Answers_3.pdf

QUESTION

I do have one additional question out of curiosity, the original specification in 3.2.1.4 required a transition of 12 hours from ambient, i.e. +70F to ‐65F with the 60,000 lb. static load in 12 hours. Among the answers provided, i.e. No.12, you state this to currently be anywhere between 72 and 84 hours depending upon the outdoor ambient conditions. It would appear that you are asking for something in the order of 6‐7X the current capacity in cooling.

Regarding the question:

We dug up some historical chamber data from 2003:

June 24 2003:

+90F to ‐52F in ~30 hours (with an 8 hour hold at +40F)

9,500 lb steel test item www.wunderground.com historical weather data in Yuma (MCAS):

Mean Temp = 83F

Max Temp = 96F

Min Temp = 70F

Avg RH = 29

Max RH = 62

Min RH = 15

October 25, 2003

+68F to ‐32F in ~6 hours

24 hour hold at ‐32F

‐32F to ‐52F in ~2 hours

9,500 lb steel test item www.wunderground.com historical weather data in Yuma (MCAS):

10/25/2003

Mean Temp = 80F

Max Temp = 95F

Min Temp = 64F

Avg RH = 29

Max RH = 93

Min RH = 6

10/26/2003

Mean Temp = 78F

Max Temp = 88F

Min Temp = 69F

Avg RH = 11

Max RH = 23

Min RH = 6

From the Specification:

3.2.1.4. The SMEE shall be programmable to transition the WFC chamber temperature from +70°F to either temperature extreme (‐65°F or +165°F) at a rate not to exceed 5°F per minute. The time for static chamber temperature to change from +70°F to ‐65°F should not exceed 12 hours. The time for static chamber temperature to change from +70°F to +165°F should not exceed 8 hours.

The "... shall be programmable ... rate not to exceed 5°F per minute." Requirement is a hard "shall".

The " ...time for static chamber temperature to change from +70°F to ‐65°F should not exceed 12 hours " is an aggressive "should". This statement reflects what would be desired, but is unrealistic taking into account what is needed to perform our test mission.

Propose the following change to 3.2.1.4:

3.2.1.4. The SMEE shall be programmable to transition the WFC chamber temperature from +70°F to either temperature extreme (‐65°F or +165°F) at a rate not to exceed 5°F per minute.

Equipment sizing and calculations for static chamber temperature to change from +100°F to ‐65°F should not be expected to exceed 48 hours.

under the conditions described in 3.1.3 (60,000 static load in the chamber).

Equipment sizing and calculations for static chamber temperature to change from +50°F to +165°F should not be expected to exceed 24 hours.

under the conditions described in 3.1.3 (60,000 static load in the chamber) given the available site power. Performance Requirement 3.2.1.1 shall be met regardless.