The eyes of NASA and the rest of America's manned space flight program will be squarely fixed on Utah again Tuesday as Morton Thiokol conducts the fourth in a series of full-scale tests of its redesigned solid rocket motor.

The test is the next-to-the last hurdle to be cleared before an identical version of the motor can carry the Space Shuttle Discovery aloft sometime in August.The 126-foot long, 1.2 million-pound motor will undergo a full-duration horizontal test firing for two minutes at the company's remote West Desert test facility, 25 miles west of Brigham City. It will be the first such firing conducted in Morton Thiokol's new test bay facility.

If Tuesday's test proves successful, one remaining full-scale firing will be held in July before the launch of Discovery.