Conclusions
Scientific milestone comparable to invention of telescope
No obvious show stoppers identified so far
Long-lead, high cost items (M1, structure) are low risk
Difficulties
- stiffness / eigenfrequency of structure
- adaptive optics module
- figuring of quaternary mirror
Modular scheme: start using before completion
Cost: ~ $1 billion (based on very conservative assumptions)
Schedule: ~ 15 years (fabr.), 10 years for start of ops.