  Current research in High Energy Cosmic Ray Physics touches on fundamental
questions regarding the origin of cosmic rays, their composition, the
acceleration mechanisms, and their production. Unambiguous measurements of the
energy spectra and of the composition of cosmic rays at the "knee" region could
provide some of the answers to the above questions. So far only ground based
observations, which rely on sophisticated models describing high energy
interactions in the earth's atmosphere, have been possible due to the extremely
low particle rates at these energies. A calorimetry based space experiment that
could provide not only flux measurements but also energy spectra and particle
identification, would certainly overcome some of the uncertainties of ground
based experiments. Given the expected particle fluxes, a very large acceptance
is needed to collect a sufficient quantity of data, in a time compatible with
the duration of a space mission. This in turn, contrasts with the lightness and
compactness requirements for space based experiments. We present a novel idea
in calorimetry which addresses these issues whilst limiting the mass and volume
of the detector. In this paper we report on a four year R&D program where we
investigated materials, coatings, photo-sensors, Front End electronics, and
mechanical structures with the aim of designing a high performance, high
granularity calorimeter with the largest possible acceptance. Details are given
of the design choices, component characterisation, and of the construction of a
sizeable prototype (Calocube) which has been used in various tests with
particle beams.
