Madhav Sonkusare

Project AGNI

A KNSB solid rocket motor that thrustMIT designed, cast and fired itself, aimed at a 10,000 ft rocket. The first M-class test failed 1.63 s in. The rebuilt motor held for the whole burn and delivered 9,202 N·s.

RolePropulsion Lead

  • 9,202 N·s total impulse
  • 2,163 N average thrust
  • 129 s specific impulse
  • 7.25 kg KNSB
Project AGNI, rendered in section

Inside AGNI

Forward closure

Two O-ring seals and an independent retainer ring secure the forward closure.

Material
Al 6061-T6
Seals
2 O-rings
Retention
Retainer ring

Propellant grains

Four KNSB grains, together they hold 7.25 kg of propellant.

Grains
4 × 165 mm
Bore
Ø32 mm
Mass
7.25 kg

Casing and liner

An aluminium casing with a carbon-fibre liner that serves as the casting sleeve and thermal barrier.

Casing
Al 6061-T6 · 6 mm wall
Liner
CFRP · 3 mm

Nozzle

A converging-diverging nozzle with two O-rings and an independent aft retainer.

Seals
2 O-rings
Retention
Aft retainer ring
  1. Forward closure. Two O-ring seals and an independent retainer ring secure the forward closure.
  2. Propellant grains. Four KNSB grains, together they hold 7.25 kg of propellant.
  3. Casing and liner. An aluminium casing with a carbon-fibre liner that serves as the casting sleeve and thermal barrier.
  4. Nozzle. A converging-diverging nozzle with two O-rings and an independent aft retainer.
Section view of the AGNI motor, forward end at the top

  1. Forward closure

    Two O-ring seals and an independent retainer ring secure the forward closure.

  2. Propellant grains

    Four KNSB grains, together they hold 7.25 kg of propellant.

  3. Casing and liner

    An aluminium casing with a carbon-fibre liner that serves as the casting sleeve and thermal barrier.

  4. Nozzle

    A converging-diverging nozzle with two O-rings and an independent aft retainer.

Static fire

Agni 2.0, M class, front camera, 7 October 2024: the motor held for the whole burn. Slowed down.
Agni 1.0, 6 November 2023: ignition, then the failure 1.63 s into the burn. Slowed down.
we also tested a J-class motor that day cuz why not...

Project goal

Develop and validate an M-class motor for thrustMIT’s entry in the 10,000 ft student-researched and developed (SRAD) category.

  • 10,000 ft SRAD category
  • Student-designed hardware
  • J-class prototype → M-class programme
  • Static-fire validation

Design evolution

2023

AGNI 1.0

  • 3 propellant grains
  • SS 304 closure bolts
  • Single O-ring seals
  • Closure and nozzle bolted directly
AGNI 1.0 Fusion model with its closure, casing and nozzle separated.
2024

AGNI 2.0

  • 4 propellant grains
  • Class 12.9 fasteners
  • Redundant O-ring seals
  • Forward & aft retainers
  • Staggered bolt configuration
AGNI 2.0 Fusion model in an exploded view showing the added forward and aft retainers.
2023

AGNI 1.0

  • 3 propellant grains
  • SS 304 closure bolts
  • Single O-ring seals
  • Closure and nozzle bolted directly
AGNI 1.0 Fusion model with its closure, casing and nozzle separated.AGNI 2.0 Fusion model in an exploded view showing the added forward and aft retainers.
2024

AGNI 2.0

  • 4 propellant grains
  • Class 12.9 fasteners
  • Redundant O-ring seals
  • Forward & aft retainers
  • Staggered bolt configuration
  • ≈30% lower peak casing stress · FEA
  • Retainers share the closure loads
  • Full static burn without structural failure

Published failure analysis and redesign study ↗

Casting

  • 4 grains
  • 7.25 kg cast propellant
  • 0.93 density ratio
  • Carbon-fibre liners
  • Centred coring rod
  • Casting checklists
FIG. 01CASTING FIXTURE
Core rod and knurled capUpper centring supportCast KNSB grainCarbon-fibre linerLower centring supportCasting base
Exploded view · grain and liner cut in half
Three cast propellant grains standing in black carbon-fibre liners, wrapped in cling film on a workshop bench
Agni 1.0's three grains in carbon-fibre liners, wrapped against moisture, Nov 2023
Four cast propellant grains in black liners, numbered 1 to 4, standing on paper on a workbench
The four numbered grains of Agni 2.0 after casting, October 2024

Testing

6 November 2023

AGNI 1.0

Failure at 1.63 s

  • Head bolts sheared
  • Forward seal failed
  • Contained by the test stand
October 2024

AGNI 2.0

Complete static burn

  • 9,202 N·s total impulse
  • 2,163 N average thrust
  • 129 s specific impulse
  • No structural failure
  • J-class motor tested as well
  • 1,229 N·s · J-class result
Two stainless steel bolts lying on a dark surface, each cut across its shank, with the shear planes marked
The stainless steel bolts that sheared on Agni 1.0, 6 November 2023
FIG. 02THRUST · LOAD CELL
Thrust against time for the M-class AGNI motor: a rise to a plateau near 4,900 N between 1.3 and 2.0 seconds, then a fall to about 600 N at 4 seconds.0.00.51.01.52.02.53.03.54.001,0002,0003,0004,0005,000Time (s)N≈ 4,900 N peak
Measured thrust of the M-class motor on 7 October 2024, from the load cell

Project Kali

After AGNI, the junior propulsion team built Kali, an N-class KNSB motor designed from everything the AGNI tests had taught us, and this time meant to fly.

Kali powered Varuna, thrustMIT’s first rocket on a student-developed motor, which flew at IREC 2026 in the 10,000 ft SRAD category.

  • N-class KNSB motor
  • Static fire · February 2026
  • Flew in Varuna · IREC 2026
  • 10,000 ft SRAD category
Kali, the junior team’s N-class motor, on the vertical test bed, February 2026.

Gallery

Ready for Livestream. ft. Avionic team in the tent

Links

Next

Solid Propellant Research

A reusable test motor for nitrate propellants beyond KNSB, proof-tested with water and static fired.

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