When the new, improved space shuttle Discovery blasts off from the Kennedy Space Center in the near future, it will carry with it America's hopes for a future in space.

The shuttle will look much like NASA's previous 25 shuttle launches, according to an article in the current issue of Popular Mechanics, but there have been significant modifications.There have been 40 major changes, costing $450 million, in the solid-rocket boosters, villains of the Challenger tragedy.

In addition, there have been 39 major changes, costing $200 million, in the shuttle's liquid-fueled main engines. The orbiter itself also has been modified.

All told, there have been 68 mandatory modifications and 210 optional changes in the shuttle. The only piece of hardware that remains essentially the same is the 154-foot long external tank - the only disposable part of the system.

There also have been significant modifications in NASA's attitude toward safety. In the post-Challenger Rogers Report, NASA came under fire for not having a safety rep in on the launch decision. Safety will have a vote this time.