On May 27, NASA will launch their first flight with astronauts to the International Space Station from U.S. soil in nearly 10 years. This mission is the first launch of American astronauts aboard an American rocket and spacecraft as part of their Commercial Crew Program . NASA astronauts Bob Behnken and Doug Hurley will fly on SpaceX ’s Crew Dragon spacecraft, lifting off on a Falcon 9 rocket from Kennedy Space Center in Florida, for an extended stay at the space station for the Demo-2 mission. The specific duration of the mission is to be determined. As the final flight test for SpaceX, this mission will validate the company’s crew transportation system, including the launch pad, rocket, spacecraft, and operational capabilities. This also will be the first time NASA astronauts will test the spacecraft systems in orbit. Behnken and Hurley were among the first astronauts to begin working and training on SpaceX’s next-generation human space vehicle and were
Numbers Defendit numerus: There is safety in numbers We begin by talking about numbers. This may seen rather elementary but is does set the scene and introduce a lot of notation. In addition much of what follows is important in computing. Integers I will assume you are familiar with the integers. 1,2,3,4,. . .,101,102, . . . , n, . . . , 2^32582657 − 1, . . . sometime called the whole numbers. These are just the numbers we use for count- ing. To these integers we add the zero, 0, defined as: 0 + any integer n = 0 + n = n + 0 = n Once we have the integers and zero mathematicians create negative integers by defining (−n) as: the number which when added to n gives zero, so n + (−n) = (−n) + n = 0. Eventually we get fed up with writing n+(−n) = 0 and write this as n−n = 0. We have now got the positive and negative integers {. . . , −3, −2, −1, 0, 1, 2, 3, 4, . . .} You are probably used to arithmetic with integers which follows simple rules. To