Stretch receptors in the blood vessels of his neck will detect the increase in pressure, and activate the baroreceptor reflex. While the Car is accelerating, the high blood pressure in Andy’s head will fool his body into making physiological changes to his heart and blood vessels to prevent any further rise in blood pressure. Although 3G is not usually enough to cause greyout when flying in an aircraft, the situation in the Car is slightly unusual because of the rapid G reversal that happens between acceleration and deceleration. This will throw him forward firmly into his harness, and blood will drain to his legs, which will reduce the blood pressure in his head. When he slows down he will briefly experience up to 3G in the opposite direction. The force in this direction will also increase the blood pressure in his head, which may be a little uncomfortable, but will not carry any risk of losing consciousness.Ĭar decelerating – blood forced to the feet As the Car accelerates, a force of around 2.5G will push him hard back into his seat. G Forces in the Carĭue to Andy’s very reclined seating position in BLOODHOUND SSC, the G force he will experience when the Car accelerates will be in a different direction to that he would usually feel when turning in an aircraft. The Typhoon is capable of sustaining turns of up to 9G, requiring the pilots to use a full-coverage anti-G suit and positive pressure breathing for G protection. It also includes positive pressure breathing which provides pressurised breathing gas when the G level is increased to raise blood pressure. The system includes full-coverage anti-G trousers which compress the legs to increase blood pressure and aid return of blood to the heart.

For cutting-edge fighter aircraft such as the Typhoon, this requires an advanced anti-G system to keep pilots conscious at up to 9G. This causes dimming of vision (greyout) as the eye is starved of oxygen and, at higher G levels, loss of consciousness due to lack of oxygen in the brain. At a certain G level, this effect is so strong that not enough blood gets to the head. G Induced Loss of Consciousnessīecause the blood in the arteries and veins gets heavier, pulling high G in an aircraft reduces blood pressure above the heart (and blood pressure in the legs is increased). This makes them feel heavy, and movement becomes difficult. When pilots ‘pull G’, they feel a force greater than gravity (for example, 3G is three times Earth’s gravity). For the technically minded, what is responsible is actually an acceleration caused by the mass of the planet, which draws us towards it at 9.81m.s-2. So, when we are standing upright we are exposed to 1G. We measure G force in multiples of Earth’s gravity, as this is something we are all familiar with. This force pushes them downwards into their seats as their bodies literally become heavier.

RAF pilots experience the same thing in their aircraft when turning quickly. The most important thing is G force, which will be produced when the Car speeds up and slows down.

He will be shaken, compressed, disorientated, deafened and heated, but these are all in a day’s work for a pilot. The forces that driver Andy Green’s body will be exposed to in BLOODHOUND SSC are not unlike those he has been trained to deal with as a fighter pilot. By Wing Commander Nic Green, Chief Research Medical Officer, Royal Air Force Centre of Aviation Medicine

Positive and negative g force in a car