Solid Rocket Fuel Less Expensive, Easier to Store

Solid rocket fuel is among the most explosive and dangerous substances in the defense and space industries, but it was chosen for use in the boosters of the Space Shuttle because among other things it is cheaper and easier to store than liquid fuel, according to experts in the space industry.

Essentially, solid rocket fuel is made from four substances--the fuel, which is a finely ground aluminum powder, a catalyzing agent, an oxidizer and a binding agent that holds it all together, according to Ed Metal, a spokesman for Marshall Space Flight Center in Huntsville, Ala.

It was the highly volatile oxidizer, ammonium perchlorate, that was being produced at the plant that exploded at Pacific Engineering and Production Co. in Henderson, Nev., on Wednesday.

Unlike various forms of liquid fuel, the ingredients of which are kept separate until the actual moment that they enter an engine and begin to power it, solid fuel is premixed and put into huge containers that can be stored for long periods or stacked inside an engine or missile, ready for use at a moment’s notice.

There is, of course, danger in that, scientists say. A stray match or spark of any kind could ignite the solid fuel, and there would be no way of stopping it until it burned itself out. This was not the case in the Pacific Engineering blast, which involved only ammonium perchlorate.

However, if properly stored, solid fuel has advantages over liquid fuel. It will not evaporate or corrode its containers as will some of the ingredients of liquid fuel, it can generally be used in simpler engines and it is often somewhat less expensive.

In contrast, at least some liquid fuels tend to be more powerful. As to which is better, “a lot of it is very subjective” and depends on the use and circumstances, said Floyd Anderson, who manages the solid propulsion lab at the Jet Propulsion Laboratory.

Solid fuel looks something like black tar with the consistency of a rubber eraser and is typically manufactured in great quantities, scientists say. In the case of the space shuttle, about 1.1 million pounds of solid fuel is required to fill each booster, which is 149 feet long and 12 feet in diameter, according to NASA officials.

Whether Wednesday’s explosion in Nevada will slow down the space program is still unclear. NASA officials say Pacific Engineering was one of only two companies that have been producing the oxidizer.

However, a slowdown in the space program has meant enough of a backlog in supplies that officials at Kerr-McGee, an Oklahoma-based producer of ammonium perchlorate with a plant near Henderson, say they have enough material for at least three more flights. The compan2032170857officials decline to say by how much “for proprietary reasons,” a spokesman said.