Author Topic: EMU Q&A  (Read 3614 times)

Offline coypu76

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EMU Q&A
« on: 11/24/2014 09:49 PM »
The current NSS forums break down primarily into discussions of launch vehicles and spacecraft, but I'd like to make the case that there is another area of space technology that merits its own forum category: Space Suits.
The history and development of space suits is key to the manned exploration of space, and just as the U.S. is about to have three different manned spacecraft (Orion, SpaceX's Dragon v2, and Boeing's CST-100) there is a lot of space suit development going on.
It's possible that some of the forum members here are not aware of the types of space suits that exist, for IVA and EVA activities, for instance.  Prior to the retirement of the Shuttle, there would have been four types of space suits on the ISS during a Shuttle visit:

US ACES Shuttle IVA (David Clark)
US EMU EVA (ILC Dover)
Russian Sokol IVA (НПП Звезда)
Russian Orlan-MK  EVA(НПП Звезда)

A lot of development is going on.  Existing suit technology is mature - the Sokol and Orlan suits have been around for decades.  The ILC Dover EMU, the American EVA suit, was designed in 1979, and some of the actual suits in use are nearly that old.  For Orion's visit to an asteroid, Nasa is looking at modifying the ACES suit with gloves and boots from the EMU to allow some ability to move around in the microgravity environment of an asteroid without having to have multiple space suits on board - this is the MACES (Modified ACES) suit.

Also under development are the Z-1 and Z-2 rear entry suits at NASA.

Besides old hands ILC Dover and David Clark, there are a number of new space suit companies trying to break in:

Orbital Outfitters (contracted by SpaceX)
Final Frontier Design (partners are an NPP Zvezda engineer from Russia, and an American designer)

Beyond the suits themselves, what kinds of life support systems will be used in new technology?  What kinds of monitoring, control, navigation and information systems will be incorporated into new suits?

There are lots of launch vehicle geeks on this forum, but I hope I'm not the only person interested in space suit technology.  I'd really like to see a Space Suits section here on NSS.  What say ye, gods of the forum?

Coypu
« Last Edit: 11/24/2014 10:29 PM by Chris Bergin »

Online sanman

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Re: EMU Q&A
« Reply #1 on: 11/24/2014 10:27 PM »
There's already a new section for In Space Hardware, and there are discussion threads on space suits in that forum. Maybe that would be a good place to discuss some of these things.
« Last Edit: 11/24/2014 10:29 PM by Chris Bergin »

Offline Chris Bergin

Re: EMU Q&A
« Reply #2 on: 11/24/2014 10:33 PM »
A thread is fine and I've created it via this. No way is there enough for a section. That requires at least 40 or so threads. There isn't anywhere near that many threads.


Offline coypu76

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Re: EMU Q&A
« Reply #3 on: 11/28/2014 03:57 PM »
Dr. Richard D. Watson of the Johnson Space Flight Center in Houston presented a paper at the International Conference on Environmental Systems in Tucson, AZ, back in July, discussing initial testing of the Modified ACES (MACES) space suit as a candidate EVA suit for Orion exploration missions which have a need for EVA capability in microgravity environments.  Link to the full report is here:  http://forum.nasaspaceflight.com/index.php?topic=36150.0

The MACES suit is a modified David Clark ACES suit, the same pressure suit worn for launch and recovery of Shuttle missions prior to the retirement of that system.  A primary reason for consideration of this suit for EVA is a very simple one:  The Orion cannot carry enough mass for both IVA and EVA suits for astronauts on deep space missions.  Rear entry suits like the Z-2 by ILC Dover or the Orlan MK by NPP Zvezda are unsuitable for launch and recovery operations because their design does not allow any position where astronauts can be subjected to acceleration forces like those of re-entry and touchdown/splashdown safely and comfortably.  The same is true of the venerable EMU, with its rigid upper torso and multiple limb bearings:  great for EVA but unsafe for re-entry and landing.

Back in the 1970s the Apollo missions faced the same challenge of mass, and the AL-7 and AL-7B suits worked well for launch and recovery operations as well as EVA operations on the Moon and in microgravity, demonstrated in Russell Schweickart's Apollo 9 EVA and during a total of nine EVA activities during Skylab.  The AL-7 series proved quite versatile. 

Today, however, we don't have a dual purpose suit available.  The Shuttle program used the LES up to the STS-65 mission and was completely phased out by the STS-88 mission.  From STS-65 Shuttle missions used the ACES suit.  Both suits were manufactured by David Clark and were designed to be IVA-only suits:  survival support for astronauts during launch and recovery operations.  The LES was only a partial pressure suit and wholly unsuitable for EVA, whereas the ACES suit had a full pressure bladder.

NASA modified the ACES suit and Dr. Watson's report on testing of the MACES suit in three environments:  Suspension mobility testing using the ARGOS testing frame at Houston, microgravity testing on the vomit comet, and under water in the Neutral Buoyancy Laboratory.  MACES will require further modification for umbilical support or support for a PLSS backback, but right now it has a few advantages:  It's relatively cheap, being modified from an existing suit design.  It can be used for launch/recovery operations as well as limited EVA operations, and it's fairly lightweight, addressing the mass limit issue.  But it wasn't designed to be an EVA suit, and so there are challenges.

It looks like right now, the first manned Orion misssions will use the MACES suit, but it will be very interesting to see what SpaceX and Boeing decide to use for launch and recovery operations in the Dragon v2 and the CST-100.  Both of the latter craft right now have only a mission of delivery crews and payload to destinations in LEO, but both may be used for other purposes as orbital capabilities and opportunities increase (Bigelow and others).

[Doug's corrections are noted and appreciated, but I'll leave my mistakes in the original post, acknowledging them as such - coypu]
« Last Edit: 11/29/2014 05:05 AM by coypu76 »

Offline the_other_Doug

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Re: EMU Q&A
« Reply #4 on: 11/29/2014 04:16 AM »
One terminology correction -- the Apollo-era ILC suits were designated A7L and A7LB.  Not AL-7 and AL-7B.  Each was also separated into EV and IV versions, the EV versions designed for the LM crews and the IV versions for the CM pilot.  (The A7LB version of the IV suit was actually EVA-capable, but only from the CSM, as it lacked any ability to interface with a PLSS and depended on a special umbilical connection within the CM.)

-Doug  (With my shield, not yet upon it)
-Doug  (With my shield, not yet upon it)

Offline Dalhousie

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Re: EMU Q&A
« Reply #5 on: 11/18/2015 03:03 AM »
How much water is lost from the space suit sublimator during an EVA?

Thanks!
« Last Edit: 11/18/2015 03:04 AM by Dalhousie »
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Offline AnalogMan

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Re: EMU Q&A
« Reply #6 on: 11/18/2015 01:13 PM »
How much water is lost from the space suit sublimator during an EVA?

Thanks!

This description of the feed water circuit may help answer your question:

B. Feed Water Circuit

The feed water circuit provides the capability to reject the heat from the EMU that has been either generated by the astronautís metabolic processes, from the EMUís avionic systems, from the life support mechanical systems, or from the external environment. Three reservoir tanks (one large and two small) that are initially charged with approximately 10 pounds (aprox. 4.8 quarts) of ultrapure water supply the feed water circuit. A detailed discussion regarding the necessity of the ultrapure water is addressed in subsequent sections. The feed water circuit provides enough water to support cooling for an 8-hour extravehicular activity (EVA). In the event that the 10 pounds of water from the primary tank is prematurely depleted, the reserve tanks can provide an additional 30 minutes of cooling capability at a 1000 British thermal unit (BTU)/hr metabolic rate, enough time to allow the astronaut to return to the ISS airlock.

Water flows from the feed water tanks to the sublimator, which acts as a heat exchanger between the feed water circuit and the liquid transport circuit. The sublimator operates at the triple point of water, where the three phases of water are present. Upon exposing the EMU to the vacuum of space, water flow to the sublimator from the feed water system is initiated and forms a layer of ice on the surface of the sublimator that is exposed to vacuum. After the ice layer is formed, water from the feed water circuit remains liquid by picking up the heat from the liquid transport loop via the heat exchanger in the sublimator. The heat removed from the liquid transport loop is dissipated into space via the sublimation of the sublimator ice layer. As the ice sublimates, the voids left behind in the ice layer are filled with additional water from the feed water circuit.


Note: 1000 BTU/hr is ~290 watts.  The EMU is designed for average/max metabolic rates of 1000 BTU/hr and 2000 BTU/hr respectively

Offline Dalhousie

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Re: EMU Q&A
« Reply #7 on: 11/18/2015 08:58 PM »
How much water is lost from the space suit sublimator during an EVA?

Thanks!

This description of the feed water circuit may help answer your question:

B. Feed Water Circuit

The feed water circuit provides the capability to reject the heat from the EMU that has been either generated by the astronautís metabolic processes, from the EMUís avionic systems, from the life support mechanical systems, or from the external environment. Three reservoir tanks (one large and two small) that are initially charged with approximately 10 pounds (aprox. 4.8 quarts) of ultrapure water supply the feed water circuit. A detailed discussion regarding the necessity of the ultrapure water is addressed in subsequent sections. The feed water circuit provides enough water to support cooling for an 8-hour extravehicular activity (EVA). In the event that the 10 pounds of water from the primary tank is prematurely depleted, the reserve tanks can provide an additional 30 minutes of cooling capability at a 1000 British thermal unit (BTU)/hr metabolic rate, enough time to allow the astronaut to return to the ISS airlock.

Water flows from the feed water tanks to the sublimator, which acts as a heat exchanger between the feed water circuit and the liquid transport circuit. The sublimator operates at the triple point of water, where the three phases of water are present. Upon exposing the EMU to the vacuum of space, water flow to the sublimator from the feed water system is initiated and forms a layer of ice on the surface of the sublimator that is exposed to vacuum. After the ice layer is formed, water from the feed water circuit remains liquid by picking up the heat from the liquid transport loop via the heat exchanger in the sublimator. The heat removed from the liquid transport loop is dissipated into space via the sublimation of the sublimator ice layer. As the ice sublimates, the voids left behind in the ice layer are filled with additional water from the feed water circuit.


Note: 1000 BTU/hr is ~290 watts.  The EMU is designed for average/max metabolic rates of 1000 BTU/hr and 2000 BTU/hr respectively

Thank you.  II'll work it out.  Why can't people use SI units?  BTUs?  Not even the British use BTUs. Might as well use cubits and bushels.

Grumpy that this got merged without any notice and I had to use the search function to find it again. 
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline manboy

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Re: EMU Q&A
« Reply #8 on: 11/19/2015 01:48 AM »
How much water is lost from the space suit sublimator during an EVA?

Thanks!

This description of the feed water circuit may help answer your question:

B. Feed Water Circuit

The feed water circuit provides the capability to reject the heat from the EMU that has been either generated by the astronautís metabolic processes, from the EMUís avionic systems, from the life support mechanical systems, or from the external environment. Three reservoir tanks (one large and two small) that are initially charged with approximately 10 pounds (aprox. 4.8 quarts) of ultrapure water supply the feed water circuit. A detailed discussion regarding the necessity of the ultrapure water is addressed in subsequent sections. The feed water circuit provides enough water to support cooling for an 8-hour extravehicular activity (EVA). In the event that the 10 pounds of water from the primary tank is prematurely depleted, the reserve tanks can provide an additional 30 minutes of cooling capability at a 1000 British thermal unit (BTU)/hr metabolic rate, enough time to allow the astronaut to return to the ISS airlock.

Water flows from the feed water tanks to the sublimator, which acts as a heat exchanger between the feed water circuit and the liquid transport circuit. The sublimator operates at the triple point of water, where the three phases of water are present. Upon exposing the EMU to the vacuum of space, water flow to the sublimator from the feed water system is initiated and forms a layer of ice on the surface of the sublimator that is exposed to vacuum. After the ice layer is formed, water from the feed water circuit remains liquid by picking up the heat from the liquid transport loop via the heat exchanger in the sublimator. The heat removed from the liquid transport loop is dissipated into space via the sublimation of the sublimator ice layer. As the ice sublimates, the voids left behind in the ice layer are filled with additional water from the feed water circuit.


Note: 1000 BTU/hr is ~290 watts.  The EMU is designed for average/max metabolic rates of 1000 BTU/hr and 2000 BTU/hr respectively

Thank you.  II'll work it out.  Why can't people use SI units?  BTUs?  Not even the British use BTUs. Might as well use cubits and bushels.
Because it was designed in the United States and at a time when the only other country developing EVA suits was the Soviet Union.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline te_atl

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Re: EMU Q&A
« Reply #9 on: 02/06/2016 03:06 AM »
I'm helping a friend with a story project.  He is working on a scenario where a space craft docks to a depressurized station and astronauts on a salvage team have to enter.

Since he is trying to use existing tech, he is trying to see if an astronaut outfitted with a current NASA suit variant can pass through an IDA port.  If so which one(s), and if not, what about Russian suits?


Offline sdsds

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Re: EMU Q&A
« Reply #10 on: 02/06/2016 04:10 AM »
Nominally the IDA hatch and the Russian segment docking hatches have the same passage diameter, 800mm. An astronaut suited in a NASA EMU requires 914 mm; a cosmonaut in a Russian Orlan requires 800 mm.
See: http://www.iaaweb.org/iaa/Studies/eva.pdf

Good questions by the way; Google is your friend; I'm just repeating what it tells me. :)
« Last Edit: 02/06/2016 04:11 AM by sdsds »
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Offline arachnitect

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Re: EMU Q&A
« Reply #11 on: 02/07/2016 03:03 AM »
Was just looking at something similar in another thread.

Astro/Cosmonauts in Orlan suits have practiced going from Pirs to Soyuz Orbital Module in case Pirs was unable to be re-pressurized. It was a tight fit apparently.

Tags: Spacesuits ACES MACES EVA IVA