• •The Buran spacecraft utilized four primary flight computers to manage its automated landing systems
• •A quad-redundant system prevents a 'tie-breaker' paradox that occurs in three-computer setups when one unit provides conflicting data
• •It remains unclear how the software effectively reconciled simultaneous input discrepancies between the four independent machines during the 1988 flight

The Soviet Buran space shuttle utilized a four-computer architecture rather than a more common triple-modular redundancy configuration. While triple systems are standard in aerospace, they struggle to determine which unit is faulty when one of the three disagrees with the others. By using four, the system ensures a majority vote even if one computer fails entirely and another provides erroneous data. Whether this complex voting logic introduced latent bugs that were never triggered in its singular, uncrewed 1988 mission remains a subject of debate among modern systems engineers.