The "Mechanical Counterpressure" (or SAS) space suit is the holy grail when it comes to mobility, flexibility, and being lightweight however it also has it's share of problems. It's very difficult to tailor, difficult to get into, and has problems conforming to complex human geometry.

The first two problems are well on their way to being solved:

  • 3D scanners and automated software can easily generate templates for suits sparing expensive and time consuming manual tailoring

  • New "smart fibers" may be able to expand and contract on command making it easy to get into and tighten electronically.

However, solving the "complex geometry" problem is a bit more difficult. In NASA's original SAS trials, they solved this by padding concave sections of the body (such as the back and armpits) with foam and more recent attempts at a MC suit such as MIT's Bio-Suit also struggled with complex joints such as the hands. It then mentions that to solve this problem, they used a separate pressurized gloves and pressurized helmet.

My question:

How is the transition from mechanical counterpressure suit to gas-pressurized suit in the case of helmets and gloves accomplished without leaking air?

Nasa trial with guy in a SAS

See helmet to suit transition

  • $\begingroup$ A lot of information about space suit pressurization, and what the astronauts deal with can be found here: en.wikipedia.org/wiki/Space_suit#Theories_of_design On a basic level (without having fact-checked) the suit is sealed, then pressurized. As long as the pressure remains stable and the seals hold, then it's not a problem; the pressurization also seems to maintain the seal in a lot of the designs I've looked at. $\endgroup$ Commented Jun 15, 2018 at 10:19
  • $\begingroup$ A problem during pressurization is to keep pressure equal between torso and head. Larger pressure differences are not healthy for the lungs, heart and blood circulation. Arms and legs are less sensitive for differential pressure. The hands may swell badly if ambient pressure is lower there. $\endgroup$
    – Uwe
    Commented Jun 15, 2018 at 16:41
  • $\begingroup$ Another problem will be the airtight seal of the helmet to the neck of the wearer. Any pressure on the carotid arteries that reduces blood flow to the brain may be dangerous. If the seal is at the shoulders, it would be difficult keep it airtight during movements of the head and the shoulders. $\endgroup$
    – Uwe
    Commented Jun 15, 2018 at 22:38
  • 1
    $\begingroup$ This expired patent may give you some food for thought: [patents.google.com/patent/US3820162A/en] $\endgroup$
    – S. McGrew
    Commented Sep 28, 2019 at 17:01


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