Posts: 180
From: Los Angeles, CA, USA
Registered: Apr 2019

posted 07-24-2019 08:46 PM            

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Does anyone know what the nominal temperature was supposed to be inside of the Mercury spacecraft and how was that temperature maintained?

And when that nominal temperature was first established from an engineerring design standpoint did that take into account the heat that would be given off by the spacecraft's instrumentation?

Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010

posted 07-29-2019 03:42 AM               

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It was suppose to be room temp, the same system that provided suit cooling.

And yes, it took into account the heat produced by the avionics.

Posts: 971
From: Perth, Western Australia
Registered: Apr 2015

posted 07-31-2019 06:31 AM               

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For Mercury-Atlas 8 the average cabin temperature indicated 90 to 105 degrees F. For Mercury-Atlas 9 the cabin temperature cycled between 90 and 95 degrees F.

The suit temp was recorded at a lower temp, however the ECS system underwent many modifications between missions, and the cabin temp on earlier missions were measured from different positions resulting in different results.

The design had an expected range of 60 to 90 degrees F.

The details can be found within this document.Figure C-2 indicates cabin temp variation during a mission.

Posts: 219
From: Phoenix, AZ
Registered: Feb 2007

Posts: 180
From: Los Angeles, CA, USA
Registered: Apr 2019

posted 08-02-2019 12:46 AM            

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Thank you for these excellent responses. It would be interesting to know what the cabin temperature was inside of Freedom 7. Given that it was a short flight, one might expect the cabin temperature to be perhaps the lowest of any of the missions.

This brings up the question of the Mercury pressure suit and what the temperature was inside the suit for various missions.

The abdomen oxygen inlet hose as I understand it was suppose to provide ventilation inside the suit. And the oxygen hose that directly connected into the helmet was for breathing. Secondarily however, I imagine that the oxygen flow inside the helmet provided cooling as well. But during each orbital flight, the astronauts had their visors open, therefore exposing them to the heat of the cabin. So I am wondering if when their visors were open if oxygen was still being feed into their helmets.

And most surprisingly, the astronauts were actually wearing long johns — thermal underwear inside the suit which was sure to raise their body temperature. One might think they would have come up with something much thinner to wear or simply allow the astronauts be close to nude. Although I understand that part of the reason for the underwear was to absorb perspiration.

Posts: 971
From: Perth, Western Australia
Registered: Apr 2015

posted 08-02-2019 01:36 AM               

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The Mercury astronauts suit temperature is a topic that many of the astronauts have described having issues with during their respective flights. Schirra describes this in his oral history project interview.

The valve used to control the suit temperature required fine adjustments and was reported to be prone to over-correct. The suit cooling circuit was also modified between some missions. The system was capable of providing adequate cooling.

Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010