system it has to be affordable to go. it can't just be like billions of dollars per person to go to mars. no way you could establish a base on bars at that cost. so we have to develop rockets that are rapidly and as close to completely as reusable as possible. as a example, the falcon line cost about $60 million. sort of like a jet. but the cost of the propellant is only about $200,000. >> we asked you about why with improvement over the last 20 to 30 years and one thing that doesn't improve is jet travel. you are flying from new york to london, it takes about as long