1.   Environmentalists first raised concerns about the impact of rocket exhaust, particularly from solid fuel rockets, on stratospheric ozone about eight years ago.

2.   Many engineers favor replacement of the solid rockets with a liquid fuel rocket that could make an automated landing after being jettisoned by the shuttle early in its ascent.

3.   The missile will consist of a multistage solid fuel rocket and a kill vehicle with on-board guidance to direct it to its deadly rendezvous.

4.   It is a three-stage, solid fuel rocket, but few details on its performance have been released.

5.   The reports said the three-stage, solid fuel rocket will replace aging silo-based nuclear missiles.

6.   They are launched atop Japanese solid fuel rockets.