Report, Procedures Development and Checklist

To keep track of everything, I'm writing reports for myself, and developing the appropriate checklists. Below, a report on the first pressure-integrity tests of the prototype pressure suit. It may well be that this suit never flies, that it's simply a 'proof of concept' garment that will teach me all I need to know to build the next suit for actual flight. Below the report, the current donning procedure checklist.

PROJECT ALPHA--Expedition Equipment Test Report 1
REPORT TYPE: Equipment test / Full-pressure garment
CONCEPT ___ BUILDING ___ GROUND TEST __X__ FLIGHT TEST ____
REPORT STATUS: Draft _X_ Final ___
TITLE: FULL-PRESSURE SUIT MK I TESTS, 25 and 26 NOV 2009
AUTHOR: CM Smith
PRESENT DURING TESTS: CM Smith, AR Perri (assistant)
DATE OF FILE INITIATION: 28 November 2009
DATE OF FINAL FILE SAVE: 28 November 2009

REPORT OBJECTIVES:

Performance report on first pressurization test of Full-Pressure Suit Mark I (FPSMK-I), using common air (c. 20% oxygen, c.80% nitrogen) as breathing and suit-inflation gas. The Full-Pressure Suit tested here was built between 26 Oct 2008 and 22 Nov 2009 with no intermediate pressure test. The currently-reported tests were conducted to investigate (a) pressure-bladder garment integrity, (b) viability of the SCUBA demand regulator to release breathing gas to the occupant at each inhalation and (c) viability of the pressure helmet to ‘dump’ exhaled gas at each exhalation.

OVERVIEW of RESULTS:

While the pressure suit, inflated in two tests, appeared to maintain what appeared (this test lacked a pressure gauge to accurately monitor suit pressure) to be a physiologically-endurable pressure (estimated at 6PSI above ambient pressure of c.14.7PSI), and the breathing gas demand regulator worked well enough in these tests, it was determined that having the lower (below-neck) part of the pressure garment intimately connected to the pressure helmet resulted in the pressure-helmet’s overpressure relief valve being activated at the time of suit inflation to a suitable pressure for life-support in ambient near-vacuum pressures. When this problem was identified, a neck-sealing ring was added to the pressure garment to somewhat divorce the pressure helmet from the body of the pressure garment. This radically improved suit performance, allowing the SCUBA demand regulator to activate at each inhalation and the pressure helmet’s overpressure valve to activate at each exhalation. However, when the pressurized suit occupant bent his arms, or otherwise moved his body, pressure-suit pressurization gas was forced between the neck ring, over-pressurizing the pressure helmet and thereby activating the pressure helmet’s overpressure relief valve; in a low-pressure (e.g. high-altitude) environment this would be unacceptable, as it would quickly reduce pressure in the pressure suit, resulting in decompression sickness for the operator.

There are two options considered available to date:
build the suit to be entirely full-pressure, so that no matter what movement the occupant makes, the overpressure is ‘dumped’ AND simultaneously the suit is repressuirized, via an aneroid device, to maintain a physiologically-suitable pressure (e.g. over 5PSIG pressure and over 5PPO2 pressure); this could be accomplished by building a ‘constant-volume’ pressure bladder garment.
build the suit to be divorced-pressure, so that the lower (below-neck) pressure is maintained regardless of the pressure-helmet pressure, allowing the inhalations and exhalations of the occupant to be restricted--in terms or pressure--to be restricted to the pressure helmet; while this may be possible, it would always be possible that an over-exertion on the lower suit would force suit-pressurization gas beyond the neck ring, activating the pressure helmet’s overpressure relief valve, thereby subjecting the suit occupant to decompression sickness.

OVERALL LESSONS

The main technical challenges of home-building a full-pressure suit suitable for high-altitude balloon aviation are not in the ‘software’, that is, in the ability of the pressure garment to hold the pressure: even this heavily-modified ‘off the rack’ SCUBA diving dry suit (and, critically, its airtight zipper) easily contained the required pressure (this was not measured in these tests, as there was no suit pressure gauge fitted to the suit; but it did appear that a high pressure was maintained in the suit during the second test, though this will have to be verified and quantified in a future test--having said this, the pressure maintained seemed to be, on an experiential level, suitable for high-altitude/low-atmospheric-pressure conditions). Rather, the main technical challenges lie in the hardware that (a) admits breathing gas and (b) exhausts exhaled gas.

RE point 1a above (regarding the admission of breathing gas), the SCUBA regulator used to admit breathing gas to the suit functioned, even though the regulator was physically stationed several feet away from the pressure helmet itself (via a hose). It has yet to be determined whether or not a standard SCUBA demand regulator will work in a near-vacuum; if not, there are at least three possible solutions: (a) building a full-pressure housing around the SCUBA demand regulator so that it would work at higher altitudes / lower (near-vacuum) pressures, (b) using a demand regulator that is designed to deliver breathing gas in near- or full-vacuum conditions and (c) building the demand (breathing gas intake) regulator INTO (inside) the pressure helmet. Other solutions may exist, but I have not considered them.

RE point 1b above (regarding the exhalation of breathed gas), the pressure helmet’s exhaust valve continuously dumped suit inflation gas when the pressure garment was NOT divorced from the pressure helmet’s above-neck area, probably because the suit pressure was high enough to initiate the exhaust valve’s ‘overpressure’ design element.

When the pressure helmet was (largely) divorced from the pressure garment via a nearly-airtight neck bladder (in the 26 Nov 2009 test), the helmet’s intake valve worked better, actuating the SCUBA regulator to admit breathing gas to the helmet at each inhalation; in the same way, when the pressure helmet was (largely) divorced from the pressure garment via a nearly-airtight neck bladder, the helmet’s ‘dump’ valve worked better at each exhalation, actuating the dump (overpressure) valve ONLY when (a) the occupant exhaled and /or (b) when the occupant bent/flexed the pressure bladder garment, forcing gas through the neck bladder and over-pressuring the pressure helmet. Point 4b can perhaps be addressed by (a) a better neck bladder seal, preventing pressure garment gas admission into the pressure helmet, and / or (b) construction of / incorporation of ‘constant-pressure’ design elements into the pressure bladder garment, eliminating the issue of bodily movement (below the helmet neck bladder) over-pressuring the helmet and thereby actuating the pressure-helmet’s overpressure relief valve system.

RECOMMENDATIONS

Test possibility of breathing through an oral/nasal mask, inside the pressure helmet, to ease inhalation effort and to more easily exhaust exhaled gas.

REPORT DERIVATIVES

FULL-PRESSURE SUIT MARK I (FPS-MKI) DONNING PROCEDURE
(use this checklist ONLY for donning FPS-MKI, using standard air as suit pressurization / breathing gas; if using pure oxygen or other breathing gas / suit pressurization gasses, see other Donning Procedures)

1. Don Insulation / Comfort Coverall Garment (ICCG)
2. Don Comfort Liner Socks (CLS)
3. Don Comfort Liner Gloves (CLG) (if any)
4. Body Into Pressure Garment (PBG) Body
5. Head Through Pressure Garment Neck Ring
a. ensure secure neck seal
6. Don Gloves
a. pressure bladder gloves / ensure no wrinkles
b. pressure bladder glove backup / ensure no wrinkles
c. attach wrist clamps (L, R), screwing to only ____ torque
7. Don Communications Carrier Helmet (CCH)
8. Don Voice Helmet Recording Device ((a) switch ON (b) visual (c) insert in CCH)
9. Ensure Suit Pressurization Tank is Turned On and Indicates >= 3,000PSI
10. Connect Low Pressure Hose (suit inflation + inflator valve: 1 second test)
11. Don Pressure Restraint / Helmet Holdback Harness
a. waist belt secure / helmet anterior link connection
b. chest belt secure / helmet posterior link connection
12. Don Pressure Helmet (PH); ensure ‘easy’ bayonet slide connection is unimpeded
13. Low Pressure Hose Test (1-second)
14. Assistant holds SPG monitor in view of suit occupant and assistant
15. Close Pressure Helmet Visor; assistant monitors Suit Pressure Gauge (SPG)
16. Pre-Pressurize PBG with 5-second manual inflation
a. if Pre-Pressurization fails after 5 seconds (monitor SPG), OPEN VISOR
b. if Pre-Pressurization succeeds (SPG indicating rising PSI), continue suit pressurization to 19.7PSI (below)
17. Pilot Inhale / Exhale Test (10 seconds)
18. Pilot Ensures Pressure Garment pressure at 19.7 PSI / 5.7 PSIG, via SPG
19. Check Suit Tank Pressure Gauge (be sure >2,500 PSI)
20 Check PRG Integrity by listening for leaks at:
a. back zipper
b. wrists
c. neck seal
d. boots
21. Commence suit test objectives or move to step #22
22. Move Pilot to Balloon Capsule