Material for the Egress Phase:

Critical Analysis of Aluminium for Possible Applications

in Lander of Mars Rover-II

Aditya Shankar (12052) (Methology)

Archit Agrawal (12153) (Suggestions)

Semanti Mukhopadhyay (12645) (Introduction)

Shivam Tripathi (12676) (Discussion and Conclusions)

For Science is Nothing but Perception..--Plato

Introduction and Objective

Mission Timeline

• Pre-Launch: Preparation for the mission, landing site

selection, assembly and testing, and delivery to Sri

Harikota

• Launch: Lift-off from Earth

• Cruise: Voyage through space

• Approach: Nearing the red planet Mars

• Entry, Descent, and Landing: Journey through the

martian atmosphere to the surface

• Rover Egress: Leaving the lander to begin exploration

• Surface Operations: Learning about Mars through the

day-to-day activities of the rovers4 Image source: http://mars.isro.gov/mer/mission/images/merl4.jpg

Landing/Egress Sequence

• An aeroshell and a parachute decelerate the lander through the Martian atmosphere.

• Prior to surface impact, retro-rockets are fired to slow the lander´s speed of descent, and airbags are

inflated to cushion the lander at surface impact.

• After its initial impact, the lander bounces along the Martian surface until it rolls to a stop.

• The airbags are then deflated and retracted, and the lander petals and rover egress aids are deployed.

• Once the petals have opened, the rover deploys its solar arrays, and places the system in a safe state.

Lander Design

• The component of main importance in the Lander

Petal.

• Lander Petal: Retraction system that slowly drag the

airbags

• toward the lander to get them out of the path of the

rover.

• Small ramps or “ramplets”, connected to the petals

fan out and create "driving surfaces" that fill in large

spaces between the lander petals.

• Ramplets nicknamed “Batwings”

Motivation for Present Work

• Ramplet Design: Requisite Properties

• Strong enough to bear shock and stress during landing at low

temperatures.

• Must be able to cover dangerous, uneven terrain, rock obstacles,

and leftover airbag material that could get entangled in the rover

wheels.

• The rover must not succumb to stresses even when it bangs its

belly on a rock or smashes into the ground as it was moving off

the lander.

• Resistance to collision by high speed particles in atmosphere

• Withstand extreme temperatures.

Material Under Scrutiny:

Metals!!

Metal Required??

High Stiffness, High

Ductility, Low Specific

Volume, High Strength,

High Impact Toughness

Processing Required??

Grain Size Engineering

Effect of grain size on the Yield strength and Young’s

modulus of elasticity of metallic material

• Producing a relationship between grain size and yield strength of metallic

material by Hall-Petch equation.

Methodology:

• 1)Sample Preparation:

• Firstly we need to prepare samples with a range of different grain

size, d.

• We will do this by deforming (rolling) a plate by different amount,

cutting samples at each stage.

Methodology:

• We will then anneal the sample to fully recrystallize them.

• Heavily deform samples should recrystallize to a final grain size

• After measuring a grain size , We will do Vicker’s Hardness measurements on each ,

and convert hardness to yield stress and will end up with a relationship between

grain size and yield strength and Young’s modulus of elasticity

2)Vickers Hardness Test:

Observation:

Grain Size d(micrometre) Yield Stress (Mpa)

3.4 365.0

5.6 343.2

11.2 269.6

21.0 240.4

Discussion And Conclusion:

• We need materials having High Stiffness, High Ductility, Low Specific

Volume, High Strength, High Impact Toughness

• As per experiment lower the grain size higher will be the yield strength

• Also firstly Young’s modulus of elasticity will increase linearly with grain

size and will constant after a critical value.

Suggestions :

• So to have a good Young’s modulus and yield strength we should fabricate a material

having both type of grains (small and large both).

• Smaller grains provide restriction to movement of dislocation and yield strength

increases and large grains will provide a good Young’s modulus

Thank You!