HS2, IMechE, and the Bloodhound SSC

A power station building programme costing more than HS2 would become essential

“We estimate that about 60kWh/seat-km of energy would be needed at 360kph, compared to about 50kWh/seat-km at 320kph. Average speeds are assumed to be 75% of maximum; at an average speed of about 240kph (75% of the Institution's proposed maximum 320kph) we estimate that about 34kWh/seat-km would be required compared to about 46kWh/seat-km at 270kph (75% of 360kph).”

These two sentences in the Institution's Transport Policy Statement 10/01 “High Speed Rail 2” have many truly amazing implications.  

For the 174km between London and Birmingham 34kWh/seat-km would mean, even at a low 5p/kWh, nearly £300/seat for energy alone. Raising the top speed to 360km/h at 46kWh/seat-km would cost £100/seat extra. Those on the National Minimum Wage would need to work for twenty hours to save two minutes.

50kWh/seat-km at 320km/h would mean 16MW/seat or 8GW per 500 seat train and, at 25kV, a contact wire current of 320kA. Unfortunately, that is at least a hundred times the current rating of conventional contact wire. Furthermore, HS2's 61 train fleet would have, apparently, a potential demand of nearly 500GW. Since the National Grid's present total capacity is only 89GW, a massive power station building programme costing many times that of HS2 itself would become essential.

At constant speed on the level, kWh/km is train resistance at the pantograph rather than at the wheel. Even at one tonne per seat, 50kWh/seat-km implies train resistance of 180kN/seat or 18 tonnes wt./seat. This would rule out an adhesion railway, even one using rubber tyres, so perhaps HS2 will be the world's first high speed rack railway. The single seat Bloodhound SSC, however, is expected to reach 1050mph with 122kN thrust.  Its resistance would be, apparently, a third lower at five times the speed.

David J.A. Hobbs

Next letter: The red herring