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Developing the xEMU for deep space exploration

April 23rd, 2018 / By: , / Featured

NASA’s next generation spacesuit will require new textiles to meet extreme demands.

The design of the new xEMU spacesuit will utilize some of the technologies in thIs NASA Z-2 suit, which is a technology demonstrator for a planetary surface suit. Photo: NASA

Human space exploration is one of the most ambitious and exciting endeavors upon which mankind has ever embarked, and it has always been an integral part of the U.S. space program. The National Aeronautics and Space Administration (NASA) sent our first astronaut, Alan Shepard, on a suborbital flight in 1961, and eight years later landed a pair of astronauts on the Moon with the Apollo program. Since then, the U.S. human spaceflight program has focused on Low Earth Orbit (LEO) with the Space Shuttle and International Space Station (ISS) programs.

Various highly functional spacesuits developed by NASA and its contractors were instrumental in the success of all these programs, and textiles were used extensively in the spacesuits. New and more advanced textiles are needed for developing NASA’s next generation spacesuit, the xEMU, for manned missions beyond LEO and into deep space.

The Deep Space Gateway

NASA has sent unmanned spacecraft to Mars and into interstellar space, but manned missions have not gone beyond the Moon since the Apollo program. With renewed interest from the public and with government directives, NASA is setting its sights on sending humans beyond the Moon via the Deep Space Gateway (DSG) missions, eventually with missions to Mars.

The DSG will operate in deep space near the Moon and allow NASA to gain experience for human missions that push farther into the solar system in preparation for missions to Mars. In order to achieve this vision, NASA is developing the next generation spacesuit, or Extravehicular Mobility Unit (EMU), for operation on planetary surfaces.

NASA’s next generation spacesuit will be developed as part of the Exploration Extravehicular (EVA) System. The early stages of the development will involve building a Deep Space EVA System called xEMU for demonstration on the International Space Station (ISS) and during DSG missions. The xEMU is the precursor for the future Mars Surface EVA System, mEMU. The xEMU spacesuit will be utilized in the first 3 phases of the DRMs, and its development has immediate needs for the infusion of advanced textile technologies.

NASA will be developing the xEMU spacesuit pressure garment system (PGS) in-house at the Johnson Space Center. The advanced spacesuit team will need to work with the textile industry and academia to leverage state-of-the-art textile technologies and new advanced textiles for this development. The primary function of the xEMU PGS is to protect astronauts from the harsh environment in cislunar space and on the lunar surface.

It will have exploration mobility capabilities, which the current EMU spacesuit lacks, to operate on a planetary surface. The design of the xEMU spacesuit will utilize some of the technologies in the NASA Z-2 suit, which is a technology demonstrator for a planetary surface suit.

The architecture of a spacesuit
Photo: NASA.

The general soft-goods architecture of a spacesuit consists of a pressure enclosure, a Thermal Micrometeoroid Garment (TMG), and a Liquid Cooling and Ventilation Garment (LCVG). On the ISS EMU, the TMG is constructed with an outer-shell layer of a Nomex/Teflon/Kevlar 14-oz. ripstop, woven fabric called Ortho-Fabric. This provides abrasion, tear and micro-meteoroid protection while maintaining the required surface optical properties for space suit thermal control.

Underneath the Ortho-Fabric are several thermal insulating layers of aluminized polyester film, or Mylar, with a bonded polyester scrim. A neoprene-coated ripstop nylon “liner” completes the TMG and provides additional micrometeoroid protection. The pressure enclosure for the EMU system currently consists of a Dacron “restraint” fabric with a polyurethane-coated nylon “bladder.” The restraint provides the required structure for the pressure, human and external loads, while the bladder encloses the oxygen environment and provides the leak-tight element of the system.

The LCVG is worn underneath the pressure enclosure and is designed to circulate cold water and oxygen in order to cool the user and ventilate the system. The current LCVG uses a stretch, nylon knit fabric integrated with ethyl vinyl acetate (EVA) cooling tubes and a nylon tricot comfort liner. This entire system together provides the functionality of the soft elements of the space suit and protects the user from the external environment.

Although the xEMU PGS will likely have a similar general construction philosophy as the current EMU, the fabric materials will need to have added functionality and enhanced properties to enable operation on the lunar surface. Identifying or developing new materials for the TMG will be the focus of the xEMU PGS materials development effort. The immediate advanced textile needs for xEMU PGS are a dust-resistant, outer-layer fabric and a high-performance, metalized thin-film insulation material. NASA has set Key Performance Parameters to identify the major areas where improvement is sought over the current system.

The lunar dust challenge

The challenge for the xEMU PGS outer-layer fabric is to protect against the lunar regolith, or “lunar dust,” found on the lunar surface. Although the current EMU outer layer, Ortho-Fabric, has a tight-weave structure, it is still susceptible to dust penetration that could damage the material layers underneath. Analysis of the Apollo spacesuits that were worn on the lunar surface found that lunar dust is highly abrasive and it tends to adhere to the outer layer fabric. Lunar dust embedded into the fibers of the outer fabric appeared to promote wear.

The dust carried by the fabric can also contaminate other spacecraft systems and affect their performance. Therefore, the xEMU outer-layer fabric needs to provide dust protection, which includes resistance to dust adhesion, abrasion and penetration. Highly flexible, woven fabric with a durable coating could be a possible solution.

In addition to dust resistance, the material should have the following properties:

  • Excellent abrasion, wear, tear and puncture resistance
  • High infrared emissivity and low solar absorptance to enhance thermal radiation protection
  • Flame resistance in an oxygen-enriched spacecraft environment
  • Low outgassing in thermal vacuum environment
  • High temperature (+250 oF) resistance
  • Low temperature (-250 oF) flexibility
New and improved solutions

A new solution for the current metalized-film insulation material is also sought for the xEMU PGS development. The new material should be similarly lightweight as the current thin-film construction and provide optimal thermal radiation and conduction insulation in a high-vacuum environment. Material with high flexibility and good durability while enhancing insulation performance is desirable.

An alternative to the current neoprene-coated, nylon ripstop liner material should also be explored. The new material should be non-abrasive, lightweight and high-strength, which is able to improve the ballistic and hypervelocity protection performance of the system.

It is exciting to look forward to the future human exploration mission to Mars in the 2030s. There are unique textile application challenges that will provide opportunities for technology innovation in the development of the mEMU spacesuit. There is a need to develop a flexible and robust hybrid thermal insulation that can perform both in a space vacuum environment and in the Martian low-pressure atmosphere.

Innovative PGS designs and architectures utilizing multi-functional textiles for the mEMU spacesuit should be explored. The advanced spacesuit development team at NASA JSC is looking forward to collaborate with the textile industry and academia to identify advanced textile solutions for the immediate xEMU PGS needs and the future mEMU spacesuit development challenges, and to fulfill the NASA human space exploration missions.

 

Henry Tang is a senior materials engineer at NASA Johnson Space Center, responsible for testing, evaluating, and selecting materials for space flight systems applications.

Ben Peters is an engineer at NASA’s Johnson Space Center who works on the design, development, evaluation and testing of advanced planetary space suits and their related systems.