AIAA-95-1 062 the Suitport's Progress M. Cohen NASA Ames Research
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NASA-TM-111836 /t/ .' I I AIAA-95-1 062 The Suitport's Progress M. Cohen NASA Ames Research Center Moffett Field, CA Life Sciences and Space Medicine Conference April 3-5, 1995 / Houston, TX For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics 370 L'Enfant Promenade, SOW., Washington, D.C. 20024 AIAA-95-106; THE SUITPORT'S PROGRESS Marc M. Cohen* NASA-Ames Research Center Moffett Field, California Abstract Origins of the Suitport NASA-Ames Research Center developed The Suitport Extravehicular Access Facility the Suitport as an advanced space suit originated during the early phase of the airlock to support a Space Station suit, Space Station Advanced Development based on the AX-5 hard suit. Several third Program. It grew from a recognition that the parties proposed their own variations the construction and operation of Space Station Suitport on the moon and Mars. The Freedom (SSF) would require several Suitport recently found its first practical use thousand hours of EVA time (This finding as a terrestrial application in the NASA- has not changed much for the new design Ames Hazmat vehicle for the clean-up of for "Space Station Alpha." To make the best hazardous and toxic materials. In the Hazmat use of SSF crew time, it will become application, the Suitport offers substantial necessary to make the entire space suit improvements over conventional hazard donning and doffing, and airlock suits, by eliminating the necessicty to egress/ingress as safe, rapid, and efficient decontaminate before doffing the suit. as possible. Definitions The Space Shuttle EMU suit and airlock AX-5 Ames Experimental Suit 5 systems pose several potential CCPS Command/Control Pressure Suit disadvantages for frequent and routine EMU Extra-Vehicular Mobility Unit Space Station operations. The shuttle EVA Extra-Vehicular Activity airlock would not be large enough to ft 3 cubic feet accommodate two crew members suiting up Hazmat Hazardous materials into the hard, rear-entry AX-5 as it is fairly IVA Intra-Vehicular Activity tight even for the soft, pull-on EMUs. m 3 cubic meters However, the solution for Space Station was clearly not to build a bigger airlock because PLSS Portable Life Support System that would only increase atmosphere loss, psi pounds per square inch pump-down time, power, and cooling. SSF Space Station Freedom STS Space Transportation System All Space Shuttle EMU suit maintenance (Space Shuttle) occurs on the ground. Perhaps the most Suitport An airlock design to allow rapid important departure from this practice is, that donning & doffing of a protective the SSF suit must be maintainable, suit through a rear hatch. resizable, and repairable on orbit. This V.E.R. Volumetric Efficiency Ratio requirement suggested a radical departure from the traditional "dumb can" airlock design. It would involve automated servicing, and the ability to conserve *Architect, Advanced Projects Branch, atmosphere and other consumables much Space Projects Division, Senior Member AIAA more efficiently than the EMU airlock system. Thus the problem definition for the Suitport involved considering strategies for Copyright © 1995 by the American Institute of Aeronautics and Astronautics, Inc. No conserving consumables. Secondarily, it involved additional considerations such as copyright is asserted in the United States under Title 17, U.S. Code. The U.S. potential for protection against outside contaminants. Government has a royalty-free license to exercise all rights under the copyright Strategies for AtmosDhere Loss - The loss claimed herein for government purposes. of atmosphere varies directly with the All other rights are reserved to the copyright volume of the airlock. There are two owner. strategies to handle this situation: to "sacrificetheatmosphere"fromtheairlock The Suitport seeks to resolve the dilemma of to vacuumandto saveon power,cooling pumpdown time versus power by saving on andcrewtimeORto "savetheatmosphere" all the variables. By reducing the pump andpaythecostinpower,cooling,time,and down volume by more than two orders of complexity.Undereitherstrategy,reducing magnitude, it saves substantially on power, the totalvolumeof the airlockatmosphere cooling, and pump down time. The volume contributesto savingson all the metrics, of air in the interstitial volume between the exceptperhapscomplexity.Theuseofvoid space suit hatch and the airlock hatch is so fillers can be a fairly inexpensiveway to small that it may become economical to reducethis pumpdownvolume Figure1 sacrifice it to vacuum without pumping it illustrates dramatically the inverse down. Table 1 shows a comparison of the relationshipbetweenelectricalpowerfor Suitport pump down volume against six airlockpumpdownandthetimerequiredto other candidate airlock designs. These pumpdownvariousairlockvolumesfrom1 metrics show the potential order of atmosphereintoastoragetankona 10to 1 magnitude improvements that the Suitport compressionratio.Thisgraphshowsthatto promises. 2 achieverapidpumpdownunderthe save the atmosphere approach for a large airlock Table 1. EVA Access Facility demands very large amounts of electrical Volumetric Efficiency Ratio (V.E.R.) power, compared to the then-anticipated SSF total capacity of 50 to 75 kW. For Suited Crew Volume = 0.22m 3 (8.0 ft3) example, to pump down a 300 ft3 airlock in for one crew member ten minutes would require about 25kW continuous during that period. It may also be Suited Crew Volume V.E.R. = possible to pump the airlock down to the Pump-Down Volume SSF cabin atmosphere. However, pumping to the cabin would pose potential hazards of AIRLOCK PUMP V.E.R. introducing external contamination into the OPTION DOWN station proper, because it would depend VOLUME upon filtration rather than upon physical m 3 (ft3) separation. A STS-Type .062 Comparative Analysis - The first step was to Airlock 3.63 (129) prepare comparative analyses of candidate (enlarged) , .087 airlock systems to support AX-5 suit STS Existing 2.59 (92) Airlock operations. 1 The four airlock design .120 concepts that received the closest attention B Transit 1.86 (66) were: Aidock C Suitport w/ .014 (0.5) 16.0 A. An STS-Type Airlock enlarged to PLSS Seal accommodate the rigid AX-5 suit. C' Suitport No 2.28 (81) .098 B. A Transit Airlock, as an adaptation of PLSS Seal the STS airlock reduced by removing D Crewlock w/ .056 (2.0) 4.00 the suit servicing and don/doffing and Void Filler placing it inside the station. D' Crewlock No 1.49 (53) .150 C. The Suitport EVA Access Facility in Void Filler which the AX-5 rear entry disconnect mounts to the airlock hatch, creating an Strategies to Control Contamination - Two extremely small pump down volume in strategies exist for donning and doffing a the interstitial space between the suit rear hatch and the airlock hatch. protective suit without exposing the wearer to external contamination. These two D. The Crewlock developed by William strategies are "decontaminate before Haynes of the Aerospace Corp., which doffing" and "exit to a safe atmosphere." In uses conformal void fillers to minimize the decontaminate before doffing the pump down volume around the approach, decontamination must occur while space-suited crew member. the crew member is still in the suit, before opening its protective envelope. Current protective suits for hazardous material cleanupfollowthisapproach,as wouldthe that support productivity and safety current NASA Space Shuttle EMU suit in EVA operations, (should decontamination become (2) to develop advanced EVA necessary).Intheexit to a safe atmosphere airlock and servicing support system approach, the crew member can exit the suit mock-ups for high-pressure hard to a safe environment without space suits such as the AX-5 .... decontaminating first. The Suitport takes the exit to a safe atmosphere approach to an Cawthorn described "expected products": integrated systems level for both space operations and terrestrial applications. (1) an advanced EVA access facility combined airlock and servicing Figure 2 illustrates a storyboard showing the systems, operational scenario of how a crew member (2) an EVA suit servicing, donning would prepare the suit before routine and doffing, egress and ingress operations, don (enter) the suit, separate computer simulation .... the suit from the Suitport and egress the station airlock. The Suitport offers a This advanced airlock initiative came to a halt substantial improvement over the when NASA eliminated the Space Station conventional airlock technology. The crew suit from the budget. Instead, station member enters the rear-entry hatch of the planners proposed to stage EVAs out of the space suit through the Suitport. Closing the shuttle airlock to build the station, a scheme nesting suit rear hatch and Suitport hatch that proved inadequate and unworkable. together, it is necessary only to pump down Since that time, a there is a space station or vent off the very small amount of air in the airlock to support the space shuttle-type interstitial volume between the two hatches, EMU, but not an advanced suit. Without an less than .035 m 3 (1 ft3). Thus, the Suitport advanced station suit, there was no demand promises substantial savings in spacecraft for an advanced Space Station airlock. atmosphere loss, crew time, electrical power, and pump cooling. The way the Suitport Third P6rty Adaptations seals the suit to the habitable "shirtsleeve" Since the Space Station Advanced atmosphere offers the additional advantages Development Program, a number of