The Impact of Selling the Federal Helium Reserve by National Research Council

Author:National Research Council
Language: eng
Format: epub
Tags: Policy for Science and Technology
Publisher: NATIONAL ACADEMY PRESS
Published: 2000-05-23T00:00:00+00:00

Pressurizing and Purging

Helium plays a unique and critical role in the pressurizing and purging of primary rocket propulsion systems. It will continue to do so as long as the propellant is a combination of liquid hydrogen and liquid oxygen. First, helium gas is used to pressurize the propellant tanks for the engines. In this application, pressure is provided to prevent pump cavitation and must be sufficient to keep the tanks from collapsing under vehicle-imposed structural loads. Pressure-fed propulsion systems are also used to provide engine-chamber pressurization. Second, helium gas is used for the purging of the propellant feed systems for liquid-hydrogen engines. Helium is used because its normal boiling point is lower than that of hydrogen. Thus it is the only element that can be used without compromising propellant integrity or feed-system function. Other gases would freeze, producing particles that could clog equipment and seize an engine, or react with or dissolve in the liquid hydrogen, reducing engine efficiency, all with potentially disastrous results.

The use of liquid and gaseous helium for pressurizing and purging rocket propulsion systems by the aerospace industry and the National Aeronautics and Space Administration (NASA) amounted to about 470 million scf (13 million scm) of helium in 1996. Large-scale aerospace uses of helium are expected to increase over the next 20 years, as the space shuttle is used to construct and service the International Space Station. There is no question that past successes in space exploration and the associated technology have been partially enabled by access to substantial supplies of helium. Because aerospace use is such a large fraction of overall usage, attention must be paid to developing alternative approaches to helium-based pressurizing and purging or, where there are none, recycling procedures. There has been little incentive thus far to conserve helium in large-scale aerospace use. However, aerospace engineers are focusing their attention on future space access vehicles that do not depend on cryogenic propellants. If the uses of noncryogenic propulsion systems increase, the demand for helium as a pressurant will decrease.

It should be noted that the rocket industry also uses significant amounts of helium for welding, cooling scientific payloads, refrigerating fuel-handling systems to liquid-hydrogen test temperatures, and as a pneumatic control system fluid in spacecraft and other rocket-propelled systems. NASA's current combined use of liquid and gaseous helium for all purposes amounts to the equivalent of 150 million scf (4.2 million scm) of gaseous helium per year.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.