1.   Financial woes have also buffeted the ISS, the orbiting construction site that has been the destination for most of the current shuttle flights.

2.   Rockwell has opted for a winged spaceship, similar to the current shuttle but without the exterior fuel tanks.

3.   The current shuttle mission is the second such utility flight to the station.

4.   The McDonnell Douglas version would launch and land vertically, while the other two would fly like the current shuttle with a vertical take off and a rolling landing.

5.   The next generation would not require the extensive and costly launch infrastructure the current shuttle fleet needs.