The fatal mishap with Virgin Galactic’s Spaceship Two on October 31, 2014, caused by premature unlocking of the feather system by the co-pilot, revealed some serious shortcomings of the flight simulators used to prepare pilots for suborbital spaceflights (Barbara Kanki, Space Safety Magazine, July 29, 2015): “While crews may have practiced normal and non-normal procedures in a full mission scenario, many critical aspects of the operational environment were missing, including vibration and g-forces as well as elements of time pressure […]. When present, such conditions may result in much greater workload and stress than what would be experienced in a flight simulator.” This tragic incident, killing one pilot and injuring the other, stresses the need for new-generation simulators that better replicate the operational environment.

The first-of-its-kind simulator DESDEMONA at TNO (Soesterberg, the Netherlands) offers such capability. Featuring an all-attitude cabin, a centrifuge and a horizontal and a vertical track, the simulator is capable of reproducing the operational environment with respect to higher g-forces, vibrations, and extreme attitudes. It is now being used to familiarize future spaceflight participants with the typical g-forces of suborbital spaceflight. The simulated flight profile represents a winged vehicle that takes off horizontally from a spaceport, accelerates with 2g (“eye balls in”) to Mach 3, unloads to simulate weightlessness while enjoying an outside view of the Earth, and finally pulls more than 3g (“head-to-feet”) for 20 seconds during the re-entry in the atmosphere. For untrained participants, the latter phase of increased g-forces is most challenging as it drains blood from the brain, which may lead to a blackout or even g-induced loss-of-consciousness (G-LOC). For flight crews, the increased g-forces result in higher workload and may also induce spatial disorientation, daring their perception of “up” and “down”. Spatial disorientation is the dreaded cause of Controlled Flight Into Terrain (CFIT), and Loss Of Control In-flight (LOC-I), the two biggest killers in military and commercial aviation today. Clearly, suborbital flight crews should be specifically trained to recognize the various types of spatial disorientation that they may encounter in-flight.

DESDEMONA (acronym for DESorientation DEMONstrator Amst) was co-developed in the 2010s by AMST Systemtechnik GmbH (Austria) and TNO to reproduce specifically those flight conditions that lead to spatial disorientation and loss of control. The cockpit is equipped with an 180×40 degrees out-the-window visual display, cockpit instruments, and flight controls. With the appropriate simulator model, a pilot can fly spaceflight-in-the-loop scenarios and get realistic motion feedback from the advanced motion platform. This way, pilots can practice non-normal flight conditions before experiencing them in real flight. This approach is already successfully being applied for military pilots, allowing them to practice flight conditions that are either very rare, or too dangerous or expensive to train in flight. An example of such training is the recovery from an inverted deep stall of an F-16, where DESDEMONA’s cabin is actually being inverted and rocking equally to the aircraft. Being inverted not only causes spatial disorientation in the pilot, it also makes the recovery much more demanding than is the case in a conventional simulator. Another example is the simulation of unusual attitudes, and other “upsets”, of transport aircraft. This offers the opportunity for commercial pilots to experience the non-normal aircraft behavior associated with an aerodynamic stall, including the strong vibrations due to “buffeting” of the wing. As buffeting is an important warning signal for an impending stall, it is essential to accurately reproduce these vibrations in the simulator.

In comparison to conventional aircraft, suborbital spaceflights involve even more extreme motions and attitudes. This poses special requirements for the simulator training of their flight crews. The accident with Space Ship Two underlines this. Currently, the industry seems to make use of standard flight simulators that are very limited in reproducing the physical environment of suborbital spaceflight. With the advanced DESDEMONA simulator, suborbital pilots can practice normal and non-normal procedures in an environment under realistic workload. A groundbreaking space era calls for groundbreaking simulator technologies.

-F16 flight simulation

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-Suborbital flight simulation

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About the author

Eric Groen

Eric Groen has a background in human physiology, and received a Ph.D. on his research into the Space Adaptation Syndrome in astronauts. Currently he works as senior scientist at TNO, with a strong interest in spatial disorientation, loss-of-control in-flight, and simulation of non-normal flight conditions, including suborbital spaceflight. Eric has been teaching spatial disorientation awareness training for more than 10 years, and provides anti-air sickness training to pilots.

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