Testimony 

Before the Subcommittee on Space and 

Aeronautics, Committee on Science and 

Technology, House of Representatives

United States Government Accountability Office

GAO 

For Release on Delivery 

Expected at 10:30 a.m. EDT 

Thursday, April 24, 2008 NASA

Challenges in Completing 

and Sustaining the 

International Space Station 

Statement of Cristina T. Chaplain, Director 

Acquisition and Sourcing Management 

GAO-08-581T 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

To view the full product, including the scope 

and methodology, click on GAO-08-581T. 

For more information, contact Cristina 

Chaplain at (202) 512-4841 or 

chaplainc@gao.gov. 

Highlights of GAO-08-581T, a testimony 

before the Subcommittee on Space and 

Aeronautics, Committee on Science and 

Technology, House of Representatives 

April 24, 2008

NASA

Challenges in Completing and Sustaining the 

International Space Station 

NASA faces significant challenges in its plans to complete assembly of the 

International Space Station (ISS) prior to the scheduled retirement of the 

space shuttle in 2010. Since GAO testified on this issue in July 2007, the 

shuttle flight schedule has remained aggressive—slating the same number of 

launches in a shorter period. While NASA thinks the proposed schedule is still 

achievable, the schedule 

• is only slightly less demanding than it was prior to the Columbia disaster 

when the agency launched a shuttle every other month with a larger 

shuttle fleet and 

• leaves little room for the kinds of weather-related, technical, and logistical 

problems that have delayed flights in the past. 

Unanticipated delays could result in changes to the station’s configuration, 

that is, some components may not be delivered. We have previously testified 

that such changes could limit the extent of scientific research that can be 

conducted on board the ISS. 

After assembly is completed and the shuttle retires, NASA’s ability to rotate 

crew and supply the ISS will be impaired because of the absence of a vehicle 

capable of carrying the 114,199 pounds of additional supplies and spares 

needed to sustain the station until its planned retirement in 2016. For crew 

rotation and logistics, NASA plans to rely on: 

• Russian, European and Japanese vehicles. These vehicles were 

designed to augment the capabilities of the shuttle, not replace them, and 

have far less capacity to haul cargo. Furthermore, aside from a single 

Russian vehicle that can bring back 132 pounds of cargo, no vehicle can 

return cargo from the ISS after the shuttle is retired. 

• Commercially developed vehicles. NASA has pledged approximately $500 

million for the development of commercial vehicles. NASA expects these 

vehicles will be ready for cargo use in 2010 and crew use in 2012, even 

though none of the vehicles currently under development has been 

launched into orbit yet and their aggressive development schedule leaves 

little room for the unexpected. If one of these vehicles cannot be delivered 

according to NASA’s current expectations, NASA will have to rely on 

Russian vehicles to maintain U.S. crew presence on the ISS until the new 

generation of U.S. spacecraft becomes available. 

We are not making recommendations as a result of our review as NASA is well 

aware of the predicament it faces with the station and has weighed options 

and trade-offs for the remainder of the schedule manifest. However, it is 

important that flexibility continue to be maintained as events impacting 

schedule occur and that decisions be made with the goal of maximizing safety 

and results. 

The International Space Station 

(ISS), the most complex scientific 

space project ever attempted, 

remains incomplete. NASA expects 

the station’s final construction cost 

will be $31 billion and expects 

sustainment costs through the 

station’s planned retirement in 

fiscal year 2016 to total $11 billion. 

The space shuttle, the only vehicle 

capable of transporting large 

segments of the station into orbit, 

is critical to its completion. NASA 

plans to complete ISS assembly 

and retire the shuttle in 2010 in 

order to pursue a new generation 

of space flight vehicles, which will 

not begin to be available until 2015. 

To provide crew rotation and 

logistical support during this 5-year 

gap, NASA plans to rely on 

spacecraft developed by the 

commercial sector and other 

countries. 

In light of these circumstances, 

GAO examined the risks and 

challenges NASA faces in (1) 

completing assembly of the ISS by 

2010 and (2) providing logistics and 

maintenance to the ISS after 2010. 

GAO’s work to accomplish this 

included reviewing budget, 

planning, and other documents 

from NASA; reviewing NASA 

officials’ testimonies; and 

interviewing NASA and foreign 

space program officials. 
Page 1 GAO-08-581T 

Mr. Chairman and Members of the Committee: 

I am pleased to be here to discuss challenges that the National Aeronautics 

and Space Administration (NASA) faces in completing and sustaining the 

International Space Station (ISS). After delays and redesigns, efforts are 

under way for a long-envisioned expansion of the station so it can support 

a larger crew and more scientific research. NASA officials estimate the 

entire cost to complete the station will total $31 billion, and another $11 

billion will be needed to sustain it through its planned decommissioning in 

fiscal year 2016. 

The space shuttle has been and is critical to completion of the space 

station and re-supplying the station. The shuttle remains the only vehicle 

capable of transporting large segments of the station into orbit for 

assembly. NASA plans to complete ISS assembly duties and retire the 

shuttle fleet in 2010 in order to pursue a new generation of space flight 

vehicles for exploration. To that end, NASA has begun the process of 

making key decisions on suppliers that will no longer be needed. NASA 

officials told us that in many cases, restarting suppliers after these 

decisions are made would be cost prohibitive and time consuming. 

However, a new NASA vehicle will not be available until 2015 at the 

earliest, when the Crew Launch Vehicle (Ares I) and Crew Exploration 

Vehicle (Orion) are expected to fly. To fill the gap following retirement of 

the shuttle and provide crew rotation and logistical support, NASA plans 

to rely on a variety of spacecraft developed by the commercial sector and 

other countries. 

In July 2007, we testified on a number of challenges NASA was facing with 

regard to completing the ISS within the time constraints created by the 

shuttle’s retirement. Those challenges are still relevant. In light of these 

issues, we examined the risks and challenges NASA faces in (1) 

completing assembly of the ISS by 2010, and (2) providing logistics and 

maintenance support to the ISS after 2010. 

In short, our work continued to find that NASA’s plans to complete 

assembly of the International Space Station prior to the scheduled 

retirement of the space shuttle at end of fiscal year 2010 require much to 

happen and very little to go wrong. While NASA believes the schedule is 

still achievable, the flight rate that NASA is projecting is only slightly less 
Page 2 GAO-08-581T 

aggressive than it was prior to the Columbia disaster1 when, from 1992 to 

2003, the agency launched a shuttle every other month. At that time, NASA 

used four vehicles to maintain its flight schedule. To complete the station 

by 2010, NASA will need to maintain a similar flight rate with fewer 

shuttles and with a shuttle fleet that is aging and continuing to face fuel 

sensor challenges. NASA remains confident that the current manifest can 

be accomplished within the given time, and in fact, it has several months 

of reserve time in its manifest. However, agency officials readily admit 

that the schedule is aggressive. If delays continue, NASA may need to 

reduce the number of flights to the station, which could prevent delivery 

of items currently scheduled for assembly and the pre-positioning of 

critical spares. Further, while NASA still expects to be able to increase 

crew capacity from three to six persons, changes it may need to make to 

the space station’s configuration could limit the extent of scientific 

research that can be conducted onboard the ISS or quality of life for the 

crew. 

After assembly is completed and the shuttle is retired, NASA’s ability to 

rotate crew and supply the ISS will be impaired because of the absence of 

a vehicle capable of carrying the 114,199 pounds (or 51.8 metric tons) of 

additional supplies needed to sustain the station until its planned 

retirement in fiscal year 2016. NASA plans to rely on Russian, European 

and Japanese vehicles to service the station. Even with these vehicles, this 

shortfall remains. While the Russian vehicles are already in service, the 

European vehicle just completed its first operational test flight, and 

development efforts are still under way on the Japanese vehicle. In 

addition, these vehicles were designed to augment the capabilities of the 

shuttle, not replace them. Both the European and Japanese vehicles were 

designed to deliver supplies to the station but their capacities are not 

equal to the shuttle’s 37,864 pounds of capacity. Furthermore, aside from a 

single Russian vehicle that can bring back 132 pounds of cargo and rotate 

crew, no vehicle can return cargo from the International Space Station 

after the shuttle is retired. NASA plans to rely on commercially developed 

vehicles to address some of these shortfalls and has pledged 

approximately $500 million for their development. NASA expects one of 

these vehicles will be ready for cargo use in 2010 and crew use in 2012. 

However, no vehicle has successfully been launched into orbit and their 

development schedules may leave little room for the unexpected. If these 

 1

 In 2003, the space shuttle Columbia broke up as it returned to Earth after 16 days in orbit. 

After the accident of Columbia, the shuttle fleet was grounded for approximately 2 1⁄2 years. 

During that the time, U.S. crew and supplies were launched in the Russian Soyuz and 

Progress. 
Page 3 GAO-08-581T 

vehicles cannot be delivered according to NASA’s current expectations, 

NASA will have to rely on Russian vehicles to maintain U.S. crew on the 

International Space Station until the new generation of U.S. spacecraft 

becomes available. 

To conduct our work, we reviewed documents and testimonies by NASA 

officials relating to the challenges associated with ISS completion, the 

delivery schedule for ISS assembly and replacement units, and the space 

shuttle manifest. We reviewed key ISS budget and strategic maintenance 

plans, the ISS Independent Safety Task Force Report, and previous GAO 

reports relating to the ISS. We visited and interviewed officials responsible 

for ISS operations at NASA Headquarters, Washington, D.C., and the 

Johnson Space Center in Houston, Texas. At NASA Headquarters, we met 

with officials from the Exploration Systems Mission Directorate and the 

Space Operations Mission Directorate, including representatives from the 

International Space Station and space shuttle programs. We met with ISS 

and space shuttle officials at the Johnson Space Center. We also talked to 

a commercial developer of space vehicles and met with representatives of 

foreign space efforts. Complete details of our scope and methodology can 

be found in appendix I. We conducted this performance audit from July 

2007 to April 2008, in accordance with generally accepted government 

auditing standards. Those standards require that we plan and perform the 

audit to obtain sufficient, appropriate evidence to provide a reasonable 

basis for our findings and conclusions based on our audit objectives. We 

believe that the evidence obtained provides a reasonable basis for our 

findings and conclusions based on our audit objectives. 

The International Space Station program began in 1993 with several 

partner countries: Canada, the 11 member nations of the European Space 

Agency (ESA), Japan, and Russia. The ISS has served and is intended to 

expand its service as a laboratory for exploring basic questions in a variety 

of fields, including commercial, scientific, and engineering research. The 

first assembly flight of the station, in which the space shuttle Endeavor 

attached the U.S. laboratory module to the Russian laboratory module, 

occurred in early December of 1998. However, since the program’s 

inception, NASA has struggled with cost growth, schedule delays and redesigns of the station. As we reported in the past, these challenges were 

largely due to poorly defined requirements, changes in program content 

and inadequate program oversight. Due to these challenges, the 

configuration of the station has devolved over time. In the spring of 2001, 

NASA announced that it would make major changes in the final 

Background 
Page 4 GAO-08-581T 

configuration of the ISS to address cost overruns. In 2003, the National 

Academies reported that this reconfiguration greatly affected the overall 

ability of the ISS to support science. NASA estimates that assembly and 

operating costs of the ISS will be between $2.1 billion to $2.4 billion 

annually for FY2009-FY2012. The ISS as of February 19, 2008, is 

approximately 65 percent complete. 

The shuttle program and the ISS program are inherently intertwined. The 

shuttle has unique capabilities in that it can lift and return more cargo to 

and from orbit than any other current or planned space vehicle. Figure 1 

shows the capabilities of the shuttle in various configurations. Most 

segments of ISS cannot be delivered by any other vehicle. For example, 

the Columbia disaster in 2003 put ISS assembly on hiatus as NASA ceased 

shuttle launches for 21⁄2 years while it investigated the safety of the fleet. 

During this period, the Russian Soyuz became the means of transportation 

for crewmembers traveling to and returning from the ISS. 

Figure 1: Cargo Capabilities of the Shuttle 

In a major space policy address on January 14, 2004, President Bush 

announced his “Vision for U.S. Space Exploration” (Vision) and directed 

NASA to focus its future human space exploration activities on a return to 

the Moon as prelude to future human missions to Mars and beyond. As 

Mixed Flight Capability: 16,480 lbs./7,475 mass kg. 

Consisting of internal cargo (8,818 lbs./4,000 kg.), external (2,205 lbs./

1,000 kg.), water (882 lbs./400 kg.), nitrogen (55 lbs./25 kg.), oxygen

(110 lbs./50 kg.) and propellants which are fuel and oxidizer (4,409 lbs./

2,000 kg.). The majority of internal cargo is packaged in cargo transfer bags and 

then flown in either a rack or middeck locker.

External Capability: 14,716 lbs./6,675 mass kg.

Consisting of internal cargo (441 lbs./200 kg.), external (8,818 lbs./4,000 kg.), 

water (882 lbs./400 kg.), nitrogen (55 lbs./25 kg.), oxygen (110 lbs./50 kg.) and 

propellant (4,409 lbs./2,000 kg.). Two Express Logistics Carriers (ELC) can be 

loaded on the Shuttle payload bay. The ELC’s can be left on the ISS for stowage 

of science payloads and maintenance of spares—each holding up to 10 orbital 

replacement units (ORU), and each has the ability to deliver up to two science 

payloads.

Assembly Capability: 37,864 lbs./17,175 mass kg.

Consisting of internal cargo (441 lbs./200 kg.), external (31,967 lbs./14,500 kg.), 

water (882 lbs./400 kg.), nitrogen (55 lbs./25 kg.), oxygen (110 lbs./50 kg.) and 

propellant (4,409 lbs./2,000 kg.). The assembly configuration enables the 

delivery of assembly hardware, such as the ESA’s Columbus module.

Source: GAO analysis of NASA data.

The shuttle’s different capabilities
Page 5 GAO-08-581T 

part of the Vision, NASA is developing new crew and cargo vehicles, with 

the first crew vehicle currently scheduled to be available in 2015. The 

President also directed NASA to retire the space shuttle after completion 

of the ISS, which is planned for the end of the decade. Based on that 

directive, NASA officials told us that they developed a manifest consisting 

of 17 shuttle launches to support ISS assembly and supply between 2005 

and 2010.2

 Nine of these have taken place. In response to the President’s 

Vision, NASA formally set September 30, 2010, as the date that the shuttle 

program will cease because agency officials believe that continuing the 

program beyond that date will slow development of the agency’s new 

vehicles—specifically, the agency budget cannot support both programs at 

costs of $2.5 billion to $4 billion above current budget. As shown in Table 

1, the shuttle program costs NASA several billion dollars annually and 

projected funding is phased out in fiscal year 2011. NASA officials stated 

that the majority of shuttle program cost is fixed at roughly $3 billion a 

year whether it flies or not. NASA officials stated that the average cost per 

flight is $150 million to $200 million.3

Table 1: Space Shuttle Program Costs 

Dollars in millions 

Funding 

Year FY 2007 FY 2008 FY 2009 FY 2010 FY 2011 FY 2012 FY 2013

space 

shuttle 

program 

3,315.3 3,266.7 2,981.7 2,983.7 95.7 — —

Source: President’s FY 2009 Budget Request. 

The 2005 NASA Authorization Act designated the U.S segment of the ISS 

as a national laboratory and directed NASA to develop a plan to increase 

the utilization of the ISS by other federal entities and the private sector. In 

response, NASA has been pursuing relationships with these entities. NASA 

expects that as the nation’s newest national laboratory, the ISS will 

strengthen NASA’s relationships with other federal entities and private 

sector leaders in the pursuit of national priorities for the advancement of 

science, technology, engineering, and mathematics. The ISS National 

 2

 The manifest includes 18 total flights, but one of the launches is reserved for repairs to the 

Hubble Space Telescope. 

3

 This cost is based on hardware, such as the booster rocket, used for the shuttles. 
Page 6 GAO-08-581T 

Laboratory is also intended to open new paths for the exploration and 

economic development of space. 

It will be a challenge for NASA to complete the space station by 2010 given 

the compressed nature of the schedule, maintenance and safety concerns, 

as well as events beyond its control such as weather. Any of these factors 

can cause delays that may require NASA to re-evaluate and reconstitute 

the assembly sequence. NASA remains confident that the current manifest 

can be accomplished within the given time and there are tradeoffs NASA 

can make in terms of what it can take up to support and sustain the station 

should unanticipated delays occur. However, failure to complete assembly 

as currently planned would further reduce the station’s ability to fulfill its 

research objectives and short the station of critical spare parts that only 

the shuttle can currently deliver. 

In our July 2007 testimony, we reported that NASA planned to launch a 

shuttle once every 2.7 months. The plan for launches remains aggressive, 

partly because NASA plans on completing the ISS with the last assembly 

mission in April 2010, with two contingency flights in February and July 

2010 to deliver key replacement units. The 5 months between the last 

assembly launch and shuttle retirement in September 2010 act as a 

schedule reserve, which can be used to address delays. There are 8 shuttle 

flights left to complete the station and two contingency flights left to 

deliver key components necessary to sustain the ISS after the retirement 

of the shuttle. There is an average of 2 1⁄2 months between each shuttle 

launch.4

 Table 2 shows the current shuttle manifest. 

Table 2: Remaining Flights of the Space Shuttles 

Space shuttles Expected launch dates 

Discovery May 31, 2008

Atlantisa August 28, 2008

Endeavor October 16, 2008

Discovery December 4, 2008

Endeavor March 2009 

 4

 This includes one mission to repair the Hubble Space Telescope and two contingency 

flights. 

The Retirement of the 

Shuttle Poses 

Challenges to NASA’s 

Ability to Complete 

the International 

Space Station 

Shuttle Flight Schedule Is 

Aggressive 
Page 7 GAO-08-581T 

Space shuttles Expected launch dates 

Discovery April 2009 

Endeavor August 2009 

Discovery October 2009 

Endeavorb February 2010 

Discovery April 2010 

Endeavorb July 2010 

Source: GAO analysis of NASA’s shuttle manifest. 

a

Mission to repair the Hubble Space Telescope 

b

Contingency flights

NASA has launched shuttles at this rate in the past. In fact, the agency 

launched a shuttle, on average, every two months from 1992 through the 

Columbia disaster in 2003. However, at that time the agency was launching 

a fleet of four shuttles.5

 The shuttles require maintenance and refurbishing 

that can last four to five months before they can be re-launched. 

Launching at such a rate means that the rotation schedule can handle few 

significant delays, such as those previously experienced due to weather 

and fuel sensor difficulties. Lastly, NASA officials said that Shuttle 

Atlantis, which was to go out of service after the Hubble mission, will 

return to servicing the ISS for two more flights, which NASA believes will 

add more schedule flexibility. 

 5

 The remaining three shuttles are the Atlantis, Discovery, and Endeavor. 
Page 8 GAO-08-581T 

Figure 2: Completed and Projected Space Shuttle Flights Needed for ISS Assembly 

NASA officials stated repeatedly that NASA is committed to safely flying 

the shuttle until its retirement and will not succumb to schedule pressure. 

However, the compressed nature of the manifest will continue to test that 

commitment. Fuel sensor challenges continue to surface in the shuttle 

fleet. For example, the recent shuttle Atlantis launch was delayed two 

months while NASA addressed a fuel sensor problem associated with the 

shuttle’s liquid hydrogen tank. This is the same system that caused a 2-

week delay in the launch of the shuttle Discovery in 2005. 

There are also challenges associated with the shuttle launch window. 

NASA officials told us that the duration of that window is dependent on a 

number of factors, which include changes in the position of the earth and 

spacecraft traffic restrictions. NASA must consider its traffic model 

constraints for vehicles docking at the space station. According to the 

traffic model for ISS, no other vehicle can dock while the shuttle is 

docked, and each vehicle has constraints on how long it can stay docked. 

For example, the shuttle can dock for a maximum of 10 days, while the 

Potential Launch Delays 

Remain 
Page 9 GAO-08-581T 

Soyuz can dock a maximum of 200 days. The docking of these two 

vehicles must be coordinated and meet other technical restrictions. 

In addition, the shuttle has experienced delays due to severe weather, 

such as when Atlantis’s external tank was damaged by a hailstorm in 2007. 

In this case the delay was about three months. Figure 3 shows the delays 

in recent shuttle launches related to weather and other causes. 

Figure 3: Causes of Recent Space Shuttle Flight Delays 

The ISS is scheduled to support a six-person crew as early as 2009 and 

maintain that capability through 2016. NASA officials said that equipment 

essential to support a six-person crew, such as systems for oxygen 

recycling, removal of carbon dioxide and transforming urine into water as 

well as an exercise machine will be delivered to the station this fall. In 

addition, there are two components that have been planned to hold this 

and other equipment needed for the six-person crew, which are scheduled 

to go up in April 2010. If unanticipated delays occur, NASA may need to 

hold back these two components—known as the Node 3 and the Cupola—

which could constrain the ability to conduct research and the quality of 

life on the station for the crew. 

NASA officials emphasized that NASA’s intent was to have most science 

conducted on ISS only after the assembly of the ISS was completed. The 

ISS currently supports three crewmembers. NASA stated that the majority 

Completion of ISS Needed 

to Expand Scientific 

Research 
Page 10 GAO-08-581T 

of the crew’s time is spent maintaining the station, rather than conducting 

scientific study. According to NASA, the crew spends no more than 3 

hours per week on science. Completion of the ISS would allow NASA to 

expand to a six-person crew who could conduct more research. 

Since the ISS is designated as a national laboratory, the expectation is that 

it will support scientific experimentation. NASA is in the process of 

negotiating agreements with scientific organizations to support scientific 

research on the ISS. NASA officials told us that they are negotiating a 

Memorandum of Understanding with the National Institutes of Health to 

explore the possibility of scientific experimentation onboard the ISS. 

These officials also told us that NASA is in the process of negotiating with 

at least two other agencies. 

NASA’s efforts to complete the ISS are further complicated by the need to 

put replacement units—the spare parts that are essential to sustaining the 

ISS—into position before the shuttle retires. The two contingency flights 

of the shuttle have been designated to deliver these key replacement units, 

which only the shuttle is capable of carrying. According to NASA, the 

original approach to deal with these key components (also known as 

orbital replacement units—ORU6

) was to take the ones that failed or 

reached the end of their lifetime back to Earth on the shuttle, refurbish 

them and launch them back to ISS for use. As a result of the shuttle 

retirement, NASA will no longer be bringing down ORUs to fix. Instead, 

NASA officials stated they have adopted a “build and burn” philosophy, 

which means that after the shuttle retires, instead of being brought down 

to be refurbished, ORUs will be discarded and disintegrate upon re-entry 

into the atmosphere. To determine how many replacement units need to 

be positioned at the station, NASA officials told us they are using data 

modeling that has been very effective in determining how long ORUs will 

last. Table 3 illustrates the shuttle manifest. This includes elements needed 

for the planned configuration to complete the station and delivery of 

critical spares. 

 6

 Orbital Replacement Units (ORU), according to NASA officials, are critical spares are 

necessary to sustain the ISS. 

The Need to Pre-Position 

Replacement Units to 

Sustain the ISS May Also 

Affect Assembly 
Page 11 GAO-08-581T 

Table 3: Manifest of Remaining Space Shuttle Flights 

Dates Space shuttle Element being delivered 

May 31, 2008 Discovery Kibo Japanese Experiment Module Pressurized 

Module (JEM-PM), one of two Japanese’s research 

facilities. 

Japanese Remote Manipulator System (JEM RMS) are 

two robotic arms that support operations on the outside 

of Kibo. 

Aug. 28, 2008 Atlantis Final shuttle Mission to Hubble Space Station. 

Oct. 16, 2008 Endeavor Multi-Purpose Logistics Module (MPLM) are a reusable 

“moving van” carrying equipments, experiments, and 

supplies to and from the ISS. 

Dec. 4, 2008 Discovery Fourth starboard truss segment (ITS S6), power 

element. 

Fourth set of solar arrays and batteries-power element.

March 2009 Endeavor Kibo Japanese Experiment Module Exposed Facility 

(JEM EF), the second Japanese research facility. 

Logistics Module Exposed Section (ELM-ES) is a pallet 

that can hold three experiment payloads. 

Spacelab Pallet Deployable 2 (SLP-D2) is a platform 

for mounting instruments. 

April 2009 Discovery MPLM 

Lightweight Multi-Purpose Experiment Support 

Structure Carrier (LMC) is the carrier to carry 

experiments to the ISS. 

Galley-multi-purpose facility to handle meal 

preparations. 

Second treadmill 

Crew Health Care System 2 (CHeCS 2) are a suite of 

hardware on the ISS that provides the medical and 

environmental capabilities to ensure the health and 

safety of crewmembers during long-duration missions. 

Aug. 2009 Endeavor EXPRESS Logistics Carrier 1 (ELC1) and 2 (ELC2) 

are designed to carry external payloads and Orbital 

Replacement Units (ORUs). 

Oct. 2009 Discovery MPLM 

LMC 

Feb. 2010 

Contingency 

Flight 

Endeavor ELC3 and ELC4 are designed to carry external 

payloads and ORUs. 

April 2010 Discovery Node 3 is a habitation system with the Cupola

observatory. 
Page 12 GAO-08-581T 

Dates Space shuttle Element being delivered 

July 2010 

Contingency 

Flight 

Endeavor ELC5 and ELC1 are designed to carry external 

payloads and ORUs. 

Source: GAO analysis of NASA’s shuttle manifest. 

NASA currently plans to use two contingency flights for these 

replacements because all other flights are planned with assembly cargo. 

Recently, the NASA Administrator publicly stated that these flights are 

considered necessary to sustain the ISS and have been scheduled to carry 

key spare units. 

In the event that NASA completes assembly of the ISS on schedule and 

prepositions an adequate number of critical spares, the agency still faces a 

myriad of challenges in sustaining the research facility until its retirement, 

currently planned for fiscal year 2016. Without the shuttle, NASA officials 

told us that they face a significant cargo supply shortfall and very limited 

crew rotation capabilities. NASA will rely on an assortment of vehicles in 

order to provide the necessary logistical support and crew rotation 

capabilities required by the station. Some of these vehicles are already 

supporting the station. Others are being developed by international 

partners, the commercial sector, and NASA. (See Figure 4) Furthermore, 

some of these transportation services may face legal restrictions, and still 

others face cost, schedule, and performance issues that raise serious 

questions about their development and utilization. These issues will 

challenge NASA’s ability to close the sustainment gap between the 

retirement of the shuttle in 2010 and the availability of the Crew 

Exploration Vehicle (CEV) in 2015. Failure of any or some of these efforts 

would also seriously restrict NASA’s options to sustain and maintain a 

viable space station. 

Alternative Vehicle 

Options to Service the 

International Space 

Station Pose 

Challenges 
Page 13 GAO-08-581T 

Figure 4: Availability of Vehicles Serving the International Space Station 

a

Represents space exploration technologies only 

With the exception of the Shuttle and the recently completed 

demonstration flight of the ATV, the only vehicles currently capable of 

supporting the space station are the Russian Progress and Soyuz vehicles. 

NASA officials stated that both of these vehicles have provided reliable 

service to the ISS. From the Columbia disaster in 2003 until return to flight 

in 2005, the Russian vehicles were the sole source of logistical support and 

crew rotation capability for the station. The Progress provides 

atmospheric gas, propellant, water, and pressurized cargo. It also has the 

capability to use its thrusters to change the Station’s altitude and 

orientation. The Soyuz provides crew delivery and rescue capability for 

three crew members. Progress vehicles are expendable and offer no 

recoverable return capability, but provide important trash removal 

capabilities. Soyuz vehicles have a limited recoverable cargo capacity. 

However, some NASA officials have suggested that their limited 

capabilities restrict the capacity of the station to move to a six-member 

crew and significantly limit the scientific research because the vehicles 

cannot bring experiments to earth for assessment. 

NASA currently purchases crew and cargo transport services from Russia 

through a contract with the Russian Federal Space Agency (Roscosmos). 

Russian Vehicles 

2006 2007 2008 2009 2015 2016

Shuttle services ISS

Soyuz and Progress

ATV

HTV

COTSa

Source: GAO analysis of NASA data.

Currently servicing ISS

Development and

not yet operational

Awaiting congressional action

▲

Test flight

▲

Test flight

▲

Demonstration of cargo vehicle

Development phase Estimated 

operational date

CEV

2010 2011 2012 2013 2014

ATV European Space Agency Automated Transfer Vehicle (ATV) 

HTV Japan Aerospace Exploration Agency H-II Transfer Vehicle (HTV)

COTS Commercial Orbital Transportation Services (COTS)

CEV NASA’s Crew Exploration Vehicle (CEV) 
Page 14 GAO-08-581T 

NASA officials told us that after the initial ISS contract between 

Roscosmos and NASA expired, NASA entered into another contract that 

runs through 2011. However, according to NASA, the Iran Nonproliferation 

Act of 2000 restricted certain payments in connection to the ISS that may 

be made to the Russian government. In 2005, NASA requested relief from 

the restrictions of the Act, and Congress amended the Act.7

 Through this 

amendment, NASA and Roscosmos have negotiated quantities and prices 

for services through January 1, 2012. 

NASA officials anticipate the use of 4 Soyuz flights per year and 

approximately 6 Progress flights beginning in approximately 2010. While 

NASA officials stated that they are making every effort to limit amount of 

fees they pay for usage of Russian vehicles, to date, NASA officials told us 

that they anticipate that from fiscal year 2009 to fiscal year 2012, NASA 

will spend $589 million on cargo and crew services from the Russians.8

NASA officials also told us that the Roscosmos has suggested that it will 

charge NASA higher fees for usage of its vehicles. 

NASA has stated it will use its international partners’ vehicles to conduct 

some supply activities. Specifically, Japan’s Aerospace Exploration 

Agency (JAXA) H-II Transfer Vehicle (HTV) and the European Space 

Agency’s (ESA) Automated Transfer Vehicle (ATV) vehicles will be used 

for bringing up cargo. NASA’s reliance on the ATV and HTV assumes that 

these vehicles will be ready to service the ISS by the time the shuttle stops 

flying in 2010. 

The new vehicles being developed by the European and Japanese space 

agencies are very complex. The ATV had a development timeline of 20 

years. Its first operational test flight to the ISS was in March 2008. NASA 

has stated that both the European and Japanese vehicle development 

programs experienced technical hurdles and budgetary constraints, but 

are committed to fulfilling their roles as partners in the ISS program. 

NASA officials told us they have confidence the European vehicle will be 

 7

 The 2005 Amendment to the Iran Nonproliferation Act of 2000 altered the Acts definition 

of “extraordinary payments in connection with the International Space Station.” NASA 

refers to this amendment as its “exemption.” 

8

 NASA and Roscosmos have negotiated quantities and prices for services through calendar 

year 2011. According to NASA it will require additional relief from the restrictions of the 

Act, currently entitled the Iran, North Korea and Syria Nonproliferation Act. 

European and Japanese 

Vehicles 
Page 15 GAO-08-581T 

available for ISS operations before retirement of the shuttle, but they are 

not as confident about the Japanese vehicle’s being ready by that time. The 

Japanese vehicle is still under development and has faced some setbacks. 

NASA officials told us that the HTV’s first test launch is planned for July 

2009. 

Figure 5: The European Automated Transfer Vehicle (ATV) 

Figure 6: The Japanese H-II Transfer Vehicle (HTV) 

Maximum capability: 

16,535 lbs./7,500 mass kg. The ATV is capable of 

performing many ISS reboost and altitude burns and 

resupplying ISS with water and atmospheric gas. The 

ATV has no external capability and is expendable and 

offers no recoverable return capability.

Source: GAO analysis of NASA data.

The European Automated Transfer Vehicle (ATV) capability

Maximum capability:

13,228 lbs./6,000 mass kg. 

The HTV can provide 

atmospheric gas and 

water re-supply to the ISS. 

The HTV can also deliver 

limited unpressurized 

external cargo. The HTV 

has no re-boost capability 

and is an expendable 

vehicle like the ATV.

Source: GAO analysis of NASA data.

The Japanese H-II Transfer Vehicle (HTV) capability
Page 16 GAO-08-581T 

In addition to potential development challenges, the international partner 

vehicles have constraints in terms of what they can take to and from the 

ISS in comparison to the shuttle. NASA’s current plans to manage the gap 

after the shuttle retirement do not take into account the possibility of 

delays in the development of these vehicles, and even if they do come on 

line on time, NASA officials estimate that there will be a significant 

shortfall to the ISS of at least 114,199 pounds (or 51.8 metric tons) in cargo 

re-supply capability. These vehicles were designed to augment the 

capabilities of the shuttle and have significantly less capability to deliver 

cargo to the ISS. The shuttle can carry a maximum cargo of close to 38,000 

pounds (17,175 kg.). In comparison, the European ATV’s maximum 

capability is 16,535 pounds (7,500 kg.) and the Japanese HTV’s average 

capability is 13,228 pounds (6,000 kg.). The HTV and ATV are expendable 

vehicles. NASA can use them for trash removal, but cannot carry cargo or 

scientific experiments back to earth because the vehicles disintegrate 

when re-entering the atmosphere. 

The Russian Progress and Soyuz vehicles also have very limited cargo 

capacity. For example, the Progress has an average capability of 5,732 

pounds (2,600 kg.)—roughly one-seventh the shuttle’s capability. The 

Progress, like the ATV and HTV, is an expendable vehicle. The Soyuz can 

transport three crew persons to the ISS and can serve as a rescue vehicle 

capable of taking three crew members back to earth. Unlike the ATV and 

HTV, the Soyuz does have the capacity to bring down cargo—roughly 132 

pounds (60 kg.). NASA officials have stated that until NASA deploys its 

new crew exploration vehicles or commercial vehicles become available, 

NASA will be dependent on the Russian vehicles for crew transportation 

services and on the Japanese and European vehicles for limited cargo 

services whenever they become available. 

Figure 7 compares the up mass capabilities of the various vehicles. 

International Partner 

Vehicles Have Constraints 

in Ability to Ferry Crew 

and Cargo to and from the 

ISS in Comparison to the 

Shuttle 
Page 17 GAO-08-581T 

Figure 7: Upmass capability by vehicle 

a

The Soyuz has the capability to bring down from the ISS up to 132 pounds of cargo. 

NASA is working with the commercial space sector through its 

Commercial Orbital Transportation Services (COTS) program to develop 

and produce vehicles that can take equipment and crew to and from the 

space station. NASA expects that these vehicles will be ready for cargo use 

in 2010 and crew use in 2012. However, these vehicles have yet to be 

successfully launched into orbit, and some NASA officials have 

acknowledged that their development schedules leave little room for the 

unexpected. 

Under the COTS program, NASA has pledged $500 million to promote 

commercial opportunities for space transportation vehicles. Using Space 

Commercial Vehicles 

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

Soyuza Space ATV HTV Progress

shuttle

Up mass capabilities by vehicle in pounds (in kilograms)

Vehicles

Maximum up mass (in kilograms)

Minimum up mass (in kilograms)

Total capability

Source: GAO analysis of NASA data.

13,228

(6,000)

16,535

(7,500)

132

(60)

5,732

(2,600) 14,716

(6,675)

37,864

(17,175)
Page 18 GAO-08-581T 

Act agreements9 instead of traditional contracting mechanisms, NASA will 

make payments to companies based on the achievement of key milestones 

during the development of their vehicles. These agreements are both 

funded and unfunded. For the two funded agreements that have been 

reached, NASA stated that the commercial suppliers for space 

transportation services will have customers outside of ISS, including 

NASA’s Constellation program, which plans to send humans back to the 

moon and eventually Mars. The COTS program will occur in phases. In the 

first phase companies will demonstrate the vehicle launch and docking 

capabilities with the ISS. The second phase is the procurement of services 

for transportation of cargo and crew to the ISS, which is scheduled to 

begin sometime in the 2010 timeframe. 

NASA had seven COTS agreements through the Space Act. NASA signed 

five unfunded Space Act agreements, which facilitate the sharing of 

technical and ISS integration information between commercial companies 

and NASA. NASA has funded two companies, Rocketplane Kistler (RpK) 

and Space Exploration Technologies (SpaceX). NASA officials stated that 

through the funded Space Act agreements, SpaceX has received $139 

million for its project and is still working on successfully launching a 

vehicle that can reach low-Earth orbit. The company successfully 

completed a critical design review in August 2007 and told us that it is 

planning its first orbital demonstration test flight for June 2009. NASA 

officials told us that RpK received $37 million in funding, but then forfeited 

the remainder of its share because it did not meet certain financial 

development milestones. When NASA began to redistribute these forfeited 

funds, RpK filed a bid protest with GAO, which GAO denied. NASA 

officials then moved forward and awarded $170 million to Orbital Sciences 

Corporation in February 2008. 

NASA officials acted quickly to award the forfeited money and expect that 

SpaceX will have cargo capability available in 2010 (by the time the shuttle 

is retired) and crew capability in 2012. While Space X has been meeting 

key milestones in the development of its vehicle, some officials at the 

 9

 COTS agreements are Space Act agreements issued pursuant to NASA’s other 

transactions authority. These types of agreements are not contracts, and are therefore 

generally not subject to those federal laws and regulations that apply to government 

contracts. NASA has budgeted $500 million in fiscal year 2006 to fiscal year 2010 as an 

investment for the demonstration of commercial orbital capabilities and will be executed in 

two phases. The first phase consists of technical development/demonstration funded by 

the Space Act agreements. The second phase may include the competitive procurement of 

orbital transportation services. 
Page 19 GAO-08-581T 

Johnson Space Center were skeptical that COTS would be available on the 

current projected schedule. Additionally, the International Space Station 

Independent Safety Task Force (IISTF) reported that design, development 

and certification of the new COTS program was just beginning and that “if 

similar to other new program development activities, it most likely will 

take much longer than expected and will cost more than anticipated.” In 

our opinion, the schedule is optimistic when compared to other 

government and commercial space programs we have studied. We will be 

studying the COTS program and schedules in more detail in response to a 

request of members of congress. 

NASA is under pressure to develop its own vehicles quickly as the space 

shuttle’s retirement in 2010 means that there could be at least a 5-year gap 

in our nation’s ability to send humans to space. Among the first major 

items of NASA’s development efforts to implement the Vision program are 

the development of new space flight systems—including the Ares I Crew 

Launch Vehicle and the Orion Crew Exploration Vehicle. Ares I and Orion 

are currently targeted for operation no later than 2015. NASA plans to use 

these vehicles as they become available to service the space station. 

However, we recently testified that there are considerable unknowns as to 

whether NASA’s plans for the Ares I and Orion vehicles can be executed 

within schedule goals, as well as what these efforts will ultimately cost. 

This is primarily because NASA is still in the process of defining many of 

the project’s performance requirements and some of these uncertainties 

could affect the mass, loads, and weight requirements for the vehicles. 

Such uncertainty has created knowledge gaps that are affecting many 

aspects of both projects. For example, a design analysis cycle completed 

in May 2007 revealed an unexpected increase in ascent loads (the physical 

strain on the spacecraft during launch) that could result in increases to the 

weight of the Orion vehicle and both stages of the Ares I. 

NASA recognizes the risks involved with its approach and it is taking steps 

to mitigate those risks. However, given the complexity of the Orion and 

Ares I efforts and their interdependencies, any significant requirements 

changes can have reverberating effects and make it extremely difficult to 

establish firm cost estimates and schedule baselines. If knowledge gaps 

persist, programs will cost more, fail to meet their schedules, or deliver 

less than originally envisioned. Ultimately, NASA’s aggressive schedule 

leaves little room for the unexpected. If something goes wrong with the 

development of the Crew Launch Vehicle or the Crew Exploration Vehicle, 

the entire Constellation Program could be thrown off course and the 

return to human spaceflight further delayed. 

Ares I and Orion 
Page 20 GAO-08-581T 

The decision to retire the space shuttle in 2010 has had profound effects 

on the ISS program. It leaves little flexibility in the shuttle schedule. Any 

delays could require NASA to choose between completing the station as 

planned and the pre-positioning of needed critical spares. The decision 

also leaves NASA dependent on Russia for crew rotation services until 

other vehicles are developed and demonstrated. And even with the 

development of these vehicles, NASA still faces a significant capacity 

shortfall in its ability to provide logistical support to the station. The 

shortfall may well impact support for a six person crew and the quality of 

research that can be conducted on the ISS. At the same time, it also 

provides opportunities to commercial suppliers to demonstrate 

capabilities that could have long-term benefits for future U.S. space 

exploration and development. We are not making recommendations as a 

result of our review as NASA is well aware of the predicament it faces with 

the station and has weighed options and trade-offs for the remainder of 

the schedule manifest. However, it is important that flexibility continue to 

be maintained as events impacting schedule occur and that decisions be 

made with the goal of maximizing safety and results. 

Mr. Chairman, this concludes my statement. I would be pleased to answer 

any questions that you or the other members may have at this time. 

For further questions about this statement, please contact Cristina T. 

Chaplain at (202) 512-4841. Individuals making key contributions to this 

statement include James L. Morrison, Greg Campbell, Brendan S. Culley, 

Masha P. Pastuhov-Purdie, Keo Vongvanith, and Alyssa B. Weir. 

Concluding 

Observations 

GAO Contacts and 

Staff 

Acknowledgments 
Page 21 GAO-08-581T 

To identify the risks and challenges NASA faces in completing assembly of 

the International Space Station by 2010, we 

• analyzed key documents and testimonies by NASA officials relating to the 

challenges associated with ISS completion. This included: the delivery 

schedule for ISS parts for assembly and the delivery schedule for 

replacement units, the space shuttle manifest, budget documents and the 

strategic maintenance plan, the ISS Independent Safety Task Force 

Report, and previous GAO reports relating to the ISS. 

• interviewed NASA mission officials to obtain information on the status of 

the ISS. We also discussed these issues with the International Partners 

(Canadian Space Agency, European Space Agency and Japan Aerospace 

Exploration Agency) to get their perspectives. 

To determine the risks and challenges NASA faces in providing logistics 

and maintenance support to the International Space Station after 2010, we 

• analyzed documents related to the up-mass and down-mass capabilities of 

the International Partners and SpaceX vehicles, the shortfall in ISS upmass for re-supply and sustainment, the new vehicles that will support ISS 

NASA’s plans for using Russian vehicles to support ISS through what 

NASA refers to as its “exemption,” and the impacts to the utilization of the 

ISS. 

• We interviewed key NASA officials from NASA Headquarters, the Space 

Operations Mission Directorate, NASA’s Commercial Orbital 

Transportation Services program, and the ISS program officials, and 

interviewed officials representing the International Partners 

To accomplish our work, we visited and interviewed officials responsible 

for the ISS operations at NASA Headquarters, Washington, D.C., and the 

Johnson Space Center in Houston, Texas. At NASA Headquarters, we met 

with officials from the Exploration Systems Mission Directorate and the 

Space Operations Mission Directorate, including representatives from the 

International Space Station and space shuttle programs. We also met with 

ISS and space shuttle mission officials at the Johnson Space Center. 

We conducted this performance audit from July 2007 to April 2008, in 

accordance with generally accepted government auditing standards. Those 

standards require that we plan and perform the audit to obtain sufficient, 

appropriate evidence to provide a reasonable basis for our findings and 

conclusions based on our audit objectives. We believe that the evidence 

obtained provides a reasonable basis for our findings and conclusions 

based on our audit objectives. 

Appendix I: Scope and Methodology 

(120674) 
Page 22 GAO-08-581T 
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