The Diamant A had a number of innovative aspects for its day which might be applicable to small launch vehicles. It had one of the first multinozzle solid motors with gimballing nozzles. It used a solid gas generator to pressurize the first stage liquid propellant tanks. The first stage motors were extremely simple, as liquid motors go, utilizing a graphite throat and film cooling. The Diamant rockets had no guidance system, only a control system, and were guided from the ground.
The Diamant A rocket was a final unifying effort from a multiple step development process. Each of the stages was tested in a separate sounding rocket program. Stage 3 and the Payload shroud were tested separate from the Diamant vehicle as the Rubis sounding rocket, Stage 2 was tested in the Topaz sounding rocket and stage 1 was tested in the Emerald and Saphire
PERFORMANCE ESTIMATES
The following table is an estimate of the performance of each stage and the vehicle, as a whole. The nose cone was ejected about 10 seconds into the flight of stage 2 so that stage is broken into two performance phases.
STAGE 1
Stage 1 was a pressure-fed liquid propellant stage with 21372 lb-m of Nitric Acid as the oxidizer and 6512 lb-m of Turpentine as the fuel. A 250 lb-m slug of furfuryl alcohol in the fuel lines ignited the propellants. This stage used a unique solid-propellant pressurization system whereby hot gasses from a solid gas generator plus steam generated from water coolant were used to pressurize the propellants to about 320 PSI.
The pressurized propellants were burned in the Vexin rocket motor which provided an average of about 69690 lb-f of thrust. The Vexin motor design was quite simple and used a graphite throat with film cooling. The following image shows the general plan of the motor. The motor was basically a steel tube and nozzle with a graphite throat. It also had a radial injection system, not seen on many other motors.
| VEXIN MOTOR | |
| OF Ratio | 3.16 |
| Oxidizer | Nitric Acid |
| Fuel | Turpentine |
| Chamber Pressure | 255 PSI |
| Sea Level Thrust | 63620 lb-f |
| Vacuum Thrust | 72929 lb-f |
| Sea Level Isp | 203 sec |
| Vacuum Isp | 233 sec |
| wdot | 313 lb/sec |
| Expansion Ratio | 3.6 |
| Length | ~ 72 in |
| Throat Diameter | 15.9 in |
| Nozzle Exit Diameter | 30.2 in |
| Engine Weight | 816 lb |
| Thrust:Weight Ratio | 85:1 |
STAGE 2
The Diamant's second stage utilized a solid rocket motor with four steerable nozzles. This motor provided about 33,700 pounds of thrust for about 44 seconds. The propellants were based on polyurethane binder with aluminum fuel and ammonium perchlorate as the oxidizer; this mixture had a trade name of "Isolane." The nozzles were offset from their rotation axis such that by rotating them, the nozzles could direct the thrust off-axis. Hydraulic pistons rotated each nozzle; by coordinating the nozzle rotation, the thrust could be directed as desired for pitch, yaw and roll control.
Design of Nozzles
STAGE 3
Stage 3 is a 275 RPM spin-stabilized vehicle utilizing a 25.6 in (650 mm) diameter by 82 inch (2100 mm) long solid rocket motor called P0.64. Powered by the same "Isolane" propellant as the second stage, the motor had a peak thrust of 11690 lb-f for an average thrust of about 8573 lb-f; it burned for about 45 seconds with an average Isp of 273 seconds. It had a 3.78 inch (96mm) graphite throat and the chamber pressure varied from a low of 20 atmospheres (290 PSI) to 40 atmospheres (594 PSI) during its burn time.
AERODYNAMIC LOSSES
Simulations of the flight indicate that there is an aerodynamic loss of 459 feet per second for both stages 1 and 2. About 451 fps was lost to aerodynamics for stage 1 and about 8 feet per second was lost in stage 2.
GRAVITY LOSSES
Flight simulations indicate that there is about 4041 feet per second of gravity losses during the flight of stages 1 and 2. Stage 1 saw gravity losses of about 2715 fps and stage 2 saw gravity losses of about 1326 fps.
GUIDANCE
The Diamant A had no on-board guidance system, only an on-board control system utilizing gyroscopes for orientation control. Ground based tracking systems with an uplink control signal provided the guidance for the Diamant A launch vehicle.
REFERENCE
- Capcom Space [http://www.capcomespace.net/]
- Villain, J. "The Evolution of Liquid Propulsion in France in the Last 50 Years" Acta Astronautica Vol 22, 1990.
- Truchot, Mr A. "Design and Analysis of Solid Rocket Motor Nozzle," Agard Lecture Series 150, Design methods in Solid Rocket Motors, 1988.
- Uhrig, G.; Boury, D.; "Large Space Solid Rocket Propulsion in Europe Past and Future Developments," AIAA 1998-3980, AIAA 1998.
- Jung, Phillipe; Serra, Jean-Jacques; "VE 210 Rubis: Sounding Rocket on the Road to Space," IAC-05-E4.3.02, International Astronautical Federation 2005.
- DIAMANT A ROCKET, France's space agency, the CNES in 60'S [VIDEO] YouTube.
