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NASA International Space Station De-crewing and Re-crewing Plan SSP 50715

Status Report From: Johnson Space Center
Posted: Tuesday, October 31, 2006

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Directive 008586 Attachment A
SSP 50715 Baseline
INTERNATIONAL SPACE STATION DE-CREWING AND RE-CREWING PLAN

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The purpose of this document is to define the program process requirements, milestones and general station configuration requirements should it become necessary to de-crew the International Space Station (ISS) and later re-crew and return to normal operations.

The contents of this document are intended to be consistent with the tasks and products to be prepared by the ISS Program participants as defined in SSP 50200-01, Station Program Implementation Plan, Volume 1: Station Program Management Plan, and SSP 50200-02, Station Program Implementation Plan, Volume 2: Program and Manifesting. This document is under the control of the Space Station Control Board (SSCB).

1.0 INTRODUCTION

De-crewing of the International Space Station (ISS) could occur as a result of several scenarios including; major system failure (unrecoverable or resulting in emergency condition), medical emergency or related problem, or insufficient consumables. Each of these scenarios initiates a decision making process where the de-crewing event will be classified as "planned" or "unplanned" for discussion purposes in this document. The approach to de-crewing is directly related to the scenario classification and additional definitions provided herein.

Unplanned de-crewing takes on 2 sub-classifications defined here as emergency and contingency:

A. An emergency de-crewing is defined as a scenario requiring immediate departure of the ISS crew. The preparation time could be as little as a few (30) minutes with little ability to configure the station systems or optimize undocking opportunities. Responses to these cases are defined by the procedures in SSP 50505-2 Basic Provisions on Crew Actions in Case of Fire on the ISS, SSP 50506-2 Basic Guidelines for Crew Activities During ISS Depressurization, All Increments/Flights and SSP 50653 Basic Provisions on Crew Actions in the Event of a Toxic Release on the ISS, All Increments/Flights, which focus on fire, cabin pressure loss, and toxic release events.

B. A contingency de-crewing is defined as a scenario allowing up to 72 hours before a crew's departure. This scenario allows enough time to execute some or all of the system configurations outlined in this document but no time is available for special payload configuration needs or other system configuration "optimization" activity.

Planned de-crewing will be defined as a scenario offering greater than 72 hours before the crew needs to depart the ISS. This potentially allows for other tasks to be accomplished beyond the system configurations outlined in this document. As a result the crew can configure the station systems for optimal operation during the de-crewed phase and coordinate optimal undocking opportunities. This period includes time for crew sleep and rest.

Section 3 defines the de-crewing decision process and requirements. The decision making authorities are specifically defined since timely decisions during this process may be critical.

Section 4 outlines the baseline system configuration desired for de-crewing which also supports the ability to successfully facilitate in re-crewing. Additional steps may also be required to regain fault tolerance for ISS habitation. Deviations from the baseline may be necessary due to the ISS configuration at the time and will be appropriately analyzed for necessary changes and any required actions to be taken.

The ISS Program's top priority is to maintain ISS and crew safety and survival (reference SSP 50261-01, Generic Groundrules, Requirements, and Constraints Part 1: Strategic and Tactical Planning, Section 4.2.1A). As part of the nominal process to plan a safe and sustainable ISS configuration without a crew, the ISS and system configurations will be assessed. As time permits, depending on the scenario, a partial to full system configuration will be achieved. The risk and safety posture will be evaluated and appropriate actions taken by the ISS Program to maintain safety of the ISS and the returning crew.

Section 5 outlines the decision making process for re-crewing the ISS. This area is defined in general terms since the reasons for departure directly affect the decisions for return. The process does address the major elements of assuring crew safety upon return to the ISS and ability to restore system integrity. Ultimately the plans for return to ISS should mitigate the risk of de-crewing again but the processes must also recognize the potential risks associated with crew return to orbit.

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