The SLV-3 during it's first stage of take-off (Source: ISRO)

SLV project was started in early seventies and was designed to put 40 Kg payload into a 400Km circular orbit. SLV3 rocket had four solid-propellant rocket motors, interstages connecting the forward skirt of one stage with the rear skirt of the next stage, inertial guidance and control systems to steer the vehicle along a predetermined trajectory and a heat shield to protect the fourth stage and the satellite payload[11]. The SLV project was lead by APJ Abdul Kalam[12] who also had the additional responsibility for designing the fourth stage of the SLV. He had Dr VR Gowariker who was the expert in the field of composite propellant. MR Kurup the expert in propellant, propulsion and pyrotechnics. and AE Muthunayagam for high energy propellant. The forth stage required composite structure and required many innovations in fabrication technology. Prof. Curian, President of CNES (the French Centre Nationale de Etudes Spatiales) often visited ISRO for mutual peer review. CNES was developing Diamont Launch Vehicle and requested ISRO to develop Diamont's fourth stage. Diamont airframe had a different stage diameter that forced additional innovations for APJA Kalam's team. The common last stage motor was reconfigured and upgraded from a 250 Kg , 400mm diameter stage to 600 Kg, 650 mm stage. Incidentally when the stage was ready for delivery the French CNES cancelled the Diamont project. The stage was later re-configured for exclusive SLV3 use at 360Kg and 700mm. Amongst the 4 rocket stage the critical stages were the 8.6 tonne booster Stage-1 and high mass ratio apogee rocket motor (Stage-4) using high energy propellant.

The milestones consisted of :

• Development & qualification of all subsystems through sounding rockets by 1975
  
• Sub-orbital flight by 1976
  
• Final orbital flight in 1978

Wernher von Braun [13] during his visit to ISRO mentioned the American physiological complex of NIH (Not Invented Here) and said, "If you have to do anything in rocketry do it yourself", he commented, "SLV-3 is a genuine Indian design and you may be having your own troubles. But you should always remember that we do not just build on success, we also build on failure"[14].

SLV3-1

SLV3-2

SLV3-3

SLV3-4

Payload Faring

Gross_Mass

Fuel_Mass

Empty_Mass

(StageFuel- Mass-Ratio)

10,800 Kg

8,660 Kg

2,140 Kg

(0.802)

4,900 Kg

3,150Kg

1,750 Kg

(0.643)

1,500 Kg

1,060 Kg

440 Kg

(0.707)

360 Kg

260Kg

98 Kg

(0.728)

50 Kg

Motor Fuel-Mass-Ratio [16]

0.851

0.843

0.875

0.847

N.A.

Thrust@Vacuum

Thrust@Sea_Level

(Burn_Time)

51,251 Kgf

46,390 Kgf

(49 sec)

27,227 Kgf

-

(40 sec)

9,249 Kgf

-

(45 sec)

2.736 Kgf

-

(33 sec)

N.A.

Specific-Impulse

Isp@Vacuum Isp@Sea_Level

253 sec

229 sec

267 sec

216 sec

277 sec

190 sec

283 sec

60 sec

N.A.

Length

Diameter

10.0 m

1.0 m

6.4 m

0.8 m

2.3 m

0.815 m

1.5 m

0.657 m

2.2 m

0.8 m

Chamber Pressure [17]

Expansion Ratio

44.1 bar

6.7:1

38.3 bar

14.2:1

44.1 bar

25.7:1

29.4 bar

30.5:1

N.A.

Propellant

Chemical

Case material

Solid

PBAN/AP/Al

Steel

Solid

PBAN/AP/Al

Steel

Solid

HEF20/AP/Al

GFRP

Solid

HEF20/AP/Al

Composite

Phenolic glasses

Number of Engines

(Number of Segments)

1

(3)

1

(1)

1

(1)

1

(1)

N.A.