Aerospace Project Budget Overruns: NASA and ESA Missions
NASA Office of Inspector General and GAO produce the most detailed cost-growth data on space programmes available anywhere. Cost growth across the major NASA missions has averaged about 25% above original baselines.
| Mission | Original budget | Final / latest | Overrun |
|---|---|---|---|
| James Webb Space Telescope | $500M (1997 study) | $9.66B (GAO-21-306 life-cycle estimate) | ~+1,830% |
| Space Launch System (SLS) | $10B (2011) | $23.8B through 2025 | +138% |
| Orion crew vehicle | $5B (2006) | $20.4B through 2025 | +308% |
| Mars Sample Return (cancelled in the final FY2026 budget, Jan 2026) | $3-5B (2020) | $11B (final 2024 NASA estimate) | +150% to +260% |
| Europa Clipper | $2B (2015) | $5.2B (2024 launch) | +160% |
| International Space Station (US share) | $17.4B (1993) | $~75B (assembly through 2010) | +330% |
| Mars Science Laboratory (Curiosity) | $1.6B (2006) | $2.5B (2012 launch) | +56% |
| Galileo (ESA navigation constellation) | EUR 3B | EUR 10B+ | +230% |
Sources: NASA Office of Inspector General reports, GAO NASA Assessments of Major Projects (annual), European Court of Auditors special report on Galileo. The James Webb row was re-traced to its documents on 8 October 2026 (a 1997 study estimate per the US House Science Committee's 2011 hearing charter, and the life-cycle estimate in GAO-21-306); the other rows have not yet been re-traced to a specific report and page, so check the agency report before citing them.
Why space programmes overrun
- Technology readiness: Missions are routinely greenlit with critical subsystems at TRL 4 or 5, meaning they have to be matured during the project itself. JWST's sunshield, deployment mechanism and mirror segments were all at low TRL at project start.
- No-failure tolerance: A satellite or interplanetary spacecraft cannot be repaired in flight, so the cost of late discoveries is total loss. Test programmes must be exhaustive, and overrun tolerance is essentially zero.
- Long durations: Multi-decade programmes encounter inflation, regulatory shifts, and political resets. JWST began in 1996 and launched 2022.
- Heritage / new-tooling tension: Programmes often rely on industrial heritage from past missions, but key suppliers may have exited or lost workforce.