LSR ThrustSSC Report 97-10-02

Battle for Mach 1 on Land October 2nd was a seriously unproductive day. High winds blowing from the South had turned the Black Rock Desert into a gigantic sand storm for the second day running. The ThrustSSC team were poised to take the ...

Battle for Mach 1 on Land

October 2nd was a seriously unproductive day. High winds blowing from the South had turned the Black Rock Desert into a gigantic sand storm for the second day running.

The ThrustSSC team were poised to take the ThrustSSC car deeper into the transonic speed range- with targets of Mach 0.947 and Mach 0.961 for runs 55 and 56- but the onset of the high winds made this impossible despite the last minute running of two replacement 13 mile white gypsum track lines in 2 hours.

The ThrustSSC project is now at an interesting stage : The highest Mach Number achieved is Mach 0.935 and the ThrustSSC Engineering Team are happy to proceed further up the scale in small steps to Mach 1. At Mach 0.935 the team had been led to expect aerodynamic buffeting from the unstable airflow-but so far this has not been encountered. Driver Andy Green reports that the car feels more stable with the higher mach numbers.

Against this progress is the fact that the fall is rapidly approaching and with the onset of the colder weather the number of viable run days is reducing- and these run days have to be shared with the Spirit of America Team. The ThrustSSC project is also coming to the end of its Black Rock funding though there has recently been considerable interest in refunding in the UK with a number of sponsorship approaches received. Despite these obvious pressures, the team will continue to operate in carefully defined steps, always aware that decisions made in haste can lead to serious accidents.

The huge daily television audience approaching 100 million is likely to be back when Sky return with their live satellite link - and despite the extended down period the internet hits have not dropped below 750,000/day.

The weather forecast over the next 48 hours promises high pressure and fine running conditions. For tomorrow October 3rd, the coin toss for first run slot has been won by ThrustSSC and the team plan to roll -out at 0730am. Spirit of America is expected to run later in the day.

The Federation International Automobilistes has now agreed in principle to sanction the supersonic runs and from October 3rd the timekeepers will be reporting ThrustSSC ground speeds and provisional Mach Numbers.

Achievement of Mach 0.94 and Mach 0.96 tomorrow will put the ThrustSSC team in a strong position to progress to Mach 1 over the next week or so.


Additional Information - An Understanding of Speed.

The World Land Speed Record is a measure of ground speed- the same speed element as your car. Regardless of headwind or tailwind the speed measured by our USAC Timekeepers is the speed made by ThrustSSC as it transits the measured mile and measured kilometre. This is known as the ground speed- literally the speed ThrustSSC makes over the ground- the very same measure of speed you see on your car speedometer. We call this MPHG.

However, ThrustSSC is a high performance aerodynamic vehicle and the aerodynamic performance is very important to the overall performance of the car. If ThrustSSC is being driven to a defined groundspeed , but into a headwind- then the airspeed will be higher than the ground speed. If there were a tailwind then the airspeed would be less than groundspeed.

The airspeed is read off the ThrustSSC airspeed indicator which takes into account the dynamic air pressure at the pitot- the shiny piece at the end of the boom on the ThrustSSC nose. Because of altitude effect here at Black Rock- the indicated airspeed is always lower than the ground speed. Indicated airspeed is called MPHI.

The third element is the Mach No. Named after the Austrian scientist Ernst Mach- the Mach No is the ratio of the airspeed (MPHI) to the local speed of sound. So Mach 0.80 is 80% of the speed of sound. Now the speed of sound varies with temperature and the following figures may prove helpful:

Temp C                      Temp F                Local Speed of Sound-mph
0                        32                        741.1
5                        41                        747.9
10                        50                        754.6
15                        59                        761.2
20                        68                        767.8
25                        77                        774.3
30                        86                        780.7

As the Thrust project pushes on towards Mach 1 , the sound barrier, Andy Green is asked by the Engineering Team to drive accurately to Mach Number which is indicated in the cockpit.Thus for a given Mach Number target speed, on a cold day the ground speed will be lower- and on a hot day the ground speed will be higher for the same Mach No. If there happens to be a tailwind on a hot day, then Andy will be driving at an even faster ground speed to achieve the target Mach No. for the run.

Keeping up to Speed with Thrust SSC Internet at

Info line on (44) 0839-888-850

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Series General
Drivers Andy Green