|
Items in cart [4] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 36
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
OCR for page 37
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
OCR for page 38
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
OCR for page 39
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
OCR for page 40
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?
OCR for page 41
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.
OCR for page 42
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
Representative terms from entire chapter:
mir eva
