  Gamma ray bursts (GRBs) are the most energetic eruptions known in the
Universe. Instruments such as Compton-GRO/BATSE and the GRB monitor on BeppoSAX
have detected more than 2700 GRBs and, although observational confirmation is
still required, it is now generally accepted that many of these bursts are
associated with the collapse of rapidly spinning massive stars to form black
holes. Consequently, since first generation stars are expected to be very
massive, GRBs are likely to have occurred in significant numbers at early
epochs. X-red is a space mission concept designed to detect these extremely
high redshifted GRBs, in order to probe the nature of the first generation of
stars and hence the time of reionisation of the early Universe. We demonstrate
that the gamma and x-ray luminosities of typical GRBs render them detectable up
to extremely high redshifts (z~10-30), but that current missions such as HETE2
and SWIFT operate outside the observational range for detection of high
redshift GRB afterglows. Therefore, to redress this, we present a complete
mission design from the science case to the mission architecture and payload,
the latter comprising three instruments, namely wide field x-ray cameras to
detect high redshift gamma-rays, an x-ray focussing telescope to determine
accurate coordinates and extract spectra, and an infrared spectrograph to
observe the high redshift optical afterglow. The mission is expected to detect
and identify for the first time GRBs with z > 10, thereby providing constraints
on properties of the first generation of stars and the history of the early
Universe.
