.

https://t.me/space78125/1623

[tater]

13 minutes ago, DDE said:

Michail Kotov over here is convinced that this is just a very expensive repaint of the NASA xEMU with none of the potential issues rectified.

Um, it is that suit I believe. The problems were primarily schedule/cost related (there was an OIG report I think). Outsourcing production solves many of those, presumably.

What are the other issues?

Edited March 16, 2023 by tater

[kerbiloid]

23 minutes ago, tater said:

What are the other issues?

The Telegrams post tells about 160 kg mass, huge joints and their dust pollution, poor design of gloves and boots. Do they need more?

[tater]

14 minutes ago, kerbiloid said:

The Telegrams post tells about 160 kg mass, huge joints and their dust pollution, poor design of gloves and boots. Do they need more?

Thanks for the translation.

The mass is not terribly important on the moon. xEMU was 126 lbs (57 kg) which is fine on the Moon. Suit mass from a mass budget standpoint is not a thing, they are using Starship.

Dust is always an issue for lunar suits. Dunno about the gloves and boots. On the plus side they will have ample room to potentially take care of any suit issues, heck, bring spares—they're taking a decent size suburban house with them.

[kerbiloid]

Just now, tater said:

The mass is not terribly important on the moon

The weight isn't. The mass is important even in zero-g, it's inertion.

[tater]

EDIT: could they have typoed 160 lbs to 160 kg (damn potato units)? It;s plausible it gained mass tom xEMU, but 160 lbs is only 72kg, not a meaningful difference in lunar gravity (momentum always a problem in any suit in that environment, obviously).

1 minute ago, kerbiloid said:

The weight isn't. The mass is important even in zero-g, it's inertion.

Yeah, but that is true regardless. Even inside in shirtsleeves someone with muscles attuned to 1g will likely have issues in low gravity with their inertia.

And the difference between 57kg and 72kg is not huge (I don't buy the 160 kg number without a link to NASA/Axiom saying that is the mass).

The total Apollo eva suit mass was 91kg as a reality check.

 

US reporting is saying the suits are lighter than the Apollo suits.

[tater]

Actually 160kg is within limits.

The NASA requirement was initially 186.6 kg. This is for the whole system, and might well include total (mission?) consumables, it's hard to tell from the NASA doc. Total mass was then dropped to 177 kg. At the time of the OIG report, the suit was 183kg—overmass for the new standard.

The mass reduction goals could not be met with their internal design because they lacked funding for advanced materials. Not a thing with the new contractor. They were also focused on lowering mass for the xPLSS component (heaviest part).

The principle concerns are I imagine an Orion issue. Mass and stowage issues for it are... nontrivial.

Edited March 16, 2023 by tater

[sevenperforce]

As I understand it, the current space suits that NASA will be buying for EVA use on the moon will still use a water-based open-loop evaporator for cooling the suit, limiting the time-persistence of EVAs.

What if you could use a radiative solution?

The human body produces around 200 W/m^2 of heat during moderate to high metabolic activity. Using the Stefan-Boltzmann law with a maximally efficient radiator (if my math is correct), you only need your radiator to operate at 242 K, well below the temperature of the human body.

Of course you won’t have a maximally effective radiator. And you’ll also have to deal with the thermal conditions on the moon. Half of your body will be in direct sunlight, absorbing 1368 W/m^2, while the other half will be absorbing lunar-reflected sunlight at 97 W/m^2. Adding this average to the average metabolic output of a human, the actual heat rejection requirement is 932.5 W/m^2, which requires a radiator temperature of 358 K, which at 85°C is MUCH higher than the temperature of the human body.

But what if there was another way?

Imagine the outer surface of a spacesuit covered in cells with a white substrate that ordinarily reflects solar radiation, but can fill with a carbon-doped coolant with high emissivity. The cells in direct sunlight are kept empty of coolant so that they reflect heat, while the cells in shadow are saturated and reject heat.

The cells in shadow will still be absorbing light reflected by the lunar surface at 97 W/m^2. Let’s imagine for the sake of argument that the empty cells will have 97% reflectance, 3% emissivity, and 3% absorption, while the saturated cells have 97% emissivity, 3% reflectance, and 97% absorption.

Half of the suit exterior, then, will be absorbing 41 W/m^2 while the other half is absorbing 94.1 W/m^2, all while needing to reject the 200 W/m^2 that the body inside is producing. The total heat rejection required is therefore 267.5 W/m^2. Half of the body has 97% emissivity and half has 3% emissivity, so the average emissivity is 50%. The radiative heat rejection capacity needs to be 535.1 W/m^2. By the Stefan-Boltzmann law, your radiator only needs to be operating at 38.5°C.

Obviously that’s still above human body temperature, but not by much. Assuming a Carnot coefficient of performance on the order of 3.0, a compressor-based heat exchanger would only need to provide the equivalent of 7.5 degrees of thermal differential to keep the astronaut at the equivalent of a balmy shirtsleeve environment. I can’t remember the thermodynamics for that, but it can’t be much energy. 

[NFUN]

I'd worry about the color of the spacesuit being very important to get to the apparently low margin of effectiveness. The moon has a pretty low albedo and you wouldn't want its dust, which is famously for sticking everywhere, to cook the astronaut if it starts building up everywhere

[Piscator]

Well, assuming your smart cooling system works, you could just add a pair of giant stylish angel wings to your suit to increase the radiative surface. Or you could carry an equally stylish parasol.

[kerbiloid]

7 hours ago, sevenperforce said:

Let’s imagine for the sake of argument that the empty cells will have 97% reflectance

According to the civil defence reference book, nuke heat radiation: polished aluminium = 0.95, polished copper = 0.96, so the suit should be almost mirror.

But what's even worse:

Spoiler

And this is ~0.7.

***

Still insisting on good old classics, proven by time.

Spoiler

 

[FleshJeb]

@sevenperforceSome further items for consideration:

• How much heat is the expansion of the breathing air from the tanks absorbing?
• How much gets dumped by venting the CO2? (I'm assuming this is open-cycle.)
• How much gets dumped by venting the humidity produced by the body? (Also assuming this is open-cycle.)
  • From professional experience, I would assume 2-3L of water consumption over an 8 hour shift at comfortable temperatures. Push that to 4-6L at higher temperatures (35-40C) and exertions. (I wonder how they deal with salt build-up in the suit? At those volumes, a cotton t-shirt will stand on its own just from salt-encrustation.)

[tomf]

I don't know how you would do open circuit CO2. It's going to be a lithium hydroxide scrubber, which releases additional heat as it absorbs CO2.

For divers you insert a stick with temperature sensors into the scrubber cartridge and by measuring where the heat from the reaction front has reached to sense how much of the scrubber has been used.

Edited March 21, 2023 by tomf

[kerbiloid]

5 hours ago, FleshJeb said:

From professional experience, I would assume 2-3L of water consumption over an 8 hour shift at comfortable temperatures. Push that to 4-6L at higher temperatures (35-40C) and exertions.

This! They should boil the sweat and evaporate it outside instead of another coolant.

A biomechanical open-cycle stinky suit.

***

As there is a lot of Dune fans on this forum, why not refer to the wizdom of freemen?

Just cover the suit with rubber to prevent any evaporation, and you can walk in a hottest desert endlessly.

At least, the Dune says so.

Edited March 21, 2023 by kerbiloid

[tater]

My pref for an orbital suit. ^^