The related "dinitrodiglycol", more properly termed diethylene glycol dinitrate in modern notation, was widely used in World War 2 Germany, both alone as a liquid monopropellant and colloidal with nitrocellulose as a solid propellant. The otherwise desirable characteristics of this compound; it is quite stable, easy to manufacture, and has a very high energy density; are marred by a high freeze point (-11.5 deg. C) and pronounced thermal expansion, both being problematic in spacecraft. "Dinitrochlorohydrin" and "tetranitrodiglycerin" are also likely candidates, though no current use is known. The polynitrates of long chain and aromatic hydrocarbons are invariably room temperature solids, but many are soluble in simple alcohols or ethers in high proportion, and may be useful in this state.