Design and Stress Analysis of Extraterrestrial ... - The Black Vault

2.2. RADIOACTIVE ISOTOPIC SOURCES OF E:.ERGY
FOR EXTRATERRESTRIAL ROCKET-ENGINES
It is common knowledge that a large amount ol heat is given
off in the decay of radioactive materials. This heat can be successfully
used in a space power plant.
Most radioactive isotopes used are obtained artifically as
a result of neutron bombardment in ordinary energy reactors. As a
result of isotope decay, a monotonic decrease in thermal energy occurs
according to exponential law. These isotopes are simple and operationa
ly reliable. The great difference in decay rates allows us a
widc .hoice of energy sources for the most varied purposes.
However, power plants on radioactive isotopes have several
disadvantages. They are expensive as compared with reactor installations
since in order to obtain the isotope, uranium must be
consumed in reactors: isolation of the isotope is also a complex
and costly process.
Therefore, radiolsotopic power plants are advisable only at
low powers (less than a kilowatt). The use of isotopic elements
requires a number of safety measures.
Although the radiatiozn of a particles (protons) is comparatively
safe for man since it is extinguished in th'e materials of the
isotope itself and the ampoule, y-radlation (electromagnetic) and
$-radiation (eiectrons), which gives off y-bremsstrahlung during
collision with particles of matter, require protection.
An ampoule with an isotope must be hermetically sealed in such
a way that the seal is not destroyed in the event of a crash.
All a-radioactive isotopes in their decay products have gaseous
helium whose pressure, at the end of the service period, can reach
huge values which complicates the construction of the source.
189