Abstract
In the light of recently revived interest in high energy density fuels for aerospace applications1,2), a new look is being given at unconventional fuels. Among the latter are hydrides, because their hydrogen content and density. Among hydrides silanes are of interest because of their combustion and energetic properties.
Silanes are silicon hydrides organized in molecular chains similar to those of hydrocarbons; at STP, lower silanes (SiH4, Si2H6) are gaseous and extremely pyrophoric; with increasing chain length, silanes become liquid from trisilane (Si3H8) on, and therefore easily pumped. Another important feature of silanes is the large amount of hydrogen theoretically available by thermal decomposition: in fact at moderate temperatures (about 500 K) the chains begin to break and at 700 K their decomposition is complete, yielding silicon and gaseous hydrogen, useful for propulsion in combination with air nitrogen and oxygen. This last feature, if confirmed, could identify silanes not only as energy carriers but also components in bi-fuel systems. To assess their theoretical performance, simulations were conducted assuming silanes and/or their thermal decomposition products in combination with various oxidizers and air. Preliminary results are suggestive of their potential for some specialized applications, especially where compactness is at premium.
