WASHINGTON -- Within the span of a single year, from August 1998 to May 1999, The United States lost six space launchers along with their payloads. Last August, a military Titan IV thundered into the skies above Cape Canaveral carrying a secret satellite for the National Reconnaissance Office (NRO), a Defense Dept. organization that runs America's fleets of spy spacecraft. In less than a minute, the rocket blew up. In the same month, Boeing's brand new Delta III was launched, only to fail within minutes in a spectacular night explosion.

In April, another pair of Titan IVs were sent aloft from the Cape. These booster rockets actually worked, but malfunctions of their last stages left their satellites marooned in useless orbits. Shortly thereafter, an Athena rocket fired from the military rocketbase at Vandenberg, Calif. fell into the Pacific when the cover over its imaging satellite failed to drop away. Shortly thereafter, the Delta III, making its second try for commercial success, failed again when its last stage shut down after just a second of thrust, making its satellite worthless space junk.

Causes of these rocket failures are still under investigation as of late July, but there might be at least one common link to two of these mishaps. That second Delta III failure was of the same rocket engine that was used in one of the April Titan failures, possibly linking these two accidents. But is still too early in the investigations to know for sure. That part, the Pratt and Whitney RL-10 engine system, has been flying on U.S. rockets for more than 35 years.

While that engine is so reliable that it is also used on the Delta III, versions of the Titan IV, and even the Atlas II and III, should it fail on any one of these vehicles it could effectively ground the others until the failure is better understood. One reason that the RL-10 is so popular is that there has been no other similar engine system developed during these decades. Why? Because for years most rocket development in the U.S. has centered around either smaller launchers like the winged Pegasus or the space shuttle. And, like Pegasus, the newest U.S. small rockets with names like Taurus and Athena have been made from missile designs from the Cold War era.

That lack of rocket engine development for most of the 1970's and 1980's has resulted in reliance by the industry on basically older systems. Only in the last several years, spurred by the Air Force's desire for slashing its launching costs, has the development of an entirely new throw-away rocket been given priority. But those new rockets won't be available until 2001 and won't become operational until 2002.