http://www.foxbusiness.com/features/2018/01/18/nasa-pushes-spacex-on-rocket-spacex-speaks-to-risks-in-falcon-9-wsj.html
"NASA is working with Elon Musk's SpaceX to redesign part of
the fuel system for the company's Falcon 9 rockets
and then will demand at least seven successful unmanned flights
before allowing astronauts on board. "
Falcon 9 の燃料系の再設計が進行中で，
有人打ち上げの前に少なくとも7回の無人打ち上げ連続成功が要求されている．
（これ以降の記事には，
Falcon 9 のヘリウム高圧タンク系の再設計と，また燃料充填手順が問題視）
"The hearing also disclosed that the statistical limit for a "failed mission"
remains approximately one in 55 launches, despite several years of
intense development, NASA expenditures of about $5 billion
and significant additional investment by the two companies.
That limit applies to mission failures in which the vehicle doesn't reach
the space station but the crew uses emergency procedures to survive."
数年の集中的な開発，$5 billion の NASA の投資と，2つの会社の追加投資にもかかわらず，
ミッション失敗の統計限界は 55回に1回程度に止まっている．
このミッション失敗には，宇宙ステーションには到達しないが緊急脱出手段を用いたものを含む．
