| Year | Estimate* |
|---|---|
| 1984 | $8 billion (FY 1984 dollars, R&D only, no shuttle launches). |
| April 1987 | $16 billion, following restructuring in which program was split into two “phases”: $12.2 billion for Phase I; $3.8 billion for Phase II (FY 1984 dollars, R&D only, no shuttle launches). |
| April 1989 | $30 billion for Phase I (real year dollars (RYD),* through assembly complete, including shuttle launches during assembly and other costs-such as the Flight Telerobotic Servicer and ground facilities). Phase II “indefinitely postponed,” so not included in this or subsequent cost estimates. |
| Early 1990 | $37 billion (RYD, through assembly complete, including shuttle launches during assembly and other costs). |
| December 1990 | $38.3 billion (RYD, through assembly complete, including shuttle launches during assembly and other costs). |
| March 1991 | $30 billion (RYD, through permanent human capability, including shuttle launches during assembly and other costs). |
| Nov. 1993 | $17.4 billion, following termination of g744Freedom and initiation of International Space Station (RYD, development costs through assembly complete, no shuttle launches, includes costs for science experiments). |
| March 1998 | $21.3 billion (RYD, development costs through assembly complete, no shuttle launches, includes costs for science experiments). |
| g744April 1998 | g744Not a NASA estimate, but independent “Cost Assessment and Validation Team” headed by Jay Chabrow concludes cost could be $24.7 billion through assembly complete. |
| June 1998 | $22.7 billion (RYD, development costs through assembly complete, no shuttle launches, includes costs for science experiments). NASA did not accept the Chabrow figure, but agreed the program would cost $1.4 billion more. |
| February 1999 | $23.4-26 billion (RYD, development costs through assembly complete, no shuttle launches, includes costs for science experiments). |
| February 2000 | $24.1-$26.4 billion (RYD, development costs through assembly complete, no shuttle launches, includes costs for science experiments). |
| March 2001 (Under Discussion) | $22-23 billion, assuming termination of construction after completion of “U.S. Core” and attachment of European and Japanese lab modules (RYD, development costs through completion of the “U.S. Core”; no shuttle launches; includes costs for science experiments, reduced 40% from previous estimates). |
Prepared by CRS, using cost data from NASA.
*According to NASA's budget books (e.g., page SI-6 of the FY 2001 budget book), estimates in “real year dollars” (RYD) reflect current and prior year spending unadjusted for inflation, plus future year spending that includes a factor accounting for expected inflation.
| CALENDAR YEAR | NATURE OF CHANGE | REASON |
|---|---|---|
| Fall 1985-May 1986 | The original space station concept envisaged three elements: an occupied base for 8 crew members in a 28.5G5« orbit, an automated co-orbiting platform nearby, and an automated “polar platform” in orbit around Earth's poles. The original reference design for the occupied base was called the “Power Tower,” but a “dual-keel” approach was chosen instead as the baseline design in the fall of 1985; the details were approved by NASA in May 1986. Changes included: arrangement of truss structure and modules modified to place modules at center of gravity; solar dynamic power added to photovoltaic arrays; number of U.S. laboratory and habitation modules reduced from 4 to 2, with plans for 2 more provided by Europe and Japan (the new U.S. modules would be larger than the original design, however, so total habitable volume relatively unchanged); U.S. Flight Telerobotic Servicer added at congressional urging to supplement Canada's planned Mobile Servicing System. | Cost and user requirements. NASA stated that the dual-keel design would provide a better microgravity environment for scientists, more usable area for attached payloads, and better pointing accuracy. Cost estimate maintained at $8 billion ($FY 1984). |
| Late 1986 | Dual-keel design reaffirmed, but emphasis on building single-keel first in recognition of reduced availability of shuttle flights and reduced amount of cargo that would be allowed aboard the shuttle in the wake of the Challenger tragedy. Emphasis on early accommodation of experiments; fewer spacewalks; extended “safe haven” concept with the possibility for “lifeboats” for emergency return to Earth (not made a requirement at this time reportedly for cost reasons); increased use of automation and robotics; “lead center” management approach replaced with dedicated space station program office in Reston, VA. | January 1986 space shuttle Challenger tragedy and concern by astronauts at Johnson Space Center about the number of hours of spacewalks, or “EVAs”; quality and quantity of living space; standard of safety for “safe havens” (to which astronauts would retreat in emergencies such as depressurization or dangerous sunspot activity); lack of “lifeboats” for emergency return to Earth when the space shuttle was not docked with the station. Cost estimate unchanged. |
| 1987 | Program split into “phase 1” and “phase 2,” with single keel of occupied base built in phase 1 and second keel delayed until phase 2; polar platform part of phase 1; co-orbiting platform and solar dynamic power pushed into phase 2. | Rising program costs and expected budget constraints. Cost estimate had risen to $14.5 billion ($FY 1984) for research and development. New design estimated to cost $12.2 billion ($FY 1984) for Phase 1 and $3.8 billion ($FY 1984) for Phase 2, saving money in the near term, but costing more in the long term. |
| 1989 | Phase 2 indefinitely postponed; polar platform transferred from space station program to NASA's Office of Space Science and Applications (was for earth observation studies). Only remaining element is single-keel occupied base, divided into an initial phase with reduced capabilities (e.g., crew reduced to 4 from 8; electrical power reduced to 37.5 kw from 75 kw; use of open-loop instead of closed-loop life support system) and an assembly complete phase when “full capabilities” would be restored. NASA asserted that the capabilities envisioned in the 1987 Phase 2 program (dual-keel etc.) could still “evolve” sometime in the future to support expeditions to the Moon and Mars. | Cost growth and expected budget constraints. NASA termed this a “rephasing.” Cost for Phase I estimated at $19 billion real year dollars,* or $13 billion FY 1984 dollars, for R&D; NASA estimated total program costs through assembly complete at $30 billion real year dollars. |
| CALENDAR YEAR | NATURE OF CHANGE | REASON |
|---|---|---|
| 1990-1991 | U.S. modules reduced in size (from 44 feet to 27 feet); “pre-integrated truss” chosen in effort to reduce EVA requirements; total length reduced (from 493 feet to 353 feet); Flight Telerobotic Servicer canceled; crew size formally reduced to 4; electrical power reduced (from 75 kw to 56 kw); “lifeboat” added to the station's design but not included in the cost estimate; “assembly complete” designation abandoned with concept that station would continually evolve in an undefined and unbudgeted “follow-on phase.” | Beginning in 1990, concerns developed over rising program costs, weight, insufficient electrical power, and too many EVAs for maintenance. In Dec. 1990, NASA estimated program costs through assembly complete at $38.3 billion real year dollars. Congress directed NASA to restructure the station. New plan released in March 1991. NASA stated it would cost $30 billion real year dollars through 1999, though this was no longer the time when assembly would be completed (see column to the left). GAO estimated total program costs through 30 years of operation at $118 billion. |
| 2001 (Under Discussion) | International Space Station (ISS) construction to be terminated after completion of “U.S. Core” and attachment of European and Japanese modules. NASA will not build Habitation Module, Crew Return Vehicle, or Propulsion Module until and unless additional funds are made available. Then they would be “enhancements.” Details still under discussion, but could mean that crew size would be limited to 3 instead of 6 or 7 because only one Russian Soyuz would be available as a lifeboat instead of the larger CRV. Smaller crew size would limit amount of science that can be conducted. Science program currently being restructured. | Cost growth of $4 billion over estimate made in its FY 2001 budget submission. ISS had been estimated to cost $17.4 billion (real year dollars) when it began in 1993 (FY 1994). NASA's estimate rose to $21.3 billion and then $22.7 billion in 1998, to $23.4-26 billion in 1999, and to $24.1-26.4 billion in 2000. NASA's March 2001 plan to discontinue construction after the “U.S. Core” is completed and attachment of the European and Japanese module results in a cost estimate of $22-23 billion and a “completion” date of November 2003-October 2004. Hardware being built for NASA by Europe and Japan (Node 3 and Centrifuge Accommodation Module, respectively) as part of barter agreements could be launched if NASA has sufficient funding for integration costs. |
Prepared by CRS, based on information from NASA, historical CRS publications, congressional hearings, and articles in the trade press.
*According to NASA's budget books (e.g., page SI-6 of the FY 2001 budget book), estimates in “real year dollars,” reflect current and prior year spending unadjusted for inflation, plus future year spending that includes a factor accounting for expected inflation.
| Module | Plan | Actual | Slip |
|---|---|---|---|
| Zarya (Sunrise) | 6/98 | 11/98 | 5 mos |
| Unity | 7/98 | 12/98 | 5 mos |
| Zvezda | 1/98 | 7/00 | 19 mos |
| Destiny | 5/99 | 2/01 | 19 mos |
| Milestone | Rev C | Rev F | Slip |
|---|---|---|---|
| Assembly Complete | 12/03 | 4/06 | 28 mos |
| FY 1994—Assy Compl | Post-Assy Operations | |
|---|---|---|
| Int'l Space Station | $24.1-26.4B | $13-15B |
| Shuttle Support | $14.1B | $19B |
| Other (Civil Service) | $2.0-2.1B | TBD |