In-orbit emergencies

In-orbit anomalies posing a serious threat to the crew could have resulted in any of three abort scenarios: “Immediate Return’’, “Early Return’’, or rescue by a Soyuz spacecraft. Buran crews would have had checklists instructing them what to do in each of those situations.

Immediate Return

“Immediate Return’’ was an abort scenario requiring Buran to deorbit between 40 minutes and 3 hours after the occurrence of the anomaly. Forty minutes was considered the minimum time needed to complete all preparations for re-entry such as closing of the payload bay doors, preparing hydraulic systems, donning pressure suits, and loading re-entry software into the on-board computers. One anomaly likely to result in an Immediate Return was considered to be a serious fire in the crew compartment not disabling the vehicle or the crew. After extinguishing the fire with available means, the crew would have donned their Strizh pressure suits to prevent smoke inhalation. If the fire threatened to go out of control after the crew had put on the suits, the crew also had the option of depressurizing the cabin to starve the flames of oxygen. Another such anomaly would be a sudden leak in the ODU propulsion system that within a short period of time would lead to an inability to fire the deorbit engines or position the ship for a Soyuz rescue mission, stranding the crew in orbit.

“Immediate Return’’ could only end with a safe runway landing if the vehicle’s ground track happened to carry it over one of the three available Soviet landing sites within a short time after the occurrence of the anomaly. If this was not the case, the crew would have had to eject from Buran before it crash-landed. Factors to be taken into account here would have been the need to protect public safety and have rescue crews within a reasonable distance of the landing zone (especially if the vehicle had to be ditched in the ocean).