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Appendix C Phase ~ Mir Program INTRODUCTION Phase 1 of the International Space Station (ISS) was a National Aeronautics and Space Administration (NASA) program encompassing 11 Space Shuttle flights and one Soyuz flight over a four-year period from February 1994 to these questions in a rigorous sense. The following answers are based on primarily our observations during the Phase 1 program, by both crewmembers and ground personnel. Efforts continue to increase our detailed knowledge of the history of systems that will be flown on ISS. June 1998. During Phase 1, seven U. S. astronauts spent 31 months aboard Mir working with their cosmonaut crew mates supporting Mir operations and conducting scientific 1. What type MIR equipment has the greatest maintenance expenments. Existing assets pnmar~ly the Space Shuttle ' ' requirement (ground on-orbitJ? the Russian Soyuz, and the Russian space station Mir, were used. In a review of the lessons learned from the Phase 1 Mir program, the committee found some similarities and many differences in the approaches taken by the Russians for the Mir and by NASA for the ISS. One of the primary short- comings on Mir was the limited availability of communica- tions with the ground. The Mir experience reaffirms the committee's opinion that the ISS will require 100 percent communications availability through the tracking and data relay satellite system. The two major sources of information pertaining to the Phase 1 Mir program were the NASA's lessons-learned documentation (NASA, 1998) and responses to questions from the committee about the Phase 1 Mir experience in the areas of maintenance and repair, extravehicular activity, station operations, and crew timelines. The questions and answers are reprinted in this appendix. The answers were prepared by the NASA Phase 1 ground support personnel with management review and comments. QUESTIONS ABOUT THE PHASE I MIR EXPERIENCE Introductory Remark We [NASA] do not have direct information to answer iThe questions and answers have been printed verbatim and have not been edited. 36 Maintenance and Repair Maintenance takes several forms (preventive and correc- tive) and can have different levels of impact to station opera- tions. For example, the Elektron oxygen generators are "fussy" in the sense that they often require attention from the crew to purge air bubbles from the water supply line or to respond to pressure anomalies that may temporarily take the unit offline. These are due to the fact that the Elektron generates hydrogen as well as oxygen and safety systems shut the unit down as the conservative response to preclude accumulation of hydrogen in the vehicle. In addition, the Elektron supply and overboard vent lines must be cleaned periodically. On one occasion, cleaning the vent required EVA operations on two different EVAs, but it was possible to schedule the tasks with other EVA tasks to reduce the time impact. The Elektron system to be flown on ISS will be similar to the Mir units. Another system that required a significant amount of maintenance is the gyrodine momentum storage system. The externally mounted system on Kv ant 2 exhibited a rapid failure rate and did not perform as well as was hoped, and therefore was not maintained. Instead, internally mounted gyrodines were added in flight. These have functioned satisfactorily and comprise the system which is currently operating. The failure rate of the gyrodines has been signifi- cant, but many of those failures were induced by other factors. For example, the units use a magnetic suspension system to reduce wear and drag internally and a normal
APPENDIX C shutdown maintains the suspension until the rotor has spun down. However, on quite a few occasions during the latter part of the Phase 1 Program, unexpected losses of electrical power resulted in rapid stopping of the units, causing with premature termination of the magnetic suspension. This resulted in predictable damage to some parts of the units. Some spares for these parts were kept on board for this scenario, and the crew was very proficient in performing the task. However, the spares were eventually depleted. The Solid Fuel Oxygen Generator, or SFOG is another system with maintenance requirements characteristic of the Russian design approach.. This is a very simple unit with only two moving parts: an electric fan and a spring-powered striker assembly used to trigger the initiator pellet for the SFOG cartridge. While we are unaware of any failures of the fan, it is a common type that is widely used on the Mir and several spares are usually on board. The striker assembly is subject to wear with high use, which can result in the need to make several attempts to initiate the cartridge reaction. The striker assembly is easily and regularly changed out. The Mir' s roll-axis thrusters are located on the end of the Sofora truss boom in a self-contained unit. This unit has been replaced twice over the life of the Mir when its propel- lant was exhausted. In neither case was a failure of the hard- ware involved and, despite U.S. reservations concerning the changeout task's feasibility, both changeouts were com- pleted without incident. However, the task is lengthy and complex, involving multiple EVA's (three or more) and the use of a special Progress vehicle to carry and position the replacement propellant unit. Another task that required a great deal of ground attention and crew time was the identi- fication and repair of cooling system leaks. For various rea- sons the Mir had a relatively high incidence of condensate present on the walls of some modules. This, combined with an unfortunate choice of metals for grounding straps, led to dissimilar metals corrosion that caused perforation of the coolant loop tubing in a number of places. Once the problem was identified, locating the sources of the leaks rapidly esca- lated to being the major crew task for several months during the Spring of 1997. Concerns regarding habitability and exercise also resulted from of the leakage of the ethylene glycol coolant into the cabin atmosphere. There was no direct health threat due to this leakage, but it was a major irritant to the crew and limited exercise opportunities. The inability to exercise can become a constraint to keeping the crew on board, but the problem was resolved without evacu- ation. Design improvements have been made to ISS to better control the humidity level and prevent dissimilar corrosion should it occur. As a third corrective action, the coolant in use on ISS is a non-toxic, non-irritating material. 2. What type of Mir equipment has the highest replace ment rate ? Exact data not available, but the following items have 37 been observed. They are listed in no particular order: · filters and other consumables · batteries · gyrodines . . · avlomcs boxes · SFOG strikers 3. How have actualfailure rates of equipment on Mir com- pared with the earlier projections? We do not have sufficient data to be quantitative on this, but the following observation is offered. Mir was designed to be maintained, operated, and have some research per- formed by a crew of two, with the addition of a third crewmember to be dedicated to research. This objective has basically been met, although in recent years very long hours have been required on many occasions. The condition of the station has led to the need for higher than usual effort to restore normal functionality to on-board systems. This activity reached a peak in 1997, and a major push by the crew resulted in the maintenance demands and overall station reliability being much improved from late 97 at least through mid 98 when the last U.S. crew departed the station. We have little data for the period after the U.S. crew left Mir. 4. What types offailures were encountered (design flaws, environmental, usage, randomJ? All of the above, as would be expected with a program of this length. 5. What was the planned Mir sparing philosophy and how did it compare with actual? The planned sparing philosophy was to "replace as speci- fled in design documents," which means replacing each item at the end of its predicted reliable lifetime. In reality, as experience was accumulated and pressure on spares avail- ability grew, the philosophy changed to operate non-critical hardware until failure. This is the norm in the U.S. aero- space industry and is the plan for the U.S. segment of ISS (with careful definition of the term "failure") as it makes an enormous difference in the spares population required and resulting cost. The Russian program is particularly well suited to this approach since in addition to having highly maintainable hardware on orbit, the Progress cargo vehicle manifest can be changed at a relatively late date to respond to late-breaking requirements. In addition, the Russian philosophy is to retain critical parts on orbit, even when they have shown some degradation, rather than to discard them, since a deorbited Progress is not recoverable and failed hard- ware returned in it is lost. Therefore, when a computer has a partial failure, for example, it is replaced as soon as possible with a new unit but the failed unit is retained against its
38 ENGINEERING CHALLENGES TO THE LONG-TERM OPERATION OF THE INTERNATIONAL SPACE STATION possible use as a temporary spare. Also, the predicted fail ure rates of some items such as fans was overstated to the point where an excessive number was kept on board. This was eventually corrected, but since the process for maintain ing on-board inventory was evolving, it took some time to determine. 6. If you were starting over with Mir, what changes would you make to reduce maintenance cost and time? From a maintenance and logistics perspective, NASA does not have sufficient knowledge to say much at this time. Some improvement in demand for consumables and other evolutionary items would be good, and experience has reinforced the importance of tracking the maintenance and logistics demand rather than letting it get behind. Positive examples from the Mir include the high degree of on-orbit maintainability of the hardware, permitting the resupply of smaller components rather than larger units, the large proportion of internal hardware to be maintained rather than extensive EVA requirements, and a highly responsive logistics resupply vehicle (Progress) capable of carrying replacement items, both IVA and EVA, on relatively short notice. Another key element is an emphasis on skills-based training for the crew so that they can accomplish any main tenance task that arises while the crew is on-orbit. Negative examples from Mir include the necessity to per form certain types of repair operations, such as cutting of materials, on-orbit. The increase in atmospheric particulates (such as dust) which resulted from some of these activities is undesirable. Likewise, the procedures for repairing the coolant leaks were ineffective in preventing further leakage of the coolant into the atmosphere. Finally, the lack of a descent vehicle capability for returning failed hardware drives replacement unit costs and prevents failure analysis for design improvements. 7. What has proven to be the most important characteristic of the MIR internal systems, (robustness, reliability, hours are: redundancy) ? All three apply. It is difficult to determine what could be named the single most important characteristic of a Mir sys tem. Very many of Mir' s internal systems were brand new, and this may have been of utmost importance. Mir software was developed and modified on an "as-needed" basis, dur ing the entire life span of the station. The same philosophy (change with changing environment, think on your feet, be flexible, be adaptable and creative) was applied to all internal systems of Mir and became the core philosophy enabling the station to fly, albeit with some difficulties, almost twice as long than was originally predicted. Extravehicular Activity 1. What part of the MIR program has the highest EVA requirement? Of over 350 total Mir EVA hours, three categories of external work are apparent: Assembly- 52% Science - 24% Maintenance/Contingencies - 25% 2. How many "preplanned EVA" hours does the MIR pro- gram plan annually? From 1987-1998, an overall average of about 20 hours of EVA assembly and science were planned each year. In more recent years (1995-1998), the rate of Mir EVA increased to seven to ten EVAs per year (39-55 hours per year). 3. How many "unplanned EVA hours" have occurred each year, for the first three years, and for the most recent three years, of MIR operation ? Over the life of Mir, 1/4 of the EVA work was "un- planned" as noted in the answer to question one. In the first three years, (1986-1989), only one EVA of 3.5 hour dura- tion was unplanned (to free debris preventing docking between Kvantl and Mir modules). In the last three years (1997-1998), a total of 30 hours of unplanned EVA was expended (1 hour for antenna anomalies in 1996, 24 hours for Spektr repairs in 1997-1998, 5 hours in 1997-1998 for the Kvant2 hatch). 4. What have been the actual EVA hours each year since the start of the MIR operational phase ? Based on available data, the approximate annual Mir EVA 1986 - 0 1987 - 9 1988- 19.5 1989 - 0 1990- 32 1991 - 53 1992 - 24.5 1993 - 24 1994- 11 1995 - 39 1996 - 46 1997 - 77 1998 - 36 1999 - 0
APPENDIX C 5. How do the estimates of EVA time compare with actual time spent EVA ? From first hand experience with the Mir-23 and Mir-24 EVAs, the typical Mir EVA was planned for a 5 hour 30 minute duration. The actual duration often increased by about 10% or 30 minutes. 6. How much time did you put in the on-orbit timeline for a crewmember's training and preparation to perform an EVA ? Based on detailed study and experience with Mir-23 and Mir-24, pre-EVA crew time (including on-orbit training) ranged from 9-54 hours, but was normally about 22 hours. Response to unplanned contingencies requires considerably more preparation than those tasks trained and executed per pre-flight plans. The second or third EVA in a related series requires much less overhead than the first. 7. What is the failure rate for the MIR space suit assembly? Has it improved over time? Mir is normally provisioned with three Orlan suits and numerous spare parts. Of the 76 Mir EVA sorties, two ended early due to O2 regulator and cooling failures and three were degraded but not stopped by cooling and humidity removal problems. Only one of the EVAs since 1997 has required the use of the spare suit (fan problem). The Orlan suit has evolved since Russia's manned lunar mission era with design issues being addressed along the way. The same Orlan M design that has been used for Mir EVAs since 1997 will also be used on ISS. Though a specific failure rate is difficult to program? compute with the limited data in hand, no show-stopping hardware failures have occurred in recent years. 8. What suit/life support system enhancements have been required ? Russian initiated improvements from the Orlan DMA to the Orlan M include: Increased suit service life from 10 to 12 sorties More volume in upper torso for larger crew Better and more capable humidity removal More mobility in lower legs and arms via new bearings New overheard window/visor and brighter helmet lights to improve visibility Easier on-orbit arm/leg resizing - Elimination of low pressure mode of suit pressure regulator 39 Joint agreements have resulted in the following: Option for U.S. safety tether attachment Option for U.S. rigidizable equipment/body restraint tether Common foot restraint platform to hold both EMU and Orlan boots Option for U.S. crew preference items (moleskin, underwear, comfort gloves) Future attachment of Orlan specific self rescue jet pack (SAFER) 9. If you had it to do over, what changes would you make to the EVA system (suit/LSS)? From a U.S. perspective, NASA would: Enhance suit size range to fit more large and small crewmembers. Improve arm mobility and glove dexterity. Correct glove and boot thermal comfort issues. Make the umbilical easier to mate/demate when pressurized. Never design an EVA hatch to open outward. Implement a larger GCTC water tank for more inte- grated mockup layout. Improve mockup fidelity. Increase the limited number of Russian EVA ground personnel. Get one to two of them to reside in Houston on a permanent/rotating basis. Improved access to overseas facilities, hardware, procedures, and drawings. 10. What is the estimated cost of an EVA hour in the Mir NASA does not have sufficient data to provide an estimate. 11. What were some of the cosmonauts' tasks that re- quired EVA ? Deployment and retrieval of numerous small and mid- sized science experiments Construction of truss experiments Transport, installation, and deployment of solar arrays and attitude control thruster packages Routing, restraint, and connection of cables Backup manual release of a jammed antenna and solar array Transport of crew and large objects via Strela cargo crane External inspections after MMOD events Still and video camera photography
40 ENGINEERING CHALLENGES TO THE LONG-TERM OPERATION OF THE INTERNATIONAL SPACE STATION - Spektr module repairs (power connections, leak detec- tion, solar array reinforcement) 12. How was the prediction for EVA aboard the ISS made ? Based on what criteria? The same Russian engineers who supported Mir EVA also are responsible for ISS EVA planning. Until water tank test- ing is performed, they base their estimates on an experienced assessment of flight hardware drawings and direct similarity to past on-orbit Mir work. Assembly is the primary driver for Russian ISS EVA. Science is piggybacked onto existing EVA time and there- fore has not yet had an impact to total ISS EVA demand. Maintenance is estimated at two to three days per year. Resources for up to two days of unplanned Russian EVA are reserved on every increment. NASA reviews and approves all Russian EVA demand via the EVA Project Office's Multilateral EVA Control Board (MECB). This forum manages the integrated sched- ule, content, sequencing, etc., of both U.S. and Russian EVA to ensure safety, success and efficiency. Station Operations 1. What areas have been most critical to the efficiency of the station ? From our observations, the Motion Control System, Elec- trical Power System, and Oxygen generation systems have been the most critical and impacting to station operations. 2. How many mission support people are required on the ground to tend MIR (average day)? Approximately 20 people constitute each Mir flight con- trol team 24-hour shift. This number does not include per- sonnel associated with MCC-M facility operation, ground station network operations, or Mir systems engineers pro- viding real-time consultation with the flight control team. Additional flight control and MCC-M personnel are also present to provide planning for future 24 hour shifts two to four days in advance of execution. 3. What are communications bandwidths (uplinks and downlinksJ and how much communications time is averaged per day ? Voice Communications: Two 30 kHz bandwidth VHF FM voice channels are available for crew-to-ground com- munications via ground stations. With the combination of NASA and Russian VHF ground stations, a minimum of ten minutes of VHF FM voice communication is typically avail- able of each daily orbit. Communications sessions average 20-25 minutes in length during the ten orbits which consti- tute the crew work day. Packet Data Communications: One of the VHF FM voice channels can be used to send 9.6 kbaud "packet" data, a type of e-mail transmission commonly used in the amateur radio community. This is typically done during at least three com- munication sessions per day. Telemetry Data: Two 256 kbps telemetry streams are used to provide systems data to MCC-M via Russian ground stations. The Russian telemetry ground stations are avail- able for 9 of the 16 daily orbits and are used whether the crew is awake or not. Telemetry communications sessions average 20-30 minutes in length. Telemetry is not available via NASA ground stations. Command Uplink: One 64 Kbps UHF command uplink is used for Mir station commanding from Russian ground stations only. Command capability is not available via the NASA ground stations. Satellite Communications: Voice, video, and limited telemetry data was also available via the Altair relay satel- lites. However, this system experienced frequent operational problems with the on-board Mir satellite communications equipment, the Altair satellites and the Altair satellites' ground stations. Consequently this system was used on a limited basis (three to four times per week maximum depend- ing on system availability) and generally done when out-of- range of the Russian ground stations. Communications sessions of one Mbps voice and television or one Mbps telemetry and voice could be provided for up to 45 minutes using Altair. Limited command capability was also avail- able at 64 kbps. This system has not been used since March 1999 due to the failure of the last remaining relay satellite. Crew Timelines 1. How valuable is the time spent performing on-orbit handover? This was invaluable for both Russian and NASA crew members. 2. What percentage of crew time did you allocate for on- orbit handover for those occasions when 2 Soyuz were docked at Mir? NASA operations were not impacted by the presence of two Soyuz crews. Handover remained the highest priority and largest time consumer for the Russian Commanders and Flight Engineers of both Soyuz crews. Handover activities constituted at least 50% of crew time during the handover period. 3. How much time was in the crew timeline each day to per- form exercise?
APPENDIX C Three hours per day is the Russian medical requirement. This is normally broken up into two 90 minute exercise sessions. 4. How much time is required for relaxation periods each week for a long duration space flight? Weekends and all Russian holidays are considered off- duty days for the crew. The Mir crew is normally scheduled for an 0800-2300 Moscow time work day. Morning wakeup, breakfast, lunch and dinner time in addition to at an hour of personal time at the end of each day are scheduled and con- sidered non-work periods. 5. How much time is required each weekfor a crew member to have a family conference? Family conferences are scheduled once per week using the VHF FM voice system and two-way television, if the television system is available. The duration of these con- ferences is typically 20-30 minutes. Additional time to 41 communicate with family and friends is available using amateur radio equipment on-board. Amateur radio commu- nications sessions were done at crew discretion. 6. How many crew hours per day are allocated to mainte- nance, repair, and/or science? How does the actual experi- ence compare to the allocation? Timeline content is very mission dependent. Scheduled work activity is approximately 11 hours per crew workday. During Phase 1 of the ISS program, the actual crew work activity often exceeded the scheduled amount of time depending on the type of work being performed and the presence of systems malfunctions on board the station. REFERENCE NASA (National Aeronautics and Space Administration). 1998. Phase 1 Lessons Learned. August 26, 1998. Houston, Texas: NASA Johnson Space Center.
flying, remotely controlled robotic platform that can carry a camera (or two cameras when stereoscopic Images are warranted) and other sensors to any part of the ISS. AERCam can perform the following [asks: visual inspection pre-EVA reconnaissance closeout video documentation supplemental video coverage for other robotic operations positioning of cameras and lights for EVA crew nonvisual sensing (e.g., presence of ammonia, infrared camera, measurement of structural vibrations The AERCam can be operated easily by an IVA astronaut and can be deployed without disturbing the micrograv~tr environment of the ISS. AERCam has already proven it; practicality. On the STOW mic~i`,n AF.R~Am WAC Or: i- ~ ~_1 ~. ~. ~ ~ ~ ~ W ~ ^ ~- ~ ~ ~ ~ eleoperanon moue In close proximity to the Space Shuttle orbiter and within the operator's line of sight. Current procedures for inspecting Me station exterior to assess damage cause major d~sruphons to the ISS microgranty environment. Although the AERCam system could satisfy the needs of the ISS, it is not currently on the manifest for the AS. Recommendation. Development and test of the AERCam system should be continued so that it can be included in the baseline International Space Station pSS) equipment manifest for support of extravehicular activities. ADVANCED ROBOTIC TECHNOLOGIES In addition to Improvements In visual inspection capabilities, improvements could be made in robotic systems to optimize Me capabilities of the human-robot teams aboard the ISS and on me ground. Significant progress In robotics research promises to enhance the performance of robotic servicing systems through improved teleoperation modes and superv~sed-autonomous modes of operation for all of the planned or proposed robotic systems for the ISS. Two research and development programs, the Ranger Project and Me Robonaut Project being developed by NASA Johnson Space Center, are sufficiently well developed and have a high enough probability of yielding significant improvements to the operation of the ISS post Assembly Complete to warrant serious consideration. Both programs are focused on enhancing robotic servicer technologies. 42