EVAActive🇺🇸
Extravehicular Mobility Unit
Designation: EMU
The defining American EVA suit — 400+ ISS spacewalks, Hubble repairs, and decades of orbital construction in a single iconic white suit.
About This Suit
The Extravehicular Mobility Unit (EMU) has been NASA's primary EVA suit since its first use on STS-6 in April 1983, and it remains active on the ISS today — one of the longest-serving pieces of operational space hardware in history. Its defining innovation is a two-piece modular design: a hard fiberglass upper torso (HUT) and a soft lower torso assembly (LTA) that can be resized on-orbit using a set of sizing rings and components stored at the ISS — meaning one suit can fit crew members of different sizes. The 14-layer construction includes a Liquid Cooling and Ventilation Garment (LCVG) over the astronaut's body, the pressure bladder, Dacron restraint, multiple aluminized Mylar thermal layers, and an outer Ortho-fabric shell. The PLSS backpack is a self-contained life support system providing 8 hours of O₂, CO₂ scrubbing via lithium hydroxide canisters, battery power, and communications. A SAFER (Simplified Aid for EVA Rescue) thruster backpack is worn over the PLSS for untethered emergency return capability.
Key Features
- 1Two-piece modular design: resizable on-orbit to fit different crew members
- 214 material layers including LCVG, pressure bladder, Dacron restraint, Mylar, Kevlar, and Ortho-fabric
- 3Fully self-contained PLSS: 8-hour O₂, CO₂ scrubbing, thermal, battery, comms
- 4SAFER jet-pack attachment for untethered emergency return capability
- 5Independent of spacecraft — astronaut becomes a self-contained life support system
- 6400+ ISS EVAs performed; Hubble servicing missions (1993–2009) highlight reel
Historic Missions
1983
STS-6 (first use)
First operational EMU EVA — Story Musgrave and Don Peterson
👨🚀 Story Musgrave, Don Peterson
1993
Hubble SM1
First Hubble servicing — installed COSTAR corrective optics, saving the telescope
👨🚀 Story Musgrave, Jeffrey Hoffman, et al.
2009
Hubble SM4
Final Hubble servicing — installed WFC3 and COS instruments extending Hubble's life to 2040+
1998
ISS Assembly (400+ EVAs)
Complete assembly of the International Space Station across 400+ EVAs spanning 25 years
Engineering & Research Highlights
- ◆Modular on-orbit resizing proved that a single EVA suit design could serve crews of widely varying physiques — key insight for multi-decadal ISS operations
- ◆Pre-breathe protocol research identified that 4.3 psi pure O₂ operation requires 4+ hours of pre-breathe to prevent decompression sickness from ISS 14.7 psi atmosphere
- ◆Hubble SM EVA tool development produced innovations in microgravity tool design now applied to planetary EVA planning