The Fifth International Astronautical Congress: Summaries of a Selection of Papers Read at the Congress Held at Innsbruck on August 1–7, prepared by Eric Burgess, F.R.A.S.

Solid propellents can be useful for certain astronautical operations. The characteristics of these propellents are that they have a high total impulse to total rocket weight ratio, higher reliability, a tendency towards lower costs. The specific impulses are lower than for liquid propellents, about 180 to 200 seconds compared with 240 seconds.