SPACE LAUNCH VEHICLES



ASLV - Augumented Satellite Launch Vehicle

Line drawing of the ASLV

(Source: ISRO)

 

 

Keeping in view the long-term goal for realizing polar and geo-synchronous launch capability for operational class of satellites, development of Augmented Satellite Launch Vehicle (ASLV), was undertaken to act as a low cost intermediate vehicle for demonstrating critical technologies.

ASLV was configured as a five-stage solid propellant vehicle, weighing about 40 tonne and having a length of about 23.8 m. The strap-on stage consisted of two identical 1 m diameter solid propellant motors similar to SLV-3 first stage, other stages being the same as in SLV-3. The payload capability was thus raised to 150 Kg as compared to SLV-3's 42 Kg capability. Closed loop guidance, active from the ignition of the second stage motor to the separation of the third stage, was employed in ASLV while SLV-3 had used an open loop system.

Four Developmental (= D) launches were planned. The ASLV program series was limited to 4 to master solid fuelled booster clustering and other critical technologies before embarking on mainstream PSLV launchers that are much more larger and complex.

ISRO's limited budget and capability however could not simultaneously sustain ASLV & PSLV programs. Thus limiting the ASLV as a proving ground, rather then as niche market commercial launcher.



ASLV Rocket Configuration:


First Launch Date: 24 March 1987. Last Launch Date: 04 May 1994. LEO Payload: 150 kg. to: 400 km Orbit. Liftoff Thrust: 92,780 kgf. Total Mass: 41,000 kg. Core Diameter: 1.0 m. Total Length: 23.5 m. Flyaway Unit Cost $: 9.00 million. in 1985 unit dollars.

 

 

ASLV-0

(AS0)

ASLV-1

(AS1)

ASLV-2

(AS2)

ASLV-3

(AS3)

ASLV-4

(AS4)

Payload Faring

Gross_Mass

Fuel_Mass

Empty_Mass

(StageFuel- Mass-Ratio)

10,600 Kg

8,637 Kg

2,963 Kg

(0.745)

10,800 Kg

8,900 Kg

2,900 Kg

(0.754)

4,400 Kg

3,200Kg

1,200 Kg

(0.727)

1,710 Kg

1,060 Kg

650 Kg

(0.620)

512 Kg

317 Kg

195 Kg

(0.619)

150 Kg

 

Motor Fuel-Mass-Ratio [19]

0.851

0.851

-

0.875

-

N.A.

Thrust@Vacuum

Thrust@Sea_Level

(Burn_Time)

51,251 Kgf

46,390 Kgf

(49 sec)

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 [20]

 

253 sec

229 sec

 

259 sec

232 sec

 

276 sec

220 sec

 

277 sec

190 sec

281 sec

110 sec

N.A.

Length

Diameter

11.0 m

1.0 m

10.0 m

1.0 m

6.35 m

0.8 m

2.44 m

0.815 m

1.4 m

0.657 m

3.27 m [21]

1.0 m

Chamber Pressure [22]

Expansion Ratio

44.1 bar

6.5:1

44.1 bar

6.7:1

38.3 bar

14.2:1

44.1 bar

25.7:1

29.4 bar

28.6:1

N.A.

Propellant

Chemical

Case material

Solid

HTPB 15CDV6

Steel

Solid

HTPB 15CDV6

Steel

Solid

HTPB 15CDV6

Steel

Solid

HEF20/AP/Al

Graphite Epoxy

Solid

HEF20/AP/Al

Graphite Epoxy

 

 

Aluminum Alloy

Number of Engines

(Number of Segments)

2

(3)

1

(3)

1

(1)

1

(1)

1

(1)

N.A.

 

Stages of the ASLV

 

1. ASLV Strap-ons (AS-0)


The two strap-ons that ASLV has, employ the same motor as its main stage 1. Further, the motor for both the strap-ons and stage 1 of ASLV is derived from the stage 1 of SLV-3. However, the nozzles on the strap-on motors are canted at 9 degrees, while those on the main stage are not.


2. ASLV Stage 1 (AS-1)

ASLV's stage 1 is an uprated version of SLV-3's first stage. Stage 1 ignites at 49.5 sec following strap-on burnout at 49.2 sec (timings could vary and depend on realtime decision). The nozzles in stage 1 incorporate secondary injection ports for TVC.

3. ASLV Stage 2 (AS-2)

Again, stage 2 motor is an upgraded version of SLV-3's stage 2 motor. Certain changes in the solid fuel composition were made. The same grain configuration as SLV-3 was retained, but the aluminum content was raised from 12% to 18% accompanied by a thickening of carbon phenolic ablative material to combat increased erosion.

4. ASLV Stage 3 (AS-3)

This is the only ASLV motor applied directly from its predecessor SLV-3.

5. ASLV Stage 4 (AS-4)

Again an upgraded version of SLV-3 stage 4. Stage mass reduction was achieved with Kevlar 49 replacing glass fiber reinforced plastic as the casing material. Propellant mass was increased 45kg by slight case stretching and was compensated for by recontouring to a shorter nozzle.

 

Technical Drawing for the SLV3 and ASLV

(click on image for High Resolution Image)

ASLV Flights:

ASLV-D1

Flight date & time: 24 March1987
Payload: SROSS A, 150 Kg

Flight sequence, result and discussion:Failure.

The core AS-1 stage did not ignite following strap-on burnout. The investigation board attributed it to either a loose connection or a random failure [23] .

ASLV-D2

Flight date: 12 July1988
Payload: SROSS-B, 150 Kg

Flight sequence, result and discussion: Failure

AS-1 stage ignited after 49.8 sec instead of 49.5 sec following strap-on burnout at 49.2 sec. After a detailed failure analysis it was determined that wind shear prevented the control systems from converging the guidance (i.e. Insufficient control gain) and the upper stages broke away. A number of corrective actions were taken, many of them relating to the transition between the strap-on stage and the first stage included a redesigned autopilot and motor changes to reduce dynamic pressure[24]. They also included better characterization of vehicle, improved stability, introduction of on-board detection of flight events and extensive simulations[25].


ASLV-D3

Flight date: 20 May 1992, 00:30 GMT
Payload: SROSS-C, 106 Kg (carrying a Gamma- ray burst detector and an astronomy payload)

Flight sequence, result and discussion:Partial Failure.

Orbit: 255 x 430 Km, Inclination: 46 Low perigee resulted in rapid orbit decay, it re-entered atmosphere on 14 July 1992.
The payload achieved orbit but AS-4 did not fully spin up, resulting in a low perigee. However, this flight validated all the corrective actions in the design of ASLV[26]. The satellite spin period was 10.6 sec.

ASLV-D4

Flight date: 04 May 1994, 00:00 GMT
Payload: SROSS-C2, 113 Kg

Flight sequence, result and discussion:Successful launch.

Orbit: 437 x 938 Km, Inclination: 46.2


 


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