NASA is preparing to launch a laboratory for the international space station.
The hi-tech Destiny lab is due to be propelled into space on Friday aboard space shuttle Atlantis.
The cost is so high that there is no back-up module. If Destiny is damaged or destroyed, space station construction will be put on hold for years.
Not everyone believes Destiny will be a 'jewel in the sky'.
Physics professor at the University of Maryland and director of the American Physical Society's Washington office, Robert Park, said: "I'm a great advocate of space-based research, but not with a manned space station. That just has not turned out to be productive at all".
NASA is shrugging off criticism as it prepares to launch the $1.4 billion laboratory, the centerpiece of the international space station, Alpha, and the most expensive station component.
Given the high stakes of this mission, Commander Kenneth Cockrell and his crew are understandably nervous. The shuttle astronauts will perform three spacewalks to attach Destiny to the space station. Then it will be up to Alpha's three residents to fix up the lab.
Possibly the hardest part of the mission will be easing Destiny - 28ft long and 14ft in diameter - out of Atlantis' cargo bay. Astronaut Marsha Ivins will have just 2 inches of clearance when she lifts the lab with the shuttle robot arm.
The 30,000-pound Destiny is loaded with computers and other electronics needed to run not only the lab, but the entire space station. There are no racks of equipment - those will arrive on later shuttle flights.
Destiny's first experiments in the spring will involve protein crystals and the astronauts and cosmonauts. NASA wants to better understand how humans adapt to weightlessness to prepare for expeditions to Mars.